Investigation of cyano resin-based gel polymer electrolyte: in situ gelation mechanism and electrode-electrolyte interfacial fabrication in lithium-ion battery

Cyanoethyl polyvinyl alcohol (PVA-CN)-based gel polymer electrolyte (GPE) is a high-performance electrolyte for lithium-ion batteries (LIBs), which is in situ synthesized from a stable monomer without using additional initiators. Unfortunately, the gelation mechanism of PVA-CN is still unclear. Furthermore, for general GPEs prepared by in situ polymerization, the electrode-GPE interface in batteries remains to be further optimized. Here we present the gelation mechanism of the PVA-CN-based GPE and fabricate an electrode-GPE interface with less resistance during battery formation. The cross-linkable PVA-CN-based organogel is formed via in situ cationic polymerization of the cyano resin initiated by PF5, a strong Lewis acid produced by the thermo-decomposition of LiPF6. It is interesting to find that the battery formation process completed in the precursor solution instead of gel can greatly reduce the interfacial resistance of graphite-GPE and benefit the formation of a more stable solid electrolyte interface (SEI) on the anode, which contributes to a dramatic improvement in battery performance. This work gives useful guidance towards designing new GPE materials and promoting their practical application in LIBs.