Toward a high-voltage practical lithium ion batteries with ultraconformal interphases and enhanced battery safety

Nickel-rich layered lithium transition metal oxides, LiNi_xCo_yMn_1-x-yO₂, are key cathode materials for high-energy lithium–ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides is hampered by their parasitic reactions and the associated safety issues at high voltages. Developing a stable cathode–electrolyte interphase (CEI) is a promising strategy to overcome this problem. Herein, we report a novel approach, based on the in situ polymerization reaction, to build a protective polymer skin on LiNi_0.6Co_0.2Mn_0.6O₂ (NCM622) cathode materials. The artificial CEI skin was found to drastically improve the intrinsic thermal stability, mitigate the evolution of phase transition, and effectively inhibit the associated parasitic reactions between cathodes and the electrolyte in the high-charge states. This coating approach leads to enhanced capacity retention and battery safety under high-voltage operations. The CEI design concept offers a promising strategy for develop advanced nickel-rich cathodes for batteries.