Balancing Partial Ionic and Electronic Transport for Optimized Cathode Utilization of High‐Voltage LiMn 2 O 4 /Li 3 InCl 6 Solid‐State Batteries

Abstract Their suggested stability towards high‐voltage cathode materials makes halide‐based solid electrolytes currently an interesting class of ionic conductors for solid‐state batteries. Especially the LiMn 2 O 4 spinel cathode active material is of interest due to its slightly higher nominal voltage and more resilience to overcharging compared to LiCoO 2 and LiNi x Mn y Co z O 2 cathodes. Typically, a standard ratio of active material to solid electrolyte is used in composites for solid‐state batteries. However, for ideal transport properties, and thus to achieve balanced and optimal partial‐conductivities, this ratio needs to be re‐optimized each time the material basis is changed. In this work, we show transport in the composite measured through both DC polarization as well as transmission line modeling of the impedance spectra. By balancing the partial transport parameters of the composite, an optimum capacity of the solid‐state batteries is achieved. This work shows characterization and optimization of transport is required for unlocking the full potential of solid‐state batteries.