Surface Modification and Electrochemical Properties of Cobalt-Free Lithium-Rich Manganese-Based Cathode Material Li1.2Ni0.2Mn0.6O2
Cobalt-free lithium-rich manganese-based cathode materials have attracted much attention as potential next-generation cathode materials for lithium-ion batteries due to their high specific capacity and low-cost advantages.However,problems such as low first-cycle Coulombic efficiency,poor rate performance,and capacity attenuation limit the further development of cobalt-free lithium-rich manganese-based cathode materials.A spinel phase was successfully coated on the surface of cobalt-free Li1.2Ni0.2Mn0.6O2 cathode material by the method of surface treatment with citric acid and then re-calcination.The physical characterization and electrochemical test analysis were carried out on the samples before and after modification.The results show that the morphology of cobalt-free Li1 2Ni0.2Mn0 6O2 cathode material before and after modification is basically the same,which is irregular particles with the size of 100-400 nm.The modified powder particles have slightly uneven edges.The surface treatment of cobalt-free lithium-rich manganese cathode material Li1.2Ni0.2Mn0.6O2 with citric acid solution formed a structure with layered phase inside and spinel phase on the surface.The presence of spinel phase not only provides a three-dimensional ion diffusion channel for lithium ion diffusion,but also improves the rate performance.It can also act as a protective layer between the material surface and the electrolyte to improve the first coulomb efficiency and improve the cycle performance.The first coulomb efficiency and reversible specific capacity of the modified Li1.2Ni0.2Mn0.6O2 are 92.4％and 292 mAh·g-1,respectively,which are 13.8％and 22 mAh·g-1 higher than those before modification,and the reversible specific capacity and long-cycle capacity retention rate are significantly improved at different magnifications.It shows that it has better rate performance and cycle stability performance.The modification method is simple and effective,and can be applied to different components of Li-rich cathode materials.It provides a new idea for the further development of Li-rich manganese-based cathode materials.
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