Lithium-Metal All-Solid-State Batteries Enabled by Polymer-Coated Halide Solid Electrolytes

Abstract

Halide solid electrolytes (HSEs) hold great promise for next-generation all-solid-state batteries (ASSBs); however, their application in practical devices is significantly hindered by the poor air and chemical stabilities, and reactivities at the lithium-metal anode interface. In this study, we present a methodology involving the modification of HSEs with an ionically conductive and electronically insulating polymer composite, leading to enhanced stability against lithium metal and stable cycling of ASSB cells. The concept is exemplified through the fabrication of a poly(methyl methacrylate) (PMMA) modified Li 3 YCl 6 (LYC) solid electrolyte (LYC_PMMA). Li symmetric cells employing LYC_PMMA exhibited stable lithium plating/stripping performance for well over 1400 cycles. In ASSB cells comprising an uncoated LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NMC811) cathode and a lithium metal anode, a discharge capacity of approximately 125 mAh/g was achieved at 1C cycling, with a coulombic efficiency of over 99.5% and a capacity retention of 99% over 100 cycles at RT. The polymer coating not only mitigates degradation reactions at the lithium metal anode interface, it also enables cell cycling under a reduced external pressure and imparts air stability, thereby enhancing processibility and manufacturability. This investigation introduces a facile and scalable approach for stabilizing halide electrolytes against lithium metal, offering a viable route to high-energy and cost-effective ASSB technologies.