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Lithium versus Mono/Polyvalent Ion Intercalation: Hybrid Metal Ion Systems for Energy Storage (Review)
  • Year: 2019
Lithium versus Mono/Polyvalent Ion Intercalation: Hybrid Metal Ion Systems for Energy Storage (Review)
  • Author(s): R. Stoyanova, V. Koleva, A. Stoyanova

The energy storage by redox intercalation reactions is, nowadays, the most effective rechargeable ion battery. When lithium is used as intercalating agents, the high energy density is achieved at an expense of non-sustainability. The replacement of Li + with cheaper monovalent ions enables to make greener battery alternatives. The utilization of polyvalent ions instead of Li + permits to multiplying the battery capacity. Contrary to Li + , the realization of quick and reversible intercalation of bigger monovalent and of polyvalent ions is a scientific challenge due to kinetic constraints, polarizing ion effects and Coulomb interactions. Herein we provide a vision how to make the intercalation of these ions feasible. The idea is to perform dual intercalation of ions having different charges, radii, preferred coordination and diffusion pathway topology. All these features are demonstrated by the recent knowledge on selective and non-selective intercalation properties of oxides and polyanion compounds with layered and tunnel structures. Based on dual intercalation properties, the fabrication of hybrid metal ion batteries is presented and discussed.

  • Source: Chemical Record 19 (2019) 474-501.
A study on graphene/tin oxide performance as negative electrode compound for lithium battery application
  • Year: 2019
A study on graphene/tin oxide performance as negative electrode compound for lithium battery application
  • Author(s): A. Y. Shenouda, A.A. Momchilov

A novel negative (anode) material for lithium-ion batteries, tin oxide particles covered with graphene (SnO/graphene) prepared from graphite was fabricated by hydrothermal synthesis. The structure and morphology of the composite were characterized by Raman spectra, FTIR spectra, XRD, XPS and FESEM. It is observed that the G and 2D bands (1581 and 2831 cm−1, respectively) have more intensity in graphene rather than graphite. EIS was carried out. It is observed that the lowest Warburg impedance coefficient, σw, is 24.39 Ω s0.5 for Li/SnO–graphene (3:1) cell. The reversible specific capacity of Li/SnO–graphene (3:1) cell was about 0.950 Ah g−1 after 100 cycles at current density current 10−2 A g−1. These results indicate that 3 SnO:1 graphene possesses superior cycle performance and high rate capability. The enhanced electrochemical performances can be ascribed to the characteristic structure of tin oxide with graphene shells, which buffer the volume change of the metallic tin and prevent the detachment and agglomeration of pulverized tin.

  • Source: Journal of Materials Science: Materials in Electronics 30, 2019, 79–90
Ni(OH)2 and MnO2 based nanocomposites for hybrid supercapacitors
  • Year: 2018
Ni(OH)2 and MnO2 based nanocomposites for hybrid supercapacitors
  • Author(s): L. Soserov, A. Stoyanova, T. Boyadzhieva, V. Koleva, M. Kalapsazova, R. Stoyanova

Hybrid supercapacitors with the composite electrode materials display high energy density at the expense of the reduced cycle stability. Herein, we provide new data on the electrochemical performance of hybrid electrodes based on mixed nickel hydroxides/manganese oxides in the form of structured and multiphase composites. As structured composites, two types of less known structure modifications are examined: interstratified modification of Ni(OH)2 (i.e. α/βIS-Ni(OH)2) and ε-modification of MnO2. The multiphase hydroxide/oxide composites are prepared by the conventional grinding of α/βIS-Ni(OH)2 and ε-MnO2 and by the in-situ formation after the reaction of layered Na0.5Ni0.5Mn0.5O2 with mixed LiOH-KOH electrolyte. The structure, morphology and porous texture properties of composites are analyzed by means of powder X-ray diffraction, scanning electron microscopy (SEM) and low-temperature nitrogen adsorption, respectively. The electrochemical performance of composites electrodes is determined by galvanostatic experiments in concentrated individual KOH and mixed LiOH-KOH electrolytes. The ex-situ X-ray diffraction is used to monitor the changes in composite electrodes during electrochemical cell function. It has been found that α/βIS-Ni(OH)2 participates in electrochemical reaction concomitantly with H2O and Li+ intercalation, while the electrochemical performance of ε-MnO2 is determined by surface adsorption of electrolyte alkaline ions. The best electrochemical performance (in terms of discharge capacity, rate capability and cycling stability) is achieved for α/βIS-Ni(OH)2 especially when it works in mixed LiOH-KOH electrolyte. In alkaline electrolyte solution, layered Na0.5Ni0.5Mn0.5O2 is transformed into a phase mixture between slightly sodium deficient oxide Na0.5-xNi0.5Mn0.5O2 and α-type nickel hydroxide. Thus generated multiphase composite demonstrates the highest areal capacitance and a rate capability comparable with that for α/βIS-Ni(OH)2.

  • Source: Electrochimica Acta 283 (2018) 1063-1071
Investigation of Montmorillonite as carrier for OER
  • Year: 2018
Investigation of Montmorillonite as carrier for OER
  • Author(s): Boshnakova, I., Lefterova, E., Slavcheva, E.

The aim of this work is to investigate the natural mineral Montmorillonite (MMT) as catalytic support and to assess the efficiency of the composite MMT-supported Ir toward OER in acidic electrochemical water splitting. MMT is a phyllosilicate layered clay with 2:1 type sheet structure with high cation exchange capacity, high surface area and low cost. Three different catalyst with iridium loadings of 10, 20, and 30 wt% Ir supported on MMT are synthesized. Their phase identification, crystallite size, elemental analysis, and thermal stability are studied by means of XRD, HRTEM, EDX, and TGA, respectively. The catalytic performance is examined in 0.5 M H2SO4 and in electrolysis cell with proton conductive polymer membrane (PEMEC). The results obtained prove that montmorillonite is a promising alternative of the conventional carbon supports with the advantage of being both easily available and cost favourable. Ir/MMT loaded with 30 wt% Ir is the best performed catalyst. In PEMEC operated at 80 °C the catalyst loading of 0.5 mgIr cm−2 ensures intensive and sustainable oxygen evolution with current density reaching 200 mA cm−2 already at 1.6 V.

  • Source: International Journal of Hydrogen Energy, 43, 35, 2018, 16897-16904
Gold-supported magnetron sputtered Ir thin films as OER catalysts for cost-efficient water electrolysis
  • Year: 2018
Gold-supported magnetron sputtered Ir thin films as OER catalysts for cost-efficient water electrolysis
  • Author(s): Petkucheva, E., Borisov, G., Lefterova, E., Heiss, J., Schnakenberg, U., Slavcheva, E.

This work presents a research on the preparation of thin composite catalytic films in which an essential part of the efficient but expensive Ir is substituted by Au sub-layer using the preparation method of direct current magnetron sputtering (DCMS). The aim is to investigate the influence of the Au sub-layer on the catalytic activity toward oxygen evolution reaction (OER) of water electrolysis. The properties of the sputtered films are studied using X-ray diffraction (XRD) and electrochemical methods of cyclic voltammetry, quasi steady state polarization and chronoamperometry. It is found that by proper variations in the films thickness it is possible to realize synergetic effects leading to essential decrease in Ir loading and the cost of catalysis without sacrifice in efficiency.

  • Source: International Journal of Hydrogen Energy, 43, 35, 2018, 16905-16912