Improving structure stability and electrochemical properties of Hf-doped Ni-rich layered cathode materials via dual-pillar effect

The Hf-doped Li[Ni 0.8- x Hf x Co 0.1 Mn 0.1 ]O 2 ( x  = 0–0.04) materials were synthesized by the co-precipitation process combined with high-temperature solid-state reaction. First-principles calculations and Rietveld refinement confirm that Hf doping induces dual-pillar effect by forming more stable HfO 6 octahedrons in the transition metal layers and more NiO 6 octahedrons in the lithium layers, which collectively stabilize the layered structure. Moreover, Hf doping facilitates lithium-ion transport by lowering the diffusion energy barrier and enhances the electronic conductivity of Hf-doped NCMs by reducing the band gap. The 2 mol% Li[Hf 0.02 Ni 0.78 Co 0.1 Mn 0.1 ]O 2 cathode delivers a specific discharge capacity of 205.1 mAh g −1 at 20 mA g −1 and presents an impressive capacity retention of 87.0 % after 100 cycles at 200 mA g −1 at room temperature, with 13.6 % higher than the pristine cathode. At 1 A g −1 charge/discharge current density, the 2 mol% Hf-doped cathode achieves a discharge capacity of 142.4 mAh g −1 . These results further demonstrate the effectiveness of dual-pillar effect in constructing stable layered microstructure, significantly improving cycling stability and high-rate performance.