In Situ Growth of Free-Standing All Metal Oxide Asymmetric Supercapacitor

Metal oxides have attracted renewed interest in applications as energy storage and conversion devices. Here, a new design is reported to acquire an asymmetric supercapacitor assembled by all free-standing metal oxides. The positive electrode is made of 3D NiO open porous nanoribbons network on nickel foam and the negative electrode is composed of SnO₂/MnO₂ nanoflakes grown on carbon cloth (CC) substrate. The combination of two metal oxide electrodes which replaced the traditional group of carbon materials together with metal oxide has achieved a higher energy density. The self-supported 3D NiO nanoribbons network demonstrates a high specific capacitance and better cycle performance without obvious mechanical deformation despite of undergoing harsh bulk redox reactions. The SnO₂/MnO₂ nanoflakes as the pseudocapacitive electrode exhibit a wide range of voltage window (-1 to 1 V), which is conducive to electrochemical energy storage. The (CC/SnO₂/MnO₂)(-)//(NiO/Ni foam)(+) asymmetric supercapacitor device delivers an energy density of 64.4 Wh kg^-1 (at a power density of 250 W kg^-1) and two devices in series are applied to light up 24 red LEDs for about 60 s. The outstanding electrochemical properties of the device hold great promise for long-life, high-energy, and high-power energy storage/conversion applications.