Capacitor electrode material, capacitor electrode, preparation method thereof, and supercapacitor

Abstract

The present invention relates to the field of electrochemical energy storage technology, and discloses a capacitor electrode material, wherein the electrode material comprises an active substance, a conductive agent and a binder, wherein the active substance is a sulfur-doped nanocarbon cage, the sulfur-doped nanocarbon cage has a microporous structure and a mesoporous structure, and the BET specific surface area of the sulfur-doped nanocarbon cage is greater than 500 m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 30%; the total pore volume of the sulfur-doped nanocarbon cage is greater than 1cm 3 / g, and the proportion of micropore volume to total pore volume is less than 15%; X-ray photoelectron spectroscopy measured the mass percentage of carbon on the surface of the sulfur-doped nanocarbon cage to be 80-98%, and the mass percentage of sulfur to be 0.1-10%. The sulfur-doped nanocarbon cage contained in this electrode material has a multi-level pore structure dominated by mesopores, which is conducive to the transmission of electrolyte ions. At the same time, it has a high sulfur doping amount and a large specific surface area. In combination with a conductive agent and a binder, it exhibits good rate performance, high specific capacity, and high specific capacitance in supercapacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and in particular to capacitor electrode materials, capacitor electrodes, preparation methods thereof, and supercapacitors. Background Art

[0002] With the depletion of fossil energy and the intensification of environmental problems, new energy sources have become a global focus to ensure sustainable development. Energy storage devices, including lithium-ion batteries, supercapacitors, and fuel cells, have been extensively researched. As important active materials in energy storage devices, nanocarbon materials not only offer excellent performance but also have abundant raw material sources and low costs. In recent years, a variety of porous carbon materials have been developed and applied, including activated carbon, graphene, carbon nanotubes, template carbon, hollow carbon spheres, and nanocarbon cages. Nanocarbon cages exhibit a range of unique physical and chemical properties due to their hollow structure, large specific surface area, and rich pore structure. Depending on the template, nanocarbon cages can exhibit either square or circular structures. Hu Zheng's group at Nanjing University reported on a variety of square nanocarbon cage materials that exhibit excellent performance in applications such as supercapacitors and lithium-sulfur batteries. Xu Bin's group at Beijing University of Chemical Technology prepared graphitized porous carbon with a cage-like structure by thermally decomposing transition metal organic acid salts. The high degree of graphitization, large specific surface area, and abundant pores of this material enable high specific capacity and cycling stability in potassium-ion battery anodes. This shows that nanocarbon cages have good development potential and application prospects in the field of energy storage.

[0003] Furthermore, the incorporation of heteroatoms such as sulfur can effectively enhance the pseudocapacitance of carbon cage materials, increasing the overall capacity of the material. However, the sulfur-doping process for nanocarbon cages is complex, the sulfur atom incorporation rate is low, and the hollow structure and graphitized carbon layer of the carbon cage are generally affected during the doping process, which to some extent affects the electrochemical performance and commercial application of this type of material. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem of poor capacitance performance of supercapacitor electrode materials in the prior art and to provide a capacitor electrode material, a capacitor electrode, a preparation method thereof, and a supercapacitor. The capacitor electrode material exhibits excellent capacitance performance when used in a supercapacitor.

[0005] In order to achieve the above-mentioned object, the first aspect of the present invention provides a capacitor electrode material, which contains an active substance, a conductive agent and a binder, wherein the active substance is a sulfur-doped nanocarbon cage, the sulfur-doped nanocarbon cage has a microporous structure and a mesoporous structure, and the BET specific surface area of the sulfur-doped nanocarbon cage is greater than 500m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 30%; the total pore volume of the sulfur-doped nanocarbon cage is greater than 1cm 3 / g, the proportion of micropore volume to total pore volume is less than 15%; X-ray photoelectron spectroscopy measures that the mass percentage of carbon on the surface of the sulfur-doped nanocarbon cage is 80-98%, and the mass percentage of sulfur is 0.1-10%.

[0006] A second aspect of the present invention provides a capacitor electrode, comprising a current collector and an electrode material coated and / or filled on the current collector, wherein the electrode material is the capacitor electrode material described in the first aspect.

[0007] The third aspect of the present invention provides a method for preparing a capacitor electrode, which comprises coating and / or filling a slurry containing a capacitor electrode material and a solvent on a current collector, drying, and rolling or not rolling. The capacitor electrode material is the capacitor electrode material described in the first aspect.

[0008] The fourth aspect of the present invention provides a supercapacitor, which includes a core and an electrolyte, wherein the core and the electrolyte are sealed in a battery casing, the core includes an electrode and a diaphragm, and the electrode is the capacitor electrode described in the second aspect or a capacitor electrode prepared according to the preparation method described in the third aspect.

[0009] Through the above technical solution, the capacitor electrode material provided by the present invention contains an active substance, a conductive agent and a binder, wherein the active substance is a sulfur-doped nanocarbon cage, the sulfur-doped nanocarbon cage has a microporous structure and a mesoporous structure, and the BET specific surface area of the sulfur-doped nanocarbon cage is greater than 500m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 30%; the total pore volume of the sulfur-doped nanocarbon cage is greater than 1cm 3 / g, with the proportion of micropore volume to total pore volume being less than 15%; X-ray photoelectron spectroscopy indicates that the mass percentage of carbon on the surface of the sulfur-doped nanocarbon cage is 80-98%, and the mass percentage of sulfur is 0.1-10%. The sulfur-doped nanocarbon cage contained in this capacitor electrode material has a multi-level pore structure dominated by mesopores, which facilitates the transport of electrolyte ions. It also has a high sulfur doping content and a large specific surface area. When combined with a conductive agent and a binder, it exhibits good rate performance, high specific capacity, and high specific capacitance in supercapacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a high-resolution transmission electron microscopy image of the sulfur-doped nanocarbon cage prepared in Preparation Example;

[0011] Figure 2is an X-ray photoelectron spectroscopy (XPS) graph of the sulfur-doped nanocarbon cage prepared in Preparation Example;

[0012] Figure 3 This is the XPS S2p spectrum of the sulfur-doped nanocarbon cage prepared in the preparation example;

[0013] Figure 4 is the Raman curve of the sulfur-doped nanocarbon cage prepared in Preparation Example;

[0014] Figure 5 1 is the cyclic voltammetry curve of the capacitor electrode prepared in Example 1 at different scan rates in potassium hydroxide electrolyte;

[0015] Figure 6 1 is the charge-discharge curve of the capacitor electrode prepared in Example 1 at different current densities in potassium hydroxide electrolyte;

[0016] Figure 7 1 is the charge and discharge curve of the capacitor electrode prepared in Example 1 at different current densities in tetraethylammonium tetrafluoroborate solution;

[0017] Figure 8 This is the rate curve of the capacitor electrode prepared in Example 1 as the negative electrode of a lithium ion capacitor. DETAILED DESCRIPTION

[0018] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0019] The first aspect of the present invention provides a capacitor electrode material, which contains an active substance, a conductive agent and a binder, wherein the active substance is a sulfur-doped nanocarbon cage, the sulfur-doped nanocarbon cage has a microporous structure and a mesoporous structure, and the BET specific surface area of the sulfur-doped nanocarbon cage is greater than 500m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 30%; the total pore volume of the sulfur-doped nanocarbon cage is greater than 1cm 3 / g, the proportion of micropore volume to total pore volume is less than 15%; X-ray photoelectron spectroscopy measures that the mass percentage of carbon on the surface of the sulfur-doped nanocarbon cage is 80-98%, and the mass percentage of sulfur is 0.1-10%.

[0020] According to some embodiments of the present invention, the nanocarbon cage has a microporous structure and a mesoporous structure, and the BET specific surface area of the nanocarbon cage is greater than 500m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 30%, preferably, the BET specific surface area of the nanocarbon cage is 500-1600m 2 / g, and the proportion of the specific surface area in micropores to the total specific surface area is less than 20%.

[0021] According to some embodiments of the present invention, the total pore volume of the nanocarbon cage is greater than 1 cm 3 / g, the proportion of micropore volume to total pore volume is less than 15%, preferably, the total pore volume of the nanocarbon cage is greater than 1.4cm 3 / g, the proportion of micropore volume to total pore volume is less than 10%, more preferably, the total pore volume of the nanocarbon cage is 1.4-3.6cm 3 / g, and the proportion of micropore volume to total pore volume is 2.5-4.5%.

[0022] According to some embodiments of the present invention, preferably, in the pore size distribution curve of the nanocarbon cage, there is a micropore distribution peak at 0.59-0.63 nm, and there are two mesopore distribution peaks at 2.73-4.1 nm and 3.877-15.6 nm.

[0023] In the present invention, the pore structure properties of the sulfur-doped nanocarbon cages were determined using the BET test method. Specifically, a Quantachrome AS-6B analyzer was used for measurement. The BET specific surface area and pore volume of the nanocarbon cages were obtained using the Brunauer-Emmett-Taller (BET) method. The mesopore distribution curve was calculated from the desorption curve using the Barrett-Joyner-Halenda (BJH) method, and the micropore size distribution curve was calculated from the isotherm curve using the Horvath-Kawazoe (HK) method.

[0024] According to some embodiments of the present invention, the mass percentage of carbon on the surface of the nanocarbon cage measured by X-ray photoelectron spectroscopy is 80-98%, and the mass percentage of sulfur is 0.1-10%. Preferably, the mass percentage of carbon on the surface of the nanocarbon cage measured by X-ray photoelectron spectroscopy is 84-95%, and the mass percentage of sulfur is 0.2-5%.

[0025] According to some embodiments of the present invention, the sulfur-doped nanocarbon cages may further contain oxygen, which may be oxygen in various forms formed on the surface of the sulfur-doped nanocarbon cages during the preparation process. Preferably, the mass percentage of oxygen on the surface of the nanocarbon cages, as measured by X-ray photoelectron spectroscopy, is 2-15%, more preferably 4-15%.

[0026] According to some embodiments of the present invention, the sulfur-doped nanocarbon cage may contain doping elements known to those skilled in the art that can be applied to nanocarbon materials. Preferably, the sulfur-doped nanocarbon cage does not contain elements such as nickel, nitrogen, boron, phosphorus, fluorine, chlorine, bromine, and iodine.

[0027] According to some embodiments of the present invention, the content of carbon, sulfur, and oxygen on the surface of the sulfur-doped nanocarbon cage is measured using X-ray photoelectron spectroscopy. X-ray photoelectron spectroscopy analysis is performed on an ESCALab250 X-ray photoelectron spectrometer equipped with Thermo Avantage V5.926 software from Thermo Scientific. The excitation source is monochromatic Al Kα X-ray with an energy of 1486.6 eV and a power of 150 W. The penetration energy used in the narrow scan is 30 eV. The base vacuum during the analysis test is 6.53×10 -9 mbar. Electron binding energies were calibrated using the C1s peak of elemental carbon (284.6 eV). Data processing was performed using ThermoAvantage software, and quantitative analysis was performed using the sensitivity factor method in the analysis module. Prior to testing, the sulfur-doped nanocarbon cages were dried in a helium atmosphere at 150°C and 1 standard atmosphere for 3 hours.

[0028] According to some embodiments of the present invention, preferably, the nanocarbon cage has a spherical or spherical morphology. Preferably, the diameter of the nanocarbon cage is 2-200 nm, preferably 3-50 nm. In the present invention, the surface morphology of the material is characterized by high-resolution transmission electron microscopy (HRTEM), and the model of the high-resolution transmission electron microscope used is JEM-2100 (JEOL Ltd.), and the high-resolution transmission electron microscope test conditions are: accelerating voltage 200 kV. The diameter of the nanocarbon cage can be measured by high-resolution transmission electron microscope images.

[0029] According to some embodiments of the present invention, preferably, in the Raman curve of the nanocarbon cage, I D / I G The range is 0.5-1.5, preferably 0.5-1.1. The nanocarbon cage of the present invention has obvious D peak and G peak, and has a certain degree of graphitization. In the present invention, the Raman test of the nanocarbon cage adopts visible laser Raman measurement method, using 532nm light source to perform Raman characterization on the functional groups of the nanocarbon cage to obtain a characteristic spectrum.

[0030] According to some embodiments of the present invention, preferably, in the X-ray photoelectron spectrum of the nanocarbon cage, the nanocarbon cage has characteristic peaks of sulfur at 161±1eV, 162-166eV and 168±2eV, or has characteristic peaks of sulfur at 162-166eV and 168±2eV.

[0031] According to some embodiments of the present invention, preferably, the mass percentage of sulfur, as determined by a characteristic peak corresponding to 162-166 eV in the X-ray photoelectron spectrum of the nanocarbon cage, is 2-90%, preferably 70-88%, based on the total amount of sulfur on the surface of the nanocarbon cage. In the present invention, the characteristic peak of sulfur in the X-ray photoelectron spectrum of the nanocarbon cage is located at 162-166 eV, indicating that the sulfur in the nanocarbon cage of the present invention is combined with carbon to form a C-S bond, and exists in the form of thiophene sulfur.

[0032] In the present invention, the "sulfur" in the term "sulfur-doped nanocarbon cage" refers to elemental sulfur, and specifically refers to elemental sulfur in various forms formed on the surface of the sulfur-doped nanocarbon cage during the preparation process of the sulfur-doped nanocarbon cage.

[0033] In the present invention, the term "mesopore" is defined as a pore with a pore diameter in the range of 2-50 nm. Pores with a pore diameter less than 2 nm are defined as "micropores".

[0034] According to some embodiments of the present invention, preferably, the method for preparing the sulfur-doped nanocarbon cage comprises the following steps:

[0035] (1) Precursor preparation: providing a homogeneous solution containing a nickel source, a polybasic organic carboxylic acid, a sulfur source, and a solvent, and then removing the solvent from the homogeneous solution to obtain a complex precursor material, wherein the sulfur source is selected from a Group IA bisulfate and / or sulfate;

[0036] (2) calcining: calcining the complex precursor material obtained in step (1) at a constant temperature of 450-700° C. under an inert atmosphere to obtain a pyrolysis product;

[0037] (3) Acid washing: providing an aqueous solution containing the pyrolysis product obtained in step (2), and contacting it with an acid for reaction, followed by solid-liquid separation, washing and drying.

[0038] According to some embodiments of the present invention, the method for preparing the sulfur-doped nanocarbon cage uses sulfate / bisulfate as a sulfur source and activator, and simultaneously cooperates with a nickel source and a polybasic organic carboxylic acid to prepare a complex precursor material. By controlling the calcination temperature, the preparation of the sulfur-doped nanocarbon cage can be achieved simply and efficiently. The prepared sulfur-doped nanocarbon cage has a complete structure, a microporous structure and a large number of mesoporous structures, and a high specific surface area.

[0039] According to some embodiments of the present invention, in step (1), there is no particular limitation on the method for forming the homogeneous solution. For example, the homogeneous solution may be formed by heating, more preferably by heating and stirring. The present invention also does not particularly limit the heating temperature and stirring rate, as long as the homogeneous solution can be formed.

[0040] According to some embodiments of the present invention, preferably, in step (1), the complex precursor material is a complex precursor material obtained by dissolving a nickel source, a polybasic organic carboxylic acid and a sulfur source in a solvent to form a homogeneous solution, and then removing the solvent in the homogeneous solution. There is no particular limitation on the type of the solvent, and the solvent is based on the ability to form a homogeneous solution. Preferably, the solvent is water and / or ethanol, more preferably water; the present invention does not have any particular limitation on the amount of the solvent, and the solvent is also based on the ability to form a homogeneous solution. The solvent in the homogeneous solution can be removed by direct evaporation, and the temperature and process of evaporation can adopt existing technologies known to those skilled in the art. For example, the solvent in the homogeneous solution can be removed by heating and evaporating to dryness.

[0041] According to some embodiments of the present invention, preferably, in step (1), the nickel source is selected from one or more of organic acid salts, carbonates and basic carbonates containing nickel, preferably carbonates and / or basic carbonates containing nickel, more preferably basic nickel carbonate.

[0042] According to some embodiments of the present invention, preferably, the sulfur source is selected from one or more of potassium sulfate, sodium sulfate, potassium bisulfate and sodium bisulfate, more preferably potassium bisulfate and / or sodium bisulfate, further preferably potassium bisulfate.

[0043] According to some embodiments of the present invention, preferably, the polybasic organic carboxylic acid is selected from one or more of citric acid, maleic acid, trimesic acid, terephthalic acid and malic acid, more preferably citric acid and / or terephthalic acid.

[0044] According to some embodiments of the present invention, preferably, the molar ratio of the nickel source, the polybasic organic carboxylic acid, and the sulfur source, calculated as nickel element, is 1:0.1-10:0.1-2, preferably 1:0.5-3:0.3-2, and more preferably 1:0.7-1.5:0.5-1.2. This preferred embodiment is more conducive to obtaining hierarchical porous nanocarbon cages with a high specific surface area containing both micropores and mesopores.

[0045] According to some embodiments of the present invention, preferably, in step (2), the inert atmosphere is provided by at least one of nitrogen, argon, neon and helium, preferably a nitrogen atmosphere.

[0046] According to some embodiments of the present invention, in step (2), the constant temperature roasting temperature is 450-700° C., preferably, the constant temperature roasting temperature is 500-650° C. In the present invention, if the constant temperature roasting temperature is too low, the nickel element in the nanocarbon material cannot be completely removed, while if the temperature is too high, the structure of the nanocarbon cage will be affected and the yield of the carbon cage will be reduced. Only by controlling the constant temperature roasting temperature within the above-defined range can the preparation of sulfur-doped nanocarbon cages be achieved.

[0047] According to some embodiments of the present invention, preferably, the roasting method includes: heating to a constant temperature section at a rate of 0.5-30°C / min, preferably heating to a constant temperature section at a rate of 1-10°C / min; maintaining a constant temperature in the constant temperature section for 20-600 min, preferably 60-480 min.

[0048] According to some embodiments of the present invention, in step (3), the acid can be any acid commonly used in the art, as long as it can remove the nickel element from the pyrolysis product. Preferably, the acid is an aqueous solution of an inorganic acid and / or an aqueous solution of an organic acid, preferably one or more of an aqueous solution of hydrochloric acid, an aqueous solution of sulfuric acid, an aqueous solution of nitric acid, and an aqueous solution of citric acid, more preferably an aqueous solution of hydrochloric acid. Preferably, the concentration of the aqueous solution of an inorganic acid and / or an aqueous solution of an organic acid is 0.1-10 mol / L; and the pH value of the acid is less than 7. The present invention has no particular requirements for the amount of the acid used, as long as it can remove the nickel element from the pyrolysis product.

[0049] According to some embodiments of the present invention, preferably, in step (3), the temperature for contact reaction of the aqueous solution of the pyrolysis product with the acid is 20-120° C., preferably 60-100° C.; and the time for contact reaction is 0.1-48 h, preferably 4-12 h.

[0050] According to some embodiments of the present invention, the washing is used to remove the acid remaining on the sulfur-doped nanocarbon cages caused by the acid washing process. Therefore, various water washing methods that can wash the sulfur-doped nanocarbon cages to neutrality are applicable to the present invention.

[0051] According to some embodiments of the present invention, drying is used to remove water from the sulfur-doped nanocarbon cages. Drying can be performed at normal pressure or reduced pressure. Drying conditions may include: a temperature of 100-120° C. and a time of 6-10 hours.

[0052] According to some embodiments of the present invention, preferably, the nickel source, polybasic organic carboxylic acid and sulfur source are used in such an amount that the mass percentage of carbon on the surface of the prepared sulfur-doped nanocarbon cage is 80-98%, and the mass percentage of sulfur is 0.1-10%.

[0053] According to some embodiments of the present invention, more preferably, the nickel source, the polybasic organic carboxylic acid and the sulfur source are used in such an amount that the mass percentage of carbon on the surface of the prepared sulfur-doped nanocarbon cage is 84-95%, and the mass percentage of sulfur is 0.2-5%.

[0054] According to some embodiments of the present invention, preferably, in the capacitor electrode material, the mass ratio of the active material, the conductive agent and the binder is 7-18:0-3:1, for example, it can be 9:0.5:0.5, 8:1:1, 8:1.5:0.5, 7:2:1, 9:0:1 and any value in the range formed by any two of these values, preferably 8-18:1-3:1, and more preferably 8:1:1.

[0055] According to some embodiments of the present invention, the content and type of the conductive agent are well known to those skilled in the art. Preferably, the conductive agent is selected from at least one of acetylene black, Ketjen black, graphene and carbon nanotubes, more preferably acetylene black.

[0056] According to some embodiments of the present invention, the binder can be any known binder suitable for capacitors, preferably a fluorine-containing resin and / or a polyolefin compound. More preferably, the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber emulsion, and an aqueous dispersion of an acrylonitrile copolymer, with polytetrafluoroethylene being even more preferred.

[0057] A second aspect of the present invention provides a capacitor electrode, comprising a current collector and an electrode material coated and / or filled on the current collector, wherein the electrode material is the capacitor electrode material described in the first aspect.

[0058] According to some embodiments of the present invention, the current collector can be various current collectors known to those skilled in the art. Preferably, the current collector is selected from any one of stainless steel mesh, nickel foam, aluminum foil and copper foil, more preferably stainless steel mesh.

[0059] The third aspect of the present invention provides a method for preparing a capacitor electrode, which comprises coating and / or filling a slurry containing a capacitor electrode material and a solvent on a current collector, drying, and rolling or not rolling. The capacitor electrode material is the capacitor electrode material described in the first aspect.

[0060] According to some embodiments of the present invention, the type and amount of the solvent are well known to those skilled in the art, and all solvents known in the art that can be used for capacitor electrode preparation can be used. Preferably, the solvent is anhydrous ethanol and / or N-methylpyrrolidone, more preferably anhydrous ethanol; the amount of the solvent used is based on the ability to form the desired coating slurry.

[0061] According to a preferred embodiment of the present invention, the method for preparing the capacitor electrode includes:

[0062] The active material, conductive agent and adhesive are mixed, ground evenly and then mixed with a solvent to form a slurry. The slurry is then evenly coated on the current collector, dried and cut into electrode sheets.

[0063] According to another preferred embodiment of the present invention, the method for preparing the capacitor electrode includes:

[0064] The active material, conductive agent and adhesive are mixed, ground evenly and then mixed with a solvent to form a slurry. The grinding is continued until the slurry becomes a clay-like state. The clay-like slurry is stretched into a uniform thin sheet, dried, cut and pressed onto a current collector to obtain an electrode sheet.

[0065] The fourth aspect of the present invention provides a supercapacitor, which includes a core and an electrolyte, wherein the core and the electrolyte are sealed in a battery casing, the core includes an electrode and a diaphragm, and the electrode is the capacitor electrode described in the second aspect or a capacitor electrode prepared according to the preparation method described in the third aspect.

[0066] According to some embodiments of the present invention, preferably, the supercapacitor is a lithium ion capacitor or a double-layer supercapacitor.

[0067] According to some embodiments of the present invention, preferably, the battery housing is a button-type battery housing.

[0068] According to some embodiments of the present invention, the electrolyte can be an electrolyte suitable for capacitors conventionally used in the art. Preferably, the electrolyte is an aqueous electrolyte or an organic electrolyte, preferably any one of an aqueous potassium hydroxide solution, a lithium hexafluorophosphate electrolyte and a tetraethylammonium tetrafluoroborate acetonitrile solution; more preferably, when the supercapacitor is a double-layer supercapacitor, the electrolyte is an aqueous electrolyte, preferably an aqueous potassium hydroxide solution or a tetraethylammonium tetrafluoroborate acetonitrile solution; more preferably, when the supercapacitor is a lithium ion capacitor, the electrolyte is an organic electrolyte, preferably a lithium hexafluorophosphate electrolyte.

[0069] According to some embodiments of the present invention, the diaphragm used in the supercapacitor has both electrical insulation and liquid retention properties, is disposed between the electrodes of the core, and is sealed within the battery housing together with the core. The diaphragm can be any of various commonly used diaphragms in the art. Preferably, the diaphragm is selected from any one of polyethylene, polypropylene, and cellulose diaphragms. More preferably, when the supercapacitor is a double-layer supercapacitor, the diaphragm is a cellulose diaphragm; more preferably, when the supercapacitor is a lithium-ion capacitor, the diaphragm is polypropylene.

[0070] According to some embodiments of the present invention, the lithium ion capacitor may directly use a metal lithium sheet as a positive electrode.

[0071] The capacitor electrode made from the capacitor electrode material provided by the present invention has a multi-level pore structure dominated by mesopores, which is beneficial to the transmission of electrolyte ions. It also has a high sulfur doping amount and a large specific surface area. The capacitor electrode made by combining a conductive agent and an adhesive exhibits good rate performance, high specific capacity and high specific capacitance in supercapacitors.

[0072] The present invention will be described in detail below through examples.

[0073] Unless otherwise specified, all reagents used in the present invention are of analytical grade and commercially available.

[0074] The surface morphology of the material was characterized using high-resolution transmission electron microscopy (HRTEM). The microscope used was a JEM-2100 (JEOL Ltd.) at an accelerating voltage of 200 kV. The diameter of the sulfur-doped nanocarbon cages was measured from the HRTEM images.

[0075] The pore structure properties of the material were determined using the BET test method. Specifically, a Quantachrome AS-6B analyzer was used. The specific surface area and pore volume of the material were obtained using the Brunauer-Emmett-Taller (BET) method. The mesopore distribution curve was calculated from the desorption curve using the Barrett-Joyner-Halenda (BJH) method. The micropore size distribution curve was calculated from the isotherm curve using the Horvath-Kawazoe (HK) method.

[0076] The content of various elements on the surface of the materials and the content of various sulfur and oxygen species were determined by X-ray photoelectron spectroscopy (XPS). The X-ray photoelectron spectroscopy analysis was performed on an ESCALab250 X-ray photoelectron spectrometer equipped with Thermo Avantage V5.926 software from Thermo Scientific. The excitation source was monochromatic Al Kα X-ray with an energy of 1486.6 eV and a power of 150 W. The penetration energy used for narrow scanning was 30 eV. The base vacuum during the analysis was 6.53×10 - 9mbar. Electron binding energies were calibrated using the C1s peak of elemental carbon (284.6 eV). Data processing was performed using Thermo Avantage software, and quantitative analysis was performed using the sensitivity factor method in the analysis module. Prior to testing, the material was dried in a helium atmosphere at 150°C and 1 standard atmosphere for 3 hours.

[0077] The Raman test uses visible laser Raman measurement method and uses a 532nm light source to perform Raman characterization on the functional groups of the nanocarbon cage to obtain a characteristic spectrum.

[0078] Preparation Examples 1-2 are used to illustrate sulfur-doped nanocarbon cages and their preparation methods.

[0079] Preparation Example 1

[0080] Preparation of sulfur-doped carbon nanocages:

[0081] (1) Preparation of precursor: According to the molar ratio of nickel source (calculated as nickel element), polybasic organic carboxylic acid and sulfur source of 1:0.7:1, 30 g of basic nickel carbonate, 29.4 g of citric acid and 27.8 g of potassium hydrogen sulfate were weighed and added to a beaker containing 50 mL of deionized water, and stirred at 70 ° C to obtain a homogeneous solution, which was further heated and evaporated to dryness to obtain a complex precursor material;

[0082] (2) Calcination: The complex precursor material is placed in a porcelain boat, which is then placed in the constant temperature zone of a tube furnace. Nitrogen gas is introduced at a flow rate of 100 mL / min, and the temperature is raised to 650°C at a rate of 2.5°C / min. After holding the temperature for 2 h, heating is stopped and the product is cooled to room temperature under a nitrogen atmosphere to obtain a pyrolysis product.

[0083] (3) Acid washing: The pyrolysis product was added to a 2.0 M HCl aqueous solution and stirred at 80 °C for 10 h, then filtered and washed with deionized water until the filtrate was neutral. The filter cake was then dried at 140 °C for 2 h to obtain sulfur-doped nanocarbon cages.

[0084] Characterization of basic properties of sulfur-doped nanocarbon cages:

[0085] The high-resolution transmission electron microscopy (HRTEM) images of the sulfur-doped nanocarbon cages are shown in Figure 2. Figure 1 As shown in the figure, it can be seen that the sulfur-doped nanocarbon cage has an obvious hollow cage structure with a spherical or quasi-spherical morphology, and the diameter of the sulfur-doped nanocarbon cage is 20-30 nm.

[0086] The X-ray photoelectron spectroscopy (XPS) of the sulfur-doped nanocarbon cage is shown in Figure 2. Figure 2As shown in the figure, the XPS peaks for carbon, oxygen, and sulfur are clearly visible, demonstrating the effective doping of sulfur. Based on the peak areas, the mass percentages of each element on the surface of the sulfur-doped nanocarbon cage can be calculated: carbon is 91.81%, oxygen is 4.95%, and sulfur is 3.24%.

[0087] The XPS S2p spectrum of the sulfur-doped nanocarbon cage is as follows Figure 3 As shown in the figure, it can be seen that there are characteristic peaks of sulfur at 162-166eV and 168±2eV. According to the product peak area after peak separation, it can be calculated that the sulfur content corresponding to the characteristic peak at 162-166eV accounts for 86.44% of the total sulfur content.

[0088] The BET specific surface area of the sulfur-doped nanocarbon cage was 1539.772 m 2 / g, the specific surface area in micropores is 221.386m 2 / g, the ratio of micropore specific surface area to total specific surface area is 14.4%; the total pore volume is 3.523cm 3 / g, micropore volume is 0.1cm 3 / g, the proportion of micropore volume to total pore volume is 2.84%; the micropore volume pore size distribution curve of the sulfur-doped nanocarbon cage has a distribution peak at 0.62nm, and the mesopore volume pore size distribution curve has two distribution peaks at 3.94nm and 12.3nm, indicating that the sulfur-doped nanocarbon cage is a nanocarbon material with microporous structure and mesoporous structure, and the mesoporous structure is mainly.

[0089] The Raman curve of the sulfur-doped nanocarbon cage is as follows Figure 4 As shown in the figure, we can see obvious D peak and G peak, I D / I G =1.005, indicating that the sulfur-doped nanocarbon cage has a high degree of graphitization.

[0090] Preparation Example 2

[0091] Preparation of sulfur-doped carbon nanocages:

[0092] (1) Preparation of precursor: According to the molar ratio of nickel source (calculated as nickel element), polybasic organic carboxylic acid and sulfur source of 1:1.2:1, 30 g of basic nickel carbonate, 50.37 g of citric acid and 27.8 g of potassium hydrogen sulfate were weighed and added to a beaker containing 50 mL of deionized water, and stirred at 70 ° C to obtain a homogeneous solution, which was further heated and evaporated to dryness to obtain a complex precursor material;

[0093] (2) Calcination: The complex precursor material is placed in a porcelain boat, which is then placed in the constant temperature zone of a tube furnace. Nitrogen gas is introduced at a flow rate of 60 mL / min, and the temperature is raised to 600°C at a rate of 2.5°C / min. After holding the temperature for 2 h, heating is stopped and the product is cooled to room temperature under a nitrogen atmosphere to obtain a pyrolysis product.

[0094] (3) Acid washing: The pyrolysis product was added to a 2.0 M HCl aqueous solution and stirred at 80 °C for 10 h, then filtered and washed with deionized water until the filtrate was neutral. The filter cake was then dried at 140 °C for 2 h to obtain sulfur-doped nanocarbon cages.

[0095] Characterization of basic properties of sulfur-doped nanocarbon cages:

[0096] High-resolution transmission electron microscopy observation and measurement show that the sulfur-doped nanocarbon cage has a spherical or quasi-spherical morphology, and the diameter of the nanocarbon cage is 5-20 nm.

[0097] X-ray photoelectron spectroscopy (XPS) analysis revealed that the surface carbon content of the sulfur-doped nanocarbon cage was 86.89% by mass, the oxygen content was 10.35% by mass, and the sulfur content was 2.76% by mass. The XPS S2p spectrum of the sulfur-doped nanocarbon cage exhibited characteristic sulfur peaks at 161±2 eV, 162-166 eV, and 168±2 eV. Based on the product of peak areas after peak separation, it was calculated that the sulfur content corresponding to the characteristic peak at 162-166 eV accounted for 79.6% of the total sulfur content.

[0098] The BET specific surface area of the sulfur-doped nanocarbon cage was 1096.314 m 2 / g, the specific surface area in micropores is 186.416m 2 / g, accounting for 17.0% of the total specific surface area; the total pore volume of sulfur-doped nanocarbon cages is 2.761 cm 3 / g, micropore volume is 0.087cm 3 / g, accounting for 3.15% of the total pore volume; the micropore volume and pore size distribution curve of the sulfur-doped nanocarbon cage has a distribution peak at 0.63nm, and the mesopore volume and pore size curve has two distribution peaks at 3.7nm and 10nm, indicating that the sulfur-doped nanocarbon cage is a nanocarbon material with microporous structure and mesoporous structure.

[0099] Raman testing shows that the sulfur-doped nanocarbon cage has obvious D peak and G peak, I D / I G =0.823, indicating that the sulfur-doped nanocarbon cage has a certain degree of graphitization.

[0100] Comparative Preparation Example

[0101] (1) Weigh 30 g of basic nickel carbonate and 30 g of citric acid into a beaker containing 30 mL of deionized water, stir at 70° C. to obtain a homogeneous solution, and continue heating and evaporating to dryness to obtain a complex precursor material;

[0102] (2) placing the complex precursor material in a porcelain boat, then placing the porcelain boat in the constant temperature zone of a tube furnace, introducing nitrogen at a flow rate of 200 mL / min, and heating to 600°C at a rate of 10°C / min. After holding the temperature for 2 h, heating was stopped and the mixture was cooled to room temperature under a nitrogen atmosphere to obtain a pyrolysis product;

[0103] (3) The pyrolysis product was added to a 2.0 M HCl aqueous solution and stirred at 80 °C for 10 h, then filtered and washed with deionized water until the filtrate was neutral. The filter cake was then dried at 140 °C for 2 h to obtain a nanocarbon material.

[0104] X-ray photoelectron spectroscopy (XPS) testing revealed the presence of incompletely removed nickel in the nanocarbon material. The mass percentages of various elements on the surface of the nanocarbon material were calculated based on peak areas. The mass percentages of nickel, carbon, and oxygen were 8.26%, 83.11%, and 8.54%, respectively.

[0105] The BET specific surface area of the nanocarbon material was calculated to be 264.968 m 2 / g, the specific surface area in the micropores is 0; the pore volume of the nanocarbon material is 0.677cm 3 / g, the micropore volume is 0; the pore volume and pore size curve of the nano-carbon material has two distribution peaks at 3.86nm and 15nm, indicating that there is no microporous structure in the nano-carbon material.

[0106] Examples 1-3 are used to illustrate capacitor electrodes and methods for preparing the same.

[0107] Example 1

[0108] The sulfur-doped nanocarbon cages, acetylene black, and polytetrafluoroethylene obtained in Preparation Example 1 were mixed in a mass ratio of 8:1:1, and an appropriate amount of anhydrous ethanol was dropped into the mixture. The mixture was thoroughly ground until the slurry was in the state of plasticine. The plasticine-like slurry was stretched and rolled into a uniform thin sheet using a glass rod, and then dried in an oven at 80°C for 3 hours. After complete drying, it was cut into circular electrodes with a diameter of 10 mm. Subsequently, a hydraulic press was used to press the circular electrode onto a stainless steel mesh current collector at a pressure of 10 MPa to obtain a capacitor electrode.

[0109] Example 2

[0110] The sulfur-doped nanocarbon cages and polytetrafluoroethylene obtained in Preparation Example 1 were mixed in a mass ratio of 9:1, an appropriate amount of anhydrous ethanol was added, and the mixture was thoroughly ground until the slurry was in the state of plasticine. The plasticine-like slurry was stretched and rolled into a uniform thin sheet using a glass rod, and then dried in an oven at 80°C for 3 hours. After complete drying, it was cut into circular electrodes with a diameter of 10 mm. Subsequently, a hydraulic press was used to press the circular electrode onto a stainless steel mesh current collector at a pressure of 10 MPa to obtain a capacitor electrode.

[0111] Example 3

[0112] A capacitor electrode was prepared according to the method of Example 1, except that the active material was replaced by the sulfur-doped nanocarbon cage prepared in Preparation Example 2. The remaining raw materials, steps and conditions were the same as those in Example 1 to obtain a capacitor electrode.

[0113] Comparative Example

[0114] A capacitor electrode was prepared according to the method of Example 1, except that the active material was replaced by the nanocarbon material prepared in the comparative preparation example. The remaining raw materials, steps and conditions were the same as those in Example 1 to obtain a capacitor electrode.

[0115] Test Example 1

[0116] This test example is used to test the capacitance performance of capacitor electrodes in aqueous electrolyte.

[0117] Performance Testing: Capacitance performance was tested using a three-electrode system, using the capacitor electrodes prepared in Examples 1-3 and the comparative example as the working electrode, a platinum electrode as the counter electrode, a mercuric oxide electrode as the reference electrode, and a 6 mol / L KOH aqueous solution as the electrolyte. The capacitive performance of the capacitor electrodes was characterized using an electrochemical workstation. The assembled three-electrode system was subjected to constant current charge and discharge tests over a voltage range of -1 V to 0 V (relative to the mercuric oxide electrode). The specific capacitance was recorded at various current densities (0.5-10 A / g).

[0118] The present invention exemplarily provides the cyclic voltammetry curves of the capacitor electrode prepared in Example 1 at different scan rates, such as Figure 5 As shown in the figure, the charge and discharge curves at different current densities are shown in the figure. Figure 6 As shown in the figure, the capacitor electrode prepared in Example 1 has a specific capacitance of 238.5 F / g at a current density of 0.5 A / g, and a specific capacitance of 201 F / g at a current density of 1 A / g. As the current density increases, the specific capacitance shows a downward trend, but at a higher current density (10 A / g), the capacitor electrode can still maintain a specific capacitance of 160 F / g.

[0119] The capacitor electrode prepared in Example 2 has a specific capacitance of 180 F / g at a current density of 1 A / g.

[0120] The capacitor electrode prepared in Example 3 has a specific capacitance of 190 F / g at a current density of 1 A / g.

[0121] The capacitor electrode prepared in the comparative example has a specific capacitance of 120 F / g at a current density of 1 A / g.

[0122] Test Example 2

[0123] This test example is used to illustrate a double-layer supercapacitor and its preparation method, as well as the electrochemical and capacitive properties of the capacitor electrodes.

[0124] Assembly of a double-layer supercapacitor: The capacitor electrodes and cellulose diaphragms prepared in Example 1 and the comparative example were soaked in 1 M tetraethylammonium tetrafluoroborate acetonitrile solution for 0.5 h and then taken out. A 1 M tetraethylammonium tetrafluoroborate acetonitrile solution was used as the electrolyte, and a double-layer supercapacitor was assembled in the order of battery shell (positive electrode) - capacitor electrode - diaphragm - capacitor electrode - battery shell (negative electrode).

[0125] Performance testing:

[0126] The capacitor was charged and discharged at different current densities in the voltage range of 0-2.7V using an electrochemical workstation, and the corresponding specific capacitance was recorded. The charge and discharge curves are shown in Figure 2. Figure 7 The capacitor electrode prepared in Example 1 has a specific capacitance of 88 F / g at a current density of 1 A / g.

[0127] The capacitor electrode prepared in the comparative example has a specific capacitance of 65 F / g at a current density of 1 A / g.

[0128] Test Example 3

[0129] This test example is used to illustrate a lithium-ion capacitor and its preparation method, as well as the electrochemical and capacitive properties of the capacitor electrodes.

[0130] Assembly of lithium ion capacitors: The capacitor electrodes and polypropylene diaphragms prepared in Example 1 and the comparative example were soaked in lithium hexafluorophosphate electrolyte for 0.5 h and then taken out. Lithium hexafluorophosphate was used as the electrolyte and the battery shell (positive electrode) - lithium sheet - diaphragm - capacitor electrode - battery shell (negative electrode) were used to assemble a button-type lithium ion capacitor.

[0131] Performance testing: The button-type lithium-ion capacitors were characterized for specific capacity and rate performance using a blue-electric system. Within a voltage range of 0-3V, they were discharged and then charged at different current densities (0.1-2A / g).

[0132] The present invention exemplarily provides the capacitor electrode prepared in Example 1 as the negative electrode of the lithium ion capacitor, and the corresponding specific capacity at different current densities, such as Figure 8 As shown in the figure, the specific capacity of the button-type lithium-ion capacitor exceeds 900 mAh / g at a current density of 0.1 A / g. Although the specific capacity decreases with increasing current density, it can still reach 300 mAh / g when the current density is increased to 1 A / g. In addition, the specific capacity can still be maintained at 200 mAh / g at a current density of 2 A / g.

[0133] The capacitor electrode prepared in the comparative example had a stabilized specific capacity of only 500 mAh / g at a current density of 0.1 A / g. At a current density of 1 A / g, the specific capacity was only 180 mAh / g. When the current density was increased to 2 A / g, the specific capacity was only 130 mAh / g.

[0134] From the above data analysis, it can be seen that the capacitor electrode prepared by using the capacitor electrode material provided by the present invention, when applied to a supercapacitor, exhibits good rate performance, high specific capacity and high specific capacitance.

[0135] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A capacitor electrode material comprising an active material, a conductive agent, and a binder, wherein: The active material is a sulfur-doped nanocarbon cage having a microporous structure and a mesoporous structure, and the BET specific surface area of the sulfur-doped nanocarbon cage is greater than 500 m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 30%; the total pore volume of the sulfur-doped nanocarbon cage is greater than 1cm 3 / g, the proportion of micropore volume to total pore volume is less than 15%; the mass percentage of carbon on the surface of the sulfur-doped nanocarbon cage measured by X-ray photoelectron spectroscopy is 80-98%, and the mass percentage of sulfur is 0.1-10%; The mass percentage of oxygen on the surface of the nanocarbon cage is measured by X-ray photoelectron spectroscopy and is 2-15%.

2. The capacitor electrode material according to claim 1, wherein The BET specific surface area of the sulfur-doped nanocarbon cage is 500-1600 m 2 / g, the ratio of the specific surface area in the micropores to the total specific surface area is less than 20%; the total pore volume of the sulfur-doped nanocarbon cage is greater than 1.4cm 3 / g, the proportion of micropore volume to total pore volume is less than 10%; the mass percentage of carbon on the surface of the sulfur-doped nanocarbon cage measured by X-ray photoelectron spectroscopy is 84-95%, and the mass percentage of sulfur is 0.2-5%.

3. The capacitor electrode material according to claim 1, wherein In the pore size distribution curve of the sulfur-doped nanocarbon cage, there is a micropore distribution peak at 0.59-0.63 nm, and there are two mesopore distribution peaks at 2.73-4.1 nm and 3.877-15.6 nm.

4. The capacitor electrode material according to claim 1, wherein The sulfur-doped nanocarbon cage has a spherical or quasi-spherical morphology.

5. The capacitor electrode material according to any one of claims 1 to 4, wherein: The diameter of the sulfur-doped nanocarbon cage is 2-200 nm.

6. The capacitor electrode material according to claim 5, wherein The diameter of the sulfur-doped nanocarbon cage is 3-50 nm.

7. The capacitor electrode material according to any one of claims 1 to 4, wherein: In the Raman curve of the sulfur-doped nanocarbon cage, I D / I G The range is 0.5-1.

5.

8. The capacitor electrode material according to claim 7, wherein In the Raman curve of the sulfur-doped nanocarbon cage, I D / I G The range is 0.5-1.

1.

9. The capacitor electrode material according to any one of claims 1 to 4, wherein: Based on the total amount of sulfur on the surface of the sulfur-doped nanocarbon cage, the mass percentage of sulfur determined by the characteristic peak corresponding to 162-166 eV in the X-ray photoelectron spectrum of the sulfur-doped nanocarbon cage is 2-90%.

10. The capacitor electrode material according to claim 9, wherein Based on the total amount of sulfur on the surface of the sulfur-doped nanocarbon cage, the mass percentage of sulfur determined by the characteristic peak corresponding to 162-166 eV in the X-ray photoelectron spectrum of the sulfur-doped nanocarbon cage is 70-88%.

11. The capacitor electrode material according to any one of claims 1 to 4, wherein: The mass ratio of the active material, the conductive agent and the adhesive is 7-18:0-3:

1.

12. The capacitor electrode material according to claim 11, wherein The mass ratio of the active material, the conductive agent and the adhesive is 8-18:1-3:

1.

13. The capacitor electrode material according to any one of claims 1 to 4, wherein: The conductive agent is selected from at least one of acetylene black, Ketjen black, graphene and carbon nanotubes.

14. The capacitor electrode material according to claim 13, wherein The conductive agent is acetylene black.

15. The capacitor electrode material according to any one of claims 1 to 4, wherein: The binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber emulsion and acrylonitrile copolymer aqueous dispersion.

16. The capacitor electrode material according to claim 15, wherein The adhesive is polytetrafluoroethylene.

17. A capacitor electrode comprising a current collector and an electrode material coated and / or filled on the current collector, characterized in that: The electrode material is the capacitor electrode material according to any one of claims 1 to 16.

18. The capacitor electrode according to claim 17, wherein The current collector is selected from any one of stainless steel mesh, nickel foam, aluminum foil and copper foil.

19. The capacitor electrode according to claim 18, wherein The current collector is a stainless steel mesh.

20. A method for preparing a capacitor electrode, comprising coating and / or filling a slurry containing a capacitor electrode material and a solvent on a current collector, drying, and rolling or not rolling, wherein: The capacitor electrode material is the capacitor electrode material according to any one of claims 1 to 16.

21. The preparation method according to claim 20, wherein The solvent is anhydrous ethanol and / or N-methylpyrrolidone.

22. The preparation method according to claim 21, wherein The solvent is anhydrous ethanol.

23. A supercapacitor comprising a core and an electrolyte, wherein the core and the electrolyte are sealed in a battery housing, the core comprising an electrode and a diaphragm, characterized in that: The electrode is the capacitor electrode according to any one of claims 17 to 19 or is a capacitor electrode prepared according to the preparation method according to any one of claims 20 to 22.

24. The supercapacitor according to claim 23, wherein The supercapacitor is a lithium ion capacitor or a double-layer supercapacitor.

25. The supercapacitor according to claim 23, wherein The battery housing is a button-type battery housing.

26. The supercapacitor according to claim 23, wherein The electrolyte is an aqueous electrolyte or an organic electrolyte.

27. The supercapacitor according to claim 26, wherein The electrolyte is any one of a potassium hydroxide aqueous solution, a lithium hexafluorophosphate electrolyte, and a tetraethylammonium tetrafluoroborate acetonitrile solution.

28. The supercapacitor according to any one of claims 23 to 27, wherein: When the supercapacitor is a double-layer supercapacitor, the electrolyte is an aqueous electrolyte.

29. The supercapacitor according to claim 28, wherein When the supercapacitor is a double-layer supercapacitor, the electrolyte is a potassium hydroxide aqueous solution or a tetraethylammonium tetrafluoroborate acetonitrile solution.

30. The supercapacitor according to any one of claims 23 to 27, wherein: When the supercapacitor is a lithium ion capacitor, the electrolyte is an organic electrolyte.

31. The supercapacitor according to claim 30, wherein When the supercapacitor is a lithium ion capacitor, the electrolyte is a lithium hexafluorophosphate electrolyte.

32. The supercapacitor according to any one of claims 23 to 27, wherein: The separator is selected from any one of polyethylene, polypropylene and cellulose separators.

33. The supercapacitor according to claim 32, wherein When the supercapacitor is a double-layer supercapacitor, the separator is a cellulose separator.

34. The supercapacitor according to claim 32, wherein When the supercapacitor is a lithium ion capacitor, the diaphragm is polypropylene.

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