La₂Ni_0.5Li_0.5O₄ modified single polycrystalline particles of NMC622 for improved capacity retention in high-voltage lithium-ion batteries

Ni-rich lithium nickel manganese cobalt oxides have been extensively studied as high capacity and low cost positive electrode materials for lithium-ion batteries. In order to improve their electrochemical properties, especially cycle capability, we develop a surface modification on single polycrystalline particles of LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622) powder with a lanthanum-based oxide. A wet-chemical process and following heat-treatment at 750 °C produce K₂NiF₄-type La₂Ni_0.5Li_0.5O₄ nanoparticles on the surface of NMC622 particles. The La₂Ni_0.5Li_0.5O₄-modification improves capacity retention of NMC622 during long-term charge-discharge cycling in the wide voltage range of 3.0–4.5 V at room temperature. The capacity retention at the 150th cycle is about 86% (from 182 to 157 mAh g^-1) which is higher than 78% (from 176 to 135 mAh g^-1) obtained for the unmodified NMC622 electrode. Further improvements by the La₂Ni_0.5Li_0.5O₄ modification are confirmed in the capacity retention cycled at 60 °C and in the discharging rate capability. The La₂Ni_0.5Li_0.5O₄-modification is highly effective on the single polycrystalline particles of Ni-rich NMC for long cycle-life and high-rate lithium-ion batteries.