High‐Performance Pure Polymer Electrolytes with Enhanced Ionic Conductivity for Room‐Temperature Applications

All‐solid‐state lithium metal batteries (ASSLMBs) are renowned for their high energy density and safety, positioning them as leading candidates for next‐generation energy storage solutions. In this study, pure polymer solid‐state electrolytes are developed using the solution casting method, optimized for room temperature operation. The base material, poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), is enhanced with succinonitrile (SN) and polyacrylonitrile (PAN) to improve its electrochemical performance at room temperature. The optimized electrolyte, PSP‐0.05, demonstrated superior characteristics, including an ionic conductivity (σ) of 3.2 × 10−4 S cm−1 and a wide voltage window of up to 5 V. When integrated into full batteries, PSP‐0.05 exhibited exceptional performance in multiplicative cycling tests at room temperature, achieving discharge specific capacities of 132 and 113 mAh g−1 at 3 and 5 C rates, respectively. Additionally, long‐term cycling at 1 C rate resulted in an initial discharge‐specific capacity of 145.2 mAh g−1 with over 94.9% capacity retention after 1000 cycles. Given the simplicity of the preparation process and its impressive electrochemical properties, the PSP‐0.05 electrolyte holds significant potential for practical applications in safer ASSLMBs. Using the solution casting method, cyclic‐structured pure polymer solid electrolytes are prepared. The high‐performance PSP‐0.05 demonstrated a 5 V electrochemical window and sustained a discharge capacity of 137.8 mAh g−1 after 1000 cycles at 1 C rate, proving especially suitable for room temperature applications.