| Summary: | Spinel Li<sub>4</sub>Mn<sub>5</sub>O<sub>12</sub> was successfully prepared by the wet chemical method to modify the surface of Li<sub>1.2</sub>Ni<sub>0.2</sub>Mn<sub>0.6</sub>O<sub>2</sub>. The results showed that an ultrathin spinel Li<sub>4</sub>Mn<sub>5</sub>O<sub>12</sub> surface-modified layer with a thickness of approximately 10 nm was successfully constructed on the raw material surface, and that the cationic order was improved. In addition, the lithium ion diffusion coefficients (D<sub>Li</sub><sup>+</sup>) of the raw materials and the modified materials were calculated using the EIS test and impedance fitting. The results indicated that the ultrathin Li<sub>4</sub>Mn<sub>5</sub>O<sub>12</sub> surface modification shell can increase the lithium ion diffusion rate of the material and improve the rate capability of the material. So, the surface modification layer of spinel Li<sub>4</sub>Mn<sub>5</sub>O<sub>12</sub> can reduce the oxygen loss of the first cycle and improve the cationic order of the material. Therefore, the first coulombic efficiency of Li<sub>4</sub>Mn<sub>5</sub>O<sub>12</sub>/Li<sub>1.2</sub>Ni<sub>0.2</sub>Mn<sub>0.6</sub>O<sub>2</sub> material at the current density of 12.5 mA·g<sup>−1</sup> reaches 80.46%, and the capacity retention rate reaches 91.74% after 50 cycles, which are 3.36% and 21.23% higher than those of the raw materials, respectively. It showed better electrochemical reversibility and cyclic stability. This study provides a straightforward and convenient modification method for improving the stability of cobalt-free lithium-rich manganese cathode materials and has a favorable application prospect.
|
|---|