Dual modification of LiNi _0.83 Co _0.11 Mn _0.06 O ₂ cathode materials by K ⁺ doping and Li ₃ PO ₄ coating for lithium ions batteries

Abstract

Abstract Li 3 PO 4 @Li 0.99 K 0.01 Ni 0.83 Co 0.11 Mn 0.06 O 2 (NCM‐KP) cathode powders are synthesized via K + doping in calcination processes and H 3 PO 4 coating in sol–gel processes. K + precisely enters into the lattice to widen the (003) plane to 0.4746 nm with a lower cationic disordered degree of 1.87%. Moreover, the surface residual lithium salts are treated by H 3 PO 4 to generate a uniform Li 3 PO 4 coating layer of approximately 11.41 nm, which completely covers on the surface of secondary spherical particles to improve the interfacial stability. At 25 °C, the NCM‐KP electrode delivers a discharge specific capacity of 148.9 mAh·g −1 with a remarkable capacity retention ratio of 84.1% after 200 cycles at 1.0C and retains a high reversible specific capacity of 154.4 mAh·g −1 at 5.0C. Even at 1.0C and 60 °C, it can maintain a reversible discharge specific capacity of 114.6 mAh·g −1 with 0.21% of capacity decay per cycle after 200 cycles, which is significantly lower than 0.40% for the pristine NCM powders. Importantly, the charge transfer resistance of 238.89 Ω for the NCM‐KP electrode is significantly lower than 947.41 Ω for the pristine NCM one by restricting the interfacial side reactions. Therefore, combining K + doping and Li 3 PO 4 coating is an effective strategy to enable the significant improvement of the electrochemical property of high‐nickel cathode materials, which may be mainly attributed to the widened diffusion pathway and the formed Li 3 PO 4 protective layer, thus promoting Li + diffusion rate and preventing the erosion of HF.