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

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.