Dual-Functional Tungsten Boosted Lithium-Ion Diffusion and Structural Integrity of LiNi₀.₈Co₀.₁Mn₀.₁O₂ Cathodes for High Performance Lithium-Ion Batteries
2021
Zhu, Zhenhua | Gao, Aimei | Liang, Yansheng | Yi, Fenyun | Meng, Tao | Ling, Jingzhou | Hao, Junnan | Shu, Dong
In this work, a series of LiNi₀.₈Co₀.₁Mn₀.₁O₂ oxides with dual-functional heterostructure are acquired from a trace tungsten (W) modification strategy; such a heterostructure contains a gradient tungsten distribution structure and a fast ion-conductive LiₓWOy coating layer that are in situ formed via thermodynamic diffusion during the calcination process. The gradient doping can increase the lattice parameters because of the large radius of tungsten, then further to expand interlayer spacing and facilitate the lithium-ion diffusion coefficient which can enhance the capacity and rate performance. Besides, the strong W–O bonds can improve the stability of the lattice and promote the structural integrity and thermostability. Meanwhile, the fast ion-conductive LiₓWOy layer can not only facilitate the rate of Li⁺ deintercalation, but also act as a defensive layer to suppress side reactions and then improve the cycling property. As a result of the dual-functional heterostructure, the W-modified LiNi₀.₈Co₀.₁Mn₀.₁O₂ with the mass fraction of 4500 ppm (W4500) shows a superior discharge capacity of 165.5 mAh g–¹ at 5.0 C and an enhanced cycle retention of 88.4% (25 °C) after 100 cycles. Especially, the positive electrode of W4500 delivers a better structural integrity than that of pristine. The investigation elaborates the characters of the dual-functional tungsten modification and offers a path to prepare better Ni-rich layered oxides for lithium-ion batteries.
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