Ni3Se4 Nanostructure as a Battery-type Positive Electrode for Hybrid Capacitors

Battery-type supercapacitors have drawn significant attention due to their high charge storage ability resulted from the combined surface and intercalation redox phenomenon. In this regard, nickel chalcogenides are expected to deliver high specific capacity accompanied by their dominant battery-type supercapacitor features. Herein, we have developed a facile one step solvothermal route to prepare pure phase Ni3Se4 nanostructures and attempted to understand the synthetic factors such as solvent and Ni/Se ratio on the formation of Ni3Se4 phase. The obtained Ni3Se4 nanostructures were subjected to the supercapacitor performance evaluation by loading them onto carbon paper and found that the electrode materials are able to store the charge through dominant intercalation redox process (battery-type storage mechanism). Among them, Ni3Se4 (NS-15E(1)) synthesized in water/ethanol (2 : 3) mixture with Ni/Se (1 : 1) ratio has displayed a high specific capacity of 376 C g(-1) (104 mA hg(-1)) at a current density of 1 A g(-1) in 2 m KOH. The superior charge storage of NS-15E(1) could be attributed to the improved redox process facilitated by the easier diffusion of electrolyte ions into the bulk of the material. Furthermore, a hybrid device fabricated by using Activated charcoal (AC) and NS-15E(1) as negative and positive electrodes, respectively has showed an extended voltage window of 1.6 V and achieved a high energy density similar to 20 Wh Kg(-1) at a power density of 329 W kg(-1).