WO2012030415A1 - Ultracondensateur faisant appel à une nouvelle variété de carbone - Google Patents

Ultracondensateur faisant appel à une nouvelle variété de carbone Download PDF

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Publication number
WO2012030415A1
WO2012030415A1 PCT/US2011/036164 US2011036164W WO2012030415A1 WO 2012030415 A1 WO2012030415 A1 WO 2012030415A1 US 2011036164 W US2011036164 W US 2011036164W WO 2012030415 A1 WO2012030415 A1 WO 2012030415A1
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mego
product
graphite oxide
carbon
electrolyte
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PCT/US2011/036164
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English (en)
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Rodney S. Ruoff
Yanwu Zhu
Meryl Stoller
Shanthi Murali
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Board Of Regents, The University Of Texas System
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Priority claimed from US12/875,880 external-priority patent/US20110080689A1/en
Application filed by Board Of Regents, The University Of Texas System filed Critical Board Of Regents, The University Of Texas System
Publication of WO2012030415A1 publication Critical patent/WO2012030415A1/fr
Priority to US13/782,329 priority Critical patent/US9412484B2/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • C01B32/23—Oxidation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Definitions

  • the present disclosure relates to capacitors, and specifically to carbon materials that can be used in capacitors.
  • Ultracapacitors also called supercapacitors or electrochemical capacitors
  • supercapacitors are a potential solution for meeting the world's electrical energy storage needs.
  • Ultracapacitors store energy by forming a double layer of electrolyte ions on the surface of conductive electrodes. Ultracapacitors are not limited by the electrochemical charge transfer kinetics of batteries and thus can operate at very high charge and discharge rates, and can have lifetimes of over a million cycles; however, the energy stored in ultracapacitors is currently an order of magnitude lower than batteries. The limited energy storage of ultracapacitors limits their use to those applications that require high cycle life and power density.
  • the energy density of conventional state-of-the-art ultracapacitor devices mainly based on porous activated carbon (AC), is about 4-5 Wh/Kg while that of lead acid batteries is in the range 26-34 Wh/Kg.
  • a conventional AC material with a specific surface area (SSA) in the range of 1,000-2,000 m 2 /g and a pore size distribution in the range of 2-5 ran, can have a gravimetric capacitance of 100-120 F/g in an organic electrolyte.
  • SSA specific surface area
  • this disclosure in one aspect, relates to capacitors, and specifically to carbon materials that can be used in capacitors.
  • the present disclosure provides a method for making activated microwave expanded graphite oxide comprising expanding and reducing graphite oxide with microwave radiation to produce MEGO; and chemically activating the MEGO.
  • FIG. 1 is a (A) schematic showing the microwave exfoliation/reduction of graphite oxide and the following chemical activation of microwave exfoliated graphite oxide (MEGO) with potassium hydroxide (KOH), (B) low magnification scanning electron microscopy (SEM) image of a 3D activated MEGO (a-MEGO) chunk, (C) high-resolution SEM image of a different sample region of the same chunk, (D) annular dark-field scanning transmission electron microscopy (ADF-STEM) image of the same area depicted in (C), (E) a high magnification phase contrast electron microscopy image of the thin edge of an a-MEGO chunk, taken at 80 kV, and (F) exit wave reconstructed high resolution transmission electron microscopy (HRTEM) image from the edge of a-MEGO.
  • ADF-STEM annular dark-field scanning transmission electron microscopy
  • FIG. 2 illustrates the BET specific surface area of a-MEGO versus the KOH to MEGO loading ratio in the mixture before activation.
  • FIG. 3 illustrates (A) low magnification SEM, (B) high magnification SEM, and (C) ADF-STEM images of a-MEGO, where B and C were simultaneously taken from region 1 of (A), showing larger pores of between 2-10 nm; (D) very high magnification SEM and (E) ADF-STEM images simultaneously taken from region 2 of (A), and (F) acquired from the region outlined as a box in (E).
  • FIG. 4 illustrates electron paramagnetic resonance (EPR) data of a-MEGO having a SSA of about 2,520 m 2 /g, with DPPH used as a standard.
  • EPR electron paramagnetic resonance
  • FIG. 5 illustrates (A) synchrotron powder X-ray diffraction (XRD) data of a sample of a-MEGO material having a specific surface area (SSA) of about 2,520 m 2 /g, plotted as Cu Koc, (B) X-ray photoelectron spectroscopy (XPS) of the C Is region and the K 2p region (inset), and (C) electron energy loss spectroscopy (EELS) data for a-MEGO and graphite.
  • XRD synchrotron powder X-ray diffraction
  • SSA specific surface area
  • XPS X-ray photoelectron spectroscopy
  • EELS electron energy loss spectroscopy
  • FIG. 6 illustrates XPS data of an a-MEGO sample having a SSA of about 2,520 m 2 /g (A) fit to the C Is region, and (B) the O Is region.
  • FIG. 7 illustrates (A) Raman spectroscopy and (B) Fourier transform infrared spectroscopy data for an a-MEGO sample and a MEGO control sample.
  • FIG. 8 illustrates (A) high resolution, low pressure N 2 (77.4 K) and Ar (87.3 K) isotherms, together with the C0 2 (273.2 K) isotherm (inset), and (B) cumulative pore volume and pore size distribution (inset) for N 2 , calculated using a slit/cylindrical NLDFT model, and C0 2 , calculated using a slit pore NLDFT model, both from gas adsorption/desorption analysis of an a-MEGO sample having a SSA of about 3,100 m 2 /g.
  • FIG. 9 illustrates (A) N 2 (77.4 K) isotherms, and (B) cumulative pore volume versus pore diameter obtained from (A) obtained during adsorption/desorption analysis of an a- MEGO sample having an SSA of about 2,520 m 2 /g and using a MEGO control sample.
  • FIG. 10 illustrates the quenched solid density functional theory (QSDFT) pore size distribution of an a-MEGO sample.
  • QSDFT quenched solid density functional theory
  • FIG. 11 illustrates (A) cyclic voltammetry (CV) curves for various scan rates of an a- MEGO material having a SSA of about 2,400 m 2 /g in a BMIM BF 4 AN electrolyte, (B) galvanostatic charge/discharge curves under differing constant currents, (C) Nyquist plot, illustrating the imaginary and real components of the impedance, with high frequency inset, and (D) frequency response of the gravimetric capacitance of an a-MEGO supercapacitor.
  • CV cyclic voltammetry
  • FIG. 12 illustrates (A) cyclic voltammetry (CV) curves for various scan rates of an a- MEGO material having a SSA of about 3,100 m 2 /g in a 1.0 M TEA BF 4 AN electrolyte, (B) galvanostatic charge/discharge curves under differing constant currents, (C) Nyquist plot, illustrating the imaginary and real components of the impedance, and (D) frequency response of the gravimetric capacitance of an a-MEGO supercapacitor.
  • CV cyclic voltammetry
  • FIG. 13 illustrates data from constant life cycle stability testing of an a-MEGO based supercapacitor in neat BMIM BF 4 , where the a-MEGO had an SSA of about 3,100 m 2 /g.
  • FIG. 14 illustrates (A) cyclic voltammetry (CV) curves for various scan rates of an a- MEGO material having a SSA of about 3,100 m 2 /g in neat EMIM TFSI electrolyte, and (B) galvanostatic charge/discharge curves under differing constant currents.
  • CV cyclic voltammetry
  • FIG. 15 illustrates illustrates (A) high resolution, low pressure isotherms, and (B) pore size distribution for N 2 adsorption, calculated using a slit/cylindrical NLDFT model, from N 2 adsorption/desorption analysis of an activated thermally exfoliated graphite oxide (a-TEGO) sample having a BET SSA of about 2,675 m 2 /g.
  • a-TEGO activated thermally exfoliated graphite oxide
  • FIG. 16 illustrates (A) cyclic voltammetry (CV) curves for various scan rates of an a- TEGO material having a SSA of about 2,700 m 2 /g in BMIM BF 4 /AN electrolyte, (B) galvanostatic charge/discharge curves under differing constant currents, (C) Nyquist plot, illustrating the imaginary and real components of the impedance, and (D) frequency response of the gravimetric capacitance of an a-MEGO supercapacitor.
  • CV cyclic voltammetry
  • Ranges can be expressed herein as from “about” one particular value, and/or to "about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as "about” that particular value in addition to the value itself. For example, if the value "10” is disclosed, then “about 10" is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.
  • compositions of the invention Disclosed are the components to be used to prepare the compositions of the invention as well as the compositions themselves to be used within the methods disclosed herein. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds can not be explicitly disclosed, each is specifically contemplated and described herein. For example, if a particular compound is disclosed and discussed and a number of modifications that can be made to a number of molecules including the compounds are discussed, specifically contemplated is each and every combination and permutation of the compound and the modifications that are possible unless specifically indicated to the contrary.
  • compositions disclosed herein have certain functions.
  • the present disclosure provides a carbon material that can be used in a capacitor, such as, for example, an ultracapacitor.
  • a capacitor such as, for example, an ultracapacitor.
  • Ultracapacitors also called supercapacitors or electrochemical capacitors, are a potential solution to meeting the world's electrical energy storage needs. Vastly accelerated adoption of ultracapacitor technology, now mainly based on porous carbons, is currently hindered by their low energy storage density and relatively high effective series resistance.
  • the present disclosure provides, in various aspects, a new carbon material obtained through the chemical activation of microwave exfoliated graphite oxide (MEGO).
  • MEGO microwave exfoliated graphite oxide
  • this new type of carbon (hereinafter referred to as activated MEGO, or a-MEGO) has at least one of: a high surface area of up to about 3,100 m 2 /g or more, a high electrical conductivity, a low O and H content with strong evidence of primarily sp 2 bonding, a novel pore structure, or a combination thereof.
  • the carbon material or a portion thereof can be a negative curvature carbon allotrope.
  • two-electrode ultracapacitor cells constructed with a-MEGO electrodes and ionic liquid (IL) electrolytes can yield significantly higher gravimetric capacitance than other conventional electrode materials used with ionic liquid electrolytes, with energy and power densities exceeding those of commercially available ultracapacitors by a factor of at least about 4 and 10, respectively.
  • IL ionic liquid
  • Ultracapacitors store energy by forming a double layer of electrolyte ions on the surface of conductive electrodes. Ultracapacitors are not limited by the electrochemical charge transfer kinetics of batteries and thus can operate at very high charge and discharge rates, and can have lifetimes of over a million cycles; however, the energy stored in conventional ultracapacitors can be about an order of magnitude lower than batteries. Such lower energy storage values can limit the adoption of ultracapacitors to applications that require high cycle life and power density. In one aspect, the energy density of conventional ultracapacitor devices, mainly based on porous activated carbon (AC), is about 4-5 Wh/Kg, while that of lead acid batteries is in the range 26-34 Wh/Kg.
  • AC porous activated carbon
  • CNTs Carbon nanotubes
  • SWNTs single walled CNTs
  • Graphene has a theoretical SSA of 2,630 m 2 /g and a very high intrinsic in-plane electrical conductivity, as well as high mechanical strength and chemical stability.
  • Graphene- based materials derived from graphite oxide (GO) can also be manufactured in industrial quantities at relatively low cost.
  • Graphene can be made using any of a variety of known methods. Specific methods for obtaining chemically-modified graphene are also disclosed in Park and Ruoff, "Chemical methods for the production of graphenes," Nat. Nanotechnol:29 (March, 2009), incorporated herein by reference for the purpose of disclosing graphene synthetic methods.
  • graphene can be produced by reducing graphene oxide with a reducing agent.
  • Example reducing agents include anhydrous hydrazine, hydrazine monohydrate, dimethyl hydrazine, sodium borohydride, hydroquinone, alkaline solutions, and alcohols. Hydrogenation/hydrogen transfer techniques employing small molecule reduced species as hydrogen sources and graphene oxide as the hydrogen sink may also be used. Catalysts, such as tris(tripenylphosphine) rhodium chloride can optionally be used as activators of hydrogen that is produced during oxidation of a hydrogen source.
  • Ultracapacitors based on reduced graphene oxide with capacitance values of approximately 130 F/g in aqueous KOH or 100 F/g in organic electrolytes have been developed.
  • Other graphene-based materials derived from GO can have high end capacitance values of -200 F/g in aqueous electrolytes, -120 F/g in organic electrolytes, and -75 F/g in an ionic liquids.
  • high frequency ultracapacitors prepared from oriented graphene grown on nickel surfaces can provide efficient filtering of 120 Hz current with an RC time constant of less than 0.2 ms, but such performance is at the cost of low effective energy storage due to the very low density of the electrode material.
  • the present disclosure provides an activation method with, for example, KOH, for processing microwave exfoliated graphite oxide (MEGO) and/or thermally exfoliated graphite oxide (TEGO), to achieve SSA values up to about 3,100 m /g or more.
  • an 'activated MEGO' (a-MEGO) material can be obtained.
  • the inventive a-MEGO is a novel carbon with a unique porous structure, and can yield very high gravimetric capacitance values, low ESR values in commercially available ionic liquid and/or organic electrolytes, or a combination thereof.
  • the inventive process simultaneously increases the surface area accessible by electrolyte ions while maintaining the high electrical conductivity, resulting in high energy and power density in two-electrode ultracapacitor cells.
  • a new type of highly porous carbon is generated that is not graphene.
  • the inventive carbon can be similar in structure to 'negative curvature carbon'.
  • chemical activation such as, for example, KOH activation
  • a resulting a-MEGO material can enable the supercapacitor to having enhanced performance as compared to supercapacitors comprising conventional materials.
  • a MEGO powder can be prepared by exposing GO to microwave energy.
  • the microwave energy can be from about 300 MHz to about 300 GHz.
  • the microwave energy can be from about 1 to about 10 GHz.
  • the microwave energy can be about 2.45 GHz.
  • the source of microwave energy can be any source suitable for use in the methods of the present disclosure.
  • a microwave source can comprise a magnetron, klystron, gyrotron, field effect transistor, tunnel diode, Gunn diode, IMP ATT diode, or a combination thereof.
  • a MEGO powder can be prepared by irradiating GO in a conventional (e.g., domestic) microwave oven.
  • the intensity of the microwave energy can also vary, depending, upon, for example, the specific material and degree of expansion desired.
  • the microwave energy is from about 100 to about 2,500 W, or from about 700 to about 1,500 W.
  • the length of time for which a material is subjected to microwave irradiation can vary.
  • the intensity of the microwave radiation and/or the length of time for which the material is exposed to the microwave energy is sufficient to at least partially expand the GO powder.
  • the length of time can be at least about 10 seconds, for example, about 10, 20, 30, 40, 50, 60, 80, 100, 200, 300, or more seconds.
  • a GO powder can be exposed to microwave radiation of about 2.45 GHz and about 1,100 W for a period of about 1 minute.
  • GO materials be prepared using known methods, and one of skill in the art could readily prepare a suitable GO material for use in the methods of the present disclosure.
  • the MEGO powder can be contacted with an activator, after which, the powder can optionally be filtered and dried.
  • the resulting material is a mixture of MEGO and an activator, such as, for example, MEGO/KOH, that can be chemically activated.
  • the mixture of MEGO and activator does not have to be filtered and/or dried, prior to a heat treatment step as described herein.
  • the activator can comprise a basic material, such as, for example, KOH or an aqueous solution thereof.
  • the activator can comprise a redicing agent.
  • an activator can comprise one or more other compounds suitable for use in preparing an activated MEGO material.
  • an activator can comprise zinc chloride, aluminium chloride, magnesium chloride, boric acid, nitric acid, phosphoric acid, potassium hydroxide, sodium hydroxide, or a combination thereof.
  • the mixture can be subjected to a heat treatment step.
  • the heat treatment step can comprise exposing the mixture to a flowing stream of an inert and/or a reducing gas at elevated temperature for a period of time.
  • the gas comprises argon.
  • the gas or mixture of gases can comprise other inert and/or reducing gases.
  • the environment e.g., furnace tube
  • the temperature of a heat treatment step can vary depending on the degree of activation desired and the specific materials being processed. In one aspect, the temperature is a temperature sufficient to at least partially activate the MEGO material. In another aspect, the temperature can vary if different gases are used. In other aspects, the duration of a heat treatment step can be from about 30 minutes to about 5 hours, for about about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 hours. In a specific aspect, a heat treatment step can be from about 1 to about 2 hours. In other aspects, a heat treatment step can be less than about 0.5 hours or greater than about 5 hours, and the present invention is not intended to be limited to any particular length of time for a heat treatment step. One of skill in the art, and in possession of this disclosure, could readily determine appropriate activation conditions for preparation of an a-MEGO material.
  • the MEGO and/or mixture of MEGO and base can be positioned in a tube furnace under, for example, a flowing argon stream at a pressure of about 400 Torr. The mixture can then be heated at about 800 °C for about one hour.
  • FIG. 1 A illustrates an exemplary schematic of an activation process, as described herein. While not wishing to be bound by theory, the chemical activation process can occur according to the following reaction scheme:
  • phosphoric acid can be used for activation, wherein the acid reacts with the carbon source at temperature less than 450 °C, leading to what has described as C-C bond weakening and formation of a cross-linked structure. This likely reduces the release of volatile materials, lowers the activation temperature, and increases the carbon yield.
  • the activated MEGO after activation, at least a portion of the activated MEGO is not graphene. In still another aspect, after activation, the MEGO material is not grapheme, but rather has a unique structure as described herein.
  • FIG. IB illustrates the microstructure of an exemplary a-MEGO material, prepared as described herein.
  • FIGS. 1C-1F illustrate (C) high resolution SEM, (D) annular dark field scanning transmission electron microscopy (ADF-STEM), and (E-F) high-resolution TEM (HR-TEM) images of the microstructure of the a-MEGO material.
  • ADF-STEM annular dark field scanning transmission electron microscopy
  • E-F high-resolution TEM
  • chemical activation can generate a plurality of pores in the carbon material.
  • the pore distribution and specific surface area can play significant roles in high gravimetric capacitance values, and the types of surfaces that are present and accessible to the electrolyte are likely critically important to good compatibility with a wide range of electrolytes with different ion sizes, such as the ELs and the organic electrolytes described herein.
  • chemical activation can generate a three-dimensional network of pores in the carbon material.
  • all or a portion of the pores generated in the carbon material can comprise mesopores.
  • at least a portion of the pores generated in the carbon material can have a diameter of from less than about 1 nm to about 10 nm.
  • at least a portion of the pores can be smaller than 1 nm or greater than 10 nm, and the present disclosure is not intended to be limited to any particular pore size and/or distribution.
  • the SSA of the resulting material can be controlled by varying the ration of MEGO to base and/or reducing agent.
  • FIG. 2 illustrates exemplary SSA values obtainable by varying the KOH/MEGO ratio.
  • chemical activation can, in one aspect, at least partially digest the MEGO material. In another aspect, chemical activation can restructure at least a portion of the MEGO material. It should be noted that statistical quantitation of the resulting pores by electron microscopy techniques can be difficult.
  • chemical activation can produce an a-MEGO material having a dense pore structure, wherein at least a portion of the walls of the pores comprise curved carbon sheets.
  • at least a portion of these curved carbon wall sheets are a single layer thickness.
  • an a-MEGO material can be comprised of a plurality of n- membered rings in plane, where n varies between about 5 and about 8. As illustrated in the exit wave reconstructed image of FIG. IF, the in-plane cystallinity can, in various aspects, be preserved even as the sheets bend through relatively high degrees of curvature.
  • the chemically activated a-MEGO material can, in one aspect, have a BET surface area of up to about 3,100 m 2 /g, for example, about 1,000, 1,200, 1,300, 1 ,500, 1,800, 2,000, 2,200, 2,400, 2,600, 2,800, 3,000, 3,100 m 2 /g, or more.
  • the chemically activated a-MEGO can exhibit a high electrical conductivity, such as, for example, up to about 500 S/m or more.
  • an a- MEGO material can have a powder electrical conductivity of about 200, 250, 300, 350, 400, 450, 500, 550 S/m, or more.
  • the chemically activated a-MEGO can exhibit a low oxygen content, a low hydrogen content, or a combination thereof.
  • an a-MEGO material can have a C/O atomic ratio of up to about 35, for example, about 20, 24, 26, 28, 30, 32, 34, 35, or greater.
  • an a-MEGO material can have a hydrogen content less than about 0.5 wt.% or less than about 0.3 wt.%. In another aspect, an a-MEGO material can have a hydrogen content less than the threshold detection limit by elemental analysis.
  • At least a portion of a chemically activated a-MEGO material comprises sp 2 carbon.
  • At least a portion of an a-MEGO material can comprise a low, for example, ppm level, unpaired spin count as determined by electron paramagnetic resonance (EPR), as illustrated in FIG. 4.
  • EPR electron paramagnetic resonance
  • a-MEGO prepared in accordance with the methods described herein can, in one aspect, be comprised primarily of single carbon sheets.
  • Other analyses of a-MEGO materials such as synchrotron powder X-ray diffraction (XRD; FIG. 5A) and X-ray photoelectron spectroscopy (FIG. 5B) are consistent with images obtained via HR-TEM, indicating predominately single carbon sheets.
  • XRD and XPS studies show a reduced intensity for the (002) peak.
  • the low-angle scatter observed for a-MEGO materials as compared to MEGO (not activated) is also consistent with the presence of a high density of pores in the a-MEGO material.
  • the Cls region of the XPS spectrum (FIG. 5B) for a MEGO material illustrates a tail between about 286 eV and about 290 eV that, in one aspect, can be attributed to C-0 groups and energy loss shake-up features.
  • the activated material a- MEGO
  • the presence of such oxygen containing groups was suppressed, with two new peaks appearing between about 292 eV and about 296 eV.
  • These new peaks can be attributed to potassium residue, primarily as K 2 C0 3 with a small amount of KOH.
  • the resulting XPS spectra will vary.
  • quantification of the amount of sp -bonding can be determined by measuring the ratio between ⁇ * bonding and ⁇ *+ ⁇ * bonding using, for example, electron energy loss spectroscopy (EELS).
  • FIG. 5C illustrates a comparison of the carbon K near edge structure for both a-MEGO and graphite samples of equivalent thickness. Assuming 100% sp 2 bonding in the graphite reference spectra, the a-MEGO sample can have about 98% ( ⁇ 2%) sp 2 bonding. Complementary measurements can also be made by XPS (FIG. 6), providing similar results. In addition, micro Raman spectroscopy (FIG. 7A) and Fourier transform infrared spectroscopy (FIG. 7B) techniques can be utilized to reinforce and understand the specific structure of a particular a-MEGO material.
  • EELS electron energy loss spectroscopy
  • FIG. 8 illustrates data obtained from coupling nitrogen (77.4 K) and argon (87.3 K)
  • ultramicropores i.e., pores having a width of less than about 1 nm.
  • the isotherms from these experiments can reveal details of the low-pressure region where micropore filling occurs, as well as pore condensation and type H2 hysteresis.
  • the experimental data from a-MEGO samples indicates an interconnected pore system with constrictions.
  • FIG. 9 illustrates data obtained from similar analysis of a MEGO (unactivated) control sample), indicating a significantly smaller pore volume than that obtained for the a-MEGO material.
  • the smaller pore volume can be attributed to the platelet like structure in MEGO materials, whereas the pores in a-MEGO materials can exhibit a well-defined micro-mesopore size distribution as in FIG. 8B, with a significant increase in pore volume of up to about 2.14 cm 3 /g relative to MEGO materials.
  • the obtained pore size/volume distribution indicates that a-MEGO is a unique material because of the existence of well-defined micro- and mesopores.
  • a-MEGO can exhibit micropores having a width of about 1 nm, as well as narrow mesopores with an average width of about 4nm.
  • FIG. 10 further illustrates the pore size distribution of an exemplary a-MEGO material, calculated using a quenched solid density functional theory (QSDFT) which can account for surface roughness of the material.
  • QSDFT quenched solid density functional theory
  • the inventive a-MEGO material can be utilized as a component of an electrode, for example, in a supercapacitor.
  • a supercapacitor designs and electrode designs for use in supercapacitors are known, and one of skill in the art could readily select an appropriate supercapacitor, electrode, and/or cell design for use with the compositions and methods of the present invention.
  • a voltage potential can be applied across the electrodes of the supercapacitor, such that one electrode becomes positively charged and the other becomes negatively charged. Negatively charged ions in the electrolyte cover the surfaces of the positively charged electrode, while positively charged ions in the electrolyte cover the surfaces of the negatively charged electrode, a result of the
  • a supercapacitor comprises one or more graphene-based electrodes, an electrolyte, and a dielectric separator that can divide the supercapacitor into two chambers, wherein each of the two chambers comprises an electrode and a portion of electrolyte.
  • the electrolyte is an ionic liquid and/or comprises an ionic liquid.
  • Ionic liquids are typically salts that melt at temperatures below 100 °C. They are typically composed of discrete ions or loosely associated ions, each of which offers a unique set of materials properties. These properties can be unavailable from neutral organic compounds, crystalline inorganic salts, or common solvents, such as water. Ionic liquids can exhibit suitable aspects of one or more of the following properties: high conductivity, high chemical stability, high thermal stability, or high electrochemical stability, large
  • an ionic liquid can be used at high potentials, such as, for example, 2.0 V or higher.
  • the melting point of an ionic liquid can be decreased by using liquids with lower anion/cation interactions or with more diffuse charge structures. Melting points can also be decreased by, for example, using asymmetric ionic liquids as well as by introducing various types of synthetic oligomers or polymers as pendant functionalities.
  • the viscosity of an ionic liquid can be decreased by the presence of perfluorinated anions and oligomer or polymer substituents.
  • Linked moieties possessing multiple charged components can also lower viscosity while simultaneously increasing thermal stability.
  • the electrochemical window of ionic liquids can be broadened by adding fluorinated alkyl chains to the cation. In some aspects, this can cause dramatic ' differences in the local electronic environments.
  • the anions can be fluorinated anions, such as, for example, bistriflimide, or a dicyanamide anion.
  • the thermal stability of an ionic liquid can be increased by linking multiple charged groups together or through the use of fluorinated components.
  • Reactivity as a function of temperature can also be used to select ionic liquids that are more thermally stable at ultracapacitor operation and/or storage temperatures.
  • any suitable ionic liquid based electrolyte can be used in conjunction with one or more electrodes in an electrochemical cell.
  • these can comprise ionic liquids with ammonium cations, imidazolium cations, or a combination thereof.
  • these cations can be paired with tetrafiuoroborate or
  • an ionic liquid can comprise a cyclic ammonium- or phosphonium- based composition.
  • an ionic liquid can comprise a spirocyclic
  • an ionic liquid can comprise a N-methyl-N-alkyl pyrrolidinium bistriflimide.
  • an ionic liquid can comprise pyrrolidinium salts as cations, wherein the inclusion of a longer alkyl chain can decrease the melting point of the ionic liquid.
  • an octyl-functionalized cation can have a melting point of about -15.2 °C.
  • a cation/anion combination with a desired melting point can be selected by one of skill in the art.
  • an ionic liquid can be a pyrrolidinium-based ionic liquid having a melting point lower than about -10 °C, a non-pyrrolidinium-based cyclic ammonium, a phosphonium-based cyclic ammonium, or a combination thereof.
  • an ionic liquid can comprise an N-methyl-N-alkyl pyrrolidinium bistriflimide ionic liquid having a melting point of about -10 °C or lower.
  • an ionic liquid can be a spirocyclic ammonium- or phosphonium -based ionic liquid.
  • an ionic liquid can comprise an acyclic ammonium- or phosphonium-based ionic liquid.
  • an ionic liquid can comprise a combination of one or more ionic liquids recited herein or otherwise known in the art.
  • an ionic liquid can comprise l-Butyl-3-methyl-imidazolium tetrafluoroborate, BMBVI BF 4 , l-Ethyl-3-methylimidazolium
  • an ionic liquid can comprise one or more ionic liquids not specifically recited herein, and the present invention is not intended to be limited to any particular ionic liquid.
  • the ionic liquid is a mixture of two or more ionic liquids, and/or a mixture of an ionic liquid and another non-ionic electrolyte.
  • an organic electrolyte can comprise TEA BF 4 in AN electrolyte.
  • an organic electrolyte can comprise other species or mixtures of species not recited herein.
  • an ammonium-based ionic liquid comprising N,N-diethyl-N- methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl) amide can be used.
  • This composition is non-flammable, operates in a wide potential window (5.4 V) and has a high ionic conductivity (4.0 mS/cm at 30 °C).
  • an ionic liquid or mixture of ionic liquids can exhibit high electrochemical stability, such as, for example, that or quarternary ammonium salts and/or pyrrolidinium salts.
  • an ionic liquid can comprise from about 1 wt.% to about 100 wt.% of an electrolyte, for example, about 1, 2, 3, 4, 5, 7, 9, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 34, 36, 38, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100 %.
  • an electrolyte can comprise a solvent, such as, for example, acetonitrile, benzonitrile, and/or other low boiling nitriles, propylene carbonate, ethylene carbonate, dimethyl carbonate, and combinations thereof.
  • an electrolyte can comprise other solvents and/or mixtures of solvents not specifically recited herein. For example, mixtures of ionic liquids can exploit the unique solvent properties of individual ionic liquids for dissolution of neutral additives.
  • an electrolyte can comprise a lithium containing electrolyte, such as, for example, LiBF 4 /AN, LiPFe/EC/DEC, Li-TFSI, Li 2 S04, LiOH, or a combination thereof.
  • an electrolyte can comprise Li-TFSI dissolved in an ionic liquid, such as, for example, EMIM-TFSI.
  • an electrolyte can comprise a mixture of any of the ionic liquids, non-ionic liquids, and/or lithium containing electrolytes described herein, optionally with other electrolyte components known in the art.
  • an electrolyte can comprise H 2 S0 4 .
  • an electrolyte can comprise an ionic liquid or mixture of ionic liquids and another, non-ionic liquid, such as an exogenous solvent.
  • the other liquid can be present in various amounts and can help render the viscosity or melting point of the electrolyte as a whole suitable for a particular ultracapacitor.
  • 10 wt% acetonitrile can be used in an electrolyte when a triflate ionic liquid is used, as triflate containing ionic liquids can be tacky solids at room temperature.
  • acetonitrile can have a deleterious effect of dilution in an ionic liquid, it can significantly decrease the viscosity and melting point of the mixture as compared to ionic liquid alone.
  • the melting point of a mixture can be decreased to nearly that of the solvent alone (e.g, -45 °C).
  • a decreased melting point and increased electrolyte viscosity can improve the ultracapacitor performance as a whole because it can facilitate greater ion mobility, allowing faster and more efficient charging and discharging.
  • an ionic liquid can be anhydrous or substantially anhydrous before it is disposed in an supercapacitor, after it is assembled into the supercapacitor, or both.
  • any residual water content of materials used in the electrodes can be sufficiently low to preserve the anhydrous or substantially anhydrous state of the ionic liquid.
  • an anhydrous ionic liquid can have a water content of less than about 10 ppm, for example, less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 ppm.
  • an anhydrous liquid can have a sufficiently low concentration of water so as to avoid detectable hydrolysis products in a supercapacitor during the life of the supercapacitor.
  • At least one electrode of a cell comprises a graphene-based material, such as, for example, a-MEGO, that is compatible with the electrolyte.
  • any one or more other other electrodes can comprise any suitable material that is compatible with the electrolyte.
  • one or more of the electrodes can be optimized to provide large surface area and compact or small charge separation so as to improve the energy density of the supercapacitor.
  • one of electrodes is not graphene-based and can comprise a different carbon electrode material, such as, for example, activated carbon.
  • one or more electrodes can be made of chemically-modified graphene or a graphene that has been expanded by exposure to microwave radiation followed by chemical activation as described herein.
  • Chemically-modified graphene can demonstrate one or more of the following improvements as compared to activated carbon electrodes: ability to be synthesized with different methods into various morphologies and chemical functionalities, very high surface area to allow large potential gains and high energy density, compatibility with high voltage electrolytes, suitable conductivity without additives, low equivalent series resistance in ultracapacitors allowing improved energy efficiency and less resistive heating during high current loads, improved resistance to deleterious effects of water, and elimination of water and hydrolysis products.
  • an electrode can comprise a carbon composition such as that described in U.S. Provisional Patent Application 61/144,898, PCT Publication No. PCT/US2009/041768, U.S. Patent Application 12/430,240, U.S. Patent Application 11/976,574, PCT Publication No. PCT/US2004/032585, and/or U.S. Patent Application 10/ 574,507, each of which is hereby incorporated by reference for the purpose of disclosing carbon compositions suitable for use in an electrode.
  • At least one electrode comprises a-MEGO which was produced by by exposing a graphite-oxide derived carbon to microwave radiation and subsequently chemically activating the carbon to further reduce it, for example using 1-10 M KOH at a temperature of from about 200 °C to about 1,000 °C for several hours.
  • Such an electrode can, in various aspects, be used in conjunction with electrolytes containing propylene- carbonate or acetonitrile or ionic-liquids discussed later or a combination thereof.
  • an a-MEGO material having a SSA of about 1,280 m 2 /g can exhibit a capacitance of about 122 F/g, when used in a BMIM BF AN electrolyte.
  • FIG. 11A illustrates cyclic voltammetry analysis of the cells, showing rectangular curves from 0 V to 3.5 V over a wide range of scan rates.
  • FIG. 1 IB illustrates galvanostatic charge/discharge curves with specific capacitance values of 165 F/g (at 1.4 A/g), 166 F/g (at 2.8 A/g), and 166/g (at 5.7 A/g).
  • the exemplary a-MEGO samples When expressed in volumetric terms, the exemplary a-MEGO samples had a capacitance of about 60 F/cm 3 . Moreover, at the initiation of discharge, the a-MEGO sample exhibited a voltage drop of 0.034 V (i 0 of 1.4 A/g), indicating a very low ESR in the test cell. In another aspect, analysis of the frequency response over the range from 500 kHz to 5 mHz produced the Nyquist plot shown in Fig. 11C. The plot features a vertical curve, indicating a nearly ideal capacitive behavior of the cell.
  • capacitance of the a-MEGO in BMIM BF 4 /AN electrolyte can decrease sharply at about 4 Hz and remains at about 0.035 F at 10 Hz.
  • Performance of the same a-MEGO material in TEA BF 4 /AN electrolyte was evaluated, where a specific capacitance greater than 150 F/g was obtained from a discharge curve with a constant 0.8 A g current and an ESR or 4.62 ⁇ (FIG. 12).
  • the inventive a-MEGO material can exhibit the highest gravimetric capacitance known to date in an organic electrolyte for any carbon derived from graphene-based materials.
  • energy and power density can be estimated based on measurements of the supercapacitor test cell in BMIM BF AN
  • the energy density of an a- MEGO material can be about 70 Wh/kg. In other aspects, the energy density of an a-MEGO material can be at least about 60, at least about 70, at least about 75, at least about 80 Wh/kg, or more.
  • the methods fo the present disclosure can provide an a-MEGO material having a density of at least about 0.2 g/cc, at least about 0.4 g/cc, at least about 0.6 g/cc, at least about 0.8 g/cc, or at least about 1 g/cc.
  • an a-MEGO material can have a density of about 0.2 g/cc.
  • an a-MEGO material can have a density of about 0.6 g/cc.
  • the a-MEGO material can exhibit a volumetric capacitance of at least about 100 F/cc (i.e., about 166 F/g), or at least about 120 F/cc (i.e., about 200 F/g).
  • an a-MEGO material can have a density of about 1 g/cc.
  • the a-MEGO material can have a volumetric capacitance of at least about 200 F/cc.
  • the a-MEGO material can exhibit an energy density of about 85 kW/kg (normalized with carbon), representing a volumetric density of about 51 kW/L for a material having a density of about 0.6 g/cc and about 85 kW/L for a material having a density of about 1 g/cc.
  • a practical energy density of greater than about 20 Wh/kg can be achieved for a packaged supercapacitor device, based on a weight ratio of 30% for the active electrode material in the device. This is 4 times higher than existing AC-based
  • the power density can be about 250 kW/kg, as estimated by using the voltage drop and ESR obtained from the discharge curve.
  • the power density of ⁇ 75 kW/kg is one order higher than the values from commercial carbon supercapacitors that have energy density values of 4-5 Wh/kg.
  • an a-MEGO material, in an electrochemical cell can exhibit a power density of at least about 200, at least about 225, at least about 250, at least about 275, at least about 300 kW/kg, or more.
  • the performance of a-MEGO can be higher when used with small diameter ions.
  • the measured gravimetric capacitance of a-MEGO (SSA ⁇ 3100 m 2 /g) at 3.5 V and a current density of 0.7 A/g is 200 F/g, with an ESR of 8.6 ⁇ .
  • the curves in FIG. 14 are not as ideal as those from a-MEGO in either BMEVI BFVAN or TEA BF 4 /AN electrolyte.
  • the two-electrode supercapacitor cells constructed with a-MEGO electrodes showed a higher gravimetric capacitance in AN-based electrolytes than any other carbon derived from graphene-based materials.
  • the energy density for an ionic liquid based fully packaged cell for example, l-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI), can be about 25.5 Wh/Kg, or about the same as that of a conventional lead acid battery.
  • the processes used to synthesize the inventive carbon material are readily scalable to industrial levels.
  • Electrodes can be the same thickness used in commercial cells and testing can be performed using commercial collectors, separators, binders, and electrolytes.
  • the methods to prepare a-MEGO materials can be easily scaled to industrial levels. For example, the inventive methods described herein can be applied to TEGO (FIGS. 15 and 16), which is currently manufactured in ton quantities.
  • the a-MEGO material can be stable, for example, when used in an electrochemical cell and/or a supercapacitor.
  • the a-MEGO material can be stable for a number of charge/discharge cycles, for example, up to about 200,000, 500,000, or 1,000,000 cycles.
  • the a-MEGO can be stable over a range of temperatures that can be encountered during operation of a supercapacitor, for example, from about -20 °C to about 300 °C, including all ranges and subranges therebetween.
  • a-MEGO materials described herein, together with the methods to prepare a- MEGO materials can also be useful hydrogen storage applications, gas adsorption
  • the inventive a-MEGO material is disposed in an electrode of a supercapacitor.
  • the inventive a-MEGO material is disposed in a fuel cell electrode as a catalyst support.
  • the inventive a-MEGO material is disposed in an electrode of a lithium ion battery.
  • the inventive a-MEGO material can be disposed in an electrode of an energy storage and/or conversion device, or in an analyzer as an adsorption media.
  • Graphite oxide (GO) powders made from the modified Hummers' method were irradiated in a domestic microwave oven (GE, JES0736SM1SS) operated at 1100 W for 1 minute. During the irradiation, a large volume expansion of the GO powder occurred and the black, fluffy MEGO powder obtained was collected for activation. Typically, 400 mg MEGO powder was dispersed in 20 ml 7M aqueous KOH solution and stirred for 4 hours at a speed of 400 rpm, followed by another 20 hours of static soaking in ambient conditions.
  • the extra KOH solution was removed by briefly filtering the mixture through a polycarbonate membrane (Whatman, 0.2 /mi); then the mixture was dried in the lab environment at 65 °C for 24 hours.
  • a control MEGO sample made with the same soaking-drying process but with no KOH was also prepared, and 85% of the mass remained after drying.
  • a KOH to MEGO ratio was calculated by assuming the MEGO in the dry MEGO/KOH mixture gave the same mass yield, i.e.,85%.
  • KOH uptake was linearly dependent on the molarity of the KOH solution, with other process parameters held constant (such as the amount of MEGO from the same batch of GO and the volume of KOH solution).
  • the KOH/MEGO ratio was 8.9 ⁇ 0.3.
  • the dry MEGO/KOH mixture was heated at 800 °C for 1 hour in a horizontal tube furnace (50-mm diameter), with an argon flow of 150 seem and working pressure of ⁇ 400 Torr. The temperature was ramped from room temperature to 800 °C at 5 °C/min.
  • the sample was repeatedly washed by de-ionized water until a pH value of 7 was reached. Then the sample was dried at 65 °C in ambient for 2 hours, followed by thermal annealing at 800 °C in vacuum (0.1 Torr) for 2 hours, to generate 'activated MEGO' (a-MEGO) powders.
  • Thermally exfoliated graphite oxide ('TEGO') made by 'thermal shocking' of GO at 250 °C in ambient, was activated following the same process.
  • the a-MEGO and a-TEGO so obtained were characterized in a variety of ways, and supercapacitor measurements were made, as described in the main text and below.
  • the a-MEGO was analyzed by scanning electron microscopy (SEM, Hitachi S5500, 30 kV), transmission electron microscopy (TEM, JEOL 201 OF, 200 kV at UT- Austin; TEM, spherical aberration corrected FEI Titan 80/300, 80 kV at BNL; the spherical and chromatic aberration corrected TEAM instrument at LBNL, see: ncem.lbl.gov/TEAMproject/) and scanning TEM (Aberration corrected Hitachi HD2700C at BNL).
  • the exit wave reconstructed image shown in FIG. F was processed using the MacTempas Exit Wave Reconstruction Package (totahesolution.com) from a series of 41 images, ranging from 28 nm above
  • Gaussian to 28 nm below Gaussian and with 1.4 nm focal step size Gaussian to 28 nm below Gaussian and with 1.4 nm focal step size.
  • Quantachrome Nova 2000 at 77.4 K to obtain the surface areas of a-MEGO samples from different KOH/MEGO ratios, and for the comparison between MEGO control and a-MEGO samples.
  • Detailed adsorption experiments with nitrogen (77.4K), argon (87.3 K), and carbon dioxide (273.2 K) were also performed with a Quantachrome Autosorb iQ MP in order to assess surface area and pore characteristics of the a-MEGO.
  • Nitrogen adsorption with the Quantachrome Autosorb iQ MP was also carried out on the a-TEGO. The samples were outgassed at 150 °C for 16 hours under turbomolecular vacuum pumping prior to the gas adsorption measurements.
  • Micro Raman was performed on a Witec Alpha 300 confocal Raman system with a laser wavelength of 532 nm. Lorentzian fitting was done to obtain the positions and widths of the D and G bands in the Raman shift spectra. Fourier transform infrared spectroscopy (FTIR) was done with a Perkin Elmer Spectrum BX.
  • FTIR Fourier transform infrared spectroscopy
  • X-ray photoelectron spectroscopy was performed with two separate systems equipped with monochromatic Al Ka sources (Kratos AXIS Ultra DLD, Omicron Nanotechnology XM1000/EA 125 U7) to analyze the chemical composition of the samples.
  • EPR Electron paramagnetic resonance
  • Electron energy loss spectroscopy (EELS, Gatan) was carried out in a JEOL 2010 TEM on commercial graphite powder (SP-1 graphite, Bay Carbon, Inc. Michigan, USA; the same graphite used to make the GO that was converted to MEGO), MEGO, and a-MEGO samples, respectively.
  • High resolution SEM, STEM and EELS were performed using a dedicated STEM Hitachi HD2700C, equipped with a cold-field emission gun, a CEOS aberration corrector and a high-resolution (0.35eV) EELS Spectrometer (Gatan, Syndica).
  • Iu and Ig represent the integrated intensity for specific energy ranges of the spectra for the a-MEGO and graphite (assumed to be 100% sp carbon), respectively. Comparisons were made between a-MEGO and graphite films of approximately the same thickness (as measured by comparing the intensity in the zero loss peak with the intensity in the low-loss region). Iir * and ⁇ * are the peak intensities due to the ls ⁇ it* and ls ⁇ ⁇ * transitions, corresponding to sp 2 and sp 3 hybridized carbon atoms.
  • the powder sample was supported on a surface that was nearly free of carbon and oxygen and that consisted of a Pt thin film that had been evaporated on a Si wafer.
  • XPS data was analyzed using the Casa XPS fitting package and an asymmetric Doniach-Sunjic (DS) peak shape was used to fit the sp 2 component, as required for conductive sp 2 carbon materials.
  • a two-electrode cell configuration was used to measure the performance of supercapacitors with the a-MEGO and a-TEGO materials. 5 wt% Polytetrafluoroethylene (PTFE; 60 wt% dispersion in water) was added to the a-MEGO and a-TEGO as a binder.
  • PTFE Polytetrafluoroethylene
  • the a-MEGO (or a-TEGO) and PTFE was mixed into a paste using a mortar and pestle, rolled into uniform thickness sheets whose thickness ranged 40 to 50 ⁇ thick (from sheet to sheet) and punched into ⁇ l-cm diameter electrodes.
  • a pair of typical electrodes had a weight between 2.5 and 4.0 mg after drying overnight at a ⁇ 100 °C under vacuum.
  • the two identical (by weight and size) electrodes were assembled in a test cell, which consisted of two current collectors, two electrodes, and an ion-porous separator (Celgard® 3501) supported in a test fixture consisting of two stainless steel plates.
  • l-butyl-3-methylimidazolium tetrafluoroborate ( ⁇ BF 4 ) was obtained commercially from Sigma Aldrich and diluted in acetonitrile (AN) with a weight ratio of 1 :1 (with some testing done with neat BMIM BF 4 ).
  • the tetraethylammonium tetrafluoroborate (TEA BF , Sigma Aldrich) was prepared at 1.0 M in AN.
  • the l-Ethyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI, Sigma Aldrich) was used as purchased.
  • RESR Vdrop /(2Icons). The power density, calculated from the discharge data at certain constant current Icons, and normalized with the weight of the carbon cell (two carbon electrodes) is given by
  • FIG. 4 illustrates EPR data of a-MEGO with DPPH used as a standard.
  • FIG. 6 illustrates detailed XPS analysis of a-MEGO sample (SSA ⁇ 2520 m2/g).
  • A Fit to the Cls region is shown, with detailed spectrum inset.
  • An sp 3 component if present, is expected at +0.8 to +0.9 eV above the sp 2 component in the C Is spectrum.
  • shake-up features are also present at +4.4, +5.5, +6.5 and +7.9 eV above the main sp 2 peak (widths of 1.5, 1.3, 1.3 and 1.1 eV respectively) and are in good agreement with fits to the extended shake-up energy loss spectrum of glassy carbon and highly oriented pyrolytic graphite (HOPG) by Leiro et. al.
  • HOPG highly oriented pyrolytic graphite
  • Residual potassium ( ⁇ 2 at. %) from the KOH activation process is detected as a K 2p doublet with the K 2p 3 2 state observed at 292.9 eV.
  • B The O Is region is shown and composed of three components at 530.6 eV (K2C03), 532.5 eV (KHC03) and 534.6 eV (KOH). It is noted that the C Is shake up features described above make the unequivocal deconvolution of a carbonate bond problematic. Residual peak fitting error is shown beneath all spectra.
  • FIG. 7 illustrates (A) Raman of a-MEGO and MEGO control sample. The Id/Ig slightly increases from -1.16 in MEGO to ⁇ 1.19 in a-MEGO. From Lorentzian fitting, the D band FWHM increases from -135 to -183 cm-1. (B) FTIR transmittance spectra.
  • FIG. 9 illustrates N 2 adsorption/desorption analysis of a-MEGO ( ⁇ 2,520 m 2 /g) with MEGO as control.
  • A N 2 isotherm curves at 77.4 K.
  • B Cumulative pore volume versus pore diameter plots obtained from the adsorption isotherm in (A). NLDFT analysis for carbon with slit/cylindrical model was used on the adsorption data to obtain the pore volumes.
  • FIG. 10 Quenched solid density functional theory' (QSDFT) pore size distribution of a-MEGO.
  • QSDFT Quenched solid density functional theory'
  • FIG. 12 Supercapacitor performance of a-MEGO (SSA - 3,100 m 2 /g) with 1.0 M TEA BF AN electrolyte.
  • A CV curves for different scan rates. Rectangular shapes indicate the capacitive behavior.
  • B Galvanostatic charge/discharge curves of a-MEGO based supercapacitor under different constant currents. The specific capacitances calculated from the discharge curves are 154, 145 and 141 F/g, for the constant currents of 0.8, 1.9 and 3.8 A/g, respectively.
  • FIG. 13 illustrates testing of the a-MEGO (with surface area of- 3,100 m 2 /g) based supercapacitor in neat ⁇ BF 4 over 10000 cycles. Constant current cycles were run at a rate of 2.5 A/g. Retention of 97% was obtained after 10000 cycles. In this example, the pure IL was used as electrolyte to minimize possible contamination.
  • FIG. 14 illustates supercapacitor performance of a-MEGO (SSA ⁇ 3,100 m 2 /g) in neat EMIM TFSI electrolyte.
  • A CV curves under different scan rates.
  • B Galvanostatic charge/discharge curves under different constant currents.
  • the specific capacitances calculated from the discharge curves with maximum voltage of 3.5 V are 200, 192 and 187 F/g for the currents of 0.7, 1.8 and 3.5 A/g, respectively.
  • the normalized ESR is
  • FIG. 15 illustrates N 2 adsorption/desorption analysis of a-TEGO.
  • A High resolution, low pressure isotherm, from which a high BET SSA of 2,675 m /g (calculated in the linear relative pressure range from 0.1 to 0.3) is obtained.
  • B Pore size distribution for N 2 adsorption (calculated using a slit/cylindrical NLDFT model). 15. Supercapacitor performance of a-TEGO with BMIM BF 4 /AN electrolyte
  • FIG. 16 illustrates supercapacitor performance of a-TEGO (SSA -2,700 m 2 /g) in the BM BF 4 /AN electrolyte.
  • A CV curves for different scan rates.
  • B Galvanostatic charge/discharge curves under different constant currents. The capacitance values calculated are 156, 154 and 154 F/g for the currents of 2.0, 3.9 and 7.8 A/g, respectively.

Abstract

La présente invention porte sur un matériau carboné qui peut être utile, par exemple, dans les ultracondensateurs. Elle porte également sur des applications et des dispositifs contenant ce matériau carboné.
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RU2525825C1 (ru) * 2012-11-02 2014-08-20 Владимир Владимирович Слепцов Пленочный конденсатор
CN103833015A (zh) * 2012-11-23 2014-06-04 海洋王照明科技股份有限公司 石墨烯及其制备方法
CN103833010A (zh) * 2012-11-23 2014-06-04 海洋王照明科技股份有限公司 石墨烯及其制备方法和应用
CN103833018A (zh) * 2012-11-23 2014-06-04 海洋王照明科技股份有限公司 石墨烯及其制备方法
CN103833013A (zh) * 2012-11-23 2014-06-04 海洋王照明科技股份有限公司 石墨烯及其制备方法
EP2933229A1 (fr) * 2014-04-17 2015-10-21 Basf Se Dispositifs de condensateur électrochimique utilisant un matériau de carbone bidimensionnel pour filtrage de ligne à courant alternatif haute fréquence
WO2015158703A1 (fr) * 2014-04-17 2015-10-22 Basf Se Dispositifs condensateurs électrochimiques utilisant un matériau de carbone bidimensionnel pour le filtrage de ligne ca haute fréquence
CN105923632A (zh) * 2016-04-18 2016-09-07 方大炭素新材料科技股份有限公司 一种基于石墨烯复合改性超级电容器用活性炭的制备方法
CN107017096A (zh) * 2017-04-01 2017-08-04 苏州海凌达电子科技有限公司 一种改性石墨电极材料的制备方法及其应用
CN107093526A (zh) * 2017-04-14 2017-08-25 苏州海凌达电子科技有限公司 以石墨氧化物为主要成分的电极材料制备方法及其应用
CN107093526B (zh) * 2017-04-14 2019-08-02 苏州海凌达电子科技有限公司 以石墨氧化物为主要成分的电极材料制备方法及其应用
CN111925207A (zh) * 2020-07-08 2020-11-13 杭州电子科技大学 一种Mg3B2O6-Ba3(VO4)2复合陶瓷材料及制备方法
CN111925207B (zh) * 2020-07-08 2022-06-07 杭州电子科技大学 一种Mg3B2O6-Ba3(VO4)2复合陶瓷材料及制备方法

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