Improving LiNixCoyMn1-x-yO2 cathode electrolyte interface under high voltage in lithium ion batteries

The demanding for high energy density as well as high safety is still an important threshold for battery commercialization. Next-generation layered LiNixCoyMn1-x-yO2 (NCM) cathodes will meet the specific energy required for driving range of at least 300 miles from a single charge to guarantee the success of electric vehicles. Extending operating voltage of NCM cathode materials is considered as an effective way to increase energy density of lithium ion batteries. However, unstable electrode electrolyte interface (CEI) limits the electrochemical performance of NCM cathodes when operating at high voltages (>4.3 V). In this review, underlying factors and mechanisms that result in the failure to form a robust CEI are analyzed, including surface phase reconstruction, stress-induced cracking, transition metal dissolution, electrolyte decomposition and oxygen redox reaction. Then, progress on how to improve and stabilize CEI is summarized. To bridge the gap between current and next generation automotive batteries, it is expected that the situation of NCM electrode materials at high voltage to be fine-tuned with available variables such as nickel content, packaging density and loading level. Moreover, more detailed work on designing and studying a reliable CEI can help the application of NCM cathodes under high voltage.