Polymer electrolyte based solid state redox supercapacitors with poly (3-methyl thiophene) and polypyrrole conducting polymer electrodes

Types I and II solid state redox supercapacitors have been constructed using polypyrrole (pPy) and poly (3-methyl thiophene) (pMeT) conducting polymer electrodes with lithium ion conducting polymer electrolyte poly(ethylene oxide) (PEO)-LiCF₃SO₃ plasticised with poly (ethylene glycol) (PEG). The performance of the capacitors has been characterised by a.c. impedance, linear sweep voltammetry, galvanostatic charge-discharge methods and long term cycling tests. The asymmetric type II capacitors with p-doped pPy and pMeT electrodes give a capacitance value ∼ 2 mF cm⁻² (equivalent to 18 Fg⁻¹ of the total mass of the electrodes) and can be charged up to the voltage of 1.7 V. The symmetric type 1 capacitors of the configuration pPy | polymer electrolyte | pPy and pMeT | polymer electrolyte | pMeT show comparable values of capacitance but they are limited to the working voltage of <1.0 V. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Electrochemical redox supercapacitors using PVdF-HFP based gel electrolytes and polypyrrole as conducting polymer electrode

Electrochemical redox supercapacitors have been fabricated using polymeric gel electrolytes polyvinylidene fluoride co-hexafluoropropylene (PVdF-HFP)–ethylene carbonate (EC)–propylene carbonate (PC)–MClO₄: M = Li, Na, (C₂H₅)₄N and electrochemically deposited polypyrrole as conducting polymer electrode. The performance of the capacitors have been characterized using a.c impedance spectroscopy, cyclic linear sweep voltammetry and galvanostatic charge–discharge techniques. The capacitors shows larger values of overall capacitance of about 14–25 mF cm^− 2 (equivalent to a single electrode specific capacitance of 78–137 F g^− 1 of polypyrrole), which corresponds to the energy density of 11–19 W h kg^− 1 and power density of 0.22–0.44 kW kg^− 1. The values of capacitance have been found to be almost stable up to 5000 cycles and even more. A comparison indicates that the capacitive behaviour and the capacitance values are not much affected with the size of cations of the salts incorporated in gel electrolytes, rather predominant role of anions is possible at the electrode–electrolyte interfaces. Furthermore the coulombic efficiencies of all the cells were found to be nearly 100% that is comparable to the liquid electrolytes based capacitors.     

MnO2/graphite electrodeposited under supergravity field for supercapacitors and its electrochemical properties

MnO₂/graphite electrode material is successfully synthesized by electrodeposition under supergravity field from manganese acetate and graphite suspending solution. X-ray diffraction and field emission scanning electron microscopy show that the obtained composite is γ-MnO₂/graphite. The process of depositing the MnO₂/graphite was shown by the schematic illustration. Galvanostatic charge/discharge and cyclic voltammograms tests are applied to investigate electrochemical performances of the composite electrodes prepared under supergravity fields. MnO₂/graphite synthesized under supergravity field exhibits good discharge capacitance and the specific capacitance is 367.77 F g^?1 at current density of 0.5 A g^?1. It is found that supergravity field has effects on the electrochemical performances of MnO₂/graphite material.     

Role of composite MnO2 cathode on electrochemical cells based on polymer electrolyte (PEO/NaClO3)

Thin-film sodium-ion-conducting polymer electrolyte based on polyethylene oxide (PEO) system was prepared by solvent casting method. The thin-film electrolytes were characterized by X-ray diffraction (XRD), infrared (IR), cyclic voltammetry (CV) and alternating current conductivity, and Wagner’s polarization method. The complexation of salt with PEO was confirmed by XRD and IR studies. The charge transport of these electrolytes is mainly due to ions, which was confirmed by the transference number experiment. The conductivity studies show that the conductivity value of PEO/NaClO₃ complex increases with the increase of temperature as well as the addition of low molecular weight polyethylene glycol, dimethyl formamide, and propylene carbonate. The electrolyte stability and cell reversibility were analyzed by CV studies. Electrochemical cells have been fabricated with a common cell configuration Na|electrolyte|(MnO₂ + I₂ + C + electrolyte), and their discharge characteristic studies were made through a load 100 kΩ at room temperature. The measured open circuit voltage ranges from 2.80 to 2.54 V with short circuit current ranges from 667 to 1,000 μA and several other cell parameters were evaluated. Finally, the merit of the composite cathode is found with the comparison of the MnO₂ cathode.     

Sonochemically synthesized MnO2 nanoparticles as electrode material for supercapacitors

In this study, manganese oxide (MnO₂) nanoparticles were synthesized by sonochemical reduction of KMnO₄ using polyethylene glycol (PEG) as a reducing agent as well as structure directing agent under room temperature in short duration of time and characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM), Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis. A supercapacitor device constructed using the ultrasonically-synthesized MnO₂ nanoparticles showed maximum specific capacitance (SC) of 282 Fg⁻¹ in the presence of 1 M Ca(NO₃)₂ as an electrolyte at a current density of 0.5 mA cm⁻² in the potential range from 0.0 to 1.0 V and about 78% of specific capacitance was retained even after 1000 cycles indicating its high electrochemical stability.     

Galvanostatically deposited Fe: MnO2 electrodes for supercapacitor application

The present investigation describes the addition of iron (Fe) in order to improve the supercapacitive properties of MnO₂ electrodes using galvanostatic mode. These amorphous worm like Fe: MnO₂ electrodes are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR) and wettability test. The supercapacitive properties of MnO₂ and Fe: MnO₂ electrodes are investigated using cyclic voltammetry, chronopotentiometry and impedance techniques. It is seen that the supercapacitance increases with increase in Fe doping concentration and achieved a maximum of 173 F g^?1 at 2 at% Fe doping. The maximum supercapacitance obtained is 218 F g^?1 for 2 at% Fe: MnO₂ electrode. This hydrous binary oxide exhibited ideal capacitive behavior with high reversibility and high pulse charge–discharge property between ?0.1 and +0.9 V/SCE in 1 M Na₂SO₄ electrolyte indicating a promising electrode material for electrochemical supercapacitors.     

Honeycomb-like manganese oxide nanospheres for redox supercapacitors

Honeycomb-like MnO₂ nanospheres were synthesized using stainless steel substrates by a facile chemical bath deposition method. The obtained nanospheres were about 200–400 nm in diameter and consisted of porous ultrathin nanosheets. Honeycomb-like MnO₂ nanospheres exhibited a high specific capacitance of 240 F g^?1 and 87.1% capacitance retention after 1000 cycles at a current density of 0.5 A g^?1. These remarkable electrochemical results imply great potential for applications of the honeycomb-like MnO₂ nanospheres in supercapacitors.     

锂离子电池用具有分级三维离子电子混合导电网络结构的纳微复合电极材料

文章评述了分级三维离子电子混合导电网络结构和具有该结构的纳微复合电极材料在锂离子电池中的应用等方面的最新研究工作进展.首先介绍了纳微复合电极结构相关概念及其优缺点,然后列举了一些运用此概念设计并构筑出的电极材料实例.研究证明,此新型电极结构能够大幅提高锂离子电池电极材料的储锂性能,并且该结构设计还可推广到其他电化学储能...     

Studies on PEO-based sodium ion conducting composite polymer films

A sodium ion conducting composite polymer electrolyte (CPE) prepared by solution-caste technique by dispersion of an electrochemically inert ceramic filler (SnO₂) in the PEO–salt complex matrix is reported. The effect of filler concentration on morphological, electrical, electrochemical, and mechanical stability of the CPE films has been investigated and analyzed. Composite nature of the films has been confirmed from X-ray diffraction and scanning electron microscopy patterns. Room temperature d.c. conductivity observed as a function of filler concentration indicates an enhancement (maximum) at 1–2 wt% filler concentration followed by another maximum at ∼10 wt% SnO₂. This two-maxima feature of electrical conductivity as a function of filler concentration remains unaltered in the CPE films even at 100 °C (i.e., after crystalline melting), suggesting an active role of the filler particles in governing electrical transport. Substantial enhancement in the voltage stability and mechanical properties of the CPE films has been noticed on filler dispersion. The composite polymer films have been observed to be predominantly ionic in nature with t _ion ∼ 0.99 for 1–2 wt% SnO₂. However, this value gets lowered on increasing addition of SnO₂ with t _ion ∼ 0.90 for 25 wt% SnO₂. A calculation of ionic and electronic conductivity for 25 wt% of SnO₂ film works out to be ∼2.34 × 10⁻⁶ and 2.6 × 10⁻⁷ S/cm, respectively.     

Nickel, cobalt, and manganese oxide composite as an electrode material for electrochemical supercapacitors

A composite material, Ni_1/3Co_1/3Mn_1/3(OH)₂, is synthesized by chemical precipitation method for supercapacitors' electrode material. Physical characterizations using x-ray diffraction, energy-dispersive x-ray, and scanning electron microscopy show that Ni_1/3Co_1/3Mn_1/3(OH)₂ possesses an amorphous structure and higher specific surface area (268.5 m²?g^?1), which lead to a high initial specific capacitance of 1,403 F?g^?1 in the potential window of 0–1.5 V. It may be a potential electrode material for future supercapacitor when its cycling stability and rate performance are addressed.     

Mechanochemical-synthesized Al-doped manganese dioxides for electrochemical supercapacitors

Al-doped MnO₂ as electrode materials for supercapacitor were synthesized by high-energy ball milling. The morphologies and structures of prepared MnO₂ were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Electrochemical investigation indicated that doped MnO₂ presented preferable electrochemical performances than un-doped MnO₂, but there were obvious capacitance decline in the first several dozen of cycles for all doped MnO₂ samples. The Al_0.05/Mn_0.95O₂ electrode, especially, showed the largest capacitance among all prepared MnO₂ samples. Excellent conductivity of Al in doped MnO₂ was considered to be responsible for enhanced electrochemical performances of doped MnO₂.     

Synthesis and performance of nickel hydroxide nanodiscs for redox supercapacitors

Herein, we report the facile synthesis of β-Ni(OH)₂ nanodiscs by chemical precipitation method and their use in supercapacitors. β-Ni(OH)₂ nanodiscs are characterized by FTIR, XRD, FESEM, XPS and TGA analysis. Morphological analysis revealed the uniform nanodisc morphology of β-Ni(OH)₂. The supercapacitor behavior is evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy measurements in 1-M aqueous KOH solution with 0- to 0.6-V potential window. The specific capacitance of β-Ni(OH)₂ nanodiscs is found to be 400 F g⁻¹. The energy and power densities of the β-Ni(OH)₂ nanodiscs are found to be 7.15 W h kg⁻¹ and 1716 W kg⁻¹, respectively, at the current density of 1 A g⁻¹. The cycle life test shows the good stability of the electrode with 83 % retention capacitance even after 1500 cycles.

     

Electrochemical characterization on layered lithium ruthenate for electrochemical supercapacitors

Electrochemical characteristics of lithium ruthenate (Li_xRuO_2+0.5x·nH₂O) for electrochemical capacitors' electrode material were first examined in this paper by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge tests. Results show that Li_xRuO_2+0.5x·nH₂O has electrochemical capacitive characteristic within the potential range of − 0.2–0.9 V (vs. SCE) in 1 M Li₂SO₄ solution. The capacitance mainly arises from pseudo-capacitance caused by lithium ions' insertion/extraction into/out of the Li_xRuO_2+0.5x·nH₂O electrode. The specific capacitance of 391 F g^− 1 can be delivered at 1 mA charge–discharge current for Li_xRuO_2+0.5x·nH₂O electrode with an energy density of 65.7 W h kg^− 1. This material also exhibits an excellent cycling performance and there is no attenuation of capacitance over 600 cycles.     

Evaluation of lyophility of carbon materials for electrodes of supercapacitors

Physics of the Solid State - The heats of wetting have been measured experimentally for some of the solvents used for the preparation of electrolytes of supercapacitors. For the first time, the...     

Nanostructured transition metal oxides for aqueous hybrid electrochemical supercapacitors

In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the capacitance of the metal oxides and the cell voltage of the supercapacitor. It is shown that the cell voltage of an electrochemical supercapacitor can be increased significantly with the use of hybrid systems. The most relevant associations are Fe₃O₄ or activated carbon as the negative electrode and MnO₂ as the positive. The cell voltage of the Fe₃O₄/MnO₂ device is 1.8 V and this value was increased to 2.2 V by using activated carbon instead of Fe₃O₄. These two systems have shown superior behavior compared to a symmetric MnO₂/MnO₂ device which only works within a 1 V potential window in aqueous K₂SO₄. Furthermore, the activated carbon/MnO₂ hybrid device exhibits a real power density of 605 W/kg (maximum power density =19.0 kW/kg) with an energy density of 17.3 Wh/kg. These values compete well with those of standard electrochemical double layer capacitors working in organic electrolytes. PACS 82.47.Uv; 82.45.Fk; 82.45.Yz     

Effect of electrodeposition modes on ruthenium oxide electrodes for supercapacitors

With developments in energy storage devices, supercapacitors are gaining more attraction because of their potential to excel batteries shortly. In this work, ruthenium oxide (RuO₂) has been deposited on stainless steel and studied the influence of surface modification of solid electrodes on capacitance properties. Hydrous ruthenium oxide was plated by different modes such as potential sweep method (cyclic voltammetric), constant potential method (chronoamperometry) and optimised potential pulse method using a recently reported precursor material namely ruthenium nitrosylsulfate (RuNS). The structural information and morphology of electrodeposits were characterised by X-ray diffractometer and scanning electron microscope respectively. The XRD studies indicate a poor crystalline state for RuO₂ in all the modes of deposition but can contribute to a higher surface area when compared to a highly crystalline form. The SEM analysis revealed the formation of surface modification concerning the change of potential mode. Mud-cracked morphology, spherical particles and dendrimeric morphology observed on chronoamperometry, potential pulse and cyclic voltammetry respectively. Electrochemical studies were also conducted on the samples to assess their performance for supercapacitor applications. The spherical particles of hydrous RuO₂ show high performance of capacitance behaviour 1180 F/g in 0.5 M H₂SO₄ at the scan rate of 5 mV/s. Dendrimeric morphology and mud-cracked morphology shows 573 F/g and 546 F/g respectively in same 0.5 M H₂SO₄ at the scan rate of 5 mV/s. The studies reveal that RuO₂ electrodes can be exploited for their outstanding capacitive behaviour by properly controlling the morphology of the deposits.     

Nano-composite LiMnPO4 as new insertion electrode for electrochemical supercapacitors

Nano-composite olivine LiMnPO₄ (nC-LMP) was found to exhibit facile pseudo-capacitive characteristics in aqueous as well as non-aqueous electrolytes. We demonstrated employing nC-LMP as positive electrode in hybrid electrochemical capacitors namely Li-Ion hybrid capacitors (LIC). Adapting a simple CVD technique, nano-crystallites of LiMnPO₄ were coated with carbon monolayers of ∼2 nm thick to circumvent its poor intrinsic electronic conductivity. The novelty is that the single crystallites were intimately covered with carbon ring and networked to the neighboring crystallites via the continuous carbon wire-like connectivity as revealed from HRTEM analysis. Single electrode faradic capacitance of 3025 Fg⁻¹ (versus standard calomel reference electrode) was deduced for carbon coated LMP, the highest reported hitherto in Li⁺ aqueous electrolytes. Employing nC-LMP as working electrode versus an activated carbon (AC), we obtained a high specific energy of 28.8 Wh kg⁻¹ with appreciable stability in aqueous electrolytes whereas in nonaqueous electrolyte there is an obvious increase in energy density (35 Wh kg⁻¹) due to wider potential window. That is, a full cell version of LIC, AC|Li⁺|LMP, was fabricated and demonstrated its facile cycling characteristics via removal/insertion of Li⁺ within nC-LMP (positive electrode) and the electrosorption of Li⁺ into mesoporous carbon (AC) (negative electrode). Such cells ensured a typical battery-like charging and EDLC-like discharging characteristics of LIC type electrochemical capacitors (ECs) which are desired to enhance safety and energy densities.     

Gallium nitride electrodes for membrane-based electrochemical biosensors

We report on the deposition of planar lipid bilayers (supported membranes) on gallium nitride (GaN) electrodes for potential applications as membrane-based biosensors. The kinetics of the lipid membrane formation upon vesicle fusion were monitored by simultaneous measurements of resistance and capacitance of the membrane using AC impedance spectroscopy in the frequency range between 50mHz and 50kHz. We could identify a two-step process of membrane spreading and self-healing. Despite its relatively low resistance, the membrane can be modeled by a parallel combination of an ideal resistor and capacitor, indicating that the membrane efficiently blocks the diffusion of ions.