An Intrinsically Safe Gel Polymer Electrolyte Comprising Flame Retarding Polymer Matrix for Lithium Ion Battery Application.

State-of-the-art (SOTA) liquid electrolyte/polyolefin separator setups used in lithium ion batteries suffer from the hazard of leakage and high flammability. To address these issues, phosphonate, a flame retarding moiety, is chemically bonded to a polymer matrix to fabricate a non-flammable gel polymer electrolyte (GPE). The obtained phosphonate-based polymer matrix as well as its corresponding GPE (gelled with flammable SOTA non-aqueous liquid electrolyte) show remarkable flame resistivity. Unlike poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP)-based GPEs, the phosphonate-based GPE does not react with lithiated graphite at high temperatures. Both features indicate that the phosphonate-based GPE is superior to SOTA GPEs in the aspect of safety performance. As the flame retarding moiety is chemically bonding to the polymer, the parasitic reactions between the flame retarding moiety and the electrodes are avoided. Consequently, lithium ion battery (LIB) cells comprising phosphonate-based GPE show good capacity retention comparable to cells comprising SOTA GPEs. Compared with SOTA GPEs, phosphonate-based polymer based GPEs show improved intrinsic safety performance and comparable cycle life. Therefore, phosphonate-based polymers exhibit high potential to be used as a new class of polymer matrix for GPE used in LIBs.