Reinforced flexible solid-state electrolyte membrane by polyurethane polymer of intrinsic microporosity for high-energy-density lithium metal battery

Poly (ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are restricted in commercial applications due to the low ionic conductivity at ambient temperature and fragile mechanical properties. Polyurethanes (PUs) are unique materials coupled with superior rigidity and flexibility. Herein, we designed a novel polyurethane polymer of intrinsic microporosity (PPU), which was incorporated with PEO-based polymer electrolyte to prepare composite polymer electrolyte (CPE). The physicochemical and electrochemical properties of CPE membranes were explored. The high ionic conductivity (1.82 × 10−3 S cm−1 at 50 °C) and superior interfacial stability with the lithium anode was obtained. Furthermore, the rate performances and the cycling properties of CPE in LiFePO4 (LFP) batteries were extensively studied. The CPE-15% PPU film showed the excellent electrochemical stability of 84.3% capacity retention after 890 cycles at 0.5 C and 82.4% capacity retention after 500 cycles at 1.0 C at 50 °C. Especially, the CPE matched with high-voltage LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode delivered long-term stable cycling performances. The novel polymer electrolyte acquired could open up a new horizon to achieve high stable lithium metal batteries.