SnCl4 initiated formation of polymerized solid polymer electrolytes for lithium metal batteries with fast ion transport interfaces

Solid-polymer-electrolytes (SPEs) are under active consideration for their high-energy and safe electrochemical energy storage. However, conventional polymer electrolytes are facing poor electrolyte/electrode interfacial contact and undesired lithium dendrite problems. Here, we report a polymerized-dioxolane (P-DOL) electrolytes created by in situ polymerization of DOL in the presence of tin tetrachloride (SnCl4), which enables ultra-conformal interfacial contact with all cell components. More importantly, SnCl4 plays a dual function by initiating ring-opening polymerization of DOL and simultaneously forming a LiCl/LixSn-based alloy composite protective layer on Li metal anodes. The robust Li-rich ion conductive alloys coupled with an electronically insulating surface component form fast ion transport channels. Using the SnCl4-initiated P-DOL SPEs exhibits a high ionic conductivity (>2 mS cm−1) and a wide electrochemical window (4.7 V) at room temperature. Applications of P-DOL SPEs in Li/Li symmetric and Li/LiFePO4 batteries further demonstrate low polarization and high capacity retention. This work provides a facile and practical approach to designing P-DOL SPEs for high-performance lithium metal batteries.