Solid-state lithium garnet (LLZT) electrolytes display relatively high ionic conductivity, thermal stability, and compatibility with lithium metal, which makes them encouraging for the future of lithium-ion batteries. As with many other solid electrolytes, their main weakness is poor contact and high interfacial resistance with electrodes. The use of polymer gels as interlayers has been demonstrated to reduce this interface, improving cell stability and lifespan. In this study, immersion precipitation has been explored as a preparation method to create poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) polymer membranes. The resultant microstructure is highly porous and can uptake nearly 600% its weight in liquid electrolyte when forming a gel. Polymethyl methacrylate (PMMA) and lithium fluoride (LiF) are incorporated into the membranes and evaluated for their contributions to mechanical and electrochemical properties. Membranes containing LiF showed high stability up to 4.5 V vs Li/Li+ and were analyzed in cells of composition NMC/PVDF-HFP/LLZT/Li. Specific discharge capacities up to 174 mAh/g were achieved during early cycling and showed promise for future exploration and application in quasi-solid-state lithium-ion batteries.