A morphology-disorder dual parameter to design Ni-rich layered cathode materials

Ni-rich layered cathode materials are promising for high-energy-density lithium-ion batteries; however, their severe capacity degradation hampers large-scale applications. While metal doping has emerged as a viable strategy to enhance structural stability, the reported effects of dopants remain controversial, primarily due to differences in synthesis conditions and precursor reactivity. Herein, we propose a dual-parameter strategy integrating primary particle morphology and Li/Ni disorder across a broad sintering temperature range (700–900 °C). Under this strategy, LiNi_0.90Co_0.06Mn_0.04O₂ (NCM90) cathode materials achieve optimal structural and electrochemical performance with two exemplary dopants (1 mol% Nb and W). However, the optimized sintering temperature for Nb-NCM90 cathode materials is 750 °C, whereas W-NCM90 require 850 °C. Detailed morphological analysis reveals that a critical primary particle density governs capacity retention. Below the critical primary particle density (33.82 particles per μm² for the Nb-NCM90 and 11.69 particles per μm² for the W-NCM90), all cathode materials exhibit excellent capacity retention due to limited strain building up during cycling, but low reversible capacity associated with severe Li/Ni disorder. In contrast, above the critical primary particle density, these cathode materials demonstrate rapid capacity fading attributed to high strain accumulation during cycling, despite high initial capacity associated with low Li/Ni disorder. These findings highlight the synergistic interplay between primary particle density and Li/Ni disorder in achieving both high-capacity retention and reversible capacity.