Preparation And Study Of High-performance Gel Polymer Electrolytes For Lithium Ion Battery

Polymer lithium-ion batteries have attracted a lot of attention all over the worldbecause of their advantages such as high voltage, no environmental pollution, longlife, adapt to any shape, size and excellent safety performance characteristics. As animportant component of polymer lithium-ion batteries, polymer electrolyte plays avery crucial role. In this paper, both excellent polymer thermoplastic polyurethane(TPU) and polyvinylidene fluoride-hexafluoropropylene (P(VDF-HFP)) had beenchosen as the matrix polymer, the gel polymer electrolyte prepared by the blendedmaterial has reached the target we set. This gel polymer electrolyte has excellentmechanical properties, high ionic conductivity and electrochemical stability. Thecontents of our study are as follows:Firstly, pure TPU, P(VDF-HFP) and blending TPU/P(VDF-HFP) films havebeen prepared by electrospinning technique. These films are immersed in1MLiClO4-EC/PC in the electrolyte activated respectively, ultimately the gel polymerelectrolyte was obtained. Compared the performance of three kinds of gel polymerelectrolyte, the TPU/P(VDF-HFP) gel polymer electrolyte(GPE) shows a high ionicconductivity about4.1mS cm-1at room temperature, a first charge–discharge capacityof168.8mAh g-1which is99%theoretical capacity of LiFePO4. The electrochemicalstability of the GPE is at5.5V versus Li+/Li. The TPU/P(VDF-HFP) membranesshow a high tensile strength (8.38MPa) and elongation (118.8%). The test found thatTPU/P(VDF-HFP)-based gel polymer electrolyte has good electrochemical andmechanical properties.Secondly, a series of TPU/P(VDF-HFP) films were prepared by electrospinningwith different concentrations of polymer solution.10%GPE has a high ionicconductivity6.62mS cm-1, the first discharge capacity of169.04mAh g-1. After30cycles of charge-discharge tests, the discharge capacity still reached168mAh g-1at0.1C-rate, with little attenuation. The results show that10%gel polymer electrolytefilms display excellently in the physical structure, the electrochemical and mechanicalproperties, it is the best membrane material for a lithium ion battery.Finally, different mass ratio of TPU/P(VDF-HFP) films prepared byelectrospinning technique. TPU/P(VDF-HFP) films with mass ratio of1:1have thebest ionic conductivity about4.69mS cm-1at room temperature. TPU/P(VDF-HFP)films with mass ratio of1:1as a gel polymer electrolyte in lithium-ion batteries also exhibit superior performance, with absolute superiority exceeding the gel polymerelectrolyte materials with mass ratio of1:4and4:1.