UC San Diego

All-solid-state batteries using sulfur-based positive electrodes (cathodes) offer a cost-effective route to achieve high specific energy. However, low active material utilization and cycle life hinder performance. Here, we demonstrate a positive electrode design that employs sulfide solid-state electrolytes, where a high energy synthesis approach forms a metastable and ionically conductive interphase on the active material surface. This interphase facilitates high active material utilization and contributes capacity with cycling. We also show that tailoring active material particle sizes to the micron-scale improves rate performance and cycling stability. Structural analysis reveals that the substantial volume change of sulfur-based positive electrodes during operation can partially offset that of the negative electrodes, thereby mitigating internal mechanical stress. The combined design principles enable sulfur areal capacities up to 11 mAh cm-2 while maintaining stable cycling at 25 °C. We further demonstrate several specific-energy-focused cell architectures, particularly a Li2S anode-free pouch cell that operates under “low stack pressure” of 10 MPa. This work outlines practical design strategies for constructing high-specific-energy all-solid-state batteries for a broad range of emerging applications.