Double-layer solid-state electrolyte enables compatible interfaces for high-performance lithium metal batteries

Solid-state lithium metal batteries are promising next-generation batteries for both micro-scale integrated electronic devices and macro-scale electric vehicles.However,electrochemical incompatibility between electrolyte and electrodes causes continuous performance degradation.Here,we report a unique design of a double-layer composite solid-state electrolyte(D-CSE),where each layer,composed of both polymer and ceramics,is electrochemically compatible with its contacting electrode(Li anode or LiCoO_(2)cathode).The D-CSE has a small thickness(50μm),high thermal stability(up to 160℃ without noticeable deformation),and good flexibility even at a high ceramics content(66.7 wt%).Large-area selfstanding film can be obtained by a facile coating route.The electrolyte/electrode interface can be further enhanced via forming a soft interface by in-situ polymerization.Quasi-solid-state Li|D-CSE|LiCoO_(2)coin cells with the cathode-supported D-CSE can deliver a high initial discharge capacity of 134 mAh g^(-1) and a high capacity retention of 83%after 200 cycles at 0.5 C and 60℃.Quasi-solid-state Li|D-CSE|LiCoO_(2)pouch cells(designed capacity 8.6 mAh)with the self-standing D-CSE have a high retention of80%after 180 cycles at 2 mA charge and 4 mA discharge.At a high cathode loading(19.1 mg cm^(-2)),the Li|D-CSE|LiCoO_(2)pouch cell still can be stably cycled,and can withstand abuse tests of folding,cutting and nail penetration,indicating practical applications of the D-CSE.