V2O3@C optimized by carbon regulation strategy for ultra long-life aqueous zinc-ion batteries

The V2O3@C nanospheres, synthesized by a carbon reduction reaction process, have excellent electrochemical properties, which can be due to the outstanding electrical conductivity and mechanical properties of carbon shell. [Display omitted] •The core-shell V2O3@C nanospheres were obtained by carbon reduction reaction.•The thickness of the carbon shell can be adjusted by changing the calcination temperature.•The thickness of the carbon shell also affecting the electrochemical performance.•The obtained V2O3@C exhibits ultra-high long-cycle performance.•The charge-discharge mechanism and electrochemical kinetics of the electrode were studied. Aqueous zinc-ions batteries (AZIBs) are expected to be a new green energy storage devices due to the low cost and safety. As classic cathode materials for AZIBs, layered vanadium oxides have excellent redox activity and large capacity performance. However, it not only has poor conductivity, but easily dissolved during (dis)charge process. Therefore, it is necessary to modify vanadium oxide to improve electrochemical performance in AZIBs. Herein, we successfully synthesized V2O3 with carbon shell (V2O3@C) by the reduction reaction of carbon with V2O5 in an oxygen-free environment and tested its electrochemical performance. By exploiting the effect of different calcination temperatures on the carbon reduction reaction, V2O3@C nanospheres with different carbon shell thicknesses were successfully synthesized. After fitting the experimental data, the calcination temperature for optimal electrochemical performance was determined to be 800 ℃ (VC-800). Detailly, the capacities of V2O3@C obtained at 700, 800 and 900 ℃ in the first 100 cycles at 0.5 A/g were 454.5, 400.7 and 325.1 mAh/g, respectively. Furthermore, the obtained VC-800 showed 126 % capacity retention after 10,000 cycles at 10 A/g. In the presence of carbon shell, V2O3 maintains the reversible redox valence characteristics while improving the conductivity and cycle life. This work may broaden ideas in improvement of vanadium-based materials for zinc ion storage.