Large gap cobalt‑vanadium oxide structure encapsulated in porous carbon for high performance capacitive deionization

The application of traditional electrode materials for high-performance capacitive deionization (CDI) has been persistently limited by their low charge-storage capacities and slow salt removal rates. In order to improve the electrochemical performance, cobalt‑vanadium coated porous carbon gradient hollow spheres (Co3V2O8@C) with large internal spacing, and high pore structure was prepared in this paper to improve the ion mobility. The structure with the following characteristics: (1) Co3V2O8@C with a reversible ionic insertion/de-insertion and good electrical conductivity; (2) the increased lattice spacing effectively mitigates volume expansion during prolonged cycling; (3) it increases the utilization rate of the active center inside the electrode material and shows high electrochemical adsorption capacity by being applied to capacitive deionization. When applied to CDI, Co3V2O8@C has top CDI performance compared to the currently reported cobalt-based electrode materials. The holding capacities for different ions (Cl−, SO42−, NO3−, and Na+) were 160, 161, 244, and 69 mg·g−1 with good cycling stability after 100 h. Our research provides a reasonable pathway for building the structure of high-capacity cobalt-based electrodes and further promoting the development of high-performance CDI electrode materials.