Surface-Functionalized Coating for Lithium-Rich Cathode Material To Achieve Ultra-High Rate and Excellent Cycle Performance.

Abstract

Although the lithium-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2, as a promising cathode material, has a high specific capacity, it suffers from capacity decay and discharge voltage decay during cycling. In this work, the specific capacity and discharge voltage of Li1.2Mn0.54Ni0.13Co0.13O2 are stabilized by surface-functionalized LiCeO2 coating. We have conducted LiCeO2 coating via a mild synchronous lithium strategy to protect the electrode surface from electrolyte attack. This optimized LiCeO2 coating has high Li+ conductivity and abundant oxygen vacancies. The results demonstrate that 3% LiCeO2-coated Li1.2Mn0.54Ni0.13Co0.13O2 exhibits the highest capacity retention rate at 1, 2, and 5 C after 200 cycles, which were 84.3%, 85.4%, and 86.3%, respectively. The discharge specific capacity was almost 1.3, 1.4, and 1.4 times that of the pristine electrode. In addition, the 3% LiCeO2 electrode exhibited the least voltage decay of 0.409, 0.497, and 0.494 V at 1, 2, and 5 C, which was only about half of the pristine electrode. It should not be overlooked that the 3% LiCeO2 electrode still exhibits a high capacity at high current densities of 1250 mA g-1 (5 C) and 2500 mA g-1 (10 C), and its specific discharge capacities are 190.5 and 160.6 mAh g-1, respectively. These outstanding electrochemical properties benefit from surface-functionalized LiCeO2 coatings. To better understand the mechanism of oxygen loss of lithium-rich materials, we propose the lattice oxygen migration path of the LiCeO2-coated electrodes during the cycle. Our research provides a possible solution to the poor rate capability and cycle performance of cathode materials through surface-functionalized coatings.