Elevated Li+ diffusivity in Ni-rich layered oxide by precursor pre-oxidation

Abstract

Ni-rich layered oxide possesses a high theoretical capacity, high working voltage, and low cost; hence, categorized as a potential cathode material for high energy-density Li-ion batteries (LIBs). However, poor cycling performance, voltage fading, and thermal instability are some major issues that need to be addressed. Herein, a successful synthesis strategy is utilized to form a ternary oxide by sintering the hydroxide precursor at 500 °C for 6 h, followed by the lithiation of oxide under different sintering temperatures. The precursor pre-oxidation mitigates the cation mixing, removes residual lithium compounds, and enhances Li+ transportation. Moreover, the influence of sintering temperature on the electrochemical performance reveals that 750 °C for 15 h (NCAO-2) is the optimum temperature for oxide precursor. At this temperature, NCAO-2 holds enhanced cycling stability with retention of 89.8% after 100 cycles and 71% after 200 cycles. In contrast, the cathode synthesized with hydroxide precursor maintains 66.6% and 55.4% after 100th and 200th cycles at 1 C under the voltage range of 2.7–4.3 V. Furthermore, the rate capability, lithium diffusivity, and the thermal stability increase for oxide precursor NCAO-2. Consequently, the sintering of hydroxide precursors protects the particle from the inner to the outer surface. Hence, it is helpful to use oxide precursors to modify Ni-rich layered oxides further to attain high discharge capacity and enhanced cycling performance for their usage in high energy-density LIBs.