To overcome the drawback of low electrical conductivity within supercapacitor applications, several surfactants are used for nanoscale V2 O5 to enhance the specific surface area. Polyethylene glycol 6000 (PEG-6000), sodium dodecylbenzene sulfonate (SDBS), and Pluronic P-123 (P123) controllers, if used as soft templates, easily form large specific surface area crystals. However, the specific mechanism through which this occurs and the influence of these surfactants is not clear for V2 O5 ⋅H2 O. In the present study, we aimed to investigate the mechanism of crystal growth through hydrothermal processes and the pseudocapacitive behavior of these crystals formed by using diverse surfactants, including PEG-6000, SDBS, and P123. Our results show that different surfactants can dramatically influence the morphology and capacitive behavior of V2 O5 ⋅H2 O powders. Linear nanowires, flower-like flakes, and curly bundled nanowires can be obtained because of electrostatic interactions in the presence of PEG-6000, SDBS, and P123, respectively. Furthermore, the electrochemical performance of these powders shows that the nanowires, which are electrodes mediated by PEG-6000, exhibit the highest capacitance of 349 F g(-1) at a scan rate of 5 mV s(-1) of all the surfactants studied. However, a symmetric P123 electrode comprising curly bundled nanowires with numerous nanopores showed an excellent and stable specific capacitance of 127 F g(-1) after 200 cycles. This work is beneficial to understanding the fundamental role of the surfactant in the assisted growth of V2 O5 ⋅H2 O and the resulting electrochemical properties of the pseudocapacitors, which could be useful for the future design of appropriate materials.

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Supercapacitor is considered as a candidate for the promising energy storage device due to its permanent properties, high power density, and short charging time [1]. It can be used as a backup system, starting power of fuel cell , hybrid vehicle, or large industrial equipment [2].  There are two typical types of supercapacitors. One is electrochemical double layer capacitors (EDLC) utilizing a polarization phenomenon occurring between the surface of electrode and electrolyte. And the other is pseudo-capacitors using high-speed redox reactions. Normally, transition metal oxide and conductive polymer are used as the electrode materials of pseudo-capacitors [3]. Ruthenium [4] and nickel [5] are often studied among various metal electrode. They exhibit excellent performance, but it is difficult to commercially used because of its high price and eco-unfriendly with strong acid or alkali electrolyte. Therefore, manganese has been studied as an alternative materials.  Manganese is showing potential to be used as a supercapacitor electrode because of its low price and eco-friendly property. But, the mechanical strength of manganese is weak, so discharge cycle life is relatively short as compared with that of other electrode materials [6]. In addition, manganese oxide is limited used in conditions that require high power because the power density is reduced with increasing contact resistance [7].  In this study, we fabricate alloy of cobalt, nickel, and manganese prepared by chemical reduction method using the reducing agent (N2H4) and the dispersant (C6H5Na3O7) [8]. The unique shape of Mn-Co-Ni oxide powder was formed by combing powder of Mn (plate like), Co (flower like), and Ni (sphere) (Figure. 1). The electrochemical performance of the Mn-Co-Ni oxide was measured with cyclic voltammetry and charge-discharge test. Reference [1] J.R. Miller, P. Simon, Science, 321 (2008) 651-652. [2] S. Sarangapani, B.V. Tilak, C.P. Chen, J. Electrochem. Soc., 143 (1996) 3791-3799. [3] K. Zhang, L.L. Zhang, X.S. Zhao, J. Wu, Chem. Mat., 22 (2010) 1392-1401. [4] J.P. Zheng, P.J. Cygan, T.R. Jow, J. Electrochem. Soc., 142 (1995) 2699-2703. [5] V. Srinivasan, J.W. Weidner, J. Electrochem. Soc., 144 (1997) L210-L213. [6] S.C. Pang, M.A. Anderson, T.W. Chapman, J. Electrochem. Soc., 147 (2000) 444-450. [7] Q. Li, Z.-L. Wang, G.-R. Li, R. Guo, L.-X. Ding, Y.-X. Tong, Nano Lett., 12 (2012) 3803-3807. [8] K.H. Kim, Y.B. Lee, S.G. Lee, H.C. Park, S.S. Park, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 381 (2004) 337-342. Figure 1