A Robust Surface-Modified Separator Fabricated with Roll-to-Roll Atomic Layer Deposition and Electrohydrodynamic Deposition Techniques for High Temperature Lithium Ion Batteries
Afaque Manzoor Soomro, Jae‐Wook Lee, Muhammad Waqas, Young Su Kim, Muhsin Ali, Muhammad Asad Ullah Khalid, Kyung Hyun Choi
Abstract
A multilayer separator is developed by the deposition of ultrathin polyvinylidene fluoride (PVDF) and aluminum oxide (Al 2 O 3 ) layers on polyolefin separator using in-house designed novel roll-to-roll atmospheric atomic layer deposition (R2R-AALD) and electrohydrodynamic atomization (EHDA) methods. The conformal coatings of ultrathin PVDF (∼5 um) and Al 2 O 3 (∼10 nm) layers form a highly uniform interconnect microporous structure, which enhances thermal stability and mechanical strength. The deposition of PVDF and Al 2 O 3 layers also improves electrolyte wettability and electrolyte uptake (256%), which gives rise to ionic conductivity. The Al 2 O 3 /PVDF/Celgard separator shows excellent thermal stability with minimal shrinkage up to 180 °C and robust mechanical strength. The lithium cobalt oxide/graphite (LCO/graphite) cells based on as-developed multilayer separator deliver excellent discharge capacity of 130.9 mAh g −1 at 0.5 C after 150 cycles and capability of 99.6 mAh g −1 at 5 C after 100 cycles at room temperature. Moreover, the LCO/graphite cells with Al 2 O 3 /PVDF/Celgard separator also show remarkable cyclic performances at elevated temperatures. The as-developed separator proves to be a better candidate for high capacity lithium ion batteries, especially for high temperature conditions.