Peter Müller-Buschbaum

A full series of variously lithiated graphite anodes material LixC6 (0<x<1) corresponding to a different state‐of‐charge (SOC) between 0 % and 100 % was collected from 18650‐type cylinder Li‐ion batteries, and the thermal structural behavior of these electrodes was mapped using ex situ high‐resolution X‐ray and neutron diffraction. Their structural behavior was analyzed over a broad temperature range. At high temperatures, a non‐reversible decomposition of the lithiated graphite anodes takes place, accompanied by a loss of intercalated lithium ions, forming novel phases such as LiF and Li2O strongly coupled to the degradation of the solid electrolyte interface (SEI). Complementary calorimetric measurements showed the strongly exothermic chemical reactions during the decomposition matching well to the collected diffraction data. Post mortem analysis applying scanning electron microscopy revealed …

Although the loss of Li inventory (LLI) is a common aging mechanism in Li-ion batteries, there are only few methods capable of comprehensive depth profiling within the bulk of the electrode to locate the residual Li. Two post-mortem analytical methods, which can be used to obtain quantified Li depth profiles to depths greater than 10 μm from the electrode surface are neutron depth profiling (NDP) and glow discharge optical emission spectroscopy (GD-OES). In this work, the validation of GD-OES using NDP by examining the Si/graphite anodes of cylindrical 21,700 cells is presented. One anode was in a pristine/fresh state, two anodes were aged to the state of health (SOH) 90% and 76% at 45 °C respectively, and suffered from heavy solid electrolyte interphase (SEI) growth, and the fourth anode was aged to SOH 60% at 0 °C and exhibited Li plating. It is demonstrated that Li plating leads to a faster sputter rate of …

Because of the detrimental effects of excessive exposure to solar ultraviolet radiation (UVR) on human skin health, wearable UVR detectors have attracted more and more attention. Inspired by the artwork “Tian-tsui hair pin with flora decoration” from the Palace Museum, a reversible and photochromic peony-shaped hairpin is designed to realize the visualized detection of solar UV radiation. It is prepared via electrospinning a mixed solution containing thermoplastic polyurethanes (TPUs) and Zn-MOF@WO3 onto microfiber nonwoven fabrics (MFNFs). Because of the enhanced UV responsive and photochromic capability from Zn-MOF@WO3 as well the excellent flexibility from TPUs and MFNFs, the obtained hairpin presents an excellent photoresponsive and wearable performance. When exposed to UV radiation from sunshine, the hairpin switches from white to light blue and finally to blue with radiation time. The …

Realization of multi-source energy harvesting with one single device would maximize power output. Thus, it is emerging as a promising strategy towards renewable energy generation and has attracted worldwide attention in the past decades. Capable of capturing mechanical energy that is ubiquitous in the ambient environment, triboelectric nanogenerator (TENG) has been considered a novel yet effective source towards next-generation energy harvesting. In this work, a flexible hybrid energy harvester (HEH) is developed via the rational integration of autonomous self-healing TENG and high bending-stable lead sulfide quantum dot (PbS QD) solar cell, enabling independent electricity generation by two different mechanisms. The single-electrode mode TENG component with self-healing is realized by a polydimethylsiloxane/Triton X-100 (PDMS/TX100) mixture as the dielectric layer and the shared gold (Au …

Converting PbI2 residues into low‐dimensional perovskites through post‐treatment with ammonium‐based large cations can passivate 3D perovskites, thus has emerged as an effective strategy to improve the performance of perovskite solar cells (PSCs). Herein, a dramatically improved efficiency is demonstrated for PSCs based on a two‐step‐processed FAPbI3 perovskite via post‐treatment with formamidinium (FA)‐based benzamidine hydrochloride (PFACl), outperforming the commonly used methylamine (MA)‐based benzylamine hydrochloride (PMACl). With an in‐depth exploration of the crystal structures and morphology changes of the FAPbI3 perovskite upon the PFACl post‐treatment, the preferential formation of 1D rather than 2D structures on the 3D perovskite film is identified. In contrast to the 2D counterpart, the more energetically favorable 1D structure enables a more effective elimination of PbI2 …

Halide perovskites, in the form of thin films and colloidal nanocrystals, have recently taken semiconductor optoelectronics research by storm, and have emerged as promising candidates for high‐performance solar cells, light‐emitting diodes (LEDs), lasers, photodetectors, and radiation detectors. The impressive optical and optoelectronic properties, along with the rapid increase in efficiencies of solar cells and LEDs, have greatly attracted researchers across many disciplines. However, most advances made so far in terms of preparation (colloidal nanocrystals and thin films), and the devices with highest efficiencies are based on Pb‐based halide perovskites, which have raised concerns over their commercialization due to the toxicity of Pb. This has triggered the search for lower‐toxicity Pb‐free halide perovskites and has led to significant progress in the last few years. In this roadmap review, researchers of different …

The compatibility of lithium metal with organic solvents is the most crucial for lithium metal batteries (LMBs). Even though ether solvents show excellent compatibility toward lithium metal, the reactivity of the ether solvents at elevated temperatures and high voltages hinders their utilization in lithium metal battery systems. In this study, a high‐temperature ether electrolyte is designed comprising lithium oxalyldifluoroborate (LiODFB), diethylene glycol dibutyl ether (DGDE), 3‐methoxypropionitrile (MPN), and fluorinated ethylene carbonate (FEC), which is abbreviated as MDF electrolyte. The presence of MPN in the electrolyte changes the solvation structure, thereby facilitating increased redox reactions of ODFB− and synergizing with FEC to build a robust solid electrolyte interface (SEI), effectively inhibiting lithium dendrites growth and solvent decomposition. Consequently, the MDF electrolyte exhibits not only long …

Utilizing intermolecular hydrogen‐bonding interactions stands for an effective approach in advancing the efficiency and stability of small‐molecule acceptors (SMAs) for polymer solar cells. Herein, we synthesized three SMAs (Qo1, Qo2, and Qo3) using indeno[1,2‐b]quinoxalin‐11‐one (Qox) as the electron‐deficient group, with the incorporation of a methylation strategy. Through crystallographic analysis, it is observed that two Qox‐based methylated acceptors (Qo2 and Qo3) exhibit multiple hydrogen bond‐assisted 3D network transport structures, in contrast to the 2D transport structure observed in gem‐dichlorinated counterpart (Qo4). Notably, Qo2 exhibits multiple and stronger hydrogen‐bonding interactions compared with Qo3. Consequently, PM6 : Qo2 device realizes the highest power conversion efficiency (PCE) of 18.4 %, surpassing the efficiencies of devices based on Qo1 (15.8 %), Qo3 (16.7 …

Polarized light is critical for a wide range of applications, but is usually generated by filtering unpolarized light, which leads to substantial energy losses and requires additional optics. Here we demonstrate the direct emission of linearly polarized light from light-emitting diodes made of CsPbI3 perovskite nanoplatelet superlattices. The use of solvents with different vapour pressures enables the self-assembly of the nanoplatelets with fine control over their orientation (either face-up or edge-up) and therefore their transition dipole moment. As a result of the highly uniform alignment of the nanoplatelets, as well as their strong quantum and dielectric confinement, large exciton fine-structure splitting is achieved at the film level, leading to pure red light-emitting diodes with linearly polarized electroluminescence exhibiting a high degree of polarization of 74.4% without any photonic structures. This work demonstrates the …

The LiCoO2 (LCO) cathode is foreseen for extensive commercial applications owing to its high specific capacity and stability. Therefore, there is considerable interest in further enhancing its specific capacity by increasing the charging voltage. However, single‐crystal LCO suffers from a significant capacity degradation when charged to 4.5 V due to the irreversible phase transition and unstable structure. Herein, an ultra‐small amount (0.5% wt. in the electrode) of multi‐functional PIM‐1 (a polymer with intrinsic microporosity) additive is utilized to prepare a kind of binder‐free electrode. PIM‐1 modulates the solvation structure of LiPF6 due to its unique structure, which helps to form a stable, robust, and inorganic‐rich cathod‐eelectrolyte interphase (CEI) film on the surface of LCO at a high voltage of 4.5 V. This reduces the irreversible phase transition of LCO, thereby enhancing the cyclic stability and improving the …

The colloidal layer formation on porous materials is a crucial step for printing and applying functional coatings, which can be used to fabricate anticounterfeiting paper. The deposition of colloidal layers and subsequent thermal treatment allows for modifying the hydrophilicity of the surface of a material. In the present work, wood-based colloidal inks are applied by spray deposition on spray-deposited porous cellulose nanofibrils (CNF) films. The surface modification by thermal annealing of the fabricated colloid-cellulose hybrid thin films is investigated in terms of layering and hydrophobicity. The polymer colloids in the inks are core–shell nanoparticles with different sizes and glass transition temperatures (Tg), thus enabling different and low thermal treatment temperatures. The ratio between the core polymers, poly(sobrerol methacrylate) (PSobMA), and poly(-butyl methacrylate) (PBMA) determines the Tg and hence …

Solution processing of hybrid perovskite semiconductors is a highly promising approach for the fabrication of cost‐effective electronic and optoelectronic devices. However, challenges with this approach lie in overcoming the controllability of the perovskite film morphology and the reproducibility of device efficiencies. Here, a facile and practical aging treatment (AT) strategy is reported to modulate the perovskite crystal growth to produce sufficiently high‐quality perovskite thin films with improved homogeneity and full‐coverage morphology. The resulting AT‐films exhibit fewer defects, faster charge carrier transfer/extraction, and suppressed non‐radiative recombination compared with reference. The AT‐devices achieve a noticeable improvement in the reproducibility, operational stability, and photovoltaic performance of devices, with the average efficiency increased by 16%. It also demonstrates the feasibility and …

Thermally induced degradation of organic photovoltaic devices hinders the commercialization of this emerging PV technology. Thus, a precise understanding of the origin of thermal device instability, as well as identifying strategies to circumvent degradation is of utmost importance. Here, it investigates thermally‐induced degradation of state‐of‐the‐art PBDB‐T‐2F (PM6):BTP (Y6) bulk heterojunction solar cells at different temperatures and reveal changes of their optical properties, photophysics, and morphology. The open‐circuit voltage and fill factor of thermally degraded devices are limited by dissociation and charge collection efficiency differences, while the short‐circuit current density is only slightly affected. Energy‐resolved electrochemical impedance spectroscopy measurements reveal that thermally degraded samples exhibit a higher energy barrier for the charge‐transfer state to charge‐separated state …

The instability of perovskite absorbers under various environmental stressors is the most significant obstacle to widespread commercialization of perovskite solar cells. Herein, we study the evolution of crystal structure and microstrain present in naked triple-cation mixed CsMAFA-based perovskite films under heat, UV, and visible light (1 Sun) conditions by grazing-incidence wide-angle X-ray scattering (GIWAXS). We find that the microstrain is gradient distributed along the surface normal of the films, decreasing from the upper surface to regions deeper within the film. Moreover, heat, UV, and visible light treatments do not interfere with the crystalline orientations within annealed polycrystalline films. However, when subjected to heat, the naked perovskite films exhibit a rapid component decomposition, induced by phase separation and ion migration. Conversely, under exposure to UV and 1 Sun light soaking, the …

Niobium pentoxides (Nb2O5) present great potential as next-generation anode candidates due to exceptional lithium-ion intercalation kinetics, considerably high capacity, and reasonable redox potential. Although four phases of Nb2O5 including hexagonal, orthorhombic, tetragonal, and monoclinic polymorphs show diverse characteristics in electrochemical performance, stable lifetime, high specific capacity, and fast intercalation properties cannot be delivered simultaneously with a single phase. Herein, this issue is addressed by generating a homogeneous mixture of orthorhombic and monoclinic crystals at the nanoscale. Reversible lithium-ion intercalation/deintercalation of the monoclinic phase is achieved, and exceptional lithium storage sites are created at the interface of the two phases. As a result, electrochemical features of stable lifetime from the orthorhombic phase and high specific performance from the …

Structural and spatial aspects of cell degradation are studied using a combination of diffraction-and imaging-based tools applying laboratory X-rays, neutron scattering and synchrotron radiation with electrochemical and thermal characterization. Experimental characterization is carried out on cylindrical cells of 21700-type, where four regimes of cell degradation are identified, which are supplemented by an increased cell resistance and surface temperature during cell operation. The amount of intercalated lithium in the fully charged anodes in the fresh and aged states is determined by ex situ X-ray diffraction radiography and in situ X-ray diffraction computed tomography. The qualitatively similar character of the results revealed a loss of active lithium along with the development of a complex heterogeneous distribution over the electrode stripe.

Perovskite bandgap tuning without quality loss makes perovskites unique among solar absorbers, offering promising avenues for tandem solar cells1,2. However, minimizing the voltage loss when their bandgap is increased to above 1.90 eV for triple-junction tandem use is challenging3-5. We present a novel pseudohalide, cyanate (OCN-), with a comparable effective ionic radius (1.97 Å) to bromide (1.95 Å) as a bromide substitute. Electron microscopy and X-ray scattering confirm OCN incorporation into the perovskite lattice. This contributes to significant lattice distortion, ranging from 90.5° to 96.5°, a uniform iodide/bromide distribution and consistent microstrain. Due to these effects, OCN-based perovskite exhibits an enhanced defect formation energy and significantly decreased nonradiative recombination. We achieved an inverted perovskite (1.93 eV) single-junction device with an open-circuit voltage (VOC) of …

Due to the poor UV protection capability, natural silk fabrics not only suffer from easy damage by sunshine but also induce possible sunburn in the human body. Efficient azobenzene isomerization and enhanced UV shielding are realized by replacing the natural silk with natural protein silk fibroin (SF) and electrospinning together with light-responsive copolymer P(MEO2-co-OEG300-co-AHMA). Compared to a solution cast film, the absorption peak intensity at 355 nm is 60 % higher in UV–Vis spectra of the electropsun SF/P(MEO2-co-OEG300-co-AHMA) fabrics. This improvement is related to the highly oriented chains, inducing more space and higher efficiency for azobenzene isomerization. Only exposure to visible light for 20 min, the absorption peak corresponding to the trans- state at 355 nm recovers to 92.5 % in the electrospun fabrics, which is 100 % faster than that in the solution cast film (50 min). It is …

The improvement in the efficiency of inverted perovskite solar cells (PSCs) is significantly limited by undesirable contact at the NiOX/perovskite interface. In this study, a novel microstructure‐control technology is proposed for fabrication of porous NiOX films using Pluronic P123 as the structure‐directing agent and acetylacetone (AcAc) as the coordination agent. The synthesized porous NiOX films enhanced the hole extraction efficiency and reduced recombination defects at the NiOX/perovskite interface. Consequently, without any modification, the power conversion efficiency (PCE) of the PSC with MAPbI3 as the absorber layer improved from 16.50% to 19.08%. Moreover, the PCE of the device composed of perovskite Cs0.05(MA0.15FA0.85)0.95Pb(I0.85Br0.15)3 improved from 17.49% to 21.42%. Furthermore, the application of the fabricated porous NiOX on fluorine‐doped tin oxide (FTO) substrates enabled the …

Tin perovskite solar cells (PSCs) are considered promising candidates to promote lead‐free perovskite photovoltaics. However, their power conversion efficiency (PCE) is limited by the easy oxidation of Sn2+ and low quality of tin perovskite film. Herein, an ultra‐thin 1‐carboxymethyl‐3‐methylimidazolium chloride (ImAcCl) layer is used to modify the buried interface in tin PSCs, which can induce multifunctional improvements and remarkably enhance the PCE. The carboxylate group (CO) and the hydrogen bond donor (NH) in ImAcCl can interact with tin perovskites, thus significantly suppressing the oxidation of Sn2+ and reducing the trap density in perovskite films. The interfacial roughness is reduced, which contributes to a high‐quality tin perovskite film with increased crystallinity and compactness. In addition, the buried interface modification can modulate the crystal dimensionality, favoring the formation of …