An initiator loaded separator triggering in situ polymerization of a poly(1,3-dioxolane) quasi-solid electrolyte for lithium metal batteries

Abstract

An in situ polymerization strategy is regarded as a promising approach to fabricate gel polymer electrolytes (GPEs) and improve interface contact between the electrolyte and electrodes, in which the initiator is initially dissolved in the precursor solution. Herein, aluminum trifluoromethanesulfonate (Al(OTf)₃) is preloaded onto a separator sheet as the initiator to trigger the ring-opening reaction of 1,3-dioxolane (DOL). The polymer matrix near the separator has a higher crystallization degree than that far away from the separator. Fluoroethyl carbonate (FEC) is further introduced as a liquid plasticizer to produce an amorphous GPE for enhanced ionic conductivity and interfacial stability. As a result, the as-synthesized FEC based GPE exhibits a substantial ionic conductivity of 1.5 × 10⁻⁴ S cm⁻¹ at room temperature, an expanded electrochemical window of 4.8 V, and a high Li⁺ transference number of 0.63. The symmetric Li|Li cell exhibits a stable lifespan for 650 h at 1 mA cm⁻² and 1 mA h cm⁻². Moreover, the LiFePO₄ full cell exhibits stable cycling for 300 cycles at 1C with a capacity retention of 94.5%. This work provides a novel idea for the in situ synthesis of advanced GPEs toward practical application of solid-state lithium metal batteries.