Enhanced Mechanical Strength and Electrochemical Performance of Core–Shell Structured High–Nickel Cathode Material

Improving capacity retention during cycling and the thermal–abuse tolerance of layered high–nickel cathode material, LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811), is a significant challenge. A series of core–shell structured cathode materials with the overall composition of LiNi_0.8Mn_0.1Co_0.1O₂ was prepared via a coprecipitation method in which the nickel–rich composition (LiNi_0.9Mn_0.05Co_0.05O₂) is the core and the manganese–rich composition (LiNi_0.33Mn_0.33Co_0.33O₂) 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.