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 LiNi0.8 Co0.15 Al0.05 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[Ni0.8 Co0.15 Al0.05 ]0.97 Ce0.03 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).