Preparation And Study Of High-performance TPU/PVDF/PS Gel Polymer Electrolytes For Lithium Ion Battery

With the rapid development of science and technology, looking for new environmental protection green energy has becomed the theme of the times. As an important branch of green energy, polymer lithium-ion battery becomes the focus of research. The advantages of polymer lithium-ion batteries contain high voltage, low environmental pollution, long service life, strong adaptability, high quality specific capacity, high charge and discharge capacity and good safety performance, etc. Fluoro-polymers have received much attention due to their good electrochemical stability and affinity of superiority to electrolyte solutions. In this paper, nanofibrous membranes based on poly(vinylidene fluoride)(PVDF), thermoplastic polyurethane(TPU) and polystyrene(PS) are prepared by electrospinning technique and the corresponding composite gel polymer electrolytes(GPEs) are obtained after being activated in liquid electrolyte. Through a series of tests, this GPE ha s excellent mechanical properties, high ionic conductivity and electrochemical stability, which is suitable for application in lithium-ion batteries. The contents of our study include the following three parts:Firstly, the blend films of TPU/PS, PVDF/PS and TPU/PVDF/PS have been prepared by electrospinning technique at room temperature. These films are activated with 1 M LiClO4-EC/PC respectively, and the GPEs have been obtained. Through the study, the GPE based on TPU/PVDF/PS shows a high ionic conductivity of 5.46 mS cm-1, the electrochemical stability window of 5.9 V, a first discharge capacity of 169.5 mAh g-1 which is about 99.9% theoretical capacity of LiFePO4. The TPU/PVDF/PS films show a high tensile strength(12.8 MPa) and elongation(99.4%). Studies have shown that the GPE based on TPU/PVDF/PS has the most superior performance.Secondly, a series of TPU/PVDF/PS membranes with different polymers concentrations have been prepared by electrospinning. These membranes are activated with 1 M Li ClO4-EC/PC, and the GPEs have been obtained. At 0.1C-rate, the GPE with concentration of 10% of TPU/PVDF/PS shows the best performance with the first charge and discharge capacity of the lithium ion battery respectively 169.8mAh g-1 and 169.6 mAh g-1 after 50 times charging and discharging cycles, little attenuation, discharge capacity is still as high as 164.3 m Ah g-1. Test results clearly show that the electrospun membrane with concentration of 10% TPU/PVDF/PS is the most suitable for lithium-ion diaphragm material.Finally, the films with different mass ratio of TPU/PVDF/PS have been prepared by electrospinning. These membranes are activated with 1 M LiClO4-EC/PC, and the GPEs have been obtained. The test results show that the performances of TPU/PVDF/PS film with mass ratio of 6:6:1 has the most superior performance. It has the highest ionic conductivity reached 5.52 mS cm-1 and the first charge-discharge capacity been 169.4 mAh g-1and 168.9 m Ah g-1. The TPU/PVDF/PS films with mass ratio of 6:6:1 is very suitable for lithium-ion batteries.