Supercapacitor comprising nanostructure of a metal-chalcogen compound

Abstract

Symmetric and asymmetric supercapacitors are disclosed. The symmetric supercapacitor comprises: a first electrode; an electrolyte; and a second electrode. The first and second electrodes comprise carbon-based material and nanostructure of metal-chalcogen compound, wherein the metal is selected from Cu, Va, Ni, Fe, Ag, Co, Mn, Sn, and any combination thereof, and the chalcogen is selected from Te, Se, and S. The asymmetric supercapacitor comprises: a substrate; a first electrode comprising a first carbon-based material and a first nanostructure of a metal-chalcogen compound, wherein the metal is selected from Cu and Sn, and the chalcogen is selected from Te, Se, and S; an electrolyte; and a second electrode comprising a second carbon-based material.

Description

[0001] SUPERCAPACITOR COMPRISING NANOSTRUCTURE OF A METAL- CHALCOGEN COMPOUND

[0002] CROSS REFRENCE TO RELATED APPLICATIONS

[0003]

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 456,820, filed 04 April 2023, the contents of which are all incorporated herein by reference in their entirety.

[0004] FIELD OF THE INVENTION

[0005]

[0002] The present invention relates generally to supercapacitors. More specifically, the present invention relates to supercapacitors comprising nanostructure of a metal-chalcogen compounds.

[0006] BACKGROUND OF THE INVENTION

[0007]

[0003] 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.

[0008]

[0004] Several types of supercapacitors are known and in use. Electrostatic double-layer capacitors (EDLCs), Electrochemical pseudo-capacitors, and Hybrid capacitors are the most common.

[0009]

[0005] 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.

[0010]

[0006] Pseudo-capacitors are supercapacitors where charges are stored through the electrosorption, redox reaction or intercalation process. In faradaic charge storage mechanism, 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.

[0011]

[0007] 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 pseudocapacitor 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 pseudo-capacitor) 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.

[0012]

[0008] 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 energy density 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.

[0009] Therefore, the aim of the claimed invention is to provide an improved hybrid- supercapacitor suitable for any use for example, electric vehicles or any other electrically powered units.

[0013] SUMMARY OF THE INVENTION

[0014]

[0010] Some aspects of the invention may be directed to a supercapacitor. The supercapacitor may include a first electrode comprising a first carbon-based material and a first nanostructure of a metal-chalcogen compound, wherein the metal includes Cu, Va, Ni, Fe, Mn, Sn, and any combination thereof, and the chalcogen includes Te, Se, and S; an electrolyte; and a second electrode selected from:

[0015] (i) a second carbon-based material; and

[0016] (ii) the second carbon-based material and a second nanostructure of a metal- chalcogen compound, wherein the metal includes Cu, Va, Ni, Fe, Mn, Sn, and any combination thereof, and the chalcogen includes Te, Se, and S.

[0017] [Oil] Some additional aspects of the invention may be directed to a symmetric supercapacitor, comprising: a first electrode; an electrolyte; and a second electrode. In some embodiments, the first and second electrodes comprise carbon-based material and nanostructure of metal-chalcogen compound, wherein the metal includes Cu, Va, Ni, Co, Ag, Fe, Mn, Sn and any combination thereof, and the chalcogen is includes Te, Se, and S.

[0018]

[0012] In some embodiments, each one of the first and second electrodes comprises: a first layer comprising the carbon-based material and a second layer comprising the nanostructure of the metal-chalcogen compound. In some embodiments, a mass loading of the first layer is between 0.1 mg / cm2to 20.0 mg / cm2and a mass loading of the second layer may be between 0.1 mg / cm2to 20.0 mg / cm2.

[0019]

[0013] In some embodiments, each one of the first and second electrodes comprises: a composite material comprising a mixture of the carbon-based material and the nanostructure of the metal-chalcogen compound. In some embodiments, the metal-chalcogen compound has morphologies, includes, nanoparticle, nanospheres, nanotube, nanosheets, nanowires, nanoflower, etc. In some embodiments, the weight ratio between the carbon-based material and the nanostructure of metal-chalcogen mixture compound is between 1:1 to 1:4.

[0020]

[0014] In some embodiments, the carbon-based material may include at least one of single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi- walled carbon nanotubes (MWCNT), carbon nano-pearl powder, functionalized carbon, carbon black, graphite powder, allotropes of graphene, and activated black carbons.

[0021]

[0015] In some embodiments, the first layer comprising oriented SWCNT, DWCNT and MWCNT, may be parallel to a surface of the second layer.

[0022]

[0016] In some embodiments, the electrolyte may include, KOH, NaOH, NaCl, KC1, Na2SO3, Na2SO4, NaC104, K2SO3, TEABF4, TBABF4, TBAPF6, TEAPF6, LiC104, LiCl, LiOH, Li2SO4. In some embodiments, the electrolyte may be an aqueous or organic gel electrolyte. In some embodiments, the aqueous or organic gel may include at least one of polyvinyl alcohol (PVA), n-methyl-2-pyrrolidone (NMP), cellulose powder, acetonitrile, carboxymethyl cellulose (CMC), and sulfonated tetrafluoroethylene based fluoropolymer- copolymer (Nafion).

[0023]

[0017] In some embodiments, the electrolyte may be an aqueous solution and the supercapacitor further comprises a separator. In some embodiments, each one of the first and second electrodes further may include an additive. In some embodiments, the additive may be Poly vinylidene fluoride (PVDF).

[0024]

[0018] In some embodiments, the supercapacitor may further include two current collectors, each attached to a surface of either the first or the second electrode not facing the electrolyte.

[0025]

[0019] In some embodiments, the supercapacitor may further include at least one conductive layer attached to at least one of the current collectors. In some embodiments, the at least one conductive layer may include mixture of between 70 to 90 wt.% graphite, 20 to 5 wt.% MWCNT and a binder.

[0026]

[0020] Some additional aspects of the invention may be directed to an additional asymmetric supercapacitor, that may include: a first electrode comprising a first carbonbased material and a first nanostructure of a metal-chalcogen compound, wherein the metal may include at least one of Cu, Va, Ni, Co, Ag, Fe, Mn, Sn, and any combination thereof and the chalcogen may include Te, Se, and S; an electrolyte; and a second electrode that may include a second carbon-based material.

[0027]

[0021] In some embodiments, the carbon-based materials may include at least one of, single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multiwalled carbon nanotubes (MWCNT), carbon nano-pearl powder, allotropes of graphene, activated carbon, carbon black, graphite powder, and activated black carbons, etc. In some embodiments, the first electrode may include: a first layer that may include the carbon-based material and a second layer comprising the nanostructure of the metal-chalcogen compound. In some embodiments, a mass loading of the first layer may be between 0.1 mg / cm2to 20.0 mg / cm2and a mass loading of the second layer may be between 0.1 mg / cm2to 20.0 mg / cm2.

[0022] In some embodiments, the first electrode may include: a composite material that may include a mixture of the carbon-based material and the nanostructure of the metal- chalcogen compound. In some embodiments, the metal-chalcogen compound has morphologies, includes, nanoparticle, nanospheres, nanotube, nanosheets, nanowires and nanoflower. In some embodiments, the weight ratio between the carbon-based material and the nanostructure of metal-chalcogen mixture compound may be between 1:1 to 1:4.

[0028]

[0023] In some embodiments, the electrolyte may include at least one of, KOH, NaOH, NaCl, KC1, Na2SO3, Na2SO4, NaClO4, K2SO3, TEABF4, , TBABF4, TBAPF6, TEAPF6, LiClO4, LiCl, LiOH, Li2SO4. In some embodiments, the electrolyte is an aqueous or organic gel electrolyte. In some embodiments, the aqueous or organic gel may include at least one of polyvinyl alcohol (PVA), n-methyl-2-pyrrolidone (NMP), cellulose powder, acetonitrile, carboxymethyl cellulose (CMC), and sulfonated tetrafluoroethylene based fluoropolymer- copolymer (Nafion). In some embodiments, the electrolyte may be an aqueous solution and the supercapacitor may further include a separator.

[0029]

[0024] In some embodiments, the first and second electrode may further include an additive. In some embodiments, the additive may be Poly vinylidene fluoride (PVDF), or carboxymethyl cellulose (CMC).

[0030]

[0025] In some embodiments, the supercapacitor may further include two current collectors, each attached to a surface of either the first or the second electrode not facing the electrolyte.

[0031]

[0026] In some embodiments, the supercapacitor may further include at least one conductive layer attached to at least one of the current collectors. In some embodiments, the at least one conductive layer includes mixture of between 70 to 90 wt.% graphite, 20 to 5 wt.% MWCNT and a binder.

[0032]

[0027] In some embodiments, the supercapacitor may further include a first current collector; a first conductive layer, attached from one side to the first current collectorand to the first carbon based material; a second current collector; and a second conductive layer, attached from one side to the second current collector, and to the second carbon based material.

[0033]

[0028] In some embodiments, the first and second conductive layers may include a mixture of between 70 to 90 wt.% graphite, between 20 to 5 wt.% MWCNT and a binder.

[0029] Some additional aspects of the invention may be directed to a method of making an electrode for a supercapacitor, the method may include synthesizing nanostructures of metal-chalcogen compound, wherein the metal may be selected from Cu, Ag, Ni, Co, and Sn and any combination thereof, and the chalcogen may be selected from Te, Se, and S; forming a first layer that may include carbon-based material; and depositing a second layer that may include the nanostructures of metal-chalcogen compound on one side of the first layer.

[0034]

[0030] In some embodiments, the carbon-based material may include at least one of single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multiwalled carbon nanotubes (MWCNT), carbon nano-pearl powder, functionalized carbon, carbon black, Graphite powder, allotropes of graphene, and activated black carbons.

[0035]

[0031] In some embodiments, the method may further include depositing the electrode on a current collector. In some embodiments, the method may further include depositing a conductive layer on the current collector prior to depositing the electrode.

[0036]

[0032] In some embodiments, the method may further include assembling a supercapacitor using a first electrode according to any one of the embodiments disclosed herein, an electrolyte and a second electrode, selected from;

[0037] (i) a carbon-based material deposited on a current collector; and

[0038] (ii) an electrode according to any one of the embodiments disclosed herein.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040]

[0033] 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:

[0041]

[0034] Fig. 1A is an illustration of a symmetric supercapacitor according to some embodiments of the invention;

[0035] Fig. IB is an illustration of an asymmetric supercapacitor according to some embodiments of the invention;

[0042]

[0036] Fig. 2 is a flowchart of a method of making an electrode for a supercapacitor according to some embodiments of the invention;

[0043]

[0037] Fig. 3 is an X-ray diffraction spectrum for 2D SnSe nanosheets according to some embodiments of the invention;

[0044]

[0038] Fig. 4 shows SEM analysis confirming the surface morphology of the 2D SnSe nanosheets according to some embodiments of the invention;

[0045]

[0039] Fig. 5 is an illustration of a synthesis process of CuSe nanocrystals according to some embodiments of the invention;

[0046]

[0040] Fig. 6 shows a SEM image of CuSe according to some embodiments of the invention;

[0047]

[0041] Fig. 7 A show XRD patterns of CuSe according to some embodiments of the invention;

[0048]

[0042] Fig. 7B shows Transmission Electron Microscopy (TEM3. High-resolution (HR) TEM, Selected Area Electron Diffraction (SAED), and Energy Dispersive X-ray Spectrum (EDS) of CuSe according to some embodiments of the invention;

[0049]

[0043] Fig. 7C shows nitrogen adsorption / desorption isotherms and Pore size distributions of the CuSe nanosheets and BJH pore-size distribution curve (inset) according to some embodiments of the invention;

[0050]

[0044] Fig. 8A shows XRD pattern of SnS according to some embodiments of the invention;

[0051]

[0045] Fig. 8B shows SEM images of SnS nanostructure according to some embodiments of the invention;

[0052]

[0046] Fig. 9 shows CV curves at different electrolytes at 0.5 M concentration and the corresponding Capacitance graph according to some embodiments of the invention;

[0053]

[0047] Fig. 10 shows CV curves at different concentration of NaOH and the corresponding Capacitance graph according to some embodiments of the invention;

[0054]

[0048] Fig. 11 shows CV curves at different CuSe mass loading in 2.5 M NaOH @ 100 mV / s and the corresponding Capacitance graph according to some embodiments of the invention;

[0049] Fig. 12 shows the electrochemical characterization of the 0.45 mg CuSe nanosheets on SS substrate (a, b) CV curves of the CuSe nanosheets at different scanning rates and their corresponding capacitance (in F / g and mF / cm2), (c, d) Galvanostatic Chargedischarge (GCD) curves at different current densities and their corresponding capacitance (in F / g and mF / cm2) according to some embodiments of the invention;

[0055]

[0050] Fig. 13 shows the electrochemical impedance spectroscopy analysis of CuSe nanosheet electrode (a) Nyquist plot, (b) fitted equivalent circuit, (c) Bode phase plots and (d) capacitance Vs frequency according to some embodiments of the invention;

[0056]

[0051] Fig. 14 shows electrochemical stability of CuSe nanosheets electrode through 3500 repetitive CV cycles at 100 mV / s according to some embodiments of the invention; and

[0057]

[0052] Fig. 15 shows Electron Microscope Images of HR-SEM: (a) Low magnification of CuSe on a carbon tape surface (b) High magnification of CuSe on a grid surface (c) Low magnification of CuSnSe on a carbon tape surface (d) High magnification of CuSnSe on a grid surface (e) Low magnification of SnSe on a carbon tape surface (f) High magnification of SnSe on a grid surface, according to some embodiments of the invention.

[0058]

[0053] 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 some of 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.

[0059] DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0060]

[0054] 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.

[0061]

[0055] Some aspects of the invention are directed to hybrid supercapacitors comprising nanostructure of a metal-chalcogen compound. The hybrid supercapacitors may be symmetric supercapacitors or asymmetric supercapacitors. The metal-chalcogen compound may be provided as a nanolayer, nanoparticle, nanospheres, nanotube, nanosheets, nanowires and nanoflower and the like. The metal-chalcogen compound may be included in the electrodes of the supercapacitor together with a carbon-based material.

[0062]

[0056] 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. 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, nanowires having a width of at most 100 nm, and nanoflower having an average diameter of at most 100 nm and the like.

[0063]

[0057] As used herein, a “chalcogen” may include elements selected from Te, Se and S.

[0064]

[0058] As used herein, a “metal” may include metallic elements selected from Cu, Va,

[0065] Ni, Fe, Sn, and the like.

[0066]

[0059] As used herein, a carbon-based material may include any carbon-based morphology, for example, carbon nanolayer, single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nano-pearl powder, graphite powder, allotropes of graphene, and activated black carbons, and the like.

[0067]

[0060] As used herein a “functionalized carbon-based material” 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.

[0068]

[0061] In some embodiments, the effective electrochemical performance of the supercapacitor is directly dependent on the selection of active electrode material and suitable electrolyte. The surface morphology, crystal structure, and thickness of the films / layers are the parameters for achieving efficient electrochemical performance.

[0069]

[0062] In some embodiments, the following aspects should be taken into consideration when fabricating an electrode for supercapacitor application:

[0070] • The electrode material may have large surface area, porosity, and conductivity to have superior electrochemical performance.

[0071] • The electrolyte may penetrate into porous surface of the electrode material.

[0072] • The use of good electrically conducting materials reduces resistance and allows for high power delivery. • Environmental-friendly and non-toxic electrode.

[0073] • Simple, low-cost, industry-scalable approach may be engaged to fabricate large area electrode.

[0074]

[0063] The energy density (E) and power density (P) of supercapacitor are calculated using equations (1) and (2)

[0075] E =1 / 2CV2, (1) p = V2 / 4R, (2)

[0076]

[0064] Where C is the DC capacitance, V is the voltage, and R is the resistance. According to this equation, embodiments of the invention focus on enhancing the energy density of supercapacitors by improving their capacitance and working voltage.

[0077]

[0065] 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.

[0078]

[0066] Reference is now made to Fig. 1A which is an illustration of a symmetric supercapacitor according to some embodiments of the invention. A supercapacitor 100 may include a first electrode 10A, a second electrode 10B, and an electrolyte 20. In a symmetric supercapacitor first electrode 10A and second electrode 10B have a substantially similar structure and forms a mirror symmetry from both sides of electrolyte 20, as illustrated.

[0079]

[0067] In some embodiments, each one of electrodes 10A and 10B may include carbonbased material 12 and nanostructure of metal-chalcogen compound 14, wherein the metal includes Cu, Va, Ni, Co, Ag, Fe, Mn, Sn and any combination thereof, and the chalcogen includes Te, Se, and S. For example, a carbon-based layer 12 may be attached to a metal- chalcogen nanolayer (or nanosheet) 14. For example, functionalized MWCNTs may be used to form carbon-based layer 12. In some embodiments, metal-chalcogen compound layer 14 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. (given from other metal-chalcogens).

[0068] In some embodiments, metal-chalcogen compound 14 has the following chemical formula MSnX, where M is selected from Cu, Ag, Co, Ni and the like and X is selected from Te, Se, and S.

[0080]

[0069] In some embodiments, a mass loading of layer 12 is between 0.1 mg / cm2to 20 mg / cm2, for example, 0.15 mg / cm2, 0.3 mg / cm2, 0.5 mg / cm2, 1 mg / cm2, 2 mg / cm2, 5 mg / cm2, 7 mg / cm2, 10 mg / cm2, 15 mg / cm2, 20 mg / cm2, and any value in between. In some embodiments, a mass loading of layer 14 is between 0.1 mg / cm2to 20.0 mg / cm2, for example, 0.1 mg / cm2, 0.3 mg / cm2, 0.5 mg / cm2, 1 mg / cm2, 2 mg / cm2, 5 mg / cm2, 7 mg / cm2, 10 mg / cm2, 15 mg / cm2, 20 mg / cm2, and any value in between.

[0081]

[0070] In some embodiments, the carbon-based material may be a functionalized carbonbased material, for example, functionalized SWCNT, DWCNT, MWCNT, carbon nanopearl powder, carbon black, graphite powder, allotropes of graphene, activated black carbons, and the like.

[0082]

[0071] In some embodiments, first layer 12 may include oriented SWCNT, DWCNT and MWCNT. In such case, the longitudinal axes of the SWCNTs, DWCNTs and MWCNTs are substantially parallel to the surface of second layer 14.

[0083]

[0072] In some embodiments, each one of first electrode 10A and second electrode 10B may comprise a composite material comprising a mixture of the carbon-based material and the nanostructure of the metal-chalcogen compound. For example, electrodes 10A and 10B may include a mixture of SnS nanoflower, and MWCNTs or carbon nano-pearl powder.

[0084]

[0073] In some embodiments, the weight ratio between the carbon-based material and the nanostructure of metal-chalcogen mixture is between 1:1 to 1:4, for example, 1:1.5, 1:2, 1:2.5, 1:3, 1:35, 1:14 and any value in between.

[0085]

[0074] In some embodiments, electrolyte 20 may be placed between electrodes 10A and 10B. For example, when electrodes 10A and 10B include metal-chalcogen compound layer 14, electrolyte 20 is located between layers 14, as illustrated.

[0086]

[0075] In some embodiments, when comprising the composite material, each one of first and second electrodes 10A and 10B may further comprise additives, such as, Poly vinylidene fluoride (PVDF) and the like.

[0087]

[0076] In some embodiments, electrolyte 20 may include an aqueous solution of, KOH, NaOH, NaCl, KC1, Na2SO3, Na2SO4, NaClO4, TBABF4, TBAPF6, TEAPF6, K2SO3, TEABF4, LiClO4, LiCl, LiOH, Li2SO4and the like. In such case, supercapacitor 100 may further include a separator (not shown). In some embodiments, the separator may be made from cellulose paper or gel polymer electrolyte membrane.

[0088]

[0077] In some embodiments, electrolyte 20 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, LiC104, LiCl, LiOH, Li2SO4and the like.

[0089]

[0078] In some embodiments, supercapacitor 100 may further include two current collectors 30, each attached to a surface of either first electrode 10A or second electrode 10B not facing electrolyte 20. Current collectors 30 may include any metallic sheet, such as, stainless steel foil / mcsh, copper foil, nickel foam / foil, Aluminum foil / mesh or carbon cloth / foam.

[0090]

[0079] Reference is now made to Fig. IB which is an illustration of an asymmetric supercapacitor according to some embodiments of the invention. An asymmetric supercapacitor 200 may include a first electrode 110, a second electrode 120, and an electrolyte 20. In an asymmetric supercapacitor first electrode 110 is different from second electrode 120 by at least one of the carbon-based materials and / or the nanostructure of a metal-chalcogen compound.

[0091]

[0080] Electrolyte 20 may be substantially the same as electrolyte 20 of supercapacitor 100. Supercapacitor 200 may further include current collectors 30 and which are substantially similar to current collectors 30 of supercapacitor 100.

[0092]

[0081] In some embodiments, first electrode 110 may include a first carbon-based material 112 and a first nanostructure of a metal-chalcogen compound 114. In such case, first electrode 110 may be the positive electrode.

[0093]

[0082] In some embodiments, second electrode 120 may include only second carbonbased material 122. In such case, second electrode 120 may be the negative electrode. In some embodiments, second electrode 120 may also include a second nanostructure of a metal-chalcogen compound.

[0094]

[0083] In some embodiments, first carbon-based material 112 and the second carbonbased material 122 may be the same, or may be different. In some embodiments, the first and / or second carbon-based materials 112 or 122 include, single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nano-pearl powder, functionalized carbon, carbon black, graphite powder, allotropes of graphene, activated black carbons, and the like.

[0095]

[0084] In some embodiments, metal-chalcogen compound 114, may include a metal selected from Cu and Sn, and a chalcogen selected from Te, Se, and S.

[0096]

[0085] In some embodiments, metal-chalcogen compound layer 114 may include SnSe nanostructure, CuSe nanostructure, CuS nanostructure, CuTe nanostructure, SnTe nanostructure, SnS nanostructure, 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. (given from other metal-chalcogens).

[0097]

[0086] In some embodiments, metal-chalcogen compound 14 has the following chemical formula MSnX, where M is selected from Cu, Ag, Co, Ni and the like and X is selected from Te, Se, and S.

[0098]

[0087] In some embodiments, first layer 112 may include oriented SWCNT, DWCNT and MWCNT. In such case, the longitudinal axes of the SWCNTs, DWCNTs and MWCNTs are parallel to a surface of second layer 114.

[0099]

[0088] In some embodiments, a mass loading of layer 112 is between 0.1 mg / cm2to 20 mg / cm2, for example, 0.15 mg / cm2, 0.3 mg / cm2, 0.5 mg / cm2, 1 mg / cm2, 1.5 mg / cm2, 2 mg / cm2, 5 mg / cm2, 7 mg / cm2, 10 mg / cm2, 15 mg / cm2, 20 mg / cm2, and any value in between. In some embodiments, a mass loading of layer 114 is between 0.1 mg / cm2to 20.0 mg / cm2, for example, 0.1 mg / cm2, 0.3 mg / cm2, 0.5 mg / cm2, 1 mg / cm2, 1.5 mg / cm2, 5 mg / cm2, 7 mg / cm2, 10 mg / cm2, 15 mg / cm2, 20 mg / cm2, and any value in between.

[0100]

[0089] In some embodiments, first electrode 110 may comprise a composite material comprising a mixture of the carbon-based material and the nanostructure of the metal- chalcogen compound. For example, electrode 110 may include a mixture of SnS nanoflower, and MWCNTs or carbon nano-pearl powder.

[0090] In some embodiments, the weight ratio between the carbon-based material and the nanostructure of metal-chalcogen mixture compound is between 1:1 to 1:4, for example, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, and any value in between.

[0101]

[0091] In some embodiments, when comprising the composite material, first electrodes 110 may further comprise additives, such as, Polyvinylidene fluoride (PVDF).

[0102]

[0092] In some embodiments, electrolyte 20 may be placed between electrodes 110 and 120. For example, when electrode 110 includes metal-chalcogen compound layer 114, electrolyte 20 is located between layer 114 and electrode 120, as illustrated.

[0103]

[0093] In some embodiments, supercapacitor 100 and / or supercapacitor 200 may further include a first and a second conductive layers 35. First and second conductive layers 35, may be attached from one side to first current collecting layer 30 or second current collecting layer 30, and to the first carbon-based 12 and 112 material or second carbon-based material 12 or 122, respectfully. In some embodiments, conductive layers 35 may include 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 each one of first and second conductive layers 35 may be between 0.1 mg / cm2to 20.0 mg / cm2.

[0104]

[0094] In some embodiments, supercapacitor 100 and / or supercapacitor 200 may not include conductive layers 35.

[0105]

[0095] Reference is now made to Fig. 2 which is a method of making an electrode for a supercapacitor according to some embodiments of the invention. In step 210, nanostructures of metal-chalcogen compound 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. Some nonlimiting examples for synthesizing metal-chalcogen compounds are given herein below in the Examples section.

[0106]

[0096] In step 220, a first layer comprising carbon-based material is formed, by any known method. For example, the first layer may be deposited on a substrate. The carbonbased material may be mixed with a binder (e.g., PVDF, CMC, etc.) and a solvent (e.g., NMP, water, etc.) and may be deposited by at least one of, spraying, printing, applicating, etc. on a substrate. In some embodiments, the substrate is selected from, a current collector layer (e.g., layer 30) or conductive layer (e.g., layer 35). In some embodiments, the carbonbased material includes single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nano-pearl powder, functionalized carbon, carbon black, graphite powder, allotropes of graphene, and activated black carbons, and the like.

[0107]

[0097] In step 230, a second layer comprising the nanostructures of the metal-chalcogen compound may be deposited on one side of the first layer. 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.

[0108]

[0098] In some embodiments, steps 220 and 230 may be combined together to form a single layer comprising both the carbon-based material and the metal-chalcogen compound. In some embodiments, the carbon-based material and the metal-chalcogen compound may be mixed and be deposited by at least one of, spraying, printing, applicating, etc. on the carbon-based material layer.

[0109]

[0099] In some embodiments, the method may further include depositing the electrode on a current collector, for example, current collector, for example, current collector 30.

[0110]

[0100] In some embodiments, the method may include applying a first conductive layer (e.g., layer 35) on top of a current collector (e.g., current collector 30). The method 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., NMP, water, etc.). Followed by depositing the mixture on one surface of the current collector by at least spraying, printing, applicating, etc.

[0111]

[0101] In some embodiments, the method may further include assembling a supercapacitor using a first electrode (e.g., electrode 10A or 110), electrolyte 20 and a second electrode, selected from; a carbon-based material deposited on a current collector (e.g., electrode 120); and electrode 10B, as illustrated in Figs. 1A and IB.

[0112] Examples

[0113]

[0102] Synthesis of SnSe nanosheets

[0114]

[0103] Solution processed and phase controlled Two-Dimensional (2D) SnSe nanosheets fabrication has been done by adopting one-pot heat up synthetic route. In one-pot heat up synthesis SnCl45H2O, SeO2, 1-10 Phen, and 0AM heated together in nitrogen (N2) environment. The novel features to implement this synthesis route are, (1) Inexpensive and non-toxic selenium precursor (SeO2) has been used instead of expensive, toxic, and complicated selenium source like sodium selenosulfate. (2) Single phase and single crystalline SnSe prepared via controlled reaction parameters. (3) This synthesis route encourages to optimized for SnSe 2D morphology. In brief, 0.05 M SnCl4:5H2O, 0.05 M SeOi and 0.05 M - 1 - 10 Phenanthroline mixed in 20 ml 0AM. As Selenium is insoluble in water so here in current situation 0AM acts as solvent. 1-10 Phen acts as capping and reductant and further leads important role to achieve single phase SnSe. The mixed solution stirred at 15 min in nitrogen (N2) environment with flow rate 0.5 L / min. With same N2 flow rate tri- neck flask heated up to 120 °C. After reaching 120 °C temperature, flow rate change to 1 L / min for 10 min. Again, the solution heated up to 260 °C with flow rate 0.5 L / min. At 260 °C, the flow rate maintained about 0.1 L / min for next 30 min and the solution cooled down naturally. Finally, this product purified by centrifuge at 4500 rpm by adding ethanol and acetone for several times.

[0115]

[0104] Reference is now made to Fig. 3 with is an X-ray diffraction spectrum for 2D SnSe nanosheets according to some embodiments of the invention. The spectrum was taken from the synthesized SnSe. A further SEM analysis confirms the surface morphology of the 2D SnSe nanosheets for 0.05 M concentration depicted is shown in Fig. 4.

[0116]

[0105] Synthesis of CuSe nanostructure

[0117]

[0106] Copper (II) chloride dihydrate (CuC12.2H2O, 99%, Fisher chemicals), selenium dioxide (SeO2, 99.4%), 1-10 phenanthroline (C12H8N2, 99%) and Oleylamine (C18H37N, 80-90%, Acros organics) were used for synthesis as received without further purification, as schematically shown in Fig. 5. lire synthesis of CuSe nanocrystals was carried out using a facile one-pot chemical route and oleylamine as a solvent. In typical synthesis process CuC12-2H2O, SeO2 with molar concentrations such as 0.02 M, 0.05 M, 0.1 M and 0.15 M and 1-10 phenanthroline (0.1 M) were dissolve in 20 ml of oleylamine with magnetic stirring to form the precursor solution at room temperature under N2 atmosphere for 15 min into a three-neck flask. The reaction solution is heated up to 90 °C and kept for 10 min. After that, the temperature was increased to 180 °C and kept for 1 hr. After naturally cooling down to room temperature, the final products were collected by centrifugation and washed with ethanol and acetone several times.

[0118]

[0107] Reference is now made to Fig. 6 which a SEM image of CuSe according to some embodiments of the invention. The SEM images of copper selenide structures obtained from the reaction with 0.02, 0.05, 0.1 and 0.15 molar concentration are shown in Figure 6 (a-h). As shown in Fig. 6 (a, b, c, g, h) CuSe crystals grow in an irregular pattern. Nanostructures with hexagonal forms and a platelike morphology are shown in Fig. 6 (d, e). The thicknesses of the hexagonal plates ranged from 40 nm to 70 nm. A wide range of size distribution was observed for the edge length of the hexagons, varying between 89 nm and 235 nm.

[0119]

[0108] Reference is now made to Fig. 7A which shows XRD patterns of CuSe according to some embodiments of the invention. The crystal structure and chemical composition of copper selenide powder was confirmed by XRD. The typical XRD patterns for copper selenide synthesized at concentrations of 0.02 M, 0.05 M, 0.1 M, and 1.15 M are shown in Fig. 7A (a-d), demonstrating the polycrystalline nature of the material. The sharp and narrow peaks detected in the XRD pattern from sample with 0.02 M concentration can be attributed to the mix phase of copper selenide (Fig.7 A (a)). The peak positions and intensities were matching with the standard data for hexagonal CuSe denoted by @, Cubic CuSe2 denoted by * and klockmannite CuSe (JCPDS No. 01-086-1240) assigned by @.

[0120]

[0109] Fig. 7 A (b) shows XRD pattern for 0.05 M copper selenide can be index to mix phase. The peak positions and intensities were matching with the standard data for hexagonal CuSe assigned by @, Cubic CuSe2 denoted by * and klockmannite CuSe denoted by @.

[0121] [HO] The sharp and narrow peaks observed from sample with 0.1 M concentration in the XRD pattern (Fig. 7 A) can be indexed to the (1 0 1), (1 0 2), (1 0 3), (0 0 6), (1 0 4), (1 0 5), (1 0 6), (00 8), (1 1 0), (1 0 8), (2 0 1 ), (2 03), and (2 0 8) planes of hexagonal crystals of CuSe with klockmannite phase. The peak positions and intensities were matching well with the standard data for hexagonal CuSe.

[0122]

[0111] Fig. 7A (d) shows XRD pattern for sample with 0.15 M concentration can be index to mix phase. The peak positions and intensities were matching with the standard data for hexagonal CuSe assigned by @, Cubic CuSe2 denoted by * and Cuo.svSe denoted by *.

[0123]

[0112] The pure klockmannite phase of CuSe has been confirmed from the XRD for the sample prepared at 0.1M concentration.

[0124]

[0113] Reference is now made to Fig. 7B wdiich show's Transmission Electron Microscopy (TEM), High-resolution (HR) TEM, Selected Area Electron Diffraction (SAED), and Energy Dispersive X-ray Spectrum (EDS). Fig. 7B (a) and (b) shows a typical TEM and high-resolution (HR) TEM image of single CuSe Nanosheet, revealing the hexagonal nanosheet with well-resolved 2D lattice fringes. The value of fringe spacing is 0.341 nm match well with inter planner d-spacing of the (100) plane of klockmannite CuSe. The SAED pattern (Fig. 7B (c)) also implies single-crystalline hexagonal structure. Additionally, the energy- dispersive X-ray spectrum (EDS) (Fig. 7B (d)) reveals two strong peaks of Cu and Se elements. The quantitative EDS analysis shows that the atomic ratio of Cu and Se is close to the intrinsic 1:1 stoichiometry, implying the homogeneous purity of CuSe NSs.

[0125]

[0114] Reference is now made to Figs. 7C which is the Nitrogen adsorption / desorption isotherms and Pore size distributions of the CuSe nanosheets and BJH pore-size distribution curve (inset). The surface area and pore size of CuSe nanostructures were obtained from nitrogen desorption-desorption isotherms (Figure 9) using the multiple-point BET method. The pore size and specific surface area of CuSe nanosheets is found to be 5.13 nm and the specific surface area is 10.90 m2 / g.

[0126]

[0115] The electrochemical performance for CuSe nanostructure supercapacitor study was conducted in three-electrode configuration: Dip and dry method is used to deposit CuSe nanostructure over SS substrate. As synthesized CuSe powder (0.1M) 10 mg is dissolved in 10 ml of ethanol. SS substrate (1 X 1 cm) was dipped into the prepared CuSe solution for 20 s to adsorb CuSe onto SS substrate and dried by IR healing. Such process was repeated for 20 times for optimum covering of CuSe on the SS substrate. Mass loading is calculated by weighing substrate before and after deposition and their subtraction (Weight difference method).

[0127]

[0116] Synthesis of SnS nanostructure

[0128]

[0117] Tin (II) Chloride dihydrate (SnCl2:2H2O >= 97%), Sulfur sublimed (99.5%, Acros organics), and Oleylamine (C18H37N, 80-90%) were used as received without further processing.

[0129]

[0118] The synthesis of SnS flower-like nanostructures was done by employing a simple and economic one-pot heat up route. In typical synthesis, SnCh:2H2O (0.05M), and Sulfur (0.1M) are used as Tin source and sulfur itself; and Oleylamine (10 ml) was used as solvent. In the beginning, sulfur was added to OA and stirred until the solution turned orange, or until the sulfur completely dissolved in OA. Following that, SnCh:2H2O was added to the solvent and stirred for 10 minutes under N2 environment. Later the solution was heated to 120 °C and kept in this temperature for 20 min. Again, the temperature of the three-neck flask was heated to 180 °C and kept in this temperature for 1 hour. Once it cools down naturally, the final product is collected by centrifugation and washed with ethanol for 4 to 5 times.

[0119] Reference is now made to Fig. 8 A which shows XRD patern of SnS according to some embodiments of the invention. The structural feature of as synthesized flower like SnS nanostructure by XRD spectra is shown in Fig. 8A. The XRD pattern was recorded in between 20° to 80° scanning angle range. All observed diffraction peaks of as-synthesized nanomaterial could be indexed to orthorhombic SnSe with lattice parameters of a = 5.6730, b = 5.7500 and c = 11.7600 A (JCPDS number 01-079-2193).

[0130]

[0120] Reference is now made to Fig. 8B which shows SEM images of SnS nanostructure according to some embodiments of the invention. The SEM analysi s confirms the surface morphology of the 3D flower-like SnS nanostructures. The SEM images of 3 D flower-like SnS nanostructures were also confirmed by a respective EDS, not shown. The low magnification SEM image (Fig. 8A-a) depicts 3D flower like SnS nanostructures and the high magnification image shown in Fig. 8A-b reveals a large coverage of flower-like nanostructures. The average thickness of 3D flower-like SnS nanostructures is 14 nm. The EDS spectrum shown in clearly consisted of peaks for Sn and S. It clearly recommended the formation of Tin Sulfide phase. Finally, EDS analysis is strongly consistent with XRD results, and it confirms the successfully deposited 3D flower-like SnS nanostructures by the proposed chemical route.

[0131]

[0121] Functionalization of MWCNTs

[0132]

[0122] 95% pure MWCNTs (5-15 pm as length and 15-20 nm as outward diameter) was refluxed using H2O2 at 90 °C for 48 h in order to anchor oxygenated functional groups and to remove amorphous carbon derivatives. The obtained residue was rinsed repeatedly using double distilled water (DDW) several times and dried at 60 °C for 12 h. To obtain a stable dispersion, sonication of 0.125 g of MWCNTs was performed in Triton X-100 surfactant with 25 mL of DDW (Tx-100: DDW: 1:100) for 1 h.

[0133]

[0123] Cyclic voltammetry measurement

[0134]

[0124] The mass loading for deposited CuSe is 0.2 mg electrode is examined in various electrolyte such as NaOH, KOH, NaCl, LiCl and Na2SO3with fixed concentration 0.5 M and scan rate 100 mV / s. In three electrode cell configuration CuSe electrode used as working electrode (WE), Ag / AgCl as reference electrode (RE) and platinum wire as counter electrode (CE). The specific capacitance of CuSe electrodes of unit area (1 cm ) dipped in different electrolyte were estimated from the CV curve according to the following equation (1).

[0135]

[0125] Where, ‘Cs’ is the specific capacitance is the potential sweep rate (mVs ), (Vc-Va) is an operational potential window, ‘I’ is the current response (mA) and ‘m’ is the deposited mass of sample electrode.

[0136]

[0126] Reference is now made to Fig. 9 which shows CV graph recorded for scan rate of 100 mV / s, using equation (1). Fig. 9 (a) shows CV curves at different electrolytes at 0.5 M concentration and 9 (b) shows the corresponding capacitance graph.

[0137]

[0127] The specific and Areal capacitance values of CuSe for different electrolyte are given in Table 1.

[0138]

[0128] Table 1

[0139]

[0129] It has been observed from CV curve that CuSe electrode showing good current distribution and high CV area with high specific capacitance in NaOH electrolyte as compared to other electrolytes.

[0140]

[0130] Therefore, NaOH electrolyte was selected and performed concentration optimization using CV. The concentration of NaOH was increased from 0.5 M to 3 M with 0.5 interval and corresponding CV curves were recorded as well as analyzed at fixed mass loading (0.2 mg) and scan rate 100 mV / s, as illustrated in Fig. 10

[0141]

[0131] Fig. 10(a) shows CV curves at different concentrations of NaOH and Fig. 10(b) shows corresponding Capacitance graph. The calculated specific capacitance values are given in following Table 2.

[0142]

[0132] Table 2

[0143]

[0133] In some embodiments, after electrolyte concentration variation it observed that the capacitance has been increased. The highest capacitance has been observed in two different concentrations i.e. 1.5 M and 2.5 M NaOH. But the current distribution for 2.5 M NaOH is comparatively better than 1.5 M NaOH which will be benefited for device fabrication. The mass loading variation has been performed using optimized electrolyte concentration i. e. 2.5 M NaOH. The CV has been performed for different mass loading and it is shown in Fig. 11.

[0144]

[0134] Fig. 11(a) shows CV curves at different CuSe mass loading in 2.5 M NaOH @ 100 mV / s and Fig. 11(b) shows the corresponding capacitance graph.

[0145]

[0135] The calculated specific capacitance values are given in Table 3. Table 3 shows the specific and areal capacitance values of CuSe for different mass loading.

[0146]

[0136] Table 3

[0147]

[0137] Reference is now made to Fig. 12 which shows electrochemical measurements of the mass loading (0.45 mg) CuSe over SS and molar concentration (2.5 M) of NaOH. The various scan rate CV curves for CuSe were examined and shown in Fig. 12 (a). The specific capacitance has been seen to be decrease as scan rate increases from 2 mv / s to 100 mV / s (Fig. 12 (b)) which might be due to the restricted time limitation in the electrolytic interaction process. The maximum capacitance values for CuSe nanosheets is found to be 718.04 F / g (323.12 mF / cm2) for scan rate of 2 mV / s.

[0148]

[0138] Fig. 12 shows the electrochemical characterization of the 0.45 mg CuSe nanosheets on SS substrate (a, b) CV curves of the CuSe nanosheets at different scanning rates and their corresponding capacitance (in F / g and mF / cm2), (c, d) Galvanostatic Chargedischarge (GCD) curves at different current densities and their corresponding capacitance (in F / g and mF / cm2).

[0149]

[0139] All the calculated capacitance values are shown in Table. 4.

[0150]

[0140] Table 4 shows the specific and Areal capacitance values of CuSe for different scan rates.

[0151]

[0141] The rate capability of material of a device according to some embodiments of the invention, was checked / measured using a Galvanostatic Charge-discharge (GCD) as shown in Fig. 12 (c) for at different current densities from 4 A / g to 1 A / g. The highest capacitance for 1 A / g current density is found to be 272.34 F / g (122.56 mF / cm2). The capacitance values for different current density have been calculated and are shown in Table. 5.

[0152]

[0142] Table 5 includes the specific and Areal capacitance values of CuSe for different current density.

[0153]

[0154]

[0143] Electrochemical impedance spectroscopy (EIS) study

[0155]

[0144] The assessment of the EIS is one of the most important factors for supercapacitor electrodes. In order to explore the electrical conduction, ionic diffusion, charge transfer mechanisms, and source of capacitive behavior, electrochemical impedance spectroscopy (EIS) tests using the Nyquist graph’(Z' v- ” Z") at a range of frequencies between 1 Hz and 100 kHz have been utilized (a). Two distinct parts of the Nyquist plot, such as a kind of semi-curvature and a lined rise at high and low frequency zones, clearly demonstrate the dev’ce's electrochemical characteristics. As can be seen in Fig. 13 (a), the impedance result was examined using a semi-quantitative fit using an analogous circuit simulation of the R(Q(R(QR)) (Fig. 13 (b)).

[0156]

[0145] The intersection of a semicircle in the region of higher frequencies reflects the internal resistance (Rs), which is formed from a combination of contact resistance at the material interface, substrate internal resistance, and electrolytes ionic resistance. The diameter of the semi-circle determines the charge transfer resistance (Ret) involved in the electrochemical process during electrochemical operation. The constant phase element (CPE, Q) is made up of two parts: I Yo - admittance (S.sn) and (ii) a fractional element n that can range between 0 and 1. If n is close to 1, the behavior of the electrode appears to be the same as that of a perfect capacitor. Fig. 13 (a) showing the Nyquist plot of the CuSe fitting to equivalent circuit R(Q(R(QR))), Here black colored data indicating measured and red colored data indicating fitted (calculated) data. Fig. 13 showing the good fit with a least chi-square value in orders of 10-4. The fitted circuit showing the small solution (Rs) resistance of 0.75 Ohm.cm2along with the charge transfer resistance (Rct) of 161.90 ohm.cm2.

[0146] Fig. 13 (c) and (d) show the Bode plots of phase angle and capacitance versus frequency. From Fig. 13 (c), the electrode showing the maximum phase angle value of 64.63° and for the ideal capacitor, it is 90°, which means the electrode showing towards a capacitive nature. A crucial variable is the relaxation time constant of the supercapacitor electrode (r0= 1 / fo, fo = signature frequency). Low relaxation time indicates that electrolyte ions have reached the film and that the electrochemical cell has reached its maximal capacitance while still rapidly recharging. Indicating that fast charge diffusion occurs between reversible insertion / extraction operations, the estimated r0was 0.2 s (Fig. 13. (c)). Furthermore, at a phase angle of -45°, r0was calculated from a frequency vs. phase angle plot (Fig. 13 (c)) because resistive and capacitive impedances are identical. The electr’de's relaxation time was 0.2 s, which represents the rate at which the accumulated charge may be successfully distributed. The computed r0was 0.2 s (Fig. 13 (d)), indicating that rapid charge diffusion occurs between reversible insertion / extraction processes.

[0157]

[0147] Electrochemical stability

[0158]

[0148] As the stability impacts the electrode’s supercapacitor performance, the electrode’s stability (capacitive retention) was investigated for 3500 CV cycles at 100 mV / s scanning. Fig. 14 shows capacitive retention vs. CV cycles, with CV cycles at inset. The very good capacitive retention of about 96.41 % has been observed from stability measurements. Therefore, Fig. 14 demonstrates the electrochemical stability of CuSe nanosheets electrode through 3500 repetitive CV cycles at 100 mV / s.

[0159] Additional synthesis of CuSe and SnSe in aqueous solution

[0160]

[0149] Copper chloride dihydrate (CuC12.2H2O, 99%), Tin Chloride dihydrate (SnC12:2H2O >= 98%), Selenium powder (Se, 99.5%', Fisher chemicals), Carbin black SUPERP (99%) / SuperP®, BLACK PEARLS®, VULCAN® (99%,) / AC (TOB), L- Ascorbic Acid (C6H8O6, 99%), Sodium Borohydride (NaBH4, 99%). AU the materials were A.R. and used as received without further processing. Water purified with a Milli-Q system with a resistivity > 15 MQ-cm was used throughout the experiments. All the materials mentioned above were used to synthesize CuSe / SnSe / CuSe ©carbon black / SnSe@carbon black, respectively. A Modified Creighton-type procedure synthesis was used. An aqueous solution of metal cation / metal-alloy solutions (50 mL, 0.03M of Mn+) when M= Cu, Sn, Co, Ni or Ag, was prepared in flask A. Then, a solid L-ascorbic acid (0.02M) was added to this solution. The solution in flask A was vigorously stirred and heated to 70-80°C (solution A). At the same time, an aqueous solution of Se-powder (50 mL,0.03M) was prepared in flask B (solution B). solution B was vigorously stirred and heated to 70-80°C; when the solution reached 70°C, a strong reducing agent such as sodium borohydride (NaBH4, 0.06M) was added. Following the heating step, solution A was added in a fast manner to solution B under vigorous stirring, without heating. The mixed solution was allowed to cool down to room temperature while being stirred for 2 hours. In the next step, the mixed solution was centrifuged, and a black precipitate reached. The precipitate was washed a few times with water and then with alcohol. Lastly, black nanostructure was dried in the oven at 85 °C for at least 2 hours, preferably overnight.

[0161]

[0150] Additional combinations of metal cations were tested to create other chalcogenide materials. Various reducing agents such as NaBH4, NaOH and ascorbic acid and a variety of concentrations, such as 0.03M, 0.06M, and 0.12M, were used to test the effect on the nanostructures.

[0162] Synthesis of AgSe and CuSnSe nanostructures

[0163]

[0151] Copper chloride dihydrate (CuC12.2H2.O, 99%), Tin Chloride dihydrate (SnCh:2H2O >= 98%), silver nitrate (AgNCL, 99%), Selenium powder (Se, 99.5%, Fisher chemicals) were used to synthesize the AgSe and CuSnSe nanostructures. A Modified Creighton-type procedure synthesis was used. An aqueous solution of metal cation / metal- alloy solutions (50 mL, 0.03M of Mn+) when M= Cu, Sn, or Ag, was prepared in flask A. Then, a solid L-ascorbic acid (0.02M) was added to this solution. The solution in flask A was vigorously stirred and heated to 70-80°C (solution A). At the same time, an aqueous solution of Se-powder (50 mL,0.03M) was prepared in flask B (solution B). solution B was vigorously stirred and heated to 70-80°C: when the solution reached 70°C, a strong reducing agent such as sodium borohydride (NaBFL, 0.06M) was added. Following the heating step, solution A was added in a fast manner to solution B under vigorous stirring, without heating. The mixed solution was allowed to cool down to room temperature while being stirred for 2 hours. In the next step, the mixed solution was centrifuged, and a black precipitate reached. The precipitate was washed a few times with water and then with alcohol. Lastly, black nanostructure was dried in the oven at 85°C overnight.

[0164]

[0152] Additional combinations of metal cations were tested to create alloyed nanostructures, such as, Cu-Sn, Ag-Sn, etc. In this case, tin aqueous mixture of the cations was used in the same concentration described above, following the same procedure. Moreover, different reducing agents, such as NaOH and ascorbic acid, and various concentrations, such as 0.03M, 0.06M, and 0.12M, were used to test the effect on the nanostructures.

[0165]

[0153] Reference is now made to Fig. 15 which shows HR-SEM images of some of the metal-chalcogen nanostructures disclosed above. The images in Fig. 15 include (a) Low magnification of CuSe on a carbon tape surface (b) High magnification of CuSe on a grid surface (c) Low magnification of CuSnSe on a carbon tape surface (d) High magnification of CuSnSe on a grid surface (e) Low magnification of SnSe on a carbon tape surface (f) High magnification of SnSe on a grid surface, according to some embodiments of the invention.

[0166]

[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.

[0167]

[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.

[0168]

[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. A supercapacitor, comprising: a first electrode comprising a first carbon-based material and a first nanostructure of a metal-chalcogen compound, wherein the metal comprises at least one of Cu, Va, Ni, Fe, Mn, Sn, and any combination thereof, and the chalcogen includes Te, Se, and S; an electrolyte; and a second electrode selected from:(i) a second carbon-based material; and(ii) the second carbon-based material and a second nanostructure of a metal- chalcogen compound, wherein the metal comprises at least one of Cu, Va, Ni, Fe, Mn, Sn, and any combination thereof, and the chalcogen includes Te, Se, and S.

2. The supercapacitor of claim 1, wherein the first electrode comprises: a first layer comprising the carbon-based material and a second layer comprising the nanostructure of the metal-chalcogen compound.

3. The supercapacitor of claim 2, wherein a mass loading of the first layer is between 0.1 mg / cm2to 0.3 mg / cm2and a mass loading of the second layer is between 0.2 mg / cm2to 10.0 mg / cm2.

4. The supercapacitor of claim 1, wherein the first electrode comprises: a composite material comprising a mixture of the carbon-based material and the nanostructure of the metal-chalcogen compound.

5. The supercapacitor according to any one of claims 1 to 4, further comprising: a first current collector; a first conductive layer, attached from one side to the first current collector and to the first carbon based material; a second current collector; and a second conductive layer, attached from one side to the second current collector and to the second carbon-based material.

6. The supercapacitor of claim 5, wherein the first and second conductive layers comprise a mixture of between 70 to 90 wt.% graphite, between 20 to 5 wt.% multi-walled carbon nanotubes (MWCNT) and binder.

7. The supercapacitor according to any one of claims 1 to 6, wherein the nanostructure of the metal-chalcogen compound includes morphologies, selected from, nanoparticle, nanotube, nanospheres, nanosheets, nanowires, and nanoflower.

8. The supercapacitor according to any one of claims 1 to 7, wherein the carbonbased material comprises at least one of, single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nano-pearl powder, functionalized carbon, carbon black, Graphite powder, allotropes of graphene, and activated black carbons.

9. The supercapacitor of claim 8, wherein the first layer comprising oriented SWCNT, DWCNT, and MWCNT, originated parallel to a surface of the second layer.

10. The supercapacitor according to any one of claims 1 to 9, wherein the electrolyte comprises at least one of, KOH, NaOH, NaCl, KC1, Na2SOg, Na2SO4, NaC104, TBABF4, TBAPF6, TEAPF6, K2SO3, TEABF4, LiC104, LiCl, LiOH, and Li2SO4.

11. The supercapacitor according to any one of claims 1 to 10, wherein the electrolyte is an aqueous or organic gel electrolyte.

12. The supercapacitor of claim 11, wherein the aqueous or organic gel comprises at least one of polyvinyl alcohol (PVA), n-methyl-2-pyrrolidone (NMP), cellulose powder, acetonitrile, carboxymethyl cellulose (CMC), and sulfonated tetrafluoroethylene based fluoropolymer-copolymer (Nafion).

13. The supercapacitor according to any one of claims 1 to 12, wherein the electrolyte is an aqueous solution and the supercapacitor further comprises a separator.

14. The supercapacitor according to any one of claims 1 to 13, wherein each one of the first and second electrodes further comprises an additive.

15. The supercapacitor of claim 14, wherein the additive is Polyvinylidene fluoride (PVDF).

16. The supercapacitor according to claim 1, further comprising two current collectors, each attached to a surface of either the first or the second electrode not facing the electrolyte.

17. A supercapacitor, comprising:a first electrode; an electrolyte; and a second electrode, wherein each one of the first electrode and the second electrode comprises a carbon-based material and a nanostructure of metal-chalcogen compound, wherein the metal comprises at least one of: Cu, Ag, Ni, Co, Sn, or any combination thereof, and the chalcogen is selected from Te, Se, S, or any combination thereof.

18. The supercapacitor of claim 17, wherein each one of the first electrode and the second electrode comprises: a first layer comprising the carbon-based material and a second layer comprising the nanostructure of the metal-chalcogen compound.

19. The supercapacitor of claim 18, wherein a mass loading of the first layer is between 0.1 mg / cm2to 20.0 mg / cm2and a mass loading of the second layer is between 0.1 mg / cm2to 20.0 mg / cm2.

20. The supercapacitor of claim 19, wherein each one of the first electrode and the second electrode comprises: a composite material comprising a mixture of the carbon-based material and the nanostructure of the metal-chalcogen compound.

21. The supercapacitor of claim 20, wherein the weight ratio between the carbonbased material and the nanostructure of the metal-chalcogen mixture compound is between 1:1 to 1:4.

22. The supercapacitor of claims 17-21, wherein the nanostructure has a pore size greater than 9 m2 / g.

23. The supercapacitor of claims 17-21, wherein the nanostructure has a pore size between 4 and 6 nm.

24. A method of making an electrode for a supercapacitor comprising: synthesizing nanostructures of metal-chalcogen compound, wherein the metal is selected from includes at least one of Cu, Ag, Ni, Co, and Sn and any combination thereof, and the chalcogen is selected from Te, Se, and S; forming a first layer comprising carbon-based material; and depositing a second layer comprising the nanostructures of metal-chalcogen compound on one side of the first layer.

25. The method of claim 24, wherein the carbon-based material comprises at least one of: single-wall carbon nanotubes (SWCNT), double-wall carbon nanotubes (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nano-pearl powder, functionalized carbon, carbon black, graphite powder, allotropes of graphene, and activated black carbons.

26. The method of claims 24 and 25, further comprising depositing the electrode on a current collector.

27. The method of claim 26, further comprising, depositing a conductive layer on the current collector prior to depositing the electrode.

28. The method of claims 26 or 27, further comprising assembling a supercapacitor using a first electrode according to any one of claims 24 and 25, an electrolyte and a second electrode, selected from;(i) a carbon-based material deposited on a current collector; and(ii) an electrode according to any one of claims 24 and 25.

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