All-Solid-State Batteries with Extremely Low N/P Ratio Operating at Low Stack Pressure

Abstract

All-solid-state batteries (ASSBs) are emerging as promising candidates for next-generation energy storage systems. However, their practical implementation faces significant challenges, particularly their requirement for an impractically high stack pressure. This issue is especially critical in high-energy density systems with limited negative-to-positive electrode capacity ratios (N/P ratios), where uneven lithium (Li) stripping induces the formation of interfacial voids. This study addresses these challenges by introducing an anode with a novel structural design that operates effectively under practically viable conditions while significantly reducing the N/P ratio to less than one. The approach entails the integration of a lithiophilic magnesium (Mg) film beneath a thin layer of the silicon-graphite (SiGr) active materials. This structure facilitates the deposition of excess Li beneath the SiGr layer during overcharging, which enables stable cycling even at room temperature and at a low stack pressure of 3 MPa. By mitigating the poor contact that is characteristic of ASSBs with a low stack pressure, and simultaneously increasing the energy density by lowering the N/P ratio, the design significantly advances the key electrochemical properties of ASSBs.