Pr doped single-crystal LiNi_0.5Mn_0.3Co_0.2O₂ cathode enables high rate capability and cycle stability for lithium ion batteries

The massive application of single crystal (SC) ternary cathode material LiNi_1-x-yMn_xCoO₂ is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li⁺ diffusion and structural instability. Herein, Pr³⁺, a large radius ion is introduced to single-crystal LiNi_0.5Mn_0.3Co_0.2O₂ to enhance Li ⁺ conductivity and structural stability. With 0.4% Pr doping, the Li(Ni_0.5Mn_0.3Co_0.2)_0.996Pr_0.004O₂ cathode displays a capacity retention of 79.72% at 10 C, and a 98.17% capacity retention after 50 cycles at 25 ℃ and 96.3% capacity retention after 50 cycles at 55 ℃ within a 3.0–4.5 V voltage window. Electrochemical impedance spectroscopy confirms that the Pr doping can effectively lower the charge-transfer resistance and facilitate the transportation of Li⁺ on the surface of LiNi_0.5Mn_0.3Co_0.2O₂. The Direct current internal resistance result implies that the structure of the Pr-doped cathode particles is more stable during cycling. In addition, differential scanning calorimetry measurements measurement combined with in situ X-ray diffraction confirms the thermo-stabilization effect of the Pr dopant.