Highly conductive and durable metal oxide particles as cathode composite layer additives for carbon-free all-solid-state batteries

Abstract

All-solid-state batteries (ASSBs) are attracting considerable attention for use in altering conventional Li-ion batteries, owing to their high energy density and safety. However, sulfide-based solid electrolytes suffer from having a narrow electrochemical stability window and consequent side reactions with high-Ni layered cathode materials and carbon-based conductive carbon agents at high voltages, underscoring the need for a stable alternative to existing carbon agent. This causes interfacial degradation and deteriorates the cycling performance. This study introduces a highly conductive and durable cathode-framework-stabilizing additive employing black WO3-x particles for obtaining high-performance carbon-free sulfide-based ASSBs. Using black WO3-x as cathode composite layer additive stabilized the cathode/electrolyte interface and provided both electronic and ionic conductivity in the cathode layer. In addition, the cathode composite layer with black WO3-x improved the electrochemical performance and cycle stability in ASSB cells without a carbon agent. These findings demonstrate that simply incorporating highly conductive and durable metal oxides into cathode composite layer additives can improve the cycling stability of ASSBs. © 2025 Elsevier B.V.