A Concentration Gradient Approach to Enhance Mechanical and Electrochemical Stability in Ni-rich Cathode Materials for Long-Lasting Lithium-Ion Batteries

Fracturing plays a major role in the degradation of electrochemical performance of Ni-rich cathode materials during successive cycles. However, mechanical properties of the cathode materials such as hardness and fracture strength, which closely correlate with cracks formation, have not been intensively studied. Here, we introduce a concentration gradient structure with Ni-rich core and Mn-rich shell. Based on this approach, the radially aligned primary particles formed with spoke- like microstructure, which contributes to the improved hardness and fracture strength. Benefiting from the mechanical stable structure, the concentration gradient cathode can withstand the accumulated strain originated from lattice changes and fatigue destruction during repeated cycles, and thus presents less fractures, which effectively inhibiting the parasitic reaction between electrolyte and cathode through cracks. As a result, the electrochemical stability of the modified material was significantly improved. This work gives a feasible way to improve the mechanically stable Ni-rich cathode for lithium-ion batteries with high energy density.