WO2018104942A1 - Supercondensateur comprenant une électrode de charbon de faible pureté et électrolyte aqueux - Google Patents

Supercondensateur comprenant une électrode de charbon de faible pureté et électrolyte aqueux Download PDF

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Publication number
WO2018104942A1
WO2018104942A1 PCT/IL2017/051321 IL2017051321W WO2018104942A1 WO 2018104942 A1 WO2018104942 A1 WO 2018104942A1 IL 2017051321 W IL2017051321 W IL 2017051321W WO 2018104942 A1 WO2018104942 A1 WO 2018104942A1
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Prior art keywords
electrode
supercapacitor
activated carbon
alkaline electrolyte
porous
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PCT/IL2017/051321
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English (en)
Inventor
Ervin TAL-GUTELMACHER
Mordechay Moshkovich
Tamir Stein
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POCell Tech Ltd.
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Publication of WO2018104942A1 publication Critical patent/WO2018104942A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/34—Carbon-based characterised by carbonisation or activation of carbon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H01G11/10—Multiple hybrid or EDL capacitors, e.g. arrays or modules
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H01G11/30—Electrodes characterised by their material
    • H01G11/46—Metal oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H01G11/54—Electrolytes
    • H01G11/58—Liquid electrolytes
    • H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • H01G11/52—Separators
    • 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 invention is directed to a supercapacitor comprising a carbonaceous electrode utilizing a low purity carbon source in combination with alkaline electrolyte, and methods for the preparation thereof.
  • Electrochemical capacitors or an electric double-layer capacitor (EDLC), also termed supercapacitors or ultracapacitors, are one class of energy-storage devices that fill the gap between the high specific energy of batteries and the high specific power of conventional electrostatic capacitors.
  • a basic EDLC cell configuration is a pair of highly porous electrodes, typically including activated carbon, disposed on opposite faces of parallel conductive plates known as current collectors.
  • the electrodes are impregnated with an electrolyte, and separated by a separator consisting of a porous electrically-insulating and ion-permeable membrane.
  • a voltage is applied between the electrodes, negative ions from the electrolyte flow to the positive electrode while positive ions from the electrolyte flow to the negative electrode, such that an electric double layer is formed at each electrode/electrolyte interface by the accumulated ionic charges.
  • energy is stored by the separation of positive and negative charges at each interface.
  • the separator prevents electrical contact between the conductive electrodes but allows the exchange of ions.
  • the EDLC When the EDLC is discharged, such as by powering an external electrical device, the voltage across the electrodes results in current flow as the ions discharge from the electrode surfaces.
  • the EDLC may be recharged and discharged again over multiple charge cycles.
  • EDLC While the amount of energy stored per unit weight is generally lower in an EDLC in comparison to electrochemical batteries, the EDLC has a much greater power density and a high charge/discharge rate. Furthermore, an EDLC has a far longer lifespan than a battery and can undergo many more charge cycles with little degradation (millions of charge cycles, compared to hundreds for common rechargeable batteries). Consequently, EDLCs are ideal for applications that require frequent and rapid power delivery, such as hybrid vehicles that are constantly braking and accelerating. EDLCs are also environmentally friendly (have a long lifespan and are recyclable), safe, lightweight, and have a very low internal resistance (ESR). The charging process of an EDLC is also relatively simple and is not subject to overcharging.
  • the most widely available commercial supercapacitor is an electric double-layer capacitor based on a symmetric configuration of two high-surface-area carbon electrodes separated by an electrolyte. Charge is stored in the electric double-layer that arises at all electrode/electrolyte interfaces, resulting in effective capacitances of 10-40 ⁇ '2 (for flat plates). On charge the anions are adsorbed on one electrode and the cations on the other electrode.
  • Aqueous-based activated carbon supercapacitors are promising devices for providing high power densities, since water is a low-cost and non-toxic material, aqueous electrolytes do not require specific manufacturing conditions, and possess relatively high conductivity.
  • energy density of aqueous electrolyte supercapacitors is relatively low due to the limited cell voltage.
  • An efficient way to improve the cell voltage in terms of the energy density is to use organic electrolytes with a wider electrochemical stability window than water.
  • Organic electrolytes including the combination of a solvent with different salts could enable the maximum cell voltage to reach more than 3 V, a value three times higher than the maximum cell voltage of aqueous-based supercapacitors.
  • various carbon materials are used as active materials for EDLC electrodes, owing to their high conductivity, high surface area, a rich variety of dimensionality, good corrosion resistance, controlled pore structure, processability and compatibility in composites, and relatively low cost.
  • the non-limiting examples of carbonaceous materials include activated carbons (ACs), carbon nanotubes, graphite, graphene, and carbide-derived carbons. Considering the essential criteria of low cost and high volumetric capacitance required by industrial applications, activated carbon remains the material of choice for EDLCs.
  • AC material used for the preparation of carbon-based electrodes often requires several purification stages prior the electrode processing step in order to achieve high power densities. These additional purification stages are economically inefficient and contribute to the overall costs of the electrode starting materials.
  • Commercially available activated carbons which are designated for use in supercapacitors are typically of ultra-purity grades in order to minimize poisoning of the electrolyte and ensure high durability and cycle life. Purity of the carbon source is particularly important in aqueous supercapacitors, which do not include water-, acid- and/or alkaline-soluble materials, such as, for example, metals.
  • AC -based electrodes often require the use of stabilizing reagents such as binders, silicates or gelling agents which are incorporated into AC during the electrode preparation. Incorporation of said stabilizing reagents can influence electrochemical capacitance, add additional steps to the electrode manufacturing process and increase the overall costs thereof. Additionally, AC-based electrodes, which include stabilizing reagents are prone to mechanical degradation and thus have a shorter cycle life.
  • stabilizing reagents such as binders, silicates or gelling agents which are incorporated into AC during the electrode preparation. Incorporation of said stabilizing reagents can influence electrochemical capacitance, add additional steps to the electrode manufacturing process and increase the overall costs thereof.
  • AC-based electrodes, which include stabilizing reagents are prone to mechanical degradation and thus have a shorter cycle life.
  • the present invention provides a unique electrode composition utilizing a low purity carbon source in combination with alkaline electrolyte, demonstrating improved energetic efficiency, capacitance and wide temperature range stability.
  • the beneficial electrode composition of the invention utilizes low purity carbon source as the main component, thus promoting the use of environmentally friendly and economically efficient starting materials.
  • the electrode of the present invention is mechanically, chemically and thermally-stable, and demonstrates an advantageous stability in the sub-zero temperatures.
  • the electrode according to the principles of the invention can be substantially free of commonly used binder agents, gelling agents and other thickening agents and has no hazardous effect on humans or the surrounding environment.
  • the inventors of the present invention have surprisingly found that a low purity carbon comprising above about 7% ash can beneficially be used to prepare a supercapacitor electrode, which provides high energetic efficiency and cost-efficient capacitance. Furthermore, when used in combination with an alkaline electrolyte, the low purity carbon-based electrode showed diminished leakage currents, as compared to the use with an acidic electrolyte, wherein said leakage currents are acceptable for commercial use.
  • the unique electrode composition of the invention therefore allows the production of cost-effective alkaline supercapacitor with a prolonged cycle life. Performance of the supercapacitor comprising low purity carbon-based electrodes can be further increased by adjusting the electrode thickness and selecting suitable separator material .
  • the present invention further provides preparation methods of the electrode, enabling both small and large scale production possibilities, which can be tailored to the desired supercapacitor application.
  • the present invention provides a supercapacitor comprising at least one capacitor cell comprising a first porous electrode, a second porous electrode, an aqueous alkaline electrolyte being in contact with said first porous and second porous electrodes, and a separator separating the first porous electrode from the second porous electrode, wherein the first porous electrode comprises low purity activated carbon having an ash content of above about 7 wt%, and wherein the first porous electrode is impregnated with an aqueous alkaline electrolyte.
  • the activated carbon has an ash content of above about
  • the activated carbon has an ash content of above about 15 wt%.
  • the activated carbon as described above has a surface area of at least about 500 m 2 /gr. In some other embodiments, the activated carbon has a surface area of at least about 1000 m 2 /gr. In some additional embodiments, the activated carbon as described above has a porosity/pore volume of about 0.3 to about 0.9 cc/gr.
  • the aqueous alkaline electrolyte comprises a dissolved salt selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH) and lithium oxide (LiOH). Each possibility represents a separate embodiment of the invention.
  • the electrolyte comprises KOH.
  • the aqueous alkaline electrolyte concentration is between about 20 and about 50 wt%. In some currently preferred embodiments, the aqueous alkaline electrolyte concentration is about 30 wt%.
  • the first electrode as described above is a binder-free electrode. In some related embodiments, the first electrode is substantially free of gelling agents and/or thickening agents.
  • the activated carbon is present in the first porous electrode in a weight percent ranging from about 35 to about 45 wt% of the total weight of the first electrode.
  • the alkaline electrolyte is present in the first porous electrode in a weight percent ranging from about 55 to about 65 wt% of the total weight of the first electrode.
  • the first porous electrode comprises a dry matter content (DMC) from about 35 to about 45 wt% activated carbon and an alkaline electrolyte in an amount of about 55 to about 65 wt%.
  • DMC dry matter content
  • the first electrode consists essentially of the activated carbon and aqueous alkaline electrolyte.
  • said aqueous alkaline electrolyte comprises KOH.
  • the first porous electrode as described above has a thickness ranging from about 50 microns to about 5 millimeters. In further embodiments, the first porous electrode has a thickness ranging from about 50 microns to about 350 microns. In additional embodiments, the first porous electrode has a thickness ranging from about 300 microns to about 1.5 millimeters.
  • the specific capacitance of the first porous electrode is at least about 45 F/g.
  • the first porous electrode has a porosity of about 0.3 to about 0.9 cc/gr.
  • the separator comprises a material selected from the group consisting of polyvinyl alcohol, polypropylene, polyethylene and combinations thereof. In further embodiments, the separator is selected from a polyvinyl alcohol-coated polyethylene separator and a polypropylene separator. Each possibility represents a separate embodiment of the invention.
  • the separator comprises polyvinyl alcohol. In some specific embodiments, the supercapacitor is a polyvinyl alcohol coated polyethylene separator. In certain embodiments, the separator has a thickness of above about 30 micron.
  • the supercapacitor of the invention is a symmetric supercapacitor, wherein the second electrode is substantially identical to the first electrode.
  • the second electrode comprises low purity activated carbon having an ash content of above about 7 wt%, and is impregnated with aqueous alkaline electrolyte.
  • the supercapacitor of the invention is an asymmetric supercapacitor.
  • the second electrode comprises low purity activated carbon having an ash content of above about 7 wt%, and is impregnated with aqueous alkaline electrolyte, wherein the weight percent of activated carbon and/or the thickness of the second electrode are different than those of the first electrode.
  • the second electrode comprises a transition metal oxide or sulfide.
  • the transition metal oxide or sulfide is selected from the group consisting of Mn n O x , TiO x , NiO x , CoO x , SnO x , FeSy, MoS y , NiS y , CoS y , MnS y , TiS y , SnS y and combinations thereof, wherein x ranges from 1.5 to 3, y ranges from 1.8 to 2.2 and n ranges from 1 to 2.
  • the second electrode comprises Mn0 2 .
  • the second electrode can further include activated carbon.
  • said activated carbon is a low purity carbon comprising above about 7 wt% ash.
  • the second electrode comprises an additional carbonaceous material.
  • the second electrode comprises activated carbon, Mn0 2 , carbon nanotubes (CNTs), and graphite.
  • the present invention provides a method for preparing a supercapacitor porous electrode comprising a low purity activated carbon having an ash content of above about 7 wt%, wherein the electrode is impregnated with an aqueous alkaline electrolyte, the method comprising the steps of: (a) mixing the aqueous alkaline electrolyte with the low purity activated carbon, with optional stirring, to achieve a homogeneous paste; (b) heating the paste obtained in step (a); and (c) processing the paste obtained in step (b) to form a standalone homogeneous electrode.
  • the activated carbon has an ash content of above about 10 wt%. In further embodiments, the activated carbon has an ash content of above 15 wt%.
  • the activated carbon has a surface area of at least about 500 m 2 /gr. In yet some other embodiments, the activated carbon has a surface area of at least about 1000 m 2 /gr.
  • the aqueous alkaline electrolyte comprises a dissolved salt selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH) and lithium oxide (LiOH). Each possibility represents a separate embodiment of the invention. In some currently preferred embodiments, the electrolyte comprises KOH.
  • the mixing in step (a) is carried out in a stepwise manner.
  • the heating in step (b) is carried out at a temperature of about 50 to about 100 °C.
  • the mixing in step (a) is carried out utilizing a mixing apparatus selected from a mixer, a hand mixer, a homogenizer or a sonicator. Each possibility represents a separate embodiment of the invention.
  • the mixing in step (a) is carried out utilizing a mixer.
  • the mixing is performed at a speed of from about 20 to about 120 RPM. In some other embodiments, the mixing speed is increased throughout step (a).
  • the weight ratio of activated carbon and the alkaline electrolyte in step (a) ranges from about 35 to about 45 wt% activated carbon and from about 55 to about 65 wt% electrolyte.
  • the processing of step (c) is carried out utilizing a method selected from rolling, calendering, coating, casting, pressing, printing, 3D printing or a combination thereof.
  • the processing of step (c) is carried out utilizing rolling.
  • the rolling as described above is performed on an inert polymeric laminate.
  • the laminate is peeled off after the rolling process, thereby allowing the formation of a free-standing electrode.
  • the processing of step (c) further comprises pressing.
  • the paste is pressed between two non-conducting polymer sheets.
  • the present invention further provides a method for the preparation of the supercapacitor as described above, comprising preparing the first supercapacitor electrode comprising (a) mixing aqueous alkaline electrolyte with low purity activated carbon having an ash content of above about 7 wt%, with optional stirring, to achieve a homogeneous paste; (b) heating the paste obtained in step (a); and (c) processing the paste obtained in step (b) to form a standalone homogeneous electrode.
  • the method comprises preparing a second porous electrode; separating the first porous electrode from the second porous electrode by a porous separator.
  • the method comprises filling the separator with the electrolyte, wherein the electrolyte is in contact with the first porous electrode and with the second porous electrode.
  • Figure 1 depicts the specific capacitance of the alkaline and acidic sup ercapaci tors comprising low purity carbon- and high purity carbon-based electrodes (solid black bars - low purity carbon and acidic electrolyte, diagonal stripes bars - low purity carbon and alkaline electrolyte, solid grey bars - high purity carbon and acidic electrolyte, and checkerboard bars - high purity carbon and alkaline electrolyte).
  • Figure 2 depicts the energetic efficiency of the alkaline and acidic supercapacitors comprising low purity carbon- and high purity carbon-based electrodes.
  • Figure 3 depicts the leakage current of the alkaline and acidic supercapacitors comprising two distinct low purity carbon-based electrodes (anodes).
  • Figure 4 depicts the electrode capacitance cost-efficiency as a function of carbon ash content.
  • FIG. 5 depicts the Equivalent Series Resistance (ESR) values measured for different electrode thicknesses in both symmetric and asymmetric supercapacitor configurations.
  • Figure 6 depicts the capacitance measured for symmetric supercapacitor configuration comprising varied electrode thicknesses.
  • Figure 7 depicts the capacitance measured for asymmetric supercapacitor configuration comprising varied electrode thicknesses.
  • Figure 8 depicts the ESR values measured at room temperature for different supercapacitors as a function of the separator used in each system. The corresponding thickness of each separator is indicated as a white circle. Grey squares represent ESR DC measured at 0.1 Amp; white squares represent ESR DC measured at 1 Amp; and black squares represent ESR AC.
  • Figure 9 depicts the ESR values measured at -30°C for different supercapacitors as a function of the separator used in each system. The corresponding thickness of each separator is indicated as a white circle. Grey squares represent ESR DC measured at 0.1 Amp; white squares represent ESR DC measured at 1 Amp; and black squares represent ESR AC.
  • Figures lOA-lOC depict the ESR values measured over a wide temperature range for three distinct sup ercapaci tors utilizing different separators, namely, separators No: 1 ( ⁇ ), 2 ( ⁇ ) and 8 (-).
  • Figure 10A depicts the ESR DC measured at O. lAmp;
  • Figure 10B depicts the ESR DC measured at 1 Amp; and
  • Figure IOC depicts the ESR AC .
  • Figure 11A depicts the ESR values measured at 65 °C for three distinct supercapacitors utilizing different separators, namely, separators No: 1 ( ⁇ ), 5 ( ⁇ ) and 8(-), over the course of the charge/discharge experiment.
  • Figure 11B depicts the capacitance measured at 65 °C for three distinct supercapacitors utilizing different separators, namely, separators No: 1 ( ⁇ ), 5 ( ⁇ ) and 8(-), over the course of the charge/discharge experiment.
  • the present invention is directed to a unique electrode composition based on the beneficial combination of a low purity carbon source with an alkaline electrolyte, giving rise to a mechanically, chemically and thermally-stable free-standing electrode.
  • a low purity carbon source is both cost-effective and environmentally friendly, as the electrode preparation does not require purifying steps and as such does not impose any hazardous effect on humans or the surrounding environment.
  • the low-purity carbon source is an activated carbon, having a high surface area which promotes high capacitance of the supercapacitor of the invention.
  • the electrode according to some embodiments of the invention can be substantially free of commonly used binder agents, gelling agents and other thickening agents, allowing improved electrochemical performance without jeopardizing the overall mechanical stability of the electrode, thereupon enabling prolonged cycle life.
  • the present invention provides a supercapacitor comprising at least one capacitor cell comprising a first porous electrode, a second porous electrode, an aqueous alkaline electrolyte being in contact with said first porous and second porous electrodes, and a separator separating the first porous electrode from the second porous electrode, wherein the first porous electrode comprises a low purity activated carbon having an ash content of above about 5 wt%, and wherein the first porous electrode is impregnated with an aqueous alkaline electrolyte.
  • the activated carbon has an ash content of above about 7 wt%.
  • low purity activated carbon refers in some embodiments to the ash content of above about 5 wt%. In further embodiments, the term “low purity activated carbon”, refers to the ash content of above about 6 wt%. In some currently preferred embodiments, the term “low purity activated carbon” refers to the ash content of above about 7 wt%.
  • the ash weight percent refers to the weight of ash relatively to the total weight of the activated carbon utilized in the electrode.
  • the activated carbon has an ash content of above about 8 wt%. In further embodiments, the activated carbon has an ash content of above about 9 wt%. In still further embodiments, the activated carbon has an ash content of above about 10 wt%. In yet further embodiments, the activated carbon has an ash content of above about 11 wt%. In still further embodiments, the activated carbon has an ash content of above about 12 wt%. In yet further embodiments, the activated carbon has an ash content of above about 13 wt%. In still further embodiments, the activated carbon has an ash content of above about 14 wt%. In yet further embodiments, the activated carbon has an ash content of above 15 wt%.
  • the activated carbon does not contain an ash content of above 20 wt%. Without being bound by theory or mechanism of action, it is postulated that activated carbon having above 20 wt% ash will be more prone to go through parasitic reactions, which in turn might cause an increase in the internal resistance and leakage current of the supercapacitor comprising said impure activated carbon, and decrease the overall performance of the supercapacitor.
  • the activated carbon utilized in the first porous electrode is characterized in that the ash content is below about 20 wt%. In further embodiments, the ash content is below about 19 wt%, below about 18 wt%, below about 17 wt%, below about 16 wt%, or below about 15 wt%. Each possibility represents a separate embodiment of the invention.
  • the activated carbon has an ash content ranging from about 7 wt% to about 20 wt%. In certain embodiments, the activated carbon has an ash content ranging from about 7 wt% to about 15 wt%. In further embodiments, the activated carbon has an ash content ranging from about 8 wt% to about 12 wt%. In additional embodiments, the activated carbon has an ash content ranging from about 15 wt% to about 20 wt%. In additional embodiments, the activated carbon has an ash content ranging from about 16 wt% to about 19 wt%. In some particular embodiments, the activated carbon has an ash content of about 10 wt%.
  • the activated carbon has an ash content of about 18 wt%.
  • ash refers in some embodiments to the impurities found in activated carbon.
  • Said impurities can include inorganic impurities e.g. metals, metal oxides, metal phosphates, metal sulphates, and ceramic materials (i.e. silicates).
  • Non-limiting examples of said impurities include calcium carbonate, potash, phosphate, iron, manganese, sodium, aluminum, strontium, zinc, and copper.
  • the acid/water-soluble ash content constitutes at least about 1 wt% of the total weight of ash in the carbon source and/or electrode.
  • the acid/water-soluble ash content constitutes at least about 2.5 wt% of the total weight of ash. In further embodiments, the acid/water-soluble ash content constitutes at least about 5 wt% of the total weight of ash.
  • the ash content of the activated carbon present in the electrode can be assessed as known in the art, for example, by Inductively coupled plasma mass spectrometry (ICP-MS) or Inductively coupled plasma Atomic Emission Spectroscopy (ICP-AES). Ash content of commercially available carbons is typically assessed by burning the carbon at the temperature of above about 500°C and weighting the product of the combustion reaction. The difference in the weight of the initial carbon and the reaction product is defined as the ash content.
  • ICP-MS Inductively coupled plasma mass spectrometry
  • ICP-AES Inductively coupled plasma Atomic Emission Spectroscopy
  • porous refers to a structure of interconnected pores or voids such that continuous passages and pathways throughout a material are provided.
  • the porosity of the electrodes is from about 20% to about 90%, such as, for example, 30% - 80%, or 40% - 70% porosity. Each possibility represents a separate embodiment of the invention.
  • the porous electrodes have a high surface area.
  • the term "high surface area”, as used in some embodiments, refers to a surface area in the range from about 1 to about 2000 m 2 /g, such as, for example, 10 - 1000 m 2 /g or 50 -1500 m 2 /g.
  • the terms “porous” and/or “high surface area” encompass materials having micro or nanoparticles.
  • the activated carbon as described above has a surface area of at least about 500 m 2 /gr. In further embodiments, the activated carbon has a surface area of at least about 600 m 2 /gr. In still further embodiments, the activated carbon has a surface area of at least about 700 m 2 /gr. In yet further embodiments, the activated carbon has a surface area of at least about 800 m 2 /gr. In still further embodiments, the activated carbon has a surface area of at least about 900 m 2 /gr. In yet further embodiments, the activated carbon has a surface area of at least about 1000 m 2 /gr.
  • the activated carbon as described above has a porosity/pore volume of about 0.3 to about 0.9 cc/gr. In another embodiment, the porosity/pore volume is about 0.4 to about 0.8 cc/gr. In yet another embodiment, the porosity/pore volume is about 0.45 to about 0.75 cc/gr. Choice of electrolyte
  • the present invention is based in part on a surprising finding that the supercapacitor comprising a low-purity electrode comprising activated carbon having ash content of above about 7 wt% and an alkaline electrolyte had leakage current which was significantly lower than the one measured in a similar supercapacitor utilizing acidic electrolyte.
  • the low purity activated carbon is combined with an aqueous alkaline electrolyte.
  • the aqueous alkaline electrolyte comprises a dissolved salt selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH) and lithium oxide (LiOH).
  • KOH potassium hydroxide
  • NaOH sodium hydroxide
  • LiOH lithium oxide
  • the utilized electrolyte should be complimentary to the supercapacitor system in which it serves in. Studies showed a strong correlation between the electrode pore size and the electrolyte ion size. This correlation affects the conductivity of the electrode and addresses the need of tailoring the pore sizes to the ion size to promote optimum supercapacitor performance. Another important factor is the chemical interaction between the electrode material, i.e. active carbon, and the electrolyte.
  • the KOH electrolyte has a lower tendency to react with the carbon impurities, as well as typical surface functional groups existing in activated carbon, in comparison, for example, to acidic electrolytes.
  • the low reactivity of KOH prevents parasitic reactions, which in turn reduce the tendency for leakage current, self-discharge and energy/power loss of the supercapacitor device.
  • KOH electrolyte is more chemically ccoommppaattiibbllee wwiitthh tthhee ppaacckkaaggiinngg eeqquuiippmmeenntt aanndd mmaatteeririaallss ooff tthhee aasssseemmbblleedd ssuuppeerrccaappaacciittoorr ddeevviiccee aanndd pprreevveennttss ccoorrrroossiioonn ooff tthheessee mmaatteerriiaallss wwhhiicchh aarree iinn cclloossee pprrooxxiimmiittyy ttoo tthhee eelleeccttrroollyyttee soolluuttii
  • the first electrode as described above is a free-standing and mechanically stable electrode. Additionally, the electrode can be essentially free of commonly used additives such as binder reagents for enforcing mechanical stability of an electrode. Thus, in certain embodiments, the first electrode as described above is a binder-free electrode. In some related embodiments, the first electrode is substantially free of gelling agents and/or thickening agents.
  • the term "self-standing electrode” refers to an electrode that is made out of a paste comprising the low purity activated carbon and alkaline electrolyte as described above, wherein said paste can be easily processed to achieve a flat electrode configuration in a reproducible and cost-productive manner, without utilizing additional stabilizing reagents, such as binders, gelling agents, thickening agents, cross-linkers, silicates or combinations thereof.
  • a binder include carboxymethyl cellulose (CMC), rubbers, PVDF, Teflon, LiPAA.
  • the first porous electrode as described above is substantially free of gelling agents and/or thickening agents such as clay, sulfonates, saccharides and organosilicons.
  • the terms “substantially free of gelling agents and/or thickening agents” and “essentially free of gelling agents and/or thickening agents” are used interchangeably and mean that the amount of such agents is undetectable by conventional detection means (e.g., elemental analysis).
  • the term “essentially free of gelling agents and/or thickening agents” refers to the presence of less than 0.5 wt% of said agents in the first porous electrode. In some other embodiments, said term refers to the presence of less than 0.1 wt% of said agents of the total weight of the electrode. In further embodiments, said term refers to an amount of less than 0.05 wt% of said agents of the total weight of the electrode.
  • the low purity activated carbon is one of the main components in the electrode of the invention. Accordingly, in some embodiments, the activated carbon is present in the first porous electrode in a weight percent ranging from about 35 to about 45 wt% of the total weight of the first electrode.
  • the second main component is the alkaline electrolyte as described above. Thus, in some currently preferred embodiments, the alkaline electrolyte is present in the first porous electrode in a weight percent ranging from about 55 to about 65 wt% of the total weight of the first electrode.
  • the first porous electrode comprises a dry matter content (DMC) from about 35 to about 45 wt% activated carbon and an alkaline electrolyte in an amount of about 55 to about 65 wt%.
  • DMC dry matter content
  • the first electrode consists essentially of the low purity activated carbon having above about 7 wt% ash and aqueous alkaline electrolyte.
  • said aqueous alkaline electrolyte comprises KOH.
  • the first porous electrode has a porosity of about 0.3 to about 0.9 cc/gr. In another embodiment, the porosity/pore volume is about 0.4 to about 0.8 cc/gr. In yet another embodiment, the porosity/pore volume is about 0.45 to about 0.75 cc/g.
  • the free-standing electrode as described above is mechanically stable and can be handled in a reproducible and efficient manner.
  • the first porous electrode as described above has a thickness ranging from about 50 micron to about 5 millimeters. In certain embodiments, the first porous electrode has a thickness ranging from about 50 micron to about 350 micron. In further embodiments, the first porous electrode has a thickness ranging from about 100 micron to about 300 micron. In additional embodiments, the first porous electrode has a thickness ranging from about 300 micron to about 1.5 millimeters. In further embodiments, the first porous electrode has a thickness ranging from about 500 micron to about 1 millimeter.
  • the supercapacitor of the invention includes a porous electrode as described above, which further comprises a conductive material selected from the group consisting of carbon nanotubes (CNTs), graphite, graphene and paracrystalline carbon.
  • CNTs carbon nanotubes
  • the supercapacitor of the invention includes a porous electrode as described above, which further comprises a conductive material selected from the group consisting of carbon nanotubes (CNTs), graphite, graphene and paracrystalline carbon.
  • the electrode of the invention demonstrates an improved overall performance at a wide range of temperatures.
  • the specific capacitance of the first porous electrode is at least about 45 F/g.
  • the supercapacitor as described above demonstrates an improved stability and capacitive properties at subzero temperatures. Without wishing to being bound by theory or mechanism of action, it is contemplated that the performance as subzero temperatures is affected by the separator composition and the specific combination of the unique composition of the electrode and separator.
  • the separator comprises an inert, electrically-insulating and ion-permeable material. In some embodiments, the separator is porous.
  • the separator is an inert membrane, which is ion-permeable (i.e., allowing the exchange of ions therethrough) and electrically-insulating (i.e., preventing the transfer of electrons therethrough).
  • the separator may include multiple layers (e.g., a number of separate ion-permeable and electrically-insulating membranes arranged successively).
  • Non-limiting examples of separator materials suitable for use in the supercapacitor of the invention include polyvinyl alcohol, polypropylene, polyethylene and combinations thereof.
  • the separator is selected from a polyvinyl alcohol -coated polyethylene separator and a polypropylene separator. Each possibility represents a separate embodiment of the invention.
  • the separator comprises polyvinyl alcohol.
  • the separator has a core-shell structure in which the core in made of polyethylene and the shell is made of polyvinyl alcohol (i.e. polyvinyl alcohol coated polyethylene separator). It is further contemplated that the combination between the low purity activated carbon source and the polyvinyl alcohol-based separator in an alkaline media contributes to the low and stable equivalent series resistance (ESR) values provided by the supercapacitor of the invention.
  • ESR equivalent series resistance
  • the first porous electrode comprises the activated carbon applied to the separator.
  • the electrode comprises a backing layer, which may include a conductive support such as, but not limited to carbon paper, carbon felt, carbon - plastic conductive composites, thin metal, including nickel, stainless steel, matrix, sponge or felt. Each possibility represents a separate embodiment of the invention.
  • the thin metal support can have a thickness of about 0.05 to 5 mm. According to the principles of the invention, the low purity activated carbon in combination with alkaline electrolyte offers high energetic efficiency and capacitance, and relatively low leakage current of the supercapacitor comprising said electrode.
  • the supercapacitor of the invention may be a symmetric or an asymmetric supercapacitor, including at least one electrode as described above.
  • the supercapacitor of the invention is a symmetric supercapacitor.
  • the second electrode is substantially identical to the first electrode.
  • substantially identical refers to electrodes, having the same composition, wherein the weight percent of each of electrode's constituents varies between the electrodes by no more than 10%.
  • substantially identical refers to electrodes, having the same composition, wherein the weight and/or thickness of the electrodes differs by no more than 10%.
  • the second electrode comprises low purity activated carbon having an ash content of above about 5 wt%, and is impregnated with aqueous alkaline electrolyte. In still further embodiments, the second electrode comprises low purity activated carbon having an ash content of above about 7 wt%, and is impregnated with aqueous alkaline electrolyte. In yet further embodiments, the second electrode comprises low purity activated carbon having an ash content of above about 10 wt%, and is impregnated with aqueous alkaline electrolyte. In still further embodiments, the low purity activated carbon of the first electrode has above about 7 wt% ash.
  • the supercapacitor of the invention is an asymmetric supercapacitor.
  • the asymmetric electrodes configuration may increase the energy density stored in the supercapacitor.
  • the asymmetric supercapacitor of the invention has a first low-purity carbon based anodic electrode as described above and a second cathodic electrode comprising a distinct composition.
  • the term "distinct composition”, as used herein, refers in some embodiments to the presence or at least one additional constituent in the second electrode as compared to the first electrode or vice versa. In further embodiments, the term “distinct composition" refers to a difference in the weight percent of at least one of electrode's constituents which is above about 10%.
  • the weight ratio between the electrodes can range between about 1 : 1 to about 1 :5. In some embodiments, the weight ratio refers to the dry matter of the electrode (excluding the electrolyte). In further embodiments, the weight ratio refers to the total weight of the electrode (i.e., the electrode impregnated with the electrolyte).
  • the term "distinct composition” refers to the electrodes comprising the same constituents and/or essentially the same weight percent of said constituents, wherein a weight ratio between the electrodes ranges between about 1 : 1.1 to 1 :5. In some embodiments, the weight ratio refers to the dry matter of the electrode (excluding the electrolyte). In further embodiments, the weight ratio refers to the total weight of the electrode (i.e., the electrode impregnated with the electrolyte). In further embodiments, the term “distinct composition” refers to the electrodes comprising the same constituents and/or essentially the same weight percent of said constituents, wherein a thickness ratio between the electrodes ranges between about 1 : 1.1 to 1 :5.
  • the second electrode comprises low purity activated carbon having an ash content of above about 5 wt%, and is impregnated with aqueous alkaline electrolyte, wherein the weight of the second electrode is different than that of the first electrode.
  • the second electrode comprises low purity activated carbon having an ash content of above about 5 wt%, and is impregnated with aqueous alkaline electrolyte, wherein the weight percent of activated carbon of the second electrode is different than that of the first electrode.
  • the second electrode comprises low purity activated carbon having an ash content of above about 5 wt%, and is impregnated with aqueous alkaline electrolyte, wherein the thickness of the second electrode is different than that of the first electrode.
  • the low purity activated carbon of the second electrode has above about 7 wt% ash.
  • the low purity activated carbon of the second electrode has above about 10 wt% ash.
  • the low purity activated carbon of the second electrode has above about 15 wt% ash.
  • the low purity activated carbon of the first electrode has above about 7 wt% ash.
  • the second electrode comprises a transition metal oxide.
  • the transition metal oxide is selected from the group consisting of Mn n O x , TiO x , NiO x , CoO x , SnO x and combinations thereof, wherein x ranges from 1.5 to 3 and n ranges from 1 to 2. Each possibility represents a separate embodiment of the invention.
  • the second electrode comprises Mn0 2 .
  • the second electrode comprises a transition metal sulfide.
  • the transition metal sulfide is selected from the group consisting of FeS y , MoS y , NiS y , CoS y , MnS y , TiS y , SnS y and combinations thereof, wherein y ranges from 1.8 to 2.2. Each possibility represents a separate embodiment of the invention.
  • the second electrode further comprises activated carbon.
  • the activated carbon can be a high purity activated carbon or a low purity activated carbon. Each possibility represents a separate embodiment of the invention.
  • the second electrode comprises an additional carbonaceous material, such as, but not limited to, graphite, carbon nanotubes, and graphene..
  • the second electrode as described above comprises Mn0 2 , carbon nanotubes (CNTs), graphite and activated carbon.
  • the second electrode does not include a metal as an active ingredient.
  • the super capacitor further comprises one or more current collectors.
  • the current collector is made from a conductive material, such as a conductive polymer material, in which the electrical conductivity is anisotropic, such that the conductivity perpendicular to the surface of the current collector sheet is greater than the conductivity along the surface.
  • the current collector can be made from a metal or other material which is inert to the chosen electrolyte as described above.
  • the present invention further provides a method for the preparation of the low purity activated-carbon-based electrode as described hereinabove.
  • Such electrode composition and preparation methodology is both economically and environmentally friendly, and gives rise to a straightforward and reproducible production of the beneficial electrode of the invention.
  • the present invention provides a method for preparing a supercapacitor electrode comprising a low purity activated carbon having an ash content of above about 5 wt%, wherein the electrode is impregnated with an aqueous alkaline electrolyte, the method comprising the steps of: (a) mixing the aqueous alkaline electrolyte with the low purity activated carbon, with optional stirring, to achieve a homogeneous paste; (b) heating the paste obtained in step (a); and (c) processing the paste obtained in step (b) to form a standalone homogeneous electrode.
  • the low purity activated carbon has an ash content of above about 7 wt%. In some embodiments, the activated carbon has an ash content of above about 10 wt%. In further embodiments, the activated carbon has an ash content of above about 15 wt%.
  • the aqueous alkaline electrolyte comprises a dissolved salt selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH) and lithium oxide (LiOH). Each possibility represents a separate embodiment of the invention. In some currently preferred embodiments, the electrolyte comprises KOH.
  • the present invention is based in part on the unexpected results demonstrating an improved absorption of the electrolyte solution into the activated carbon material upon heating the mixture obtained in step (a).
  • the heating process can be also considered as a degassing process, as the heating assists in the removal of unwanted gases which are physically adsorbed onto the carbon source. Additionally the removal of the unwanted gases releases pressure from the system and reduces the occurrence of abruption of the sealed capacitor system at later stages (e.g., during operation).
  • the mixing in step (a) is carried out in a stepwise manner.
  • the mixing in step (a) is carried out utilizing a mixing apparatus selected from a mixer, a hand mixer, a homogenizer or a sonicator.
  • step (a) is carried out utilizing a mixer.
  • the mixing is performed at a speed of from about 20 to about 120 RPM.
  • the mixing is performed at a speed of from about 40 to about 100 RPM.
  • the mixing speed is increased throughout step (a).
  • the weight ratio of activated carbon and the alkaline electrolyte in step (a) ranges from about 35 to about 45 wt% activated carbon and from about 55 to about 65 wt% electrolyte.
  • the heating in step (b) is carried out at a temperature of about 50 to about 100 °C. In further embodiments, the heating in step (b) is carried out at a temperature of about 60 to about 90 °C or of from about 70 to about 80 °C. Each possibility represents a separate embodiment of the invention.
  • the processing of the homogeneous paste obtained in step (a) can be achieved by several commonly used industrial methods.
  • the processing of step (c) is carried out utilizing a method selected from rolling, calendering, coating, casting, pressing, printing, 3D printing or a combination thereof.
  • the processing of step (c) is carried out utilizing rolling.
  • the rolling as described above is performed on an inert polymeric laminate.
  • the laminate is peeled off after the rolling process to further allow the end-product electrode, which is a free-standing electrode.
  • the processing of step (c) further comprises pressing.
  • the paste is pressed between two non-conducting polymer sheets.
  • the present invention provides a method for the preparation of the supercapacitor as described hereinabove, comprising preparing the first supercapacitor electrode comprising (a) mixing aqueous alkaline electrolyte with low purity activated carbon having an ash content of above about 5 wt%, with optional stirring, to achieve a homogeneous paste; (b) heating the paste obtained in step (a); and (c) processing the paste obtained in step (b) to form a standalone homogeneous electrode.
  • the low purity activated carbon has an ash content of above about 7 wt%. In some embodiments, the activated carbon has an ash content of above 10 wt%. In further embodiments, the activated carbon has an ash content of above about 15 wt%. In further embodiments, the method comprises preparing a second porous electrode. In still further embodiments, the method comprises separating the first porous electrode from the second porous electrode by a porous separator. In further embodiments, the method comprises filling the separator with the electrolyte, wherein the electrolyte is in contact with the first porous electrode and with the second porous electrode.
  • Example 1 Electrode preparation
  • a free-standing active carbon-based electrode was prepared utilizing impure carbon source, and without the presence of stabilizing reagents such as binders, silicates or gelling agents.
  • the preparation of 15Kg active carbon (AC) pate was performed as follows: 30 wt% KOH electrolyte solution was prepared using titration against a known standard solution. 6Kg of low purity AC having 10 wt.% ash content was mixed with 4.5Kg of electrolyte solution in a pot and mixed a mixer at a speed of about 40 RPM for ten minutes. Pressure buildup during the stirring caused by the release of gas adsorbed to the carbon was released in a controlled manner.
  • Electrode paste 15 Kg of electrode paste were prepared according to step (a) above and rolled as one batch.
  • the paste was allocated between two laminate layers/foils and pressed by the rolling process to the desired 10 thickness. The process was done at room temperature environment. The rolled paste was cut by die cut to the required electrode shape and size. The laminate layers were removed upon cell assembly.
  • Example 2 Energetic efficiency and capacitance of supercapacitors including different carbon sources and electrolytes.
  • the anodes were prepared as described in Example 1.
  • the alkaline electrolyte utilized was a 30% KOH solution and the acidic electrolyte was a 4.2M sulfuric acid solution (H 2 S0 4 ).
  • Cathodes of identical composition and weight/thickness were used in all the tested supercapacitors.
  • the cathodes had the same composition as the anode (described above) as well as the same weight/thickness.
  • the ESR values of the supercapacitors were measured before the beginning of the cell operation and after 12 charge/discharge cycles.
  • the ESR was measured by HIOKI mili-ohm- meter at a 1kHz frequency.
  • the measured ESR values are summarized in Table 2. It can be seen that the resistance of the alkaline supercapacitors was higher than that of their alkaline counterparts both in the beginning and end of the experiment, but resistance of the alkaline capacitors decreases following cycling. Without wishing to being bound by theory or mechanism of action, it is contemplated that the decrease in the resistance values of the alkaline supercapacitors can be due to the penetration of the electrolyte into the carbon pores.
  • the cells were charged at constant current (CC) up to the voltage of 0.9V, then were left to rest for 5 seconds. Afterwards the cells were discharged at CC (same as charge CC) up to 0.1V and left to rest again for 5 seconds. Capacitance of the supercapacitors including different anodes and electrolytes was calculated from the slope of the discharge curve in the 0.3 V-0.55V potential range.
  • a charge/discharge experiment was performed in order to assess the energetic efficiency of the supercapacitors in terms of energy obtained versus energy invested.
  • the cells were charged and discharged under a constant current of 0.1 A between 0.1V and varying upper potential limits (0.5V - 1.3 V).
  • the highest energetic efficiency was obtained under alkaline conditions.
  • the most energy efficient supercapacitor was the alkaline cell including low purity carbon-based anode (B) when the cells were charged and discharged between 0.1V and 0.9V-1.3V. Its superiority over the high purity carbon-based anode-containing supercapacitor was particularly pronounced at the deeper charge/discharge profiles.
  • the high energetic efficiency at wide potential window cycles is of high importance, as the energetic efficiency of the supercapacitor decreases with the increase of the potential window.
  • the low-purity carbon source offers capacitance which is comparable to and energy efficiency which is even higher than that of the high-purity carbons typically employed in supercapacitor electrodes.
  • Example 3 Leakage current of supercapacitors including different carbon sources and electrolytes
  • Leakage current is an indicator of the energy spent on parasitic reactions, which may lead to self-discharge of the supercapacitor.
  • Low purity carbons are more prone to parasitic reactions due to the higher content of the impurities which can interact with the electrolyte.
  • the effect of the carbon source and the type of electrolyte on the leakage current was tested. Two distinct low purity carbon sources were used to manufacture alkaline and acidic supercapacitors as shown in Table 3.
  • the anodes were prepared as described in Example 1.
  • the cathodes had the same composition as the anode as well as the same weight/thickness.
  • the supercapacitors were tested utilizing both acidic and alkaline electrolytes in order to study the interaction of the electrolyte with the carbon source used in each capacitor.
  • the alkaline electrolyte utilized was a 30% KOH solution and the acidic electrolyte was a 4.2M sulfuric acid solution (H 2 SO 4 ).
  • the leakage current was assessed as follows:
  • the supercapacitor was kept at constant temperature of 23°C for at least 12 hours.
  • the supercapacitor was tested at Discharged condition.
  • the measured leakage current of the acidic supercapacitors was significantly higher than that of the alkaline supercapacitors, for both carbon sources. Both in acidic and alkaline conditions the more contaminated carbon source (supercapacitors E and F) showed higher leakage currents than the less contaminated carbon. Without wishing to being bound by theory or mechanism of action, it is postulated that the high ash content carbon is more prone to parasitic reactions when utilizing acidic environment than an alkaline one. The leakage currents measured for the supercapacitors G and H containing anodes with 10 wt% ash were lower than the ones measured for the supercapacitors E and F containing anodes with 18 wt% ash.
  • alkaline supercapacitors are more tolerant towards the impurities found in the low purity carbon-based electrodes and wider range of low purity carbon sources can be employed in alkaline supercapacitors. It was therefore shown that the combination of a low purity carbon and alkaline electrolyte allows efficient operating conditions with low leakage current involved.
  • Example 4 Cost efficiency of different carbon -based anodes
  • ESR and capacitance of alkaline supercapacitors comprising said anodes were compared to the corresponding data obtained from supercapacitors including anodes containing carbons with various higher purity grades.
  • the anodes were prepared as described in Example 1 and included carbons with 18 wt% ash, 10 wt% ash, 5 wt% ash, and less than 2 wt% ash.
  • the electrolyte was alkaline, comprising a 30% KOH solution.
  • the cathodes had the same composition as the anode as well as the same weight/thickness.
  • the supercapacitors were 6 cm 2 supercapacitor cells.
  • the capacitance was measured as described in Example 2.
  • the measured electrode capacitance at 0,1 A was normalized to the price per gram of the carbon source (capacitance cost-efficiency).
  • Table 4 represents characterization data of the sources and the acquired ESR and capacitance values.
  • Figure 4 represents the electrode capacitance cost-efficiency as a function of carbon ash content. It can be seen that there is a direct correlation between the ash content and commercial viability of the electrode capacitance. The empirical linear relationship is shown in Formula II.
  • Activated carbons employed in commercially available supercapacitors were tested to assess their capacitance cost-efficiency.
  • Typical capacitance provided by such carbons was found to be 80-100 F/g, wherein said carbon cost is 15 $/kg.
  • Capacitance cost-efficiency of the carbon used in commercial supercapacitors therefore ranges between 5333 and 6667 F/$.
  • Formula II it can be estimated that low purity carbon electrodes having above 7 wt% ash, according to the principles of the present invention, provide higher capacitance cost-efficiency than the currently available commercial supercapacitor carbon electrodes.
  • ESR and capacitance measurements were performed in two distinct electrode configurations including: a) symmetric supercapacitor comprising two similar low purity carbon-based electrodes of the invention; and b) asymmetric supercapacitor comprising a first low purity carbon-based electrode of the invention and a second electrode comprising Mn0 2 , carbon-nanotubes and active carbon.
  • the low-purity carbon- based electrodes were prepared as described in Example 1.
  • the mass of the electrodes in the symmetric supercapacitor were 0.32 gr for each carbon-based electrode and the mass of the electrodes in the asymmetric supercapacitor were 0.3 gr of the low purity carbon electrode and 0.38 gr of the Mn0 2 -based electrode.
  • Both supercapacitors were 6 cm 2 cells and were sealed under 10Kgf/cm 2 .
  • the electrode thicknesses which were evaluated in both supercapacitors were 600 ⁇ and 300 ⁇ .
  • the electrolyte used was 30% KOH.
  • Example 6 Separator and separator-paste interaction effect on the capacitance
  • Anodes of identical composition and weight/thickness were used in all the tested supercapacitors.
  • the anodes were prepared as described in Example 1.
  • the alkaline electrolyte utilized was a 30% KOH.
  • Cathodes of identical composition and weight/thickness were used in all the tested supercapacitors. Cathodes are identical to the anodes so they contain the same.
  • the capacitance and internal resistance were measured for 10 different supercapacitors, each having a distinct separator with different characteristics as described in Table 5.
  • Said electrochemical characterization tests were performed at different temperatures, ranging from - 30°C to 65°C in order to assess the electrodes' stability at a wide temperature range.
  • the ESR DC was measured at 0.1 and lAmp for each supercapacitor, and ESR AC was measured in order to gain more information about the ionic resistance of the measured system.
  • separator's thickness is an important factor affecting the supercapacitor's processibility. In order to allow effective production of the supercapacitor, a relatively thick separator is considered to be advantageous. According to Figures 8 and 9, supercapacitors comprising separators No. 2 and 8, both comprising polyvinyl alcohol coated polyethylene separators gave rise to low internal resistance in both room temperature measurements and at subzero measurements carried out at -30°C.
  • supercapacitor comprising separator No. 8 provided the lowest internal resistance in a wide temperature range, and demonstrated superiority over supercapacitor comprising separator No. 2 (thinner separator).

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Abstract

La présente invention concerne un supercondensateur comprenant au moins une cellule de condensateur comprenant une première électrode poreuse, une seconde électrode poreuse, un électrolyte alcalin aqueux étant en contact avec lesdites première et seconde électrodes poreuses, et un séparateur séparant la première électrode poreuse de la seconde électrode poreuse, la première électrode poreuse comprenant un charbon actif de faible pureté ayant une teneur en cendres supérieure à environ 7 % en poids, et la première électrode poreuse étant imprégnée d'un électrolyte alcalin aqueux. Le supercondensateur de l'invention offre une capacité améliorée, une efficacité énergétique élevée et un faible courant de fuite. La présente invention concerne en outre des procédés de préparation de l'électrode de charbon de faible pureté.
PCT/IL2017/051321 2016-12-06 2017-12-06 Supercondensateur comprenant une électrode de charbon de faible pureté et électrolyte aqueux WO2018104942A1 (fr)

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CN109289874A (zh) * 2018-11-16 2019-02-01 安徽师范大学 一种钴掺杂二硫化锡纳米片阵列材料及其制备方法和应用
CN110648863A (zh) * 2019-09-30 2020-01-03 中南民族大学 一种碳纳米管薄膜复合金属硫化物柔性非对称超级电容器的制备方法
CN111816860A (zh) * 2020-07-27 2020-10-23 广州大学 一种电极用复合材料及其制备方法
CN113096967A (zh) * 2021-04-16 2021-07-09 广德天运新技术股份有限公司 基于碳纤维的高比容量超级电容器电极材料及制备方法

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US6110335A (en) * 1995-11-30 2000-08-29 Superfarad, Ltd. Electrode having a carbon material with a carbon skeleton network and a capacitor having the same
DE102008010563A1 (de) * 2008-02-22 2009-09-03 Süd-Chemie AG Verwendung von Aktivkohlen als Superkondensator

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JPH01165108A (ja) * 1987-12-22 1989-06-29 Asahi Glass Co Ltd 電気二重層コンデンサ
US6110335A (en) * 1995-11-30 2000-08-29 Superfarad, Ltd. Electrode having a carbon material with a carbon skeleton network and a capacitor having the same
DE102008010563A1 (de) * 2008-02-22 2009-09-03 Süd-Chemie AG Verwendung von Aktivkohlen als Superkondensator

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109289874A (zh) * 2018-11-16 2019-02-01 安徽师范大学 一种钴掺杂二硫化锡纳米片阵列材料及其制备方法和应用
CN109289874B (zh) * 2018-11-16 2021-03-16 安徽师范大学 一种钴掺杂二硫化锡纳米片阵列材料及其制备方法和应用
CN110648863A (zh) * 2019-09-30 2020-01-03 中南民族大学 一种碳纳米管薄膜复合金属硫化物柔性非对称超级电容器的制备方法
CN110648863B (zh) * 2019-09-30 2021-04-13 中南民族大学 一种碳纳米管薄膜复合金属硫化物柔性非对称超级电容器的制备方法
CN111816860A (zh) * 2020-07-27 2020-10-23 广州大学 一种电极用复合材料及其制备方法
CN111816860B (zh) * 2020-07-27 2022-02-18 广州大学 一种电极用复合材料及其制备方法
CN113096967A (zh) * 2021-04-16 2021-07-09 广德天运新技术股份有限公司 基于碳纤维的高比容量超级电容器电极材料及制备方法
CN113096967B (zh) * 2021-04-16 2024-01-23 广德天运新技术股份有限公司 基于碳纤维的高比容量超级电容器电极材料及制备方法

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