Heat-activatable Microporous Separator Membrane and its Use in Lithium-ion Batteries

摘要

Lithium-ion battery has been the preferred power source for various applications because of its high energy density, long cycle life, and the absence of a "memory" effect problem. The separator membrane used for the lithium-ion battery is basically a polyolefin type porous polymer such as polyethylene "PE", polypropylene "PP", and a trilayer PP/PE/PP[1-3]. The separator membrane is not able to adhere onto cell electrodes by itself. Therefore, an external pressure is usually applied by winding separator and electrodes together and then packaging into a metal case to maintain proper contact between separator and electrodes. A novel heat-activatable microporous separator membrane has been developed by Policell Technologies Inc. and Hitachi Maxell Ltd. The microporous membrane has the capability to be bound onto cell electrodes through heat activation. As a result, the cell has an excellent interface. The cell built with the use of such a heat-activatable membrane shows higher rate capability, longer cycle life, and lower as well as stable impedance during charge-discharge cycling.