Failure mechanisms investigation of ultra-thin composite polymer electrolyte-based solid-state lithium metal batteries

Abstract

Solid-state lithium metal batteries (SSLBs) using solid polymer electrolytes (SPEs) still suffer from the risk of lithium dendrites, and the filling of porous framework can effectively alleviate the short-circuit problem. However, the interfacial failure mechanism of SPE with lithium metal anode and the action of porous framework filler are not fully understood. Herein, thin polyethylene (PE) separator is used as filler of poly(ethylene oxide) (PEO) to prepare ultra-thin composite polymer electrolyte (PE-CPE). Although the PE framework can greatly extend the cycling life of PE-CPE with lithium metal anode, the focused ion beam-scanning electron microscopy (FIB-SEM) results reveal that the uneven deposition and pulverization of lithium at the Li/PEO interface. Nanoparticulate lithium dendrites grow through the SPE resulting in a short-circuit, while the PE framework with small pores restricts the ingress of lithium nanoparticles through physical barrier. This work provides the growth mode of lithium dendrites in PEO-based SPE systems, and simultaneously demonstrates the role of porous framework to block lithium dendrites in SSLBs.