A Multifunctional Potent Lewis Acid for In Situ Formation of Poly‐Dioxolane Electrolytes Toward High‐Performance Quasi‐Solid State Lithium Metal Batteries

Quasi‐solid‐state polymer electrolytes represent a promising strategy for Li metal batteries (LMBs) with superior safety and energy density. However, Li dendrite formation and unstable interfaces significantly hinder their practical application. Here, an AlCl 3 ‐initiated gel polymer electrolyte (AGPE) is developed via in situ ring‐opening polymerization of 1,3‐dioxolane (DOL) to directly generate poly(1,3‐dioxolane) (PDOL) electrolyte in battery cells. AlCl 3 acts both as polymerization initiator and a multifunctional additive, enhancing polymer network stability and facilitating selective Li + transport through an AlCl 3 ‐mediated multi‐coordination framework. Additionally, AlCl 3 spontaneously generates a hybrid SEI layer composed of LiF, LiCl, and LiAl, significantly enhancing interfacial stability and suppressing dendritic growth. Consequently, the AGPE achieves excellent ionic conductivity (≈5.0 mS cm −1 at room temperature) and an outstanding Li + transference number (t Li+ = 0.75). Li||LiFePO 4 full cells employing AGPE exhibit superior electrochemical stability, retaining 92.7% capacity after 280 cycles at 0.5 C and delivering a high capacity of 118.2 mAh g −1 at 5 C. These results highlight AGPE as an attractive quasi‐solid electrolyte, demonstrating substantial promise for safe and high‐performance next‐generation LMBs.