In Situ Construction of Polymer Electrolytes with Dynamic Covalent Networks via Initiator-Free Thiol-Methacrylate Radical Polymerization

Poly(ethylene oxide) (PEO), as an optimal matrix for polymer electrolytes (PEs), faces the awkward situation of low ionic conductivity and poor cycling performance. Adopting a dynamic covalent bond exchange strategy can enhance the mobility of polymer chains, thereby effectively improving the comprehensive performance of PEs. Herein, in order to improve the battery performance and investigate the effect of dynamic exchange on battery cycling, a disulfide-thiol exchange reaction was used to prepare in situ cross-linked PEs with dynamic covalent networks. The sulfur radicals formed by disulfide-thiol exchange can initiate thiol-methacrylate polymerization at room temperature, leading to the construction of cross-linked networks without an initiator or catalyst. The obtained electrolyte film exhibits an outstanding self-healing ability owing to disulfide metathesis and disulfide-thiol exchange. Moreover, the enhanced dynamic exchange can effectively increase the ionic conductivity of PEs. Due to these fast exchange reactions, the lithium-ion transference number (tLi+) of PEs is 0.58, which is much higher than those of PEO-based electrolytes. Meanwhile, the assembled Li|PEs|Li symmetric battery can cycle stably for 450 h at a current density of 0.1 mA cm–2. In addition, the Li|PEs|LiFePO4 half-cell can cycle stably for 250 cycles at 0.5C with a capacity retention of approximately 100%. As expected, the in situ construction of dynamic covalent networks based on thiol-methacrylate radical polymerization offers a workable strategy for the fabrication of high-performance PEs.