Co-Doping of Al3+ and Ti4+ and Electrochemical Properties of LiNiO2 Cathode Materials for Lithium-Ion Batteries

Abstract

LiNiO₂ cathode material for lithium-ion batteries has the advantages of high specific capacity, abundant resources, and low cost, but it suffers from difficulties in preparation, structural instability, and serious capacity decay. In this work, highly pure and layered structural LiNi_0.95 Al_a Ti_0.05-a O₂ (a=0, 0.025, 0.05) cathode materials were synthesized by a simply sol-gel method. The cation mixing of Ni²⁺ and Li⁺ , structural deterioration, irreversible conversion between H2 and H3 phases and unstable surface and CEI (Cathode-electrolyte interface) film can be effectively suppressed by co-doping with Al³⁺ and Ti⁴⁺ . A preferred LiNi_0.95 Al_0.025 Ti_0.025 O₂ sample provides a discharge specific capacity of 223 mAh g^-1 at 0.1 C and 148.32 mAh g^-1 at 5 C, a capacity retention of 72.7 % after 300 cycles at 1 C and a Li⁺ diffusion coefficient of about 2.0×10^-9 cm² s^-1 .

Keywords: LiNiO2 cathode materials; co-doping with Al3+ and Ti4+; electrochemical properties; lithium-ion batteries; phase transition.