CN113903598B

CN113903598B - Activated carbon material, preparation method thereof and supercapacitor

Info

Publication number: CN113903598B
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: 2023-09-12
Anticipated expiration: 2041-09-24
Also published as: CN113903598A

Abstract

The application relates to an active carbon material, a preparation method thereof and a super capacitor, wherein a pore structure is formed in the active carbon material, the surface of the pore wall of the pore structure contains doping elements, and the total volume of the pore structure is 0.40cm ³ /g～0.80cm ³ Per g, pore structure volume within 1nm of 0.25cm or more ³ The active carbon material prepared by the application 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 basically does not have energy storage activity, so that the doping elements are only effectively doped in the pore structure, thereby promoting the adsorption of the capacitance carbon to electrolyte ions, and further improving the capacity and self-discharge performance of the active carbon material.

Description

Activated carbon material, preparation method thereof and supercapacitor

Technical Field

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

Background

The birth of the super capacitor innovates the life style of people and has epoch-making significance. In recent years, the market demand for supercapacitors has shown a well-blown development. Sulfuric acid capacitors are 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 active 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 uses sulfuric acid solution as electrolyte and active carbon as electrode active material, and has high requirement on the capacity and self-discharge performance of electrode active carbon material.

At present, the development of an active carbon material for capacitor electrodes (hereinafter referred to as capacitor carbon) has the following technical difficulties:

the directional doping of the area is difficult to realize by the doping modification of the capacitance carbon, and the effective doping is difficult to realize. The surface of the capacitor carbon is a main place for energy storage, and the surface of the capacitor carbon is divided into an inner surface (pore area surface) and an outer surface (non-pore area surface). In the full-electric state, desolvation electrolyte ions are adsorbed on the inner surface, so that the desolvation electrolyte ions are less influenced by a solvent and are difficult to desorb under an open circuit; the solvated electrolyte ions are adsorbed on the outer surface, and a thicker solvating layer is formed, so that the solvating electrolyte ions are easy to be interfered by solvents and are easy to be desorbed under open circuit. The heteroatom doping can promote the adsorption of the capacitor carbon to electrolyte ions, the ideal doping mode of the capacitor carbon is that the heteroatom is doped on the inner surface, and the doping can simultaneously promote 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 pore size of the inner pores of the material.

Therefore, developing an active carbon material with accurately adjustable aperture size, selective doping and high capacity is a technical problem in the field of development of supercapacitor electrode materials.

Disclosure of Invention

In order to overcome the defects, the application provides the active carbon material, the preparation method thereof and the super capacitor, which can obtain the active carbon material with precisely regulated pore size and selectively doped on the inner surface of the material, and can effectively improve the capacity performance and the self-discharge performance of the active carbon material.

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 pore wall surface of the pore structure contains a doping element, and a total volume of the pore structure is 0.40cm ³ /g～0.80cm ³ Per g, pores with a pore diameter of less than 1nmThe structural volume is more than or equal to 0.25cm ³ /g。

With reference to 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 the doping elements in the cross section area of the active carbon material to the total mass content of the doping elements in the surface area of the active 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 active carbon material is 0.01% -8%.

With reference to the first aspect, the activated carbon material includes at least one of the following features a to j:

a. The tap density of the active carbon material is 0.55g/cm ³ ～0.75g/cm ³ ；

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

c. the median particle diameter of the activated carbon material is 0.5-40 mu m;

d. the acid radical content in the active carbon material is 500 ppm-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 of the activated carbon material is less than or equal to 5%;

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

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

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

j. the specific surface area of the active carbon material is 900m ² /g～1300m ² /g。

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

performing first impregnation 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 impregnation treatment is 1-45 ℃;

and mixing the first precursor and the doping agent, and then performing heat treatment to obtain the active carbon material.

With reference to the second aspect, the method further includes:

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

With reference to the second aspect, the method includes 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-formaldehyde resin, asphalt, coke, anthracite, mesophase carbon microspheres, starch, sucrose, coconut husk, almond husk, jujube husk and walnut husk;

b. the charred atmosphere comprises a first protective atmosphere;

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

d. the carbonized atmosphere comprises a first protective atmosphere, wherein 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 hours;

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, a curing agent is also added into the carbon source, and 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, a curing agent is also added into the carbon source, and the mixing time of the carbon source and the curing agent is 5-120 min;

k. 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;

and l, the mass ratio of the activator to the carbonized material is (0.5-3): 1, a step of;

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 hours;

and the median particle diameter of the porous carbon material is 2-40 mu m.

With reference to 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, wherein 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;

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 includes at least one of a phosphorus 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 performed in a second protective gas atmosphere;

d. the heat treatment is performed 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, wherein the oxygen content of the second protective gas 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 material obtained by the heat treatment to a second impregnation treatment and a second drying treatment in an acid solution.

With reference to 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 1-98 wt%;

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

e. and the moisture content of the material obtained by the second drying treatment is less than or equal to 5%.

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 the advantages that the inside of the material contains a pore structure, the surface of the pore wall of the pore structure contains doping elements, compared with the existing active carbon material, the pore structure formed by the active carbon material has the advantages that the pore volume of pores with the pore diameter within 1nm is increased, the total volume of the pore structure of the active carbon material is further increased, the pore structure has certain energy storage activity, the capacity performance of the capacitance carbon material can be improved, the diffusion steric hindrance of electrolyte is reduced, and the multiplying power performance is improved; the doped elements can promote the adsorption of the capacitance carbon to electrolyte ions in the pore structure of the material, thereby improving the capacity and self-discharge performance of the active carbon material.

(2) According to the application, the porous carbon material is subjected to first impregnation treatment at the temperature of 1-45 ℃, the oxidant in the oxidizing solution is filled into the pores, reaming does not occur in the filling process, then the porous carbon material is mixed with the dopant and then subjected to heat treatment, the purpose of reaming can be achieved in the heat treatment process, doping can be concentrated on the pore wall surface of the pore structure of the activated carbon (namely the inner surface of the activated carbon material), namely selective doping is realized, and the capacity performance, the multiplying power performance and the self-discharge performance of the capacitor carbon are improved simultaneously. The preparation method disclosed by the application is used for doping and reaming simultaneously, can realize accurate regulation and control of aperture size and selective doping, is simple in process, and can greatly improve the capacity performance and the multiplying power performance of the capacitor carbon.

Drawings

The application will be further described with reference to the drawings and examples.

FIG. 1 is a schematic diagram of a preparation flow of an activated carbon material of the present application;

FIG. 2 is a schematic diagram of the preparation process of the activated carbon material of the present application;

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

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

FIG. 5 is a comparative diagram showing the structure-activity relationship of the preparation process of example 1 and comparative example 3 of the present application.

Detailed Description

For a better understanding of the technical solution of the present application, the following detailed description of the embodiments of the present application refers to the accompanying drawings.

It should be understood that the described embodiments are merely some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in 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 relationship describing the association of the associated objects, meaning that there may be three relationships, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

The active carbon material has the advantages of good conductivity, low cost, easy adjustment of specific surface area and the like, is a main electrode material of the super capacitor, is difficult to realize effective doping and regional directional doping (material internal doping) due to the doping modification of the conventional sulfuric acid capacitor capacitance carbon material, and has difficult precise adjustment of the micropore pore size distribution of the capacitance carbon, so that the capacitance performance of the capacitor is poor.

The embodiment of the application provides an active carbon material, wherein a pore structure is formed in the active 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 0.40cm ³ /g～0.80cm ³ And/g, the pore volume of the pore structure with the pore diameter within 1nm is more than or equal to 0.25cm ³ /g。

In the technical scheme, compared with the existing active carbon material, the pore structure formed by the active carbon material has the advantages that the pore volume of pores with the pore diameter within 1nm is increased, the total volume of the pore structure of the active carbon material is further increased, the pore structure has certain energy storage activity, the capacity performance of the capacitance carbon material can be improved, the diffusion steric hindrance of electrolyte is reduced, and the rate performance is improved; the doped elements can promote the adsorption of the capacitance carbon to electrolyte ions in the pore structure of the material, thereby improving the capacity and self-discharge performance of the active carbon material.

In particular, the total volume of the pore structure may be in particular 0.40cm ³ /g、0.45cm ³ /g、0.50cm ³ /g、0.55cm ³ /g、0.60cm ³ /g、0.65cm ³ /g、0.70cm ³ /g、0.75cm ³ /g、0.80cm ³ Of course, the values of the ratio/g and the like may be other values within the above-mentioned range, and are not limited thereto. The total volume of the pore structure is less than 0.40cm ³ /g, the energy storage active site is insufficient; the total volume of the pore structure is greater than 0.80cm ³ And/g, the pore structure is liable to collapse. Pore volume of pore structure with pore diameter within 1nm can be 0.25cm ³ /g、0.27cm ³ /g、0.29cm ³ /g、0.32cm ³ /g、0.35cm ³ /g, etc., preferably 0.29cm or more in pore structure volume with a pore diameter within 1nm ³ And/g, it can be understood that the pore structure in the activated carbon material is used for electrolyte ion energy storage, and the total volume of the pore structure and the pore structure with the pore diameter within 1nm are limited in the range, so that the energy density of the activated carbon is improved.

In some embodiments, the pore structure includes micropores, where the micropores refer to pores having a pore diameter of less than 2nm, and the volume ratio of the micropores in the pore structure is 85% -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%, 95%, and the like, and of course, other values in the above range may also be used, where the volume ratio of the micropores in the pore structure is controlled within the above range, which is beneficial to improving the capacity performance of the activated carbon material.

In some embodiments, the ratio of the total mass content of doping elements of the cross-sectional area of the activated carbon material to the total mass content of doping elements of 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-section 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., and of course, other values within the above range may be also used, which is not limited herein. It can be understood that the cross section area is the cross section surface of the activated carbon material obtained by cutting the activated carbon material by using the high-energy argon ion beam, the total mass content of the doping elements in the cross section area mainly reflects the content of the doping elements on the inner surface of the activated carbon material, the surface area is the 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 the pore area of the activated carbon material, the doping elements are distributed on the pore wall surface of the pore structure (namely the inner surface of the activated carbon material) in the activated carbon material, the adsorption of electrolyte ions on the inner surface of the pore structure of the activated carbon can be promoted, and the capacity performance and the self-discharge performance of the capacitor carbon can be simultaneously promoted. In addition, the doping elements are distributed on the surface of the pore structure in the active carbon material, so that the wettability and conductivity of the electrolyte on the inner surface of the active carbon material can be improved, the electrolyte can be immersed into the pores 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 includes at least one of nitrogen, phosphorus, and sulfur. Preferably, the doping element is a nitrogen source, and the nitrogen source has electron-rich nitrogen groups, which is beneficial to improving the electrochemical performance of the activated carbon material.

In some embodiments, the mass content of the doping element in the activated carbon material is 0.01% -8%, the mass content of the doping element in the activated carbon material may be specifically 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc., and of course, other values within the above range may be also used, 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 improving the capacity performance of the activated carbon material.

In some embodiments, the activated carbon material has a tap density of 0.55g/cm ³ ～0.75g/cm ³ Specifically, the tap density of the activated carbon material is 0.55g/cm ³ 、0.60g/cm ³ 、0.65g/cm ³ 、0.70g/cm ³ And 0.75g/cm ³ And the like, but of course, other values within the above range are also possible, and are not limited thereto.

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., but may be other values within the above range, and is not limited thereto, and preferably the pH of the activated carbon material is 1.5 to 3.0.

In some embodiments, the median particle diameter of the activated carbon material is 0.5 μm to 40 μm, specifically, the median particle diameter 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., but other values within the above range are also possible, and the median particle diameter of the activated carbon material is controlled within the above range, which is advantageous 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 radical content in the activated carbon material is 500ppm to 80000ppm, and the acid radical content in the activated carbon material may be 500ppm, 1000ppm, 2000ppm, 3000ppm, 10000ppm, 20000ppm, 30000ppm, 40000ppm, 50000ppm, 60000ppm, 70000ppm, 80000ppm, etc., but may also be other values within the above range, and is not limited thereto.

In some embodiments, the activated carbon material has an activated carbon liquid absorption value of 1.30g/g to 2.00g/g, and the activated carbon material may have an activated carbon liquid absorption 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, or the like, which may be, of course, other values within the above range, without limitation, and it is understood that controlling the activated carbon liquid absorption value of the activated carbon material within the above range is beneficial to 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 of course, other values within the above range may be also used, which is not limited herein, and the moisture content of the activated carbon material is controlled within the above range, which is beneficial to improving 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., but may be other values within the above range, and is not limited thereto.

In some embodiments, the specific combined capacity of the activated carbon material is 20F/g to 28F/g, and the specific combined 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., although other values within the above ranges are also possible, and are not limited thereto.

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

In some embodiments, the activated carbon material has a specific surface area of 900m ² /g～1300m ² Specific surface area of the activated carbon material may be 900m ² /g、1000m ² /g、1100m ² /g、1200m ² /g、1300m ² Of course, the specific surface area of the activated carbon material is controlled within the above range, and the specific surface area of the activated carbon material is preferably 1000m ² /g～1200m ² /g。

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

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, the oxidant in the oxidizing solution is filled into the pores of the porous carbon material to obtain a first precursor, oxidation reaction and pore expansion are not required to occur in the filling process, then the first precursor and the dopant are mixed and then subjected to heat treatment, in the heat treatment process, the inner surface of the material (the inner surface of the material refers to the pore wall surface of the pore structure of the material) is subjected to oxidation reaction and doping reaction, 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 not having energy storage activity to having energy storage activity, the pore structure having energy storage activity can realize doping reaction, and the outer surface (the outer surface refers to the surface of a non-pore area 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 obviously smaller than the pore diameter D2 of the pore structure obtained by heat treatment, in the heat treatment, in addition, in the inner surface of the material obtained by the heat treatment has doping elements (M in fig. 2) represents doping elements, the pore diameter of the pore structure, the doping element in the pore diameter can be obtained by the heat treatment, the pore structure has high doping performance, the capacity and the high-discharging performance can be realized, the high-level carbon preparation performance can be realized, and the high-accuracy and pore expansion performance can not be realized, and the preparation performance can be realized, and the high-level, and pore expansion performance can be realized, and the preparation performance can be realized, and has high performance and performance.

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

In the technical scheme, the carbonized material obtained by carbonizing the carbon source is activated to obtain the porous carbon material, and the prepared porous carbon material is compact and does not contain doping sites. Super-micropores (micropores with the aperture smaller than 0.5 nm) are generated in the material in the carbonization process, so that preconditions are created for subsequent reaming.

In some embodiments, the heat treatment of the present application further comprises the step of subjecting the heat treated material to a second impregnation 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 partial unstable energy storage holes in advance, and then the self-discharge current in an open circuit after full electricity is reduced, and the self-discharge performance of the capacitor carbon is optimized.

The following specifically describes the preparation method of the present application with reference to the example and fig. 1:

and S10, carbonizing a carbon source in a first protective atmosphere, crushing the carbonized carbon source to obtain carbonized material, mixing the carbonized material with an activating agent, activating the carbonized material, cooling the activated carbonized material to room temperature, 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 the carbonized material with the ultra-micropores, which provides a basis for the subsequent preparation of the activated carbon adsorption material, and then activated, washed, dried and crushed to obtain the porous carbon material with compact structure and no doped active sites.

In some embodiments, the carbon source comprises at least one of phenolic resin, epoxy resin, melamine resin, furfural resin, urea-formaldehyde resin, pitch, coke, anthracite, mesophase carbon microspheres, starch, sucrose, coconut husk, almond husk, jujube husk, and walnut husk.

In some embodiments, a curing agent is also added to the carbon source during carbonization of the carbon source to produce a carbonized material. The curing agent is added into the carbon source, the curing agent can be used as a template agent of the ultra-micropores, more ultra-micropores (micropores with the aperture smaller than 0.5 nm) can be generated in the carbonization heating process, a better precondition is created for subsequent reaming, and preferably, the reaction raw materials are a mixture of the carbon source and the curing agent.

Specifically, the curing agent comprises 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 specifically be 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 thereto.

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., but may also be other values within the above range, which is not limited herein.

In some embodiments, the carbonization temperature is 250 ℃ to 700 ℃, and the carbonization temperature may be, for example, 250 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, or the like, and of course, other values within the above range are also possible, and the carbonization temperature is not limited herein, so that the carbonization temperature is controlled within the above range, and the removal of thermally unstable components in the carbon source is facilitated, thereby forming the ultramicropores.

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, etc., but may be other values within the above range, and is not limited thereto.

In some embodiments, the carbonization device comprises any one of a tube furnace, a box furnace, a pusher kiln, and a firing 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 0.05wt% to 1wt%, for example, may be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, etc., but may be other values within the above range, and is not limited thereto.

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., but may be other values within the above range, without limitation.

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 activator to char is (0.5-3): 1, specifically, the mass ratio of the activator to the charring material may be 0.5: 1. 1: 1. 1.5: 1. 2: 1. 2.5:1 and 3:1, etc., may be any other value within the above range, and is not limited thereto. 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 ℃, the activation temperature may specifically be 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, etc., but of course, other values within the above range are also possible, and the activation temperature is not limited herein, and it is understood that the activation temperature is controlled within the above range, which is beneficial to improving the adsorption performance of the activated carbon material.

In some embodiments, the time t of the activation treatment is 0 < t.ltoreq.4h, and the activation time may be specifically 0.5h, 1h, 2h, 3h, 4h, etc., but 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 means of solid-liquid separation is filtration or centrifugation.

In some embodiments, the temperature of the drying is 80 to 150 ℃, and the specific temperature may be 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, etc., but may be other values within the above range, and the drying is not limited thereto.

In some embodiments, the drying time is 24 h-72 h, and the specific time may be 24h, 30h, 36h, 42h, 48h, 52h, 60h, 72h, etc., but 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-type furnace, and a double cone dryer.

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

In some embodiments, the median particle diameter of the crushed porous carbon material is 2 μm to 40 μm, and the median particle diameter may be specifically 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or the like, but may be other values within the above range, and is not limited thereto. The median particle diameter 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.

And step S20, performing first impregnation 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 impregnation treatment is 1-45 ℃.

In the above step, the oxidizing agent is filled in the micropores of the porous carbon material by the first impregnation treatment, and the reaction is performed at a temperature of 1 to 45 ℃ to ensure that no pore expansion occurs during the first impregnation treatment, and the temperature of the first impregnation treatment may be 1 ℃, 5 ℃, 10 ℃, 20 ℃, 30 ℃, 40 ℃, 45 ℃ or the like, and of course, other values within the above range may be used, without limitation.

In some embodiments, the oxidizing solution is prepared by the following method: and dispersing an oxidant in the deionized water to obtain an oxidizing solution.

In some embodiments, the mass concentration of the oxidizing solution is 1wt% to 90wt%, specifically, the mass concentration of the oxidizing solution may be 1wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt%, etc., but may be other values within the above range, without limitation.

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, and 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, can oxidize the first precursor only by heat treatment, has no residue after high temperature, and can not 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 be other values within the above range, and is not limited thereto.

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

According to the application, 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 soaking treatment are controlled, so that the amount of the oxidizing agent adsorbed by the soaking treatment is controlled, and the reaming degree can be regulated in the subsequent operation.

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

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 ℃, 150 ℃, etc., but other values within the above range are also possible, and are not limited thereto.

In some embodiments, the first drying process is for a period of 24 hours to 72 hours. Specifically, the drying time may be 24h, 30h, 36h, 40h, 50h, 60h, 70h, 72h, etc., and of course, other values within the above range are also possible, and it is understood that the temperature and time of the first drying process are controlled within the above ranges, so that the solvent in the oxidizing solution is advantageously removed as much as possible.

In some embodiments, the first drying process may be oven drying, stirred evaporation drying, spray drying, or the like.

And step S30, mixing the first precursor obtained in the step S20 with the doping agent, 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 the one hand, under the heat treatment condition, the oxidizing agent in the step S20 and the carbon on the pore wall of the pore structure of the first precursor perform oxidation reaction to realize reaming, and the reaming can convert part of micropores with small pore diameters and no energy storage activity into active energy storage micropores, so that the diffusion resistance of the electrolyte is reduced, and the capacity performance and the multiplying power performance of the active carbon material are improved.

On the other hand, after the first precursor and the doping agent are mixed under the high-temperature condition of heat treatment, the inner surface of the first precursor (the inner surface refers to the pore wall surface of the pore structure of the material) has energy storage activity after pore wall reaming, and the adsorption performance of the first precursor is higher than that of the outer surface of the material (the outer surface refers to the surface of the non-pore area of the material), so that the inner surface of the first precursor is easy to adsorb the oxidizing agent in the oxidizing solution, and the oxidizing agent reacts with carbon on the pore wall of the pore structure of the inner surface to generate carbon free radicals after the high-temperature treatment, so that doping reaction sites are provided. The first precursor has weak outer surface adsorptivity, and is less in contact with an oxidant after being dried at a high temperature, so that the doping reaction sites on the outer surface are less, and in the reaction process, the doping active sites which are absent on the outer surface of the material do not or slightly undergo oxidation reaction, so that the doping on the inner surface of the active carbon material can be selectively realized.

The active carbon material is selectively doped on the inner surface, so that the adsorption of electrolyte ions on the inner surface is facilitated, and in a full-electric state, desolvation electrolyte ions are adsorbed on the inner surface of the capacitor carbon, so that the influence of a solvent is less, and the desorption is difficult under an open circuit; the solvated electrolyte ions are adsorbed on the outer surface, and a thicker solvating layer is formed, so that the solvating electrolyte ions are easy to be interfered by solvents and are easy to be desorbed under open circuit. Therefore, the capacity performance and the self-discharge performance of the capacitor carbon can be simultaneously improved by selectively doping the inner surface. In addition, the selective doping on the inner surface can improve the wettability and conductivity of the electrolyte on 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 capacity performance. In addition, the harmful oxygen-containing functional groups on the surface of the capacitor carbon can be removed at high temperature, the self-discharge is reduced, and the self-discharge capacity retention rate is improved.

It is worth noting that the reaming process only spreads the existing holes, no new holes are made, and the phenomenon of hole collapse caused by excessive number of holes can be avoided.

In some embodiments, the dopant includes at least one of a phosphorus source, a nitrogen source, and a sulfur source, in particular, the phosphorus source includes at least one of phosphorus trichloride, phosphorus pentoxide, tri-ammonium phosphate, di-ammonium hydrogen 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 includes 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 0.05wt% to 1wt%, for example, may be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, etc., 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) - (99:1), specifically the mass ratio of the first precursor to the dopant may be 70: 30. 75: 25. 85: 15. 90: 10. 99:1, etc., of course, may be other values within the above-mentioned range, and the mass ratio of the first precursor to the dopant is controlled within the above-mentioned range, which is advantageous for adsorption of electrolyte ions on the inner surface of the activated carbon and improvement of capacity performance of the capacitor 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, but of course, other values within the above range may be also possible, and the temperature of the heat treatment is preferably 250 ℃ to 600 ℃, more preferably 300 ℃ to 500 ℃, without limitation.

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., but may be other values within the above range, and is not limited thereto.

The temperature and time of the heat treatment are controlled within the above ranges, which is favorable for oxidation reaction and doping reaction, and further improves the self-discharge capacity of the capacitor carbon material.

And S40, carrying out second impregnation treatment on the material obtained by the heat treatment obtained in the step S30 in an acid solution, and then sequentially carrying out washing, solid-liquid separation, washing, second drying treatment and screening to obtain the activated carbon material.

In the steps, the sulfuric acid-based capacitor carbon material is obtained by carrying out second impregnation treatment on the material obtained by heat treatment through acid solubility, acid molecules can occupy holes in the material obtained by heat treatment, which cannot stably adsorb electrolyte ions, so that 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, which is beneficial to 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 heat treated material to the acid solution is 1: (3-30), specifically, when the mass ratio of the material obtained by heat treatment to the acid solution may 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 is not limited thereto, and the mass ratio of the heat-treated material to the acid solution is greater than 1:30, the acid quantity is excessive, acid molecules occupy micropores capable of stably adsorbing electrolyte ions, the self-discharge capacity retention rate of the capacitor carbon is reduced, and the mass ratio of the material obtained by heat treatment to the acid solution is less than 1: and 3, too little acid solution quantity can not play a role in optimizing the capacitance carbon.

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

In some embodiments, the second dipping time is 0.1h to 48h, specifically, the second dipping time may be 0.1h, 1h, 2h, 5h, 10h, 12h, 20h, 24h, 48h, etc., but 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 wash liquor of the wash operation is deionized water, the wash cutoff condition is a pH of 1 to 4, specific pH may be 1, 1.5, 2, 2.5, 3, 3.4, 4, etc., preferably the wash cutoff condition is a pH of 1.5 to 3.0.

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

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

In some embodiments, the screening is performed using a 200 mesh or 325 mesh screen, the purpose of which is to remove large particulate foreign matter from the activated carbon material.

The embodiment of the application also provides a super capacitor, which comprises a positive plate, a negative plate, a diaphragm between the positive plate and the negative plate, and electrolyte filled in the super micropores between the positive plate and the diaphragm and between the negative plate and the diaphragm, wherein the negative plate comprises a negative current collector and a negative material distributed on the negative current collector, the positive plate comprises a positive current collector and a positive material distributed on the positive current collector, and the positive material and the negative material can be active carbon materials prepared by the method.

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 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 5mol/L.

In some embodiments, the separator of the present application is not particularly limited, and a separator well 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 method for preparing the supercapacitor is not particularly required, and the supercapacitor can be prepared by adopting a method well known in the art, and can be a symmetrical capacitor or an asymmetrical capacitor.

The following examples are provided to further illustrate embodiments of the application. The embodiments of the present application are not limited to the following specific embodiments. The modification can be appropriately performed within the scope of the main claim.

Example 1

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

(2) And 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, performing first soaking treatment for 24 hours, rinsing with deionized water until the pH is 2.5, centrifuging, and performing first drying treatment in a double-cone dryer at 80 ℃ for 48 hours to obtain a first precursor.

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

(4) Weighing a material obtained by heat treatment and 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, performing second soaking treatment for 15h, washing with deionized water until the pH is 2+/-0.5, centrifuging, performing second drying in a box-type furnace until the water content is less than 2%, uniformly mixing VC, and sieving by 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 activated carbon material having uniform particle size is obtained in the present application.

As shown in fig. 4, the XRD pattern of the activated carbon material prepared in example 1 of the present application is determined from fig. 4, and the 002 diffraction peak of the activated carbon material is regular, so that the present application provides an activated carbon material having no collapse of the microporous structure.

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 (the oxygen content is 0.05-1 w percent), crushing by a crusher with a sieve micropore aperture of 3mm to obtain crushed materials, mixing the crushed materials with sodium hydroxide according to the mass ratio of 1:1, activating for 60 minutes at 650 ℃ in a pushed slab kiln, cooling, washing with deionized water to pH of 10, washing with nitric acid and deionized water to pH of 5-7 respectively, centrifuging, drying, and jet-crushing to median particle size of 3 mu m to obtain a porous carbon material;

(2) And weighing the 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 20 ℃, uniformly stirring, performing first dipping treatment for 12h, rinsing with deionized water to pH of 2.0, centrifuging, and performing first drying treatment in a 120 ℃ oven for 24h to obtain a first precursor.

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

(4) Weighing the material obtained by heat treatment and 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, performing second soaking treatment for 24 hours, washing with deionized water until the pH is 3+/-0.5, centrifuging, performing second drying treatment in a biconical dryer until the water content is less than 3%, mixing VC uniformly, and sieving by 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 for 0.5h at 500 ℃ in a pushed slab kiln (oxygen content is 0.05-1 w%), crushing by a crusher with a 3mm screen, mixing the crushed materials and sodium oxide according to the mass ratio of 1:1.5, activating for 25min at 800 ℃ in the pushed slab kiln, cooling, washing with deionized water until the pH is 10, washing with sulfuric acid and deionized water until the pH is 5-7, filtering, drying, and mechanically crushing until the median particle diameter is 40 mu m, thereby obtaining the porous carbon material.

(2) And weighing the porous carbon material and the 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 dipping treatment for 36h, rinsing with deionized water to pH of 1.5, centrifuging, and performing first drying in a box-type furnace at 150 ℃ for 72h to obtain a first precursor.

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

(4) Weighing the material obtained by heat treatment and 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, performing second soaking treatment for 48 hours, washing with deionized water until the pH is 4.0, centrifuging, drying until the water content is less than 5%, performing second drying in an oven, uniformly mixing VC, and sieving with 325 meshes to obtain the capacitance active carbon material.

Example 4

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

(2) And 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, performing first dipping treatment for 48 hours, rinsing with deionized water to pH of 2.5, centrifuging, and performing first drying treatment in a 150 ℃ bipyramid dryer for 24 hours to obtain a first precursor.

(3) And (3) uniformly mixing the first precursor obtained in the step (S20) with urea according to the mass ratio of 70:30, putting the mixture into a box-type furnace for heat treatment, heating to 900 ℃ under the nitrogen atmosphere (the oxygen content is 0.05-1 w%), preserving 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 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, performing second soaking treatment for 5 hours, washing with deionized water until the pH is 2+/-0.5, centrifuging, performing second drying in a box-type furnace until the water content is less than 2%, uniformly mixing VC, and sieving by 325 meshes to obtain the activated carbon material.

Example 5

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

(2) And 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 the temperature of 1 ℃, uniformly stirring, performing first impregnation treatment for 0.1h, rinsing with deionized water until the pH is 2.5, centrifuging, and performing 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 the mass ratio of 90:10, putting the mixture into a box-type furnace for heat treatment, heating to 500 ℃ under the atmosphere of neon (the oxygen content is 0.05-1 w%), preserving heat for 3h, and cooling to room temperature to obtain a material obtained by heat treatment.

(4) And weighing the material obtained by heat treatment and 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, performing second soaking treatment for 0.1h, washing with deionized water until the pH is 2+/-0.5, centrifuging, performing second drying in a box-type furnace until the water content is less than 2%, uniformly mixing VC, and sieving by 325 meshes to obtain the activated carbon material.

Example 6

Unlike example 1, the carbon source in step (1) was a thermoplastic phenolic resin, and a curing agent was not added, except that the conditions were the same.

Example 7

Unlike example 1, the "melamine" in step (3) is replaced with "monoammonium phosphate".

Example 8

Unlike 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.

Performance test:

(1) SEM photographs were tested using a Hitachi Hitachi S4800 scanning electron microscope. The mass content of the doping element (N, P, S) is tested under 1000 times by combining a scanning electron microscope with an X-ray energy spectrum. And cutting the activated carbon material by using a high-energy argon ion beam to obtain a section sample. Doped element region mass ratio: at 1000 times, the ratio of the total mass content of doping elements in the cross-sectional area of the cross-sectional sample to the total mass content of doping elements in the surface area of the non-cross-sectional 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 Panalytical X' Pert PRO MPD.

(3) Nitrogen adsorption-desorption tests were performed at 77K using a microphone ratio meter tester, and the specific surface area was calculated by BET formula, and the results are shown in table 1. The micropore size distribution was calculated from the adsorption branch data using quench solid Density function theory (QSFT) and based on a slit micropore (slit-shaped pore) model.

(4) The conductivity test method comprises the following steps: an activated carbon powder is placed 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 ion was tested using ion chromatograph ICS-3000.

(6) Liquid absorption value (g/g) test method: weighing a plurality of parts of the active carbon material prepared by the method, adding 1g of 1M sulfuric acid into each part of the active carbon material, fully stirring for about 10min by using a glass rod, and when a part of the active carbon material is converted into fluidity and luster slurry, and the rest of the active carbon material still has redundant powder, and the mass value of the 1M sulfuric acid in the two critical conditions is within 0.02, making the active carbon become the lowest 1M sulfuric acid weight of the fluidity and luster slurry, namely the liquid absorption value; if fluidity, glossy slurry and partial redundant powder do not appear at the same time, the 1M sulfuric acid mass range is adjusted to retest until the fluidity, the glossy slurry and the partial redundant powder appear at the same time.

(7) By symmetryThe two-electrode system of the sulfuric acid capacitor active carbon of the application is evaluated for capacitance performance, and the process is as follows: accurately weighing active carbon, super P conductive agent and polytetrafluoroethylene adhesive, wherein the mass ratio of the active carbon to the Super P conductive agent to the polytetrafluoroethylene adhesive is about 80:15:5, adding a certain amount of isopropanol, stirring uniformly 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. Then vacuum drying the electrode plate at 120deg.C for more than 12 hr, weighing, and making the mass of active substance on the single electrode about 3+ -0.3 mg.cm ^-2 . The dried and weighed electrode sheet was pressed against a current collector (titanium mesh) and two symmetrical current collectors/electrodes were separated by two layers of microporous fibrous membrane and immersed in 1M H ₂ SO ₄ And (3) in the solution, wrapping with a paramilm sealing film, soaking for more than 5 hours, and carrying out further testing. Performed on the CHI660D electrochemical workstation.

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

constant current charge and discharge tests are carried out by adopting the current density of 0.25A/g and the multiplying power retention rate of 20A/g, and the voltage range is 0V-0.9V. Specific capacity of capacitor (C _m ) The following formula is adopted for calculation according to the constant current discharge curve:

wherein I is constant current (A), m represents total mass (g) of two electrode plates, dV/dt (V/s) is greater than V on discharge curve _max ～V _max Range/2 (V) _max For the initial discharge voltage) is fitted to the data. The current density is 0.25A/g, C _m Representing the mass specific capacity of the activated carbon.

The rate retention was a ratio of 20A/g test specific capacity to 0.25A/g test specific capacity.

Comprehensive specific capacity (C) _{Comprehensive synthesis} ) Is calculated according to the formula:

C _{comprehensive synthesis} ＝C _m /(1 + liquid absorption value)

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

(8) The self-discharge retention test method comprises the following steps: the open circuit voltage-time relationship was obtained by charging to an operating voltage of 0.9V with a constant current and holding at the constant voltage for 120min, and then opening the circuit. The self-discharge retention rate was a ratio of a voltage value of U (V) to an initial voltage of 0.9 (V) for 30 hours after the open circuit.

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

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As can be seen from table 1: the active carbon materials prepared in examples 1 to 5 are prepared by performing a first impregnation treatment on the porous carbon material at a temperature of between 1 and 45 ℃ to fill the oxidant in the oxidizing solution into the pore structure, reaming does not occur during the filling process, then the oxidant is mixed with the oxidant, and then the heat treatment is performed, wherein the purpose of reaming can be achieved in the heat treatment process, and the active carbon material can be concentrated on the pore wall surface of the pore structure of the active carbon (namely the inner surface of the active carbon material) for doping, namely, the selective doping is realized, so that the capacity performance, the multiplying power performance and the self-discharge performance of the capacitor carbon are improved simultaneously.

The doping element of example 1 has a higher mass content in the activated carbon material than that of comparative examples 1 and 2, which means that oxidation reaction in the first precursor pore structure during the heat treatment promotes the doping reaction, and the nitrogen content of comparative examples 1 and 2 is equivalent to that of comparative example 3, which means that no oxidation reaction and little doping reaction occur. Both example 1 and comparative example 1 have a pore volume below 1nm and a total pore volume higher than comparative example 2, indicating that reaming can be achieved by performing the oxidation reaction under heat treatment conditions after the first precursor adsorbs 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 active carbon material of the present application is doped mainly on the surface (inner surface) of the pore area and doped on the non-pore area (outer surface).

TABLE 2 capacitive Performance test data for examples and comparative examples

As can be seen from table 2: examples 1 to 8 have excellent comprehensive specific capacities (20.76F/g to 27.21F/g), and the self-discharge retention rate and the rate retention rate are remarkably higher than those of comparative examples 1 to 3, which shows that the activated carbon material prepared by the application has 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 the cross-sectional area doping element to the total mass content of the surface area doping element, and a doping element (nitrogen) content higher than that of example 6, since the curing agent can act as a template for the ultra-micropores, which are generated during carbonization (micropores smaller than 0.5 nm), and which are converted into active energy storage ultra-micropores during subsequent reaming. 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, thus indicating that the hole enlarging modification and doping modification effects are better in the case where the raw material of S10 contains a curing agent.

In example 1, nitrogen doping was used, and in examples 7 and 8, phosphorus doping and sulfur doping were used, respectively, and as a result, the pore volume below 1nm and the total pore volume of example 1 were larger than those of examples 7 and 8, and the mass specific capacity, the integrated specific capacity, the self-discharge retention rate and the rate retention rate were all superior to those of examples 7 and 8. The nitrogen doping effect is obviously better than that of phosphorus and sulfur doping.

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

first, doping improves the capacity performance of the activated carbon. Compared to comparative example 1, the first precursor of example 1, after adsorption of sulfuric acid, was subjected to a heat treatment reaction with a nitrogen source at high temperature, doping occurred, and the nitrogen content (2.8%) was higher than that of comparative example 1 (0.3%). On one hand, nitrogen doping contributes to pseudo capacitance and improves capacity performance; on the other hand, nitrogen doping improves the conductivity of the activated carbon, and reduces polarization; finally, nitrogen doping enhances the wettability of the electrolyte, is beneficial to the diffusion of the electrolyte into the activated carbon and is beneficial to the electrochemical process.

And secondly, the active adsorption sites of electrolyte ions are promoted by oxidizing reaming, so that the capacity performance is improved. The pore volume of 1nm or less and the total pore volume of example 1 were higher than those of comparative example 2, indicating that reaming was achieved in the oxidation reaction with the oxidizing solution, and that some of the micropores having no electrolyte adsorption activity could be converted into micropores having electrolyte adsorption activity.

The relation of the rate performance is that of example 1 > comparative example 2, which shows that the oxidation reaming can reduce the diffusion internal resistance of electrolyte ions in the activated carbon and improve the rate performance.

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

The self-discharge capacity retention ratio of example 1 was larger than that of comparative example 4, the mass specific capacity was smaller than that of comparative example 4, the liquid absorption value was lowered, and the combined specific capacity was comparable to the latter. Example 1 was acid-modified relative to comparative example 4, which demonstrates that acid molecules can occupy the micropores of the electrolyte that are unstable in adsorption, consuming unstable capacity in advance, thereby improving self-discharge performance. The overall specific capacity of example 1 is comparable to that of comparative example 4, mainly due to the drop in the liquid absorption value.

Claims

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

performing first impregnation treatment and first drying treatment on a porous carbon material in an oxidizing solution to obtain a first precursor, wherein the first impregnation treatment is performed at 1-45 ℃, and the mass ratio of the porous carbon material to the oxidizing solution is 1: (2-20), wherein the mass concentration of the oxidizing solution is 1-90 wt%, and the oxidizing solution is obtained by dispersing an oxidant in deionized water, wherein the oxidant comprises at least one of sulfuric acid, ammonium sulfate, hypochlorous acid, chloric acid, perchloric acid, hypobromous acid, bromous acid, pyrosulfuric acid and ammonium persulfate;

Mixing the first precursor and a dopant, and then performing heat treatment, wherein the dopant comprises at least one of a phosphorus source, a nitrogen source and a sulfur source, and the mass ratio of the first precursor to the dopant is (70-99): (1-30);

and carrying out second impregnation treatment and second drying treatment on the material obtained by the heat treatment in an acid solution to obtain an activated carbon material, wherein the mass ratio of the material obtained by the heat treatment to the acid solution is 1: (3-30), wherein the acid solution comprises at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, oxalic acid and phosphoric acid, and the mass concentration of the acid solution is 1-98 wt%.

2. The method according to claim 1, wherein the method further comprises:

3. The method according to claim 2, characterized in that it comprises at least one of the following features a to o:

b. The charred atmosphere comprises a first protective atmosphere;

d. the carbonized atmosphere comprises a first protective atmosphere, wherein the oxygen content of the first protective atmosphere is 0.5-wt% -1% by weight;

e. the carbonization temperature is 250-700 ℃;

f. the carbonization time is 0.5-24 hours;

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

And I, the mass ratio of the activator to the carbonized material is (0.5-3): 1, a step of;

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

and the median particle diameter of the porous carbon material is 2-40 mu m.

4. The method according to claim 1, characterized in that it comprises at least one of the following features a to c:

a. the time of the first soaking treatment is 0.1-48 h;

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

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

5. The method according to claim 1, characterized in that it comprises at least one of the following features a to e:

a. the heat treatment is performed in a second protective gas atmosphere;

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

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

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

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

6. The method according to claim 1, characterized in that it comprises at least one of the following features a to b:

a. the time of the second soaking treatment is 0.1-48 h;

b. and the moisture content of the material obtained after the second drying treatment is less than or equal to 5%.

7. An activated carbon material, which is characterized in that the activated carbon material is prepared by the preparation method of any one of claims 1-6, 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 0.40 cm ³ /g~0.80 cm ³ Per g, the volume of the pore structure with the pore diameter within 1nm is more than or equal to 0.25 and 0.25 cm ³ /g; the ratio of the total mass content of the doping elements in the cross section area of the active carbon material to the total mass content of the doping elements in the surface area of the active carbon material is more than or equal to 1.25.

8. The activated carbon material of claim 7, characterized in that it comprises at least one of the following features a to c:

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

c. the mass content of the doping element in the active carbon material is 0.01% -8%.

9. The activated carbon material of claim 7, characterized in that it comprises at least one of the following features a to j:

a. the tap density of the active carbon material is 0.55g/cm ³ ~0.75g/cm ³ ；

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

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

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

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

j. specific surface area 900 m of the activated carbon material ² /g~1300 m ² /g。

10. A supercapacitor characterized in that it comprises the activated carbon material according to any one of claims 7 to 9 or the activated carbon material prepared by the preparation method according to any one of claims 1 to 6.