Enhancing the Structural Stability and Cycling Performance of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ Cathode Material by Al ³⁺ Ion Doping

ABSTRACT High‐nickel ternary materials are considered as promising cathode materials for lithium‐ion batteries, primarily due to their high specific capacity and energy density. However, the crystal structure of high‐nickel cathode materials undergoes significant changes during charge and discharge cycles. The accumulated stress leads to the formation and growth of microcracks along the inter‐particle boundaries, ultimately compromising particle integrity. Repeated volume contractions and expansions eventually cause further pulverization of the material. In this study, Al ³⁺ ion doping was employed to stabilize the layered structure of the high‐nickel ternary materials. Al ³⁺ ‐doped LiNi _0.8 Co _0.1 Mn _0.1 O ₂ was synthesized by a one‐step solid‐state sintering method. The characterization confirmed that Al ³⁺ ions were successfully doped into the transition metal layers of the cathode material and formed stronger Al─O covalent bonds, which enhanced the stability of the bulk phase structure, suppressed phase transition, and microcracks. The cathode material doped with 1.5 mol.% Al ³⁺ exhibited excellent cycling stability, with a capacity retention rate increased by 15.01% after 600 cycles compared to the pristine specimen. In addition, Al ³⁺ doping reduces cation mixing and optimizes ion transport kinetics, the discharge capacity reached 145.5 mAh·g ⁻¹ at 10 C rate. Therefore, achieving Al ³⁺ ion doping through co‐lithium sintering provides an effective strategy for improving the performance of high‐nickel cathode materials in lithium‐ion batteries.