Enabling 2.4-V aqueous supercapacitors through the rational design of an integrated electrode of hollow vanadium trioxide/carbon nanospheres

Aqueous supercapacitors (SCs) exhibit several advantages, including high-power density, cycling durability, and safety; however, the shortage of low energy density inhibits their further application. Acquiring an excellent performance upon using simple strategies would be beneficial, but remains challenging. Here, an integrated electrode of hollow V2O3/carbon nanospheres (H-V2O3/C) was designed and synthesized for SCs. The introduction of carbon can increase the conductivity and stability, whereas the hollow structure endows H-V2O3/C with a high specific surface area and rapid transport of ions. Moreover, the H-V2O3/C integrated electrode can simultaneously work in both negative and positive potential windows. Benefiting from these advantages, the H-V2O3/C integrated electrode exhibits a specific capacitance as high as 708.6 F g−1 in a wide voltage window of −1.1–1.3 V. Furthermore, stemming from the multiple energy storage mechanisms, the aqueous integrated full SC device exhibits a wider potential window and higher energy density than the traditional (a)symmetric ones. Therefore, the proposed device delivers a wide voltage window of 2.4 V with an energy density of 96.8 W h kg−1 at a power density of 1204.6 W kg−1, as well as superior cycling stability. This study enlightens the design and preparation of electrode materials, opening up a possible approach for developing wide voltage aqueous SCs.