CN113903598A

CN113903598A - Activated carbon material, preparation method thereof and supercapacitor

Info

Publication number: CN113903598A
Application number: CN202111121070.9A
Authority: CN
Inventors: 程钢; 汪福明; 任景润; 李子坤; 任建国; 黄友元; 贺雪琴
Original assignee: Shenzhen Beiteri New Energy Technology Research Institute Co ltd
Current assignee: Shenzhen Beiteri New Energy Technology Research Institute Co ltd
Priority date: 2021-09-24
Filing date: 2021-09-24
Publication date: 2022-01-07
Anticipated expiration: 2041-09-24
Also published as: CN113903598B

Abstract

The application relates to an activated carbon material, a preparation method thereof and a supercapacitor, wherein a pore structure is formed inside the activated carbon material, the surface of the pore wall of the pore structure contains doping elements, and the total volume of the pore structure is 0.40cm³/g～0.80cm³(g) pore structure volume with pore diameter within 1nm is more than or equal to 0.25cm³The active carbon material prepared by the method contains a pore structure, the surface of the pore wall of the pore structure contains doping elements, the pore structure has certain energy storage activity, and the outer surface of the active carbon material does not have energy storage activity basically, so that the doping elements are only effectively doped in the pore structure, the adsorption of capacitance carbon on electrolyte ions is promoted, and the active carbon material is improvedMaterial capacity and self-discharge performance.

Description

Activated carbon material, preparation method thereof and supercapacitor

Technical Field

The application relates to the technical field of electrode materials of supercapacitors, in particular to an activated carbon material, a preparation method thereof and a supercapacitor.

Background

The birth of the super capacitor renovates the life style of people and has epoch-making significance. In recent years, the market demand for supercapacitors has seen well-spray development. The sulfuric acid capacitor is widely applied to the fields of energy storage, start-stop power supply, electronic instruments and the like due to the advantages of good power performance, wide working temperature range and the like. The activated carbon material has the advantages of good conductivity, low cost, easy adjustment of specific surface area and the like, and is a main electrode material of the super capacitor. The sulfuric acid capacitor is a capacitor which takes sulfuric acid solution as electrolyte and takes active carbon as electrode active substance, and has higher requirements on the capacity and self-discharge performance of electrode active carbon materials.

At present, the development of an activated carbon material (hereinafter referred to as capacitance carbon) for a capacitor electrode has the following technical difficulties:

the carbon doping modification of the capacitor is difficult to realize the directional doping of the area and the effective doping is difficult to achieve. The capacitor carbon stores energy through surface adsorption of electrolyte ions, the surface of the capacitor carbon is the main place for energy storage, and the surface of the capacitor carbon is divided into an inner surface (surface of a porous area) and an outer surface (surface of a non-porous area). In a full-electric state, desolvated electrolyte ions are adsorbed on the inner surface, are less influenced by a solvent and are difficult to desorb under an open circuit; solvated electrolyte ions are adsorbed on the outer surface, have a thick solvated layer, are easily interfered by a solvent, and are easily desorbed under an open circuit. The heteroatom doping can promote the adsorption of the capacitor carbon to electrolyte ions, and the ideal doping mode of the capacitor carbon is that the heteroatom is doped on the inner surface, and the doping can simultaneously improve the capacity and the self-discharge performance. The prior art can not realize directional doping on the inner surface of the material, and is difficult to directionally adjust the aperture size of the inner hole of the material.

Therefore, the research and development of the active carbon material with accurate and adjustable pore size, selective doping and high capacity is a technical problem in the development field of electrode materials of the super capacitor.

Disclosure of Invention

In order to overcome the defects, the application provides the activated carbon material, the preparation method thereof and the supercapacitor, so that the activated carbon material doped on the inner surface of the material can be obtained by accurately regulating and controlling the pore size and selectively, and the capacity performance and the self-discharge performance of the activated carbon material can be effectively improved.

In a first aspect, an embodiment of the present application provides an activated carbon material, where a pore structure is formed inside the activated carbon material, a surface of a pore wall of the pore structure contains a doping element, and a total volume of the pore structure is 0.40cm³/g～0.80cm³(g) pore structure volume with pore diameter within 1nm is more than or equal to 0.25cm³/g。

In combination with the first aspect, the activated carbon material includes at least one of the following features a to d:

a. the pore structure comprises micropores, and the volume ratio of the micropores in the pore structure is 85-95%;

b. the ratio of the total mass content of doping elements in the cross-section area of the activated carbon material to the total mass content of doping elements in the surface area of the activated carbon material is more than or equal to 1.25;

c. the doping element comprises at least one of nitrogen, phosphorus and sulfur;

d. the mass content of the doping element in the activated carbon material is 0.01-8%.

In combination with the first aspect, the activated carbon material includes at least one of the following features a to j:

a. the tap density of the activated carbon material is 0.55g/cm³～0.75g/cm³；

b. The pH value of the activated carbon material is 1-4;

c. the median particle size of the activated carbon material is 0.5-40 μm;

d. the acid radical content in the activated carbon material is 500-80000 ppm;

e. the liquid absorption value of the activated carbon material is 1.30 g/g-2.00 g/g;

f. the moisture content in the activated carbon material is less than or equal to 5 percent;

g. the specific mass capacity of the activated carbon material is 58F/g-80F/g;

h. the comprehensive specific capacity of the activated carbon material is 20-28F/g;

i. the self-discharge retention rate of the activated carbon material is more than or equal to 75 percent;

j. the specific surface area of the activated carbon material is 900m²/g～1300m²/g。

In a second aspect, an embodiment of the present application provides a method for preparing an activated carbon material, where the method includes:

carrying out first dipping treatment and first drying treatment on a porous carbon material in an oxidizing solution to obtain a first precursor, wherein the temperature of the first dipping treatment is 1-45 ℃;

and mixing the first precursor and the doping agent, and then carrying out heat treatment to obtain the activated carbon material.

In combination with the second aspect, the method further comprises:

carbonizing a carbon source to obtain a carbonized material, mixing the carbonized material with an activating agent, and then performing activation treatment to obtain the porous carbon material.

In combination with the second aspect, the method comprises at least one of the following features a to o:

a. the carbon source comprises at least one of phenolic resin, epoxy resin, melamine resin, furfural resin, urea resin, asphalt, coke, anthracite, mesocarbon microbeads, starch, cane sugar, coconut shells, almond shells, jujube shells and walnut shells;

b. the charring atmosphere comprises a first protective atmosphere;

c. the carbonized atmosphere comprises a first protective atmosphere, and the first protective atmosphere comprises at least one of nitrogen, argon, neon, helium, xenon and krypton;

d. the carbonization atmosphere comprises a first protective atmosphere, and the oxygen content of the first protective atmosphere is 0.5-1 wt%;

e. the carbonization temperature is 250-700 ℃;

f. the carbonization time is 0.5-24 h;

g. in the process of carbonizing a carbon source to obtain a carbonized material, a curing agent is also added into the carbon source;

h. in the process of carbonizing a carbon source to obtain a carbonized material, a curing agent is also added into the carbon source, wherein the curing agent comprises at least one of melamine, hexamethylenetetramine, formaldehyde, p-benzaldehyde, ammonium chloride and ammonium acetate;

i. in the process of carbonizing a carbon source to obtain a carbonized material, adding a curing agent into the carbon source, wherein the mass ratio of the curing agent to the carbon source is (5:95) - (95: 5);

j. in the process of carbonizing a carbon source to obtain a carbonized material, adding a curing agent into the carbon source, wherein the mixing time of the carbon source and the curing agent is 5-120 min;

k. the activating agent comprises at least one of sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, sodium carbonate, potassium bicarbonate, sodium bicarbonate, calcium oxide and zinc chloride;

the mass ratio of the activating agent to the carbonized material is (0.5-3): 1;

m, the temperature of the activation treatment is 400-800 ℃;

n, the time t of the activation treatment is more than 0 and less than or equal to 4 h;

the porous carbon material has a median particle diameter of 2 to 40 μm.

In combination with the second aspect, the method includes at least one of the following features a to g:

a. the mass ratio of the porous carbon material to the oxidizing solution is 1: (2-20);

b. the time of the first dipping treatment is 0.1-48 h;

c. the oxidizing solution is obtained by dispersing an oxidizing agent in deionized water;

d. the oxidizing solution is obtained by dispersing an oxidizing agent in deionized water, the oxidizing agent including at least one of sulfuric acid, ammonium sulfate, hypochlorous acid, chloric acid, perchloric acid, hypobromous acid, bromic acid, pyrosulfuric acid, and ammonium persulfate;

e. the mass concentration of the oxidizing solution is 1-90 wt%;

f. the temperature of the first drying treatment is 80-150 ℃;

g. the time of the first drying treatment is 24-72 h.

a. the dopant comprises at least one of a phosphorous source, a nitrogen source, and a sulfur source;

b. the mass ratio of the first precursor to the dopant is (70-99): (1-30);

c. the heat treatment is carried out in a second protective gas atmosphere;

d. the heat treatment is carried out in a second protective atmosphere comprising at least one of nitrogen, argon, neon, helium, xenon, and krypton;

e. the heat treatment is carried out in a second protective atmosphere, and the oxygen content of the second protective atmosphere is 0.5-1 wt%;

f. the temperature of the heat treatment is 200-900 ℃;

g. the time of the heat treatment is 0.5 h-10 h.

With reference to the second aspect, the heat treatment further includes a step of subjecting the heat-treated material to a second dipping treatment and a second drying treatment in an acid solution.

In combination with the second aspect, the method includes at least one of the following features a to e:

a. the mass ratio of the material obtained by the heat treatment to the acid solution is 1: (3-30);

b. the acid solution comprises at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, oxalic acid and phosphoric acid;

c. the mass concentration of the acid solution is 1 wt% -98 wt%;

d. the time of the second dipping treatment is 0.1-48 h;

e. and the water content in the obtained material after the second drying treatment is less than or equal to 5 percent.

In a third aspect, a supercapacitor comprises the activated carbon material of the first aspect or the activated carbon material prepared by the preparation method of the second aspect.

The technical scheme of the application has at least the following beneficial effects:

(1) the active carbon material prepared by the application has a pore structure inside, and the surface of the pore wall of the pore structure contains doping elements, so that compared with the existing active carbon material, the pore structure formed by the active carbon material increases the volume of pores with the pore diameter within 1nm, further increases the total volume of the pore structure of the active carbon material, has certain energy storage activity, can improve the capacity performance of the capacitance carbon material, reduces the diffusion steric hindrance of electrolyte, and improves the rate performance; the doping element in the material pore structure can promote the adsorption of the capacitance carbon on electrolyte ions, thereby improving the capacity and the self-discharge performance of the active carbon material.

(2) According to the method, the porous carbon material is subjected to first dipping treatment at the temperature of 1-45 ℃, the oxidant in the oxidizing solution is filled into the pores, no hole expansion occurs in the filling process, and then the porous carbon material is mixed with the dopant and then subjected to heat treatment, so that the purpose of hole expansion can be achieved in the heat treatment process, and the porous carbon material can be doped on the surface of the pore wall of the pore structure of the activated carbon (namely the inner surface of the activated carbon material), namely, selective doping is achieved, and the capacity performance, the rate capability and the self-discharge performance of the capacitance carbon are improved simultaneously. The preparation method can simultaneously carry out doping and reaming, can realize accurate regulation of the aperture size and selective doping, has simple process, and can greatly improve the capacity performance and the rate performance of the capacitance carbon.

Drawings

The present application is further described below with reference to the drawings and examples.

FIG. 1 is a schematic flow chart illustrating the preparation of an activated carbon material according to the present application;

FIG. 2 is a schematic view of a process for preparing an activated carbon material according to the present application;

FIG. 3 is an SEM image of an activated carbon material prepared in example 1 of the present application;

FIG. 4 is an XRD pattern of an activated carbon material prepared in example 1 of the present application;

FIG. 5 is a graph comparing the structure-activity relationship between the preparation processes of example 1 and comparative example 3.

Detailed Description

For better understanding of the technical solutions of the present application, the following detailed descriptions of the embodiments of the present application are provided with reference to the accompanying drawings.

It should be understood that the embodiments described are only a few embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

The active carbon material is a main electrode material of a super capacitor because of the advantages of good conductivity, low cost, easy adjustment of specific surface area and the like, effective doping and area-oriented doping (doping inside the material) are difficult to realize by doping modification of the existing sulfuric acid capacitor capacitance carbon material, and the micropore diameter distribution of capacitance carbon is difficult to accurately adjust, so that the capacitance performance of the capacitor is poor.

The embodiment of the application provides an activated carbon materialA pore structure is formed in the carbon material, the surface of the pore wall of the pore structure contains doping elements, and the total pore volume of the pore structure is 0.40cm³/g～0.80cm³(g) pore volume of pore structure with pore diameter within 1nm of 0.25cm or more³/g。

In the technical scheme, compared with the existing activated carbon material, the pore structure formed by the activated carbon material increases the volume of pores with the pore diameter within 1nm, and further increases the total volume of the pore structure of the activated carbon material; the doping element in the material pore structure can promote the adsorption of the capacitance carbon on electrolyte ions, thereby improving the capacity and the self-discharge performance of the active carbon material.

In particular, the total volume of the pore structure may be in particular 0.40cm³/g、0.45cm³/g、0.50cm³/g、0.55cm³/g、0.60cm³/g、0.65cm³/g、0.70cm³/g、0.75cm³/g、0.80cm³And/g, etc., may be any other value within the above range, and is not limited herein. The total volume of the pore structure is less than 0.40cm³The energy storage active sites are insufficient; the total volume of the pore structure is greater than 0.80cm³The pore structure is easily collapsed in g. Pore volume of pore structure with pore diameter within 1nm may be 0.25cm³/g、0.27cm³/g、0.29cm³/g、0.32cm³/g、0.35cm³G, etc., preferably, the volume of the pore structure having a pore diameter of 1nm or more is 0.29cm or more³And/g, as can be understood, the pore structure in the activated carbon material is used for electrolyte ion energy storage, and the total volume and the pore size of the pore structure are limited within the range of 1nm, so that the energy density of the activated carbon is favorably improved.

In some embodiments, the pore structure includes micropores, which refers to pores with a pore diameter of less than 2nm, and a volume ratio of the micropores in the pore structure is 85% to 95%, specifically, the volume ratio of the micropores in the total volume of the pore structure may be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, and 95%, and the like, and may also be other values within the above range, which is not limited herein, and it is understood that controlling the volume ratio of the micropores in the pore structure within the above range is beneficial to improve the capacity performance of the activated carbon material.

In some embodiments, the ratio of the total mass content of doping elements in the cross-sectional area of the activated carbon material to the total mass content of doping elements in the surface area of the activated carbon material is greater than or equal to 1.25. Specifically, the ratio of the total mass content of the doping elements in the cross-sectional area of the activated carbon material to the total mass content of the doping elements in the surface area of the activated carbon material may be 1.25, 1.35, 1.45, 1.62, 1.85, etc., or may be other values within the above range, which is not limited herein. It can be understood that the cross-sectional area is a cross-sectional surface of a cross-sectional sample which can be obtained by cutting an activated carbon material by using a high-energy argon ion beam, the total mass content of doping elements in the cross-sectional area mainly reflects the content of doping elements on the inner surface of the activated carbon material, the surface area is an outer surface area of the activated carbon material, and the total mass content of the doping elements in the surface area mainly reflects the content of the doping elements on the outer surface of the activated carbon, so that the doping elements are mainly distributed in a hole area in the activated carbon material, and the doping elements are distributed on the hole wall surface of a hole structure in the activated carbon material (namely the inner surface of the activated carbon material), so that the electrolyte ion adsorption on the inner surface of the hole structure of the activated carbon can be promoted, and the capacity performance and the self-discharge performance of the capacitor carbon can be simultaneously improved. In addition, the doping elements are distributed on the surface of the pore structure in the activated carbon material, so that the wettability and the conductivity of the electrolyte on the inner surface of the activated carbon material can be improved, the electrolyte can be favorably immersed into a pore with long diffusion distance and large diffusion steric hindrance, the concentration polarization is reduced, and the capacity performance is further improved.

In some embodiments, the doping element comprises at least one of nitrogen, phosphorus, and sulfur. Preferably, the doping element is a nitrogen source, and the nitrogen source has an electron-rich nitrogen group, so that the electrochemical performance of the activated carbon material is improved.

In some embodiments, the mass content of the doping element in the activated carbon material is 0.01% to 8%, and the mass content of the doping element in the activated carbon material may specifically be 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, and the like, and may also be other values within the above range, which is not limited herein, and it is understood that the mass content of the doping element in the activated carbon material is controlled within the above range, which is beneficial to improve the capacity performance of the activated carbon material.

In some embodiments, the activated carbon material has a tap density of 0.55g/cm³～0.75g/cm³Specifically, the tap density of the activated carbon material is 0.55g/cm³、0.60g/cm³、0.65g/cm³、0.70g/cm³And 0.75g/cm³And the like, may be other values within the above range, and is not limited herein.

In some embodiments, the pH of the activated carbon material is 1 to 4, and the pH of the activated carbon material may be 1, 1.5, 2, 2.5, 3, 3.5, 4, etc., or other values within the above range, which is not limited herein, and preferably, the pH of the activated carbon material is 1.5 to 3.0.

In some embodiments, the median particle size of the activated carbon material is 0.5 μm to 40 μm, specifically, the median particle size of the activated carbon material may be 0.5 μm, 2 μm, 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, etc., or may be other values within the above range, which is not limited herein, and the median particle size of the activated carbon material is controlled within the above range, which is beneficial for improving the capacity performance of the activated carbon material. Preferably, the activated carbon material has a median particle size of 3 μm to 30 μm.

In some embodiments, the acid group content in the activated carbon material is 500ppm to 80000ppm, and the acid group content in the activated carbon material may be 500ppm, 1000ppm, 2000ppm, 3000ppm, 10000ppm, 20000ppm, 30000ppm, 40000ppm, 50000ppm, 60000ppm, 70000ppm, 80000ppm, or the like, or may be other values within the above range, and is not limited herein.

In some embodiments, the activated carbon material has an activated carbon uptake value of 1.30g/g to 2.00g/g, the activated carbon material can have an activated carbon uptake value of 1.30g/g, 1.40g/g, 1.50g/g, 1.60g/g, 1.70g/g, 1.80g/g, 1.90g/g, 2.00g/g, etc., and can have other values within the above range, without limitation, and it is understood that controlling the activated carbon uptake value of the activated carbon material within the above range is advantageous for improving the capacity performance of the capacitor carbon.

In some embodiments, the moisture content of the activated carbon material is less than or equal to 5%, specifically, the moisture content of the activated carbon material may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, and the like, and may also be other values within the above range, which is not limited herein, and the moisture content of the activated carbon material is controlled within the above range, which is beneficial to improve the adsorption capacity of the activated carbon material.

In some embodiments, the specific mass capacity of the activated carbon material is 58F/g to 80F/g, and the specific mass capacity of the activated carbon material may be 58F/g, 60F/g, 63F/g, 65F/g, 68F/g, 72F/g, 75F/g, 80F/g, etc., or may be other values within the above range, which is not limited herein.

In some embodiments, the integrated specific capacity of the activated carbon material is 20F/g to 28F/g, and the specific integrated specific capacity of the activated carbon material may be 20F/g, 21F/g, 22F/g, 23F/g, 24F/g, 25F/g, 26F/g, 27F/g, 28F/g, etc., or may be other values within the above range, which is not limited herein.

In some embodiments, the self-discharge retention rate of the activated carbon material is 75% or more, and the self-retention rate of the self-discharge retention rate of the activated carbon material may be 75%, 76%, 77%, 78%, 80%, 85%, 90%, or the like, or may be other values within the above range, which is not limited herein.

In some embodiments, the activated carbon material has a specific surface area of 900m²/g～1300m²The specific surface area of the activated carbon material may be 900m²/g、1000m²/g、1100m²/g、1200m²/g、1300m²And/g, etc., may be other values within the above range, and is not limited thereto, and the specific surface area of the activated carbon material is controlled within the above range to improve the adsorption capacity of the activated carbon material, and preferably 1000m²/g～1200m²/g。

The embodiment of the application provides a preparation method of an activated carbon material, which comprises the following steps:

carrying out first dipping treatment and first drying treatment on the porous carbon material in an oxidizing solution to obtain a first precursor, wherein the temperature of the first dipping treatment is 1-45 ℃;

In the technical scheme, the porous carbon material is subjected to first impregnation treatment at the temperature of 1-45 ℃, in the first impregnation process, an oxidant in an oxidizing solution is firstly filled into pores of the porous carbon material to obtain a first precursor, oxidation reaction and pore expansion are not required to be generated in the filling process, then the first precursor is mixed with a dopant and then subjected to heat treatment, in the heat treatment process, oxidation reaction and doping reaction are generated on the inner surface of the material (the inner surface of the material refers to the surface of the pore wall of a pore structure of the material), the oxidation reaction achieves the purpose of increasing the volume of the pore structure, namely pore expansion, so that the pore structure is converted from the pore structure without energy storage activity into the pore structure with energy storage activity, the doping reaction can be realized by the pore structure with energy storage activity, and the outer surface (the outer surface refers to the surface of a non-pore region of the material) does not have energy storage activity, namely, the doping reaction is only performed on the inner surface of the material, as shown in fig. 2, the pore diameter D1 of the pore structure in the first precursor is significantly smaller than the pore diameter D2 of the pore structure of the material obtained by heat treatment, and the inner surface of the material obtained by heat treatment already contains doping elements (M in fig. 2 represents a doping element), which indicates that the material obtained by heat treatment has been subjected to hole expansion and doping, and the preparation method of the material obtained by heat treatment does not perform hole expansion in advance, and performs doping and hole expansion simultaneously in the heat treatment process, so that the pore size and selective doping of the pore structure can be accurately regulated, the process is simple, and the capacity performance, the self-discharge performance and the rate performance of the capacitor carbon can be greatly improved.

In some embodiments, the present application further comprises a step of preparing a porous carbon material comprising:

In above-mentioned technical scheme, this application obtains porous carbon material through the carbonization material that carries out the carbonization to the carbon source, through the activation again, and the porous carbon material of preparation is compact, does not contain the doping site. Ultramicropores (micropores with the pore diameter less than 0.5 nm) are generated in the material in the carbonization process, and a precondition is created for subsequent hole expansion.

In some embodiments, the heat treatment of the present application further comprises a step of subjecting the heat-treated material to a second dipping treatment and a second drying treatment in an acid solution.

In the technical scheme, the material obtained by heat treatment is subjected to acid treatment and second drying treatment, so that acid molecules in the acid solution can consume part of unstable energy storage holes in advance, and further the self-discharge current under an open circuit after full electricity is reduced, and the self-discharge performance of the capacitance carbon is optimized.

The preparation method of the present application is specifically described below with reference to the examples and fig. 1:

step S10, carbonizing a carbon source in a first protective atmosphere, crushing the carbon source after carbonization to obtain a carbonized material, mixing the carbonized material with an activating agent to perform activation treatment, cooling the activated material to room temperature after activation, washing the activated material with deionized water until the pH value is less than 10, adding excessive acid, stirring for more than 30min, washing the activated material with deionized water until the pH value is 5-7, performing solid-liquid separation, and drying and crushing the obtained solid material to obtain the porous carbon material.

In the steps, the reaction raw materials are carbonized to obtain a carbonized material with ultramicropores, a foundation is provided for the subsequent preparation of an activated carbon adsorption material, and the porous carbon material with a compact structure and no doped active sites is obtained by activation, washing, drying and crushing.

In some embodiments, the carbon source comprises at least one of phenolic resin, epoxy resin, melamine resin, furfural resin, urea resin, pitch, coke, anthracite, mesocarbon microbeads, starch, sucrose, coconut shells, almond shells, date shells, and walnut shells.

In some embodiments, a curing agent is further added to the carbon source during carbonization of the carbon source to obtain a carbonized material. The curing agent is added into the carbon source, the curing agent can be used as a template agent of ultramicropores, more ultramicropores (micropores with the pore diameter less than 0.5 nm) can be generated in the carbonization and temperature rise process, better precondition is created for subsequent pore expansion, and preferably, the mixture of the carbon source and the curing agent is selected as the reaction raw material.

Specifically, the curing agent includes at least one of melamine, hexamethylenetetramine, formaldehyde, p-benzaldehyde, ammonium chloride, and ammonium acetate.

Specifically, the mass ratio of the carbon source to the curing agent may be specifically 5: 95. 10: 90. 30: 70. 50: 50. 70: 30. 95:5, etc., may be any other value within the above range, and is not limited herein.

Specifically, the mixing time of the carbon source and the curing agent may be 5min, 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min, etc., or may be other values within the above range, which is not limited herein.

In some embodiments, the carbonization temperature is 250 ℃ to 700 ℃, and may be, for example, 250 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, or the like, or may be other values within the above range, and is not limited herein, and the carbonization temperature is controlled within the above range, so as to facilitate the extraction of the thermally unstable component from the carbon source, thereby forming the ultra-microporous pores.

In some embodiments, the carbonization time is 0.5h to 24h, and the carbonization time may be, for example, 0.5h, 1h, 5h, 10h, 15h, 20h, 24h, or the like, or may be other values within the above range, which is not limited herein.

In some embodiments, the carbonization apparatus comprises any one of a tube furnace, a box furnace, a pusher kiln, and a roasting kiln.

In some embodiments, the first protective atmosphere comprises at least one of nitrogen, argon, neon, helium, xenon, and krypton.

In some embodiments, the oxygen content of the first protective atmosphere is 0.05 wt% to 1 wt%, and may be, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, and the like, although other values within the above range are also possible and are not limited herein.

In some embodiments, the size of the screen for the crushing treatment is 1mm to 5mm, and the specific screen size may be 1mm, 2mm, 3mm, 4mm, 5mm, etc., and may be other values within the above range, which is not limited herein.

In some embodiments, the activator comprises at least one of sodium hydroxide, potassium hydroxide, sodium oxide, potassium oxide, sodium carbonate, potassium bicarbonate, sodium bicarbonate, calcium oxide, and zinc chloride.

In some embodiments, the mass ratio of the activating agent to the carbonized material is (0.5-3): specifically, the mass ratio of the activating agent to the carbonized material may be 0.5: 1. 1:1. 1.5: 1. 2: 1. 2.5: 1 and 3: 1, etc., may have other values within the above range, and is not limited herein. It can be understood that the mass ratio of the activating agent to the carbonized material is controlled within the above range, which is beneficial to ensuring the activating effect of the carbonized material.

In some embodiments, the temperature of the activation treatment is 400 ℃ to 800 ℃, and the activation temperature may specifically be 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃ and the like, and may also be other values within the above range, which is not limited herein, and it is understood that the activation temperature is controlled within the above range, which is beneficial to improve the adsorption performance of the activated carbon material.

In some embodiments, the time t of the activation treatment is 0 < t ≦ 4h, and the activation time may be specifically 0.5h, 1h, 2h, 3h, 4h, etc., or may be other values within the above range, which is not limited herein.

In some embodiments, the acid is at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, phosphoric acid, perchloric acid, acetic acid, and benzoic acid. It will be appreciated that the purpose of washing the activated material with deionized water to a pH of less than 10 and adding acid is to remove excess curing agent from the material.

In some embodiments, the solid-liquid separation is by filtration or centrifugation.

In some embodiments, the temperature for drying is 80 ℃ to 150 ℃, and the specific temperature may be 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃ and the like, and may be other values within the above range, which is not limited herein.

In some embodiments, the drying time is 24h to 72h, and the specific time may be 24h, 30h, 36h, 42h, 48h, 52h, 60h, 72h, etc., or may be other values within the above range, which is not limited herein.

In some embodiments, the drying apparatus is any one of an oven, a box oven, and a double cone dryer.

In some embodiments, the pulverizing uses at least one of ball milling, jet milling, and mechanical milling, preferably mechanical milling.

In some embodiments, the median particle size of the porous carbon material obtained by grinding is 2 μm to 40 μm, and the median particle size may specifically be 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or the like, or may be other values within the above range, and is not limited herein. The median particle size of the porous carbon material is controlled within the range, so that the homogenization of particles is facilitated, and the doping of the outer surface of the activated carbon is reduced in the subsequent doping process.

Step S20, carrying out first dipping treatment, solid-liquid separation and first drying treatment on the porous carbon material in an oxidizing solution to obtain a first precursor, wherein the temperature of the first dipping treatment is 1-45 ℃.

In the above step, the oxidizing agent is filled in the ultramicropores of the porous carbon material by the first dipping treatment, the above reaction is performed at 1 to 45 ℃ to ensure that no pore expansion occurs in the first dipping treatment, and the temperature of the first dipping treatment may be 1 ℃, 5 ℃, 10 ℃, 20 ℃, 30 ℃, 40 ℃, 45 ℃ or the like, or may be other values within the above range, which is not limited herein.

In some embodiments, the oxidizing solution is prepared by: an oxidizing agent is dispersed in deionized water to obtain an oxidizing solution.

In some embodiments, the mass concentration of the oxidizing solution is 1 wt% to 90 wt%, and specifically, the mass concentration of the oxidizing solution may be 1 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or the like, and may have other values within the above range, which is not limited herein.

Optionally, the oxidizing agent comprises at least one of sulfuric acid, ammonium sulfate, hypochlorous acid, chloric acid, perchloric acid, hypobromous acid, bromic acid, pyrosulfuric acid, and ammonium persulfate, preferably, the oxidizing agent comprises at least one of concentrated sulfuric acid, ammonium sulfate, and ammonium persulfate. The oxidant selected by the application does not oxidize the first precursor at normal temperature, the first precursor can be oxidized only under heat treatment, and the oxidant does not have residue at high temperature and cannot pollute the prepared activated carbon material.

In some embodiments, the mass ratio of porous carbon material to oxidizing solution is 1: (2-20), specifically, the mass ratio of the first precursor to the oxidizing solution may be 1: 2. 1: 5. 1: 10. 1: 15. 1:20, etc., may have other values within the above range, and is not limited herein.

In some embodiments, the time of the first immersion treatment is 0.1h to 48h, specifically, the time of the first immersion treatment may be 0.1h, 1h, 12h, 24h, 36h, 48h, etc., and may be other values within the above range, which is not limited herein.

According to the method, the mass ratio of the porous carbon material to the oxidizing solution, the mass concentration of the oxidizing solution and the time of the first dipping treatment are controlled, so that the amount of the oxidant adsorbed by the dipping treatment is controlled, and the reaming degree can be regulated in subsequent operations.

In some embodiments, the solid-liquid separation treatment may be centrifugal separation or filtration separation.

In some embodiments, the temperature of the first drying process is 80 ℃ to 150 ℃, specifically, the temperature of the first drying process is 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ and 150 ℃, etc., and may be other values within the above range, which is not limited herein.

In some embodiments, the time of the first drying treatment is 24 to 72 hours. Specifically, the drying time may be 24h, 30h, 36h, 40h, 50h, 60h, 70h, 72h, etc., and may be other values within the above range, which is not limited herein, and it is understood that the temperature and time of the first drying process are controlled within the above range, which is advantageous for removing the solvent in the oxidizing solution as much as possible.

In some embodiments, the first drying treatment may be oven drying, stirring to dryness, spray drying, or the like.

And S30, mixing the first precursor obtained in the step S20 with a dopant, performing heat treatment in a second protective atmosphere, and cooling to room temperature to obtain a material obtained by heat treatment.

In the above steps, on one hand, under the heat treatment condition, the oxidizing agent in step S20 and carbon on the pore wall of the first precursor pore structure undergo an oxidation reaction to realize hole expansion, and the hole expansion can convert a part of micropores with small pore diameter and without energy storage activity into activated energy storage micropores, thereby reducing the diffusion resistance of the electrolyte and improving the capacity performance and rate performance of the activated carbon material.

On the other hand, after the first precursor and the dopant are mixed under the high-temperature condition of the heat treatment, the pore wall of the inner surface (the inner surface refers to the pore wall surface of the pore structure of the material) of the first precursor after hole expansion has energy storage activity and the adsorption performance of the pore wall is higher than that of the outer surface (the outer surface refers to the surface of the non-porous region of the material), so that the inner surface of the first precursor is easy to adsorb the oxidant in the oxidizing solution, and the oxidant reacts with carbon on the pore wall of the pore structure of the inner surface to generate carbon free radicals through the high-temperature treatment, so as to provide doping reaction sites. The first precursor has weak adsorbability on the outer surface, and is less in contact with an oxidant after being dried at high temperature, so that doping reaction sites on the outer surface are fewer, and in the reaction process, the doping reaction sites on the outer surface of the material lack doping active sites and do not occur or occur in a small amount, so that the selective doping on the inner surface of the activated carbon material can be realized.

The selective doping is carried out on the inner surface of the activated carbon material, so that the adsorption of electrolyte ions on the inner surface is facilitated, and desolvated electrolyte ions are adsorbed on the inner surface of the capacitance carbon in a full-electric state, are less influenced by a solvent and are difficult to desorb in an open circuit; solvated electrolyte ions are adsorbed on the outer surface, have a thick solvated layer, are easily interfered by a solvent, and are easily desorbed under an open circuit. Therefore, the selective doping on the inner surface can simultaneously improve the capacity performance and the self-discharge performance of the capacitance carbon. In addition, the selective doping on the inner surface can improve the electrolyte wettability and the conductivity of the inner surface, is beneficial to the electrolyte to be immersed into micropores with long diffusion distance and large diffusion steric hindrance, reduces concentration polarization and further improves the capacity performance. In addition, harmful oxygen-containing functional groups on the surface of the capacitance carbon can be removed at high temperature, self-discharge is reduced, and the self-discharge capacity retention rate is improved.

It is worth noting that the reaming process only reams the existing holes, does not create new holes, and can avoid the phenomenon of hole collapse caused by too many holes.

In some embodiments, the dopant comprises at least one of a phosphorus source, a nitrogen source, and a sulfur source, specifically, the phosphorus source comprises at least one of phosphorus trichloride, phosphorus pentoxide, triammonium phosphate, diammonium phosphate, monoammonium phosphate, phosphate esters, and red phosphorus; the nitrogen source comprises at least one of melamine, hexamethylenetetramine, ammonium chloride, dicyandiamide, urea, amino acid and ammonium bicarbonate; the sulfur source comprises at least one of thiourea, ammonium thiosulfate, and cysteine. Preferably, the dopant is a nitrogen source, and the existence of electron-rich nitrogen is beneficial to improving the electrochemical performance of the activated carbon material.

In some embodiments, the second protective atmosphere comprises at least one of nitrogen, argon, neon, helium, xenon, and krypton.

In some embodiments, the oxygen content of the second protective atmosphere is 0.05 wt% to 1 wt%, and may be, for example, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, and the like, although other values within the above range are also possible and are not limited herein.

In some embodiments, the mass ratio of the first precursor to the dopant is (70: 30) to (99: 1), and specifically, the mass ratio of the first precursor to the dopant may be 70: 30. 75: 25. 85: 15. 90: 10. 99: and 1, and the mass ratio of the first precursor to the dopant is controlled within the above range, which is not limited herein, and is advantageous for adsorption of electrolyte ions on the surface of the activated carbon and improvement of the capacity performance of the capacitance carbon.

In some embodiments, the temperature of the heat treatment is 200 ℃ to 900 ℃, specifically, the temperature of the heat treatment may be 200 ℃, 250 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃ or the like, and may be other values within the above range, but is not limited thereto, and preferably, the temperature of the heat treatment is 250 ℃ to 600 ℃, and more preferably, 300 ℃ to 500 ℃.

The heat treatment time is 0.5h to 10h, specifically, the heat treatment time may be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc., or may be other values within the above range, which is not limited herein.

The temperature and time of the heat treatment are controlled within the range, so that the oxidation reaction and the doping reaction are facilitated to be carried out, and the self-discharge capacity of the capacitance carbon material is further improved.

And S40, performing second immersion treatment on the material obtained in the step S30 after the heat treatment in an acid solution, and sequentially performing washing, solid-liquid separation, washing, second drying treatment and screening to obtain the activated carbon material.

In the steps, the material obtained by the heat treatment is subjected to second impregnation treatment through acid solubility to obtain the sulfuric acid-based capacitance carbon material, in the second impregnation treatment process, acid molecules can occupy holes which cannot stably adsorb electrolyte ions in the material obtained by the heat treatment, electrolyte consumption is reduced, the capacity which is easy to generate self-discharge is consumed in advance, the liquid absorption value and the self-discharge current can be synchronously reduced, and the comprehensive capacity and the self-discharge performance are improved. In addition, the acid molecules can reduce the liquid absorption value of the capacitance carbon, and are favorable for improving the volume specific capacity of the capacitance carbon.

In some embodiments, the acid solution comprises at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, oxalic acid, and phosphoric acid, preferably, the acid solution comprises at least one of sulfuric acid, nitric acid, phosphoric acid, and oxalic acid, and further preferably, the acid solution comprises oxalic acid.

In some embodiments, the mass ratio of the material obtained by the heat treatment to the acid solution is 1: (3-30), specifically, the mass ratio of the material obtained by heat treatment to the acid solution can be 1: 3. 1: 5. 1: 7. 1: 10. 1: 15. 1: 18. 1: 20. 1: 25. 1:30, etc., of course, may be other values within the above range, and the mass ratio of the material obtained by the heat treatment to the acid solution is greater than 1:30, the acid amount is too much, acid molecules occupy micropores capable of stably adsorbing electrolyte ions, the self-discharge capacity retention rate of the capacitance carbon is reduced, and the mass ratio of the materials obtained by heat treatment to the acid solution is less than 1:3, the amount of the acid solution is too small, so that the capacitance carbon cannot be optimized.

In some embodiments, the mass concentration of the acid solution is 1 wt% to 90 wt%, and specifically, the mass concentration of the acid solution may be 1 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, or the like, and may be other values within the above range, which is not limited herein.

In some embodiments, the second immersion time is 0.1h to 48h, and specifically, the second immersion time may be 0.1h, 1h, 2h, 5h, 10h, 12h, 20h, 24h, 48h, etc., or may be other values within the above range, which is not limited herein. Preferably, the time of the second impregnation treatment is 2 to 24 hours, and more preferably, the time of the second impregnation treatment is 5 to 12 hours.

In some embodiments, the washing liquid of the washing operation is deionized water, and the cut-off condition of the washing is pH 1 to 4, specifically, pH 1, 1.5, 2, 2.5, 3, 3.4, 4, and the like, and preferably, the cut-off condition of the washing is pH 1.5 to 3.0.

In some embodiments, the second drying process apparatus is any one of an oven, a box furnace, and a double cone dryer.

In some embodiments, the moisture content of the activated carbon material subjected to the second drying treatment is 5% or less, and the moisture content of the activated carbon material after specific drying may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or the like, or may be other values within the above range, which is not limited herein.

In some embodiments, the sieving is performed with a 200 mesh or 325 mesh sieve, and the purpose of the sieving is to remove large particle foreign matter from the activated carbon material.

The embodiment of the application further provides a super capacitor, including positive plate, negative pole piece and the diaphragm between positive plate and the negative pole piece, still include between positive plate and the diaphragm, the electrolyte of filling in the ultramicropore between negative pole piece and the diaphragm, the negative pole piece includes negative current collector and the negative electrode material who distributes on the negative current collector, wherein, positive plate includes the anodal mass flow body and distributes the anodal material on the anodal mass flow body, anodal material and negative electrode material all can be the activated carbon material of this application preparation.

In some embodiments, the mass ratio of the positive electrode material to the negative electrode material is (0.35:1) to (2.60: 1).

In some embodiments, the electrolyte is sulfuric acid or sulfate, and the electrolyte sulfate may specifically be at least one of lithium sulfate, sodium sulfate, and potassium sulfate, and in the present application, the concentration of the electrolyte is preferably 0.1mol/L to 5 mol/L.

In some embodiments, the separator is not limited in any way, and any separator known in the art may be used. The separator may be, but is not limited to, a polyethylene film, a polypropylene film, a cellulose film, or a modified polymer thereof.

In some embodiments, the present application has no special requirement on the preparation method of the supercapacitor, and the supercapacitor can be prepared by methods well known in the art, and can be a symmetric capacitor or an asymmetric capacitor.

The examples of the present application are further illustrated below in various examples. The present embodiments are not limited to the following specific examples. The present invention can be modified and implemented as appropriate within the scope of the main claim.

Example 1

(1) Mixing thermoplastic phenolic resin and hexamethylenetetramine according to a mass ratio of 95:5, carbonizing at 600 ℃ in a roasting furnace for 10 hours in a nitrogen atmosphere (oxygen content is 0.05 wt% -1 w%), crushing by using a crusher with a screen mesh size of 3mm to obtain a crushed material, mixing the crushed material and potassium hydroxide according to a mass ratio of 1:0.5, activating at 600 ℃ in a pushed slab kiln for 40min, cooling, washing with deionized water until the pH value is 10, washing with hydrochloric acid and deionized water respectively until the pH value is 5-7, centrifuging, drying, and crushing by airflow until the median particle size is 10 mu m to obtain a porous carbon material;

(2) weighing a porous carbon material and a sulfuric acid solution (the mass concentration is 30 wt%) according to the mass ratio of 1:2, adding the porous carbon material into the sulfuric acid solution at 10 ℃, uniformly stirring, carrying out first dipping treatment for 24 hours, rinsing with deionized water until the pH value is 2.5, centrifuging, and carrying out first drying treatment for 48 hours in an 80 ℃ double-cone dryer to obtain a first precursor.

(3) Uniformly mixing the first precursor obtained in the step (2) and melamine according to a mass ratio of 90:10, putting into a box-type furnace, heating to 500 ℃ in a nitrogen atmosphere (oxygen content is 0.05 wt% -1 w%), keeping the temperature for 2h, and cooling to room temperature to obtain a material obtained by heat treatment.

(4) Weighing the material obtained by heat treatment and a sulfuric acid solution (the mass concentration is 70 wt%) according to the mass ratio of 1:3, adding the material obtained by heat treatment into the sulfuric acid solution for second dipping treatment for 15 hours, washing with deionized water until the pH value is 2 +/-0.5, centrifuging, performing second drying in a box furnace until the moisture content is less than 2%, uniformly mixing VC, and sieving with 325 meshes to obtain the activated carbon material.

As shown in fig. 3, which is an SEM image of the activated carbon material prepared in example 1 of the present application, it is judged from fig. 3 that the present application obtained an activated carbon material having a uniform particle size.

As shown in fig. 4, which is an XRD pattern of the activated carbon material prepared in example 1 of the present application, it is determined from fig. 4 that the 002 diffraction peak of the activated carbon material is regular, and thus, the present application obtains an activated carbon material in which the microporous structure is not collapsed.

Example 2

(1) Mixing starch and ammonium chloride according to a mass ratio of 90:10, carbonizing for 4 hours at 650 ℃ in a box type furnace under a xenon atmosphere (oxygen content is 0.05 wt% -1 w%), crushing by using a crusher with a screen mesh micropore aperture of 3mm to obtain a crushed material, mixing the crushed material and sodium hydroxide according to a mass ratio of 1:1, activating for 60 minutes at 650 ℃ in a pushed slab kiln, cooling, washing with deionized water until the pH value is 10, washing with nitric acid and deionized water respectively until the pH value is 5-7, centrifuging, drying, and crushing by air flow until the median particle size is 3 mu m to obtain a porous carbon material;

(2) weighing a porous carbon material and an ammonium sulfate solution (the mass concentration is 10 wt%) according to the mass ratio of 1:10, adding the porous carbon material into the ammonium sulfate solution at the temperature of 20 ℃, uniformly stirring, carrying out first immersion treatment for 12 hours, rinsing with deionized water until the pH value is 2.0, centrifuging, and carrying out first drying treatment in a 120 ℃ oven for 24 hours to obtain a first precursor.

(3) Uniformly mixing the first precursor and hexamethylenetetramine according to a mass ratio of 88:12, putting the mixture into a box furnace for heat treatment, heating to 600 ℃ in a xenon atmosphere (with the oxygen content of 0.05 wt% -1 w%), preserving the heat for 1h, and cooling to room temperature to obtain a material obtained by heat treatment.

(4) Weighing a material obtained by heat treatment and an oxalic acid solution (the mass concentration is 1 wt%) according to the mass ratio of 1:10, adding the material obtained by heat treatment into the oxalic acid solution for second immersion treatment for 24 hours, washing the material with deionized water until the pH value is 3 +/-0.5, centrifuging the material, performing second drying treatment in a double-cone dryer until the moisture content is less than 3%, uniformly mixing VC, and sieving the mixture with 325 meshes to obtain the activated carbon material.

Example 3

(1) Mixing coconut shells and ammonium acetate according to the mass ratio of 10:90, carbonizing the mixture in a pushed slab kiln at 500 ℃ for 0.5h under the atmosphere of helium (the oxygen content is 0.05 wt% -1 w%), crushing the mixture by adopting a crusher with a 3mm screen, mixing the crushed material and sodium oxide according to the mass ratio of 1:1.5, activating the mixture in the pushed slab kiln at 800 ℃ for 25min, cooling the mixture, washing the mixture with deionized water until the pH value is 10, respectively washing the mixture with sulfuric acid and deionized water until the pH value is 5-7, performing suction filtration, drying and mechanical crushing to obtain a porous carbon material with the median particle size of 40 mu m.

(2) Weighing a porous carbon material and a persulfuric acid solution (the mass concentration is 15 wt%) according to the mass ratio of 1:5, adding the porous carbon material into the persulfuric acid solution at 40 ℃, uniformly stirring, performing first immersion treatment for 36 hours, rinsing with deionized water until the pH value is 1.5, centrifuging, and performing first drying in a 150 ℃ box furnace for 72 hours to obtain a first precursor.

(3) Uniformly mixing the first precursor and ammonium chloride according to a mass ratio of 99:1, putting the mixture into a box furnace for heat treatment, heating to 200 ℃ in a helium atmosphere (oxygen content is 0.05 wt% -1 w%), preserving heat for 10 hours, and cooling to room temperature to obtain a material obtained by heat treatment.

(4) Weighing the material obtained by heat treatment and a phosphoric acid solution (the mass concentration is 50 wt%) according to the mass ratio of 1:5, adding the material obtained by heat treatment into the phosphoric acid solution for second immersion treatment for 48 hours, washing with deionized water until the pH value is 4.0, centrifuging, drying until the moisture content is less than 5%, performing second drying in an oven, uniformly mixing VC, and sieving with 325 meshes to obtain the capacitance activated carbon material.

Example 4

(1) Mixing melamine resin and formaldehyde according to the mass ratio of 5:95, carbonizing at 250 ℃ in a roasting furnace for 20 hours under the argon atmosphere (the oxygen content is 0.05 wt% -1 w%), crushing by a crusher with the screen size of 3mm to obtain a crushed material, mixing the crushed material and potassium hydroxide according to the mass ratio of 1:3, activating at 25 ℃ in a push plate kiln for 2 hours, cooling, washing with deionized water until the pH value is 10, washing with hydrochloric acid and deionized water respectively until the pH value is 5-7, centrifuging, drying, and crushing by airflow until the median particle size is 2 mu m to obtain a porous carbon material;

(2) weighing a porous carbon material and a sulfuric acid solution (the mass concentration is 30 wt%) according to the mass ratio of 1:2, adding the porous carbon material into the sulfuric acid solution at 45 ℃, uniformly stirring, carrying out first dipping treatment for 48 hours, rinsing with deionized water until the pH value is 2.5, centrifuging, and carrying out first drying treatment for 24 hours in a 150 ℃ double-cone dryer to obtain a first precursor.

(3) And (3) uniformly mixing the first precursor obtained in the step (S20) and urea according to the mass ratio of 70:30, putting the mixture into a box furnace for heat treatment, heating to 900 ℃ in a nitrogen atmosphere (the oxygen content is 0.05 wt% -1 w%), preserving the heat for 0.5h, and cooling to room temperature to obtain a material obtained by heat treatment.

(4) Weighing the material obtained by heat treatment and an acetic acid solution (the mass concentration is 70 wt%) according to the mass ratio of 1:30, adding the material obtained by heat treatment into the sulfuric acid solution for second immersion treatment for 5 hours, washing with deionized water until the pH value is 2 +/-0.5, centrifuging, performing second drying in a box furnace until the moisture content is less than 2%, uniformly mixing VC, and sieving with 325 meshes to obtain the activated carbon material.

Example 5

(1) Mixing thermoplastic phenolic resin and hexamethylenetetramine according to a mass ratio of 80:20, carbonizing at 700 ℃ in a roasting furnace for 24 hours in a neon atmosphere (oxygen content is 0.05 wt% -1 w%), crushing by using a crusher with a screen mesh size of 3mm to obtain a crushed material, mixing the crushed material and potassium hydroxide according to a mass ratio of 1:1.3, activating at 600 ℃ for 4 hours in a push plate kiln, cooling, washing with deionized water until the pH value is 10, washing with hydrochloric acid and deionized water respectively until the pH value is 5-7, centrifuging, drying, and crushing by air flow until the median particle size is 5 mu m to obtain the porous carbon material.

(2) Weighing a porous carbon material and a sulfuric acid solution (the mass concentration is 30 wt%) according to the mass ratio of 1:2, adding the porous carbon material into the sulfuric acid solution at 1 ℃, uniformly stirring, carrying out first dipping treatment for 0.1h, rinsing with deionized water until the pH value is 2.5, centrifuging, and carrying out first drying treatment in a 100 oven for 24h to obtain a first precursor.

(3) Uniformly mixing the first precursor and ammonium bicarbonate according to a mass ratio of 90:10, putting the mixture into a box furnace for heat treatment, heating to 500 ℃ in a neon atmosphere (the oxygen content is 0.05 wt% -1 w%), preserving the heat for 3 hours, and cooling to room temperature to obtain a material obtained by heat treatment.

(4) Weighing a material obtained by heat treatment and a nitric acid solution (the mass concentration is 98 wt%) according to the mass ratio of 1:20, adding the material obtained by heat treatment into the sulfuric acid solution for second impregnation treatment for 0.1h, washing with deionized water until the pH value is 2 +/-0.5, centrifuging, performing second drying in a box furnace until the moisture content is less than 2%, uniformly mixing VC, and sieving with 325 meshes to obtain the activated carbon material.

Example 6

Different from the example 1, the carbon source in the step (1) adopts the thermoplastic phenolic resin, the curing agent is not added, and the other conditions are the same.

Example 7

In contrast to example 1, the "melamine" in step (3) was replaced by "ammonium dihydrogen phosphate".

Example 8

In contrast to example 1, the "melamine" in step (3) was replaced by "thiourea".

Comparative example 1

Unlike example 1, step (2) was not performed.

Comparative example 2

Unlike example 1, step (3) was not performed.

Comparative example 3

Unlike example 1, steps (2) and (3) were not performed.

Comparative example 4

Unlike example 1, step (4) was not performed.

And (3) performance testing:

(1) SEM pictures were tested by Hitachi Hitachi S4800 scanning electron microscopy. The mass content of the doping element (N, P, S) was tested by scanning electron microscopy in combination with X-ray spectroscopy at 1000X. A cross-sectional sample can be obtained by cutting the activated carbon material with a high energy argon ion beam. Mass ratio of doped element region: under 1000 times, the ratio of the total mass content of doping elements in the cross-section area of the cross-section sample to the total mass content of doping elements in the surface area of the non-cross-section sample. Wherein, the total mass content of the doping elements in the cross-section area mainly reflects the content of the doping elements in the hole area (inner surface), and the total mass content of the doping elements in the surface area mainly reflects the content of the doping elements in the non-hole area (outer surface).

(2) XRD was tested using a Panalytical X' Pert PRO MPD.

(3) The nitrogen adsorption-desorption test was performed at 77K using a macometer tester, and the specific surface area was calculated by the BET formula, the results of which are shown in table 1. Micropore pore size distribution was calculated from adsorption branch data using Quenched Solid Density Function Theory (QSDFT) and based on a slit-shaped pore (slit-shaped pore) model.

(4) Conductivity test method: the activated carbon powder is put into a sample tank by adopting a Mitsubishi chemical MCP-PD51 powder conductivity tester, and the conductivity is tested under the pressure of 63.66 MPa.

(5) The acid radical ions are tested by an ion chromatograph ICS-3000.

(6) Method for testing liquid absorption value (g/g): weighing a plurality of parts of the activated carbon material prepared by the method, adding 1g of 1M sulfuric acid into each part of the activated carbon material, fully stirring the mixture for about 10min by using a glass rod, and when one part of the activated carbon material is converted into flowing and glossy slurry and the other part of the activated carbon material still has redundant powder, and the mass value of the 1M sulfuric acid is within 0.02 of that of the two critical conditions, the minimum 1M sulfuric acid weight of the activated carbon material converted into the flowing and glossy slurry is the liquid absorption value; if the fluidity and glossy slurry do not exist at the same time and the excessive powder exists partially, the mass range of the 1M sulfuric acid needs to be adjusted for retesting until the fluidity and glossy slurry and the excessive powder exist at the same time.

(7) The capacitance performance of the sulfuric acid capacitor activated carbon is evaluated by adopting a symmetrical double-electrode system, and the process is as follows: accurately weighing the activated carbon, the Super P conductive agent and the polytetrafluoroethylene adhesive in a mass ratio of 80:15:5, adding a certain amount of isopropanol, uniformly stirring to form slurry, rolling the slurry to a thickness of about 100 mu m, and punching micropores to form an electrode wafer with a diameter of 13 mm. Vacuum drying the electrode plate at 120 deg.C for more than 12 hr, and weighing to obtain active substance with mass of about 3 + -0.3 mg.cm on single electrode^-2. Pressing the dried and weighed electrode sheet on a current collector (titanium mesh), separating two symmetrical current collectors/electrodes with two layers of microporous fibrous membranes, soaking them in 1M H₂SO₄In the solution, it was then wrapped with parafilm sealing film and dipped for more than 5h for further testing. Performed on CHI660D electrochemical workstation.

The method for testing the specific capacity, the comprehensive specific capacity and the rate retention rate comprises the following steps:

constant current charge and discharge tests are carried out by adopting a current density of 0.25A/g and a multiplying power conservation rate of 20A/g, and the voltage range is 0V-0.9V. Specific capacity (C) of the capacitor_m) According to the constant current discharge curve, the following formula is adoptedCalculating:

wherein I is constant current (A), m represents total mass (g) of the two electrode plates, and dV/dt (V/s) is more than V on discharge curve_max～V_maxThe/2 range (V)_maxInitial discharge voltage) was fitted to the data. Current density of 0.25A/g, C_mRepresents the specific mass capacity of the activated carbon.

The rate retention rate is the ratio of 20A/g specific capacity and 0.25A/g specific capacity.

Comprehensive specific capacity (C)_{Synthesis of}) The calculation formula of (2):

C_{synthesis of}＝C_m/(1+ imbibition number)

The comprehensive specific capacity represents the comprehensive capacity performance of the electrolyte and the activated carbon and is directly related to the energy density of an actual capacitor.

(8) Self-discharge retention test method: and charging to 0.9V working voltage by adopting a constant current, keeping the constant voltage for 120min, and then opening the circuit, thereby obtaining the open-circuit voltage-time relation. The voltage value at 30h after the discharge retention rate is open circuit is the ratio of U (V) to the initial voltage of 0.9 (V).

TABLE 1 doping element content, micropore size distribution and conductivity test results for each example and comparative example

As can be seen from Table 1: the activated carbon material prepared in embodiments 1 to 5 is prepared by performing a first impregnation treatment on a porous carbon material at a temperature of 1 ℃ to 45 ℃ to fill an oxidant in an oxidizing solution into a pore structure, wherein no pore expansion occurs during the filling process, and then mixing the porous carbon material with a dopant and performing a heat treatment, wherein during the heat treatment, the purpose of pore expansion can be achieved, and the active carbon material can be doped on the surface of the pore wall of the pore structure of the activated carbon (i.e., the inner surface of the activated carbon material) in a concentrated manner, i.e., selective doping is achieved, so that the capacity performance, the rate performance and the self-discharge performance of the capacitive carbon are improved at the same time.

The mass content of the doping element in the activated carbon material of example 1 is higher than that of comparative examples 1 and 2, indicating that the oxidation reaction occurred in the pore structure of the first precursor during the heat treatment promoted the doping reaction, and the nitrogen content of comparative examples 1 and 2 is equivalent to that of comparative example 3 indicating that the oxidation reaction did not occur and the doping reaction hardly occurred. The pore volume below 1nm and the total pore volume of example 1 and comparative example 1 were higher than those of comparative example 2, and it was demonstrated that pore enlargement could be achieved by performing an oxidation reaction under heat treatment conditions after the first precursor adsorbed the oxidant.

As can be seen from Table 1: the ratio of the total mass content of doping elements in the cross-sectional area to the total mass content of doping elements in the surface area of example 1 is higher than that of comparative example 3, which shows that the doping elements are mainly doped on the surface (inner surface) of the porous area and on the non-porous area (outer surface) of the activated carbon material of the present application.

TABLE 2 capacitive Performance test data for each example and comparative example

As can be seen from Table 2: the active carbon materials prepared in the embodiments 1 to 8 have excellent comprehensive specific capacity (20.76F/g to 27.21F/g) and obviously higher self-discharge retention rate and rate retention rate than those of the comparative examples 1 to 3, and show that the active carbon materials prepared in the application have excellent capacity performance, rate performance and self-discharge performance in a sulfuric acid capacitor system.

Example 1 has a specific surface area, a pore volume below 1nm, a total pore volume, a ratio of the total mass content of doping elements in the cross-sectional region to the total mass content of doping elements in the surface region, and a content of doping elements (nitrogen) higher than those of example 6, because the curing agent can be used as a template for ultra-micropores, which are converted into active energy storage ultra-micropores during the subsequent pore expansion process, to generate ultra-micropores (micropores smaller than 0.5 nm) during the carbonization process. So the corresponding capacity, rate and self-discharge performance are more excellent. The raw material of example 1 is a mixture of a carbon source and a curing agent, and the raw material of example 6 is only a carbon source, thereby showing that the pore-enlarging modification and doping modification effects are better in the case that the raw material of S10 contains a curing agent.

According to the results, the pore volume and the total pore volume below 1nm of the embodiment 1 are larger than those of the embodiments 7 and 8, and the corresponding specific mass capacity, comprehensive specific capacity, self-discharge retention rate and rate retention rate are better than those of the embodiments 7 and 8. Therefore, the doping effect of nitrogen is obviously better than that of phosphorus and sulfur.

Among them, the comprehensive specific capacity relationship is example 1 > comparative example 2 because:

firstly, the doping improves the capacity performance of the activated carbon. Compared with the comparative example 1, the first precursor of the example 1 absorbs the sulfuric acid and then reacts with the nitrogen source through heat treatment at high temperature, doping is carried out, and the nitrogen content (2.8%) is higher than that (0.3%) of the comparative example 1. On one hand, nitrogen doping contributes to pseudo capacitance and improves capacity performance; on the other hand, the nitrogen doping improves the conductivity of the activated carbon, and reduces the polarization; finally, the wettability of the electrolyte is enhanced by nitrogen doping, so that the electrolyte can be favorably diffused into the activated carbon, and the electrochemical process can be favorably carried out.

Secondly, the active adsorption sites of the electrolyte ions are improved by oxidation reaming, thereby improving the capacity performance. The pore volume of 1nm or less and the total pore volume of example 1 were higher than those of comparative example 2, and it was demonstrated that pore enlargement was achieved in the oxidation reaction with the oxidizing solution, and that it was possible to convert part of the micropores having no electrolyte adsorption activity into micropores having electrolyte adsorption activity.

The relationship of the multiplying power performance is that the embodiment 1 is larger than the comparative example 2, which shows that the diffusion internal resistance of electrolyte ions in the activated carbon can be reduced through oxidation hole expansion, and the multiplying power performance is improved.

As shown in fig. 5, which is a schematic diagram of the structure-activity relationship between the activated carbons of example 1 and comparative example 3 of the present application, in comparative example 3, step S20 and step S30 are not performed, and neither pore expansion nor doping is performed, and the specific mass capacity, the self-discharge retention rate, and the rate retention rate are lower than those of examples 1 to 8 and comparative examples 1 to 2.

The self-discharge capacity retention rate of the embodiment 1 is larger than that of the comparative example 4, the mass specific capacity is smaller than that of the comparative example 4, the liquid absorption value is reduced, and the comprehensive specific capacity is equivalent to that of the latter. Example 1 is acid-modified relative to comparative example 4, which shows that acid modification can occupy unstable micropores of electrolyte adsorption, and consume unstable capacity in advance, thereby improving self-discharge performance. The comprehensive specific capacity of example 1 is comparable to comparative example 4, mainly due to the decreased liquid absorption value.

Claims

1. The activated carbon material is characterized in that a pore structure is formed inside the activated carbon material, the surface of the pore wall of the pore structure contains doping elements, and the total volume of the pore structure is 0.40cm³/g～0.80cm³(ii)/g, volume of pore structure having pore diameter of 1nm or more is 0.25cm or more³/g。

2. The activated carbon material of claim 1, comprising at least one of the following characteristics a-d:

3. The activated carbon material of claim 1, comprising at least one of the following characteristics a-j:

a. of said activated carbon materialThe tap density is 0.55g/cm³～0.75g/cm³；

b. The pH value of the activated carbon material is 1-4;

c. the median particle size of the activated carbon material is 0.5-40 μm;

d. the acid radical content in the activated carbon material is 500-80000 ppm;

g. the specific mass capacity of the activated carbon material is 58F/g-80F/g;

4. A method for preparing an activated carbon material, the method comprising:

carrying out first dipping treatment and first drying treatment on a porous carbon material in an oxidizing solution to obtain a first precursor, wherein the first dipping treatment is carried out at the temperature of 1-45 ℃;

5. The method of claim 4, further comprising:

6. The method according to claim 5, characterized in that it comprises at least one of the following features a to o:

b. the charring atmosphere comprises a first protective atmosphere;

e. the carbonization temperature is 250-700 ℃;

f. the carbonization time is 0.5-24 h;

m, the temperature of the activation treatment is 400-800 ℃;

the porous carbon material has a median particle diameter of 2 to 40 μm.

7. The method according to claim 4, characterized in that it comprises at least one of the following features a to g:

b. the time of the first dipping treatment is 0.1-48 h;

e. the mass concentration of the oxidizing solution is 1-90 wt%;

f. the temperature of the first drying treatment is 80-150 ℃;

g. the time of the first drying treatment is 24-72 h.

8. The method according to claim 4, characterized in that it comprises at least one of the following features a to g:

b. the mass ratio of the first precursor to the dopant is (70-99): (1-30);

c. the heat treatment is carried out in a second protective gas atmosphere;

f. the temperature of the heat treatment is 200-900 ℃;

g. the time of the heat treatment is 0.5 h-10 h.

9. The method according to claim 4, wherein the heat treatment further comprises a step of subjecting the heat-treated material to a second dipping treatment and a second drying treatment in an acid solution.

10. The method according to claim 9, characterized in that it comprises at least one of the following features a to e:

c. the mass concentration of the acid solution is 1 wt% -98 wt%;

d. the time of the second dipping treatment is 0.1-48 h;

e. and the water content in the material obtained after the second drying treatment is less than or equal to 5 percent.

11. A super capacitor, characterized in that the super capacitor comprises the activated carbon material according to any one of claims 1 to 3 or the activated carbon material prepared by the preparation method according to any one of claims 4 to 10.