Enhancement of the cycling stability of the nickel-rich cathode material LiNi _0.9 Co _0.01 Mn _0.09 O ₂ <i>via</i> Nb ⁵⁺ doping

LiNi_<i>x</i>Co_<i>y</i>Mn_{1-<i>x</i>-<i>y</i>}O₂ cathode materials have long been recognized as one of the most promising candidates for lithium-ion batteries. In order to increase their production capacity and reduce costs, NCM cathode materials are currently being developed in the direction of high nickel and low cobalt contents. However, these cathodes face serious challenges, such as structural instability, capacity loss, and poor rate capability. Despite extensive research, problems such as structural degradation and capacity loss under high-voltage conditions remain unresolved. In this work, we successfully prepared Nb⁵⁺-doped LiNi_0.9Co_0.01Mn_0.09O₂ cathodes by incorporating Nb₂O₅ into Ni_0.9Co_0.01Mn_0.09(OH)₂ precursor powders. Nb⁵⁺ doping not only expanded the spacing of lithium layers, facilitating the diffusion of lithium ions, but also led to the formation of Nb-O bonds, enhancing structural stability and improving cycle performance. Electrochemical tests indicated that at a doping ratio of 1%, the first discharge specific capacity of the modified sample was 178.55 mAh g^-1 at 1.0C, with a capacity retention of 92.69% after 100 cycles. Furthermore, the initial discharge specific capacity of the NCM-1.0Nb sample was up to 215.58 mAh g^-1 at high voltages of 2.5-4.5 V, while after 100 cycles, it was 188.73 mAh g^-1, with a cycle retention rate of 87.54%. The electrochemical cycling performance of NCM was thus significantly improved after Nb⁵⁺ doping. Therefore, appropriate Nb⁵⁺ doping is a convenient and effective modification approach to obtain nickel-rich cathodes with excellent performance.