Tailored Cathode Composite Microstructure Enables Long Cycle Life at Low Pressure for All-Solid-State Batteries

The practical application of all-solid-state batteries (ASSBs) requires reliable operation at low pressures, which remains a significant challenge. In this work, we examine the role of a cathode composite microstructure composed of solid-state electrolyte (SSE) with different particle sizes. A composite made of LiNi0.8Co0.1Mn0.1O2 (NCM811) and fine-particle Li6PS5Cl (LPSC) shows a more uniform distribution of SSE on the surface of NCM811 particles, ensuring intimate contact. Moreover, the composite features reduced tortuosity, which enhances Li ion conduction. These microstructural advantages result in significantly reduced charge transfer resistance, helping to suppress mechanical distortion and electrochemical degradation during cycling under low-pressure conditions. As a result, the fine-LPSC cathode composite exhibits enhanced cycling stability at a moderate stack pressure of 2 MPa, outperforming its coarse-LPSC counterpart. Our finding confirms the important role of microstructure design in enabling high-performance ASSBs operating under low-pressure conditions.