Constructing Perovskite Phase to Enhance the Electrochemical Performance of a Cobalt-Free, Ultrahigh-Ni Cathode
Futong Ren, Guiquan Zhao, Yongjiang Sun, Hang Ma, Wenjin Huang, Yunchun Zha, Lingyan Duan, Genfu Zhao, Qing Liu, Qi An, Xiaoxiao Zou, Hanlin Tang, Pujia Cheng, Hong Guo
Abstract
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.