Improved electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode material for Lithium-ion batteries by using pre-oxidation of K2Cr2O7

Abstract

The precursor was pre-oxidized with K2Cr2O7 as oxidant, and Ni2+ on the surface was immediately oxidized to Ni3+, resulting in a more ordered surface structure of the precursor. It was found by XRD and SEM that the precursor pre-oxidation did not produce new phase, the surface morphology of the synthesized material did not change obviously, and the degree of cation confusion was reduced. After K2Cr2O7 pre-oxidation of the precursor, the electrochemical properties of the samples were greatly improved. In particular, the sample with 1 % K2Cr2O7 content had the best performance. After 50 cycles at 1 C and 3–4.3 V, the capacity can still retain 177.7 mAh g−1, and the capacity retention rate was as high as 99.1 %. After 50 cycles, the capacity was only 161.6 mAh g−1, and the capacity retention rate was 96.6 %. When charged to a high voltage of 4.5 V, the NCM-1 can derive a discharge capacity of 200.9 mAh g−1, which retained 173.2 mAh g−1 after 50 cycles, while the pristine had 165 mAh g−1 after 50 cycles. There was also a decrease in Ni2+ content, which reduced the degree of cation confusion and increased the kinetics of charge transfer and lithium ion diffusion.