Effect of fast charging on degradation and safety characteristics of lithium-ion batteries with LiNi x Co y Mn z Al 1- x- y- z O 2 cathodes

Fast charging compatibility is an important technical aspect required of advanced lithium-ion (Li-ion) batteries to lead the revolution and increase the adoption of electric vehicles. Although substantial material-level innovations have greatly promoted the widespread employment of fast charging rates for Li-ion batteries, the unfavorable rapid degradation and cell-level thermal instability are still bottlenecks for commercial success. In this study, fast-charging induced aging mechanisms and thermal safety characteristics of Li-ion batteries with quaternary energy-dense LiNixCoyMnzAl1-x-y-zO2 (NCMA) cathodes are comprehensively investigated. Promising fast-charge strategies under different thermal environments are applied to reveal their specific adverse side effects on electrochemical performances and cell lifetime. Post-mortem analysis is conducted to understand the distributions, microstructures, and chemical states of electrodepositions on cell components. Cell-level thermal safety evaluations are carried out based on accelerating rate calorimeter tests to determine evolutions of thermal safety hazards as a result of imposed fast charging conditions. This research highlights the significant role of lithium plating and aluminum dissolution in accelerating the thermo-electrochemical failure of the chosen NCMA-based Li-ion chemistry, providing new insights on degradation-safety interactions and effective mitigation strategies under fast charging conditions.