In Situ Electrolyte Gelation to Prevent Chemical Crossover in Li Metal Batteries

Abstract Chemical crossover is one of the key factors affecting the stable cycling of Li metal batteries using conventional carbonate electrolyte. Solid state electrolyte can help solve this problem, but has serious electrolyte/electrode problems that may cause non‐uniform Li deposition. Herein, a simple strategy to balance the chemical crossover and interfacial problems by employing composite gel electrolyte composed of PEO‐based polymer electrolyte and liquid LiPF₆ electrolyte, is reported. The high viscosity of the gel polymer can effectively prevent side reaction products and also ensures good contact between electrolyte and electrode. Meanwhile, Li⁺ migration number of the colloidal polymer electrolyte is as high as 0.67, allowing the cells to be operated at room temperature. The full battery assembled with commercial high‐capacity LiFePO₄ (12 mg cm^–2) has a specific capacity of 110 mAh g^–1 after 160 cycles along with high Coulombic efficiency. Further structural analyses confirm the LiFePO₄ cathodes are well maintained after long‐term cycling, indicating the simple cell engineering process is effective to prevent the shuttling of undesired ions and thus protects LiFePO₄ cathode from corrosion due to chemical crossover.