Stable lithium metal anode enabled by a polymeric interlayer with high salt concentration for solid-state batteries

The realization of lithium (Li) metal batteries, generally hindered by the high reactivity of Li metal with liquid electrolytes and the formation of Li dendrites, can be facilitated using solid electrolytes (SEs). Among the various types of SEs, succinonitrile (SN)-based SEs have attracted considerable attention owing to their high ionic conductivities at room temperature and oxidative stabilities at high voltages. However, the use of SN-based SEs in solid-state Li metal batteries (SSLMBs) is limited by severe side reactions (i.e., the polymerization of nitrile groups in SN catalyzed by Li metal). To overcome this problem, we propose a strategy to stabilize the interface between the Li anode and SN-based SE via a polymeric interlayer with a high salt concentration. The high salt concentration polymer (HSCP) interlayer inhibits the side reactions of SN with Li metal by blocking direct contact between them while also promoting the formation of a LiF-rich solid-electrolyte interphase (SEI), thereby mitigating the growth of Li dendrites during repeated charge–discharge cycling. The SSLMB cell assembled with the HSCP interlayer and high-voltage LiNi0.8Co0.1Mn0.1O2 cathode shows enhanced cycling performance compared to the cell with bare Li, demonstrating the beneficial role of the HSCP interlayer in stabilizing the Li/SN-based SE interface. Hence, this study provides an essential understanding of the design and construction of stable Li metal anodes for high-performance and long-cycling SSLMBs.