Lithium-Rich Anti-perovskite Li₂OHBr-Based Polymer Electrolytes Enabling an Improved Interfacial Stability with a Three-Dimensional-Structured Lithium Metal Anode in All-Solid-State Batteries

All-solid-state lithium-metal batteries, with their high energy density and high-level safety, are promising next-generation energy storage devices. Their current performance is however compromised by lithium dendrite formation. Although using 3D-structured metal-based electrode materials as hosts to store lithium metal has the potential to suppress the lithium dendrite growth by providing a high surface area with lithiophilic sites, their rigid and ragged interface with solid-state electrolytes is detrimental to the battery performance. Herein, we show that Li2OHBr-containing poly(ethylene oxide) (PEO) polymer electrolytes can be used as a flexible solid-state electrolyte to mitigate the interfacial issues of 3D-structured metal-based electrodes and suppress the lithium dendrite formation. The presence of Li2OHBr in a PEO matrix can simultaneously improve the mechanical strength and lithium ion conductivity of the polymer electrolyte. It is confirmed that Li2OHBr does not only induce the PEO transformation of a crystalline phase to an amorphous phase but also serves as an anti-perovskite superionic conductor providing additional lithium ion transport pathways and hence improves the lithium ion conductivity. The good interfacial contact and high lithium ion conductivity provide sufficient lithium deposition sites and uniform lithium ion flux to regulate the lithium deposition without the formation of lithium dendrites. Consequently, the Li2OHBr-containing PEO polymer electrolyte in a lithium-metal battery with a 3D-structured lithium/copper mesh composite anode is able to improve the cycle stability and rate performance. The results of this study provide the experimental proof of the beneficial effects of the Li2OHBr-containing PEO polymer electrolyte on the 3D-structured lithium metal anode.