Synergistic doping strategy for enhancing the electrochemical performance of NCM811 cathodes using B, Zr, and Ti

Element doping is one of the practical methods to solve the defects of nickel-rich ternary materials with poor structure stability, fast capacity decay, and poor rate performance. Three elements of B, Zr, and Ti were applied here to modify the commercial precursor NCM811 using a one-step solid-phase method. The optimal sintering temperature, duration, and elemental ratios for the single-element doping were systematically investigated. Furthermore, the synergistic effect of ternary doping with B, Zr, and Ti on the cathode crystal structure and electrochemical performance were explored at different doping ratios based on their original optimal adding amounts. It was found that the optimized amounts of three-element co-doping were only 1/10 of their optimal ratios for single-element doping. The optimal multi-element doping sample exhibited superior rate performance, and the discharged capacity can reach 1.64 times that of their individual superimposed counterparts at 5C. The potential mechanism of the synergistic modification is that excessive accumulation of doping elements can form a barrier to weaken the kinetics of lithium-ion diffusion, and some competitive influences rather than complete superimposed effects play an important role in multi-element co-modification. Therefore, a particular perspective on multi-element doping was proposed here to address the shortcomings of nickel-rich cathode materials, providing some guidance for commercial cathode material modification.