The Design, Synthesis And Performance Of Phosphorus-containing Gel Polymer Electrolytes For Lithium Ion Batteries

The high conductivity of new phosphorus-containing gel polymer electrolyteswere synthesized and used in the lithium-ion batteries.Seven alkenyl dialkylphosphates/phosphonates were synthesized and characterized by1H NMR,31P NMR,13C NMR, FT-IR and HR-MS. The radical homopolymerization of alkenyl dialkylphosphates/phosphonates were studied. Meanwhile, the copolymerization reactionwith other double bond monomers such as acrylates, methacrylates, styrenes,acrylonitrile and crosslinking agents were investigated. The structure and molecularweight of polymers were characterized by1H NMR,31P NMR,13C NMR and GPC.The results showed alkenyl dialkyl phosphates/phosphonates had poorhomopolymerization ability, and poly(alkenyl dialkyl phosphates/phosphonates) hadsmall molecular weight not exceeding five thousand. But at the same time, alkenyldialkyl phosphates/phosphonates had good copolymerization ability with othermonomers by testing the composition of the phosphorus-containing compounds. Thegood thermal stabilities of phosphorus-containing polymers were ascertained byTGA and DSC.Based on the study of the polymerization reaction of alkenyl dialkylphosphates/phosphonates, in the presence of a free radical initiator, a series ofphosphorus-containing crosslinked copolymer gel electrolytes containing alkenyldialkyl phosphates/phosphonates, bifunctional crosslinking agent, comonomers andliquid electrolyte were synthetized by the in-situ thermal polymerization method.The ionic conductivity, physical observation and mechanical properties of the gelpolymer electrolytes were tested and discussed carefully. Based on these researchresults, the optimal ratios of copolymer gel electrolytes were selected. The impact ofdifferent comonomers, monomer ratios, electrolyte contents, and temperatures on theconductivity of gel polymer electrolytes were discussed in detail. Tries hard tosummarize the rule, provides the science for the synthesis of excellent overallperformance of phosphorus-containing high conductivity gel polymer electrolytes. The morphology and microstructures of the polymers were studied by SEM. Theresults displayed the polymer matrixes have three-dimensional porous networkstructures, which demonstrated the high conductivity of phosphorus-containing gelpolymer electrolytes. The self-extinguishing time and burning time of the gelpolymer electrolytes were tested by combustion experiments. The results showedthat phosphorus-containing gel polymer electrolytes had good flame retardantproperty. To explain the high conductivity of phosphorus-containing gel polymerelectrolytes deeply, the interaction between Li+and P in phosphorus-containingcompounds was studied by the31P NMR spectra.