Improving the electrochemical properties of Li1.2Mn0.52Co0.08Ni0.2O2 cathode material by uniform surface nanocoating with samarium fluoride through depositional-hydrothermal route

Abstract

Surface nanocoating of lithium-rich layered Li1.2Mn0.52Co0.08Ni0.2O2 with samarium fluoride (SmF3) has been performed through a chemical deposition route combined with a low-temperature hydrothermal treatment. The surface-modified Li1.2Mn0.52Co0.08Ni0.2O2 particles are uniformly and completely covered by an amorphous SmF3 protective layer with a thin thickness of ∼20nm. After surface modification, the coated Li1.2Mn0.52Co0.08Ni0.2O2 as cathode shows a significantly improved cycling stability, keeping a capacity retention of 84.5% after 150 cycles at 2C, much higher than 68.9%forits uncoated counterpart. Moreover, the coated sample delivers an enhanced rate capability with an average capacity of ∼132.3mAhg−1 when charged at 5C and discharged at 0.2C, while the uncoated counterpart only exhibits a capacity of ∼111.4mAhg−1 under the same conditions. Our results reveal that the remarkably improved electrochemical performance of the surface-modified cathode is attributed to the presence of uniform, robust, and nanoscale SmF3 coating layer, which not only suppresses the growth of SEI layer by reducing the side reaction between cathode and electrolyte solution, but also strengthens the structure stability of the Li-rich layered cathode materials.