Research And Development Of Lithium-ion Battery With Gel Polymer Electrolyte

Gel polymer lithium batteries (GPLB) not only have the excellent performance of liquid lithium battery, but also can resolve the possible problems of leakage and blast owing to no free liquid electrolyte in GPLB. It is also very convenient to design the shape at will. Now the ion conductivity of gel polymer electrolyte (GPE) can reach the magnitude of 10-3S/cm, which can satisfy the practical request. However, it is still lower than that of liquid electrolyte (10-2 S/cm), which causes the fall of high rate discharge and low temperature performance of lithium battery. Now the main method of preparing GPLB is to fabricate a GPE film through solution casting first, and then assemble the battery. The cost of the process is very high and it is difficult to treat with the disused solvents, therefore, it is difficult for most liquid lithium battery manufactures to transfer to produce GPLB.Focusing on the preparation process of lithium battery, thermal polymerization process of the GPE and optimizing the component of the gel electrolyte, the paper intends to resolve some of the key problems mentioned above and to prepare a GPLB with good performance.Firstly, a situ-polymerization method as the preparation process of GPLB is introduced and PMMA as the polymer matrix of the gel electrolyte is selected. The thermal polymerization process of the gel electrolyte is also optimized.Secondly, the sorts and weights of the components of the gel electrolyte are optimized, and a GPE with excellent performance is prepared, whose ion conductivity reachs 9.2mS/cm. We analyze all the factors influencing the performance of the GPE, and study many performances of the GPE, including the microstructure, conductivity performance, liquid electrolyte holding ability, electrochemical stability, thermodynamics stability, and interfacial stability between electrolyte and electrode, et al.Finally, we prepare some GPLBs using the GPE mentioned above through situ-polymerization process followed by measuring the performance of the batteries. The GPLB exhibits good discharge performance with discharge curve declining slowly, and the average discharge voltage is 3.7V. It also has good rate charge and discharge performance, whose discharge capacity at 2.0C is over 90% of that at 0.2C. The cycle performance at 0.5C discharge rate is very good but bad at high discharge rate (1.0C). The low temperature performance also needs to be improved.