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The interfacial instability between a thiophosphate solid electrolyte and oxide cathodes results in rapid capacity fade and has driven the need for cathode coatings. In this work, the stability, evolution, and performance of uncoated, Li2ZrO3‐coated, and Li3B11O18‐coated LiNi0.5Co0.2Mn0.3O2 cathodes are compared using first‐principles computations and electron microscopy characterization. Li3B11O18 is identified as a superior coating that exhibits excellent oxidation/chemical stability, leading to substantially improved performance over cells with Li2ZrO3‐coated or uncoated cathodes. The chemical and structural origin of the different performance is interpreted using different microscopy techniques which enable the direct observation of the phase decomposition of the Li2ZrO3 coating. It is observed that Li is already extracted from the Li2ZrO3 in the first charge, leading to the formation of ZrO2 nanocrystallites with loss of protection of the cathode. After 50 cycles separated (Co, Ni)‐sulfides and Mn‐sulfides can be observed within the Li2ZrO3‐coated material. This work illustrates the severity of the interfacial reactions between a thiophosphate electrolyte and oxide cathode and shows the importance of using coating materials that are absolutely stable at high voltage. [ABSTRACT FROM AUTHOR]

Low active material loading in the composite electrode of all‐solid‐state batteries (SSBs) is one of the main reasons for the low energy density in current SSBs. In this work, it is demonstrated with both modeling and experiments that in the regime of high cathode loading, the utilization of cathode material in the solid‐state composite is highly dependent on the particle size ratio of the cathode to the solid‐state conductor. The modeling, confirmed by experimental data, shows that higher cathode loading and therefore an increased energy density can be achieved by increasing the ratio of the cathode to conductor particle size. These results are consistent with ionic percolation being the limiting factor in cold‐pressed solid‐state cathode materials and provide specific guidelines on how to improve the energy density of composite cathodes for solid‐state batteries. By reducing solid electrolyte particle size and increasing the cathode active material particle size, over 50 vol% cathode active material loading with high cathode utilization is able to be experimentally achieved, demonstrating that a commercially‐relevant, energy‐dense cathode composite is achievable through simple mixing and pressing method. [ABSTRACT FROM AUTHOR]

All-Solid-State Batteries: High Active Material Loading in All-Solid-State Battery Electrode via Particle Size Optimization (Adv. In article number 1902881, Gerbrand Ceder and co-workers demonstrate that the active material loading in all-solid-state batteries is largely controlled by the active material and solid electrolyte particle size ratio. A generalized guideline is provided for increasing active material loading via particle size optimization, and a composite cathode with >50 vol% active material loading is experimentally demonstrated. [Extracted from the article]