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 + /Ni 2+ mixing, which leads to poor Li + diffusion kinetics and structural instability. Although the introduction of high-valent Mo 6+ 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 La 3+ into the precursor during the coprecipitation process; the perovskite phase (La 4 (LiMn)O 8 ) is grown coherently within the layered lattice of LiNi 0.9 Mn 0.08 Mo 0.02 O 2 (NMM) during the subsequent lithiation process. Structurally stable La 4 (LiMn)O 8 significantly restrains the Li + /Ni 2+ 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 La 4 (LiMn)O 8 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.