Synthesis And Properties Of Composite Polymer Electrolytes For Lithium Ion Battery

The polymer lithium ion battery is considered as one of the best candidates for the next generation power sources, because it has many advantages such as high specific capacity, little possibility of electrolyte leakage, flexible packaging and shapes, polymer lithium battery has broad prospects and has received great interest in recent years. Poly(ethylene oxide)(PEO)-based polymer electrolytes have received extensive attentions for their potential capability to be used as alternative candidate materials for the traditional liquid electrolytes in all solid-state polymer lithium ion batteries. However, there are many problems, such as low temperature conductivity of polymer electrolyte, the bad compatibility of the interface between polymer electrolyte and electrode material, that seriously affecting the cycle and safety performance of the batteries, must be solved. Therefore, the polymer electrolyte systems must be improved. In this dissertation, many efforts have been invested in the study of the problems, and the results as follows:1. The novel comblike polymer P(EO+EM1+AGE) was synthesised from EO, EM1and AGE by the method of anion coordination polymerization. Polymer electrolyte was prepared with the comblike polymer as the matrix, and its performance was studied. The results showed that the performances of the novel SPE were better than the PEO base polymer electrolyte. The lithium ion transference number of the novel SPE could reach0.29.2. Nano silica with carbonate groups was synthesized by the esterification reaction, the structure of the modified nano silica was characterized by methods of FTIR and TGA. The composite polymer electrolytes (CPEs) were prepared by introducing the modified nano silica. The structure and electrochemical performances of the CPEs were studied by DSC and AC impedance. Results showed that the addition of modified nano silica enhanced the thermal properties and ionic conductivities of CPEs, and meanwhile the lithium ion transference number of CPEs increased up to0.32. Ac impedance results revealed that modified nano silica could also improve the interfacial stability between CPEs and lithium metal electrode. 3. A new composite polymer electrolyte was prepared with the comblike polymer as the matrix, and the modified nano silica M-3as the filler. Performance of the new CPE was studied. Results showed that the content of M-3has great influence on the performance of CPE. In a certain range, the crystallinity of polymer reduced firstly,and then increased. When the content of M-3was8%, the crystallinity of polymer was the minimum. At this time, the ionic conductivity and lithium ion transference number of CPE were also the maximum.