Multilayered carbon-based electrode and methods of making same

Abstract

An electrode and a supercapacitor comprising such an electrode are disclosed. The electrode may include a multilayered structure comprising at least one layer made from a mixture of two different types of carbon particles and a binder. At least one of the carbon types is an activated carbon, meaning a carbon having a surface area of between 2000 to 4000 [m2 / g], and the other type of carbon is nanostructured carbon having at least one dimension lower than 100 nm and an average surface area of between 200 to 2500 [m2 / g]. Such an electrode, when assembled in a supercapacitor increases the energy storage capacity of the supercapacitor.

Description

MULTILAYERED CARBON-BASED ELECTRODE AND METHODS OF MAKING SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of US Provisional Patent Application No. 63 / 633,907, filed 15 April 2024 and Israeli Patent Application No. 314818, filed 7 August 2024 which are hereby incorporated by reference in their entirety.FIELD OF THE INVENTION

[0002] The present invention relates generally to electrodes and supercapacitors. More specifically, the present invention relates to electrodes and supercapacitors having an active carbon layer.BACKGROUND OF THE INVENTION

[0003] The recent rise in global population has driven an increase in the consumption of natural resources such as fossil fuels, coal, and natural gases. The demand leads us to seek renewable energy resources. Further, the demand promoted the development of the necessary technologies, such as sustainable energy conversion and storage technologies. Energy- storing devices are the main solution for our global energy crisis.

[0004] Supercapacitors, also known as electrochemical capacitors, are a type of power storage devices between the traditional electrostatic capacitors and batteries. Supercapacitors have great potential as an efficient energy storage device, and they could be a future alternative to batteries.

[0005] Several types of supercapacitors are known and in use. Electrostatic double-layer capacitors (EDLCs), Electrochemical pseudo-capacitors, and Hybrid capacitors are the most common.

[0006] EDLCs are typically made up of two carbon-based electrodes, an electrolyte and a separator. Similar to the ordinary capacitor, EDLCs store the charges by non-faradaic manner and there is no charge conversion between the electrode and electrolyte. Hence, the electrode material is static in nature at all working potentials. Various carbon-based materials can be used as EDLC electrodes like carbon nanotubes, allotropes of graphene, activated black carbon, and carbon aerogels.

[0007] Pseudo-capacitors are supercapacitors where charges are stored through the electrosorption, redox reaction or intercalation process. In faradaic charge storagemechanism, the charge conversion takes place across the double layer. Compared to the EDLC electrode, the charge storing capacity of pseudo-capacitive electrode is higher, but these electrodes have limited cycling stability and low power density due to the material degradation affected by phase change and faradaic reactions. The factors affecting the electrochemical performance of pseudo-capacitors are the specific surface area of the electrode, particle size, conductivity of the active material, the construction of the device and type of electrolyte.

[0008] Hybrid supercapacitor configuration utilizes the benefits from both double layer and pseudo-capacitive. Hybrid capacitors possess both faradaic and non-faradaic charge storing mechanisms (EDLCs and pseudocapacitive). In such conditions, one system's strengths are the other's weaknesses, and vice versa. Hybridization of EDLC and pseudo-capacitor is a dynamic path to solving problems related to both systems. This can be done by the asymmetric combination of different positive and negative electrodes (EDLC and pseudocapacitor) to utilize the benefit of both electrodes. Both mechanisms operate simultaneously in such a system, which is known as an asymmetric hybrid capacitor. Additionally, the complex type electrodes with carbon-based material are merged either with metal oxide, metal chalcogenide, or conducting polymer, which exhibit both EDLC and pseudocapacitive behaviors in a single electrode. Similarly, the battery-type hybrid is created by considering one electrode as battery type and the other as capacitive type electrode. Due to their efficient electrochemical performance and unique combination that can meet the needs of various applications, supercapacitor research has dramatically increased over the last few decades and has been fired through an emerging number of applications.

[0009] Supercapacitors have the advantages of high-power density, safety, a broad range of operating temperatures, and superfast charge times. The charging time for a supercapacitor generally ranges from a few seconds to minutes, and the typical cycling life can reach 100,000 cycles with only a slight performance degradation. These technological features allowed supercapacitors to become the next generation of energy storage devices. However, they still have low energy densities. The energy density of standard / commercial EDLC supercapacitor devices is limited to 10 Whkg-1. Thus, supercapacitors are presently only used as electric vehicle starters and cabin door switchers for airplanes, which require a high- power density and a short discharge time. The bottleneck is the running distance (energy density), which should be at least 100 km for use in Electric vehicles. Thus, the energydensity must also be greater than 100 Whkg-1. In this case, the mileage goes to infinity with negligible charging times. Electric vehicle mobility can be greatly enhanced using supercapacitors whose energy density performance is competitive with Lithium-ion batteries.

[0010] Therefore, the aim of the claimed invention is to provide an improved electrode that may improve the energy storage capacity in energy storage devices, such as, supercapacitors.SUMMARY OF THE INVENTION

[0011] Some aspects of the invention may be directed to an electrode and a supercapacitor comprising such an electrode. The electrode may include a multilayered structure comprising at least one layer made from a mixture of two different types of carbon particles and a binder. In some embodiments, at least one of the carbon types is an activated carbon, meaning a carbon having a surface area of between 2000 to 4000 [m2 / g] and the other type of carbon is nanostructured carbon having at least one dimension lower than 100 nm and an average surface area of between 200 to 2500 [m2 / g]. Such an electrode, when assembled in a supercapacitor, increases the energy storage capacity of the supercapacitor.

[0012] An electrode according to some embodiments of the invention may include: a multilayered structure comprising: a conductive substrate; and an active carbon-based layer comprising a mixture of: a first type of activated carbon, at least one nano structured carbon, and a binder, wherein the first type of activated carbon comprises carbon particles may be characterized by an average surface area of between 2000 to 4000 [m2 / g]; and the nanostructured carbon may be characterized by having at least one dimension between 5 to 100 nm and an average surface area of between 200 to 250 [m2 / g].

[0013] In some embodiments, the active carbon-based layer may further include at least a second type of activated carbon. In some embodiments, the second type of activated carbon may differ in at least one of, adsorption capacity, surface area, pore size, desorption capacity, pore volume, than the first type of activated carbon. In some embodiments, the mixture may include between 30 to 90 wt.% of the at least one first type of activated carbon.

[0014] In some embodiments, the active carbon-based layer may have an average mass loading of between 4 to 20 mg / cm2. In some embodiments, the at least one other type of carbon may include at least one of: single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), and carbon nanospheres.

[0015] In some embodiments, the mixture may include two types of other carbon, a first type of carbon at an amount of between 4 to 15 wt.% and a second type of carbon at an amount of between 2.5 to 20 wt.%. In some embodiments, the amount of the at least one other type of carbon in the mixture may be between 5 to 32 wt.%. In some embodiments, the active carbon-based layer further may include conductive particles selected from: metal oxide particle, metal particles, metal chalcogenides, bi-metal particles, tri-metal particles, and any combination thereof.

[0016] In some embodiments, the binder may be a polymeric binder. In some embodiments, the polymeric binder may be at least one of: sulfonated tetrafluoroethylene based fluoropolymer-copolymer (Nafion), Polytetrafluoroethylene (PTFE), Poly vinylidene fluoride (PVDF), Carboxymethyl cellulose (CMC), epoxy resin, acrylic resin, Polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), and any copolymer thereof.

[0017] In some embodiments, the conductive substrate may include, at least one of, one or more metals, conductive composite, conductive ceramics, and carbon cloth, carbon fiber, carbon paper, and metal foam. In some embodiments, the active carbon-based layer may include a first surface in contact with the conductive substrate and a second surface; and wherein the multilayered structure further comprises an active material layer attached to the second surface. In some embodiments, the active material may include nanostructures of at least one of: a metal-chalcogen compound, metal-oxides, PtPdSn, Co, Pt, Au, Ag, Ni, Mg, V, and Mn. In some embodiments, the metal-chalcogen compound may include a metal comprising at least one of Ag, Au, Co, Ni, Mn, Cu, V, Ni, Fe, Mn, Sn, and any combination thereof, and at least one of the following chalcogens Te, Se, and S. In some embodiments, the mass loading of the active material layer is between 0.1 and 4 mg / cm2.

[0018] In some embodiments, the multilayered structure may further include a conductive layer located between the conductive substrate and the carbon-based layer. In some embodiments, the mass loading of the conductive layer is between 0.1 to 1 mg / cm2. In some embodiments, the conductive layer may include a mixture of between 70 to 90 wt.% carbon particles, between 5 to 20 wt.% conductive particles, and between 2 to 15 wt.% of the binder.

[0019] Some additional aspects of the invention may be directed to a supercapacitor. The supercapacitor may include: a first electrode; a separator comprising an electrolyte; and a second electrode. In some embodiments, at least one of the first electrode and the secondelectrode comprises: a conductive substrate; and an active carbon-based layer comprising a mixture of: a first type of activated carbon, at least one nanostructured carbon, and a binder, wherein the at least one first type of activated carbon comprises carbon particles characterized by an average surface area of between 2000 to 4000 [m2 / g] and the nanostructured carbon may be characterized by having at least one dimension between 5 to 100 nm and an average surface area of between 200 to 2500 [m2 / g].

[0020] In some embodiments, the active carbon-based layer may have an average mass loading of between 4 to 20 mg / cm2. In some embodiments, the active carbon-based layer may have other type of carbon may include at least one of: single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT),and carbon nanospheres.

[0021] In some embodiments, the mixture may include two types of other carbon, a first type of carbon at an amount of between 4 to 15 wt.% and a second type of carbon at an amount of between 2.5 to 20 wt.%. In some embodiments, the amount of the at least one other type of carbon in the mixture may be between 5 to 32 wt.%. In some embodiments, the active carbon-based layer further may include conductive particles selected from: metal oxide particle, metal particles, metal chalcogenides, bi-metal particles, tri-metal particles, and any combination thereof.

[0022] In some embodiments, the binder may be a polymeric binder. In some embodiments, the polymeric binder may be at least one of: sulfonated tetrafluoroethylene based fluoropolymer-copolymer (Nafion), Polytetrafluoroethylene (PTFE), Poly vinylidene fluoride (PVDF), Carboxymethyl cellulose (CMC), epoxy resin, acrylic resin, Polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), and any copolymer thereof.

[0023] In some embodiments, the conductive substrate may include, at least one of, one or more metals, conductive composite, conductive ceramics, and carbon cloth, carbon fiber, carbon paper, and metal foam. In some embodiments, the active carbon-based layer may include a first surface in contact with the conductive substrate and a second surface; and wherein the multilayered structure further comprises an active material layer attached to the second surface. In some embodiments, the active material may include nanostructures of at least one of: a metal-chalcogen compound, metal-oxides, PtPdSn, Co, Pt, Au, Ag, Ni, Mg, V, and Mn. In some embodiments, the metal-chalcogen compound may include a metalcomprising at least one of Ag, Au, Co, Ni, Mn, Cu, V, Ni, Fe, Mn, Sn, and any combination thereof, and at least one of the following chalcogens Te, Se, and S. In some embodiments, the mass loading of the active material layer is between 0.1 and 4 mg / cm2.

[0024] In some embodiments, the multilayered structure may further include a conductive layer located between the conductive substrate and the carbon-based layer. In some embodiments, the mass loading of the conductive layer is between 0.1 to 1 mg / cm2. In some embodiments, the conductive layer may include a mixture of between 70 to 90 wt.% carbon particles, between 5 to 20 wt.% conductive particles, and between 2 to 15 wt.% of the binder.

[0025] Some additional aspects of the invention may include a method of making an electrode. The method may include: providing a conductive substrate; and depositing a carbon-based layer, on top of the conductive substrate, comprising a mixture of: a first type of activated carbon, at least one nanostructured carbon, a solvent and a binder, wherein the at least one first type of activated carbon comprises carbon particles characterized by an average surface area of between 2000 to 4000 [m2 / g] and the nano structured carbon may be characterized by an average particle size of between 5 to 500 nm and an average surface area of between 200 to 2500 [m2 / g].

[0026] In some embodiments, the solvent may be selected from ethanol, isopropanol, acetone, water, and any combination thereof. In some embodiments, the method may further include depositing a conductive layer between the conductive substrate and the carbon-based layer. In some embodiments, the method may further include depositing an active material layer on top of the carbon-based layer. In some embodiments, the active material may include nanostructures of at least one of: a metal-chalcogen compound, metal-oxides, PtPdSn, Co, Pt, Au, Ag, Ni, Mg, V, and Mn.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0028] Figs. 1A, IB, 1C, and ID are illustrations of one-sided electrodes according to some embodiments of the invention;

[0029] Figs. IE, IF and 1G is are illustrations of double-sided electrodes according to some embodiments of the invention;

[0030] Figs. 2A and 2B are illustrations of supercapacitors according to some embodiments of the invention;

[0031] Fig. 2C is an illustration of a supercapacitor made from stacking electrodes according to some embodiments of the invention;

[0032] Fig. 3 is a flowchart of a method of making an electrode according to some embodiments of the invention;

[0033] Figs. 4A, 4B, 4C, 4D, and 4E are high-resolution scanning electron microscopy (HRSEM) images of carbon particles according to some embodiments of the invention;

[0034] Figs. 5A, 5B, and 5C are graphs showing pore size distribution of various carbon particles according to some embodiments of the invention;

[0035] Figs, 5D, 5E, and 5F are graphs of adsorption and desorption isotherms of various carbon particles according to some embodiments of the invention;

[0036] Fig. 6 includes graphs of Fourier-transform infrared spectroscopy (FTIR) analysis of various types of carbon particles according to some embodiments of the invention;

[0037] Fig. 7 includes SEM, STEM images and EDS analysis of a active carbon layer that incorporate PtPdSn nanoparticles according to some embodiments of the invention;

[0038] Fig. 8 shows binocular light microscopy images of electrodes according to some embodiments of the invention;

[0039] Reference is now made to Figs. 9A which is a CV in a potential range of 0-2.8V and 9B which is GCD plots in current density of ±20-850 mA, of Carbon-based EDEC device (503mg) with carbon mixture consisting of AC 75 wt.%, MWCNT 7.5 wt.%, graphite powder 7.5 wt.%, with PVDF and NMP, according to some embodiments of the invention.

[0040] Figs. 10A, 10B, and 10C are EIS, CV and GCD graphs for carbon-based electrodes with CMC and water as a solvent, according to some embodiments of the invention; and

[0041] Figs. 11A, 11B, are CV in a potential range of 0-3.5V, and GCD plot in current density of ±10-400 mA, of Carbon-based EDLC device (Device 18-280mg) with carbon mixture consisting of 75 wt.% AC, 25 wt.% MWCNT, with PVDF binder and Dimethylformamide (DMF) solvent, according to some embodiments of the invention.

[0042] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of someof the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0043] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0044] Some aspects of the invention are directed an electrode to be assembled in electrochemical devices, for example, energy storage devices, such as, supercapacitors. The supercapacitors may be hybrid supercapacitors that may be symmetric supercapacitors or asymmetric supercapacitors. The electrode may include at least a conductive substrate and an active carbon-based layer. The active carbon-based layer may include a mixture of at least one first type of activated carbon, at least one other type of carbon, and a binder.

[0045] Some aspects of the invention are aimed for improving the potential window, the current density, and the electrodes’ conductivity, thereby lowering the resistance of the electrodes. The synthesized carbon layer electrodes may be directed for improving the electrochemical parameters by manipulating the carbon mixture coating layer and its thickness (e.g., mass loading).

[0046] As used herein, a carbon-based material may include any carbon-based morphology, for example, graphite powder, allotropes of graphene, black carbons, etc. and nano structured carbon. Some nonlimiting examples for nanostructured carbon may include, carbon nanolayer, single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nano-pearl powder, and the like.

[0047] As used herein an “activated carbon” may refer to any type of carbon particles having an average surface area of between 2000 to 4000 [m2 / g]. Activation of carbon particles may be performed as disclosed herein below in the Example section.

[0048] As used herein a “functionalized carbon” may refer to a modification of surface sites including attachment of new carboxylic (-COOH), carbonyl (-C=O), and hydroxyl (-OH) functional groups and removal of impurities.

[0049] As used herein, a “nanostructure” may include any morphology of a crystalline, amorphous or semi-crystalline material having at least one dimension of at most 100 nm, e.g., between 5 to 100 nm. For example, a nanolayer may have a thickness of at most 100 nm. Other examples, may include nanoparticles having an average diameter of at most 100 nm, nanotube having an average diameter of at most 100 nm, nanosheets having a thickness of at most 100 nm, nano wires having a width of at most 100 nm, and nanoflower having an average diameter of at most 100 nm and the like.

[0050] In some embodiments, the effective electrochemical performance of the supercapacitor is directly dependent on the selection of active electrode material and a suitable electrolyte. The surface morphology, crystal structure, and thickness of the layers are the parameters for achieving efficient electrochemical performance.

[0051] In some embodiments, the following aspects should be taken into consideration when fabricating an electrode for supercapacitor application:• The electrode material may have a large surface area, porosity, and conductivity to have superior electrochemical performance.• The electrolyte may penetrate into the porous surface of the electrode material.• The use of good electrically conducting materials reduces resistance and allows for high-power delivery.• Environmental-friendly and non-toxic electrode.• A simple, low-cost, industry-scalable approach may be engaged to fabricate large- area electrodes.

[0052] The energy density (E) and power density (P) of supercapacitor are calculated using equations (1) and (3)E = (1 / 2 CV2) / (m*3600), (1)C = (At*I) / V, (2)P = (0.12*V2) / (m*ESR), (3)ESR = AV / I, (4)

[0053] Where C is the DC capacitance in Farad, V is the potential window in Volt, m is the device mass in kg, At is the discharge time in second, I is the current in Ampere, and AV isthe voltage drop during first 10 ms of discharge. According to this equation, embodiments of the invention focus on enhancing the energy density of supercapacitors by improving their capacitance and working voltage.

[0054] Therefore, materials and dimensions selected according to embodiments of the invention were directed to manufacture an improved hybrid supercapacitor taking into consideration the above-mentioned aspects.

[0055] Reference is now made to Fig. 1A which is an illustration of an electrode according to some embodiments of the invention. An electrode 100a may include a multilayered structure comprising at least a conductive substrate 10 and an active carbon-based layer 20.

[0056] In some embodiments, conductive substrate 10 (also known as a current collector) may include at least one of, one or more metals, conductive composite, conductive ceramics, and carbon cloth, carbon fiber, carbon paper, metal foam, and the like. In some embodiments, conductive substrate 10 may have a thickness of between 10-100 pm, and a weight of 1-100 mg / cm2.

[0057] In some embodiments, active carbon-based layer 20 may include a mixture of a first type of activated carbon, at least one nanostructured carbon, and a binder. The first type of activated carbon may include carbon particles characterized by an average surface area of between 2000 to 4000. In a nonlimiting example the surface area may be characterized using the Brunauer-Emmett-Teller (BET) surface area analysis, discussed in the result section herein below. In some embodiments, the first type of activated carbon may include carbon particles characterized by an average surface area of between 500 to 1000 [m2 / g], 750 to 1500 [m2 / g], 1000 to 1750 [m2 / g], 1250 to 2000 [m2 / g], 1500 to 2500 [m2 / g], 2250 to 3000 [m2 / g], or even 2000 to 4000 [m2 / g] and any value or range in between.

[0058] In some embodiments, the mixture may include between 5 to 90 wt.% of the first type of activated carbon and any value or range in between. For example, the mixture may include: between 5 to 10 wt.% of the first type of activated carbon; the mixture may include: between 10 to 40 wt.% of the first type of activated carbon; the mixture may include: between 10 to 20 wt.% of the first type of activated carbon; the mixture may include: between 30 to 40 wt.% of the first type of activated carbon; the mixture may include: between 30 to 40 wt.% of the first type of activated carbon; between 35 to 45 wt.% of the first type of activated carbon; between 40 to 50 wt.% of the at least one first type of activated carbon; between 45 to 55 wt.% of the first type of activated carbon; between 50 to 60 wt.%of the first type of activated carbon; between 55 to 65 wt.% of the first type of activated carbon; between 60 to 70 wt.% of the a first type of activated carbon; between 60 to 80 wt.% of the first type of activated carbon; between 60 to 90 wt.% of the first type of activated carbon; and between 30 to 60 wt.% of the first type of activated carbon.

[0059] In some embodiments, the at least one other nanostructured carbon may include at least one of: single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nanospheres and the like.

[0060] In some embodiments, the nano structured carbon is characterized by an average surface area of between 200 to 2500 [m2 / g]. In some embodiments, the surface area of nanostructured carbon is between, 200 to 500 [m2 / g], 400 to 1000 [m2 / g], 1000 to 1500 [m2 / g], between 1200 to 1600 [m2 / g], between 1500 to 2000 [m2 / g], between 1700 to 2500 [m2 / g], and any value or range in between. Some nonlimiting examples are given in the Examples section herein below.

[0061] In some embodiments, layer 20 may further include a second type of activated carbon. Therefore, active carbon-based layer 20 may include two different types of activated carbon. The two types of activated carbons may differ in at least one of, adsorption capacity, surface area, pore size, desorption capacity, pore volume, and the like. For example, the first type of activated carbon may have average surface area of between 2000 to 3000 [m2 / g] and the second type of activated carbon may have average surface area of between 3000 to 4000 [m2 / g],

[0062] In another example, the first type of carbon may have average cumulative pore volume of 0.1 to 1 [cm2 / nm / g] (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 [cm2 / nm / g] or any value or range in between) and the second type of carbon may have average cumulative pore volume of 0.01 to 0.1 [cm2 / nm / g] (e.g., 0.01, 0.02, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1. [cm2 / nm / g] or any value or range in between).

[0063] In yet another example, the first type of carbon may have an average adsorption capacity of between 10 to 20 [cm2 / g] (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 [cm2 / g] or any value or range in between) and the second type of carbon may have an average adsorption capacity of between 1 to 10 [cm2 / g] (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, [cm2 / g] or any value or range in between).

[0064] In some embodiments, the amount of the nano structured carbon in the mixture is between 5 to 32 wt.%. For example, the amount of the at least one other type of carbon inthe mixture may be between 5 to 10 wt.%, between 7 to 15 wt.%, between 8 to 20 wt.%, between 10 to 18 wt.%, between 15 to 22 wt.%, between 17 to 25 wt.%, between 20 to 28 wt.%, between 27 to 32 wt.%, between 25 to 30 wt.% and any value or range in between.

[0065] In some embodiments, the mixture may include two types of other carbon, a first type of carbon at an amount of between 4 to 15 wt.% and a second type of carbon at an amount of between 2.5 to 20 wt.%. For example, the first type of other carbon may be an activated carbon and the nanostructured carbon may be SWCNT, DWCNT, MWCNT, carbon nanospheres, and the like. In another example, the first type of other carbon may be MWCNT and the second type of other carbon may be functionalized carbon.

[0066] In some embodiments, the mixture may include the activated carbon at an amount of between 4 to 6 wt.%, between 5 to 8 wt.%, between 7 to 9 wt.%, between 8 to 12 wt.%, between 10 to 15 wt.%, between 11 to 15 wt.% and any value or range in between. In some embodiments, the mixture may include the nano structured carbon at an amount of between 2.5 to 5 wt.%, between 4 to 8 wt.%, between 6 to 9 wt.%, between 7 to 11 wt.%, between 10 to 15 wt.%, between 12 to 17 wt.%, between 15 to 18 wt.%, between 14 to 19 wt.%, between 16 to 20 wt.% and any value or range in between.

[0067] In some embodiments, the binder may be any suitable polymeric binder. Some nonlimiting examples for binders may include sulfonated tetrafluoroethylene based fluoropolymer-copolymer (Nafion), Polytetrafluoroethylene (PTFE), Poly vinylidene fluoride (PVDF), Carboxymethyl cellulose (CMC), epoxy resin, acrylic resin, Polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), agar-agar, Alginate, Amylose, Arabic gum, Carrageenan, Casein, Chitosan, Cyclodextrins, ethylene propylene diene monomer (EPDM), Gelatin, Gellan gum, Guar gum, Cellulose, Pestine, Poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), Polyacrylic acid (PAA), Poly(methyl acrylate) (PMA), Polyvinyl alcohol (PVA), Polyvinyl acetate (PVAc), Polyacrylonitrile (PAN), Polyaniline (PANi), polyethylene (PE), Polyimide (PI), Polystyrene (PS), Polyurethane (PU), Polyvinyl butyral (PVB), Polyvinylpyrrolidone (PVP), Starch, Styrene-butadiene (SBR), Polytetrafluoroethylene (PTFE), and any copolymer and combination thereof.

[0068] In some embodiments, active carbon-based layer 20 may further include conductive particles. Some nonlimiting examples may include: metal oxide particles, metalchalcogenides, metal particles Bi-metallic, tri-metallic or any alloyed particles and any combination thereof.

[0069] In some embodiments, active carbon-based layer 20 may have an average mass loading of between 4 to 20 mg / cm2. For example, active carbon-based layer 20 may have an average mass loading of between 4 to 6 mg / cm2, between 5 to 7 mg / cm2, between 7 to 10 mg / cm2, between 8 to 13 mg / cm2, between 12 to 16 mg / cm2, between 5 to 20 mg / cm2, and any value or range in between.

[0070] Reference is now made to Fig. IB which is an illustration of another electrode according to some embodiments of the invention. An electrode 100b may include conductive substrate 10 and active carbon-based layer 20 which are substantially similar to conductive substrate 10 and active carbon-based layer 20 of electrode 100a. Electrode 100b may further include an active layer 30. In some embodiments, active carbon-based layer 20 may include a first surface in contact with conductive substrate 10 and a second surface; and wherein the multilayered structure of electrode 100b may further include active material layer 30 attached to the second surface.

[0071] In some embodiments, the active material in layer 30 may include nanostructures of at least one of: a metal-chalcogen compound, metal-oxides, PtPdSn, Co, Pt, Au, Ag, Ni, Mg, V, and Mn. In some embodiments, the metal-chalcogen compound comprises a metal comprising at least one of Ag, Au, Co, Ni, Mn, Cu, V, Ni, Fe, Mn, Sn, and any combination thereof, and at least one of the following chalcogens Te, Se, and S.

[0072] In some embodiments, the materials in layers 20 and 30 may be mixed together to form a single layer comprising a mixture of at least one first type of activated carbon, at least one other type of carbon, the nanostructures, and the binder

[0073] In some embodiments, metal-chalcogen compound layer 30 may include at least one of, SnSe nanostructures, CuSe nanostructures, CuS nanostructures, CuTe nanostructures, SnTe nanostructures, SnS nanostructures, AgS nanostructures, AgSe nanostructures, AgTe nanostructures, NiS nanostructures, NiSe nanostructures, NiTe nanostructures, nanostructures, CuSnS nanostructures, CuSnSe nanostructures, CuSnTe nanostructures, nanostructures, NiSnS nanostructures, NiSnSe nanostructures, NiSnTe nanostructures, nanostructures, CoSnS nanostructures, CoSnSe nanostructures, CoSnTe nanostructures, nanostructures, AgSnS nanostructures, AgSnSe nanostructures, AgSnTe nanostructures, etc.

[0074] In some embodiments, a mass loading of layer 30 is between 0.1 mg / cm2to 4 mg / cm2, for example, 0.1 mg / cm2, 0.3 mg / cm2, 0.5 mg / cm2, 1 mg / cm2, 2 mg / cm2, 4 mg / cm2, 4 mg / cm2, and any value in between.

[0075] Reference is now made to Fig. 1C which is an illustration of another electrode 100c according to some embodiments of the invention. The multilayered structure of electrode 100c may include a conductive layer 15 located between conductive substrate 10 and carbon-based layer 20. In some embodiments, conductive substrate 10 and active carbonbased layer 20 may be substantially similar to conductive substrate 10 and active carbonbased layer 20 of electrodes 100a and 100b.

[0076] Conductive layer 15 may include a mixture of between 70 to 90 wt.% carbon particles, between 5 to 20 wt.% conductive particles, and between 2 to 15 wt.% of the binder. For example, conductive layers 15 may include a mixture of between 70 to 90 wt.% graphite, 20 to 5 wt.% MWCNT and a binder (e.g., conductive binder (e.g., PVDF, CMC, and the like)). In some embodiments, the mass loading of conductive layer 15 may be between 0.1 mg / cm2to 1 mg / cm2. In nonlimiting examples, the conductive particles may include, metal particles, metal oxide particles, metal chalcogenides particles, Graphite powder, MWCNTs, carbon black, Black pearl, Super P, Acetylene black carbon, and the like.

[0077] Reference is now made to Fig. ID which is an illustration of another electrode 100c according to some embodiments of the invention. An electrode lOOd may include the following multilayered structure: conductive substrate 10, conductive layers 15 applied on one side to conductive substrate 10, active carbon-based layer 20 applied on top of the free surface of conductive layers 15, and an active layer 30 applied on the free surface of active carbon-based layer 20.

[0078] In some embodiments, electrodes 100a, 100b, 100c and lOOd may be assembled in a supercapacitor as discussed herein below with respect to Figs. 2A, 2B and 2C.

[0079] In some embodiments, the multilayered structure may be applied on both surfaces of the conductive substrate, forming a two-sided electrode, as illustrated in Figs. IE, IF and 1G.

[0080] Electrode lOOe illustrated in Fig. IE may include two active carbon-based layers 20 each being applied to an opposite surface of conductive substrate 10.

[0081] Electrode lOOf illustrated in Fig. IF may include in addition to the two active carbonbased layers 20, two active layers 30, each being applied to an opposite free surface of a corresponding carbon-based layer 20.

[0082] Electrode 100g illustrated in Fig. 1G may include the multilayered structure of electrode lOOd applied from two opposite sides of conductive substrate 10. Electrode 100g may include the following layering sequence active layer 30 / active carbon-based layer 20 / conductive layer 15 / conductive substrate 10 / conductive layer 15 / active carbon-based layer 20 / active layer 30.

[0083] Electrodes lOOe, lOOf, and 100g may be assembled in a supercapacitor, such as, the one discussed and disclosed in Fig. 2C.

[0084] In some embodiments, electrodes 100a- 100g may be plates having any size. Some nonlimiting examples may include plates having a surface of, 2x5cm, 4x5cm, 5x10cm, lOxlOcm, and the like.

[0085] Some aspects of the invention may be directed to a supercapacitor comprising electrodes according to some embodiments of the invention.

[0086] Reference is now made to Fig. 2A which is an illustration of a symmetric supercapacitor according to some embodiments of the invention. A supercapacitor 200a may include two electrodes lOOd or two electrodes lOOd comprising both active carbon-based layer 20 and active layer 30 and an electrolyte 40. In a symmetric supercapacitor, the two electrodes form a mirror symmetry from both sides of electrolyte 40, as illustrated.

[0087] In some embodiments, electrolyte 40 may include an aqueous solution of, KOH, NaOH, NaCl, KC1, Na2SO3, Na2SO4, NaC104, TBABF4, TBAPF6, TEAPF6, K2SO3, TEABF4, EiClO4, EiCl, EiOH, Ei2SO4and the like. In such case, supercapacitor 200a may further include a separator (not shown). In some embodiments, the separator may be made from cellulose paper or gel polymer electrolyte membrane.

[0088] In some embodiments, electrolyte 40 may include organic gel comprises polyvinyl alcohol (PVA), n-methyl-2-pyrrolidone (NMP), cellulose powder, acetonitrile, a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer (Nafion), carboxymethyl cellulose (CMC), and the like. The gel may be mixed and may therefore include ions of one of KOH, NaOH, NaCl, KC1, Na2SO3, Na2SO4, NaC104, TBABF4, TBAPF6, TEAPF6, K2SO3, TEABF4, EiClO4, EiCl, LiOH, Ei2SO4and the like.

[0089] Reference is now made to Fig. 2A which is an illustration of an asymmetric supercapacitor according to some embodiments of the invention. An asymmetric supercapacitor 200b may include a first electrode 100b or first electrode lOOd, a second electrode 100a or second electrode 100c, and an electrolyte 40. In an asymmetric supercapacitor first electrode lOOb / lOOd is different from second electrode lOOa / lOOc by at least active layer 30.

[0090] Electrolyte 40 may be substantially the same as electrolyte 40 of supercapacitor 200a.

[0091] Reference is now made to Fig. 2C which is an illustration of a supercapacitor cell made from stacking electrodes according to some embodiments of the invention. A supercapacitor cell 200c may include a housing 210 that holds a plurality of electrodes according to some embodiments of the invention. The order of the stacking may include having at the top and bottom one- sided electrodes lOOa / lOOb / lOOc / lOOd at which the active carbon layer and the additional layers were deposited only on one side of the conductive substrate. Supercapacitor cell 200c may further include any number of double sided electrodes lOOe / lOOf / lOOg placed between the one side electrodes and separated by separators 220. As should be understood by the one skilled in the art any number of electrodes lOOe / lOOf / lOOg can be included in supercapacitor cell 200c, for example, 1, 2, 3 (as illustrated), 4, 5, 6, 11, 16, 20 or and more.

[0092] In some embodiments, separators 220 may be placed between each two electrodes to prevent short circuits and facilitate ion transport within the cell. Separators 220 may be soaked in an electrolyte 40. A nonlimiting example for separator 220 material may include polypropylene (PP) and polyethylene (PE). In some embodiments, supercapacitor cell 200c may further include a solution of electrolyte 40.

[0093] Housing 210 may be a sealed container, configured to secure, the electrodes stacking, the separators, and the electrolyte.

[0094] In some embodiments, electrolyte 40 of supercapacitors 200a, 200b, and 200c may vary in concentration of the ions. In a nonlimiting, example, electrolyte 40 may include between 0.1-2M, tetra-n-butylammonium hexafluorophosphate (TBAPF6) electrolyte.

[0095] Reference is now made to Fig. 3 which is a method of making an electrode for a supercapacitor according to some embodiments of the invention. In step 310, a conductive substrate 10 may be provided. For example, a plate sized 2x5cm, 4x5cm, 5x10cm, lOxlOcmand the like at a thickness of between 10-100 pm. and a weight of 1-100 mg / cm2may be provided. The plate may be made or may include one or more metals or alloys, conductive composite, conductive ceramics, and carbon cloth, carbon fiber, carbon paper, a metal foam, and the like.

[0096] In some embodiments, an optional step 315 may include depositing a conductive layer 15 on at least one side of conductive substrate 10. A nonlimiting example may include mixing between 70 to 90 wt.% graphite, 20 to 5 wt.% MWCNT, with a binder (e.g., PVDF, CMC, etc.) and a solvent (e.g., N-Methyl-2-pyrrolidone (NMP), water, etc.). Followed by depositing the mixture on one surface of the current collector by at least spraying, printing, applicating, etc.

[0097] In step 320, carbon-based layer, such as, carbon-based layer 20 may be deposited on at least one side conductive substrate 10, or on at least one surface of conductive layer 15. Depositing active carbon-based layer 20 may be done by mixing at least one first type of activated carbon, at least one other type of carbon, solvent, and a binder. The mixture may be deposited by at least one of, spraying, printing, applicating, etc. In some embodiments, the solvent may be selected from NMP, water, alcohols such as, ethanol, isopropanol, Dimethylformamide (DMF), acetone, and the like. Nonlimiting examples for fabricating layers 20 are given herein below.

[0098] In step 325, the method may optionally include depositing an active material layer on top of the active carbon-based layer. For example, active material comprising nanostructures of at least one of: a metal-chalcogen compound, metal-oxides, PtPdSn, Au, Ag, Cu, Ni, Mo, Sn, Co, Pt, Pd, V, Mg, Mn, Ti, Fe, Nb, Zn, Ru, Rh and any combination thereof, may be deposited on top active carbon-based layer 20.

[0099] In a nonlimiting example, nanostructures of metal-chalcogen compounds are synthesized. In some embodiments, the metal includes Cu, Ag, Ni, Co, Sn, and any combination thereof, and the chalcogen is selected from Te, Se, and S. The nanostructures may be mixed with a binder (e.g., PVDF, CMC, etc.) and solvent (e.g., NMP, water, etc.) and be deposited by at least one of, spraying, printing, applicating, etc. on the carbon-based material layer.

[0100] In some embodiments, steps 320 and 325 may be combined together to form a single layer comprising both the active carbon-based material and the nanostructures compound. In some embodiments, the carbon-based material and the nanostructurescompound may be mixed and be deposited by at least one of, spraying, printing, applicating, etc. on the carbon-based material layer.

[0101] In some embodiments, the method may further include assembling a supercapacitor using electrodes 100a / 100b / 100c / 100d / 100e / 100f / 100g, electrolyte 40, and optionally separator 220.ExamplesActivating carbon

[0102] Carbon can be bought, synthesized, and chemically or physically activated in various ways. Typically, the activation process may add the required functional groups, which may subsequently improve the specific surface area up to 2000-4000 [m2 / g]. Some nonlimiting examples for activating different types carbons are given herein below.

[0103] MWCNTS:MWCNTs were activated using nitric acid (HNO3). The process involved the following steps:• Mixing: 1.5 grams of MWCNT s were combined with 50 milliliters of 69% HNO3 in a three-necked flask.• Heating and Condensation: The flask was equipped with a thermocouple to monitor temperature and a condenser connected to a water trap. This setup captured the NO2 gas released during the reaction. The mixture was then heated to 90°C and held for 5 hours.• Washing and Drying: After cooling, the mixture was filtered under vacuum using a Buchner funnel. The resulting activated carbon (AC) was repeatedly washed with deionized water (DDW) until the filtrate reached a neutral pH (achieved by adding KOH). Finally, the AC was dried overnight in an oven at 90°C.

[0104] High Surface Area Activated Carbon (HSAAC):A carbon activation process using nitric acid (HNO3) was applied to HSAAC carbon. This process, involved the following steps:• Preparation: 2.5 grams of HSAAC carbon were placed in a three-necked round-bottom flask equipped with a thermocouple, stirring bar, andcondenser. The condenser was connected to a water trap to capture the NO2 gas released during the reaction.• Activation: 50 milliliters of a dilute aqueous solution of HNO3 (0.5M) were added to the carbon. The mixture was then heated to 90°C and maintained at that temperature for 5 hours.• Washing and Drying: After cooling, the mixture was filtered under vacuum using a Buchner funnel. The resulting activated carbon (AC) was repeatedly washed with deionized water (DDW) until the filtrate reached a neutral pH (achieved by adding KOH). Finally, the AC was dried overnight in an oven at 90°C.

[0105] A similar process can be applied to other types of carbon, such as, MWCNTs and the like.Carbon particles characteristics

[0106] Various types of carbons were characterized. The carbons may be included in an electrode, and more specifically in the active carbon layer of the electrode according to some embodiments of the invention. The carbon particles’ size, shape, and morphology were characterized using HRSEM, STEM, and EDS.

[0107] Reference is now made to Figs. 4A, 4B, 4C, 4D, and 4F which are HRSEM images of carbon particles according to some embodiments of the invention. Fig. 4 A includes an image of activated carbon, Fig. 4B includes an image of MWCNT, Fig. 4C includes an image of BP (conductive carbon blackl), Fig. 4D includes an image of graphite powder, and Fig. 4E includes an image of SP (conductive carbon black2).

[0108] The average surface area was measured using BET or as provided by the origin provider. Tow activated carbons and two nonacativated carbons were measured. For the activated carbons, the HSAAC had an average surface area of 2500 [m2 / g] and the black pearls had average surface area of 1488 [m2 / g]. For the nonactivated carbons, the graphite had average surface area of 96 [m2 / g], and the MWCNT had average surface area of 228 [m2 / g]. As clearly shown, the activated carbon has at least one order of magnitude larger average surface area.

[0109] Reference is now made to Figs. 5A, 5B and 5C which are graphs showing pore size distribution for nonactivated and activated carbon. In the graphs the cumulative pore volume in [cm2 / nm / g] was plotted as a function of the pore width in [nm]. The data forgraphs of Figs. 5A, 5B and 5C was calculated from BET measurements. Fig. 5A includes pore size distribution for nonactivated MWCNT, Fig. 5B includes pore size distribution for nonactivated graphite, and Fig. 5C includes pore size distribution for activated black pearls. The calculate average cumulative pore volume for each type of carbon result in MWCNT has average cumulative pore volume of 0.067 [cm2 / nm / g], the graphite has average cumulative pore volume of 0.0094 [cm2 / nm / g], and the activated black pearls has average cumulative pore volume of 0.0.35 [cm2 / nm / g].As shown the average cumulative pore volume of the activated carbon is at least one order of magnitude larger than the average cumulative pore volume of the nonactivated carbon.

[0110] Reference is now made to Figs. 5D, 5E and 5C which are graphs of adsorption and desorption isotherms of various nonactivated and activated carbon according to some embodiments of the invention. The data for graphs of Figs. 5D, 5E and 5C was calculated from BET measurements. In the graphs the volume adsorption (marked with a black triangles) and volume desorption (marked with a grey circles) in [cm2 / g] were plotted as a function of the relative pressure (P / Po). Fig. 5D includes volume adsorption and volume desorption for nonactivated MWCNT, Fig. 5E includes volume adsorption and volume desorption for nonactivated graphite, and Fig. 5F includes volume adsorption and volume desorption for activated black pearls. The adsorption and desorption behavior of all carbons were quite similar. Calculating the average adsorption for each type of carbon result in the MWCNT had an average adsorption of 7.5 [cm2 / g], the graphite had an average adsorption of 1.9 [cm2 / g], and the activate black pearl had average adsorption of 14.7 [cm2 / g]. As shown the activated carbon has at least twice the adsorption capacity in comparison to the nonactivated carbon.

[0111] Reference is now made to Fig. 6 which includes graphs of FTIR spectroscopy of various carbons according to some embodiments of the invention. Small amounts of dry carbons were crushed into powder form and tested. The spectra were recorded from 4500 to 250 cm From Fig. 6, one can determine the following functional groups: in the area of 3500 cm1,a minor OH stretching can be seen, 2980 cm1is a C-H asymmetric stretching, 2900-2000 cm'1is a C-H stretching of aliphatic CH CH3 groups, 1500 cm'1can be related to C=C stretch band / C-H asymmetric bending or to COOH group, this peak does not show at BP carbon. Next, a C-0 asymmetric stretching can be detected at 1250 cm', and C-0 bonds of the carboxylic acid group can be found at 1045 cm1; a C-0 stretching can also bedetected at 1100 cm1, and 1050 cm’1,which is usually referred to acidic C-0 bond. Also, a C-H stretch can be found at 1045 cm1, and a minor peak can be seen at 900 cm1.Slurry / ink preparation

[0112] At least one type of activated carbon was used together with at least one other type of carbon for preparing the active carbon layer in the electrode. The different types of carbons were mixed with a solvent and a binder prior to the application of the active carbon layer. Some nonlimiting examples for the preparation of slurry or ink are given herein below.

[0113] Method 1 -Slurry preparation for the applicator technique:

[0114] The slurry may consist of a carbon mixture, a binder, and a vaporizable solvent. To prepare the slurry for electrode coating, Activated Carbon (AC) at a ratio of 75- 90 wt.%, was combined with a binder such as Poly vinylidene fluoride (PVDF) at 1-5 wt.% and a vaporizable solvent such as N-Methyl-2-pyrrolidone (NMP). The ingredients were meticulously mixed by a mortar and paster / mechanical mixing to ensure homogeneity and uniform distribution of components throughout the slurry. The slurry preparation is a crucial step as it directly impacts the quality and performance of the electrode.

[0115] The carbon mixture may contain Activated Carbon (AC), Black carbons such as SuperP®, BLACK PEARLS®, VULCAN®, HSAAC, MWCNT, graphite, and graphene. The weight percentage of the carbon was between 75-90 wt.%. The activated carbon mass was in the range of 350-1500 mg. The different binder types utilized were selected from, Polyvinylidene fluoride (PVDF), Nafion®, or Carboxymethyl cellulose (CMC). The various vaporizable solvents used for the coating process may be N-Methyl-2-pyrrolidone (NMP), Dimethylformamide (DMF), or water.

[0116] The slurry was applied on applied directly on the conductive substrate using a applicator.

[0117] The outcome was a layer having mass loading of between 0.1 mg / cm2to 120.0 mg / cm2. Some possible combinations of carbons and binders are described in Table 1 and Table 2. All the experiments were carried out at room temperature 25 °C.

[0118] Table 1: various AC combinations for slurry preparation with PVDF andNMP

[0119] Table 2: various AC combinations for slurry preparation with CMC and water

[0120] Method 2- Ink preparation for air-brush / spray technique:

[0121] To prepare the slurry for electrode coating, the Activated Carbon (AC) mixture was mixed with a binder such as 5wt% Nafion®, in various ratios. The mixture was dispersed in 10-30ml of vaporizable solvent and sonicated for 2 minutes to ensure homogeneity and uniform distribution of components throughout the slurry.

[0122] The carbon mixture contained activated carbon (AC) -Black carbons such as SuperP®, BLACK PEARLS®, VULCAN®, HSAAC, MWCNT, graphite, and graphene. The weight percentage of the carbon is between 75-90 wt%. The activated carbon mass is in the range of 350-1500 mg. The different binder types utilized in device fabrication are- Polyvinylidene fluoride (PVDF), Nafion®, or Carboxymethyl cellulose (CMC). The various vaporizable solvents used for the coating process may be N-Methyl-2-pyrrolidone (NMP), Dimethylformamide (DMF), Metal-Nanoparticle solution, or water.

[0123] All the various mixture types are disclosed in Table 3. The mass loading of the layer was between 0.1 mg / cm2to 120.0 mg / cm2.

[0124] Table 3: various AC combinations for slurry preparation for spray technique.*The binder weight parentage calculated out of the total carbon wight (for example the total mix mass for device 3 is 100% AC+20%PVDF=l 20%)

[0125] Devices 10-13 of table 3 were prepared in a layer-by-layer method. In this case the first layer was prepared following the above-mentioned protocol. Shortly a mixture of 80% of HS AAC was mixed with 20% of PVDF and applied to the current collector by spray technique and dried on a hot plate. Following the first layer, a second layer was applied by spray on top of the first. The second layer consisted of 80% HSAAC and 20% Nafion. In both layers the solvent used was silver nanoparticles (Ag-NPs) solution, which was prepared in advance in our lab. It is also should be mentioned that any aqueous metal nanoparticle solution can be used instead of water.

[0126] The tested solutions for the active layers (e.g., layers 30) were made from the following metals: Ag, Au, Cu, Co, Pt, and more.Metal nanostructure synthesis for the active layer.

[0127] The metal nanostructures solution was prepared according to a slightly modified Creighton’s procedure. A cold aqueous solution containing NaBH4 (30 mL, 2.0 mM) was added under vigorous stirring to an aqueous solution of metal cation / complex solutions (10 mL, 1.0 mM of metal ion). The M-NP solutions prepared were at pH 9.0 (± 0.2). It should be emphasized that all of the M°-NPs were prepared without any stabilizing agent and synthesized in a close proximity time to the electrode layer fabrication.Electrode preparation

[0128] Method 1- applicator technique

[0129] After the slurry preparation, the film was coated using a 250-1000 micrometer film applicator. The applicator ensures precise thickness and uniformity of the coated electrode. The slurry was deposited on the conductive substrate (e.g., the current collector) and applied by the applicator. The coated electrode is then subjected to drying in an oven maintained at 70-95 degrees Celsius for 1-4 hours. This drying process is essential for removing solvents and achieving the desired electrode morphology and stability.

[0130] Method 2- spray technique

[0131] After the slurry preparation, the conductive substrate was coated with a layer of the slurry using a spray-coater pen / brush. The layer was prepared by spraying small amounts of slurry over the substrate and drying it on the hot plate at 100 °C under an ambient atmosphere. These steps are repeated until all the slurry is homogeneously dispersed on the conducting substrate (also known as a current collector).Supercapacitor assembly

[0132] Preparing a pouch cell device may involve several critical steps to ensure its proper assembly and functionality. In step 1, electrodes are cut into 2 cm x 5 cm dimensions, maintaining precision to facilitate optimal performance. In step 2, a 3 cm x 6 cm separator, such as polypropylene (PP), is then carefully placed between the electrodes to prevent short circuits and facilitate ion transport within the cell. In step 3, a solution of electrolyte in various concentrations 0.1 -IM, such as tetra-n-butylammonium hexafluorophosphate (TBAPFe) electrolyte, is employed to enhance ion conductivity within the cell. The electrolyte enables charge transfer between the electrodes during supercapacitor operation.

[0133] Once the components are in place, the assembly process proceeds with the packing of the cell using a pouch explicitly designed for this purpose. The pouch is a containment vessel, securely holding the electrode-separator-electrode stack and electrolyte solution. To ensure the integrity and longevity of the cell, the pouch is sealed using a vacuum sealer, which removes air and seals the pouch tightly. This step is vital for preventing leakage of electrolytes and maintaining a stable internal environment within the cell.

[0134] The electrolyte may include one of an aqueous solution or organic solutions (mixed in acetonitrile) of KOH, NaOH, NaCl, KC1, Na2SO3, Na2SO4, NaC104, K2SO3, TEABF4, LiC104, LiCl, LiOH, Li2SO4, TEABF4, TBABF4, TBAPF6and the like. The sizes of the electrodes may vary in accordance to the device diameters, that also may change. The following device sizes may be utilized- 2x5cm, 4x5cm, 5x10cm, lOxlOcm. It is alsoimportant to mention that the device may be a one-sided device or a multi-electrode stacking device. The multi-electrode device may contain 5, 7, 11, or 16 electrodes. For multielectrode devices double- sided electrodes have to be prepared. Following step 2 of electrode preparation the coated one-sided electrode weight was taken, and the non-coated side were covered by a carbon mixture following the same methodology to create a double sided electrode (e.g., electrodes lOOe, lOOf, and 100g). The multi-electrode devices are prepared with two one-sided electrodes, the coated sides facing each other and a separator in between, then the double-sided electrodes were added in the middle creating a sandwich structure with a separator between each and every electrode, as illustrated in Fig. 2C.Additional electrode type

[0135] Another type of layer was also tested for supercapacitor electrodes. In this case, an active material such as PtPdSn nanoparticles was incorporated in the active carbon layer of the electrode; Fig. 7 shows the SEM, STEM and EDS analysis of these materials.Carbon layer characterization

[0136] Various carbon combinations were applied on the conductive substrate, as disclosed herein above. The final multilayered structure included aluminum foil as the conductive substrate 10, on which layers 15, 20, and 30 were applied. Fig. 8 shows binocular light microscopy images of electrodes having: a) and b) substrate 10, conductive layer 15, and active carbon layer 20; and c) and d) substrate 10, conductive layer 15, active carbon layer 20, and active layer 30.Electrochemical testing

[0137] Electrochemical impedance spectroscopy (EIS) is a vital tool for studying supercapacitor electrodes. It provides insights into various aspects including electrical conductivity, ionic diffusion, how charge transfers occur, and the origin of the capacitance. EIS measurements are performed using a Nyquist plot (graph of Z' vs. -Z") across a wide range of frequencies, typically from 0.01 Hz to 10000 Hz. This plot usually has two distinct sections: a semicircle at high frequencies and a straight line at low frequencies. These features reveal the electrochemical properties of the supercapacitor device. The software ZS impWin was utilized for EIS analysis and adaptation of the experimental measurement to an actual exciting electrical circuit.I. Cyclic voltammetry ( CV)

[0138] The supercapacitor's performance can be determined by considering three key factors: specific capacitance, energy density, and power density. These values are calculated using the following equations:

[0139] The electrode materials specific capacitance is calculated via a current-voltage (CV) analysis, where C is specific capacitance, I is the voltametric current, m is the device mass (g), AV is the potential window (V), and v is the scan rate (mVs-1).II. Galvanostatic Charge-discharge (GCD)

[0140] Galvanostatic charge-discharge (GCD) was performed within a potential window and at different current densities suitable to each electrode.Further, the energy and power densities are calculated by-IAVP — - 7) m ’

[0141] where the I, AV, At, and m, are the current, potential window, discharging time, and mass of the device, respectively. Further manipulation of the previously mentioned equations leads to another way to calculate the power density and the energy density, using equations (1) and (3) discussed herein above.Analyzing the results of Method 1 - the applicator technique

[0142] Reference is now made to Figs. 9A which is a CV in a potential range of 0-2.8V and 9B which is GCD plots in current density of ±20-850 mA, of carbon-based EDLC device (503mg) with carbon mixture consisting of AC 75 wt.%, MWCNT 7.5 wt.%, graphite powder 7.5 wt.%, with PVDF and NMP, according to some embodiments of the invention.

[0143] Further results for other carbon mixtures, with PVDF binder, and a NMP solvent, are shown in Table 4.

[0144] Table 4: Devices prepared with PVDF and NMP

[0145] Reference is now made to Figs. 10A, 10B, and IOC which are EIS, CV, and GCD graphs for carbon-based electrodes with CMC and water as a solvent, according to some embodiments of the invention. Fig. 10A shows the EIS Nyquist plot, Fig. 10B shows the CV in a potential range of 0-4 V, and Fig. 10C shows the GCD plot in current density of ±10- 400 mA, of Carbon-based EDLC device (286mg) with carbon mixture consisting of AC 80 wt%, MWCNT 7.5 wt%, graphite powder 7.5 wt%, with CMC and water.

[0146] Further results for other carbon-based electrodes with CMC and water as a solvent are presented in Table 5.

[0147] Table 5: Devices prepared with CMC and WaterAnalyzing the results of Method 2 - the spray technique

[0148] Reference is now made to Figs. 11A, 11B which are CV in a potential range of 0-3.5V, and GCD plot in current density of ±10-400 mA, of Carbon-based EDLC device (Device 18-280mg) with carbon mixture consisting of 75 wt.% AC, 25 wt.% MWCNT, with PVDF binder and DMF solvent, according to some embodiments of the invention.

[0149] The results for devices manufactured using the spry technique are summarized in Table 6.

[0150] Therefore, one may conclude that the surface area of the carbon mixture plays a significant role in energy density and power density results. The best carbon was found to be the activated carbon TOB with a surface area of 2000- 2500 (m2 / gr). The additives to this carbon were MWCNT and graphite powder, these two materials provided high conductivity to the carbon-based electrodes. Furthermore, binders such as PVDF and Nafion, which are commonly used in the electrode fabrication industry, are not environmentally friendly and therefore, a considerable amount of work was invested in finding a better replacement to these binders. Based on this reasoning, a material such as CMC binder, which is a green chemical, was chosen. The chosen vapourable solvents appear to have minimal impact on the carbon-based electrode layer because most of the solvent evaporates during the heating in the electrode fabrication step. It was also found that the device parameters can beimproved by turning the single devices to a multi- stack devices, the multiple layers provide higher energy density and power density.

[0151] Another experiment was conducted on a full capacitor cell, with various carbon types and nanostructures with CMC and water. At least one electrode included a layer 20 comprising an activated carbon and different types of nanostructured carbon, SWCNT, MWCNT and carbons nanospheres. Table 5 summarizes the influence of the type of nanostructured carbon, the surface area of the nanostructured carbon (measured by BET) on the capacitance and the energy density of the cell.

[0152] Table 7- The effect of different nanostructures on the electrochemical behavior of the electrode

[0153] As clearly shown in table 7, SWCNT (also known as CNT) is less suitable since it was not possible to form a layer (although with a different preparation method a layer may be formed). Adding black carbon spheres having a higher surface area resulted in a better electrochemical behavior, with much higher Capacitance range and energy density, although the MWCNT gave sufficient performance.

[0154] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all formulas described herein are intended as examples only and other or different formulas may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time.

[0155] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0156] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

CLAIMS1. An electrode comprising: a multilayered structure comprising: a conductive substrate; an active carbon-based layer comprising a mixture of: at least a first type of activated carbon, at least one nanostructured carbon, and a binder, wherein the first type of activated carbon comprises carbon particles characterized by an average surface area of between 2000 to 4000 [m2 / g] and the nanostructured carbon characterized by having at least one dimension between 5 to 100 nm and an average surface area of between 200 to 2500 [m2 / g].

2. The electrode of claim 1, further comprising a second type of activated carbon.

3. The electrode of claim 2, wherein the second activated carbon differs from the first type of activated carbon in at least one of, adsorption capacity, surface area, pore size, desorption capacity, and pore volume.

4. The electrode of any one of claims 1 to 3, wherein the mixture comprises between 30 to 90 wt.% of the first type of activated carbon.

5. The electrode of any one of claims 1 to 4, wherein the active carbon-based layer has an average mass loading of between 4 to 20 mg / cm2.

6. The electrode of any one of claims 1 to 5, wherein the nano structured carbon comprises at least one of: double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), and carbon nanospheres.

7. The electrode of any one of claims 1 to 6, wherein the mixture comprises two types of nanostructured carbon, a first type of carbon at an amount of between 4 to 15 wt.% and a second type of carbon at an amount of between 2.5 to 20 wt.%.

8. The electrode of any one of claims 1 to 6, wherein the amount of the at least one nanostructured type of carbon in the mixture is between 5 to 32 wt.%.

9. The electrode of any one of claims 1 to 8, wherein the active carbon-based layer further comprising conductive particles selected from: metal oxide particle, metal particles, metal chalcogenides, bi-metal particles, tri-metal particles, and any combination thereof.

10. The electrode of any one of claims 1 to 9, wherein the binder is a polymeric binder.

11. The electrode of claim 10, wherein the polymeric binder comprises at least one of: sulfonated tetrafluoroethylene based fluoropolymer-copolymer (Nafion), Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), Carboxymethyl cellulose (CMC), epoxy resin, acrylic resin, Polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinylidene fluoride -hexafluoro propylene) (PVDF-HFP), and any copolymer thereof.

12. The electrode of any one of claims 1 to 11, wherein the conductive substrate comprises, at least one of, one or more metals, conductive composite, conductive ceramics, and carbon cloth, carbon fiber, carbon paper, and metal foam.

13. The electrode of any one of claims 1 to 12, wherein the active carbon-based layer comprises a first surface in contact with the conductive substrate and a second surface; and wherein the multilayered structure further comprises an active material layer attached to the second surface.

14. The electrode of claim 13, wherein the active material comprises nanostructures of at least one of: a metal-chalcogen compound, metal- oxides, PtPdSn, Co, Pt, Au, Ag, Ni, Mg, V, and Mn.

15. The electrode of claim 14, wherein the metal-chalcogen compound comprises a metal comprising at least one of Ag, Au, Co, Ni, Mn, Cu, V, Ni, Fe, Mn, Sn, and any combination thereof, and at least one of the following chalcogens Te, Se, and S.

16. The electrode of claim 15, wherein the mass loading of the active material layer is between 0.1 and 4 mg / cm217. The electrode of any one of claims 1 to 16, wherein the multilayered structure further comprises a conductive layer located between the conductive substrate and the carbon-based layer.

18. The electrode of claim 17, wherein the mass loading of the conductive layer is between 0.1 to 1 mg / cm219. The electrode of claim 18, wherein the conductive layer comprises a mixture of between 70 to 90 wt.% carbon particles, between 5 to 20 wt.% conductive particles, and between 2 to 15 wt.% of the binder.

20. A supercapacitor, comprising: a first electrode; a separator comprising an electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises: a conductive substrate; and an active carbon-based layer comprising a mixture of: a first type of activated carbon, at least one nanostructured carbon, and a binder, wherein the first type of activated carbon comprises carbon particles characterized by an average surface area of between 2000 to 4000 [m2 / g] and the nanostructured carbon characterized by having at least one dimension between 5 to 100 nm and an average surface area of between 200 to 2500 [m2 / g].

21. The supercapacitor of claim 20, wherein the active carbon-based layer further comprises a second type of activated carbon.

22. The supercapacitor of claim 21, wherein the second type of activated carbon differs from the first type of activated carbon in at least one of, adsorption capacity, surface area, pore size, desorption capacity, and pore volume.

23. The supercapacitor of any one of claims 20 to 22, wherein the mixture comprises between 30 to 90 wt.% of the at least one first type of activated carbon.

24. The supercapacitor of any one of claims 20 to 23, wherein the active carbon-based layer has an average mass loading of 4 to 20 mg / cm225. The supercapacitor of any one of claims 20 to 24, wherein the nano structured carbon comprises at least one of: double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), and carbon nanospheres.

26. The supercapacitor of any one of claims 20 to 25, wherein the mixture comprises two types of other carbon, a first type of carbon at an amount of between 4 to 15 wt.% and a second type of carbon at an amount of between 2.5 to 20 wt.%.

27. The supercapacitor of any one of claims 20 to 26, wherein the amount of the at least one other type of carbon in the mixture is between 5 to 32 wt.%.

28. The supercapacitor of any one of claims 20 to 27, wherein the active carbon-based layer further comprising conductive particles selected from: metal oxide particle, metal particles metal chalcogenides, bi-metal particles, tri-metal particles, and any combination thereof.

29. The supercapacitor of any one of claims 20 to 28, wherein the binder is a polymeric binder.

30. The supercapacitor of claim 29, wherein the polymeric binder comprises at least one of: sulfonated tetrafluoroethylene based fluoropolymer-copolymer (Nafion), Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), Carboxymethyl cellulose (CMC), epoxy resin, acrylic resin, Polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), poly(vinylidene fluoride -hexafluoro propylene) (PVDF-HFP), and any copolymer thereof.

31. The supercapacitor of any one of claims 20 to 30, wherein the conductive substrate comprises, at least one of, one or more metals, conductive composite, conductive ceramics, and carbon cloth, carbon fiber, carbon paper, and, metal foam.

32. The supercapacitor of any one of claims 20 to 31, wherein the active carbon-based layer comprises a first surface in contact with the conductivesubstrate and a second surface; and wherein the multilayered structure further comprises an active material layer attached to the second surface.

33. The supercapacitor of claim 32, wherein the mass loading of the active material layer is between 0.1 and 4 mg / cm234. The supercapacitor of any one of claims 20 to 33, wherein the multilayered structure further comprises a conductive layer located between the conductive substrate and the carbon-based layer.

35. A method of making an electrode, comprising: providing a conductive substrate; and depositing on the conductive substrate a carbon-based layer comprising a mixture of: a first type of activated carbon, at least one nanostructured carbon, a solvent and a binder, wherein the at least one first type of activated carbon comprises carbon particles characterized by an average surface area of between 2000 to 4000 [m2 / g] and the nanostructured carbon characterized by having at least one dimension between 5 to 100 nm, and an average surface area of between 200 to 2000 [m2 / g],36. The method of claim 35, wherein the solvent is selected from ethanol, isopropanol, acetone, water, and any combination thereof.

37. The method of claim 35 or claim 36, further comprising: depositing a conductive layer between the conductive substrate and the carbonbased layer.

38. The method of any one of claims 35 to 37, further comprising: depositing an active material layer on top of the carbon-based layer.

39. The method of claim 38, wherein the active material comprises nanostructures of at least one of: a metal-chalcogen compound, metal- oxides, PtPdSn, Co, Pt, Au, Ag, Ni, Mg, V, and Mn.

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