Confined in-situ polymerization of poly(1,3-dioxolane) and poly(vinylene carbonate)-based quasi-solid polymer electrolyte with improved uniformity for lithium metal batteries

Abstract

In-situ polymerization to prepare solid/quasi-solid electrolytes for lithium batteries has been extensively researched in recent years, owing to its unique superiority in achieving good physical contact with rigid electrodes. However, the uniformity of in-situ polymerized electrolytes at elevated temperatures remains a challenge, which may be influenced by the uneven heat distribution during polymerization. In this work, we demonstrate a novel confined in-situ polymerization method, which allows the fabricated electrolytes with dual polymer networks to enhance the electrolyte homogeneity. 1,3-Dioxolane (DOL) is firstly cationically polymerized at room temperature, and next vinylene carbonate (VC) is free-radically polymerized at an elevated temperature under the confinement effect of the poly (DOL) skeleton. Using this stepwise strategy, more uniform polymerization of VC under heating treatment can be achieved. The obtained quasi-solid polymer electrolyte possesses a high ionic conductivity at room temperature of 1.98 × 10−3 S/cm, relatively low activation energy of 0.13 V and an oxidation potential up to 4.3 V. Full cell employing LiFePO4 cathode, Li metal anode and the in-situ polymer electrolyte possesses an initial discharge capacity of 117 mAh/g at a charge/discharge rate of 2C, with a high capacity retention ratio of 92.1% after 1500 cycles, showing promising application prospects.