One-Step Synthesis of a Single-Crystal LiNi0.83Co0.11Mn0.06O2 Cathode with Excellent Electrochemical Properties by Ti4+ Doping and LiTi2O4 In Situ Chemical Coating Using a Novel Variable Temperature Sintering Process

High-nickel ternary material is one of the most promising cathode materials with high energy density. However, this material has the disadvantages of poor cycling stability, poor thermal stability, and low safety. The synergetic effect of single crystal, element doping, and surface coating is an effective way to improve its electrochemical performance. In this work, the particle size of the single-crystal LiNi0.83Co0.11Mn0.06O2 (NCM811) material was controlled by LiCl–KCl flux, and the internal/external synergy of Ti4+ doping and LiTi2O4 coating was realized by the pretreatment of Ti(OC4H9)4 and a subsequent new temperature-changing sintering process. The single-crystal structure greatly improved the crushing of material, the Ti4+ doping effectively broadened the lattice spacing and stabilized the layered structure, and the uniform LiTi2O4 coating effectively eliminated excess lithium salts and promoted the stability of the interface structure. The electrochemical test results showed that the modified materials had excellent electrochemical properties, especially a high lithium-ion diffusion rate and high cycle stability. Therefore, it will provide a solid technical support for the synthesis of high-performance single-crystal high-nickel ternary cathode materials.