Enhanced electrochemical performance of LiV2O4-coated and V4+-doped LiNi0.8Co0.1Mn0.1O2 cathode for lithium-ion batteries

In spite of the advantages of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode materials such as high energy density and high capacity, their capacity decay during cycling is still a significant problem, which are mainly due to the internal structural collapse and the surge in interfacial impedance caused by interfacial side reactions. To address these issues, wet chemical methods and annealing treatments were used to create LiV2O4-coated and V4+-doped NCM811 cathode materials. The LiV2O4 coating layer and the doped V4+ had little effect on the crystal structure of the NCM811, according to X-ray powder diffraction and Rietveld refinement studies. Scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy data all showed that the LiV2O4 layer was successfully coated on the surface of the spherical particles and some of the V4+ was successfully introduced into the bulk phase. Thanks to the ion-conducting layer, LiV2O4, the interfacial impedance was reduced while the Li+ diffusion rate was accelerated, and the V4+ doped into the bulk phase stabilizes the internal structure, significantly increasing the cycling stability and the rate performance of NCM811. In particular, when the coating amount was 0.6 wt%, the initial discharge specific capacity reached 203.5 mAh/g at 2.8-4.3 V at 0.1 C, and the retention rate was 87.6% after 100 cycles, which was 12.1% higher compared to 75.5% of the original sample. And when the rate was raised to 5 C, the original sample's capacity plummeted to only about 100 mAh/g, but the sample with 0.6 wt% of coating was still 140.9 mAh/g. Experiments confirmed that this LiV2O4 coating modification with synergistic V4+ doping provided an innovative technique for boosting the electrochemical performance of Ni-rich ternary cathode materials.