Plasma optimized Li7La3Zr2O12 with vertically aligned ion diffusion pathways in composite polymer electrolyte for stable solid-state lithium metal batteries

Composite solid-state electrolytes (CSSEs) are promising for high-energy–density solid-state lithium metal batteries for the integrated merits of high ionic conductivity of inorganic fillers and intimate interfical contact introduced by soft polymeric matrix. However, the Li+ diffusion in the garnet based CSSEs is still unsatisfactory due to the non-conducting Li2CO3 layer on surface of the Li7La3Zr2O12 (LLZO) and the incontinuous ion diffusion pathways caused by the random distribution. Here we report a CSSE composed of Li2CO3-free LLZO nanoparticles by plasma treatment with vertically aligned structure (labelled as PLLZOV) in PVDF-HFP/PEO/LiTFSI (PPL) matrix. The removal of Li2CO3 along with the vertical alignment of LLZO enables the CSSE with more effective Li+ diffusion, delivering a higher ionic conductivity. Moreover, benefiting from the robust polymer matrix, the CSSE possesses excellent mechanical strength with good flexbility, making it effective in suppressing lithium dendrite growth and realizing good interfacial contact. Furthermore, the PLLZOV/PPL exhibits stable potential window up to 5.0 V vs Li/Li+. As a result, the solid-state lithium metal batteries assembled with PLLZOV/PPL achieve high capacities of 128.4 mA h·g−1 at 0.5C and 109.7 mA h·g−1 at 1.0C with LiFePO4 cathode and good cycle stability at 50 °C. This composite electrolyte engineering strategy provides a facile method for the preparation of high-performance CSSE and shows great application potential in solid-state lithium metal batteries.