Enhanced thermal safety and rate capability of nickel-rich cathodes via optimal Nb-doping strategy

Abstract

Nickel-rich layered oxides have garnered great attention as promising cathode materials in lithium-ion batteries for their high specific capacity, rate capability and comparatively lower cost. However, the long cycling with a high current scenario is still a critical challenge, resulting from the lattice cracks and high temperature which are induced by rapid Li-ions intercalation/extraction and local heat accumulation under component voltage. Besides the deterioration of electrochemical performance, these limitations further lead to the impairment of structure or even thermal runaway for nickel-rich layered oxides. Herein, considering the superiorities of niobium element with multilevel electron orbitals and suitable atomic radius, a strategy of nickel-rich material modified by niobium-doping is proposed. The incorporated niobium forms a strong niobium-oxygen bonding, which promotes structure stability, ions diffusivity, and electron conductivity of nickel-rich cathode (LiNi0.8Co0.1Mn0.1O2). Accordingly, the niobium-doping cathode deliver the specific capacities of 166.4 mAh g−1 and 151.02 mAh g−1 after 100 cycles at 1 C and 5 C (1C = 200 mAh g−1), especially with the capacity retention of 88.90 % and 89.06 %. Moreover, the niobium-doping cathode exhibit a more stable thermal safety with a reversibility around 76.75 % after 100 cycles at 1 C under 50 ℃, whereas is only 36.03 % for blank sample. Accompanied with exploring the stabilization for crystalline structure and superficial electronic structure, a generic approach to synthesize excellent Ni-rich cathode materials is identified, accelerating their endurance application in complicated scenes, particularly at high-temperature and high-rate operation conditions.