A highly efficient surface modified separator fabricated with atmospheric atomic layer deposition for high temperature lithium ion batteries
Jae‐Wook Lee, Afaque Manzoor Soomro, Muhammad Waqas, Muhammad Asad Ullah Khalid, Kyung H. Choi
Abstract
A high throughput mass production of separator is proposed using a well-established unique in-house process of roll-to-roll atmospheric atomic layer deposition. An ultra-thin conformal layer of Al2O3 is deposited over the commercial Celgard (PE/PP/PE) using multi-slit gas source head. Overall 10 nm increase is incurred in the thickness, while maintaining the porosity to ~48%. The entire process of fabrication was performed at very low temperature of 90°C. The high thermal stability of as-modified separator is achieved at of 180°C. The separator was analyzed using X-ray photoelectron spectrometer, electrochemical impedance spectra, and field emission scanning electron microscope. The as-developed separator showed excellent wettability due to the surface medication in addition to robust flexibility, high conformity, and minimal thermal shrinkage. The Lithium cobalt oxide (LCO)/Graphite cells with atomic layer deposition (ALD) Celgard (Al2O3 deposited) separator delivered remarkable discharge capacity with 79.5% capacity retention after 100 cycles at 1 C as compared to the uncoated-separator(Celgard separator), which yielded relatively less retention of ~70%. Moreover, the LCO/Graphite cells with the ALD-Celgard separator delivered the discharge capacity of 140 mAh/g at elevated temperature (up to 80°C).