Design Principles for Alloy-Anode-Based Low-Stack-Pressure Solid-State Batteries

Solid-state batteries with Li alloy anodes offer enhanced safety and energy density. However, many studies still rely on high stack pressures, while low stack pressure operation is essential for practical application. This work establishes a general electro-chemo-mechanical framework that enables rational pairing of alloy anodes and solid electrolytes by predicting the critical stack pressure required for interfacial stability under practical operating conditions. Based on thermodynamic and mechanical factors, our findings identified three design principles for achieving low stack pressure: (1) applying highly conductive and mechanically compliant solid electrolytes; (2) using Li-rich and hard alloy anodes; and (3) optimizing external conditions through smooth interfaces, low applied current densities, and elevated temperatures. Experimental results demonstrate that the LiAl alloy paired with Li₆PS₅Cl electrolyte exhibits stable cycling performance and smooth interfacial morphology above the critical stack pressure, while poor performance with rough morphology has been observed below it. These findings provide key principles for achieving low stack pressure in solid-state batteries.