The Preparation And Properties Of Novel Phosphate-based Lithium-ion Battery Gel Polymer Electrolytes

A new type of high conductivity phosphate-based lithium-ion battery gel polymer electrolytes combined with good flame retardant has been prepared and investigated in the thesis.(Acryloyloxyethyl)dialkyl phosphates and(2-(methyl)acryloyloxyethyl)dialkyl phosphates have been synthesized and used as polymerization monomer. The structure of the compounds was characterized by HR-MS, 1H NMR, 31 P NMR, 13 C NMR and FT-IR. The homo-polymerization and copolymerization with the typical double bond monomers(such as styrene, etc) were studied by radical polymerization method. Both molecular weight and structure of the polymers were characterized by 1H NMR, 31 P NMR and GPC. The result proved that such monomers have both better self polymerization and copolymerization ability. The good thermal stability of the homopolymers and copolymers were demonstrated by TGA and DSC.Before preparing novel phosphates-based gel polymer electrolytes, we optimized related polymerization conditions of in-situ heat polymerization method.Afterwards, the method was applied to prepare a series of cross-linked phosphate gel copolymer electrolytes under the vacuum condition of mixing cross-linking agent,free radical initiator, comonomers and liquid electrolyte. The ionic conductivity of the gel polymer electrolytes combined with its external mechanical properties were focused on analyzing, and the conductivity changes in different molar ratios based on phosphate and crosslinking agent, different phosphates, phosphate and other double bond monomers series were investigated in detail. The high conductivity phosphate-based gel polymer electrolytes with better comprehensive performance have been optimized. Furthermore, the combustion rate and self-extinguishing time of both monomers added system and corresponding gel electrolyte system were measured by combustion experiments. It turned out such phosphate monomer and the corresponding phosphate-based gel electrolyte had good flame retardant properties. The three-dimensional internal porous structure of the polymers matrixwere observed by SEM. It was indicated the existence of a good ions transmission channel inside gel electrolyte, which leaded to the high conductivity of the gel polymer electrolytes. By using HR-MS, 31 P NMR and FT-IR to detect the mixed solution of phosphate and liquid electrolyte or lithium salt solution, a certain degree interaction between Li+ and phosphate was confirmed, further explained the high conductivity of the phosphate-based gel polymer electrolytes. The residual monomer amount of the electrolytes was calculated by the corresponding experiments and the high monomer conversion rate was proved, that meant the battery performance was slightly affected by the lower residual monomer.