Induction and Maintenance of Local Structural Durability for High‐Energy Nickel‐Rich Layered Oxides

Abstract

Nickel-rich layered oxides are one of the most promising cathode candidates for next-generation high-energy-density lithium-ion batteries. However, due to similar ion radius between Li⁺ and Ni²⁺ (0.76 and 0.69 Å), the Li⁺ /Ni²⁺ mixing phenomenon seriously hinders the migration of Li⁺ and increases kinetic barrier of Li⁺ diffusion, resulting in limited rate capability. In this work, the introduction of Ce⁴⁺ to effectively improve electrochemical properties of Ni-rich cathode materials is proposed. The LiNi_0.8 Co_0.15 Al_0.05 O₂ (LNCA) is modified with an additional precursor oxidization process using an appropriate amount of (NH₄ )₂ Ce(NO₃ )₆ . The Ce(NO₃ )₆ ^2- easily obtains electrons and generates reduction reactions, while Ni(OH)₂ is prone to electron loss and oxidation reaction. The participation of (NH₄ )₂ Ce(NO₃ )₆ can promote the oxidation of Ni²⁺ to Ni³⁺ , thereby reducing the Li⁺ /Ni²⁺ mixing and increasing the structural stability of LNCA samples. Ce⁴⁺ cation doping can impede Li⁺ /Ni²⁺ mixing of LNCA cathode materials upon the long-term cycles. Both rate performance and long-term cyclability of Li[Ni_0.8 Co_0.15 Al_0.05 ]_0.97 Ce_0.03 O₂ (LNCA-Ce0.03) sample are significantly improved. Besides, a practical pouch cell based on the cathode presents sufficient gravimetric energy density (≈300 Wh kg^-1 ) and cycling stability (capacity retention of 81.3% after 500 cycles at 1 C).