Enhancing chemomechanical stability and high-rate performance of nickel-rich cathodes for lithium-ion batteries through three-in-one modification

Abstract

Ni-rich cathode, recognized for high specific capacities and cost-effectiveness, are deemed promising candidates for high-energy Li-ion batteries. However, these cathodes display notable structural instability and experience severe strain propagation during rapid charging and extended cycling under high voltage, hindering their widespread commercialization. To tackle this chemo-mechanical instability without compromising energy and power density, we propose an efficient modification strategy involving hexavalent metal cation-induced three-in-one modification to reconstruct the nanoscale surface phase. This strategy includes uniform W-doping, integration of cation-mixed phases, and Li₂WO₄ nanolayers on the surface of Ni-rich cathode microspheres. W-doping strengthen the bond to oxygen, thereby enhancing structural stability and suppressing oxygen loss linked to a layered-to-rock salt phase transition during deep delithiation process. Additionally, establishing a cation-mixing domain with an optimal thickness on the cathode surface enhances Li⁺ diffusivity and alleviates particle structural degradation. Moreover, Li₂WO₄ nanolayers reduce electrolyte side reactions and act as a damping medium against cycling stresses. Importantly, detailed investigations into structural changes before and after modification at varying current rates were conducted to better comprehend the rate-dependent degradation mechanism. These findings yield valuable mechanistic insights into the high-rate utilization of a viable Ni-rich cathode, ensuring prolonged service life in electric vehicles.