Multilayer Porous Membranes for Lithium Polymer Batteries Based on In Situ Cross-Linked Solid Polymer Electrolytes

Solid polymer electrolytes (SPEs) are considered a promising option for solid-state lithium batteries; however, decreasing the interface resistance with the cathode or anode, achieving sufficient mechanical strength for roll-to-roll processes, and enhancing the ionic conductivity remain challenging. One promising strategy is in situ polymerization, which involves placing a supporting porous membrane between the anode and cathode, wetting a polymer electrolyte precursor, and thermally curing it for solidification. Herein, a multilayer porous membrane is presented, which is suitable for lithium polymer batteries based on in situ cross-linked SPEs. The pore size, wettability, stability, and mechanical strength of the membranes are mainly considered to demonstrate the characteristics of SPEs. Cycling tests and cyclic voltammetry results indicate that polypropylene is a suitable base material. The ionic conductivity and wettability of SPEs are improved by controlling their pore size and surface properties. The optimized multilayer porous membrane is employed in lithium polymer cells, exhibiting excellent cycle performance over 100 cycles, maintaining a stable electrochemical performance even upon cutting and folding, and demonstrating an energy density as high as 300 Wh kg–1.