Molecular Design for In‐Situ Polymerized Solid Polymer Electrolytes Enabling Stable Cycling of Lithium Metal Batteries

Abstract The practical application of polymer electrolytes is hindered due to the low ionic conductivity and the interfacial instability between the electrodes. Herein, a strategy for designing solid polymer electrolytes is developed that facilitates the rapid lithium‐ion migration through weak coordination with polymer chain segments, as well as the fast ion channel transport of oligomers. Moreover, the in situ‐produced solid polymer electrolyte (PFVS) can form stable LiF‐rich interfaces with both the lithium metal anode and different cathodes. When the PFVS is applied in Li‐metal batteries, excellent properties are achieved at room temperature. A Li||Li symmetric cell can be stably cycled for 4000 h at a current density of 0.1 mA cm−1, a Li||LiFePO4 full cell can maintain capacity retention as high as still 94.4% after 600 cycles at 1 C, and a Li||NCM811 full cell can retain 80% capacity after 180 cycles at 1 C. A 2.6 Ah Graphite|PFVS|NCM90 pouch cell is made for demonstrating the practical application potential, and it can be also stably cycled. The developed strategy provides a promising path for designing solid polymer electrolytes that can effectively extend the lifespan of Li metal batteries.