A deformable dual-layer interphase for high-performance Li10GeP2S12-based solid-state Li metal batteries

Sulfide-based solid-state Li metal batteries show tremendous potential to deliver high energy density. However, the extremely unstable Li/sulfide interface involving dendrites and electrolyte decomposition is always a tough nut to crack. Herein, a gel polymer interlayer which originates from the polymerization of 1,3-dioxolan initiated by lithium difluoro(oxalato)borate is coated on anode to solve the challenge in Li10GeP2S12-based batteries. Benefitting from the proper lithium difluorophosphate (LiPO2F2) in the interlayer, more polymeric but fewer inorganic components are generated on Li to prompt a deformable solid electrolyte interphase (SEI) with a dual layer structure that the upper layer is rich in polymer to endow the SEI with elasticity and the bottom layer is full of inorganic species to restrain Li dendrites. Moreover, the seamless contact at the Li/Li10GeP2S12 interface is achieved to homogenize the Li-ion flux and the continuous decomposition of Li10GeP2S12 is restrained. Impressively, the symmetric cell with the coated Li demonstrates an ultra-stable cycling for 500 h at 0.5 mA cm(-2)/0.5 mAh cm(-2), and the modified Li-S battery also exhibits an outstanding cycling stability. This work provides a rational design for the next-generation solid-state batteries with a stable anode-sulfide electrolyte interface.