In-situ formation of morphology-controlled cobalt vanadate on CoO urchin-like microspheres as asymmetric supercapacitor electrode

Abstract

The exploration of desirable structure is of positive significance for energy storage materials. In particular, morphology design of the electrode materials greatly affects the electrochemical performance. Herein, controllable synthesis of cobalt vanadate with various structures on 3D urchin-like CoO microspheres is achieved. By precisely controlling the vanadium content, we obtain cobalt vanadate with diverse structures, including 3D hollow nanocages, 3D nanocages connected to polygonal nanosheets, 2D honeycomb-like nanosheets, and 2D irregular nanosheets on CoO microspheres. Adjusting the content and structure of cobalt vanadate allows us to optimize its electrochemical performance. The optimized cobalt vanadate with a structure of hollow cages connected to polygonal nanosheets supported by CoO skeleton exhibits a superior energy storage capacity, and the final CoO@Co2V2O7 electrode delivers an outstanding areal specific capacitance of 7.58 F cm−2 at 2 mA cm−2. In addition, the fabricated asymmetric supercapacitor (ASC) possesses an excellent energy density of 0.45 mWh cm−2 at 1.60 mW cm−2, and an outstanding capacitance retention of 84.65% after 5000 cycles. In a word, the proposed strategy of structure-controllable cobalt vanadate supported by CoO is promising for supercapacitor electrode materials.