Enhanced mechanical strength and electrochemical performance of core-shell structured high-nickel cathode material

摘要

Improving capacity retention during cycling and the thermal-abuse tolerance of layered high-nickel cathode material, LiNi0.8Mn0.1Co0.1O2 (NMC811), is a significant challenge. A series of core-shell structured cathode materials with the overall composition of LiNi0.1Mn0.1Co0.1O2 was prepared via a coprecipitation method in which the nickel-rich composition (LiNi0.9Mn0.05Co0.05O2) is the core and the manganese-rich composition (LiN10.33Mn0.33Co0.33O2) is the shell. In terms of achieving a higher nickel content (more than 80%) of heterogeneous material, this core-shell structured material is a more practical approach because it has a larger nickel-rich core region and a thicker manganese-rich shell than the full-concentration gradient material, not to mention being more feasible for continuous mass production. Analysis of mechanical strength through nanoindentation shows that the core-shell structured NMC811 has higher stiffness and compressive stress-strain than the commercial homogeneous NMC811 and retains the mechanical strength and the binding force strong enough to prevent crack formation even after 200 cycles. The prepared core-shell structure NMC811 exhibits a greatly improved capacity retention of 76.6% compared to the commercial homogeneous NMC811 with a capacity retention of 39.6% after 200 cycles. This material also exhibits significantly improved thermal stability over the commercial homogeneous NMC811.