CN115708180A - Nitrogen and sulfur doped nano carbon material and preparation method thereof, capacitor electrode material, capacitor electrode and preparation method thereof, and capacitor - Google Patents
Nitrogen and sulfur doped nano carbon material and preparation method thereof, capacitor electrode material, capacitor electrode and preparation method thereof, and capacitor Download PDFInfo
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Abstract
The invention relates to the technical field of electrochemical energy storage, and discloses a nitrogen and sulfur doped nano carbon material which has a microporous structure and a mesoporous structure, wherein the BET specific surface area of the nano carbon material is 800-2000m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 50-85%; the total pore volume of the nano carbon material is more than 1cm 3 The proportion of the micropore volume to the total pore volume is 30-50%; measuring the mass percentage of carbon on the surface of the nano carbon material by X-ray photoelectron spectroscopy to be 70-95%; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; the carbon content in the nano carbon material measured by an element analyzer is 30-60% by mass; mass percent of nitrogenThe amount is 1-15%; the mass percentage of the sulfur is 1-15%. The nitrogen and sulfur doped nano carbon material as an electrode of a double electric layer super capacitor shows excellent capacitance performance, and as a negative electrode of a lithium ion capacitor, shows higher specific capacity.
Description
Technical Field
The invention relates to the technical field of electrochemical energy storage, in particular to a nitrogen and sulfur doped nano carbon material and a preparation method thereof, a capacitor electrode material, a capacitor electrode and a preparation method thereof and a capacitor.
Background
With the exhaustion of fossil energy and the aggravation of environmental problems, new energy has become a global focus of attention in order to ensure sustainable development. Due to the continuous deep utilization of energy, the fields of energy storage devices such as lithium ion batteries and super capacitors have been developed greatly in the near field. However, with the growth of the electric vehicle market, higher requirements are placed on the energy density and power density of the energy storage device. The conventional lithium ion battery has a high energy density, but has a low power density, and cannot meet high power output. The super capacitor is a novel green energy storage device between a traditional capacitor and a battery, and has the characteristics of short charging time, long service life, good temperature characteristic, energy conservation, environmental protection and the like. Compared with lithium ion batteries, supercapacitors have higher power density and cycle stability. The performance of the super capacitor is improved, and the electrode material is a key factor. Currently, carbon materials, transition metal oxides, hydroxides, conductive polymers, and the like are commonly used as electrode materials. The carbon material mainly adsorbs electrolyte ions through a pore structure to realize energy storage. An electric double layer supercapacitor composed of a carbon material exhibits good charge and discharge capacity and excellent cycle stability. Currently, porous activated carbon synthesized from biomass or other raw materials is the most widely used in electric double layer capacitors. The porous activated carbon has a high specific surface area and a large amount of microporous structures, and shows excellent specific capacitance. Although the activated carbon has abundant raw material sources and low cost, the larger specific surface area often results in a supercapacitor with lower volume energy density and consumes more electrolyte.
Although the super capacitor has very high power density and cycle stability, the energy density is low, and the requirement cannot be met. The lithium ion capacitor is used as a combination of the lithium ion battery and the super capacitor, and the defects of the lithium ion battery and the super capacitor are effectively overcome. The lithium ion capacitor is composed of a positive electrode material of an electric double layer capacitor and a negative electrode material of a lithium ion battery, so that the lithium ion capacitor not only has higher power density, but also keeps higher energy density. At present, the most commonly used graphite materials for the negative electrode of the lithium ion capacitor include natural graphite, artificial graphite and the like. Although the graphite material is widely applied to the lithium ion battery, the rate capability of the graphite material is low, and the graphite material has a kinetic matching problem with a positive electrode material in a lithium ion capacitor. Therefore, the preparation of the novel carbon cathode material further improves the capacity, the rate capability and the cycle life, and is an important means for solving the problem of matching the anode and the cathode of the lithium ion capacitor.
In order to overcome the defects of the electrode materials of the double electric layer super capacitor and the lithium ion capacitor, various forms of porous carbon materials are developed, including graphene, carbon nanotubes, template carbon, nano carbon cages and other materials. Due to the self-regular shape, the adjustable pore structure and the excellent conductivity, the nano carbon cage has better application prospect in the field of energy storage. The synthesis method of the nano carbon cage comprises an activation method, a template method, a hydrothermal method, a high-temperature pyrolysis method, a chemical vapor deposition method, a carbonization gel method and the like.
In addition, the doping of heteroatoms such as nitrogen, sulfur and the like can effectively improve the conductivity and wettability of the carbon material, and meanwhile, pseudocapacitance can be introduced through redox reaction to improve the overall capacity. There are two main ways of doping heteroatoms. One is a post-treatment process in which the carbon material is activated at high temperature in a heteroatom-containing gas or co-heated with a heteroatom organic. Another method is to use macromolecule containing hetero atom as raw material, and part of hetero atom is remained in carbonization process. The heteroatom doping reported at present mainly focuses on single atom doping, and the polyatomic doping has the problems of complex process, high cost and the like.
The nitrogen and sulfur doping has important significance for improving the electrochemical performance of the nano carbon cage. However, the doping of various elements is realized at the same time, the structural regularity of the material is ensured, and the porous structure and the high specific surface area are provided, so that certain difficulty is brought.
Disclosure of Invention
The invention aims to solve the problems of poor specific capacity, rate capability and cycle performance of a carbon material existing in the prior art, and provides a nitrogen and sulfur doped nano carbon material and a preparation method thereof, a capacitor electrode material, a capacitor electrode and a preparation method thereof and a capacitor, so as to improve the specific capacity, rate capability and cycle performance of the carbon material.
In order to achieve the above objects, a first aspect of the present invention provides a nitrogen and sulfur doped nanocarbon material having a microporous structure and a mesoporous structure, the nanocarbon material having a BET specific surface area of 800 to 2000m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 50-85%; the total pore volume of the nano carbon material is more than 1cm 3 (ii)/g, the proportion of the micropore volume to the total pore volume is 30-50%; measuring the mass percentage of carbon on the surface of the nano carbon material by X-ray photoelectron spectroscopy to be 70-95%; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; the carbon content in the nano carbon material measured by an element analyzer is 30-60% by mass; the mass percentage of nitrogen is 1-15%; the mass percentage of the sulfur is 1-15%.
The invention provides a preparation method of a nitrogen and sulfur doped nano carbon material, which comprises the following steps:
(1) Preparing a precursor: forming a homogeneous phase solution by using a nickel salt, a nitrogen-containing organic acid, a sulfur-containing potassium salt and a solvent, and then removing the solvent in the homogeneous phase solution to obtain a precursor, wherein the nitrogen-containing organic acid is ethylenediamine tetraacetic acid and/or 2, 5-pyridinedicarboxylic acid, and the sulfur-containing potassium salt is potassium sulfate and/or potassium bisulfate;
(2) Roasting: roasting the precursor obtained in the step (1) under the protection of inert atmosphere to obtain a pyrolysis product;
(3) Acid washing: providing an aqueous solution containing the pyrolysis product obtained in the step (2), carrying out contact reaction with acid, and then carrying out solid-liquid separation, washing and drying.
The third aspect of the present invention provides a capacitor electrode material, which contains an active material, a conductive agent and a binder, wherein the active material is the nitrogen-and sulfur-doped nanocarbon material according to the first aspect or the nitrogen-and sulfur-doped nanocarbon material prepared by the preparation method according to the second aspect.
The invention provides a capacitor electrode, which comprises a current collector and an electrode material coated and/or filled on the current collector, wherein the electrode material is the electrode material of the third aspect.
In a fifth aspect, the present invention provides a method for preparing a capacitor electrode, the method comprising coating and/or filling a slurry containing an active material, a conductive agent, a binder and a solvent on a current collector, drying, rolling or not, wherein the active material is the nitrogen-and sulfur-doped nanocarbon material according to the first aspect or the nitrogen-and sulfur-doped nanocarbon material prepared by the method according to the second aspect.
The invention provides a capacitor, which comprises a button-type shell, electrodes, a diaphragm and electrolyte, wherein the electrodes comprise the capacitor electrode of the fourth aspect or the capacitor electrode prepared by the preparation method of the fifth aspect.
Through the technical scheme, the invention has the following advantages:
(1) The nitrogen and sulfur doped nano carbon material provided by the invention has a microporous structure and a mesoporous structure, and the BET specific surface area is 800-2000m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 50-85%; total pore volume greater than 1cm 3 (ii)/g, the proportion of the micropore volume to the total pore volume is 30-50%; measuring the mass percentage of carbon on the surface of the nano carbon material by X-ray photoelectron spectroscopy to be 70-95%; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; the carbon content of the nano carbon material is 30-60% by mass measured by an element analyzer; the mass percentage of nitrogen is 1-15%; the mass percentage of the sulfur is 1-15%. The nano carbon material has a hierarchical pore structure mainly comprising micropores, abundant three-dimensional transmission channels and a larger specific surface area, nitrogen and sulfur atoms in the nano carbon material have a synergistic effect, and the lithium storage performance of the material can be effectively improved through double energy storage of physical adsorption and ion insertion;
(2) According to the preparation method of the nitrogen and sulfur doped nano carbon material, the nitrogen source and the sulfur source are directly added in the preparation process of the precursor, and in the process of forming the nano carbon material with the hollow cage-shaped and sheet-shaped mixed morphology, the doping of nitrogen and sulfur and the pore-forming activation are simultaneously realized, so that the specific surface area of the nano carbon material is effectively improved, the process is simple, and the production is easy;
(3) When the nitrogen and sulfur doped nano carbon material provided by the invention is used as a lithium ion capacitor cathode, the stable specific capacity exceeds 800mAh/g under the current density of 0.1A/g; when the current density is increased to 2A/g, the specific capacity can reach 300mAh/g at most; under the current density of 1A/g, after 1000 cycles, the capacity retention rate can reach 80% at most, and the excellent specific capacity, rate capability and cycle performance are shown; when the aqueous electrolyte is used as the electrode of the electric double layer super capacitor, the specific capacitance of a single electrode can reach 358F/g at the current density of 0.5A/g at most, and the electrode shows excellent capacitance performance.
Drawings
FIG. 1 is a transmission electron microscope image of a nitrogen and sulfur doped nanocarbon material prepared in preparation example 1;
FIG. 2 is a high-resolution transmission electron microscope image of the nitrogen-and sulfur-doped nanocarbon material prepared in preparation example 1;
FIG. 3 is N of the N and S doped nano carbon material prepared in preparation example 1 2 Adsorption-desorption isotherms;
FIG. 4 is a full scan XPS graph of a nitrogen and sulfur doped nanocarbon material prepared in preparation example 1;
FIG. 5 is an XPS high resolution S2p spectrum of the nitrogen and sulfur doped nano carbon material prepared in preparation example 1;
FIG. 6 is a Raman spectrum of the nitrogen-and sulfur-doped nanocarbon material prepared in preparation example 1;
FIG. 7 is a cyclic voltammogram of the nitrogen and sulfur doped nanocarbon material prepared in preparation example 1 at different scanning rates;
FIG. 8 is a constant current charge and discharge curve of the nitrogen and sulfur doped nanocarbon material prepared in preparation example 1;
FIG. 9 is a graph of the capacity and coulombic efficiency at different current densities for the capacitor electrodes prepared in example B1;
FIG. 10 is a graph of the capacity and coulombic efficiency at different current densities for the capacitor electrodes prepared in example B2;
FIG. 11 is a graph of capacity and coulombic efficiency at different current densities for the capacitor electrode prepared in example B3;
FIG. 12 is a graph of the cycling performance at a current density of 1A/g for the capacitor electrode prepared in example B1.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a nitrogen and sulfur doped nano carbon material, which has a microporous structure and a mesoporous structure, and has a BET specific surface area of800-2000m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 50-85%; the total pore volume of the nanocarbon material is more than 1cm 3 (ii)/g, the proportion of the micropore volume to the total pore volume is 30-50%; the mass percentage of carbon on the surface of the nano carbon material is 70-95% by X-ray photoelectron spectroscopy; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; the carbon content in the nano carbon material measured by an element analyzer is 30-60% by mass; the mass percentage of nitrogen is 1-15%; the mass percentage of the sulfur is 1-15%.
In some embodiments of the present invention, the nanocarbon material has a microporous structure and a mesoporous structure, and a BET specific surface area of the nanocarbon material is 800 to 2000m 2 The ratio of the specific surface area in micropores to the total specific surface area is 50-85%, and preferably, the BET specific surface area of the nano carbon material is 800-1600m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 70-85%.
In some embodiments of the invention, the total pore volume of the nanocarbon material is greater than 1cm 3 (ii)/g, the ratio of micropore volume to total pore volume is 30 to 50%, preferably, the total pore volume of the nanocarbon material is greater than 1.45cm 3 The proportion of the micropore volume to the total pore volume is from 35 to 50%.
In some embodiments of the present invention, the carbon content of the nanocarbon material surface is 70 to 95% by mass as measured by X-ray photoelectron spectroscopy; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; preferably, the mass percentage of carbon on the surface of the nano carbon material is 79-95% as measured by X-ray photoelectron spectroscopy; the mass percentage of nitrogen is 5-11%; the mass percentage of the sulfur is 0.2-5%.
In some embodiments of the invention, the carbon content of the nanocarbon material, as measured by an elemental analyzer, is 30-60% by mass; the mass percentage of nitrogen is 1-15%; the mass percentage of the sulfur is 1-15%; preferably, the carbon content in the nano carbon material measured by an element analyzer is 35-55% by mass; the mass percentage of nitrogen is 5-15%; the mass percentage of the sulfur is 2-15%.
In the present invention, the pore structure properties of the material were examined by the BET test method. Specifically, a Quantachrome AS-6B type analyzer is adopted for measurement, and the specific surface area and the pore volume of the material are obtained by a Brunauer-Emmett-Taller (BET) method.
In some embodiments of the present invention, preferably, the nitrogen and sulfur doped nanocarbon material may further contain an oxygen element, which may be in various forms contained in the graphitized carbon layer formed during the preparation process of the nitrogen and sulfur doped nanocarbon material. Preferably, the mass percent of oxygen on the surface of the nano carbon material is 3-15%, preferably 5-14%, measured by X-ray photoelectron spectroscopy. Preferably, the mass percentage of oxygen in the nanocarbon material is 25 to 35%, preferably 28 to 32%, as measured by an elemental analyzer.
In the invention, the contents of carbon elements, nitrogen elements, sulfur elements and oxygen elements on the surface of the nitrogen and sulfur doped nano carbon material are measured by adopting X-ray photoelectron spectroscopy; the contents of carbon element, nitrogen element, sulfur element and oxygen element in the nitrogen and sulfur doped nano carbon material are measured by adopting an element analysis method.
In some embodiments of the present invention, preferably, the nanocarbon material has a mixed morphology of hollow cage shape and sheet shape, and the diameter of the hollow structure of the nanocarbon material is 5 to 50nm. The morphology of the nano carbon material can be determined by observing through a high-resolution transmission electron microscope, and the diameter of the hollow structure of the material is obtained by measuring through an electron microscope picture by adopting a transmission electron microscope method.
In some embodiments of the present invention, it is preferable that the ratio of the intensities of the D peak and the G peak (i.e., I) in the raman curve of the nanocarbon material D /I G ) Is 0.5 to 1.5, preferably 0.5 to 1. The nano carbon material has obvious D peak and G peak, has a certain graphitization degree, and can be observed to have a hollow structure and a graphitized carbon layer by using a high-resolution transmission electron microscope. The graphitized carbon layer of the nano carbon material can play a role in buffering when lithium ions are embedded, and the stability of the material is effectively improved.
In the present invention, the term "nitrogen" in the "nitrogen and sulfur doped nanocarbon material" refers to nitrogen element, and the term "sulfur" refers to sulfur element, and specifically refers to nitrogen element and sulfur element in various forms contained in the graphitized carbon layer formed during the preparation process of the nitrogen and sulfur doped nanocarbon material.
In the present invention, the term "graphitized carbon layer" refers to a carbon structure in which a layered structure is clearly observed under a high-resolution transmission electron microscope, not to an amorphous structure.
In the present invention, the term "mesoporous" is defined as a pore having a pore diameter ranging from 2 to 50nm. Pores with a pore diameter of less than 2nm are defined as "micropores".
The invention provides a preparation method of a nitrogen and sulfur doped nano carbon material, which comprises the following steps:
(1) Preparing a precursor: forming a homogeneous phase solution by using a nickel salt, a nitrogen-containing organic acid, a sulfur-containing potassium salt and a solvent, and then removing the solvent in the homogeneous phase solution to obtain a precursor, wherein the nitrogen-containing organic acid is ethylenediamine tetraacetic acid and/or 2, 5-pyridinedicarboxylic acid, and the sulfur-containing potassium salt is potassium sulfate and/or potassium bisulfate;
(2) Roasting: roasting the precursor obtained in the step (1) under the protection of inert atmosphere to obtain a pyrolysis product;
(3) Acid washing: providing an aqueous solution containing the pyrolysis product obtained in the step (2), carrying out contact reaction with acid, and then carrying out solid-liquid separation, washing and drying.
In some embodiments of the invention, the method for preparing the nitrogen and sulfur doped nano carbon material uses nitrogen-containing organic acid as a carbon source and a nitrogen source, uses sulfur-containing potassium salt as a sulfur source and an activator, uses nickel salt as a catalyst and a template agent, and the prepared nitrogen and sulfur doped nano carbon material has a microporous structure and a mesoporous structure, and the BET specific surface area of the nano carbon material is 800-2000m 2 The proportion of the specific surface area in the micropores accounts for 50-85% of the total specific surface area; the total pore volume of the nano carbon material is more than 1cm 3 (ii)/g, the proportion of the micropore volume to the total pore volume is 30-50%; the nano carbon material has larger specific surface area and abundanceA rich pore structure, and a quantity of graphitized carbon layers.
In some embodiments of the present invention, the method for forming the homogeneous solution is not particularly limited, and the homogeneous solution may be formed by heating, and more preferably by heating and stirring, for example. The heating temperature and the stirring rate are not particularly limited in the present invention, so long as the homogeneous solution can be formed.
In some embodiments of the present invention, preferably, in step (1), the precursor is obtained by dissolving a nickel salt, a nitrogen-containing organic acid and a sulfur-containing potassium salt in a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution. The type of the solvent is not particularly limited, and is based on the ability to form a homogeneous solution, and for example, the solvent may be water, ethanol, or the like, and is preferably water; the amount of the solvent is not particularly limited, and is also based on the ability to form a homogeneous solution. The solvent in the homogeneous solution may be removed by direct evaporation, and the temperature and process of evaporation may be according to the known art, e.g. drying in an oven to remove the solvent from the homogeneous solution.
In some embodiments of the present invention, in step (1), the nickel salt may be a nickel-containing inorganic salt conventionally used in the art, preferably, the nickel salt may be selected from one or more of basic nickel carbonate, nickel acetate, nickel chloride, nickel nitrate and nickel sulfate, preferably basic nickel carbonate.
In some embodiments of the present invention, preferably, the nitrogen-containing organic acid is ethylenediaminetetraacetic acid and/or 2, 5-pyridinedicarboxylic acid, preferably ethylenediaminetetraacetic acid.
In some embodiments of the present invention, preferably, the sulfur-containing potassium salt may be potassium sulfate and/or potassium bisulfate, preferably potassium bisulfate.
In some embodiments of the present invention, it is preferable that the ratio of the amounts of the nickel salt, the nitrogen-containing organic acid and the sulfur-containing potassium salt is 1:0.5-1:0.5-2, preferably 1:0.7-1:0.5-1, most preferably 1:1:1. the adoption of the preferred embodiment is more beneficial to obtain higher nitrogen and sulfur incorporation amount and high specific surface area.
In some embodiments of the present invention, preferably, in the step (2), the inert atmosphere is provided by at least one of nitrogen, argon, neon and helium, preferably a nitrogen atmosphere and/or an argon atmosphere.
In some embodiments of the invention, the method of firing comprises: heating to 400-1000 deg.C at a heating rate of 2-10 deg.C/min, preferably 5-10 deg.C/min, heating to 600-800 deg.C, calcining at constant temperature for 1-8 hr, preferably 2-4 hr, and cooling to room temperature at a cooling rate of 1-10 deg.C/min, preferably 3-5 deg.C/min.
In some embodiments of the present invention, preferably, in step (3), the acid washing may be performed with various inorganic acids and/or organic acids as long as metal elements such as nickel, potassium, etc. in the material can be removed, for example, the acid used for the acid washing may be selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid, and acetic acid, and is preferably concentrated hydrochloric acid. The amount of the acid used is not particularly limited, and may be any amount as long as it can remove metal elements such as nickel and potassium in the material. In order to remove the metal elements such as nickel and potassium from the material more effectively, it is preferable to use an excess amount of acid in the acid washing.
In some embodiments of the invention, preferably, the temperature of the acid wash is 80 to 120 ℃, preferably 90 to 100 ℃; the contact reaction time is 6-24h, preferably 8-12h.
In some embodiments of the present invention, the washing is used to remove acid remaining on the nitrogen and sulfur doped nanocarbon material due to the acid washing process, and thus, various water washing methods capable of washing the nitrogen and sulfur doped nanocarbon material to be neutral are suitable for the present invention.
In some embodiments of the invention, drying is used to remove water from the nitrogen and sulfur doped nanocarbon material. The drying can be carried out under normal pressure or under reduced pressure. The conditions for drying may include: the temperature is 100-120 ℃, and the time is 6-10h.
In some embodiments of the present invention, preferably, the nickel salt, the nitrogen-containing organic acid and the sulfur-containing potassium salt are used in amounts such that the mass percentage of carbon on the surface of the prepared nitrogen-and sulfur-doped nanocarbon material is 70-95%; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; the carbon in the nano carbon material accounts for 30-60% by mass; the mass percentage of nitrogen is 1-15%; the mass percentage of the sulfur is 1-15%.
In some embodiments of the present invention, preferably, the nickel salt, the nitrogen-containing organic acid and the sulfur-containing potassium salt are used in amounts such that the mass percentage of carbon on the surface of the prepared nitrogen-and sulfur-doped nanocarbon material is 79-95%; the mass percentage of nitrogen is 5-11%; the mass percentage of the sulfur is 0.2-5%; the mass percentage of carbon in the nano carbon material is 35-55%; the mass percentage of nitrogen is 5-15%; the mass percentage of the sulfur is 2-15%.
The third aspect of the present invention provides a capacitor electrode material, which contains an active material, a conductive agent and a binder, wherein the active material is the nitrogen-and sulfur-doped nanocarbon material according to the first aspect or the nitrogen-and sulfur-doped nanocarbon material prepared by the preparation method according to the second aspect.
In some embodiments of the present invention, the content and type of the conductive agent are known to those skilled in the art, and the conductive agent may be selected from one or more of acetylene black, ketjen black, graphene, and carbon nanotubes. Acetylene black is preferred as the conductive agent in the present invention.
In some embodiments of the present invention, the binder is an adhesive, and the adhesive may be any adhesive known in the art that can be used for capacitors. May be selected from one or more of a fluorine-containing resin and/or a polyolefin compound, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose, polyvinyl alcohol, styrene-butadiene rubber emulsion, acrylonitrile copolymer aqueous dispersion, preferably Polytetrafluoroethylene (PTFE) and/or polyvinylidene fluoride (PVDF).
In some embodiments of the present invention, it is preferable that the mass ratio of the nitrogen-doped nanocarbon material to the sulfur-doped nanocarbon material to the conductive agent to the binder is 7 to 18:1-3:1, for example, may be 9:0.5:0.5, 8:1:1. 8:1.5: 0.5, 7:2:1 and any two of these values in the range, preferably 8:1:1.
in some embodiments of the present invention, the current collector may be any current collector known to those skilled in the art, such as a stainless steel mesh, an aluminum foil, a copper foil, etc., and the stainless steel mesh or the copper foil is selected as the current collector in the present invention.
The fourth aspect of the present invention provides a capacitor electrode, which comprises a current collector and an electrode material coated and/or filled on the current collector, wherein the electrode material is the electrode material described in the third aspect.
Since the present invention relates only to the improvement of the electrode active material, when the nitrogen and sulfur doped nanocarbon material is applied to a capacitor, other compositions and structures of the capacitor are not particularly limited.
In a fifth aspect, the present invention provides a method for preparing a capacitor electrode, the method comprising coating and/or filling a current collector with a slurry containing an active material, a conductive agent, a binder and a solvent, drying, rolling or not, wherein the active material is the nitrogen and sulfur doped nanocarbon material according to the first aspect or the nitrogen and sulfur doped nanocarbon material prepared by the preparation method according to the second aspect.
According to a preferred embodiment of the present invention, the method for preparing the capacitor electrode comprises:
mixing nitrogen and sulfur doped nano carbon materials, a conductive agent and a binder, grinding uniformly, mixing with a solvent to form slurry, then uniformly coating the slurry on a current collector, drying and cutting into the electrode plate.
According to another preferred embodiment of the present invention, the method for preparing the capacitor electrode comprises:
mixing nitrogen and sulfur doped nano carbon materials, a conductive agent and a binder, uniformly grinding, mixing with a solvent to form slurry, continuously grinding until the slurry is in a plasticine state, extending the plasticine-state slurry into uniform sheets, drying, cutting and pressing onto a current collector to obtain the electrode plate.
In some embodiments of the present invention, the solvent may be any solvent known in the art that can be used in the preparation of capacitor electrodes, for example, ethanol and/or N-methylpyrrolidone, preferably N-methylpyrrolidone. The amount of solvent used is such that the desired coating slurry can be formed.
The invention in a sixth aspect provides a capacitor, which comprises a battery shell, electrodes, a diaphragm and electrolyte, wherein the electrodes comprise the capacitor electrode in the fourth aspect or the capacitor electrode prepared by the preparation method in the fifth aspect.
In some embodiments of the present invention, the electrolyte may be an electrolyte conventionally used in the art and suitable for a capacitor, and for example, an aqueous electrolyte and/or an organic electrolyte may be used, and an aqueous electrolyte is particularly preferable.
In some embodiments of the present invention, preferably, the capacitor is a lithium ion capacitor or an electric double layer supercapacitor.
In some embodiments of the present invention, the lithium ion capacitor uses a metal lithium sheet as a positive electrode, and the electrolyte used is a lithium hexafluorophosphate electrolyte.
In some embodiments of the present invention, the capacitor uses a separator having electrical insulation properties and liquid retention properties, disposed between electrodes, and sealed together with the electrodes in a battery case. The separator may be any separator commonly used in the art, such as polyethylene, polypropylene, modified polyethylene felt, modified polypropylene felt, microglass felt, vinylon felt, or a composite film of nylon felt and wettable polyolefin microporous membrane, which are manufactured by various manufacturers known to those skilled in the art, and the like. The invention selects a water system diaphragm and a cellulose diaphragm as diaphragms of double super capacitors, and a polypropylene diaphragm as a diaphragm of a lithium ion capacitor.
The present invention will be described in detail below by way of examples.
The surface morphology of the material was characterized by High Resolution Transmission Electron Microscopy (HRTEM). The type of the adopted high-resolution transmission electron microscope is JEM-2100 (Japanese electronic Co., ltd.), and the testing conditions of the high-resolution transmission electron microscope are as follows: the acceleration voltage was 200kV. The diameter of the hollow cage-like structure of the material was measured by electron microscopy.
The pore structure properties of the material were examined by the BET test method. Specifically, a Quantachrome AS-6B type analyzer is adopted for measurement, the specific surface area and the pore volume of the material are obtained by a Brunauer-Emmett-Taller (BET) method, a mesoporous distribution curve is obtained by calculating a desorption curve according to a Barrett-Joyner-Halenda (BJH) method, and a micropore pore size distribution curve is obtained by calculating an isothermal curve according to a Horvath-Kawazoe (HK) method.
The contents of elements on the surface of the material and the contents of various nitrogen, oxygen and sulfur species are measured by X-ray photoelectron spectroscopy (XPS), the X-ray photoelectron spectroscopy is tested on an ESCALB 250 type X-ray photoelectron spectrometer which is provided with Thermo Avantage V5.926 software and manufactured by Thermo Scientific company, an excitation source is monochromatized Al K alpha X ray, the energy is 1486.6eV, the power is 150W, the penetrating energy used by narrow scanning is 30eV, and the basic vacuum during analysis and test is 6.53 multiplied by 10 -9 mbar, electron binding energy was corrected with the C1s peak of elemental carbon (284.6 eV), data processed on Thermo Avantage software, and quantified in the analysis module using the sensitivity factor method. The materials were dried at a temperature of 150 c and 1 atm under a helium atmosphere for 3 hours before testing.
The content of carbon, hydrogen, nitrogen, sulfur and other elements in the material is measured by an Elementar Micro Cube element analyzer by using a combustion method, specifically, the material is combusted at high temperature in the presence of oxygen, and C, H, N and S in the material are respectively converted into CO 2 、H 2 O、N 2 、SO 2 . After the interference factors are removed, the reaction gas is carried by the carrier gas to enter a chromatographic column for separation, and finally the reaction gas is detected by a thermal conductivity cell. The oxygen element is analyzed by converting oxygen in a sample into CO under the action of a carbon catalyst by utilizing pyrolysis, and then detecting the CO by adopting TCD.
The visible laser Raman measurement method adopted by the Raman test utilizes a 532 light source to carry out Raman characterization on the functional groups of the material, and a characteristic spectrogram is given.
Preparation examples 1 to 3 are provided to illustrate nitrogen and sulfur doped nanocarbon materials and methods for preparing the same.
Preparation example 1
(1) Preparing a precursor: according to the molar ratio of nickel salt (calculated by nickel element), nitrogen-containing organic acid and sulfur-containing potassium salt of 1:1: weighing 10g of basic nickel carbonate and 20.08g of ethylenediamine tetraacetic acid, dissolving the basic nickel carbonate and the ethylenediamine tetraacetic acid in 150mL of deionized water, uniformly stirring to obtain a solution, then weighing 9.36g of potassium bisulfate, adding the solution into the solution, heating and stirring at 95 ℃ for 4 hours, placing the solution in an oven for drying to obtain 28g of precursor, and grinding the precursor into powder for later use;
(2) Roasting: weighing 10g of precursor in a porcelain boat, then placing the porcelain boat in a tubular roasting furnace, heating to 650 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, roasting at constant temperature for 4h, and finally cooling to room temperature at a cooling rate of 5 ℃/min to obtain 3.4g of pyrolysis product;
(3) Dissolving 3.4g of pyrolysis product in 50mL of deionized water, uniformly stirring, adding 8mL of concentrated hydrochloric acid with the mass fraction of 37%, heating to 105 ℃, stirring for 12 hours, cooling to room temperature, carrying out suction filtration, washing to be neutral, putting the obtained product in an oven, and drying overnight to obtain 600mg of nitrogen and sulfur doped nano carbon material.
The transmission electron microscope image of the nitrogen and sulfur doped nano carbon material is shown in figure 1, the high-resolution transmission electron microscope image is shown in figure 2, and as can be seen from figures 1 and 2, the nano carbon material has a mixed morphology of hollow cage shape and sheet shape, and the diameter of a hollow structure is 5-50nm;
n of the nitrogen and sulfur doped nano carbon material 2 The adsorption-desorption isotherms are shown in FIG. 3, and the BET specific surface area of the nanocarbon material is calculated to be 1447.8m by the isothermal adsorption-desorption curve 2 Per g, specific surface area in micropores 1077.2m 2 (ii)/g, the proportion of the total specific surface area is 74.4%; the total pore volume of the nanocarbon material was 1.540cm 3 Per g, micropore volume of 0.595cm 3 (iv)/g, at a ratio of 38.6% of total pore volume; the data show that the nano carbon material is mainly of a microporous structure and simultaneously contains a small amount of nano carbon material with a mesoporous structure;
the carbon content of the nitrogen and sulfur doped nano carbon material is 51.88 percent by mass, the sulfur content is 2.95 percent by mass, the nitrogen content is 8.28 percent by mass, the oxygen content is 30.68 percent by mass, and the hydrogen content is 6.21 percent by mass;
as shown in FIG. 4, the X-ray photoelectron spectroscopy (XPS) of the nitrogen and sulfur doped nanocarbon material shows that XPS peaks of C, N, O and S obviously exist, wherein characteristic peaks of sulfur exist at 163 + -1 eV and 167 + -1 eV, characteristic peaks of nitrogen exist at 398 + -1 eV and 400 + -1 eV, and characteristic peaks of oxygen exist at 530-533eV, further proving effective doping of N and S elements, and further containing oxygen elements. The atomic ratio of each element on the surface of the nano carbon material can be calculated according to the peak area, the mass percentage of carbon on the surface of the nano carbon material is 81.14%, the mass percentage of oxygen is 10.01%, the mass percentage of nitrogen is 8.51%, and the mass percentage of sulfur is 0.33%;
the XPS S2p spectrum of the nanocarbon material is shown in fig. 5, from which it can be seen that sulfur mainly exists in the forms of thiophenic sulfur and sulfur oxide.
The Raman test result of the nitrogen and sulfur doped nano carbon material is shown in FIG. 6, and the nano carbon material can be seen to have obvious D peak and G peak, I peak D /I G =0.97, indicating that the nanocarbon material has a certain graphitization degree.
Preparation example 2
(1) Preparing a precursor: according to the molar ratio of nickel salt (calculated by nickel element), nitrogen-containing organic acid and sulfur-containing potassium salt of 1:1:0.5, weighing 10g of basic nickel carbonate and 20.08g of ethylenediamine tetraacetic acid, dissolving in 200mL of deionized water, uniformly stirring to obtain a solution, then weighing 4.68g of potassium bisulfate, adding into the solution, heating and stirring at 95 ℃ for 4h, placing in an oven for drying to obtain 26g of precursor, and grinding the precursor into powder for later use;
(2) Roasting: weighing 10g of precursor in a porcelain boat, then placing the porcelain boat in a tubular roasting furnace, raising the temperature to 650 ℃ at a temperature rise rate of 5 ℃/min under the protection of nitrogen, roasting at constant temperature for 4h, and finally reducing the temperature to room temperature at a temperature drop rate of 5 ℃/min to obtain 2.8g of pyrolysis product;
(3) Dissolving 2.8g of pyrolysis product in 50mL of deionized water, stirring uniformly, adding 6mL of concentrated hydrochloric acid, heating to 105 ℃, stirring for 24h, cooling to room temperature, performing suction filtration, washing with water to be neutral, putting the obtained product in an oven, and drying overnight to obtain 400mg of nitrogen and sulfur doped nano carbon material.
The nitrogen and sulfur doped carbon nanomaterial has a mixed morphology of hollow cage shape and sheet shape, and the diameter of the hollow structure is 5-50nm as determined by a transmission electron microscope;
the BET specific surface area of the nitrogen and sulfur doped nano carbon material is calculated to be 845.86m through the detection of a BET test method and an isothermal desorption curve 2 Per g, specific surface area in micropores 707.04m 2 (iv)/g, in a proportion of 83.6% of the total specific surface area; the total pore volume of the nanocarbon material was 1.51cm 3 Per g, micropore volume of 0.59cm 3 (ii)/g, in a proportion of 39% of the total pore volume; the data show that the nano carbon material is mainly of a microporous structure and simultaneously contains a small amount of nano carbon material with a mesoporous structure;
the content of carbon in the nitrogen and sulfur doped nano carbon material is 52.02 percent by mass, the content of sulfur is 2.52 percent by mass, the content of nitrogen is 9.58 percent by mass, the content of oxygen is 29.08 percent by mass, and the content of hydrogen is 6.80 percent by mass;
the mass percentage of carbon on the surface of the nitrogen and sulfur doped carbon nanomaterial is 79.4%, the mass percentage of oxygen is 8.8%, the mass percentage of nitrogen is 10.77%, and the mass percentage of sulfur is 1.03% measured by X-ray photoelectron spectroscopy;
raman tests show that the nitrogen and sulfur doped nano carbon material has obvious D peak and G peak, I D /I G And =0.995, which indicates that the nano carbon material has a certain graphitization degree.
Preparation example 3
(1) Preparing a precursor: according to the molar ratio of nickel salt (calculated by nickel element), nitrogen-containing organic acid and sulfur-containing potassium salt of 1:0.7:1, weighing 10g of basic nickel carbonate and 14.05g of ethylenediamine tetraacetic acid, dissolving the basic nickel carbonate and the ethylenediamine tetraacetic acid in 200mL of deionized water, uniformly stirring to obtain a solution, then weighing 9.36g of potassium bisulfate, adding the solution into the solution, heating and stirring at 95 ℃ for 4 hours, then placing the solution in an oven for drying to obtain 27g of a precursor, and grinding the precursor into powder for later use;
(2) Roasting: weighing 10g of precursor in a porcelain boat, then placing the porcelain boat in a tubular roasting furnace, heating to 650 ℃ at a heating rate of 5 ℃/min under the protection of nitrogen, roasting at constant temperature for 4h, and finally cooling to room temperature at a cooling rate of 5 ℃/min to obtain 4.3g of pyrolysis product;
(3) Dissolving 4.3g of pyrolysis product in 50mL of deionized water, stirring uniformly, adding 8mL of concentrated hydrochloric acid, heating to 105 ℃, stirring for 24h, cooling to room temperature, performing suction filtration, washing with water to be neutral, putting the obtained product in an oven, and drying overnight to obtain 332mg of nitrogen and sulfur doped nanocarbon material.
The nitrogen and sulfur doped carbon nanomaterial has a mixed shape of a hollow cage and a sheet, and the diameter of the hollow cage is 5-50nm;
the BET specific surface area of the nitrogen and sulfur doped nano carbon material is 1356.5m calculated through an isothermal adsorption and desorption curve through detection of a BET test method 2 (g) specific surface area in micropores of 960.3m 2 (ii)/g, the proportion of the total specific surface area is 71%; the total pore volume of the nanocarbon material was 1.49cm 3 G, micropore volume of 0.58cm 3 (iv)/g, 38.9% of total pore volume; the data show that the nano carbon material is mainly of a microporous structure and simultaneously contains a small amount of nano carbon material with a mesoporous structure;
the content of carbon in the nitrogen and sulfur doped nano carbon material is 45.43 percent by mass, the content of sulfur is 12.05 percent by mass, the content of nitrogen is 5.79 percent by mass, the content of oxygen is 29.54 percent by mass, and the content of hydrogen is 7.19 percent by mass;
the mass percentage of carbon on the surface of the nitrogen and sulfur doped carbon nanomaterial is 79.3%, the mass percentage of oxygen is 13.42%, the mass percentage of nitrogen is 5.24%, and the mass percentage of sulfur is 2.04% measured by X-ray photoelectron spectroscopy;
raman tests show that the nitrogen and sulfur doped nano carbonThe material has obvious D peak and G peak, I D /I G And =0.99, which indicates that the nano carbon material has a certain graphitization degree.
Comparative preparation example 1
The nitrogen-doped nanocarbon material was prepared according to the method of preparation example 1, except that potassium hydrogen sulfate was not used in the precursor preparation process of step (1).
(1) Preparing materials: 10g of basic nickel carbonate and 20.08g of ethylenediamine tetraacetic acid are accurately weighed, dissolved in 100mL of deionized water and uniformly stirred. After stirring with heating at 95 ℃ for 4h, it was placed in an oven. And finally obtaining 25g of precursor, and grinding the precursor into powder for later use.
(2) Roasting: accurately weighing 10g of precursor in a porcelain boat, then placing the porcelain boat in a tubular roasting furnace, raising the temperature to 600 ℃ at the heating rate of 5 ℃/min under the protection of nitrogen, roasting at constant temperature for 4h, and finally reducing the temperature to room temperature at the rate of 5 ℃/min to obtain 3.0g of black-gray pyrolysis product.
(3) And dissolving the pyrolysis product in a proper amount of deionized water, uniformly stirring, and adding 10mL of concentrated hydrochloric acid with the mass fraction of 37%. Then the temperature is raised to 100 ℃, and the mixture is heated and stirred for 12 hours. Cooling to room temperature, filtering, washing with water to neutrality, drying in an oven overnight. 800mg of nitrogen-doped nano carbon material is obtained.
The BET specific surface area of the nitrogen-doped nano carbon material is calculated to be 328.5m through the detection of a BET test method and an isothermal adsorption-desorption curve 2 G, specific surface area in micropores 30.7m 2 The proportion of the water-soluble polymer to the total specific surface area is 10 percent; the total pore volume of the nanocarbon material was 1.45cm 3 Per g, micropore volume of 0.05 cm 3 (ii)/g, in a proportion of 3.4% of the total pore volume; the data show that the nitrogen-doped nano carbon material is mainly of a mesoporous structure;
the content of carbon in the nitrogen-doped nano carbon material is 55.43 percent by mass, the content of nitrogen is 12.5 percent by mass, the content of oxygen is 25.38 percent by mass, and the content of hydrogen is 6.69 percent by mass;
the mass percent of carbon, oxygen and nitrogen on the surface of the nitrogen-doped nano carbon material is 84.91%, 9.53% and 5.56%, respectively, measured by X-ray photoelectron spectroscopy;
raman tests show that the nitrogen-doped nano carbon material has obvious D peak and G peak, I D /I G And =0.85, which indicates that the nano carbon material has a certain graphitization degree.
Comparative preparation example 2
A nanocarbon material was produced by following the method of production example 1, except that ethylenediaminetetraacetic acid and potassium hydrogensulfate were not used in the precursor production of step (1).
(1) Preparing materials: 10g of basic nickel carbonate and 20g of citric acid were dissolved in 100mL of deionized water, heated and stirred at 95 ℃ for 4 hours, and then placed in an oven to be dried. And grinding the dried precursor into powder for later use.
(2) Roasting: 10g of the precursor is weighed and placed in a tubular roasting furnace. Under the protection of nitrogen, heating to 650 ℃ at the heating rate of 5 ℃/min, roasting at constant temperature for 2h, and finally naturally cooling to room temperature to obtain a black primary product.
(3) And then dissolving the initial product in a proper amount of deionized water, uniformly stirring, and adding 10mL of concentrated hydrochloric acid with the mass fraction of 37%. Then the temperature is raised to 95 ℃, and the mixture is heated and stirred for 12 hours. Cooling to room temperature, filtering, and washing with water to neutrality. And (4) putting the carbon material into an oven, and drying the carbon material overnight to obtain 2g of the nano carbon material without the doping elements.
The BET specific surface area of the nano carbon material is calculated to be 285.3m through the detection of a BET test method and an isothermal adsorption-desorption curve 2 G, specific surface area in micropores 10.28m 2 The proportion of the water-soluble polymer to the total specific surface area is 3.6 percent; the total pore volume of the nanocarbon material was 1.53cm 3 Per g, micropore volume of 0.02cm 3 (iv)/g, at a ratio of 1.3% of total pore volume; the data show that the nano carbon material is mainly of a mesoporous structure;
the carbon content of the nano carbon material is 60.25 percent by mass, the oxygen content of the nano carbon material is 25.06 percent by mass, and the hydrogen content of the nano carbon material is 5.68 percent by mass;
the carbon content of the surface of the nano carbon material is 85.61 percent by mass, the oxygen content of the surface of the nano carbon material is 8.72 percent by mass, and the nickel content of the surface of the nano carbon material is 5.67 percent by mass;
raman test shows that the nano carbon material has obvious D peak and G peak, I D /I G =0.79, which indicates that the nanocarbon material has a certain graphitization degree.
The cyclic voltammetry tests are carried out on the nitrogen and sulfur doped nanocarbon materials prepared in preparation examples 1-3, cyclic voltammetry curves of the nitrogen and sulfur doped nanocarbon materials prepared in preparation example 1 at different scanning rates are provided exemplarily, as shown in fig. 7, the curves can be seen to be elliptical and have redox peaks, which shows that pseudocapacitance is introduced by doping of nitrogen atoms and sulfur atoms, and thus the overall performance of the material is improved.
Examples A1 to A3 serve to illustrate capacitor electrode materials, capacitor electrodes and methods for their preparation.
Example A1
Preparing a capacitor electrode: 32mg of the nitrogen-and sulfur-doped nanocarbon material prepared in preparation example 1 was weighed, and the nanocarbon material, a conductive agent (acetylene black) and a binder (polytetrafluoroethylene) were mixed in the following ratio of 8:1:1. mixing the raw materials according to the mass ratio, dripping a proper amount of absolute ethyl alcohol, fully grinding, rolling the slurry into a sheet shape, and then placing the sheet shape in a vacuum oven at 80 ℃ for drying overnight; after drying, the sheet was cut into pieces having a diameter of 10 mm. And pressing the pole piece to a stainless steel mesh current collector by using a hydraulic press, wherein the content of active substances on the pole piece is 0.8-3mg.
Example A2
Preparing a capacitor electrode: a capacitor electrode was fabricated by the method of example A1, except that the same weight of the nitrogen-and sulfur-doped nanocarbon material as that fabricated in preparation example 2 was weighed as an electrode active material.
Example A3
Preparing a capacitor electrode: a capacitor electrode was fabricated by the method of example A1, except that the same weight of the nitrogen-and sulfur-doped nanocarbon material as that fabricated in preparation example 3 was weighed as an electrode active material.
Comparative example A1
Preparing a capacitor electrode: a capacitor electrode was fabricated by the method of example A1, except that the same weight of the nitrogen-doped nanocarbon material as that fabricated in comparative preparation example 1 was weighed as an electrode active material.
Comparative example A2
Preparing a capacitor electrode: a capacitor electrode was fabricated by the method of example A1, except that the same weight of the undoped nanocarbon material produced in comparative preparation example 2 was weighed as an electrode active material.
Test example a was used to test the capacitive properties of the capacitor electrodes.
Test example A
And (3) adopting a three-electrode system to carry out capacitance performance test: the three-electrode system uses the electrodes prepared in examples A1-A3 and comparative examples A1-A2 as working electrodes, platinum electrode as counter electrode, mercury oxide electrode as reference electrode, and 6mol/L KOH aqueous solution as electrolyte.
And respectively carrying out constant-current charge and discharge tests on the assembled three-electrode system, wherein the tested voltage range (relative to the mercury oxide electrode) is 0V to-1V, and recording the specific capacitance under different current densities (0.5-20A/g).
The capacitor electrode obtained in example A1 had a specific capacitance of 358F/g at a current density of 0.5A/g, 280F/g at a current density of 1A/g, 210F/g at a current density of 5A/g, 176F/g at a current density of 10A/g and 148F/g at a current density of 20A/g.
The specific capacitance of the capacitor electrode obtained in example A2 at a current density of 1A/g was 270F/g.
The specific capacitance of the capacitor electrode obtained in example A3 at a current density of 1A/g was 190F/g.
The specific capacitance of the capacitor electrode obtained in comparative example A1 at a current density of 1A/g was 150F/g.
The capacitor electrode obtained in comparative example A2 had a specific capacitance of 120F/g at a current density of 1A/g.
Examples B1 to B3 serve to illustrate capacitor electrode materials, capacitor electrodes and methods for their preparation.
Example B1
Preparing a capacitor electrode: 80mg of the nitrogen-and sulfur-doped nanocarbon material prepared in preparation example 1 was weighed, and the nanocarbon material, a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) were mixed in a ratio of 8:1:1. mixing the components according to the mass ratio, dropping a proper amount of solvent (N-methylpyrrolidone) into the mixture, fully grinding the mixture, then blade-coating the slurry on a clean copper foil, and then placing the copper foil in a vacuum oven at 80 ℃ for drying overnight; after drying, cutting the electrode into round electrode pieces with the diameter of 10mm and the mass of 2.5mg, wherein the content of active substances on the electrode pieces is 0.8-2mg.
Example B2
Preparing a capacitor electrode: 32mg of the nitrogen-and sulfur-doped nanocarbon material prepared in preparation example 1 was weighed, and the nanocarbon material, a conductive agent (acetylene black) and a binder (polytetrafluoroethylene) were mixed in a ratio of 8:1:1. mixing the components according to the mass ratio, and dropping a proper amount of solvent (absolute ethyl alcohol) for full grinding until the slurry is in a plasticine state; spreading and rolling the slurry in the plasticine state into uniform slices by using a glass rod, and then drying the slices in an oven at 80 ℃ for 2 to 3 hours; after completely drying, cutting the electrode into a circular pole piece with the diameter of 10mm and the mass of 2.1mg, and pressing the circular pole piece onto a stainless steel mesh current collector by using a hydraulic machine under the pressure of 10MPa to obtain the capacitor electrode.
Example B3
Preparing a capacitor electrode: a capacitor electrode was prepared according to the method of example B2, except that nitrogen, sulfur-doped nanocarbon material, conductive agent (acetylene black) and binder (polytetrafluoroethylene) were mixed in the following ratio of 7:2:1, in a mass ratio of 1.
Comparative example B1
Preparing a capacitor electrode: a capacitor electrode was fabricated by the method of example B2, except that the same weight of the nitrogen-doped nanocarbon material as that fabricated in comparative preparation example 1 was weighed as an electrode active material.
Comparative example B2
Preparing a capacitor electrode: a capacitor electrode was fabricated by the method of example B2, except that the same weight of the nanocarbon material as that fabricated in comparative preparation example 2 was weighed as an electrode active material.
Comparative example B3
Preparing a capacitor electrode: capacitor electrodes were prepared as in example B2, except that the same weight of commercially available graphite (commercially available from beidou corporation) was weighed out as the electrode active material.
Test example B is illustrative of a lithium ion capacitor and a method of making the same.
Test example B
Assembling the capacitor: the capacitor electrodes and the polypropylene separators prepared in examples B1 to B3 and comparative examples B1 to B3 were respectively immersed in lithium hexafluorophosphate electrolyte for 0.5h and then taken out, and lithium hexafluorophosphate was used as electrolyte, and the button-type lithium ion capacitor was assembled in the order of battery case (positive electrode) -lithium sheet-separator-electrode-battery case (negative electrode).
And (4) performance testing: and characterizing the specific capacity, the rate capability and the cycling stability of the prepared button lithium ion capacitor through a blue electricity system. In the voltage range of 0-3V, the materials are discharged and recharged at different current densities (0.1-2A/g).
The present invention exemplarily provides a constant current charge and discharge curve of the nitrogen and sulfur doped nanocarbon material prepared in preparation example 1, as shown in fig. 8, it can be found from the constant current charge and discharge curve of fig. 8 that the curve presents an asymmetric shape, and the rest of preparation examples are similar, which indicates that the nitrogen and sulfur doped nanocarbon material provided by the present invention has an electric double layer capacitance and a pseudocapacitance, and can be applied to a lithium ion capacitor or an electric double layer supercapacitor.
The capacitor electrode prepared in example B1 had a first discharge specific capacity of 1540mAh/g and a charge specific capacity of 900mAh/g at a current density of 0.1A/g. Their corresponding specific capacities at different current densities are shown in fig. 9. Under the current density of 0.1A/g, the stable specific capacity exceeds 800mAh/g. The specific capacity is 395mAh/g under the current density of 1A/g. When the current density is increased to 2A/g, the specific capacity can still reach 290mAh/g. In addition, as shown in fig. 12, the capacity retention rate of the first capacitor obtained in example B1 reached 80% after 1000 cycles at a current density of 1A/g.
The capacitor electrode prepared in example B2 has a first discharge specific capacity of 1557.3mAh/g and a charge specific capacity of 950.7mAh/g at a current density of 0.1A/g. Their corresponding specific capacities at different current densities are shown in fig. 10. Under the current density of 0.1A/g, the stable specific capacity exceeds 900mAh/g. Under the current density of 1A/g, the specific capacity is 420mAh/g. When the current density is increased to 2A/g, the specific capacity can still reach 300mAh/g. In addition, the capacity retention of the capacitor electrode obtained in example B2 was close to 60% after 1000 cycles at a current density of 1A/g.
The capacitor electrode prepared in example B3 has a first discharge specific capacity of 1485.2mAh/g and a charge specific capacity of 850.1mAh/g at a current density of 0.1A/g. Their corresponding specific capacities at different current densities are shown in fig. 11. Under the current density of 0.1A/g, the stable specific capacity exceeds 800mAh/g. The specific capacity is 300mAh/g under the current density of 1A/g. When the current density is increased to 2A/g, the specific capacity can still reach 190mAh/g. After 1000 cycles at a current density of 1A/g, the capacity retention rate was 71%.
The capacitor electrode prepared in comparative example B1 has a stabilized specific capacity of 600mAh/g at a current density of 0.1A/g. The specific capacity is 260mAh/g under the current density of 1A/g. When the current density is increased to 2A/g, the specific capacity is only 180mAh/g. After 1000 cycles at a current density of 1A/g, the capacity retention was 50%.
The capacitor electrode prepared in comparative example B2 has a stabilized specific capacity of 500mAh/g at a current density of 0.1A/g. Under the current density of 1A/g, the specific capacity is 180mAh/g. When the current density is increased to 2A/g, the specific capacity is only 130mAh/g. After 1000 cycles at a current density of 1A/g, the capacity retention rate was close to 60%.
The capacitor electrode prepared in the comparative example B3 has the highest specific capacity of only 360mAh/g after being stabilized under the current density of 0.1A/g. In addition, the capacity retention rate after 1000 cycles at a current density of 1A/g is less than 50%.
From the data analysis, the nitrogen and sulfur doped nano carbon material shows excellent specific capacity, rate capability and cycle performance when applied to a lithium ion capacitor; when the single-electrode specific capacitance material is applied to an electric double layer super capacitor, the single-electrode specific capacitance can reach 358F/g at the current density of 0.5A/g in an aqueous electrolyte, and the single-electrode specific capacitance material shows excellent capacitance performance.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (17)
1. The nitrogen and sulfur doped nano carbon material is characterized in that the nano carbon material has a micropore structure and a mesoporous structure, and the BET specific surface area of the nano carbon material is 800-2000m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 50-85%; the total pore volume of the nano carbon material is more than 1cm 3 The proportion of the micropore volume to the total pore volume is 30-50%; the mass percentage of carbon on the surface of the nano carbon material is 70-95% by X-ray photoelectron spectroscopy; the mass percentage of nitrogen is 3-20%; the mass percentage of the sulfur is 0.1-10%; the carbon content in the nano carbon material measured by an element analyzer is 30-60% by mass; the mass percentage of nitrogen is 1-15%; the mass percentage of the sulfur is 1-15%.
2. The nanocarbon material according to claim 1, wherein the BET specific surface area of the nanocarbon material is 800 to 1600m 2 The proportion of the specific surface area in the micropores to the total specific surface area is 70-85%; the total pore volume of the nano carbon material is more than 1.45cm 3 (ii)/g, the proportion of micropore volume to total pore volume is 35-50%; the mass percentage of carbon on the surface of the nano carbon material is 79-95% measured by X-ray photoelectron spectroscopy; the mass percentage of nitrogen is 5-11%; the mass percentage of the sulfur is 0.2-5%; the mass percentage of carbon in the nano carbon material is 35-55% measured by an element analyzer; the mass percentage of nitrogen is 5-15%; the mass percentage of the sulfur is 2-15%.
3. The nanocarbon material according to claim 1 or 2, wherein the nanocarbon material has a mixed morphology of hollow cage and sheet, and a diameter of a hollow structure of the nanocarbon material is 5 to 50nm.
4. The nanocarbon material according to claim 1 or 2, wherein the ratio of the intensities of the D peak and the G peak in the raman curve of the nanocarbon material is 0.5 to 1.5, preferably 0.5 to 1.
5. A preparation method of a nitrogen and sulfur doped nano carbon material is characterized by comprising the following steps:
(1) Preparing a precursor: forming a homogeneous phase solution by using a nickel salt, a nitrogen-containing organic acid, a sulfur-containing potassium salt and a solvent, and then removing the solvent in the homogeneous phase solution to obtain a precursor, wherein the nitrogen-containing organic acid is ethylenediamine tetraacetic acid and/or 2, 5-dipicolinic acid, and the sulfur-containing potassium salt is potassium sulfate and/or potassium bisulfate;
(2) Roasting: roasting the precursor obtained in the step (1) under the protection of inert atmosphere to obtain a pyrolysis product;
(3) Acid washing: providing an aqueous solution containing the pyrolysis product obtained in the step (2), carrying out contact reaction with acid, and then carrying out solid-liquid separation, washing and drying.
6. The production method according to claim 5, wherein in the step (1), the nickel salt is selected from one or more of basic nickel carbonate, nickel acetate, nickel chloride, nickel nitrate and nickel sulfate, preferably basic nickel carbonate; the nitrogenous organic acid is ethylenediamine tetraacetic acid; the sulfur-containing potassium salt is potassium bisulfate.
7. The production method according to claim 5, wherein in the step (1), the mass ratio of the nickel salt, the nitrogen-containing organic acid and the sulfur-containing potassium salt is 1:0.5-1:0.5-2.
8. The production method according to claim 5, wherein, in the step (2), the roasting method comprises: heating to 400-1000 deg.C at a heating rate of 2-10 deg.C/min, preferably 5-10 deg.C/min, heating to 600-800 deg.C, baking at constant temperature for 1-8 hr, preferably 2-4 hr, and cooling to room temperature at a cooling rate of 1-10 deg.C/min, preferably 3-5 deg.C/min; the inert atmosphere is nitrogen atmosphere and/or argon atmosphere.
9. The production method according to claim 5, wherein in the step (3), the acid used for acid washing is selected from one or more of concentrated hydrochloric acid, concentrated sulfuric acid and acetic acid, preferably concentrated hydrochloric acid.
10. The production method according to claim 5 or 9, wherein, in the step (3), the temperature of the acid washing is 80 to 120 ℃, preferably 90 to 100 ℃; the contact reaction time is 6-24h, preferably 8-12h.
11. An electrode material for capacitors, comprising an active material, a conductive agent and a binder, wherein the active material is the nitrogen-and sulfur-doped nanocarbon material according to any one of claims 1 to 4 or the nitrogen-and sulfur-doped nanocarbon material produced by the production method according to any one of claims 5 to 10.
12. The electrode material according to claim 11, wherein the mass ratio of the nitrogen-sulfur doped nanocarbon material, the conductive agent and the binder is 7-18:1-3:1.
13. 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 electrode material according to claim 11 or 12.
14. A method for producing a capacitor electrode, which comprises coating and/or filling a slurry containing an active material, a conductive agent, a binder and a solvent on a current collector, drying, rolling or not, characterized in that the active material is the nitrogen-and sulfur-doped nanocarbon material according to any one of claims 1 to 4 or the nitrogen-and sulfur-doped nanocarbon material produced by the production method according to any one of claims 5 to 10.
15. The method for producing a capacitor electrode according to claim 14, wherein the solvent is ethanol and/or N-methylpyrrolidone, preferably N-methylpyrrolidone.
16. A capacitor comprising a battery case, electrodes, a separator, and an electrolyte, wherein the electrodes comprise the capacitor electrode of claim 13 or the capacitor electrode prepared by the method of claim 14 or 15.
17. The capacitor of claim 16, wherein the capacitor is a lithium ion capacitor or an electric double layer supercapacitor.
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| WO2023160605A1 (en) * | 2022-02-23 | 2023-08-31 | 中国石油化工股份有限公司 | Sulfur-modified carbon material, preparation method therefor, and application thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2023160605A1 (en) * | 2022-02-23 | 2023-08-31 | 中国石油化工股份有限公司 | Sulfur-modified carbon material, preparation method therefor, and application thereof |
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