Fabricating a high performance composite separator with a small thickness for lithium ion batteries

Abstract Separator is a porous membrane that physically separates the cathode and anode, yet ensures the lithium ion transport between these two electrodes. This work attempts to develop a high performance composite separator that can also provide a low cost potential when produced at a large scale. For this purpose, a non-woven reinforced macroporous polyaramid separator with a thickness comparable to mainstream commercial products was developed to achieve improved separator mechanical performance and uniformity. The separator consists of a polymer phase with a uniform porous structure and a non-woven reinforcement. The non-woven structure made using a wet-laid process provides the increased separator mechanical strength, while the macroporous polyaramid phase modified with nano and submicron ceramic particles optimizes the pore structure for improved battery electrochemical performance. Compared with the commercial polyolefin separator, this developed separator showed superior mechanical and physical robustness at elevated temperatures. The separator wettability by the standard liquid electrolyte was also much improved. A stable cycle performance and an improved rate capability have been observed when the separator was evaluated in full coin cells.