International Journal of Energy Research, Vol.45, No.3, 3966-3978, 2021
Synthesis and electrochemical properties of cation-disordered rock-salt xLi(3)NbO(4)center dot(1-x) NiO compounds for Li-ion batteries
In this study, Li-excess cation-disordered rock-salt cathode materials, xLi(3)NbO(4)center dot(1 - x) NiO (LNNO, 0.55 <= x <= 0.7), are synthesized to explore the effect of composition on the structure and electrochemical performance using a sol-gel method for the first time. X-ray diffraction results combined with Rietveld refinements demonstrate that pure cation-disordered rock-salt structure can be obtained at x >= 0.6. The electron microscopy results of samples demonstrate the irregular particles with size of 1 to 10 mu m and rock-salt structure is further confirmed. The samples with x = 0.6, 0.65, and 0.7, respectively, exhibit the much higher reversible capacity than their theoretical Ni2+/Ni3+ capacity attributing to anionic redox reaction. The LNNO6 sample deliver the first discharge capacity 155.35 mAh/g and 82.9% capacity retention after 40 cycles. In addition, X-ray photoelectron spectroscopy analyses and dV/dQ measurements are utilized to investigate the restricted electrochemical behaviors and performances which are constrained by the competition between Ni2+/Ni3+ and O2-/O-.