Stabilizing the Bilateral\nInterfaces by a PVDF-Based\nDouble-Layer Solid Composite Electrolyte with a Relieved Dehydrofluorination\nEffect for Solid-State Lithium Metal Batteries

The dehydrofluorination effect of poly(vinylidene fluoride)\n(PVDF)\ninduced by ceramic fillers with an alkaline surface compromises the\ncomprehensive properties of the solid composite electrolyte (SCE)\nand leads to the deficient performance of the solid-state lithium\nmetal batteries (SLMBs). In this work, a unique PVDF-based double-layer\nsolid electrolyte was fabricated, which consisted of a Li<sub>6.4</sub>La<sub>3</sub>Zr<sub>1.4</sub>Ta<sub>0.6</sub>O<sub>12</sub> (LLZTO)-filled\nSCE with poly(acrylic acid) (PAA) as an alkalinity-scavenging agent\nin contact with the Li anode, and another SCE with lithium difluoro(oxalato)borate\n(LiDFOB) as a film-formation additive facing the cathode. It is found\nthat a moderate amount of PAA relieves the dehydrofluorination degree\nof the PVDF matrix and improves the Li plating/stripping reversibility,\nand the addition of LiDFOB is involved in the formation of a stable\npassivation film on the cathode. Consequently, the resultant double-layer\nSCE holds favorable overall properties, especially being well-compatible\nwith both electrodes, endowing the SLMBs with superior cycle and rate\nperformance at room temperature.