Constructing electrochemically stable single crystal Ni-rich cathode material via modification with high valence metal oxides

Abstract

Single crystal Ni-rich cathode materials (SCNCM) are a good supplement in the market of nickel-based materials due to their safety and excellent electrochemical performance. However, the challenges of cation mixing, phase change during charge/discharge, and low thermal stability remain unresolved in single crystal particles. To address these issues, SCNCM are rationally modified by incorporating transition metal (TM) oxides, and the influence of metal ions with different valence states on the electrochemical properties of SCNCM is methodically explored through experimental results and theoretical calculations. Enhanced structural stability is demonstrated in SCNCM after the modifications, and the degree of improvement in the matrix materials varies depending on the valence state of doped TM ions. The highest structural stability is found in WO₃-modified SCNCM, due to the smaller effective ion radii, higher electro-negativity, stronger W–O bond, and efficient suppression of oxygen vacancy generation. As a result, WO₃-modified SCNCM have outstanding cycle performance, with a capacity retention rate of 90.2% after 200 cycles. This study provides an insight into the design of advanced SCNCM with enhanced reversibility and cyclability.