The Study On Process And Performance Of Gel Polymer Electrolyte By In-situ Thermal Polymerization

Currently the gel polymer lithium ion batteries have already had a scale, but the production still have two key problems: one problem is the ionic conductivity of the gel polymer electrolyte (GPE) which is still lower than the liquid electrolyte,and that causes the fall of high rate discharge and low temperature performance of lithium battery. The other one is the making methods of the gel polymer electrolyte (GPE) that not only solution casting method but also the American Bell-core method have some common problems, such as the complicated process and the high production cost.Focusing on the two problems, this paper adopts the method of in-situ thermal polymerization to fabricate gel polymer electrolyte. Firstly take out a certain rate of the monomers, cross-linking agent, initiator and liquid electrolyte, then mix them to prepare the precursor solution. Secondly heat the precursor solution to initiate a polymerization reaction, and at last the precursor solution turns to gel and the preparation of GPE is completed. The paper mainly has studied the system of the GPE , the excellent progress condition and the best ratio of component in precursor solution . By testing the performance of the GPE the paper tries to find a excellent gel polymer system and technical parameters in order to realize the in-situ polymerization in lithium ion battery and achieve the improvement of the making progress of the polymer lithium ion battery .In this paper a excellent gel polymer system including methyl methacrylate (MMA), butyl acrylate(BA) and triethylene glycol dimethylacrylate (TEGDMA) has been found, and the best progress condition is thermal polymerization III.In this paper the sort and weights of the components of the gel electrolyte has been optimized, and a gel polymer electrolyte with excellent performance has been prepared, whose ion conductivity reaches 8.16 mS/cm .The porous structure of the polymer base has been observed by SEM .The ionic conductivity of the GPE has been tested using AC impedance spectra .The factors such as temperature and time influencing the performance of the GPE has been analyzed too. There is no chemical reaction since the scan potential has 6.0V by technique of linear sweep voltammetry. It proves that the GPE has a good performance of electrochemical stability. The TG-DTA spectra both reveals that the GPE has a good thermodynamics stability. The lithium ion transference number of the GPE has been tested by using constant potential step, and the relationship between the ion transference number and the various contents of liquid electrolyte has been approximately studied. The paper also has studied the interfacial stability between GPE and lithium slice by using AC interfacial impedance spectra. Moreover, the mechanical strength of GPE with various contents of liquid electrolyte has been approximately studied by pressure testing machine .