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Enhancing the Electrochemical Performance of LiNi₀.₄Co₀.₂Mn₀.₄O₂ by V₂O₅/LiV₃O₈ Coating

Chen, Zhen, Wang, Zeli, Kim, Guk-Tae, Yang, Guang, Wang, Huanhuan, Wang, Xuesen, Huang, Yizhong, Passerini, Stefano, Shen, Zexiang
ACS applied materials & interfaces 2019 v.11 no.30 pp. 26994-27003
cathodes, coatings, electrochemistry, electrolytes, energy density, lithium, temperature
Despite layered LiNiₓCoyMnzO₂ having drawn much attention for their high capacity and high energy density, they still endure strong capacity decay upon prolonged cycling and high C-rates, primarily due to sluggish Li⁺ and charge-transfer kinetics and detrimental parasitic reactions with the electrolyte. To address these issues, application of a surface-coating layer made of V₂O₅/LiV₃O₈ on LiNi₀.₄Co₀.₂Mn₀.₄O₂ (V-NCM) is pursued. Benefiting from the ionic conductivity of LiV₃O₈ and the electronic conductivity of V₂O₅, resulting in both enhanced Li⁺ diffusion and charge-transfer kinetics, the coated material offers significantly improved C-rate capability. Additionally, better long-term cycling performance is achieved mostly due to the mitigated parasitic reactions at the electrode/electrolyte interface that result in lower structural degradation. As a result, Li/V-NCM cells deliver over 100 mA h g–¹ capacity at 10 C and also achieve 86.1% (2 C) and 94.1% (10 C) capacity retention after 200 cycles. These V-NCM cells operate quite stably even at elevated temperature, that is, 40 and 60 °C. The coating strategy herein reported may also be useful to enhance the cycling stability and C-rate capability of other layered cathode materials.