Low-temperature strategy to synthesize single-crystal LiNi_0.8Co_0.1Mn_0.1O₂ with enhanced cycling performances as cathode material for lithium-ion batteries

With high reversible capacities of more than 200 mAh/g, Ni-rich layered oxides Li[Ni_xCo_yMn_1–x–y]O₂ (x ≥ 0.6) serve as the most promising cathode materials for lithium-ion batteries (LIBs). However, the anisotropic lattice volume changes linked to their α-NaFeO₂ structured crystal grains bring about poor cycle performances for conventionally produced NCM materials. To deal with these issue, single-crystal µm-sized LiNi_0.8Co_0.1Mn_0.1O₂ rods was synthesized by a hydrothermal method. Compared with conventional synthesis methods, these LiNi_0.8Co_0.1Mn_0.1O₂ rods were calcined at a low temperature with excessive lithium sources, which not only reduces the sintering temperature but also ensures the mono-dispersed micrometer-scaled particle distribution. When used as the cathode material for LIBs, the as-prepared LiNi_0.8Co_0.1Mn_0.1O₂, with ordered layered-structure and low degree of cation mixing, shows excellent electrochemical performances. When sintered at 750 °C with 50% Li-excess, the cathode material delivered an initial discharge capacity of 226.9 mAh/g with Coulombic efficiency of 91.2% at 0.1 C (1 C = 200 mA/g) in the voltage range of 2.8‒4.3 V. When charge-discharged at 1 C for 100 cycles, discharge capacity of 178.1 mAh/g with the capacity retention of 95.1% are still obtained. The cycling stability at high cut-off voltage is also outstanding. These superior electrochemical properties should be related to the monodispersed micron scaled morphology which not only decreases the contact area between electrode and electrolyte but also mitigates the formation of microcracks. This low-temperature strategy of synthesizing single-crystal LiNi_0.8Co_0.1Mn_0.1O₂ rods should be able to provide a feasible method for synthesizing other single-crystal Ni-rich cathode materials with excellent electrochemical performances for LIB.