A dendrite-suppressed flexible polymer-in-ceramic electrolyte membrane for advanced lithium batteries

Lithium-ion batteries (LIBs) using solid-state electrolytes (SSEs) can improve safety and energy density comparable with the liquid electrolytes (LE)-based counterparts. Especially, employing garnet-type SSEs to prepare solid-state LIBs are promising to achieve high-energy cells. However, the unbending and brittle issues of the inorganic SSE films are not suitable to fabricate flexible and stretchable energy storage devices. Here, We find that introducing specific polymer (30 wt%) into Li6.75La3Zr1.75Ta0.25O12 (LLZTO) can strongly increase the strength of the composite polymer-in-inorganic electrolyte (CIE) film. Both in-situ and ex-situ characterizations demonstrate that CIE delivers an excellent ability to suppress the growth of Li dendrites due to the close packing of LLZTO and effective filled grain boundaries and voids inside the CIE film by the polymer. The CIE inherits impressive electrochemical performance from LLZTO. As a result, the assembled LiFePO4 (LFP)/CIE/Li cell delivers better cell performance than LFP/LE-separator/Li cell at ambient temperature (AT). The assembled high-voltage cathode (Li1.2Mn0.6Ni0.2O2, 4.8 V)/CIE/Li cell also displays an excellent cell performance at AT. The present study offers new insights into exploring of flexible polymer-in-ceramic electrolytes for high-voltage LIBs with improved safety and energy density.