Synergistic role of Sb doping and surface modification in high performance ultrahigh-nickel layered oxides cathode materials

Abstract

Before the ultrahigh-nickel LiNixCoyMnzO2 (NCM, x + y + z = 1, x ≥ 0.9) layered oxides are able to be used as a commercial electrode material for Li+ batteries, problems such as structural instability and capacity degradation due to repeated cycling need to be overcome. In this essay, we designed and prepared the Sb-modified LiNi0.92Co0.04Mn0.04O2 (Sb-NCM) materials, which simultaneously realize synergistic role of Sb doping and surface modification. The discharge capacity of the Sb-NCM materials is 206.0 mA h g−1 at 0.5 C between 2.7 V and 4.3 V. The capacity maintenance is 82.9 % after 125 cycles at 5 C, compared with 50.1 % of the pristine sample. It also demonstrates excellent rate performance, exhibiting the capacity at 5 C equal to 88.5 % at 0.1 C, while the pristine sample is only 83.7 %. According to the in situ X-ray diffractometer (XRD) test, the higher stability of Sb-NCM materials is mainly manifested in the strain mitigation induced by the absorption of anisotropic lattice shrinkage / extraction, which inhibits the formation of microcracks during charge-discharge test. Therefore, simultaneous Sb doping and Sb oxides coating layer are positive solution to stabilize layered structure and improve electrochemical properties.