Amar M. Patil

An innovative concept of use of redox-active electrolyte in asymmetric capacitor based on MWCNTs/MnO2 and Fe2O3 thin films

In present investigation, we have prepared a nanocomposites of highly porous MnO2 spongy balls and multi-walled carbon nanotubes (MWCNTs) in thin film form and tested in novel redox-active electrolyte (K3[Fe(CN)6] doped aqueous Na2SO4) for supercapacitor application. Briefly, MWCNTs were deposited on stainless steel substrate by “dip and dry” method followed by electrodeposition of MnO2 spongy balls. Further, the supercapacitive properties of these hybrid thin films were evaluated in hybrid electrolyte ((K3[Fe(CN)6 doped aqueous Na2SO4). Thus, this is the first proof-of-design where redox-active electrolyte is applied to MWCNTs/MnO2 hybrid thin films. Impressively, the MWCNTs/MnO2 hybrid film showed a significant improvement in electrochemical performance with maximum specific capacitance of 1012 Fg−1 at 2 mA cm−2 current density in redox-active electrolyte, which is 1.5-fold higher than that of conventional electrolyte (Na2SO4). Further, asymmetric capacitor based on MWCNTs/MnO2 hybrid film as positive and Fe2O3 thin film as negative electrode was fabricated and tested in redox-active electrolytes. Strikingly, MWCNTs/MnO2//Fe2O3 asymmetric cell showed an excellent supercapacitive performance with maximum specific capacitance of 226 Fg−1 and specific energy of 54.39 Wh kg−1 at specific power of 667 Wkg−1. Strikingly, actual practical demonstration shows lightning of 567 red LEDs suggesting “ready-to sell” product for industries.

Ultrathin nickel sulfide nano-flames as an electrode for high performance supercapacitor; comparison of symmetric FSS-SCs and electrochemical SCs device

Metal sulfides have received well deserved attention due to their excellent electrical conductivity and thermal stability, as compared to metal oxides, allowing them to achieve a high capacitance and energy density for portable energy storage devices. In this study, the preparation of highly porous nano-flames composed of nickel sulfide (NiS) thin film on a cost effective, flexible stainless steel substrate through a trouble free, inexpensive and simple chemical bath deposition (CBD) method is reported. The prepared nano-flames composed of a NiS thin film demonstrates the excellent electrochemical features with a maximum specific capacitance (Cs) of 750.6 F g−1 at a scan rate of 5 mV s−1 in a three electrode system. Furthermore, the portable symmetric flexible solid state supercapacitor (FSS-SC) and electrochemical supercapacitor (SC) are fabricated and tested. In comparison with the symmetric electrochemical SC, the symmetric FSS-SC shows an excellent electrochemical performance with a high Cs of 104 F g−1 at 5 mV s−1 with a good electrochemical stability of 85.3% over 3000 CV cycles. This study constitutes the first comparison of symmetric FSS-SCs and electrochemical SCs formed with NiS nano-flames. Such an impressive symmetric FSS-SC is predicted to be an exceptionally promising candidate for energy storage systems.

Fabrication of high performance flexible all-solid-state asymmetric supercapacitors with a three dimensional disc-like WO3/stainless steel electrode

Presently, significant attention has been paid towards the rational synthesis of nanostructured anode and cathode electrode materials for assembling high-performance supercapacitors. Despite significant progress being achieved in designing cathode electrode materials, anode electrode materials with high capacitance are hardly investigated. In the present article, a tungsten oxide (WO3) thin film is prepared on a flexible stainless steel substrate by a wet chemical method and used as an anode electrode to fabricate a flexible asymmetric supercapacitor (ASC). An electrochemical investigation of the WO3 thin film shows a maximum specific capacitance of 530 F g−1 at 1 mA cm−2 in a potential window of 0 to −0.8 V in 1 M Na2SO4 electrolyte. In addition, a highly energetic, flexible ASC device is assembled using a WO3 thin film as an anode, a MnO2 thin film as a cathode and polymer gel as an electrolyte. The as-assembled MnO2//WO3 ASC device exhibited a stable electrochemical potential window of 1.8 V and better cycling stability. Whats more, the flexible MnO2//WO3 ASC device achieves a high specific capacitance of 115 F g−1 with an acceptable specific energy of 52 W h kg−1 at a current density of 3 mA. Hence, the proposed flexible MnO2//WO3 ASC device creates one more option for anode materials to develop flexible energy storage devices.

Electrochemical behavior of chemically synthesized selenium thin film

The facile and low cost simple chemical bath deposition (CBD) method is employed to synthesize red colored selenium thin films. These selenium films are characterized for structural, morphological, topographical and wettability studies. The X-ray diffraction (XRD) pattern showed the crystalline nature of selenium thin film with hexagonal crystal structure. The scanning electron microscopy (SEM) study displays selenium nanoparticles ranging from 20 to 475 nm. A specific surface area of 30.5 m(2) g(-1) is observed for selenium nanoparticles. The selenium nanoparticles hold mesopores in the range of 1.39 nm, taking benefits of the good physicochemical stability and excellent porosity. Subsequently, the electrochemical properties of selenium thin films are deliberated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) techniques. The selenium thin film shows specific capacitance (Cs) of 21.98 F g(-1) with 91% electrochemical stability.

Design and synthesis of hierarchical mesoporous WO3-MnO2 composite nanostructures on carbon cloth for high-performance supercapacitors

Abstract To enhance the energy density and power performance of supercapacitors, the rational design and synthesis of active electrode materials with hierarchical mesoporous structure is highly desired. In the present work, fabrication of high-performance hierarchical mesoporous WO3-MnO2 composite nanostructures on carbon cloth substrate via a facile hydrothermal method is reported. By varying the content of MnO2 in the composite, different WO3-MnO2 composite thin films are obtained. The formation of composite is confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The Brunauer-Emmett-Teller (BET) analysis reveals maximum specific surface area of 153 m2 g−1. The optimized WO3-MnO2 composite electrode demonstrates remarkable electrochemical performance with high specific capacitance of 657 F g−1 at a scan rate of 5 mV s−1 and superior longterm cycling stability (92% capacity retention over 2000 CV cycles). Furthermore, symmetric flexible solid-state supercapacitor based on WO3-MnO2 electrodes has been fabricated. The device exhibits good electrochemical performance with maximum specific capacitance of 78 F g−1 at a scan rate of 5 mV s−1 and specific energy of 10.8 Wh kg−1 at a specific power of 0.65 kW kg−1. The improved electrochemical performance could be ascribed to the unique combination of multivalence WO3 and MnO2 nanostructures and synergistic effect between them