Enhanced electrochemical performance of ultra-high nickel cathode through Hf doping for lithium-ion batteries

High-energy-density lithium-ion batteries with ultra-high nickel cathode (UH-NCM, LiNi _xCo _yMn _1-x-yO ₂, x>0.9) are suitable power sources for electric vehicles. Nevertheless, UH-NCM cathode suffers from the poor cycle and rate performance caused by the collapse of layered structure at deep delithiation. Here we present a Hf ⁴⁺ doping strategy to improve cycle and rate performance of UH-NCM cathodes simultaneously. Experiments and density functional theory (DFT) based calculations reveal the effectivity on stabilizing the layered structure via injecting foreign Hf ⁴⁺. The pristine LiNi _0.95Co _0.025Mn _0.025O ₂ cathode exhibits a capacity retention of 65.1 % after 100 cycles at 1 C, while the optimal 1 mol% Hf ⁴⁺ doped UH-NCM cathode maintains 84.5 % under the same condition. Moreover, the specific discharge capacity of Hf ⁴⁺ doped cathode increases from 106.3 mAh/g to 121.5 mAh/g at 10 C. This work provides a simple approach for enhancing the electrochemical performance of UH-NCM.