Surface modification of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ via an ionic conductive LiV₃O₈ as a cathode material for Li-ion batteries

To improve the stability and performance of the cathode materials, an ionic conductor layer was coated successfully on the surface of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LMNC) microspheres. The structural analysis confirmed that LiV₃O₈ coating did not change the basic structure of LMNC, and all obtained materials are solid solutions with a good-layered structure and a good crystallinity. The microscopy measurement showed that the thickness of the coating layer for the LV-3 sample is about 2.5 nm. This appropriate layer is helpful for improving the surface stability of LMNC and the diffusion of lithium, leading to an obvious enhancement of the electrochemical performance. Our result confirmed that the average discharge specific capacities for LV-3 sample at 0.1 C, 0.2 C, 0.5 C, 1 C, and 3 C are respectively 265.9, 219.1, 188.0, 156.3, and 121.5 mAh g⁻¹, which are much larger than the values of other samples. After 50 cycles at a 1 C rate, the capacity retentions for different samples are 60.7%, 74.0%, 87.6%, and 70.4%, indicating that LV-3 sample exhibits the best performance. Furthermore, EIS measurements showed that the diffusion coefficient for LV-3 sample is calculated to be 1.26 × 10⁻¹⁵ cm² s⁻¹, which is also the largest value among all considered samples. Our experiments identified that coating an ionic conductive layer on the cathode material surface will significantly improve their rate capacity and cycling stability.