High-Performance Supercapacitors Based on Hierarchical VOx Microspheres Forming from Hyperbranched Nanoribbons

Novel VOx nanomaterials as high performance electrode materials of supercapacitors were successfully synthesized by solvothermal method using V₂O₅, H₂O₂, (NH₄)₂SO₄ and EG (Ethylene Glycol). These as-prepared nanomaterials are hierarchical microspheres with diameter of ~5 μm, which formed from hyperbranched growth of nanoribbons. According to XRD and TEM, these hierarchical VOx microspheres consist of V₆O₁₃ with metallic conductivity and VO₂. These materials exhibited a tremendous specific capacitance of 581 F/g, with corresponding volumetric specific capacitance of 3.94 F/cm³, at 0.6 A/g in the potential range of 0 to 1.2 V when used as supercapacitor electrodes in a solution of 1 M LiNO₃. The energy density is as high as 29 Wh/kg, which is much higher than those of many other symmetrical supercapacitors. In addition, the capacity retention of 65% was achieved even after 2000 cycles, demonstrating high performance of vanadium oxide nanomaterials used in supercapacitors.