A Sandwich Structure Composite Solid Electrolyte with Enhanced Interface Stability and Electrochemical Properties For Solid-state Lithium Batteries

Poor interfacial combination between the solid electrolyte and the lithium anode is a bottleneck for the application of solid-state lithium batteries. Here, a flexible polymer buffer layer of poly (propylene carbonate) (PPC)- Li7La3Zr2O12(LLZO) was introduced to the surface of polyvinylidene fluoride (PVDF)-LLZO solid electrolyte to form a sandwich composite structure, boosting the interfacial contact and stability between electrodes and electrolyte by in situ gelation of the PPC buffer layer. The layered structure composite solid electrolyte (LSCE) membrane has an electrochemical stability window of 4.55 V, and the ion conductivity is 1.25 × 10−4 S·cm−1. Due to the formation of a good interface contact and good stability against lithium and inhibition of lithium dendrite, the assembled NCM622/LSCE/Li solid-state battery has an initial specific capacity of 152.7 mAh·g−1 at a current density of 0.5 C, and the discharge specific capacity remains 106.9 mAh·g−1 after 200 cycles. At 1 C, the initial discharge specific capacity of the battery reaches 149.8 mAh·g−1, and remains 98 mAh·g−1 after 200 cycles. This layered structure composite electrolyte membrane shows good potential for use in high-performance solid-state lithium batteries.