The theory guides the doping of rare earth elements in the bulk phase of LiNi0.6Co0.2Mn0.2O2 to reach the theoretical limit of energy density.

Abstract

Rare earth elements, characterized by their high-energy d-shell and f-shell electrons, large charge density, and substantial atomic radius, theoretically offer enhanced electronic states near the Fermi level. Doping rare earth elements into electrode materials can improve the internal electronic conductivity of the material. However, there are relatively few studies and reports on the mechanisms of rare earth elements in optimizing LiNi_xCo_yMn_1-x-yO₂ (NCM) materials. This study analyzes the feasibility of lanthanide doping through model construction and density functional theory (DFT) calculations. The LiNi_0.56Co_0.2Mn_0.2Ce_0.04O₂ (1/24 Ce-doped NCM622) material, guided by first-principles calculations, can even achieve an energy density of 248 mA h g^-1 as the cathode of lithium-ion batteries, which is almost the theoretical limit of the energy density of medium-content high-nickel ternary materials, reaching the level of eight-series high-nickel materials. At a rate of 0.1 C, the capacity retention rate can be 91.12 % after 300 cycles. This work introduces new development opportunities for NCM622 materials synthesized via a simple co-precipitation method in an air atmosphere and provides valuable insights into the role of rare earth elements in electrode material optimization.