Insights into the\nDeterioration Mechanism of Charging\nAbility during Calendar Aging and Cycling Aging of High-Voltage Co-Poor\nNCM Cathode-Graphite Full Battery

Lithium-ion battery (LIB) has gained significant recognition\nfor\nthe power cell market owing to its impressive energy density and appealing\ncost benefit. Among various cathodes, a high-voltage cobalt-poor lithium\nnickel manganese cobalt oxide cathode (Co-poor NCM cathode) has been\nconsidered as a promising strategy to enhance its energy density.\nDespite these advantages, high-voltage Co-poor NCM cathode-graphite\nfull battery usually suffers from poor rate performance. However,\nfast charging has been a key indicator for widespread application\nof power batteries. Although many efforts have been made to improve\nthe charging performance of fresh batteries, few works investigate\nthe charging ability during calendar aging and cycling aging of high-voltage\nCo-poor NCM cathode-graphite full battery. In this work, we found\nthat the charging ability becomes worse during calendar aging and\ncycling aging. Results showed that the increasing charge transfer\nresistance from the cathode is the major obstacle to achieving fast\ncharging during the aging process. To address the problem, high-voltage\nAl<sub>2</sub>O<sub>3</sub>-coated Co-poor NCM cathode successfully\nprepared via a simple atomic layer deposition (ALD) method has been\ndeveloped to reduce the decay of charging performance during calendar\naging and cycling aging. Al<sub>2</sub>O<sub>3</sub>-coated NCM cathode\ncan effectively reduce the growth rate of the resistance of cathode,\nwhich is benefiting from the conversion of Al<sub>2</sub>O<sub>3</sub> into LiAlO<sub>2</sub> with high ionic conductivity and the restriction\nformation of rock salt phase. Benefiting from the decreased charge\ntransfer resistance of the NCM cathode, the mismatch of the lithium-ion\nreaction kinetics is well alleviated, thus effectively reducing the\npolarization under fast charging. As a result, Al<sub>2</sub>O<sub>3</sub>-coated NCM cathode-graphite full battery shows the slow deterioration\nof charging performance during the aging process. This work provides\na promising strategy for constructing fast-charging batteries during\ncalendar aging and cycling aging.