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Recently, transition metal-based nanomaterials have played a key role in the applications of supercapacitors. In this study, nickel phosphide (Ni-P) was simply combined with NiCo LDH via facile phosphorization of Ni foam and subsequent electrodeposition to form core–shell nanorod arrays on the Ni foam; the Ni-P@NiCo LDH was then directly used for a pseudocapacitive electrode. Owing to the splendid synergistic effect between Ni-P and NiCo LDH nanosheets as well as the hierarchical structure of 1D nanorods, 2D nanosheets, and 3D Ni foam, the hybrid electrode exhibited significantly enhanced electrochemical performances. The Ni-P@NiCo LDH electrode showed a high specific capacitance of 12.9 F cm−2 at 5 mA cm−2 (3470.5 F g−1 at a current density of 1.3 A g−1) that remained as high as 6.4 F cm−2 at a high current density of 100 mA cm−2 (1700 F g−1 at 27 A g−1) and excellent cycling stability (96% capacity retention after 10 000 cycles at 40 mA cm−2). Furthermore, the asymmetric supercapacitors (ASCs) were assembled using Ni-P@NiCo LDH as a positive electrode and activated carbon (AC) as a negative electrode. The obtained ASCs delivered remarkable energy density and power density as well as good cycling performance. The enhanced electrochemical activities open a new avenue for the development of supercapacitors. [ABSTRACT FROM AUTHOR]

In this work, three dimensional (3D) Ni x Co 1− x S 2 /graphene composite hydrogels with different Ni contents (denoted as Ni x Co 1− x S 2 /GH ( x = 0, 0.31, 0.56, 0.66, 1)) have been synthesized by a simple one-step hydrothermal method and utilized as the active materials of supercapacitors. The as-prepared samples present a 3D interconnected porous network with the pore sizes in the range of several to tens micrometers. Interestingly, the Ni x Co 1− x S 2 particles are uniformly located on the graphene network and the particle size is evolved from ∼50 nm to ∼1.5 μm with the increase of Ni content. The electrochemical measurements revealed that the specific capacitance, rate capability and cyclability of different Ni x Co 1− x S 2 /GH electrodes are strongly affected by their different Ni content. Among these, the 3D Ni 0.31 Co 0.69 S 2 /GH composite has the highest specific capacitance of 1166 F/g at a current density of 1 A/g. Furthermore, a specific capacitance of 559 F/g can be still maintained at high current density of 20 A/g. After 1000 charge–discharge cycles at 5 A/g, the specific capacitance remains a high value of 755 F/g. [ABSTRACT FROM AUTHOR]

An asymmetric supercapacitor based on manganese dioxide/Au/nickel foam (MANF) electrode as positive electrode and graphene or commercial activated carbons (AC) as negative electrode was fabricated. The effect of different negative electrode materials and mass ratios of negative/positive electrodes on the electrochemical properties of the asymmetric supercapacitor was carefully investigated. The results suggest that the mass ratio of negative/positive electrode has a significant impact on the specific capacitance of the asymmetric supercapacitor. Especially, it is found that the optimal mass ratio of the negative/positive electrode is slightly lower than that calculated according to charge balance. On the other hand, the asymmetric supercapacitor with commercialized AC as negative electrode possesses higher specific capacitance and better rate capability than that of the asymmetric supercapacitor with graphene as negative electrode. The negative material has slight impact on the cycle stability of the asymmetric supercapacitor. In addition, the optimized asymmetric supercapacitor with MANF composite as positive electrode and AC as negative electrode can obtain an energy density as high as 65.9 Wh kg at a power density of 180 W kg and a cell voltage of 1.8 V in the neutral NaSO aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: A class of novel composite electrodes based on poly(3,4-ethylenedioxythiophene) (PEDOT) and manganese dioxide (MnO2) was assembled by step-by-step anodic deposition on nickel foam for supercapacitor application. The effect of the distribution and loading of PEDOT on the electrochemical performance of composite electrodes was studied carefully. Among these composite electrodes, the optimized PEDOT/MnO2/PEDOT sandwich electrode shows excellent capacitive behavior, and MnO2 species in the optimized sandwich electrode possesses a high specific capacitance of 487.5Fg−1 at 1Ag−1. Furthermore, an asymmetric supercapacitor cell with the optimized sandwich composite as positive electrode and active carbon (AC) as negative electrode also exhibits outstanding performance at a cell voltage of 1.8V in a 0.5M Na2SO4 aqueous electrolyte. It has a high energy density of 30.2Whkg−1 with a power density of 180Wkg−1. And even at a high power density of 2.7kWkg−1, the asymmetric supercapacitor can deliver a high energy density of 13.1Whkg−1. Moreover, the asymmetric supercapacitor displays impressive electrochemical cycling stability with 99.5% initial capacitance remained after 1000 continuous cycles. [Copyright &y& Elsevier]

We successfully developed a 3D porous CNT/MnO 2 composite electrode based on manganese oxide and carbon nanotubes (CNTs) by a simple “dipping and drying” process followed by a potentionstatic deposition technology for non-enzymatic glucose detection and supercapacitor applications. The composition and structure of the as-prepared electrode were characterized by energy-dispersive X-ray spectroscopy (EDX), field Emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. The electrochemical performances were evaluated by cyclic voltammetry (CV), chronopotentiometry (CP) and Amperometric i – t techniques. The as-prepared sensor could accurately detect glucose in 0.5 M NaOH solution in the presence of interferences, such as ascorbic acid, uric acid and fructose, with a high sensitivity up to 3406.4 μA/(cm 2 mM). These excellent electrochemical performances were closely related to the synergistic effect of two components and the unique 3D porous architecture of the electrode. A symmetrical supercapacitor has been also fabricated using the novel electrodes and it exhibited a high specific capacitance of 160.5 F/g at the current density of 1 A/g which can rival with the asymmetrical supercapacitor. Such symmetrical device delivered prominent energy density of 22.3 Wh kg −1 at the power density of 500 W kg −1 . All of these perfect performances paved the way for this hybrid to be a potential competitive candidate in the application of glucose sensor and supercapacitor. [ABSTRACT FROM AUTHOR]

Abstract: This work reports the synthesis of novel nanocomposite electrodes based on MnO2 nanosheets, Pt, Au, or Pd nanoparticles (NPs), exfoliated carbon nanotubes (CNTs), and Ni foam (NF) substrates. The MnO2–Pd–CNT–NF electrode in 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIM-PF6)/N, N-dimethylformamide (DMF) electrolyte exhibits a high specific capacitance of 559.1F/g based on MnO2 with a wide potential window (2.1V). To the best of our knowledge, this is one of the highest capacitance for MnO2 in ionic liquid (IL) electrolytes ever reported. The IL hybrid supercapacitors are assembled using MnO2–Pd–CNTs–NF positive electrode, activated carbon (AC) negative electrode, and BMIM-PF6/DMF electrolyte displaying high operating voltage (3V), high energy density (78.4Wh/kg) and high power density (12.7kW/kg). The superior performances of the MnO2 IL hybrid supercapacitors suggest their potential application for the future generation of electrochemical power sources. [Copyright &y& Elsevier]