Gel Electrolyte Based On Polymer Material Of Glycerol Carbonate Doped With Lithium Salt

Polymer electrolytes played an important role in lithium-ion batteries and it had been widely studied to improve the conductivity as people required higher performance for lithium-ion batteries. The gel electrolytes overcame low conductivity with solid polymer electrolyte. A series of derivatives of glycerol carbonate had been synthesised, it contained acrylic glycerol carbonate as polymer matrix and tri(2,3-cyclic glycerol carbonate) triethylamine ether, tri(2,3-cyclic glycerol carbonate) borate as additives in plasticizer. IR and 1H NMR were used to characterize the compounds. The electrochemical performances of the gel electrolytes were tested. The details as follow:(1) Synthesise and characterize of gel electrolytes based on acrylic glycerol carbonate as polymer:acrylic glycerol carbonate had been synthesised by the substitution reaction. Acryloyl chloride was taken from two methods, acrylic acid and benzoyl chloride as the raw materials or acrylic acid and phosphorus trichloride as the raw materials. The second method with stirring 2 h in 76℃and vacuum distillation has higher yield. Acrylic glycerol carbonate (AGC) was taken from glycerol carbonate and acryloyl chloride, anhydrous tetrahydrofuran as solvent. AGC and MMA were used to copolymerize to prepare P(AGC-MMA). The gel electrolyte was prepared by dipping the P(AGC-MMA) film in PC containing 1 mol/L LiClO4, the conductivity of the gel electrolyte reached 1 .0533×104S·cm -1.(2) Synthesise and electrochemical performance test of gel electrolytes based on tri(2,3-cyclic glycerol carbonate) triethylamine ether and tri(2,3-cyclic glycerol carbonate) borate as additives:p-toluenesulfonic glycerol carbonate was taken from glycerol carbonate and 4-toluene sulfonyl chloride as the raw materials, acetone as solvent; tri(2,3-cyclic glycerol carbonate) triethylamine ether was taken from p-toluenesulfonic glycerol carbonate and triethanolamine as the raw materials, NaH as catalyst, anhydrous tetrahydrofuran as solvent; tri(2,3-cyclic glycerol carbonate) borate was taken from glycerol carbonate and boric acid, NaHSO4 as catalyst. The plasticizers were prepared in 1 mol/L LiC104 in PC with different amount of additives. The viscosity of the plasticizers increased with the weight ratio of additives. The electrochemical stability window of the electrolytes were slightly increased.(3) The gel electrolyte was prepared via dipping the P(AGC-MMA) films in 1 mol/L LiClO4 in PC with tri(2,3-cyclic glycerol carbonate) triethylamine ether and tri(2,3-cyclic glycerol carbonate) borate for a certain time. The influence of the dipping time to the conductivity of the gel electrolyte was tested. With the dipping time increased, the conductivity reached a maxium at 60 min, it reached 1.4686×10-4 Scm-1 and 1.5151×10-4 Scm-1 for tri(2,3-cyclic glycerol carbonate) triethylamine ether and tri(2,3-cyclic glycerol carbonate) borate as additives, respectively. But with the dipping time extended, the mechanical property of films descended, so 45 min was selected as the dipping time.(4) With the ratio of the additives increased, the conductivity of the gel electrolyte was improved. When fixed the dipping time to 45 min, the conductivity of the gel electrolyte with the plasticizer dopped 3 wt% tri(2,3-cyclic glycerol carbonate) borate reached 1.0029×10-4 S·cm-1, the conductivity of the electrolyte with the plasticizer dopped 2.5 wt% tri(2,3-cyclic glycerol carbonate) triethylamine ether reached 0.9992×10-4 S·cm-1.