Bilayer Halide Electrolyte Design Enabling Excellent Interface Stability between a Li-Metal Anode and a Halide Solid Electrolyte

Halide solid electrolytes (SEs) with high ionic conductivity and good chemical stability are promising materials for all-solid-state Li-metal batteries (ASS-LMBs). However, the poor interfacial compatibility with Li metal has impeded their extensive applications in ASS-LMBs. To address this problem, here, we propose a novel bilayer halide interface Li3YCl6(LYC)/Li3OCl(LOC)/Li. The stability and Li-ion transport of LYC/LOC/Li are systematically studied by employing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Our results show that the stability of the LYC/Li interface can be greatly improved after LOC coating on LYC. In particular, we found that the diffusion of Li-ions is predominant along the boundary of the LYC/LOC/Li, and the conductivity and activation energy of Li-ions at the interface are 160 mS/cm (300 K) and 0.146 eV, respectively, which are superior to the counterparts of bulk LYC. Our results provide theoretical guidance for enabling halide compatibility with Li metal.