Interface engineering on a Li metal anode for an electro-chemo-mechanically stable anodic interface in all-solid-state batteries

Despite the extensive interest in Li metal-based all-solid-state batteries (ASSBs) with sulfide solid electrolytes (SEs), the physically, chemically, and electrochemically unstable anodic interface has impeded the achievement of performance retention at the commercial level for this system. Herein, we report Li metal anodes protected from interfacial instability by an intervening layer composed of a Li–In alloy and LiI in an Li2S–P2S5 glass ceramic matrix synthesized by a solution process. At a unique precursor composition of Li2S:P2S5:InI3, complexation of the precursor for complete dissolution in the solvent is achieved, producing a homogeneous precursor solution for coating. The elaborate solution synthesis enables the formation of a dense and void-free thin protective interlayer for the complete separation of Li metal and SE. The chemical affinity between the Li2S–P2S5 glass ceramic matrix and Li3PS4 SE adds physical stability to the anodic interface. The combined physical stability, the chemical inertness of Li–In and LiI against Li metal, and fast Li migration through the Li–In alloy, LiI, and Li2S–P2S5 glass ceramic matrix give the anodic interface electro-chemo-mechanical stability. The full ASSB paired with the LiNi0.8Co0.1Mn0.1O2 cathode exhibits notably superior stability, particularly at a high current, proving the suppression of dendritic growth of Li by the protective layer.