High Active Material Loading in All‐Solid‐State Battery Electrode via Particle Size Optimization

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. In this work, it is demonstrated 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.