Hong Jin Fan

The practical implementation of aqueous zinc‐iodine batteries (ZIBs) is hindered by the rampant Zn dendrites growth, parasite corrosion, and polyiodide shuttling. In this work, ionic liquid EMIM[OAc] is employed as an all‐round solution to mitigate challenges on both the Zn anode and the iodine cathode side. First, the EMIM+ embedded lean‐water inner Helmholtz plane (IHP) and inert solvation sheath modulated by OAc− effectively repels H2O molecules away from the Zn anode surface. The preferential adsorption of EMIM+ on Zn metal facilitates uniform Zn nucleation via a steric hindrance effect. Second, EMIM+ can reduce the polyiodide shuttling by hindering the iodine dissolution and forming an EMIM+‐I3− dominated phase. These effects holistically enhance the cycle life, which is manifested by both Zn || Zn symmetric cells and Zn‐I2 full cells. ZIBs with EAc deliver a capacity decay rate of merely 0.01 ‰ per …

Rechargeable aqueous zinc ion batteries (RAZIBs) have the potential for large scale energy storage due to their environmental friendliness, high safety and low cost. The trade-off between charging/discharging kinetics and stability has been the bottleneck of most cathode materials, which impedes the rate performance and cycle life of RAZIBs. Here we break the trade-off by designing vacancy-rich and Al-doped birnessite-type MnO2 nanosheet (Alx–MnO2) electrodes, which are synthesized by electrochemically oxidizing manganese based layered double hydroxides (MnAl-LDHs). Rich Al cation vacancies formed during the process of electrochemical oxidation provide three-dimensional diffusion channels for the storage of Zn ions, and the remaining Al atoms benefit the structural stability by suppressing the Jahn–Teller distortion of Mn(III)O6 polyhedra during battery cycling. As a result, by employing the optimized …

Zinc‐iodine batteries have the potential to offer high energy‐density aqueous energy storage, but their lifetime is limited by the rampant dendrite growth and the concurrent parasite side reactions on the Zn anode, as well as the shuttling of polyiodides. Herein, a cation‐conduction dominated hydrogel electrolyte is designed to holistically enhance the stability of both zinc anode and iodine cathode. In this hydrogel electrolyte, anions are covalently anchored on hydrogel chains, and the major mobile ions in the electrolyte are restricted to be Zn2+. Specifically, such a cation‐conductive electrolyte results in a high zinc ion transference number (0.81) within the hydrogel and guides epitaxial Zn nucleation. Furthermore, the optimized Zn2+ solvation structure and the reconstructed hydrogen bond networks on hydrogel chains contribute to the reduced desolvation barrier and suppressed corrosion side reactions. On the …

Side reactions on zinc metal (Zn) anodes are formidable issues that cause limited battery life of aqueous zinc‐ion batteries (AZIBs). Here, a facile and controllable layer‐by‐layer (LbL) self‐assembly technique is deployed to construct an ion‐conductive and mechanically robust electrolyte/anode interface for stabilizing the Zn anode. The LbL film consists of two natural and biodegradable bio‐macromolecules, chitosan (CS) and sodium alginate (SA). It is shown that such an LbL film tailors the solvation sheath of Zn ions and facilitates the oriented deposition of Zn. Symmetric cells with the four double layers of CS/SA ((CS/SA)4–Zn) exhibit stable cycles for over 6500 h. The (CS/SA)4–Zn||H2V3O8 coin cell maintains a specific capacity of 125.5 mAh g−1 after 14 000 cycles. The pouch cell with an electrode area of 5 × 7 cm2 also presents a capacity retention of 83% for over 500 cycles at 0.1 A g−1. No obvious dendrites …

Hard carbon (HC) has become the most promising anode material for sodium‐ion batteries (SIBs), but its plateau capacity at ≈0.1 V (Na+/Na) is still much lower than that of graphite (372 mAh g−1) in lithium‐ion batteries (LIBs). Herein, a CO2‐etching strategy is applied to generate abundant closed pores in starch‐derived hard carbon that effectively enhances Na+ plateau storage. During CO2 etching, open pores are first formed on the carbon matrix, which are in situ reorganized to closed pores through high‐temperature carbonization. This CO2‐assisted pore‐regulation strategy increases the diameter and the capacity of closed pores in HC, and simultaneously maintains the microsphere morphology (10–30 µm in diameter). The optimal HC anode exhibits a Na‐storage capacity of 487.6 mAh g−1 with a high initial Coulomb efficiency of 90.56%. A record‐high plateau capacity of 351 mAh g−1 is achieved, owing …

Engineering carbonaceous cathode materials with adequately accessible active sites is crucial for unleashing their charge storage potential. Herein, activated meso‐microporous carbon nanofibers are constructed to enhance the zinc ion storage density by forming a gradient‐pore structure. A dominating pore size of 0.86 nm is tailored to cater for the solvated [Zn(H2O)6]2+. Moreover, these gradient porous nanofibers feature rapid ion/electron dual conduction pathways and offer abundant active surfaces with high affinity to electrolyte. When employed in Zn‐ion capacitors, the electrode delivers significantly enhanced capacity (257 mAh g−1), energy density (200 Wh kg−1 at 78 W kg−1), and cyclic stability (95% retention after 10000 cycles) compared to non‐activated carbon nanofibers electrode. A series of in‐situ characterization techniques unveil that the improved Zn2+ storage capability stems from size …

The large‐scale deployment of aqueous Zn‐ion batteries is hindered by Zn anode instability including surface corrosion, hydrogen gas evolution, and irregular Zn deposition. To tackle these challenges, a polyhydroxylated organic molecular additive, trehalose, is incorporated to refine the solvation structure and promote planar Zn deposition. Within solvation structure regions involving trehalose, the hydroxy groups participate in the reconstruction of hydrogen bond networks, which increases the overpotential for water decomposition reaction. Moreover, at the Zn metal–molecule interface, the chemisorption of trehalose onto the surface of the zinc anode enhances corrosion resistance and facilitates the deposition of zinc in a planar manner. The optimized electrolyte significantly improves Zn striping/plating reversibility and maintains stable potentials over 1600 h at 5 mA cm−2 with a cutoff capacity of 1 mA h cm−2 in …

Organic compounds have the advantages of green sustainability and high designability, but their high solubility leads to poor durability of zinc-organic batteries. Herein, a high-performance quinone-based polymer (H-PNADBQ) material is designed by introducing an intramolecular hydrogen bonding (HB) strategy. The intramolecular HB (C=O⋯N–H) is formed in the reaction of 1,4-benzoquinone and 1,5-naphthalene diamine, which efficiently reduces the H-PNADBQ solubility and enhances its charge transfer in theory. In situ ultraviolet–visible analysis further reveals the insolubility of H-PNADBQ during the electrochemical cycles, enabling high durability at different current densities. Specifically, the H-PNADBQ electrode with high loading (10 mg cm−2) performs a long cycling life at 125 mA g−1 (> 290 cycles). The H-PNADBQ also shows high rate capability (137.1 mAh g−1 at 25 A g−1) due to significantly …

Aqueous zinc‐ion batteries (AZIBs) are gaining popularity for their cost‐effectiveness, safety, and utilization of abundant resources. MXenes, which possess outstanding conductivity, controllable surface chemistry, and structural adaptability, are widely recognized as a highly versatile platform for AZIBs. MXenes offer a unique set of functions for AZIBs, yet their significance has not been systematically recognized and summarized. This review article provides an up‐to‐date overview of MXenes‐based electrode materials for AZIBs, with a focus on the unique functions of MXenes in these materials. The discussion starts with MXenes and their derivatives on the cathode side, where they serve as a 2D conductive substrate, 3D framework, flexible support, and coating layer. MXenes can act as both the active material and a precursor to the active material in the cathode. On the anode side, the functions of MXenes include …

The development of polymer sodium batteries requires cathode materials with stable interfaces to avoid poor interfacial contact and interfacial side reactions during cycling. Here, a co‐engineering strategy is deployed to tailor the cathode internal structure and improve the cathode interface stability through bonding interactions. Internally, the effect of low‐cost Fe substitution in the obtained Na0.67Mn2/3Fe1/3O2 cathode material renders favorable effects in several aspects. First, the increased lattice constant facilitates Na+ intercalation and thereby lowers the diffusion barrier of Na+ ions. Second, it increases the electronic conductivity, thereby improving the reaction reversibility. Third, the MnO bond length is shortened, which alleviates the Jahn‐Taylor effect and improves structural stability. In addition to these internal effects, the FeOB bond interactions due to Fe substitution promote the decomposition of the …

Zn metal is a promising anode material in aqueous batteries, but the direct use of Zn foil encounters severe issues of dendrite formation and side reactions, causing short cycle life. Conventional thick and rigid insulating protection layers may impede Zn ion diffusion and detach during mechanical deformation of the battery. Herein, a dendrite‐free zinc anode is demonstrated by grafting a thin (≈10 nm) Ti3C2Tx MXene functional membrane which is formed via Marangoni‐driven self‐assembly. The thin MXene membrane initiates uniform nucleation and promotes deposition of (002)‐oriented Zn in a lateral growth mode. Meanwhile, the membrane functions as a soft, stress‐adaptive, and protective layer to the underneath active zinc. This functional membrane renders Zn anode with improved cycling stability without notable dendrite formation or side‐reaction products. Flexible Zn─I2 pouch cells fabricated from the …

The decoupled battery design is promising for breaking the energy density limit of traditional aqueous batteries. However, the complex battery configuration and low‐selective separator membranes restrict their energy output and service time. Herein, a zinc–sulfur decoupled aqueous battery is achieved by designing a high‐mass loading sulfur electrode and single ion‐selective membrane (ISM). A vertically assembled nanosheet network constructed with the assistance of a magnetic field enables facile electron and ion conduction in thick sulfur electrodes, which is conducive to boosting the cell‐level energy output. For the tailored ISM, the Na ions anchored on its skeleton effectively prevent the crossover of OH− or Cu2+, facilitating the transport of Na+ and ensuring structural and mechanical stability. Consequently, the Zn–S aqueous battery achieves a reversible energy density of 3988 Wh kgs−1 (by sulfur mass …

All-inorganic cesium lead bromide (CsPbBr3) quantum dots (QDs) with high photoluminescence (PL) quantum efficiency have been reported as ideal gain materials for high-performance lasers. Nevertheless, isolated CsPbBr3 QDs have not achieved lasing emission (LE) due to finite absorption cross-section. Here, we demonstrate continuous-wave lasing of isolated CsPbBr3 QDs embedded in a microcavity. Distributed Bragg reflectors (DBRs), together with isolated CsPbBr3 QDs in a polymer matrix, are introduced to construct a vertical-cavity surface-emitting laser (VCSEL), which exhibits stable single-mode lasing emissions with an ultra-low threshold of 8.8 W cm−2 and a high Q factor of 1787. Such perovskite-based microcavity structures sustain highly stable excitons at room temperature and can provide an excellent experimental platform to further study the single-particle nano-lasers and quantum physics …

Single-atom catalysts (SACs) with high atom utilization and outstanding catalytic selectivity are useful for improving battery performance. Herein, atomically dispersed Ni–N4 and Fe–N4 dual sites coanchored on porous hollow carbon nanocages (Ni–Fe–NC) are fabricated and deployed as the sulfur host for Li–S battery. The hollow and conductive carbon matrix promotes electron transfer and also accommodates volume fluctuation during cycling. Notably, the high d band center of Fe in Fe–N4 site demonstrates strong polysulfide affinity, leading to an accelerated sulfur reduction reaction. Meanwhile, Li2S on the Ni–N4 site delivers a metallic property with high S 2p electron density of states around the Femi energy level, enabling a low sulfur evolution reaction barrier. The dual catalytic effect on Ni–Fe–NC endows sulfur cathode high energy density, prolonged lifespan, and low polarization.

Rechargeable aqueous Zn‐I2 batteries (ZIB) are regarded as a promising energy storage candidate. However, soluble polyiodide shuttling and rampant Zn dendrite growth hamper its commercial implementation. Herein, a hetero‐polyionic hydrogel is designed as the electrolyte for ZIBs. On the cathode side, iodophilic polycationic hydrogel (PCH) effectively alleviates the shuttle effect and facilitates the redox kinetics of iodine species. Meanwhile, polyanionic hydrogel (PAH) toward Zn metal anode uniformizes Zn2+ flux and prevents surface corrosion by electrostatic repulsion of polyiodides. Consequently, the Zn symmetric cells with PAH electrolyte demonstrate remarkable cycling stability over 3000 h at 1 mA cm–2 (1 mAh cm–2) and 800 h at 10 mA cm–2 (5 mAh cm–2). Moreover, the Zn‐I2 full cells with PAH‐PCH hetero‐polyionic hydrogel electrolyte deliver a low‐capacity decay of 0.008 ‰ per cycle during 18 …

In the literature, Zn–Mn aqueous batteries (ZMABs) confront abnormal capacity behavior, such as capacity fluctuation and diverse “unprecedented performances.” Because of the electrolyte additive‐induced complexes, various charge/discharge behaviors associated with different mechanisms are being reported. However, the current performance assessment remains unregulated, and only the electrode or the electrolyte is considered. The lack of a comprehensive and impartial performance evaluation protocol for ZMABs hinders forward research and commercialization. Here, a pH clue (proton‐coupled reaction) to understand different mechanisms is proposed and the capacity contribution is normalized. Then, a series of performance metrics, including rated capacity (Cr) and electrolyte contribution ratio from Mn2+ (CfM), are systematically discussed based on diverse energy storage mechanisms. The relationship …

Unstable cathode‐electrolyte and/or anode‐electrolyte interface in polymer‐based sodium‐ion batteries (SIBs) will deteriorate their cycle performance. Herein, a unique solvated double‐layer quasi‐solid polymer electrolyte (SDL‐QSPE) with high Na+ ion conductivity is designed to simultaneously improve stability on both cathode and anode sides. Different functional fillers are solvated with plasticizers to improve Na+ conductivity and thermal stability. The SDL‐QSPE is laminated by cathode‐ and anode‐facing polymer electrolyte to meet the independent interfacial requirements of the two electrodes. The interfacial evolution is elucidated by theoretical calculations and 3D X‐ray microtomography analysis. The Na0.67Mn2/3Ni1/3O2|SDL‐QSPE|Na batteries exhibit 80.4 mAh g−1 after 400 cycles at 1 C with the Coulombic efficiency close to 100 %, which significantly outperforms those batteries using the …

Organic cathodes for aqueous zinc‐ion batteries (AZIBs) feature intrinsic flexibility and favorable kinetics, but they suffer from high solubility. Herein, a partial charge regulation strategy is deployed by designing a small organic molecule with extended π‐conjugated plane, namely benzo[i]benzo[6′,7′]quinoxalino[2′,3′:9,10]phenanthro[4,5‐abc]phenazine‐5,10,16,21‐tetraone (PTONQ). The charge equalization of active sites induced by the extended π‐conjugated plane of the PTONQ molecule combined with high aromaticity renders the molecule low solubility, fast charge transfer, and high structural stability. The fabricated Zn//PTONQ battery cycles more than 500 h at 175 mA g−1 with small capacity reduction, fast charged/discharged kinetics, and anti‐freeze performance (below ‐20°C). By a series of ex situ characterizations, it is attested that the capacity originates mainly from Zn2+ insertion/removal of …

The progress of aqueous zinc batteries (AZBs) is limited by the poor cycling life due to Zn anode instability, including dendrite growth, surface corrosion, and passivation. Inspired by the anti‐corrosion strategy of steel industry, a compounding corrosion inhibitor (CCI) is employed as the electrolyte additive for Zn metal anode protection. It is shown that CCI can spontaneously generate a uniform and ≈30 nm thick solid‐electrolyte interphase (SEI) layer on Zn anode with a strong adhesion via ZnO bonding. This SEI layer efficiently prohibits water corrosion and guides homogeneous Zn deposition without obvious dendrite formation. This enables reversible Zn deposition and dissolution for over 1100 h under the condition of 1 mA cm−2 and 1 mAh cm−2 in symmetric cells. The Zn‐MnO2 full cells with CCI‐modified electrolyte deliver an ultralow capacity decay rate (0.013% per cycle) at 0.5 A g−1 over 1000 cycles …

The commercial implementation of aqueous Zn-ion batteries is being impeded by the rampant dendrite growth and exacerbated side reactions on the Zn metal anodes. Herein, a 60 nm artificial protective layer with spatial dielectric–metallic gradient composition (denoted as GZH) is developed via Zn and HfO2 cosputtering. In this design, the top HfO2 layer with high permittivity and low electronic conductivity effectively suppresses hydrogen evolution. The intermediate Zn-rich oxide region promotes the dendrite-free Zn deposition and reinforces the contact between Zn and the sputtered layer. This design allows stable battery operation at high currents. Symmetric cells with Zn-GZH exhibit stable voltage separation over 500 h at 10 mA cm–2 with a cutoff capacity of 5 mAh cm–2. When paired with a vanadate cathode, the full-cell battery delivers a capacity retention of around 75% after 2000 cycles. This design concept …

Formic acid is considered one of the most economically viable products for electrocatalytic CO2 reduction reaction (CO2RR). However, developing highly active and selective electrocatalysts for effective CO2 conversion remains a grand challenge. Herein, we report that structural modulation of the bismuth oxide nanosheet via Zn2+ cooperation has a profound positive effect on exposure of the active plane, thereby contributing to high electrocatalytic CO2RR performance. The obtained Zn-Bi2O3 catalyst demonstrates superior selectivity towards formate generation in a wide potential range; a high Faradaic efficiency of 95% and a desirable partial current density of around 20 mA·cm−2 are obtained at −0.9 V (vs. reversible hydrogen electrode (RHE)). As proposed by density functional theory calculations, Zn substitution is the most energetically feasible for forming and stabilizing the key OCHO* intermediate among …

Promoting the electron occupancy of active sites to unity is an effective method to enhance the oxygen evolution reaction (OER) performance of spinel oxides, but it remains a great challenge. Here, an in situ approach is developed to modify the valence state of octahedral Ni cations in NiFe2O4 inverse spinel via surface sulfates (SO42–). Different from previous studies, SO42– is directly anchored on the spinel surface instead of forming from uncontrolled conversion or surface reconstruction. Experiment and theoretical calculations reveal the precise adsorption sites and spatial arrangement for SO42– species. As a main promoting factor, surface SO42– effectively converts the crystal field stable Ni state (t2g6eg2) to the near-unity eg electron state (t2g6eg1). Moreover, the inevitable oxygen vacancies (Vo) further optimize the energy barrier of the potential-determining step (from OH* to O*). This co-modification …

The main role of inert fillers in polymer electrolytes is to enhance ionic conductivity. However, lithium ions in gel polymer electrolytes (GPEs) conduct in liquid solvent rather than along the polymer chains. So far, the main role of inert fillers in improving the electrochemical performance of GPEs is still unclear. Here, various low-cost and common inert fillers (Al2O3, SiO2, TiO2, ZrO2) are introduced into GPEs to study their effects on Li-ion polymer batteries. It is found that the addition of inert fillers has different effects on ionic conductivity, mechanical strength, thermal stability, and, dominantly, interfacial properties. Compared with other gel electrolytes containing SiO2, TiO2, or ZrO2 fillers, those with Al2O3 fillers exhibit the most favorable performance. The high performance is ascribed to the interaction between the surface functional groups of Al2O3 and LiNi0.8Co0.1Mn0.1O2, which alleviates the decomposition of the …

Breakthroughs in super-concentrated electrolytes have pushed the aqueous solution to the forefront of the high-safety battery devices. An ideal electrolyte system should be cost-effective and stable in a wide electrochemical window. In recent years, eutectic mixtures have emerged as a green, safe, low-cost, and electrochemically stable electrolyte system for rechargeable metal-ion batteries (MIBs). Here, the fundamental understanding of the formation mechanisms, physio-chemical properties, and composition–structure–property relationships of eutectic mixtures are summarized. Our focus is their advanced function and applications in MIBs. Considering that eutectic mixtures in MIBs are still at an early stage, we provide the challenges and perspectives which hopefully may guide the rational design of advanced eutectic mixtures for different electrochemical energy storage and conversion systems.

We have achieved the synthesis of dual-metal single atoms and atomic clusters that co-anchor on a highly graphitic carbon support. The catalyst comprises Ni4 (and Fe4) nanoclusters located adjacent to the corresponding NiN4 (and FeN4) single-atom sites, which is verified by systematic X-ray absorption characterization and density functional theory calculations. A distinct cooperation between Fe4 (Ni4) nanoclusters and the corresponding FeN4 (NiN4) atomic sites optimizes the adsorption energy of reaction intermediates and reduces the energy barrier of the potential-determining steps. This catalyst exhibits enhanced oxygen reduction and evolution activity and long-cycle stability compared to counterparts without nanoclusters and commercial Pt/C. The fabricated Zn–air batteries deliver a high power density and long-term cyclability, demonstrating their prospects in energy storage device applications.

Zn–Mn aqueous batteries (ZMABs) present potential for grid-scale energy storage with the benefits of low cost, high safety and eco-friendliness [1]. Since 1866 (Leclanché wet cell), we have witnessed the prosperity of ZMABs in the primary battery market and an increasing interest in rechargeable ZMABs. In the last 5 years, achievements have been made in high-capacity MnO2 cathodes, dendrite-free Zn metal anodes and functionalized electrolytes [2–4], which push rechargeable ZMABs a step closer to practical applications. In particular, electrolyte regulation has been regarded as most important in stabilizing the interface but it remains challenging. Recently, writing in National Science Review, Liang, Fang and co-workers reported a leanwater quasi-eutectic electrolyte (QEE) that has been shown to be beneficial in facilitatingthereversibleinterfacialdeposition and reaction kinetic of Mn-based cathodes in a long …

The growing trend of intelligent devices ranging from wearables and soft robots to artificial intelligence has set a high demand for smart batteries. Hydrogels provide opportunities for smart batteries to self-adjust their functions according to the operation conditions. Despite the progress in hydrogel-based smart batteries, a gap remains between the designable functions of diverse hydrogels and the expected performance of batteries. In this Perspective, we first briefly introduce the fundamentals of hydrogels, including formation, structure, and characteristics of the internal water and ions. Batteries that operate under unusual mechanical and temperature conditions enabled by hydrogels are highlighted. Challenges and opportunities for further development of hydrogels are outlined to propose future research in smart batteries toward all-climate power sources and intelligent wearables.

The diffusion-limited aggregation (DLA) of metal ion (Mn+) during the repeated solid-to-liquid (StoL) plating and liquid-to-solid (LtoS) stripping processes intensifies fatal dendrite growth of the metallic anodes. Here, we report a new solid-to-solid (StoS) conversion electrochemistry to inhibit dendrites and improve the utilization ratio of metals. In this StoS strategy, reversible conversion reactions between sparingly soluble carbonates (Zn or Cu) and their corresponding metals have been identified at the electrode/electrolyte interface. Molecular dynamics simulations confirm the superiority of the StoS process with accelerated anion transport, which eliminates the DLA and dendrites in the conventional LtoS/StoL processes. As proof of concept, 2ZnCO3·3Zn(OH)2 exhibits a high zinc utilization of ca. 95.7% in the asymmetry cell and 91.3% in a 2ZnCO3·3Zn(OH)2 || Ni-based full cell with 80% capacity retention over 2000 …

The emergence of on-skin electronics with functions in human–machine interfaces and on-body sensing calls for the development of smart flexible batteries with high performance. Electrochromic energy-storage devices provide a visual indication of the capacity through a real-time change in color without any additional power supply. In this study, dual-function battery and supercapacitor devices for skin-interfaced wearable electronics are developed by a simple and scalable transfer printing method, featuring a thickness of less than 50 μm. Supercapacitive and battery-type devices with areal capacities of 113.4 mF cm–2 and 6.1 μAh cm–2, respectively, are achieved by assembling electrochromic cathodes, hydrogel film electrolyte, and zinc anode. The high flexibility of the ultrathin energy devices endows them with good conformity on arbitrarily shaped surfaces, including elastic human skin, further enhancing the …

In recent years, the increasing demand for high‐capacity and safe energy storage has focused attention on zinc batteries featuring high voltage, high capacity, or both. Despite extensive research progress, achieving high‐energy‐density zinc batteries remains challenging and requires the synergistic regulation of multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies of high‐energy‐density zinc batteries and critically analyze the positive effects and potential issues of these strategies in optimizing the electrochemistry, cathode materials, electrolytes, and device architecture. Finally, the challenges and perspectives for the further development of high‐energy‐density zinc batteries are outlined to guide research towards new‐generation batteries for household appliances, low‐speed electric vehicles, and large‐scale …

While aqueous Zn-Na hybrid batteries have garnered widespread attention because of their low cost and high safety, it is still challenging to achieve long cycle-life and stable discharge-voltage due to sluggish reaction kinetics, zinc dendrite formation, and side reactions. Herein, we design a Zn2+/Na+ dual-salt battery, in which sodiation of the NVP cathode favors zinc intercalation under an energy threshold, leading to decoupled redox reactions on the cathode and anode. Systematic investigations of the electrolyte effects show that the ion intercalation mechanism and the kinetics in the mixture of triflate- and acetate-based electrolytes are superior to those in the common acetate-only electrolytes. As a result, we have achieved fast discharging capability, suppressed zinc dendrites, a stable discharge voltage at 1.45 V with small polarization, and nearly 100% Columbic efficiency in the dual-salt mixture …

Poor stability of nanostructured electrocatalysts at rigorous industrial conditions significantly inhibits their performances in practical electrolyzers. Although many substrate‐supported nanostructured electrocatalysts present attractive performance at small currents, they cannot sustain industry‐level high current densities for long‐term operation. Herein, by chemically organizing nanoscale electrocatalysts into a macroscopic substrate‐free metallic alloy aerogel, this NiFe‐based nano‐catalyst achieves 1000‐h durability at industrial‐level current densities, with exceptionally high activities of 500 mA at the overpotential of only 281 mV. This NiFe alloy aerogel is constructed by a magnetic‐field assisted growth and assembly of ferromagnetic NiFe nanoparticles, in which nanowires are loosely crosslinked by metallic joints. This alloy aerogel shows a high electric conductivity of 500 S m−1, structural stability for more than …

The poor stability of the zinc‐metal anode is a main bottleneck for practical application of aqueous zinc‐ion batteries. Herein, a series of molecular sieves with various channel sizes are investigated as an electrolyte host to regulate the ionic environment of Zn2+ on the surface of the zinc anode and to realize separator‐free batteries. Based on the ZSM‐5 molecular sieve, a solid–liquid mixed electrolyte membrane is constructed to uniformize the transport of zinc ions and foster dendrite‐free Zn deposition. Side reactions can also be suppressed through tailoring the solvation sheath and restraining the activity of water molecules in electrolyte. A V2O5||ZSM‐5||Zn full cell shows significantly enhanced performance compared to cells using glass fiber separator. Specifically, it exhibits a high specific capacity of 300 mAh g−1, and a capacity retention of 98.67% after 1000 cycles and 82.67% after 3000 cycles at 1 A g−1. It …

Na‐ion battery has the potential to be one of the best types of next‐generation energy storage devices by virtue of their cost and sustainability advantages. With the demand for high safety, the replacement of traditional organic electrolytes with polymer electrolytes can avoid electrolyte leakage and thermal instability. Polymer electrolytes, however, suffer from low ionic conductivity and large interfacial impedance. Gel polymer electrolytes (GPEs) represent an excellent balance that combines the advantages of high ionic conductivity, low interfacial impedance, high thermal stability, and flexibility. This short review summarizes the recent progress on gel polymer Na‐ion batteries, focusing on different preparation approaches and the resultant physical and electrochemical properties. Reasons for the differences in ionic conductivity, mechanical properties, interfacial properties, and thermal stability are discussed at the …

Because of their high energy density, safety, eco-friendliness, and sustainability, aqueous rechargeable zinc batteries (ARZBs) have attracted burgeoning interests. Manganese oxide cathodes are particularly attractive because they are obtained from earth-abundant and non-toxic materials. However, the diversity of mechanisms that explain the electrochemistry with Zn metal anodes in mildly acidic media hinders ARZBs' further development. In brief, a specific manganese oxide polymorph, typically MnO2, in mildly acidic electrolytes has been reported to exhibit different reaction mechanisms under similar electrochemical conditions. Moreover, the recently discussed dissolution/deposition process of MnO2 in both strong and mildly acidic electrolyte media has revolutionized the conventional intercalation chemistry. To this end, this perspective aims to clarify and seek possible convergence of the conflicting …

A highly densified electrode material is desirable to achieve large volumetric capacity. However, pores acting as ion transport channels are critical for high utilization of active material. Achieving a balance between high volume density and pore utilization remains a challenge particularly for hollow materials. Herein, capillary force is employed to convert hollow fibers to a bamboo-weaving-like flexible electrode (BWFE), in which the shrinkage of hollow space results in high compactness of the electrode. The volume of the electrode can be decreased by 96% without sacrificing the gravimetric capacity. Importantly, the conductivity of BWFE after thermal treatment can reach up to 50,500 S/m which exceeds that for most other carbon materials. Detailed mechanical analysis reveals that, due to the strong interaction between nanoribbons, Young’s modulus of the electrode increases by 105 times. After SnO2 active …

The practical application of the Zn‐metal anode for aqueous batteries is greatly restricted by catastrophic dendrite growth, intricate hydrogen evolution, and parasitic surface passivation. Herein, a polyanionic hydrogel film is introduced as a protective layer on the Zn anode with the assistance of a silane coupling agent (denoted as Zn–SHn). The hydrogel framework with zincophilic –SO3− functional groups uniformizes the zinc ions flux and transport. Furthermore, such a hydrogel layer chemically bonded on the Zn surface possesses an anti‐catalysis effect, which effectively suppresses both the hydrogen evolution reaction and formation of Zn dendrites. As a result, stable and reversible Zn stripping/plating at various currents and capacities is achieved. A full cell by pairing the Zn–SHn anode with a NaV3O8·1.5 H2O cathode shows a capacity of around 176 mAh g−1 with a retention around 67% over 4000 cycles at …

Potassium (K)‐based layered oxides are potential candidates for K‐ion storage but they suffer from chemical instability under ambient conditions that deteriorate their performance in rate‐capability and cycle life. To tackle this issue, a facile hydration strategy is employed, in which H2O molecules are introduced into the K ion layers of P3‐type K0.4Fe0.1Mn0.8Ti0.1O2, which induces a phase transition from the hexagonal to monoclinic symmetry accompanied by layer spacing expansion. The hydrated K0.4Fe0.1Mn0.8Ti0.1O2 ⋅ 0.16H2O has a strong tolerance to air and can be stored in lab air ambient for 60 days without a change in crystal structure or chemical composition. The K0.4Fe0.1Mn0.8Ti0.1O2 ⋅ 0.16H2O electrode shows improved K+ mobility and less volume change during potassiation/de‐potassiation. Owing to these merits, K0.4Fe0.1Mn0.8Ti0.1O2 ⋅ 0.16H2O as the cathodes for both organic …

Aqueous Zn-MnO2 batteries with Mn2+/MnO2 conversion reaction have attracted enormous attentions in these years, in which the proposal of acetate-based electrolyte further boosts the redox chemistry and achieves the two-electron reaction with mitigated anode corrosion. However, the lower redox potential, the generation of dead MnO2, and MnO2 suspension in acetate-based Zn-MnO2 batteries inhibit their commercialization. Herein, the acetate-based electrolyte is optimized by introducing electrolyte modification and manageable Cr2+/Cr3+ reaction, contributing to higher cathodic potential and longer lifetime. Additionally, the dead MnO2 with incompact morphology is found to facilitate the further deposition in the initial stage. Based on the above discussions, we proposed the all-round optimizations, which additionally include a pre-cycling process and a simple ultrasonic treatment, achieving a triple lifetime …

Work function strongly impacts the surficial charge distribution, especially for metal‐support electrocatalysts when a built‐in electric field (BEF) is constructed. Therefore, studying the correlation between work function and BEF is crucial for understanding the intrinsic reaction mechanism. Herein, we present a Pt@CoOx electrocatalyst with a large work function difference (ΔΦ) and strong BEF, which shows outstanding hydrogen evolution activity in a neutral medium with a 4.5‐fold mass activity higher than 20 % Pt/C. Both experimental and theoretical results confirm the interfacial charge redistribution induced by the strong BEF, thus subtly optimizing hydrogen and hydroxide adsorption energy. This work not only provides fresh insights into the neutral hydrogen evolution mechanism but also proposes new design principles toward efficient electrocatalysts for hydrogen production in a neutral medium.

Developing advanced bifunctional water splitting electrodes that can perform both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is critically important for sustainable hydrogen production because of the simplicity in implementing the system where only one type of electrode material is required. However, the cell voltage of currently available electrolyzers using bifunctional electrodes is still high because maintaining high intrinsic OER and HER activity simultaneously while keeping good charge and mass transport is a challenging task. Herein, the dense ternary NiMoFe alloy nanoparticles are in situ precipitated on the highly conductive hierarchical MoO2 nano-pillar arrays (NiMoFe NPs@MoO2 NPAs) to form an ultra-hydrophilic and super-aerophobic structure by the reductive annealing process-induced phase separation method. Benefiting from the intrinsically high OER and HER activity …

Strain in layered transition‐metal dichalcogenides (TMDs) is a type of effective approach to enhance the catalytic performance by activating their inert basal plane. However, compared with traditional uniaxial strain, the influence of biaxial strain and the TMD layer number on the local electronic configuration remains unexplored. Herein, via a new in situ self‐vulcanization strategy, biaxially strained MoS2 nanoshells in the form of a single‐crystalline Ni3S2@MoS2 core–shell heterostructure are realized, where the MoS2 layer is precisely controlled between the 1 and 5 layers. In particular, an electrode with the bilayer MoS2 nanoshells shows a remarkable hydrogen evolution reaction activity with a small overpotential of 78.1 mV at 10 mA cm‐2, and negligible activity degradation after durability testing. Density functional theory calculations reveal the contribution of the optimized biaxial strain together with the induced …

Aqueous zinc ion battery is a promising technology for safe and low-cost energy storage. However, zinc batteries using metallic Zn anode suffer from poor cycle life due to Zn dendrites growth, side reactions and parasitic byproducts. To tackle these issues, we design a potent Zn anode host by combining two strategies, a 3D microporous scaffold and zincophilic surfaces. This design proves advantageous in stabilizing Zn metal deposition and improving the cycle life of full cells. Specifically, a Sn nanodots coated porous carbon fiber (Sn-PCF) network has been carefully designed. The PCF network is conducive in promoting homogeneous Zn2+ flux and uniform 3D Zn nucleation, leading to dense and flat Zn deposition even under a high capacity of 10 mAh cm−2. Meanwhile, experiments and calculation reveal that, the Sn nanodots coating induces a strongly zincophilic surface of each fiber with high Zn2+ adsorption …

由太阳能, 风能和海洋等可再生能源驱动的工业级水分解产氢为能源和环境的可持续性发展开辟了一条极具潜力的道路. 然而, 在工业上最先进电解技术使用高纯水作为氢源, 这将带来严重的淡水资源危机. 海水分解为饮用水短缺提供了一条切实可行的解决途径, 但仍面临规模工业化生产的巨大挑战. 在这里, 我们总结了海水分解的最新进展, 包括反应机制, 电极设计标准和直接海水分解的工业电解槽. 深入讨论了应对海水电解中的关键挑战, 如活性位点, 反应选择性, 耐腐蚀性和传质能力等的解决方案. 此外, 该文章重点总结了海水电解设备的最新发展, 并提出了设计长寿命直接海水电解装置的有效策略. 最后, 我们对直接海水电解的未来机遇和挑战提出了自己的观点.

A dynamic surface reconstruction of oxide electrocatalysts in alkaline media is widely observed especially for layered double hydroxide (LDH), but little is known about how to promote the reconstruction toward desired surfaces for improved oxygen evolution reaction (OER). Here, surface reconstruction of NiFe LDH nanosheets is successfully induced to a higher degree via in situ sulfur doping than that by natural electrochemical activation. Theoretical calculations, operando Raman, and various ex situ characterizations reveal the S anion‐induced effect can lower the energy barrier and facilitate the phase transformation into highly active S‐doped oxyhydroxides. The generated S‐NixFeyOOH can optimize the intermediate adsorption and facilitate the OER kinetics. The reconstructed S‐oxyhydroxides catalyst presents superior OER activity and long‐term durability compared to undoped ones. This work provides a …

Amorphization is an efficient strategy to activate intrinsically inert catalysts. However, the low crystallinity of amorphous catalysts often causes high solubility and poor electrochemical stability in aqueous solution. Here, a different mechanism is developed to simultaneously stabilize and activate the water‐soluble amorphous MoSxOy via a charge‐balancing strategy, which is induced by different electronegativity between the co‐dopants Rh (2.28) and Sn (1.96). The electron‐rich Sn prefers to stabilize the unstable apical O sites in MoSxOy through charge transfer, which can prevent the H from attacking. Meanwhile, the Rh, as the charge regulator, shifts the main active sites on the basal plane from inert Sn to active apical Rh sites. As a result, the amorphous RhSn‐MoSxOy exhibits drastic enhancement in electrochemical stability (η10 increases only by 12 mV) after 1000 cycles and a distinct activity (η10: 26 mV and …

Despite the substantial progress in cathode materials in the past few years, rechargeable zinc batteries (RZBs) are plagued by rapid performance degradation due to dendrite formation and notorious side reactions at the Zn anode side. Here, an optimized hydrated eutectic electrolyte (HEE) system containing methylsulfonylmethane, zinc perchlorate, and water, in which an organic ligand coordinated the solvation shell of Zn ions with water molecules constituting the eutectic network, is proposed. Compared to common aqueous solutions, this HEE system is proven effective in promoting the smooth Zn deposition and plating/stripping reversibility as well as suppressing side reactions. The vanadium‐based zinc batteries based on this new HEE exhibit exceptionally high‐capacity retention (≈100% retention even after 1600 cycles at a relatively small current density of 1000 mA g−1). This study offers a new type of …

Paper electronics offer an environmentally sustainable option for flexible and wearable systems and perfectly fit the available printing technologies for high manufacturing efficiency. As the heart of energy‐consuming devices, paper‐based batteries are required to be compatible with printing processes with high fidelity. Herein, hydrogel reinforced cellulose paper (HCP) is designed to serve as the separator and solid electrolyte for paper batteries. The HCP can sustain higher strain than pristine papers and are biodegradable in natural environment within four weeks. Zinc‐metal (Ni and Mn) batteries printed on the HCP present remarkable volumetric energy density of ≈26 mWh cm–3, and also demonstrate the feature of cuttability and compatibility with flexible circuits and devices. As a result, self‐powered electronic system could be constructed by integrating printed paper batteries with solar cells and light‐emitting …

Piezoelectric materials convert mechanical stress to electrical energy and thus are widely used in energy harvesting and wearable devices. However, in the piezoelectric family, there are two pairs of properties that improving one of them will generally compromises the other, which limits their applications. The first pair is piezoelectric strain and voltage constant, and the second is piezoelectric performance and mechanical softness. Here, we report a molecular bond weakening strategy to mitigate these issues in organic-inorganic hybrid piezoelectrics. By introduction of large-size halide elements, the metal-halide bonds can be effectively weakened, leading to a softening effect on bond strength and reduction in polarization switching barrier. The obtained solid solution C6H5N(CH3)3CdBr2Cl0.75I0.25 exhibits excellent piezoelectric constants (d33 = 367 pm/V, g33 = 3595 × 10−3 Vm/N), energy harvesting …

Industrial hydrogen generation through water splitting, powered by renewable energy such as solar, wind and marine, paves a potential way for energy and environment sustainability. However, state-of-the-art electrolysis using high purity water as hydrogen source at an industrial level would bring about crisis of freshwater resource. Seawater splitting provides a practical path to solve potable water shortage, but still faces great challenges for large-scale industrial operation. Here we summarize recent developments in seawater splitting, covering general mechanisms, design criteria for electrodes, and industrial electrolyzer for direct seawater splitting. Multi-objective optimization methods to address the key challenges of active sites, reaction selectivity, corrosion resistance, and mass transfer ability will be discussed. The recent development in seawater electrolyzer and acquaint efficient strategies to design direct devices for long-time operation are also highlighted. Finally, we provide our own perspective to future opportunities and challenges towards direct seawater electrolysis. 由太阳能, 风能和海洋等可再生能源驱动的工业级水分解产氢为能源和环境的可持续性发展开辟了一条极具潜力的道路.然而, 在工业上最先进电解技术使用高纯水作为氢源, 这将带来严重的淡水资源危机.海水分解为饮用水短缺提供了一条切实可行的解决途径, 但仍面临规模工业化生产的巨大挑战.在这里,我们总结了海水分解的最新进展,包括反应机制, 电极设计标准和直接海水分解的工业电解槽. 深入讨论了应对海水电解中的关键挑战, 如活性位点, 反应选择性, 耐腐蚀性和传质能力等的解决方案. 此外, 该文章重点总结了海水电解设备的最新发展, 并提出了设计长寿命直接海水电解装置的有效 …

To enhance the energy density of batteries and explore intrinsic charge storage mechanism of the active materials, it is important to reduce or eliminate the use of non‐active materials in electrodes, such as binder and conductive additives. Herein, free‐standing Na4MnV(PO4)3@C (F‐NMVP@C) fiber membrane is fabricated and directly used as a sodium‐ion battery (SIB) cathode. In situ X‐ray diffraction reveals that the V3+/V4+ redox reaction occurs through a solid‐solution reaction while a two‐phase Mn2+/Mn3+ redox reaction is identified, and both are highly reversible. Meanwhile, ex situ electrochemical impedance spectroscopy reveals that both the ion diffusion coefficient and charge transfer resistance of F‐NMVP@C change reversibly during the Na+ intercalation/de‐intercalation. Battery full cells are assembled based on the free‐standing F‐NMVP@C cathodes and F‐Sb@C anodes, which manifests a …

The direct synthesis of hydrogen peroxide (H2O2) through the two‐electron oxygen reduction reaction is a promising alternative to the industrial anthraquinone oxidation process. Selectivity to H2O2 is however limited by the four‐electron pathway during oxygen reduction. Herein, it is reported that aminoanthraquinone confined isolated metal sites on carbon supports selectively steer oxygen reduction to H2O2 through the two‐electron pathway. Confining isolated NiNx sites under aminoanthraquinone increases the selectivity to H2O2 from below 55% to above 80% over a wide potential range. Spectroscopy characterization and density functional theory calculations indicate that isolated NiNx sites are confined within a nanochannel formed between the molecule and the carbon support. The confinement reduces the thermodynamic barrier for OOH* desorption versus further dissociation, thus increasing the …

The response speed of the reported Cs2AgBiBr6-based photodetectors exhibits a wide variation ranging from microseconds to nanoseconds, while the reason is still unclear. Apart from the conventional approaches such as reducing effective area, new regulating approaches for response speed improvement have rarely been reported. On the other hand, it is generally believed that ultraviolet (UV) light has negative impact on perovskite devices resulting in performance degradation. In this work, we demonstrated that the response speed of the photodetector with FTO/Cs2AgBiBr6/Au structure can be effectively regulated by utilizing UV light-soaking effect without reducing the device area. Particularly, the decay time is efficiently modulated from 30.1 µs to 340 ns. In addition, the −3 dB bandwidth of the device is extended from 5 to 20 kHz. It is worth mentioning that the light current is remarkably boosted by 15 times …

Aqueous Zn-ion battery (AZIB) has become an attractive technology because of its unique features of low cost, high safety and the eco-friendliness. MnO2 is the model cathode material for AZIB since the first report on reversible Zn-MnO2 battery, but recent studies have unveiled different charge storage mechanisms. Due to revamping of the electrochemistry and redesigning of the electrolyte and interface, there is tremendous performance enhancement in AZIB. This mini Review will first give a brief introduction of ZIB, including fundamentals of materials and components, and the progress in recent years. Then, a general classification of working mechanisms related to MnO2 in neutral and mildly acidic electrolyte is elaborated. Our focus is put on the recent blossoming Zn-MnO2 electrolytic mechanism, which has given birth to the Zn-MnO2 redox flow batteries that are highly promising for large-scale static energy …

Passive building cooling without any electricity input are highly desirable in pursuing low energy consumption and environment protection. However, widespread adoption of existing techniques is restrained by the complex system design or low cooling power. Herein, we propose an efficient passive cooling approach with a bilayer porous polymer film, which comprises a hygroscopic hydrogel and a hydrophobic top layer with hierarchical pores. The hydrogel implements evaporative cooling in the daytime and regenerates itself at night. The top layer protects and radiatively cools the hydrogel, which enhances the cooling power during day and helps the hydrogel regeneration at night. With the synergistic effect, the bilayer film attains a remarkable sub-ambient temperature drops of ~7 °C and an effective cooling power of ~150 W·m−2 under direct sunlight, showing great potential for low-cost, efficient and scalable …

Hyperspectral imaging (HSI) with rich spectral and spatial information holds potential for applications ranging from remote sensing to biomedicine. However, charge-coupled device (CCD) detectors used in conventional HSI systems suffer from inferior and unbalanced responsivity in the visible region, which is not a perfect choice for high-performance visible HSI. That is, conventional Si-based CCDs exhibit poor responsivity at short wavelengths (e.g., 400–600 nm) compared with that at longer wavelengths due to the nature of the indirect bandgap in silicon of around 1.1 eV. To solve this challenge, we introduce a CsPbBr_3 perovskite layer to shape the spectrum of a Si/PEDOT:PSS heterojunction photodetector (PD), resulting in a fabricated Si-CsPbBr_3 hybrid PD with enhanced responsivity at 400–600 nm. This results in an approximately flat spectral responsivity curve in the visible region (400–800 nm …

Polynary transition‐metal atom catalysts are promising to supersede platinum (Pt)‐based catalysts for oxygen reduction reaction (ORR). Regulating the local configuration of atomic catalysts is the key to catalyst performance enhancement. Different from the previously reported single‐atom or dual‐atom configurations, a new type of ternary‐atom catalyst, which consists of atomically dispersed, nitrogen‐coordinated Co–Co dimers, and Fe single sites (i.e., Co2–N6 and Fe–N4 structures) that are coanchored on highly graphitized carbon supports is developed. This unique atomic ORR catalyst outperforms the catalysts with only Co2–N6 or Fe–N4 sites in both alkaline and acid conditions. Density functional theory calculations clearly unravels the synergistic effect of the Co2–N6 and Fe–N4 sites, which can induce higher filling degree of Fe–d orbitals and favors the binding capability to *OH intermediates (the rate …

The void introduction for high-energy alloying-type electrode has suffered a dilemma between insufficient void leading to structural collapse and excessive void causing low volumetrical utilization ratio. Herein, a novel tunable void structure of SnO2-void-hierarchically vertical graphene (SnO2□hVG) nanoarray has been designed via facile C-plasma technique, which facilitates simultaneous encapsulation of protective vertical graphene and moderate void formation. Benefiting from the tunable void and interconnected highly conductive graphene shells and backbones, our all-in-one framework delivers excellent structural integrity and superior Li+ storage capabilities due to the precise volume buffering without collapse of structure and extravagant void. As a result, an imposing capacity of 650 mA h g−1 at 2 A g−1 and negligible capability degradation after 1000 cycles can be achieved. This result opens a new …

Vanadium-based materials are promising cathode materials for aqueous rechargeable zinc-ion batteries (ZIBs). However, up to now, the detailed Zn ion intercalation mechanisms are still not fully clear. In this work, we first show a new facile synthesis approach for V3O7·H2O nanoarray cathode with large mass loadings (1.0–12 mg cm−2). An empirical model is proposed to assess the utilization ratio of active materials under different mass loadings. Then, through the combination of first-principles calculations and a series of ex-situ characterizations, we identify for the first time a two-step Zn2+ intercalation mechanism in V3O7·H2O. The stepwise and reversible intercalation process is manifested by different diffusion energy barriers and segmented electrochemical kinetics in various discharge depths. The nanoarray binder-free electrode is also applied in pouch cells which show high capacities than state-of-the-art …

Aqueous energy devices are under the spotlight of current research due to their safety, low cost and ease of handling. Metal-organic frameworks (MOFs) and their derivatives have spurred extensive exploration as they provide a library of new electrode materials. The rich and structural flexibilities (such as metal nodes, ligands, pore structure) endow MOFs and MOFs-derivatives with vast opportunities for various energy devices. In this review, we discuss the correlation between MOF structural parameters and electrochemical performance for aqueous energy devices in the scope of zinc-based batteries (Zn-ion, Zn-alkaline and Zn-air batteries), potassium-ion batteries and supercapacitors. For each energy device, the effect of determinative factors and structural modulating strategies of MOFs and derivatives are highlighted. Finally, we summarize the challenges and provide our perspective about MOFs and …

Organic electrode materials (OEMs) are being investigated as promising candidates for aqueous zinc-ion batteries (AZIBs) owing to their environmental friendliness, cost-effectiveness, and structural diversity, and tunability. Understanding the correlation between structural regulation of OEMs and their electrochemical property in AZIBs is vital to rational design of OEMs. Herein, we first discuss the fundamentals of the energy storage mechanism of OEMs. Then, strategies to improve the electrochemical performance, including the specific capacity, voltage, rate capability, and cycling stability, are elaborated from the perspective of molecular engineering. Finally, we share our views on the remaining challenges and prospects of OEMs in AZIBs.

Sodium‐ion capacitors (SICs) have attracted extensive attentions due to their integration of high‐energy battery and high‐power capacitor as well as the naturally abundant sodium resource. A major challenge of current SICs is to achieve high rate performance and long‐cycle stability of the battery‐type anode. Herein, fast sodium storage is achieved from sodium titanate (Na2Ti3O7) arrays that are uniformly grown on highly conductive carbon nanofiber networks with a high mass loading of 5.6 mg cm−2. Nanowires and nanobelts of Na2Ti3O7 are both synthesized, and their Na‐ion storage properties are compared. Both arrays can be used as binder‐free and flexible electrodes, but the nanobelts exhibit higher specific capacity and better rate performance than the nanowires with similar mass loading. The difference between two types of nanostructures is ascribed to their different kinetics in ion/charge transport …

Materials that can produce large controllable strains are widely used in shape memory devices, actuators and sensors,, and great efforts have been made to improve the strain output, , –. Among them, ferroelastic transitions underpin giant reversible strains in electrically driven ferroelectrics or piezoelectrics and thermally or magnetically driven shape memory alloys,. However, large-strain ferroelastic switching in conventional ferroelectrics is very challenging, while magnetic and thermal controls are not desirable for practical applications. Here we demonstrate a large shear strain of up to 21.5% in a hybrid ferroelectric, C6H5N(CH3)3CdCl3, which is two orders of magnitude greater than that in conventional ferroelectric polymers and oxides. It is achieved by inorganic bond switching and facilitated by structural confinement of the large organic moieties, which prevents undesired 180° polarization switching …

An electrolyte cation additive strategy provides a versatile route for developing high‐energy and long‐life aqueous zinc‐ion hybrid capacitors. However, the mechanisms of energy storage and Zn anode protection are still unclear in Zn‐based systems with dual‐ion electrolytes. Here, a dual charge storage mechanism for zinc‐ion hybrid capacitors with both cations and anions adsorption/desorption and the reversible formation of Zn4SO4(OH)6·xH2O enabled by the Mg2+ additive in the common aqueous ZnSO4 electrolyte are proposed. Theoretical calculations verify that the self‐healing electrostatic shield effect and the solvation‐sheath structure regulation rendered by the Mg2+ additive account for the observed uniform Zn deposition and dendrite suppression. As a result, an additional energy storage capacity of ≈50% compared to that in a pure 2 m ZnSO4 electrolyte and an extended cycle life with capacity …

Electrolyzers coupling electrocatalytic hydrogen evolution with oxidation reactions of small organic molecules have the merits of reducing cell voltage and generating high‐value products. Herein, an electrolyzer is designed and optimized that can simultaneously achieve efficient hydrogen generation at the cathode, CO2 absorption by the catholyte, and methanol upgrading to formate at the anode. For these purposes, transition metal phosphides are used as the low‐cost catalysts. The unique electrolyzer exhibits a low working voltage of 1.1 V at 10 mA cm−2. Under optimal conditions, the Faraday efficiencies of hydrogen evolution and formic acid conversion reactions, which are the reaction products at the cathode and anode, respectively, are nearly 100% at various current densities from 10 to 400 mA cm−2. Meanwhile, the CO2 absorption rate is about twice that of the hydrogen generation rate, which is close to …

The {100} facet of single‐crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single‐crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li‐storage capacity. The first‐principle calculations demonstrate an ab in‐plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate), the cut‐off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li‐ion …

Aqueous rechargeable zinc‐ion batteries (ZIBs) have attracted considerable attention as a promising candidate for low‐cost and high‐safety electrochemical energy storage. However, the advancement of ZIBs is strongly hindered by the sluggish ionic diffusion and structural instability of inorganic metal oxide cathode materials during the Zn2+ insertion/extraction. To address these issues, a new organic host material, poly(2,5‐dihydroxy‐1,4‐benzoquinonyl sulfide) (PDBS), has been designed and applied for zinc ion storage due to its elastic structural factors (tunable space and soft lattice). The aqueous Zn‐organic batteries based on the PDBS cathode show outstanding cycling stability and rate capability. The coordination moieties (O and S) display the strong electron donor character during the discharging process and can act as the coordination arms to host Zn2+. Also, under the electrochemical environment …

Hydrogen production by water electrolysis is a sustainable and promising pathway to store surplus electricity from intermittent renewable energy. In conventional electrolyzers, hydrogen evolution and oxygen evolution reactions at the two electrodes run at the same temperature. In this work, we implement an asymmetric temperature modulation to enhance the water electrolysis rate in an alkaline solution. We revisit the thermodynamics of water electrolysis and determine by both simulations and experiments that the Gibbs free energy change required for alkaline water electrolysis under asymmetric temperature is lower than that under uniform average temperature. With the temperature difference of 40 K (possible for low-grade waste heat), the required voltage of asymmetric configuration decreases by 100 mV at the current density of 10 mA cm− 2 compared to the system operated at the same average temperature …

Research on two-dimensional (2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some major breakthroughs made in the field of 2D materials in last five years not only in developing novel synthetic methods and exploring new structures/properties but also in identifying innovative applications and pushing forward commercialisation. In this review, we provide a critical summary on the recent progress made in …

The slow kinetics of oxygen evolution reaction (OER) causes high power consumption for electrochemical water splitting. Various strategies have been attempted to accelerate the OER rate, but there are few studies on regulating the transport of reactants especially under large current densities when the mass transfer factor dominates the evolution reactions. Herein, NixFe1–x alloy nanocones arrays (with ≈2 nm surface NiO/NiFe(OH)2 layer) are adopted to boost the transport of reactants. Finite element analysis suggests that the high‐curvature tips can enhance the local electric field, which induces an order of magnitude higher concentration of hydroxide ions (OH−) at the active sites and promotes intrinsic OER activity by 67% at 1.5 V. Experimental results show that a fabricated NiFe nanocone array electrode, with optimized alloy composition, has a small overpotential of 190 mV at 10 mA cm−2 and 255 mV at …

Two-dimensional (2D) layered lead halide perovskites with large exciton binding energies, efficient radiative recombination, and outstanding environmental stability are regarded as supreme candidates for realizing highly compact and ultralow threshold lasers. However, continuouswave (CW) pumped lasing of 2D lead halide perovskites, as the precondition for the electrically pumped lasing, is still challenging. Here, we tackled this challenge by demonstrating lasing emission in phenylethylammonium lead iodide [(PEA) 2PbI4] embedded in a vertical microcavity under continuous pumping at room temperature. The millimeter-sized (PEA) 2PbI4 single crystal was obtained from a twostep seed-growth method, showing high crystallization, excellent thermal stability, and outstanding optical properties. We used the exfoliated (PEA) 2PbI4 thin flake as the gain medium to construct a vertical-cavity surface-emitting laser …

Research on two-dimensional (2D) materials has been explosively increasing in last seventeen years in varying subjects including condensed matter physics, electronic engineering, materials science, and chemistry since the mechanical exfoliation of graphene in 2004. Starting from graphene, 2D materials now have become a big family with numerous members and diverse categories. The unique structural features and physicochemical properties of 2D materials make them one class of the most appealing candidates for a wide range of potential applications. In particular, we have seen some major breakthroughs made in the field of 2D materials in last five years not only in developing novel synthetic methods and exploring new structures/properties but also in identifying innovative applications and pushing forward commercialisation. In this review, we provide a critical summary on the recent progress made in the field of 2D materials with a particular focus on last five years. After a brief background introduction, we first discuss the major synthetic methods for 2D materials, including the mechanical exfoliation, liquid exfoliation, vapor phase deposition, and wet-chemical synthesis as well as phase engineering of 2D materials belonging to the field of phase engineering of nanomaterials (PEN). We then introduce the superconducting/optical/magnetic properties and chirality of 2D materials along with newly emerging magic angle 2D superlattices. Following that, the promising applications of 2D materials in electronics, optoelectronics, catalysis, energy storage, solar cells, biomedicine, sensors, environments, etc. are described sequentially …

Among the various VO2 polymorphs, the layered compound, VO2(B), has been the most widely investigated lithium‐ion battery electrode material. For sodium‐ion electrodes, however, an amorphous solid may be more advantageous as a result of the open framework to facilitate ion insertion and the ability to tolerate volumetric changes. Herein, it is shown that the Na+ insertion properties of amorphous VO2 (a‐VO2) are superior to those of crystalline VO2(B). Amorphous VO2 exhibits a linear voltage characteristic over a 3 V range (4.0 to 1.0 V vs Na/Na+) leading to a reversible capacity as high as 400 mAh g−1 and rapid redox kinetics, which is attributed to its pseudocapacitive nature. The linear voltage characteristic over 3 V affords the opportunity of fabricating a symmetric Na‐ion battery in which the a‐VO2 material serves as both the positive electrode and the negative electrode. Such a symmetric battery offers …

Introduction of defects in a controllable way is important to modulate the electronic structure of catalysts toward enhancement of electrocatalytic activity. Herein we report that incorporation of fluorine into a cobalt phosphide alloy has a unique effect: it creates both F– anion doping and P vacancies, resulting in a nearly 15-fold enhancement of the catalytic activity for the hydrogen evolution reaction (HER) in neutral solution. The existence of dual defects in CoP was confirmed by extended X-ray absorption fine structure (EXAFS) curve fitting results and density functional theory calculations. We show that the dual-defect feature is beneficial for increasing the active-site exposure, tuning the surface wettability, and optimizing the electronic configuration of CoP for the HER. Our fluorine-based modulation protocol may be applicable to other metal alloy electrocatalysts toward more efficient energy conversion reactions.

Inkjet and extrusion printing are widely employed technologies in the field of printed electronics. They provide opportunity of manufacturing diverse electronic devices on various types of substrates by employing digital layouts under ambient conditions. In this short review, fundamentals about inkjet mechanisms and ink fluidic characteristics are presented. The interaction between individual droplets and that of droplets with substrates, which are pivotal to the printing resolution and uniformity, are analyzed. In addition, some issues on droplet‐based extrusion 3D printing are discussed as an extension of conventional inkjet printing. The recent progress in application of inkjet and extrusion printing in the field of electrochemical energy storage, ranging from batteries and supercapacitors to energy storage electrochromics, is also highlighted. Challenges and perspectives are discussed at the end. It is expected that …

In photocatalysis, the Schottky barrier in metal–semiconductor hybrids is known to promote charge separation, but a core–shell structure always leads to a charge build‐up and eventually shuts off the photocurrent. Here, we show that Au–Cu2O hybrid nanostructures can be continuously tuned, particularly when the Cu2O domains are single‐crystalline. This is in contrast to the conventional systems, where the hybrid configuration is mainly determined by the choice of materials. The distal separation of the Au–Cu2O domains in Janus nanostructures leads to enhanced charge separation and a large improvement of the photocurrent. The activity of the Au–Cu2O Janus structures is 5 times higher than that of the core–shell structure, and 10 times higher than that of the neat Cu2O nanocubes. The continuous structural tuning allows to study the structure–property relationship and an optimization of the photocatalytic …

The intrinsic activity of in-plane chalcogen atoms plays a significant role in the catalytic performance of transition metal dichalcogenides (TMDs). A rational modulation of the local configurations is essential to activating the in-plane chalcogen atoms but restricted by the high energy barrier to break the in-plane TM-X (X = chalcogen) bonds. Here, we theoretically design and experimentally realize the tuning of local configurations. The electron transfer capacity of local configurations is used to screen suitable TMDs materials for hydrogen evolution reaction (HER). Among various configurations, the triangular-shape cobalt atom cluster with a central sulfur vacancy (3CoMo-VS) renders the distinct electrocatalytic performance of MoS2 with much reduced overpotential and Tafel slope. The present study sheds light on deeper understanding of atomic-scale local configuration in TMDs and a methodology to boost the …

Hollow micro‐/nanostructures are widely explored for energy applications due to their unique structural advantages. The synthesis of hollow structures generally involves a “top‐down” casting process based on hard or soft templates. Herein, a new and generic confinement strategy is developed to fabricate composite hollow fibers. A thin and homogeneous atomic‐layer‐deposition (ALD) Al2O3 layer is employed to confine the pyrolysis of precursor fibers, which transform into metal (or metal oxide)–carbon composite hollow fibers after removal of Al2O3. Because of the uniform coating by ALD, the resultant composite hollow fibers exhibit a hollow interior from heads to ends even if they are millimeter long. V, Fe, Co, and Ni‐based hollow nanofibers, demonstrating the versatility of this synthesis method, are successfully synthesized. Because of the carbon constituent, these composite fibers are particularly useful for …

Efficient thermal protection is essential to battery safety. Here, a self‐adaptive strategy is demonstrated to circumvent the thermal runaway of aqueous zinc‐ion batteries, by using a zinc chloride‐enriched hygroscopic hydrogel electrolyte. At high temperatures, water inside the hydrogel can quickly evaporate to dissipate the heat generated. Concurrently, excessive water evaporation causes a sudden drop in the ion diffusion of the hydrogel electrolyte, thereby effectively restricting the migration of ions and shutting down the battery. When the temperature lowers, the hydrogel absorbs water from the air and the battery recovers its function. The evaporation and regeneration of water in the hydrogel electrolytes are highly reversible, thus realizing intelligent and efficient thermal self‐protection of zinc‐ion batteries. By properly designing and engineering the hygroscopic hydrogel electrolytes, it is believed that other …

Direct inkjet printing of functional inks is an emerging and promising technique for the fabrication of electrochemical energy storage devices. Electrochromic energy devices combine electrochromic and energy storage functions, providing a rising and burgeoning technology for next‐generation intelligent power sources. However, printing such devices has, in the past, required additives or other second phase materials in order to create inks with suitable rheological properties, which can lower printed device performance. Here, tungsten oxide nanocrystal inks are formulated without any additives for the printing of high‐quality tungsten oxide thin films. This allows the assembly of novel electrochromic pseudocapacitive zinc‐ion devices, which exhibit a relatively high capacity (≈260 C g−1 at 1 A g−1) with good cycling stability, a high coloration efficiency, and fast switching response. These results validate the …

Tailoring the nanostructure and composition of transition metal nitrides is highly important for their use as potent low-cost electrocatalysts. Cobalt nitride (CoN) exhibits strong catalytic activity for oxygen evolution reaction (OER). However, its poor catalytic efficiency for oxygen reduction reaction (ORR) hinders its application in rechargeable zinc-air batteries (ZABs) as the air cathode. In this work, we deploy the effective strategy of Mn doping to improve both OER and ORR activity of CoN nanowires as the cathode material for ZAB. Theoretical calculation predicts that moderate Mn doping in cobalt nitride results in a downshift of the d-band center and reduces the adsorption energy of reaction intermediates. With ∼10 at% Mn dopants, stronger catalysis activities for both OER and ORR are achieved compared to pure CoN nanowires. Subsequently, both aqueous and flexible quasi-solid-state ZABs are constructed …

Metal‐ion capacitors are being widely studied to reach a balance between power and energy output by combining the merits of conventional batteries and capacitors. The main challenge for Na‐ion capacitors is that the battery‐type anode usually has unsatisfactory power density and long‐term stability since most Na host materials have a poor kinetic and structural stability. Herein, asymmetric hollow bowl‐like carbon (HBC) materials are rationally designed and fabricated through an in situ hard‐template approach. The formation originates from a subtle control of capillary force and the mechanical strength of the carbon shell. The HBCs possess abundant mesopores, high volumes of accessible surface area as well as an open macropore network. As a 3D host, MoSe2 nanocrystals are anchored onto the HBC matrix by a solid‐phase reaction. The obtained MoSe2@HBC nanobowl electrode exhibits …

Metal-ion hybrid capacitors are regarded as promising power sources for portable electronics because of numerous opportunities in designing the anode/cathode couple to realize high performance and device flexibility. Here we demonstrate our rational design of a porous-fiber network based electrode for quasi-solid-state flexible Na-ion hybrid capacitors. A SiO2-etching approach is deployed to synthesize the freestanding porous carbon nanofiber (PCNF) membrane that is both mechanically robust and light (~1 mg cm−2). The PCNF serves as a 3D scaffold for the uniform growth of MoS2@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanosheets. The resultant PCNF@MoS2@PEDOT double core/shell nanofiber electrode not only maintains the intrinsic high-capacity of MoS2 for Na-ion storage, but also renders long-term cyclability and high rate performance. The constructed quasi-solid-state Na-ion …

Thermogalvanic cells(also known as thermo-electrochemical cells) that convert waste heat energy to electricity are a new type of energy conversion device. However, the electron transfer kinetics and mass transfer of redox couples have not been thoroughly studied. Here, the ion reaction and charge transport in thermogalvanic cells are investigated by electrochemical impedance analysis. We first propose the detailed impedance model followed experimental verification on three types of electrode materials. Parameters including kinetic rate constants and ion diffusion coefficients for the electrodes are obtained by fitting the impedance data. Our study shows explicitly that impedance analysis can provide useful information on selecting suitable electrode materials for thermogalvanic cells.

Organic–inorganic hybrid perovskites have been considered as promising gain materials for lasing. Despite previous reports of lasing from nanocrystals, thin films and single crystals, the stability of perovskite lasers has been a challenge for its practical applications. Herein, a scalable strategy to prepare ultrastable perovskite@polymer hybrid fibers by employing a facile emulsion electrospinning approach is demonstrated. During the electrospinning process, polymethyl methacrylate (PMMA) first solidifies into an outer shell layer. Meanwhile, emulsion drops containing poly(vinylidene fluoride) (PVDF) and perovskite precursor are pushed inward and evolve into perovskite nanocrystals covered by PVDF. The PMMA with smooth surface benefits the light transport and the water‐resistant PVDF blocks the moisture. The methylammonium lead bromide perovskite‐embedded fibers can emit intensive light after storage in …

To boost the electrocatalytic activity of metal nanoparticles, it is important to rationally design the composition and surface atomic structure, and develop efficient synthesis protocols. Herein, a facile one‐pot self‐templated method for preparing PtPdAg hollow nanodendrites (HNDs) is deployed. These HNDs possess rich atomic steps and grain boundaries, leading to evidently higher catalytic activity in methanol electrooxidation reaction than commercial Pt black and solid particles with smooth surfaces. From control experiments and density functional theory calculations, it is proven that the tri‐metallic HND has a stronger electronic coupling as compared with the PtPd and PtAg nanoparticles. As a result, the PtPdAg HNDs show high anti‐poison capability and catalytic activity for methanol oxidation reaction. This study provides a new strategy for controllable synthesis of hollow alloy nanocatalysts with high efficiency.

Li–O2 batteries (LOB) potentially have the highest specific capacity among all types of metal‐ion batteries but suffer severely from cycle instability and low energy efficiency. In this work, an integrated cathode is fabricated that contains an amorphous MoS2 thin layer deposited on a 3D conductive carbon scaffold to improve the energy efficiency to ≈83% and cycle life up to 190 cycles. An advanced pressure‐tuned stop‐flow atomic layer deposition (ALD) method is employed to deposit a ≈5 nm thick amorphous MoS2 layer on carbon nanotube forest‐covered graphite foam. It is established that this integrated 3D cathode exhibits high catalytic activity for both oxygen reduction reaction and oxygen evolution reaction. The benefit of the ALD MoS2 in lowering the energy barrier is also supported by first‐principles calculations. Finally, quasi‐solid state flexible LOBs are also assembled that can be stably discharged up …

Various carbon nanomaterials are being widely studied for applications in supercapacitors and Li‐ion batteries as well as hybrid energy storage devices. Dual‐carbon batteries (DCBs), in which both electrodes are composed of functionalized carbon materials, are capable of delivering high energy/power and stable cycles when they are rationally designed. This Review focuses on the electrochemical reaction mechanisms and energy storage properties of various carbon electrode materials in DCBs, including graphite, graphene, hard and soft carbon, activated carbon, and their derivatives. The interfacial chemistry between carbon electrodes and electrolyte is also discussed. The perspective for further development of DCBs is presented at the end.

Electrochemical water splitting has been regarded a promising technology to provide a mobile and sustainable energy supply in the form of hydrogen fuel. The key to further development towards industrial application lies in high-efficiency and low-cost electrocatalysts. In recent years, new attention has been paid to amorphous electrocatalysts, which have short-range atomic ordering instead of translational periodicity. The structural flexibility and rich defects associated with amorphous catalyst materials offer enormous opportunities for electrochemical water splitting. In this Perspective, we elaborate on recent studies of amorphous electrocatalysts for electrochemical water splitting. Our discussion covers the diverse amorphization strategies, the positive role of structural flexibility and defects in enriching active sites, as well as challenges in the characterization of local geometry and in improving electrochemical …

Water electrolysis represents a promising sustainable hydrogen production technology. However, in practical application which requires extremely large current densities (>500 mA cm−2), the oxygen evolution reaction (OER) becomes unstable and kinetically sluggish, which is a major hurdle to large-scale hydrogen production. Herein, we report an exceptionally active and binder-free NiFe nanowire array based OER electrode that allows durable water splitting at current densities up to 1000 mA cm−2 up to 120 hours. Specifically, NiFe oxyhydroxide (shell)–anchored NiFe alloy nanowire (core) arrays are prepared via a magnetic-field-assisted chemical deposition method. The ultrathin (1–5 nm) and amorphous NiFe oxyhydroxide is in situ formed on the NiFe alloy nanowire surface, which is identified as an intrinsically highly active phase for the OER. Additionally, the fine geometry of the hierarchical electrode can …