PEO-Based Solid Polymer Electrolyte with MOF-Modified Melamine–Formaldehyde Resin for Solid-State Lithium Batteries

Solid polymer electrolytes (SPEs) are promising solutions to address insufficient energy density along with the safety risks brought by liquid electrolytes in commercial lithium-ion batteries. Nevertheless, SPEs are still limited by low room-temperature ionic conductivity and weak mechanical properties, which greatly restrict their practical application. In this work, a poly(ethylene oxide) (PEO)-based SPE composed of rigid substrates was proposed, which showcased a high Young’s modulus of 3.38 MPa. Meanwhile, with the inorganic MOF filler and organic succinonitrile (SN) plasticizer, the Z@MEL/PEO-SN SPE demonstrated a high ionic conductivity of 5.5 × 10–5 S·cm–1 and lithium transference number of 0.46 at 25 °C. The Li|Z@MEL/PEO-SN|Li symmetric cell could cycle stably for over 2000 h at a current density of 0.025 mA·cm–2 at ambient temperature. The Li|Z@MEL/PEO-SN|LiFePO4 full cell maintained a capacity retention of 94.2% after 100 cycles at room temperature at 0.2 C. These results suggest that this SPE is a promising candidate for the next generation of solid-state lithium-ion batteries with a high energy density and improved safety.