Aluminium Doping to Single-Crystal Nickel-Rich Cathodes: Insights into Electrochemical Degradation and Enhancement

Abstract

Single-crystal nickel-rich cathode materials are considered ones of the most promising candidates for automobile Li-ion batteries due to their high compacted density and superior cycling stability. Herein this work, we conduct a comparative study of single-crystal Ni-rich ternary NCM and quaternary NCMA with aluminum doping, and it is found that Al doping applied to quaternary NCMA sample can maintain superior electrochemical performance with the significantly reduced direct current resistance (DCR). In contrast, the ternary NCM samples demonstrate a notable capacity decay to only 76.7% after 100 cycles at 2.75-4.3V, compared to 85.9% of the NCMA. Synchrotron-based characterizations combined with high-resolution transmission electron microscopy unravel that the surface microstructural and bulk structural stability has been greatly enhanced after Al doping thereby substantially reducing DCR and improving the operational lifespan and efficiency of the batteries. It is hoped this work should provide deep understanding in electrochemical degradation and enhancement mechanism of the single-crystal Ni-rich cathodes, offering critical insights into the development of high-energy-density cathodes materials for the next-generation lithium-ion batteries.