Batteries & Supercaps最新文献

The determination of the intrinsic properties of solid active material candidates is essential for their performance optimization. However, macroscopic electrodes and related analytical techniques show challenges concerning the number of additional influencing parameters. We explore recessed microelectrodes (rME) as a platform that allows for a binder-free investigation of Prussian Blue analogues (PBA), a family of promising battery materials. The enhanced diffusion using microelectrochemical tools is indispensable to assess the intrinsic material performance, overcoming the limitation of cation diffusion from the electrolyte to the solid interface during (dis)charging cycles and allowing the investigation of limiting steps in the coupled ion-electron transfer process. The intrinsic electrochemical performance of PBAs was studied in a three-electrode configuration by means of cyclic voltammetry and galvanostatic (dis)charging in aqueous Na⁺-containing electrolyte. We extended the evaluation to the role of the electrolyte on the performance of cathodic and anodic processes of a Mn-based PBA. Ex-situ and operando chemical characterization were coupled to support the microelectrochemical results.

This study investigates the concealed effect of separator porosity on the electrochemical performance of lithium-ion batteries (LIBs) in thin and thick electrode configuration. The effect of the separator is expected to be more pronounced in cells with thin electrodes due to its high volumetric/resistance ratio within the cell. However, the electrochemical analyses show similar power performance regardless of the separator porosity in the thin electrode configuration. In contrast, for cells with thick electrodes, separator porosity significantly impacts the direct current-internal resistance (DC-IR) and the capacity retention at a high rate. This behavior is attributed to ion concentration gradients in the upper regions of thick electrodes, while Li⁺ transfer to lower regions is hampered as the electrode thickness increases. These findings suggest that the intrinsic properties of individual cell components, such as separator porosity, are highly dependent on the overall cell design. Moreover, while high-porosity separators enhance power performance, particularly in thick electrode configurations, they exhibit lower thermal stability and tensile strength. In conclusion, this study highlights the need for an integrated approach to optimizing separator characteristics, considering both electrochemical performance and safety trade-offs in LIBs.

Methyl viologen (MV) and its derivatives are emerging as promising candidates within the organic redox flow battery community due to their commendable reversibility and rapid reaction kinetics. However, experimental observations reveal the influence of solute concentration on the diffusion coefficient and the tendency of MV⁺ to form dimers or multimers, affecting electrolyte viscosity. Traditional characterization methods may not fully capture these properties. To explore concentration and state of charge effects on diffusion coefficient and viscosity, a kinetic Monte Carlo (kMC) model coupled with mean square displacement analysis is introduced. The kMC model offers a 3D simulation space with expandable periodic boundary conditions, enabling realistic ion movement. The mean square displacement (MSD) algorithm extracts diffusion coefficients, followed by the estimation of the electrolyte viscosity using the Stokes-Einstein equation. Validation with NaCl solutions precedes adaptation to simulate MV⁺⋅diffusion coefficients at 1.5 M with varying states of charge (SoC), aligning with experimental data. Simulation results indicate increased multimerization at higherSoCs. The diffusion coefficient of fully charged MV⁺⋅decreases with electrolyte concentration due to dimer and multimer formation. This modeling approach provides insights into MV⁺⋅behavior, crucial for organic redox flow battery development.

Ionic covalent organic frameworks (iCOFs) have garnered significant attention as potential single-ion conductive solid-state electrolytes, where researchers have made substantial efforts in designing iCOF-based composites, aiming to improve their intrinsic low conductivity. One successful case is to fill iCOF channels with lithium salts, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). However, the ion transport mechanisms in these composite electrolytes are still largely unknown, hindering their further improvement. Here molecular dynamics simulations were employed to systematically predict the ion diffusivity in iCOF (e. g., TpPa-SO₃Li COF)-LiTFSI composite electrolytes with varying LiTFSI compositions at different temperatures. A positive correlation was observed between Li⁺ diffusivity and LiTFSI:iCOF ratio, which was also verified by our experiments. Interestingly, the Li⁺ diffusion energy barrier obtained by the Arrhenius equation exhibited nearly no dependency on the LiTFSI concentration, indicating the importance of temperature-insensitive microstructural-related factors. Radial distribution functions revealed that with a higher LiTFSI proportion, the coordination number of SO₃⁻ decreases, while that of TFSI⁻ increases, suggesting a competition between these two species in the Li⁺ solvation shell. Furthermore, configurational entropy and bond orientational order parameter calculations examined the degree of disorder in the Li⁺ solvation structure. These results should improve our mechanistic understanding of iCOF-based electrolytes.

Olivine LiMn_xFe_1−xPO₄ (LMFP) cathodes are gaining attention as a promising alternative to LiFePO₄ (LFP) for lithium-ion batteries (LIBs), offering higher energy density while maintaining lower costs and improved safety compared to traditional layered oxide cathodes. However, their low electronic conductivity remains a challenge. One effective strategy to enhance electrode kinetics is incorporating carbon additives during fabrication. This study examines the role of conductive additive optimization in LiMn_0.7Fe_0.3PO₄ (LMFP73) electrodes and evaluates the impact of refining the electrode manufacturing to improve performance under practical conditions. Electrodes with 0.5 % single-walled carbon nanotubes (SWCNTs) dispersion demonstrated improved performance. Optimization of mixing protocol, solid content, and coating speed, significantly enhanced the electrode's microstructure, mechanical integrity, and electrochemical response, producing thick electrodes suitable for industrial use. Upscaling to Graphite|LMFP73 single-layer pouch (SLP) cells with 200 g m⁻² cathode loading resulted in 110 mAh g⁻¹ at C/2, retaining 93 % of the initial capacity after 100 cycles. This work provides practical process parameters to reduce the gap between academic and industrial perspectives in electrode performance assessment under realistic conditions, tackling challenges in performance improvement while taking into account high areal loadings, mechanical properties of the coatings, practical electrode balancing, and electrolyte amount in the cell fabrication process.

The Cover Feature illustrates the optimized structures for lithium adsorbed on pristine and defective graphdiyne (GDY) nanosheets. The upper part (left) of the picture shows a perfect layer decorated with lithium (green), to the right is a plot of the charge density difference, showing a uniform distribution and a charge transfer from the lithium at one vertex. The lower part presents the structure after introducing a carbon vacancy showing a distortion, charge transfer from Li atoms and an asymmetric charge density difference that moves to the three connecting carbon atoms (blue). More information can be found in the Research Article by A. Juan and co-workers (DOI: 10.1002/batt.202400514).

The Front Cover shows a fully automated sequential robotic experimental setup for the cell fabrication of stacked-type lithium–oxygen rechargeable batteries with a fabrication throughput of over 80 cells per day, which is ten times higher than conventional human-based experiments. The high alignment accuracy during the electrode stacking and electrolyte injection process results in improved battery performance and reproducibility. More information can be found in the Research Article by S. Matsuda and co-workers (DOI: 10.1002/batt.202400509).

The Cover Feature illustrates the advanced fabrication process and structure of flexible micro-supercapacitors (MSCs) with 3D interconnected graphene/carbon nanotube (CNT) composite electrodes. Combining flash lamp annealing (FLA) and laser ablation, this process transforms graphene oxide and CNT films into high-performance, interdigitated MSCs. The resulting devices deliver exceptional energy density, flexibility, and scalability, thus underscoring their potential for flexible electronics and miniaturized energy-storage applications. More information can be found in the Research Article by Y. Myung and T. Y. Kim (DOI: 10.1002/batt.202400557).

2D materials are emerging materials for energy storage and among these layered double hydroxides (LDHs) seem particularly promising due to their structure, easily adjustable composition, and cheapness. This study marks the first reported application of an LDH, specifically NiFe-NO₃ LDH, as conversion anode material in a sodium half-cell, to the best of our knowledge. Despite an initial loss in capacity, the material demonstrates notable stability, retains a high specific capacity even after 50 discharge/charge cycles (~500 mAh/g). The intricate reaction mechanism was explored using various ex-situ techniques such as DC magnetometry and FTIR, as well as in-operando X-ray Absorption Spectroscopy (XAS). The proposed Na-storage mechanism in NiFe-NO₃ LDH involves an initial irreversible “activation” during the first sodiation, characterized by a phase change reaction that leads to the formation of NiO_x and Fe₃O₄, followed by a reversible mechanism involving both intercalation and conversion in subsequent cycles.

We report on the physiochemical behaviour of membranes based on three different polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) block copolymers and an ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI)) and their use as solid-state electrolytes in supercapacitors. The nanostructured block copolymers form free standing membranes at high ionic liquid uptake with conductivities above 1 mS/cm at 25 °C, keeping ordered morphologies. We used small angle X-ray scattering (SAXS) to propose the correlation between domain spacing, the copolymer chain length (N) and the interaction parameter (χ_eff) in the block copolymers. We explored the potential of the electrolytes in two high voltage (3.0 V) device configurations, first using carbon nanotube (CNT) electrodes, with excellent electrical conductivity and high-rate capability exhibiting a power density of 5.7 KW/kg at 4 A/g, while devices based on high surface area activated carbon exhibited high energy density of 20.7 Wh/kg at 4 A/g. Overall, both devices deliver superior specific energy and power densities than that of commercial state-of-the-art supercapacitors, based on liquid electrolyte. Additionally, the CNT|Solid-state|CNT device displays higher power density compared to the AC|Solid-state|AC device, highlighting its better suitability for high power applications, while the AC|Solid-state|AC device, is better suited for energy density applications.