Impact of conducting agents on sulfide and halide electrolytes in disordered rocksalt cathode-based all-solid-state batteries

Abstract

All-solid-state battery (ASSB) systems have attracted significant attention due to their high energy density and safety compared with conventional batteries. Moreover, the application of Mn-based cation-disordered rock-salt (DRX) that possesses cost-effectiveness and high energy density on the ASSB system as a cathode is expected to be the superior next-generation battery system. However, DRX cathodes require high carbon contents due to their low electronic conductivity, leading to challenges in introducing them in ASSB systems, as the high carbon levels can cause electrolyte decomposition which potentially affects overall electrochemical performance. In this work, we applied Mn-based DRX cathodes to ASSB systems within a voltage range of 1.5–4.8 V and evaluated the suitability of cathode composites using halide and sulfide electrolytes as catholytes, respectively. The experimental results showed that the high carbon contents induced side reactions with the argyrodite, resulting in electrochemical degradation such as the drop of initial discharge voltage and the capacity fading. Meanwhile, cathode composites using a halide electrolyte exhibited relatively enhanced electrochemical performance due to its high oxidation stability regardless of the high amount of carbon contents. Consequently, the electrochemical reactions of the electrolyte, influenced by the content of conductive additives and the type of electrolyte, had a great impact on the performance of ASSB systems. This study provides a deep understanding of the interplaying among solid electrolytes, cathodes, and conductive additives and offers an important foundation for future research and development in ASSB systems.