The Study Of UHMWPE And PPEK Separator Material For Lithium Ion Battery

The lithium ion battery has the advantage of high working voltage, large specific energy, long cycle life, small self-discharge and green environment.It has been widely used in consumer electronics, electrical vehicles and industrial energy storage. As a new type of green power, lithium ion batteries have certain significance on the solution of the social problems such as the resources shortage and environment pollution. The separator as one of the core material in lithium ion batteries, is the bottleneck restricting the development of lithium ion batteries. Currently, the main separator material is made from polyolefin, its melting point is low, the heat shrinkage rate is bigger under high temperature. On the other hand, the polyolefin material has low surface energy, its affinity with the polar liquid electrolyte is poor, that leads to small electrolyte absorption and retention, which directly affect the safety and energy density of the lithium ion batteries.Based on the analysis of the above, the research contents of this paper are as folows:1. The compound gel of ultra-high molecular weight polyethylene (UHMWPE) and silicon carbide (SiC) has been made by mixer technology, which mass ratio is 1:10. Then porous membrane material is prepared through two-way stretching and the draw ratio is 2x2, 3x3 and 4x4. The performance of the composite porous membrane is studied as lithium ion battery separator material. From the results we know that the addition of SiC inorganic particles significantly improve the composite membrane’s electrolyte wettability and thermal stability. The draw ratio significantly affects the performance of the composite membrane. With the increase of draw ratio, the porosity, electrolyte absorption and mechanical strength are all improved. For the sample of 4 X 4 draw ratio time, it has excellent electrochemical performance, cycle and C-rate performance.2. The high temperature resistance poly (aryl ether ketone) (PPEK) porous membrane material were prepared through extract activation method and electrospinning. The porous membranes which are formed by the two film-forming methods all show the excellent property of high temperature resistance, after the heat treatment under 120℃ their heat shrinkage rate is 0. Compared with PPEK porous membrane made by extraction activation method, the nanometer fiber membrane made by electro-spinning has excellent porosity, electrolyte absorption and affinity. Its electrochemical properties, cell cycle and C-rate performance also have the incomparable advantages compared to extraction activation method. But the mechanical strength of the nanometer fiber membrane is poor.