Changshin Jo

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) are spotlighted as next-generation energy storage devices; however, the carbon cathodes usually dictate their performance. Herein, we aim to optimize the electrochemical performance of the carbon cathodes through particle morphology control along with porosity and surface-active site control. N-doped spherical mesocelluler carbon foam (S-MCF-N) is synthesized using a mesoporous silica template, and spherical mesocelluler carbon foam (S-MCF) and irregularly shaped mesocellular carbon foam (MSUF-C) are synthesized as control samples. Consequently, S-MCF-N shows the best ion storage capability with its large surface area, with active sites that cause redox reactions and high electrical conductivity. In particular, the spherical morphology of S-MCF-N achieves a higher tap density and can reduce the electrode thickness, which decreases the diffusion …

MXenes, the two-dimensional metal carbides and nitrides, have been considered a new class of electrode materials with their noticeable performance in various energy storage systems. Furthermore, the unique property and morphology allow MXenes to be assembled into freestanding films, which can be applied in energy storage devices with lightweight and high energy density. However, their tendency to restack and aggregate remains a challenge to enhance the electrochemical performance of MXenes. In this study, we propose a facile method to fabricate a porous MXene-TiO2 freestanding anode with the help of a flashlight. Simply heating the MXene films with a flashlight in milliseconds increases the interlayer spacing of the MXenes and simultaneously forms TiO2 on the MXene surface. Along with the widened interlayer and formation of TiO2, improved wettability, easy electrolyte penetration, and reduced …

The synthetic procedure and characterization of carbon nanofibers (CNFs) grown on carbon cloth (CC) are explored in this study, with a focus on their potential application as electrodes in vanadium redox flow batteries (VRFBs). CC offers an attractive platform for surface modification owing to its conductive properties and three-dimensional architecture, while the N-doped CNFs formed by nitrogen (N) rich composition of melamine precursor enhance wettability of electrolyte and redox reactivity of vanadium ions. Electrochemical assessments reveal that NCC electrodes significantly increase voltage efficiency (VE) and capacity retention in VRFBs compared to bare CC (BCC) electrodes. Notably, NCC demonstrates a VE of 65.9%, surpassing the 55.9% of BCC electrodes. Additionally, NCC maintains superior capacity retention under varying current densities, a crucial factor for VRFBs. Long-term stability tests over …

Lithium-ion batteries (LIBs) have become integral to various aspects of the modern world and serve as the leading technology for the electrification of mobile devices, transportation systems, and grid energy storage. This success can be attributed to ongoing improvements in LIB performance resulting from collaborative efforts between academia and industry over the past several decades. However, existing methods for calculating the energy density at the electrode level remain ambiguous and complex, complicating the comparison of energy density metrics across scientific reports. From this perspective, we highlight several testing parameters that are frequently overlooked in the academic literature but are critical for the practical applicability of LIBs. We discuss the metrics that influence the energy density, including the (i) loading level, (ii) electrode density, and (iii) N/P ratio, as well as the relationship between …

Approaching an efficient anion exchange membrane water electrolyzer (AEMWE) with satisfactorily high kinetics in the alkaline hydrogen evolution reaction (HER) is desired. We design an advanced platinum (Pt) single atom (SA)-based electrocatalyst by incorporating the Ni nanoparticle as an artificial ensemble site adjacent to Pt SA. The designed Pt SA electrocatalyst achieves higher areal current density (500 mA cm−2 at 1.8 V) in the single cell of the AEMWE and better cell voltage stability than the Pt/C electrocatalyst. The Ni nanoparticle assists in separating the binding sites of H* and OH*, in which Ni atoms provide adsorption sites for H*, while OH* adsorbs on the Pt SA. This separation effect drastically accelerates the energy barrier required for the water dissociation reaction in the Volmer step and simultaneously optimizes the H* and OH* binding energy, which extremely enhances the alkaline HER kinetics …

Mesoporous metal oxides exhibit excellent physicochemical properties and are widely used in various fields, including energy storage/conversion, catalysis, and sensors. Although several soft‐template approaches are reported, high‐temperature calcination for both metal oxide formation and template removal is necessary, which limits direct synthesis on a plastic substrate for flexible devices. Here, a universal synthetic approach that combines thermal activation and oxygen plasma to synthesize diverse mesoporous metal oxides (V2O5, V6O13, TiO2, Nb2O5, WO3, and MoO3) at low temperatures (150–200 °C), which can be applicable to a flexible polymeric substrate is introduced. As a demonstration, a flexible micro‐supercapacitor is fabricated by directly synthesizing mesoporous V2O5 on an indium‐tin oxide‐coated colorless polyimide film. The energy storage performance is well maintained under severe …

Hierarchical superstructures have novel shape‐dependent properties, but well‐defined anisotropic carbon superstructures with controllable size, shape, and building block dimensionality have rarely been accomplished thus far. Here, a hierarchical assembly technique is presented that uses spinodal decomposition (SD) to synthesize anisotropic oblate particles of mesoporous carbon superstructure (o‐MCS) with nanorod arrays by integrating block‐copolymer (BCP) self‐assembly and polymer‐polymer interface behaviors in binary blends. The interaction of major and minor phases in binary polymer blends leads to the formation of an anisotropic oblate particle, and the BCP‐rich phase enables ordered packing and unidirectional alignment of carbon nanorods. Consequently, this approach enables precise control over particles’ size, shape, and over the dimensionality of their components. Exploiting this functional …

Nowadays, thickness optimization of an electrode is considered an effective approach to achieve a high energy density or high areal capacity of Li-ion batteries. In this paper, we report a simple electrospinning technique to develop free-standing sheet bundles of lithium titanium oxide (LTO) nanowires with a readily controlled thickness of electrodes. The LTO nanowire sheet bundles (LNSBs) can show a very high areal capacity as an anode due to its microscale layer-by-layer configuration in which the nanoscale LTO nanowires are networked in each microscale layer. Such unique structures with interspaces formed between the multiple stacked sheet layers should promote electrolytes to efficiently penetrate through the thick electrode layer. Nanoscale wire assemblies can also increase the transfer rates of ions and electrons during the lithiation/delithiation processes. Consequently, the fabricated LNSB electrode …

Ordered mesoporous carbons (OMCs) are promising materials for cathode materials of a Zn ion hybrid capacitor (Zn HC) due to their high surface area and interconnected porous structure. Graphitization of the framework and nitrogen doping have been used to improve the energy storage performance of the OMCs by enhancing electrical conductivity, pseudocapacitive reaction sites, and surface affinity toward aqueous electrolytes. Thus, when both methods are simultaneously implemented to the OMCs, the Zn HC would have improved energy storage performance. Herein, we introduce a facile synthetic method for N-doped mesoporous graphitic carbon (N-mgc) by utilizing polystyrene-block-poly(2-vinlypyridine) copolymer (PS-b-P2VP) as both soft-template and carbon/nitrogen sources. Co-assembly of PS-b-P2VP with Ni precursors for graphitization formed a mesostructured composite, which was converted to N …

Zinc (Zn) metal has attracted considerable attention because of its natural abundance and stability in aqueous environments compared with lithium/sodium metal anodes. Moreover, Zn metal as anode showed a high theoretical capacity (820 mAh g−1), high energy per volume (5855 mA cm−3), and low operational potential (–0.78 V vs SHE) in electrochemical systems. However, Zn metal suffers from dendrite growth and poor plating/stripping reversibility, resulting from inhomogeneous Zn ion flux and contamination by generally used glass fiber membranes (GFs) as separators. Although studies to inhibit dendritic Zn growth have been conducted, dendritic Zn remains still a major problem during long-term cycling under practical rate and capacity conditions. In this context, it is essential to investigate Zn deposition behavior from initial nucleation to Zn growth morphologies after long-term cycling.Among the …

Soft-templating methods, which utilize the block copolymer (BCP)-derived self-assembly with inorganic precursors, have been extensively applied to synthesize a wide range of mesoporous materials. Compared with other synthetic approaches including template-free and hard templating methods, the soft-templating method offers significant advantages for customizing various compositions, particle morphologies, and pore sizes/structures of mesoporous materials. During the last decade, various soft templating approaches have been developed to synthesize functional mesoporous materials for a variety of applications. In this review, we outline recent developments in synthetic approaches for mesoporous materials and their potential applications, particularly in energy storage systems (ESSs) such as batteries and supercapacitors. In addition, this review provides general information about soft-templating methods …

Porous carbon particles, and a positive electrode active material and a lithium secondary battery including the same. This may improve the energy density of the lithium secondary battery by applying a porous electrode containing micropores and mesopores and having a uniform size distribution and shape as a positive electrode material.

Nowadays, as the use of fossil fuels is suppressed for achieving carbon neutrality, rechargeable battery is considered as a key factor to lead sustainable society. As far, the most developed and already commercialized batteries are lithium-ion batteries (LIBs). However, as the demand for LIBs is increasing, there are also several issues in the process of obtaining high-performance batteries. First, as the price of raw materials in LIB rises rapidly, a cost issue arises. In addition, as the fire accidents have occurred consistently due to overcharging or use of organic electrolyte, safety concerns are being raised. Finally, the environmental issues are emerging in the process of mining raw material and disposal of waste batteries. Therefore, a cheap, safe, and environmentally friendly battery system is needed as an alternative to LIBs.In this situation, a battery system called seawater battery (SWB) using seawater as a raw …

Aqueous Zn-ion batteries or capacitors have attracted great interest for their potential use in grid-scale energy storage systems (ESSs). They have suitable properties such as high safety, low-cost materials, and stability of Zn2+ in aqueous systems. The anode of these systems is mainly based on metallic Zn; however, corrosion of the metal surface and formation of dendrites inhibit their long-term cycle stability. It is thus necessary to find a material that can host Zn2+ in a low voltage range and enhance the electrochemical performance. Among various possible strategies, herein we applied nanostructuring to prepare mesoporous WO3 as anode material and compared the change in the electrochemical performance to that of bulk WO3. After unveiling the effect of the nanostructure, we conclude that the present nanomaterials show great potential as electrode materials for aqueous Zn-ion systems.

Achievement of an efficient and stable electrocatalytic glycerol oxidation reaction (EGOR) is limited by a lack of strategies for designing advanced electrocatalysts that satisfy the desired product selectivity, high electrocatalytic activity, and stability. Here, we report that the reaction pathway of EGOR can be modulated by the incorporation of amorphous antimony oxide (SbOx) on the surface of a Pt nanoparticle electrocatalyst (SbOx-Pt), which creates highly selective glycerol oxidation to dihydroxyacetone (DHA), one of the most valuable products of EGOR. The selective control of adsorption behaviors of glycerol oxidation products allows for SbOx to act as a reaction pathway modulator. Moreover, SbOx deposition on a Pt surface also enhances the stability, electrocatalytic activity, and glycerol conversion of the Pt electrocatalyst, and thus promotes the EGOR. As a result, the SbOx-Pt electrocatalyst achieves a high DHA …

With the increasing demand for cost-effective and safe energy storage systems, seawater batteries (SWBs) are establishing themselves in the field of rechargeable batteries. In particular, cathode materials based on the intercalation mechanism have received considerable attention owing to their low overpotential and high energy efficiency. In this study, nickel hexacyanoferrate (NiHCF) is used as an intercalation cathode material for SWB. NiHCF, a type of Prussian blue analog, has the advantages of a large interstitial volume to insert Na-ions and stability into seawater; however, it is often fabricated in a defect-rich structure. Therefore, the chelating effect of NiHCF is studied, and its structural and electrochemical properties are investigated. After introducing a chelating agent, defect-less NiHCF can be fabricated, and the well-constructed structure affects the electrochemical properties of the NiHCF. The structural …

The development of high-performance sodium storage materials is becoming necessary owing to the limited availability of lithium. Materials undergoing a multiredox-reaction mechanism are highly promising for sodium-ion batteries (SIBs) and sodium-ion hybrid capacitors (SICs). In this study, we propose an operational strategy for improving the cycling lifespan of multiredox-reaction materials in SIBs and SICs. The efficiency of this strategy was evaluated using a Na2VTi(PO4)3@C (NVTP@C) electrode with three redox reaction sites (V2+/V3+, Ti3+/Ti4+, and V3+/V4+). Electrochemical studies revealed that the exclusion of the most unfavorable reaction of NVTP@C (i.e., the V2+/V3+ redox reaction) is effective in reducing the voltage hysteresis of Na||NVTP@C half-cells and NVTP@C||AC hybrid ion capacitor systems, thereby extending their cycling life. Thus, based on a fundamental understanding of multiredox …

To increase the energy density of lithium-ion batteries (LIBs), high-capacity anodes which alloy with Li ions at a low voltage against Li/Li+ have been actively pursued. So far, Si has been studied the most extensively because of its high specific capacity and cost efficiency; however, Ge is an interesting alternative. While the theoretical specific capacity of Ge (1600 mAh g–1) is only half that of Si, its density is more than twice as high (Ge, 5.3 g cm–3; Si, 2.33 g cm–3), and therefore the charge stored per volume is better than that of Si. In addition, Ge has a 400 times higher ionic diffusivity and 4 orders of magnitude higher electronic conductivity compared to Si. However, similarly to Si, Ge needs to be structured in order to manage stresses induced during lithiation and many reports have achieved sufficient areal loadings to be commercially viable. In this work, spinodal decomposition is used to make secondary particles …

Metallic Zn anodes have recently attracted attention for use in large-scale energy storage systems; however, controlling the nucleation and growth behaviors of Zn is essential owing to its poor reversibility. In this study, we employed a protective layer (denoted XPpl) fabricated using xanthan gum and poly(ethylene oxide) (PEO). This layer exhibited a structured surface morphology and abundant oxygen-containing functional groups. When only glass fiber membrane (denoted GF) was used, Zn metal anodes polluted with dendritic Zn and broken fibers were observed after cycling. Upon introducing XPpl, dendrite-free Zn deposition was observed, and Zn metal was physically/chemically protected from the GF. An XPpl-protected ZnǁCu cell could undergo long-term operation for >5000 cycles at 2 mA cm−2. This study will provide insights into critical factors that affect Zn nucleation and growth, enabling accurate factor …

The growing use of renewable energy accelerates research on energy storage systems (ESSs) to accommodate the distributed nature of power sources and fluctuation in supply and demand. The commercially adopted system for ESSs is lithium-ion batteries (LIBs), which are actively studied for recent years. However, the use of rare resources such as Li, Ni and Co, as well as volatile and flammable organic electrolytes, cause environmental problems and fire hazards. Therefore, new type of environmentally friendly and safe ESSs are needed to meet the future demand.In this regard, the aqueous zinc-ion hybrid supercapacitors (ZHSCs) are assumed as the remarkable candidate for ESSs. ZHSCs consist of battery-type Zn metal anode and capacitor-type carbon cathode with different ion storage mechanisms. Because they have unique design of electrodes, they can combine the advantages of existing batteries …

Because large-scale lithium-ion battery (LIB) packs are compactly constructed using many LIB cells, one battery can cause fire of the other LIB cells when a few cells of them are damaged by accident owing to the latent risk of thermal decomposition reactions. To alleviate this problem, research seeks to provide an understanding of the gas generating mechanisms during cycling, electrolyte decomposition, and electrode material reactions. Understanding gas behaviors can prevent propagation of a battery fire and other hazardous situations. Therefore, in this study, we investigate commercial 18,650 cylindrical cells with long-term cycling. A lab-made in-situ Raman spectroscopic system and comprehensive transient electrochemical analyses are utilized to explore four gas expulsion phases. In addition, gas generation data are assessed for various overcharging voltage cutoffs (4.2–4.6 V). For the first time, furthermore …

Fluorine (F) is regarded as a key element in electrolytes for sodium metal anodes (SMAs) because of the formation of NaF containing solid–electrolyte interphase (SEI) layers; however, the high-cost and HF formation issues experienced by F-based electrolytes should be addressed. Herein, F-free, cost-effective 1 M NaBH4/ether-based electrolytes are proposed, motivated by the recent speculation that NaH is a “good SEI layer.” The time-of-flight secondary ion mass spectrometry (TOF-SIMS) results of sodium metal electrodes after galvanostatic cycling demonstrated that NaH is a major component of the SEI layer. In addition, the native oxide surface of sodium was converted into NaH and NaBO2 after soaking in the electrolytes, implying that “SEI reconstruction” occurred by chemical reduction. Accordingly, significantly longer cyclability was obtained in the Na‖Na symmetric cell (1200 h, 1 mA cm−2, 1 mA h cm−2 …

The current collector (CC) collects electrons from electrode materials and transports them to the external circuit. Although the CC is an essential part of battery configuration, it has not received considerable attention because there are “champion materials” such as Al and Cu foils in the commercial market. However, in accordance with the diversification of battery systems and the development of high energy density lithium-ion batteries, conventional CCs cannot address emerging issues. In particular, for alkali-metal-based or anode-free systems, a safety issue occurs due to unstable metal plating on CC. Here, we examined the roles of CCs in battery systems and categorized the problems occurring in CCs. Moreover, we especially focused on the coating methods among CC modification because surface coating is facile and has a wide scope of application. We paid attention to the latest research progress (2016 …

The rapid transport of alkali ions in electrodes is a long‐time dream for fast‐charging batteries. Though electrode nanostructuring has increased the rate‐capability, its practical use is limited because of the low tap density and severe irreversible reactions. Therefore, development of a strategy to design fast‐charging micron‐sized electrodes without nanostructuring is of significant importance. Herein, a simple and versatile strategy to accelerate the alkali ion diffusion behavior in micron‐sized electrode is reported. It is demonstrated that the diffusion rate of K+ ions is significantly improved at the hetero‐interface between orthorhombic Nb2O5 (001) and monoclinic MoO2 (110) planes. Lattice distortion at the hetero‐interface generates an inner space large enough for the facile transport of K+ ions, and electron localization near oxygen‐vacant sites further enhances the ion diffusion behavior. As a result, the interfacial …

Metal fluoride cathode materials, which are cost-effective and have large theoretical capacities, can be used in lithium-ion batteries (LIBs) to reduce the cost of these batteries. However, they have intrinsically low electrical conductivity and high overpotential. Herein, we report a bottom-up approach to synthesize NiF2/porous carbon (NPC) nanocomposites using an ammonium fluoride (NH4F) treatment. In this process the nickel precursor in the porous carbon is fluorinated under the solventless condition without hazardous reagents; thus, lower toxicity and higher yield compared to those of traditional methods can be achieved. Furthermore, we demonstrate the formation mechanism of NiF2 according to the reaction temperature. As a cathode material for LIBs, NPC nanocomposites exhibit an outstanding initial reversible capacity of 830 mAh g−1 at a current density of 50 mA g−1 and excellent rate performance of 487 …

The inherent risk of side reactions in lithium ion batteries (LIBs) is a crucial issue for large battery packs. To mitigate this problem, there have been previous studies that have attempted to reveal the possible chemical reactions from decomposition of electrolytes and electrode materials’ reactions during cycling. In particular, the gases expelled during decomposition have garnered research attention as they are explosive, flammable, toxic, and raise the inner pressure of a cell drastically. In addition, it is important to understand thermal effects on gas evolution or degradation of the electrode layer because batteries are normally exposed to a warm operation condition. Herein, the gases expelled within commercial 18650 cylindrical type LIB cells were investigated in moderate thermal conditions in a charged state. The investigation was conducted using a lab-made in situ Raman spectroscopic analysis system and …

The ever-growing demand for high performance energy storage systems has fueled the development of advanced electrode materials with light weight, high energy/power densities, and stable cycle life. Mesoporous materials play an important role in achieving these goals because of their unique features such as high surface area, tunable pore size, pore volume, and pore structures, as well as adjustable particle size and morphology. In this review, we summarize the recent progress in the synthesis of mesoporous materials and their applications in lithium-ion batteries (LIBs) and lithium-ion hybrid supercapacitors (Li-HSCs) over the past ten years. The block copolymer guided soft-template route is highlighted as a simple and versatile tool for designing mesoporous materials with controlled nano-and macrostructures without complicated synthetic procedures. The structural/morphological benefits of …

In this study, sodium cobalt fluoride (NaCoF3)/reduced graphene oxide (NCF/rGO) nanocomposites were fabricated through a simple one-pot solvothermal process and their electrochemical performance as cathodes for Li-ion batteries (LIBs) was investigated. The NCF nanoclusters (NCs) on the composites (300–500 nm in size) were formed by the assembly of primary nanoparticles (~20 nm), which were then incorporated on the surface of rGO. This morphology provided NCF NCs with a large surface area for efficient ion diffusion and also allowed for close contact with the conductive matrix to promote rapid electron transfer. As a cathode for LIBs, the NCF/rGO electrode achieved a high reversible capacity of 465 mAh·g−1 at 20 mA·g−1 via the conversion reaction, and this enhancement represented more than five times the reversible capacity of the bare NCF electrode. Additionally, the NCF/rGO electrode exhibited both better specific capacity and cyclability within the current density testing range (from 20 to 200 mA·g−1), compared with those of the bare NCF electrode.

The gravimetric and volumetric energy densities of lithium-ion batteries are key parameters for their implementation in real-life devices, yet to date, these values are documented differently both in academic and industrial reports, which makes the comparison of advances in this field challenging. This ambiguity stems from calculation methods that take into account different battery components, and since certain cell design parameters such as the mass loading and electrode density are often omitted, it is difficult to find out what assumptions are made in the calculations. Herein, we present calculation methods for the specific energy (gravimetric) and energy density (volumetric) that are appropriate for different stages of battery development: (i) material exploration, (ii) electrode design, and (iii) cell level engineering. These calculations help establishing a fair and robust method to compare energy metrics, and we …

Lithium (Li) metal is an ideal anode material for next-generation batteries. However, the commercialization of Li metal-based batteries is impeded by uncontrollable Li dendrite formation and the accumulation of a solid-electrolyte interphase (SEI). Recently, various polymers have been investigated to form a stable SEI layer on Li metal and extend its cycle life. In this study, a polymer film composed of sodium alginate (Na-Alg), which is a natural biopolymer obtained from brown algae, and poly(ethylene oxide) (PEO), was used as a separator. Na-Alg sustained the film structure and PEO facilitated Li-ion diffusion by absorbing the liquid electrolyte. Without using any additives in the commercial carbonate electrolyte, this method extended the cycle life of a Li metal symmetric cell to 1000 h with an overpotential <10 mV, and the cycle life of a full-cell (LiNi0.6Co0.2Mn0.2O2 cathode) to 200 cycles. This study suggests that …

The measured capacitance, modulus and strength of carbon nanotube-polyaniline (CNT-PANI) composite electrodes render them promising candidates for structural energy storage devices. Here, CNT-PANI composite electrodes are manufactured with electrodeposition of PANI onto the bundle network of CNT mats produced via a floating catalyst chemical vapour deposition process. PANI comprises 0% to 30% by volume of the electrode. The composition, modulus, strength and capacitance of the electrodes is measured in the initial state, after the first charge, and after 1000 charge/discharge cycles. Electrode modulus and strength increase with increasing CNT volume fraction; in contrast, the capacitance increases with increasing PANI mass. Charging or cycling reduce the electrode modulus and strength due to a decrease in CNT bundle volume fraction caused by swelling; the electrode capacitance also …

Owing to the demand for low‐cost batteries with safety, Na‐seawater batteries (SWBs) have received considerable attention as a new energy storage system (ESS). In SWB, it is necessary to use an advanced oxygen evolution/reduction reaction (OER/ORR) catalyst for high energy efficiency (EE) in the cathode and a good sodium storage material for a highly reversible capacity in the anode part. In this study, nanostructured and N and P dual‐doped hard carbon is fabricated by simply carbonizing abundant biomass, pine pollen. The oxygen electrocatalytic performance of pine pollen carbon (PPC) for a cathode is confirmed by a seawater half‐cell test, which exhibits the lowest overpotential reported among Pt/C (20 wt%) and commercial hard carbon (HC) electrodes. The sodium‐storage performance of PPC as an anode active material is tested using a coin‐type Na half‐cell, which exhibits a higher reversible …

Ultrathick battery electrodes are appealing as they reduce the fraction of inactive battery parts such as current collectors and separators. However, thick electrodes are difficult to dry and tend to crack or flake during production. Moreover, the electrochemical performance of thick electrodes is constrained by ion and electron transport as well as fast capacity degradation. Here, we report a thermally induced phase separation (TIPS) process for fabricating thick Li-ion battery electrodes, which incorporates the electrolyte directly in the electrode and alleviates the need to dry the electrode. The proposed TIPS process creates a bicontinuous electrolyte and electrode network with excellent ion and electron transport, respectively, and consequently achieves better rate performance. Using this process, electrodes with areal capacities of more than 30 mAh/cm2 are demonstrated. Capacity retentions of 87% are attained over …

Lithium (Li) metal is a promising anode material for next-generation batteries because of its low standard reduction potential (−3.04 V vs. SHE) and high specific capacity (3860 mA h g−1). However, it is still challenging to directly use Li metal as anode material in commercial batteries because of unstable Li dendrite formation and accumulated solid–electrolyte interphase. Possible methods that can suppress the unwanted formation of Li dendrites are (i) by increasing the electrode surface area and (ii) formation of porosity for confining Li. Here, we tested microporous (<2 nm) carbon and mesoporous (2–50 nm) carbon as host materials for the Li metal anode to avoid their degradation during cycling of lithium metal batteries (LMBs). Mesoporous carbon was more effective than microporous carbon as a host material to confine the Li metal and the lifetime of mesoporous carbon was more than twice as long as those of …

Off-grid energy storage devices are becoming increasingly important to power distributed applications, such as the Internet of things, and smart city ubiquitous sensor systems. To date, this has been achieved by combining an energy storage device, e.g., a battery or capacitor with an energy harvester, e.g., a solar cell. However, this approach inherently increases the device footprint and the output voltages of energy harvesters often do not match those required by energy storage device. Here we propose the first photo-rechargeable zinc-ion capacitors, where graphitic carbon nitride acts simultaneously as the capacitor electrode and light harvesting material. This approach allows light to be used to recharge the capacitor directly and they can be operated in a continuous light powered mode. These capacitors show a photo-rechargeable specific capacitance of ∼11377 mF g–1, a photo-charging voltage response of …

In this work we show for the first time that a continuous plasma process can synthesize materials from bulk industrial powders to produce hierarchical structures for energy storage applications. The plasma production process’s unique advantages are that it is fast, inexpensive, and scalable due to its high energy density that enables low-cost precursors. The synthesized hierarchical material is comprised of iron oxide and aluminum oxide aggregate particles and carbon nanotubes grown in situ from the iron particles. New aerosol-based methods were used for the first time on a battery material to characterize aggregate and primary particle morphologies, while showing good agreement with observations from TEM measurements. As an anode for lithium ion batteries, a reversible capacity of 870 mA h g−1 based on metal oxide mass was observed and the material showed good recovery from high rate cycling. The …

Herein, we show a facile surfactant-free synthetic platform for the synthesis of nanostructured vanadium pentoxide (V2O5) using reline as a green and eco-friendly deep eutectic solvent. This new approach overcomes the dependence of the current synthetic methods on shape directing agents such as surfactants with potential detrimental effects on the final applications. Excellent morphological control is achieved by simply varying the water ratio in the reaction leading to the selective formation of V2O5 3D microbeads, 2D nanosheets, and 1D randomly arranged nanofleece. Using electrospray ionization mass spectroscopy (ESI-MS), we demonstrate that alkyl amine based ionic species are formed during the reline/water solvothermal treatment and that these play a key role in the resulting material morphology with templating and exfoliating properties. This work enables fundamental understanding of the activity …

Lithium-ion batteries (LIBs) are considered as fascinating energy storage devices. However, scarcity and high cost of lithium resources lead to increasing research interest in next-generation batteries, such as potassium-ion batteries (KIBs), due to their similar electrochemical characteristics to LIBs and abundant potassium resources. However, significant problems in the search for suitable anode materials for KIBs continue to exist due to the hazards of potassium metal and unstable cycling performance of carbonaceous materials and metal oxides due to the large ionic size of potassium. Herein, we report on a well-ordered mesoporous niobium nitride/N-doped carbon hybrid (m-NbN/NC), verifying the potential of the transition metal nitride as the new K+ insertion host. The electrode delivers reversible capacities of 143 mA h g−1 at 0.01 A g−1 and 49 mA h g−1 at 1 A g−1. More impressively, a capacity retention of …

The practical use of lithium–sulfur battery (LSB) is impeded by the excessive growth of Li dendrite in the anode and the dissolution of soluble intermediates (shuttle effect) in the cathode. In spite of efforts to overcome these issues, separate research in the anode and cathode fields could not tackle the problems of both electrodes simultaneously, limiting the realization of LSB. Herein, a bifunctional separator is fabricated by coating morphology-controlled NbN on a Celgard separator. The large surface area (67 m2 g–1) and strong adsorptive surface of NbN effectively suppress the crossover of soluble intermediates to the anode side, and the captured sulfur species can be reactivated on the electrical conductive NbN surface to enhance the capacity. Most importantly, the improved mechanical strength and electrolyte wettability of separator by NbN functional layer suppress the growth of Li dendrite in anode …

With the ever-increasing demand for high energy density and low-cost energy storage devices, researchers have revitalized the field of alkali metal batteries. One of the emerging candidates are the sodium metal batteries (SMBs) as they have the merits of high theoretical capacity (1166 mA h g−1) and can be easily manufactured owing to the abundance of sodium resources. However, the uncontrollable dendrite growth on sodium metal, mainly attributed to its inhomogeneous and unstable solid–electrolyte interphase (SEI), has severely hindered the practical application of SMBs. In this review, we first summarize the critical challenges faced in the practical application of SMBs based on fundamental studies. We then discuss the recent approaches for designing an SEI layer on sodium metal anodes from two perspectives combined with feasible ideas, i.e., electrolyte modification and artificial interphase engineering …

Lithium metal batteries are considered “rough diamonds” in electrochemical energy storage systems. Li-metal anodes have the versatile advantages of high theoretical capacity, low density, and low reaction potential, making them feasible candidates for next-generation battery applications. However, unsolved problems, such as dendritic growths, high reactivity of Li-metal, low Coulombic efficiency, and safety hazards, still exist and hamper the improvement of cell performance and reliability. The use of functional separators is one of the technologies that can contribute to solving these problems. Recently, functional separators have been actively studied and developed. In this paper, we summarize trends in the research on separators and predict future prospects.

Lithium plating on conventional graphite anodes in lithium-ion batteries is typically considered an undesirable side reaction, a safety hazard or a degradation mechanism. However, lithium plating and stripping allow for efficient energy storage, and therefore various new porous anode designs with tailored surface coatings and electrolyte systems have been proposed to achieve reversible Li plating and stripping. Unfortunately, these material designs often rely on highly porous plating scaffolds with an overall lower volumetric energy and power density than conventional graphite anodes. Herein, a novel anode design is presented which leverages the good volumetric performance of industrial graphite anodes and further enhances their capacity by allowing for a reversible Li plating on their surface. The latter is achieve by conformally coating them with a nanoscale lithiophilic Si coating. As a result, excellent …