In situ polymerization infiltrated three-dimensional garnet-based framework for quasi-solid lithium metal batteries

Solid-state lithium metal batteries (LMBs) using nonflammable solid electrolytes (SEs) are considered to be the new generation of energy storage devices with high energy density and good safety. However, many challenges, such as insufficient room-temperature ionic conductivity of SEs and tremendous electrode-electrolyte interfacial impedance, hinder the commercialization of solid-state LMBs. Here, we reported a novel composite solid electrolyte (CSE), consisting of a three-dimensional (3D) Li 6.25 Ga 0.25 La 3 Zr 2 O 12 (LLZO) nanoparticle-based framework and filled tripropylene gycol diacrylate (TPGDA)-based gel electrolytes, in which the gel electrolytes are prepared by in situ polymerization of the TPGDA monomer in the condition of liquid electrolyte . Owing to the high content of LLZO powder and PVDF binder, the nonflammable CSE shows superior thermal stability and outstanding mechanical property. Moreover, the CSE exhibits high room-temperature ionic conductivity (1.66 × 10 −3  S⋅cm −1 ) due to the large amount of liquid electrolyte loaded in the 3D framework. Besides, in-situ gel electrolytes facilitate the interfacial contact between electrolyte and lithium anode. Therefore, the LiFePO 4 /CSE/Li cell exhibits excellent cycling stability at room temperature , delivering a capacity retention ratio of 86.5% after 350 cycles at 1 C. This work can provide guidance in designing CSEs for high-performance lithium metal batteries.