(506d) Thin Film Composite Separators for Energy Dense Lithium Batteries
AIChE Annual Meeting
2022
2022 Annual Meeting
Materials Engineering and Sciences Division
Polymers for Energy Storage and Conversion
Wednesday, November 16, 2022 - 1:30pm to 1:45pm
The functionality of these thin film composite separators was further enhanced by engineering the microporous membranes. A facile additive manufacturing approach for microporous membranes based on polymerization induced phase separation (PIPS) was developed. Difunctional 1,4-butanediol diacrylate (BDDA) was mixed with ethylene carbonate (EC) and then photopolymerized. During polymerization, the EC became insoluble as the BDDA cures into a crosslinked network and phase separates through spinodal decomposition. By controlling the polymerization kinetics and EC content, the pore sizes and porosities were tuned between 6.8 to 22nm and 15.4% to 38.5%, respectively. Lithium ion battery half cells consisting of LiNi0.5Mn0.3Co0.2O2 cathodes and pBDDA separators were shown to undergo reversible charge/discharge cycling with an average discharge capacity of 142 mAh/g and a capacity retention of 98.4% over 100 cycles - comparable to cells using state-of-the-art separators. Moreover, similar discharge capacities were achieved in rate performance tests due to the high ionic conductivity and electrolyte uptake of the film. The pBDDA separators were shown to be thermally stable to 374°C and exhibited negligible thermal shrinkage up to 150°C, unlike conventional polyolefin separators which shrink by more than 30% at the same temperature, compromising cell safety. Efforts to further engineer composite separators using the PIPS method will be discussed.