Effects of transition metal doping on electrochemical properties of single-crystalline LiNi_0.7Co_0.1Mn_0.2O₂ cathode materials for lithium-ion batteries

Layer Ni-rich cathode material has been attracted much attention due to its high energy density. A critical challenge of Ni-rich LiNi_1−x-yCo_xMn_yO₂ systems is the severe capacity fading and poor rate capability due to the structural degradation during lithium-ion battery (LIB) cycle process. In this study, we employ a fast screening methodology to determine the effects of doping single-crystalline LiNi_0.7Co_0.1Mn_0.2O₂ with cations Nb⁵⁺, Sr²⁺, Y³⁺, and then focus on the effects of Nb-ion doping on the structural stabilization (Nb-NCM). Nb ions doping and single crystallization are applied for LiNi_0.7Co_0.1Mn_0.2O₂ (Nb-NCM), which enhance the structural stability and upgrade the electrochemical performance. Impressively, the modified Nb-NCM material shows remarkably cycling at the rate of 1 C (3.0–4.5 V) with a capacity retention of 80.1% after 200 cycles. Even at high temperatures (45 ℃), the structure of Nb-NCM also remains stable, which has a capacity of 149.8 mA h g⁻¹ at 1 C (3.0–4.5 V) after 100 cycles. Further studies reveal that the successful doping of Nb-ion effectively inhibits cation mixing degree and structural degradation, and increases the diffusion coefficient of lithium-ion, which is the key to obtain the excellent electrochemical performance for LIBs. The present work indicates that the method of Nb-ion doping single-crystalline particles is an effective strategy to improve the stability of layered structure of Ni-rich NCM cathode material, and it represents an improve advance in the development of outstanding performance lithium-ion batteries.