UV-Cured Semi-Interpenetrating Polymer Network Electrolyte for High-Performance Bipolar-Stacked Quasi-Solid-State Lithium Metal Batteries

Lithium metal batteries are regarded as promising candidates for next-generation energy storage systems due to their high energy density. However, electrolyte instability and lithium dendrite formation remain critical challenges. Accordingly, a semi-interpenetrating polymer network (semi-IPN) quasi-solid polymer electrolyte (QSPE) is developed by incorporating polyethylene glycol monomethyl ether methacrylate (PEGMA), polyethylene glycol dimethacrylate (PEGDA), and vinyl ethylene carbonate (VEC) into a polyvinyl alcohol (PVA) matrix via UV curing. The prepared semi-IPN QSPE exhibits a high ionic conductivity of 1.36 × 10^-3 S cm^-1 and a Li-ion transference number of 0.78 at room temperature, while maintaining flexibility with a tensile strength of 5.2 MPa and a Young's modulus of 25.1 MPa. Furthermore, it demonstrates a wide electrochemical stability window up to 4.8 V and excellent interfacial compatibility with a lithium (Li) anode. Based on these properties, bipolar cells, constructed by serially connecting two LFP/QSPE/Li unit cells, not only achieve an open-circuit voltage of 6.36 V stably, but also deliver a discharge capacity of 144 mAh g^-1 at 0.2 C with 77.0% capacity retention and 99.0% coulombic efficiency after 100 cycles.