The Impact of FEC Additive on Deep Eutectic Gel Electrolyte with Self-Healing Property for Solid-State Li Metal Batteries

Deep eutectic solvents (DES), as a flame-retardant electrolyte system, have the merit of high ionic conductivity and low preparation cost. However, the poor compatibility of DES-based electrolyte with Li metal anode has seriously restricted its prospects for applications. To solve this problem, a novel DES-based gel electrolyte (DSA) has been prepared by the polymerization of SSH monomer with 4-acryloylmorpholine (ACMO) in the DES solution with/without an additive of fluoroethylene carbonate (FEC) under UV-irradiation, in which SSH monomer is synthesized by the reaction of cystine reagent with 2-isocyanethyl methacrylate ester. The impact of FEC additive on the performance of DSA electrolyte has been investigated in detail. Owing to the presence of urea-based hydrogen bonds and dynamic disulfide bonds in the SSH-ACMO gelling agent, DSA electrolyte with good mechanical properties exhibits an excellent self-repair capability at room temperature. Because of promoting the formation of SEI layer on Li metal anode, the incorporation of FEC additives could significantly improve the electrochemical performance of DSA electrolyte. The experimental results show that the as-prepared DSA-2 electrolyte sample presents high ionic conductivity of 0.85 mS cm−1 at room temperature, broad electrochemical window of 4.5 V, good non-flammability and stable interfacial characteristics.