Constructing Perovskite Phase to Enhance the Electrochemical Performance of a Cobalt-Free, Ultrahigh-Ni Cathode

Developing cobalt-free, ultrahigh-Ni cathode materials holds great significance for the sustainable advancement of lithium-ion batteries. However, ultrahigh-Ni cathodes without cobalt often suffer from severe Li+/Ni2+ mixing, which leads to poor Li+ diffusion kinetics and structural instability. Although the introduction of high-valent Mo6+ into the cobalt-free layered structure has been considered an effective strategy to optimize Li+ diffusion channels and dissipate the intergranular strain, it still cannot thoroughly resolve the anisotropic strain within the lattice. Herein, a distinctive in situ strategy is adopted to introduce La3+ into the precursor during the coprecipitation process; the perovskite phase (La4(LiMn)O8) is grown coherently within the layered lattice of LiNi0.9Mn0.08Mo0.02O2 (NMM) during the subsequent lithiation process. Structurally stable La4(LiMn)O8 significantly restrains the Li+/Ni2+ mixing, enlarges the Li-O interlayer spacing, and mitigates the intrinsic lattice strain by alleviating the H2 → H3 hexagonal phase transition. Thanks to these comprehensive structural advantages, the as-fabricated La-NMM cathode with the La4(LiMn)O8 demonstrates a reversible specific capacity of 176 mA h g-1 at 5 C and retains 90% capacity after 100 cycles at 0.5 C. This in situ strategy broadens the prospects of phase engineering and provides design ideas for the development of practical cobalt-free, ultrahigh-Ni cathode materials.