Enhancing\nthe Electrochemical Performance of LiNi_0.4Co_0.2Mn_0.4O₂ by V₂O₅/LiV₃O₈ Coating

Abstract

Despite\nlayered LiNi_<i>x</i>Co_<i>y</i>Mn_<i>z</i>O₂ having\ndrawn much attention for their high capacity and high energy density,\nthey still endure strong capacity decay upon prolonged cycling and\nhigh C-rates, primarily due to sluggish Li⁺ and charge-transfer\nkinetics and detrimental parasitic reactions with the electrolyte.\nTo address these issues, application of a surface-coating layer made\nof V₂O₅/LiV₃O₈ on LiNi_0.4Co_0.2Mn_0.4O₂ (V-NCM) is\npursued. Benefiting from the ionic conductivity of LiV₃O₈ and the electronic conductivity of V₂O₅, resulting in both enhanced Li⁺ diffusion and\ncharge-transfer kinetics, the coated material offers significantly\nimproved C-rate capability. Additionally, better long-term cycling\nperformance is achieved mostly due to the mitigated parasitic reactions\nat the electrode/electrolyte interface that result in lower structural\ndegradation. 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\n94.1% (10 C) capacity retention after 200 cycles. These V-NCM cells\noperate quite stably even at elevated temperature, that is, 40 and\n60 °C. The coating strategy herein reported may also be useful\nto enhance the cycling stability and C-rate capability of other layered\ncathode materials.