La2Ni0.5Li0.5O4 Modified Single Polycrystalline Particles of NMC622 for Improved Capacity Retention in High-Voltage Lithium-Ion Batteries

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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 LiNi0.6Mn0.2Co0.2O2 (NMC622) powder with a lanthanum-based oxide. A wet-chemical process and following heat-treatment at 750 °C produce K2NiF4-type La2Ni0.5Li0.5O4 nanoparticles on the surface of NMC622 particles. The La2Ni0.5Li0.5O4-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 La2Ni0.5Li0.5O4 modification are confirmed in the capacity retention cycled at 60 °C and in the discharging rate capability. The La2Ni0.5Li0.5O4-modification is highly effective on the single polycrystalline particles of Ni-rich NMC for long cycle-life and high-rate lithium-ion batteries.