CN112824320B - Electrode material, preparation method thereof and battery - Google Patents
Electrode material, preparation method thereof and battery Download PDFInfo
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- CN112824320B CN112824320B CN201911143169.1A CN201911143169A CN112824320B CN 112824320 B CN112824320 B CN 112824320B CN 201911143169 A CN201911143169 A CN 201911143169A CN 112824320 B CN112824320 B CN 112824320B
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- C—CHEMISTRY; METALLURGY
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- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
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- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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- C—CHEMISTRY; METALLURGY
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses an electrode material, a preparation method thereof and a battery, relates to the technical field of batteries, and is used for improving the cycling stability of the electrode material while keeping the electrode material to have high specific capacity. The preparation method of the electrode material comprises the following steps: mixing a carbon material, a graphene material, a binder and a silicon material together to obtain a precursor; and sintering the precursor in an inert environment to convert the carbon material contained in the precursor into the graphite carbon material with a lamellar structure, thereby obtaining the electrode material. The electrode material is prepared by the preparation method of the electrode material. The battery includes the electrode material. The electrode material, the preparation method thereof and the battery provided by the invention are used for improving the cycle performance and the specific capacity of the battery.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to an electrode material, a preparation method thereof and a battery.
Background
At present, a commercial lithium ion power battery generally uses a graphite material as a negative electrode, and the actual discharge specific capacity of the commercial lithium ion power battery is close to the theoretical value 372mAh/g, so that the technical route using the graphite material as the negative electrode material cannot meet the requirement of high energy density of the commercial lithium ion power battery, and therefore, a lot of negative electrode material production enterprises begin to adjust the strategic direction of the negative electrode material production enterprises, increase the layout of novel negative electrode materials, and the silicon-based negative electrode attracts attention.
The silicon material has high theoretical lithium intercalation specific capacity and low lithium intercalation and deintercalation potential, so that the silicon material has high theoretical lithium storage capacity which can reach 4200mAh/g generally, and therefore, the silicon material is considered as the next generation negative electrode material which is most hopeful to replace graphite. However, when the silicon material is applied to a battery electrode as an electrode material, in the process of charging and discharging, the repeated lithium ion deintercalation can cause the silicon material to generate huge volume expansion, and the volume expansion rate even reaches 300%, so that the silicon material is easy to be pulverized and crushed, and at the moment, the silicon material and a current collector lose electric contact, so that the reversible capacity of the material is sharply reduced, and the cycle performance is rapidly reduced.
Disclosure of Invention
The invention aims to provide an electrode material, a preparation method thereof and a battery, which can improve the cycling stability of the electrode material while keeping the electrode material to have high specific capacity.
In order to achieve the above object, the present invention provides a method for preparing an electrode material. The preparation method of the electrode material comprises the following steps:
mixing a carbon material, a graphene material, an adhesive and a silicon material together to obtain a precursor;
and sintering the precursor in an inert gas environment to obtain the electrode material.
Compared with the prior art, in the preparation method of the electrode material, the silicon material is distributed in the silk-like folds of the graphene material in the precursor obtained by mixing the silicon material with the graphene material, the carbon material and the binder. Meanwhile, the carbon material and the binder are attached to the graphene material, so that the carbon material contained in the precursor is converted into the graphite carbon material with a lamellar structure after the precursor is sintered. At the moment, the graphite carbon material with the lamellar structure is pasted on the surface of the graphene material, and the silk-like folds of the graphene material are shielded by the carbon material with the lamellar structure, so that the silk-like folds of the graphene material are ensured to have a large enough space. Therefore, when the electrode material provided by the invention is applied to a battery, in the process of repeated charging and discharging, the silk-like folds of the graphene material have a large enough space to provide an expansion space for the silicon material, so that the electrode material is prevented from being pulverized and broken, and the cycle stability of the electrode material is improved. In addition, when the carbon material and the graphene material are used as substrates for compounding carbon and silicon materials to prepare the electrode material, the carbon material and the graphene material have very high specific surface areas, so that the lithium storage capacity of the electrode material obtained by compounding the carbon material and the graphene material with silicon is increased, the transmission distance of lithium ions in the electrode material is shortened, and the lithiation reaction rate of silicon is increased.
The invention also provides an electrode material, which is prepared by the preparation method of the electrode material.
Compared with the prior art, the electrode material provided by the invention has the same beneficial effect as the preparation method of the electrode material.
The invention also provides a battery comprising the electrode material.
Compared with the prior art, the beneficial effects of the battery provided by the invention are the same as those of the electrode material, and are not repeated herein.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not limit the invention. In the drawings:
fig. 1 is a first flow chart of a process for preparing an electrode material according to an embodiment of the present invention;
FIG. 2 is a second flow chart of the preparation of an electrode material according to an embodiment of the present invention;
FIG. 3 is a third flow chart of the preparation of the electrode material according to the embodiment of the present invention;
FIG. 4 is a fourth flow chart of the preparation of the electrode material according to the embodiment of the present invention;
FIG. 5 is a fifth flowchart illustrating a process for preparing an electrode material according to an embodiment of the present invention;
FIG. 6 is a sixth flow chart of the preparation of the electrode material according to the embodiment of the present invention;
FIG. 7 is a seventh flow chart of the preparation of the electrode material according to the embodiment of the present invention;
FIG. 8 is a scanning electron microscope image of an electrode material prepared in example III of the present invention;
fig. 9 is a flowchart of a manufacturing method of a button cell battery according to a tenth embodiment of the present invention;
fig. 10 is a rate performance curve of button cell batteries prepared in example ten of the present invention;
fig. 11 is a cycle performance curve of a button cell prepared in accordance with example ten of the present invention;
fig. 12 is a scanning electron micrograph (sem) of an electrode material of a button cell prepared according to the tenth embodiment of the present invention, which is cycled 500 times;
fig. 13 is a scanning electron micrograph of the electrode material of the button cell prepared in the tenth embodiment of the invention, which is cycled 500 times.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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 invention.
With the rapid growth of the market of new energy automobiles, related fields such as upstream materials and the like are rapidly developed. The requirement of people on the endurance of new energy automobiles is higher and higher, and the requirement of consumers on the endurance mileage of the automobiles is continuously improved depending on the energy density of batteries, so that the high energy density becomes the future development direction of power batteries.
The silicon material has very high theoretical lithium intercalation specific capacity and lower lithium intercalation and deintercalation potential, so that the silicon material has high theoretical lithium storage capacity and is considered as the next generation negative electrode material which is most hopeful to replace graphite. However, during the charging and discharging processes of the lithium ion battery, the silicon material generates huge volume expansion due to the repeated deintercalation of lithium ions, and the volume expansion rate even reaches 300%, which easily causes the damage and mechanical pulverization of the silicon material structure. At this time, electrical contact between the silicon materials and the current collector is lost, so that the reversible capacity of the material is sharply reduced, and the cycle performance is rapidly reduced. Meanwhile, when the silicon-based material is applied to a negative electrode, silicon is continuously exposed to an electrolyte due to the volume effect of the silicon-based material in the charging and discharging processes, so that a stable solid electrolyte membrane (hereinafter referred to as SEI membrane) is difficult to form on the surface of the negative electrode, and therefore, a large amount of lithium ions contained in the electrolyte are consumed, and the first charging and discharging efficiency of the silicon-based material is reduced and the capacity of the silicon-based material is rapidly attenuated. In addition, silicon is a semiconductor material having low electrical conductivity, and the use of a silicon-based material as a negative electrode also reduces the transport rate of lithium ions.
Example one
The embodiment of the invention provides a preparation method of an electrode material, which is used for preparing the electrode material by compounding a silicon material, a carbon material and a graphene material. When the electrode material is used for an electrode of a battery, the pulverization and the crushing of a silicon material in the process of repeated charging and discharging can be avoided, and the cycling stability of the electrode material is improved. As shown in fig. 1, the preparation method of the electrode material comprises:
step S140: mixing the carbon material, the graphene material, the adhesive and the silicon material together to obtain the precursor. The binder can be selected from a wide range, such as one or more of polyvinylpyrrolidone, carboxymethyl cellulose, glucose, polyvinyl alcohol, and acrylic resin. The carbon material can be selected from one or more of graphite material, carbohydrate material, lipid material and acetylene material.
And S150, sintering the precursor in an inert environment to convert the carbon material contained in the precursor into the graphite carbon material with a lamellar structure, thereby obtaining the electrode material. The sintering temperature may be set according to actual conditions as long as the carbon-based material contained in the precursor can be converted into the graphite-based carbon material having a lamellar structure while carbonizing the binder, and is generally set to 650 to 900 ℃.
The preparation method of the electrode material provided in the above example shows that: the carbon material and the graphene material contained in the precursor have stable physical and chemical properties and excellent mechanical property, electrical property and thermal property, and in the electrode material prepared by compounding the silicon material with the carbon material and the graphene material, the carbon material and the graphene material can serve as a buffer matrix to inhibit and relieve volume change of silicon during lithium desorption, so that the volume expansion inclusion of the electrode material to the silicon material is enhanced. At this time, when the electrode material is applied to an electrode of a battery, in the process of repeated charge and discharge, shear stress and compressive stress generated by expansion when the silicon material repeatedly deintercalates lithium are absorbed by the sheet layer of the graphene-based material and the carbon-based material, so that the volume expansion of the silicon material does not cause the structural damage and mechanical pulverization of the electrode material, the structural collapse of the electrode material and the peeling of the electrode material are avoided, and the cycle performance of the electrode material is improved.
Meanwhile, the specific surface area of the graphene material is very large, which can generally reach 2630m 2 And/g, the graphene has a silk-like folded structure, so when the silicon material is compounded with the graphene material, the silicon material is coated in folds of the graphene material, and the surface of the prepared electrode material is less exposed. When the electrode material is used for an electrode of a battery, in the process of repeated charging and discharging, the graphene material serves as an isolation layer to isolate the silicon material from the electrolyte, so that the silicon material is prevented from being agglomerated, and meanwhile, the electrolyte is prevented from contacting the silicon material in the electrode material, so that the probability of expansion of the silicon material in the electrode material in the process of repeated charging and discharging is reduced, and the cycle performance of the electrode material is improved.
However, the conventional electrode material is obtained by simply physically compounding a silicon material and graphite or graphene, and since the graphene material and the graphite material are both in a layered structure, when the silicon material is mixed with one of the materials in the mixture of graphite or graphene, gaps between graphites or gaps between graphenes in the obtained electrode material are small. At this time, when the existing electrode material is used for an electrode of a battery, in the process of repeated charge and discharge, when the volume expansion of the silicon material exceeds the buffer capacity of the graphite material or the graphene material, the structure of the electrode material is damaged and mechanically pulverized, the structure of the electrode material is collapsed, the electrode material is peeled off, and the cycle performance of the motor material is reduced.
In the embodiment of the invention, the silicon material is distributed in the silk-like folds of the graphene material in the precursor obtained by mixing the silicon material with the graphene material, the carbon material and the binder, and the carbon material and the binder are attached to the graphene material, so that the carbon material contained in the precursor is converted into the graphite-like carbon material with a lamellar structure after the precursor is sintered. At the moment, the graphite carbon material with the lamellar structure is pasted on the surface of the graphene material, and the silk-like folds of the graphene material are shielded by the carbon material with the lamellar structure, so that the silk-like folds of the graphene material are ensured to have a large enough space. Therefore, when the electrode material provided by the invention is applied to a battery, in the process of repeated charging and discharging, the silk-like folds of the graphene material have enough large space to provide expansion space for the silicon material, so that the electrode material is prevented from being pulverized and broken, and the cycle stability of the electrode material is improved. In addition, when the carbon material and the graphene material are used as substrates for compounding carbon and silicon materials to prepare the electrode material, the carbon material and the graphene material have very high specific surface areas, so that the lithium storage capacity of the electrode material obtained by compounding the carbon material and the graphene material with silicon is increased, the transmission distance of lithium ions in the electrode material is shortened, and the lithiation reaction rate of silicon is increased.
As can be seen from the above, in the preparation method of the electrode material in the embodiment of the present invention, the electrode material is obtained by using the carbon-based material and the graphene-based material as the substrate, and compounding the carbon and the silicon material. When the carbon material and the graphene material are used as substrate carbon, the cycling performance of the electrode material can be improved by buffering the volume change of the silicon material and isolating the silicon material from electrolyte, and the carbon material can be converted into a graphite structure in a sintering mode, so that sufficient expansion gaps are reserved between the graphene material and the carbon material for the silicon material to improve the cycling performance of the electrode material. In addition, the carbon material and the graphene material are good conductors of electrons, and the conductivity is superior to that of a silicon material, so that the electrode material prepared by compounding the carbon material, the graphene material and the silicon material has good conductivity.
If the silicon material is mixed with the carbon material, the graphene material and the adhesive at the same time, the silicon material is distributed on the surface of the carbon material, the surface of the adhesive and the surface of the graphene material, so that the silicon material cannot be completely wrapped in silk-like folds of the graphene material. In this case, when the electrode material is used in an electrode of a battery, a portion of the silicon material is exposed to an electrolyte during repeated charge and discharge, so that it is difficult to form a stable SEI film on the surface of the electrode of the battery. Based on this, as shown in fig. 2, the mixing of the carbon-based material, the graphene-based material, and the silicon material to obtain the precursor includes:
step S141, preparing the graphene material and the silicon material into silicon-graphene material dispersion liquid. The mass ratio of the graphene-based material to the silicon material is (1.5 to 3.5): 3, and may be set according to actual needs. The graphene material and the silicon material are mixed by a wet method, and the silicon material is distributed in silk-like folds of the graphene material.
And step S142, uniformly mixing the carbon material, the binder and the silicon-graphene material dispersion liquid to obtain a precursor solution. The mass ratio of the carbon-based material to the silicon material in the precursor solution is (20-25): 3, and the mass ratio of the binder to the silicon material is (1.5-3.5): 3, which can be set according to actual needs. At this time, since the silicon material is already distributed in the silk-like wrinkles of the silicon material, the silicon material is not distributed on the surface of the carbon-based material and the surface of the adhesive.
And step S143, granulating the precursor solution to obtain a precursor. The granulation mode is more, for example, the common spray drying granulation mode can not only realize granulation, but also play a drying role.
In the above description, in the preparation method of the electrode material, the silicon material and the graphene material are mixed to obtain the silicon-graphene material dispersion liquid, and then the carbon material and the binder are mixed with the silicon-graphene material dispersion liquid, so that the silicon material is only distributed in the silk-like folds of the graphene material. At the moment, when the electrode material is applied to an electrode of a battery, the silicon material and the carbon material can form a protective layer in the process of charging and discharging for many times, so that the silicon material is prevented from being exposed in the electrolyte, a stable SEI film can be formed on the surface of the electrode material, and the cycling stability of the motor material is ensured.
Specifically, as shown in fig. 3, the step of preparing the silicon-graphene dispersion solution from the graphene-based material and the silicon material includes:
step S1411, the graphene-based material and the dispersion solvent are uniformly mixed to obtain a graphene-based material dispersion liquid. The graphene-like material and the dispersion solvent can be uniformly mixed by means of ultrasonic stirring or mechanical stirring. The selection of the dispersing solvent is various, such as: aqueous dispersion of polyvinylpyrrolidone. When the aqueous dispersion of polyvinylpyrrolidone is mixed with the graphene material to prepare the dispersion of graphene material, the mass ratio of the graphene material to the polyvinylpyrrolidone is (80-120): 1, and it is needless to say that the amount may be selected according to actual needs.
Silicon material is prepared into silicon material dispersion liquid. The particle size of the silicon material in the silicon material dispersion liquid is 150nm to 180nm, and may be set according to actual needs. When the particle diameter of the silicon material in the silicon material dispersion liquid is 150nm to 180nm, the silicon material can be dispersed in the silk-like wrinkles of the graphene-based material, and the structure of the graphene-based material is not damaged when the silicon material expands.
Step S1412, adding the silicon material dispersion to the graphene material dispersion to obtain a silicon-graphene material dispersion. The silicon material dispersion liquid and the graphene material dispersion liquid can be uniformly mixed in a stirring mode or a ball milling mode. The silicon material dispersion may be directly poured into the graphene-based material dispersion, and the silicon material dispersion may be added dropwise to the graphene-based material dispersion. When the silicon material dispersion liquid is dripped into the graphene material dispersion liquid, the amount of the graphene material is far greater than that of the silicon material, so that the silicon material can be uniformly distributed on the surface and the folds of the graphene material, the silicon material is prevented from agglomeration, and the cycle performance of the electrode material is improved.
Illustratively, in order to make the electrode material have a higher specific capacity, the tap density of the carbon-based material in the embodiment of the present invention is greater than that of the graphene-based material. At this time, the specific surface area of the graphene-based material and the carbon-based material in the prepared electrode material is large, and therefore, the electrode material has sufficient processing capacity so that the motor material has high specific capacity. Specifically, as shown in fig. 4, the carbon material, the adhesive and the silicon-graphene material dispersion are uniformly mixed to obtain a precursor solution, which includes:
step S1421, the carbon-based material is prepared into a carbon-based material dispersion. The binder is formulated into a binder dispersion.
The carbon-based material dispersion liquid can be obtained by uniformly mixing the carbon-based material with a dispersion solvent. When the carbon material is mixed with the dispersing solvent, the uniformly mixed carbon material dispersion liquid can be obtained by an ultrasonic dispersion or mechanical stirring mode. The dispersion solvent is various, such as: an aqueous dispersion of polyvinylpyrrolidone. When the aqueous dispersion of polyvinylpyrrolidone is used as the dispersion of the carbon material, the mass ratio of the carbon material to the polyvinylpyrrolidone in the dispersion of the carbon material is (80 to 120): 1. the binder dispersion can be obtained by dispersing the binder in water. The mass fraction of the binder in the binder dispersion liquid is 11-17%.
Step S1422, the carbon material dispersion, the adhesive dispersion, and the silicon-graphene material dispersion are put into a ball mill and mixed uniformly to obtain a precursor solution. The graphene dispersion solution can be firstly put into a ball mill, and then the silicon-graphene material dispersion solution is dropwise added into the graphene dispersion solution. The ball milling speed is 300rmp, and the ball milling time is 3-4 h.
Specifically, the precursor solution is granulated by spray drying, and the precursor solution is generally put into a centrifugal spray drying agent for granulation. The pressure, temperature and rotation speed of the precursor solution during granulation can be selected according to actual conditions, and the precursor solution can be prepared into a precursor, wherein the temperature of the precursor solution is 260-280 ℃, the rotation speed is 3-5 rpm/min, and the pressure is 0.3-0.5 mPa in general. It should be understood that the above rotational speed is the rotational speed of the electric high-speed centrifugal atomizer.
In some possible implementations, sintering the precursor in an inert gas environment to obtain the electrode material includes:
and sintering the precursor at 650-900 ℃ in an inert environment such as a nitrogen atmosphere or an argon atmosphere to carbonize the precursor, thereby obtaining the electrode material. Generally, the sintering time may be 90min to 150min. In addition, when sintering the precursor, the temperature should be raised to 650-900 ℃ at a rate of 2-5 ℃/min.
In some realizable modes, in order to ensure that the silicon material is uniformly distributed on the surfaces of the graphene-based material and the carbon-based material and prevent the silicon material from agglomerating due to overhigh surface energy, in the preparation method of the electrode material, the carbon-based material is a carbon-based material with negative charges, the graphene-based material is a graphene-based material with negative charges, and the silicon material is a silicon material with positive charges. At this time, the silicon nano material with positive charges can be uniformly distributed in the graphene sheet layer or the space structure of the carbon material through the charge attraction between the silicon nano material with positive charges, the graphene material with negative charges and the carbon material with negative charges. The carbon material with negative charges, the graphene material with negative charges and the silicon material with positive charges can be obtained by self-made products or purchased from manufacturers.
Specifically, the carbon-based material with negative charges is a carbon-based material with carboxyl groups on the surface, and may be a carbon-based material with other groups on the surface, as long as the carbon-based material is ensured to exhibit negative charges.
The silicon material with positive charges is nano silicon with amino groups on the surface, and certainly can also be nano silicon with other groups on the surface as long as the nano silicon can be ensured to show positive charges. For example: when the silicon material with positive charges is nano-silicon with amino on the surface, the nano-silicon with amino on the surface is in the amino of the acidic aqueous solution and H contained in the acidic aqueous solution + The combination causes the protonation of the amino group, so that the nano silicon with the amino group on the surface is positively charged in the acidic aqueous solution.
The graphene material with negative charges is provided with a plurality of sheets, and is graphene oxide and/or carboxylated graphene; at least one of the plurality of sheets of the carboxylated graphene contains a carboxyl group. The bonding of the carboxyl group contained in the carboxylated graphene to the graphene means that the graphene has a lamellar structure in which not every lamellar contains a carboxyl group. When the graphene-based material having a negative charge is carboxylated graphene, the carboxyl group of the carboxylated graphene is negatively charged in an acidic aqueous solution.
When the silicon nano material with positive charges, the graphene material with negative charges and the carbon material with negative charges are obtained in a self-made mode, the preparation method of the electrode material further comprises the following steps:
step S110, mixing the organic carboxylation reagent and the carbon material by adopting a solid phase mixing mode.
For example, as shown in fig. 5, mixing the organic carboxylation reagent with the carbon-based material by solid-phase mixing to obtain the carbon-based material with negative charges includes:
and step S111, putting the organic carboxylation reagent and the carbon material into a planetary ball mill, and mixing in a ball milling mode to perform a carboxylation reaction on the carbon material and the organic carboxylation reagent to obtain a crude product of the carboxylated carbon material. The process of the carboxylation reaction of the carbon-based material and the organic carboxylation reagent is substantially a process of combining the hydrophobic group of the carbon-based material and the hydrophobic group of the organic carboxylation reagent.
As for the mass ratio of the total mass of the organic carboxylation agent and the carbon-based material to the grinding ball, it may be set according to actual conditions, and is generally 1: (20 to 40). The ball milling time is also required to be set according to actual conditions, and is generally 1 h-3 h. As for the kind of the organic carboxylating agent, one or both of carboxymethyl cellulose and carboxyethyl cellulose may be included, though not limited thereto. Meanwhile, the ball milling mode can be dry ball milling or wet ball milling, and when the dry ball milling is selected, the energy generated in the dry ball milling process can be used for promoting the carboxylation reaction of the graphene to be carried out.
And S112, removing the coarse product of the carboxylated carbon material with poor dispersion effect from the coarse product of the carboxylated carbon material to obtain the carboxylated carbon material. For example, water can be added into the crude product of the carboxylated carbon materials, and the mixture is ultrasonically stirred for 1 to 2 hours to obtain a dispersion liquid of the crude product of the carboxylated carbon materials; and (3) carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated carbon material, collecting a filter cake, and removing water in the filter cake to obtain the carboxylated carbon material. The water in the filter cake can be removed by drying the filter cake in vacuum, the time and temperature of the vacuum drying can be selected according to the actual situation, the time of the vacuum drying is generally 20-24 h, and the drying temperature is 60-80 ℃.
Step S120, mixing the organic carboxylation reagent with graphene in a solid phase mixing manner. At the moment, the graphene material has a certain hydrophobic effect, so that the hydrophobic end of the organic carboxylation reagent is connected with the hydrophobic part of the graphene material, and the sheet layer of the graphene material has hydrophilic carboxyl, thereby obtaining the graphene material with negative charges.
Specifically, as shown in fig. 6, mixing the organic carboxylation reagent and the graphene in a solid-phase mixing manner includes:
and 121, putting the organic carboxylation reagent and the graphene material into a planetary ball mill, and mixing in a ball milling mode to perform carboxylation reaction on the graphene material and the organic carboxylation reagent to obtain a crude product of the carboxylated graphene material. The process of the carboxylation reaction of the graphene-based material and the organic carboxylation reagent is substantially a process of bonding the hydrophobic group of the graphene-based material and the hydrophobic group of the organic carboxylation reagent. As for the mass ratio of the total mass of the organic carboxylation agent and the graphene-based material to the grinding ball, it may be set according to the actual situation, and is generally 1: (20 to 40). The ball milling time is required to be set according to actual conditions, and is generally 1-3 h. As for the kind of the organic carboxylation agent, one or both of carboxymethyl cellulose and carboxyethyl cellulose may be included, although not limited thereto. Meanwhile, the ball milling mode can be dry ball milling or wet ball milling, and when the dry ball milling is selected, the energy generated in the dry ball milling process can be used for promoting the carboxylation reaction of the graphene to be carried out.
And S122, removing the coarse carboxylated graphene materials with poor dispersion effect from the coarse carboxylated graphene materials to obtain the carboxylated graphene materials. For example, water may be added to the crude carboxylated graphene-based material to obtain a dispersion of the crude carboxylated graphene-based material; ultrasonically stirring the dispersion liquid of the crude product of the carboxylated graphene material for 1 to 2 hours, and then carrying out suction filtration; collecting filter cake, and removing water in the filter cake to obtain carboxylated graphene material. The water in the filter cake can be removed by drying the filter cake in vacuum, the time and temperature of the vacuum drying can be selected according to the actual situation, the time of the vacuum drying is generally 20-24 h, and the drying temperature is 60-80 ℃.
Step S130, modifying the nano silicon by using an organic amination reagent to enable the surface of the nano silicon to have amino groups, so as to obtain a silicon material with positive charges.
Specifically, as shown in fig. 7, modifying the nano-silicon with an organic amination reagent to make the surface of the nano-silicon have amino groups, and obtaining a silicon material with positive charges includes:
step S131, refining the silicon powder to obtain the nano silicon with the particle size of 150 nm-190 nm. There are various ways to refine the silicon powder, for example, by sanding.
And step S132, mixing the nano silicon and the dispersion liquid to prepare the nano silicon dispersion liquid. The solid content of the nano silicon dispersion liquid is 18-24%, and can be selected according to actual conditions. The dispersing solvent can be selected from water and absolute ethyl alcohol.
And step S133, mixing the nano silicon dispersion liquid with absolute ethyl alcohol to obtain the nano silicon dispersion liquid. At this time, the solid content in the nano-silicon dispersion liquid is 2% to 5%, which can be selected according to actual needs.
In step S134, an alkaline substance and water are added to the nano-silicon dispersion to obtain an alkaline silicon material dispersion, wherein the alkaline substance may be ammonia water, inorganic alkali salt, or the like, but in order to avoid unnecessary pollution, the alkaline substance is generally commercially available ammonia water, and the mass concentration of the alkaline substance is 25% to 28%, and certainly ammonia water with other concentrations may be used. When the alkaline substance is commercially available ammonia water, even if certain ammonia is doped on the obtained silicon material with positive charges, the alkaline substance can be removed in the subsequent calcination process; when the alkaline substance is inorganic alkali, the obtained silicon material with positive charges is doped with certain inorganic alkali and cannot be removed in the subsequent calcining process, so that the prepared graphene-silicon composite material contains impurities, and the application of the graphene-silicon composite material in the electrode of the battery is influenced.
Step S135, an organic amination reagent is added dropwise to the alkaline silicon material dispersion liquid and stirred at room temperature, so that the silicon material contained in the alkaline silicon material dispersion liquid reacts with the organic amination reagent, and the silicon amide material dispersion liquid is obtained. Wherein, the alkaline silicon material dispersion liquid is alkaline and can promote the amination process of the silicon material; the organic amination reagent is selected from a wide range, such as one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, triethylene tetramine and ethylenediamine. The stirring time at room temperature is determined according to the actual reaction conditions.
Step S136: separating the positively charged silicon material from the silicon amide material dispersion. The separation method is more various, and for example, ethanol contained in the dispersion liquid containing the silicon material having positive charge may be removed, or the dispersion liquid containing the silicon material having positive charge may be separated by centrifugation.
In order to ensure that the charge density of the silicon material with positive charges is matched with the charge density of the graphene material with negative charges and the carbon material with negative charges, the mass ratio of the organic amination reagent to the nano silicon material is (5-10): 2, the mass ratio of the organic carboxylation reagent to the graphene material is 1 (15-45), and the mass ratio of the organic carboxylation reagent to the carbon material is 1 (15-45).
Example two
The invention also provides an electrode material, and the electrode material is prepared by the preparation method of the electrode material.
Compared with the prior art, the electrode material provided by the embodiment of the invention has the same beneficial effects as the preparation method of the electrode material, and the details are not repeated herein.
EXAMPLE III
The embodiment of the invention provides a preparation method of an electrode material, which comprises the following steps:
firstly, sanding silicon powder to obtain nano silicon with the particle size of 150-190 nm, and then uniformly mixing the nano silicon with water to obtain nano silicon dispersion liquid with the solid content of 20%; dispersing 10g of nano silicon dispersion liquid in absolute ethyl alcohol, and stirring for 1 hour to obtain silicon material dispersion liquid with the solid content of 2%; dropwise adding 4ml of ammonia water solution with the mass concentration of 25% and 8ml of water into the silicon material dispersion liquid to obtain alkaline silicon material dispersion liquid; and adding 99% of 3-aminopropyltriethoxysilane into the alkaline silicon material dispersion liquid, and stirring for 1 hour to obtain the silicon amide material dispersion liquid. Wherein the mass ratio of the 3-aminopropyltriethoxysilane to the nano-silicon in the silicon amide material dispersion liquid is 5.
Putting 10g of graphite and 0.25g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 1h to obtain a crude product of the carboxylated carbon material; and adding water into a planetary ball mill, and ultrasonically stirring for 1h to obtain a crude product dispersion liquid of the carboxylated carbon material. Wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of graphite and carboxymethyl cellulose to the mass of zirconia beads is 1; and (3) carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated carbon material, collecting a filter cake, and drying the filter cake in vacuum at the temperature of 60 ℃ for 20 hours to obtain the carboxylated carbon material. Dispersing 12g of the carboxylated carbon materials in 0.12g of the aqueous dispersion of polyvinylpyrrolidone, and ultrasonically stirring for 1 hour to obtain the carboxylated carbon materials dispersion.
Putting 10g of graphene and 0.25g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 1h to obtain a crude product of the carboxyl fossil graphene material; wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of the graphene and the mass of the carboxymethyl cellulose to the mass of the zirconia beads is 1; adding water into a planetary ball mill, and ultrasonically stirring for 1h to obtain a carboxyl fossil graphene material crude product dispersion liquid; filtering the dispersion liquid of the crude product of the carboxylated graphene material, collecting a filter cake, and drying the filter cake at the temperature of 60 ℃ in vacuum for 20 hours to obtain the carboxylated graphene material; 2g of carboxylated graphene materials are dispersed in 0.02g of aqueous dispersion of polyvinylpyrrolidone, and ultrasonic dispersion is carried out for 1 hour, so as to obtain the carboxylated graphene material dispersion.
4g of glucose was dispersed in 20ml of water to obtain a binder dispersion.
Step two, dropwise adding the silicon amide material dispersion liquid obtained in the step one into the carboxylated graphene material dispersion liquid obtained in the step 1, and mechanically stirring for 2 hours to obtain a silicon-graphene material dispersion liquid;
thirdly, adding the adhesive dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid obtained in the second step, stirring for 10min, and then adding the carboxylated carbon material dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid to obtain a mixed dispersion liquid; and adding the mixed dispersion liquid into a ball milling tank, and carrying out ball milling for 3 hours at the rotating speed of 300rmp to obtain a precursor solution.
And fourthly, spray drying the precursor solution obtained in the third step at the pressure of 0.3mp and the temperature of 260 ℃ at the rotating speed of 3rmp/min to obtain the precursor.
And fifthly, heating the precursor obtained in the fourth step to 650 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, sintering for 90min at 650 ℃, converting the carboxylated carbon materials in the precursor into graphite structures, and carbonizing the binder to obtain the electrode material.
FIG. 8 is a scanning electron microscope image of the electrode material prepared in the embodiment of the present invention. As shown in fig. 8, when silicon particles in the electrode material are uniformly deposited on graphene sheets, the regions between the graphene sheets which are not separated by the particles form a very good conductive connection structure, and do not affect the bottom-up electron transport. Meanwhile, due to the electrostatic acting force among the positively charged silicon material, the negatively charged graphene material and the negatively charged carbon material, the silicon material, the graphene material and the carbon material have tight binding force, so that the silicon particles are firmly pinned in silk-like folds of graphene, and the volume expansion of the silicon particles is prevented from being separated from the graphene layer.
Example four
The embodiment of the invention provides a preparation method of an electrode material, which comprises the following steps:
firstly, sanding silicon powder to obtain nano silicon with the particle size of 150-190 nm, and then uniformly mixing the nano silicon with water to obtain nano silicon dispersion liquid with the solid content of 18%; dispersing 10g of nano silicon dispersion liquid in absolute ethyl alcohol, and stirring for 1 hour to obtain silicon material dispersion liquid with solid content of 5%; dropwise adding 3ml of ammonia water solution with the mass concentration of 28% and 12ml of water into the silicon material dispersion liquid to obtain alkaline silicon material dispersion liquid; adding 99% of 3-aminopropyltriethoxysilane into the alkaline silicon material dispersion liquid, and stirring for 1h to obtain a silicon amide material dispersion liquid, wherein the mass ratio of the 3-aminopropyltriethoxysilane to the nano silicon in the silicon amide material dispersion liquid is 10.
Putting 10g of chitosan and 0.33g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 2 hours to obtain a crude product of the carboxylated carbon material; adding water into a planetary ball mill, and ultrasonically stirring for 2 hours to obtain a crude carboxylated carbon material dispersion liquid, wherein grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the graphite to the carboxymethyl cellulose to the zirconia beads is 1; carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated carbon material, collecting a filter cake, and drying the filter cake in vacuum at the temperature of 80 ℃ for 24 hours to obtain the carboxylated carbon material; dispersing 12g of the carboxylated carbon materials in 0.15g of aqueous dispersion of polyvinylpyrrolidone, and performing ultrasonic dispersion for 2 hours to obtain a carboxylated carbon material dispersion liquid.
Putting 10g of graphene and 0.33g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 3 hours to obtain a crude product of the carboxyl fossil graphene material; wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of the graphene and the mass of the carboxymethyl cellulose to the mass of the zirconia beads is 1; adding water into a planetary ball mill, and ultrasonically stirring for 2 hours to obtain a carboxyl fossil graphene material crude product dispersion liquid; carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated graphene material, collecting a filter cake, and drying the filter cake in vacuum at the temperature of 80 ℃ for 24 hours to obtain the carboxylated graphene material; 2g of carboxylated graphene materials are dispersed in 0.05g of aqueous dispersion of polyvinylpyrrolidone, and ultrasonic dispersion is carried out for 2 hours, so as to obtain carboxylated graphene material dispersion.
3g of polyvinylpyrrolidone was dispersed in 20ml of water to obtain a binder dispersion.
Step two, dropwise adding the silicon amide material dispersion liquid obtained in the step one into the carboxylated graphene material dispersion liquid obtained in the step 1, and mechanically stirring for 1 hour to obtain a silicon-graphene material dispersion liquid;
thirdly, adding the adhesive dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid obtained in the second step, stirring for 30min, and then adding the carboxylated carbon material dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid to obtain a mixed dispersion liquid; and adding the mixed dispersion liquid into a ball milling tank, and carrying out ball milling for 4h at the rotating speed of 300rmp to obtain a precursor solution.
And fourthly, carrying out spray drying on the precursor solution obtained in the third step at the pressure of 0.5mPa and the temperature of 280 ℃ at the rotating speed of 5rmp/min to obtain a precursor.
And fifthly, heating the precursor obtained in the fourth step to 900 ℃ at the heating rate of 2 ℃/min in the nitrogen atmosphere, sintering for 150min at the temperature of 900 ℃, converting the carboxylated carbon materials in the precursor into graphite structures, and carbonizing the binder to obtain the electrode material.
EXAMPLE five
Firstly, sanding silicon powder to obtain nano silicon with the particle size of 150-190 nm, and then uniformly mixing the nano silicon with water to obtain nano silicon dispersion liquid with the solid content of 24%; dispersing 10g of nano silicon dispersion liquid in absolute ethyl alcohol, and stirring for 1.5h to obtain silicon material dispersion liquid with solid content of 4%; dropwise adding 5ml of ammonia water solution with the mass concentration of 27% and 10ml of water into the silicon material dispersion liquid to obtain alkaline silicon material dispersion liquid; adding 99% of triethylene tetramine into the alkaline silicon material dispersion liquid, and stirring for 2 hours to obtain a silicon amide material dispersion liquid, wherein the mass ratio of the triethylene tetramine to the nano silicon in the silicon amide material dispersion liquid is 7.
Putting 10g of phospholipid and 0.67g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 3 hours to obtain a crude product of the carboxylated carbon material; adding water into a planetary ball mill, and ultrasonically stirring for 2 hours to obtain a crude carboxylated carbon material dispersion liquid, wherein grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the graphite to the carboxymethyl cellulose to the zirconia beads is 1; filtering the crude dispersion liquid of the carboxylated carbon materials, collecting a filter cake, and drying the filter cake at 70 ℃ in vacuum for 22 hours to obtain the carboxylated carbon materials; and (3) dispersing 12g of the carboxylated carbon material in 0.10g of the aqueous dispersion of the polyvinylpyrrolidone by ultrasonic dispersion for 2h to obtain the dispersion of the carboxylated carbon material.
Putting 10g of graphene and 0.67g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 2 hours to obtain a crude product of the carboxylated graphene material; wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of the graphene and the mass of the carboxymethyl cellulose to the mass of the zirconia beads is 1; adding water into a planetary ball mill, and mechanically stirring for 1.5h to obtain a carboxyl fossil graphene material crude product dispersion liquid; carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated graphene material, collecting a filter cake, and drying the filter cake at the temperature of 70 ℃ for 22 hours in vacuum to obtain the carboxylated graphene material; 2g of carboxylated graphene materials are dispersed in 0.016g of polyvinylpyrrolidone aqueous dispersion, and ultrasonic dispersion is carried out for 1.5h, so as to obtain the carboxylated graphene materials dispersion.
5g of carboxymethyl cellulose was dispersed in 20ml of water to obtain a binder dispersion.
Step two, dropwise adding the silicon amide material dispersion liquid obtained in the step one into the carboxylated graphene material dispersion liquid obtained in the step 1, and mechanically stirring for 1.5 hours to obtain a silicon-graphene material dispersion liquid;
thirdly, adding the adhesive dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid obtained in the second step, stirring for 20min, and then adding the carboxylated carbon material dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid to obtain a mixed dispersion liquid; and adding the mixed dispersion liquid into a ball milling tank, and carrying out ball milling for 3.5h at the rotating speed of 300rmp to obtain a precursor solution.
And fourthly, carrying out spray drying on the precursor solution obtained in the third step at the pressure of 0.4mPa and the temperature of 270 ℃ at the rotating speed of 4rmp/min to obtain a precursor.
And fifthly, heating the precursor obtained in the fourth step to 700 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, sintering at the temperature of 700 ℃ for 120min to convert the carbon carboxylate materials in the precursor into the graphite structure, and carbonizing the binder to obtain the electrode material.
EXAMPLE six
Firstly, sanding silicon powder to obtain nano silicon with the particle size of 150-190 nm, and then uniformly mixing the nano silicon with water to obtain nano silicon dispersion liquid with the solid content of 22%; dispersing 10g of nano silicon dispersion liquid in absolute ethyl alcohol, and stirring for 1.5 hours to obtain silicon material dispersion liquid with solid content of 3%; dropwise adding 6ml of ammonia water solution with the mass concentration of 26% and 9ml of water into the silicon material dispersion liquid to obtain alkaline silicon material dispersion liquid; adding 99% of ethylenediamine into the alkaline silicon material dispersion liquid, and stirring for 2 hours to obtain a silicon amide material dispersion liquid, wherein the mass ratio of ethylenediamine to nano silicon in the silicon amide material dispersion liquid is 8.
Putting 10g of graphdiyne and 0.22g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 2.5 hours to obtain a crude product of the carboxylated carbon material; adding water into a planetary ball mill, and ultrasonically stirring for 1.3h to obtain a crude carboxylated carbon material dispersion liquid, wherein grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the graphite to the carboxymethyl cellulose to the zirconia beads is 1; carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated carbon material, collecting a filter cake, and drying the filter cake at 65 ℃ for 21 hours in vacuum to obtain the carboxylated carbon material; dispersing 12g of the carboxylated carbon material in 0.11g of the aqueous dispersion of the polyvinylpyrrolidone, and performing ultrasonic dispersion for 1.2h to obtain the carboxylated carbon material dispersion.
Putting 10g of graphene and 0.22g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 2.5 hours to obtain a crude product of the carboxylated graphene material; wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of the graphene and the mass of the carboxymethyl cellulose to the mass of the zirconia beads is 1; adding water into a planetary ball mill, and mechanically stirring for 1.2 hours to obtain a carboxyl fossil graphene material crude product dispersion liquid; carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated graphene material, collecting a filter cake, and drying the filter cake in vacuum at the temperature of 65 ℃ for 23 hours to obtain the carboxylated graphene material; 2g of carboxylated graphene materials are dispersed in 0.018g of polyvinylpyrrolidone water dispersion liquid, and ultrasonic dispersion is carried out for 1.2h, so as to obtain the carboxylated graphene materials dispersion liquid.
6g of polyvinyl alcohol was dispersed in 20ml of water to obtain a binder dispersion.
Step two, dropwise adding the silicon amide material dispersion liquid obtained in the step one into the carboxylated graphene material dispersion liquid obtained in the step 1, and mechanically stirring for 1.8 hours to obtain a silicon-graphene material dispersion liquid;
thirdly, adding the adhesive dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid obtained in the second step, stirring for 15min, and then adding the carbon material dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid to obtain a mixed dispersion liquid; and adding the mixed dispersion liquid into a ball milling tank, and carrying out ball milling for 3.2h at the rotating speed of 300rmp to obtain a precursor solution.
And fourthly, carrying out spray drying on the precursor solution obtained in the third step at the pressure of 0.5mPa and the temperature of 260 ℃ at the rotating speed of 3rmp/min to obtain a precursor.
And fifthly, heating the precursor obtained in the fourth step to 800 ℃ at a heating rate of 4 ℃/min in a nitrogen atmosphere, sintering at the temperature of 800 ℃ for 100min to convert the carboxylated carbon materials in the precursor into a graphite structure, and carbonizing the binder to obtain the electrode material.
EXAMPLE seven
Firstly, sanding silicon powder to obtain nano silicon with the particle size of 150-190 nm, and then uniformly mixing the nano silicon with water to obtain nano silicon dispersion liquid with the solid content of 19%; dispersing 10g of nano silicon dispersion liquid in absolute ethyl alcohol, and stirring for 1.7h to obtain silicon material dispersion liquid with solid content of 5%; dropwise adding 3ml of 29% ammonia water solution and 11ml of water into the silicon material dispersion liquid to obtain alkaline silicon material dispersion liquid; adding 99% of ethylenediamine into the alkaline silicon material dispersion liquid, and stirring for 1.7h to obtain silicon amide material dispersion liquid, wherein the mass ratio of the ethylenediamine to the nano silicon in the silicon amide material dispersion liquid is 9:2.
putting 10g of graphite and 0.5g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 1.2h to obtain a crude product of the carboxylated carbon material; adding water into a planetary ball mill, and ultrasonically stirring for 1.7h to obtain a crude carboxylated carbon material dispersion liquid, wherein grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the graphite to the carboxymethyl cellulose to the zirconia beads is 1; carrying out suction filtration on the dispersion liquid of the crude product of the carboxylated carbon material, collecting a filter cake, and drying the filter cake in vacuum at the temperature of 75 ℃ for 23 hours to obtain the carboxylated carbon material; 12g of the carboxylated carbon material was dispersed in 0.13g of an aqueous dispersion of polyvinylpyrrolidone, and mechanically stirred for 1.7 hours to obtain a carboxylated carbon material dispersion.
Putting 10g of graphene, 0.5g of carboxyethyl cellulose and carboxymethyl cellulose into a planetary ball mill, wherein the sum of the mass of the carboxyethyl cellulose and the mass of the carboxymethyl cellulose is 0.24g, and performing ball milling and mixing for 2.5 hours to obtain a crude product of the carboxylated graphene material; wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of the graphene, the carboxymethyl cellulose and the carboxyethyl cellulose to the mass of the zirconia beads is 1; adding water into a planetary ball mill, and mechanically stirring for 1.7h to obtain a carboxyl fossil graphene material crude product dispersion liquid; filtering the dispersion liquid of the crude product of the carboxylated graphene material, collecting a filter cake, and drying the filter cake at 75 ℃ in vacuum for 22 hours to obtain the carboxylated graphene material; 2g of carboxylated graphene materials are dispersed in 0.022g of aqueous dispersion of polyvinylpyrrolidone, and ultrasonic dispersion is carried out for 1.7h, so as to obtain the carboxylated graphene material dispersion.
4g of an acrylic resin was dispersed in 20ml of water to obtain a binder dispersion.
Step two, dropwise adding the silicon amide material dispersion liquid obtained in the step one into the carboxylated graphene material dispersion liquid obtained in the step 1, and performing ball milling and mixing to obtain a silicon-graphene material dispersion liquid;
thirdly, adding the adhesive dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid obtained in the second step, stirring for 25min, and then adding the carbon material dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid to obtain a mixed dispersion liquid; and adding the mixed dispersion liquid into a ball milling tank, and carrying out ball milling for 3.8h at the rotating speed of 300rmp to obtain a precursor solution.
And fourthly, carrying out spray drying on the precursor solution obtained in the third step at the pressure of 0.4mPa and the temperature of 275 ℃ and at the rotating speed of 4rmp/min to obtain a precursor.
And fifthly, heating the precursor obtained in the fourth step to 850 ℃ at the heating rate of 3 ℃/min in nitrogen atmosphere, sintering for 130min at the temperature of 850 ℃ to convert the carboxylated carbon material in the precursor into a graphite structure, and carbonizing the binder to obtain the electrode material.
Comparative example 1
The embodiment of the invention provides a preparation method of an electrode material, which comprises the following steps:
firstly, sanding silicon powder to obtain nano silicon with the particle size of 150-190 nm, and then uniformly mixing the nano silicon with water to obtain nano silicon dispersion liquid with the solid content of 20%; dispersing 10g of nano silicon dispersion liquid in absolute ethyl alcohol, and stirring for 1 hour to obtain silicon material dispersion liquid with the solid content of 2%; dropwise adding 4ml of ammonia water solution with the mass concentration of 25% and 10ml of water into the silicon material dispersion liquid to obtain alkaline silicon material dispersion liquid; adding 99% of 3-aminopropyltriethoxysilane into the alkaline silicon material dispersion liquid, and stirring for 1h to obtain a silicon amide material dispersion liquid, wherein the mass ratio of the 3-aminopropyltriethoxysilane to the nano silicon in the silicon amide material dispersion liquid is 5.
And dispersing 12g of graphite in 0.12g of aqueous dispersion of polyvinylpyrrolidone, and ultrasonically stirring for 1 hour to obtain carbon material dispersion.
Putting 10g of graphene and 0.25g of carboxymethyl cellulose into a planetary ball mill, and ball-milling and mixing for 1h to obtain a crude product of the carboxyl fossil graphene material; wherein, the grinding balls in the planetary ball mill are zirconia beads, and the mass ratio of the sum of the mass of the graphene and the mass of the carboxymethyl cellulose to the mass of the zirconia beads is 1; adding water into a planetary ball mill, and ultrasonically stirring for 1h to obtain a carboxyl fossil graphene material crude product dispersion liquid; filtering the dispersion liquid of the crude product of the carboxylated graphene material, collecting a filter cake, and drying the filter cake at the temperature of 60 ℃ in vacuum for 20 hours to obtain the carboxylated graphene material; 2g of carboxylated graphene materials are dispersed in 0.02g of aqueous dispersion of polyvinylpyrrolidone, and ultrasonic dispersion is carried out for 1 hour, so as to obtain the carboxylated graphene material dispersion.
4g of glucose was dispersed in 20ml of water to obtain a binder dispersion.
Step two, dropwise adding the silicon amide material dispersion liquid obtained in the step one into the carboxylated graphene material dispersion liquid obtained in the step 1, and mechanically stirring for 2 hours to obtain a silicon-graphene material dispersion liquid;
thirdly, adding the adhesive dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid obtained in the second step, stirring for 10min, and then adding the carbon material dispersion liquid prepared in the first step into the silicon-graphene material dispersion liquid to obtain a mixed dispersion liquid; and adding the mixed dispersion liquid into a ball milling tank, and carrying out ball milling for 3 hours at the rotating speed of 300rmp to obtain a precursor solution.
And fourthly, spray drying the precursor solution obtained in the third step at the pressure of 0.3mp and the temperature of 260 ℃ at the rotating speed of 3rmp/min to obtain the precursor.
And fifthly, heating the precursor obtained in the fourth step to 650 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, sintering for 90min at the temperature of 650 ℃ to convert the carboxylated carbon material in the precursor into the graphite structure, and carbonizing the binder to obtain the electrode material.
Example nine
The battery provided by the embodiment of the invention comprises the electrode material, and the battery can be a lithium ion battery, a potassium ion battery, a sodium ion battery, an aluminum ion battery or the like, which is not listed here.
Compared with the prior art, the beneficial effects of the battery provided by the embodiment of the invention are the same as those of the electrode material, and are not repeated herein.
EXAMPLE ten
The embodiment of the invention provides a manufacturing method of a button cell, as shown in fig. 9, the manufacturing method of the button cell comprises the following steps:
step S210: preparing silicon-carbon anode slurry: and (2) dispersing the silicon-carbon composite material, the acetylene black, the styrene-butadiene rubber and the carboxymethyl cellulose mixture in N-methyl pyrrolidone according to the mass ratio of 8. The silicon-carbon composite material is the electrode material prepared in the third example and the electrode material prepared in the comparative example.
Step S220: uniformly coating the silicon-carbon negative electrode slurry on a copper foil current collector, drying under a vacuum condition, and rolling until the compacted density is 1.3g/cm 3 And obtaining the negative pole piece.
Step S230: 1mol/L LiPF with lithium metal sheet as counter electrode and polypropylene film as diaphragm 6 The solution is used as electrolyte and assembled into a button cell, liPF in a glove box in argon atmosphere 6 The solvent of the solution is 1:1 of ethylene carbonate and dimethyl carbonate. Electrochemical performance tests were performed on the button cells, and the results of the electrochemical performance tests are shown in fig. 10 and 11.
Fig. 10 shows a rate performance graph of a button cell prepared according to an example of the present invention, wherein a curve a in fig. 10 is a rate performance curve of a button cell prepared from the electrode material obtained in the third example, and a curve B is a rate performance curve of a button cell prepared from the electrode material obtained in the first comparative example. As can be seen from fig. 10: the first charge and discharge capacity of the button cell prepared from the electrode material obtained in the third example is 736mAh/g, and the first charge and discharge capacity of the button cell prepared in the first comparative example is 672mAh/g, so that the first charge and discharge capacity of the button cell prepared from the electrode material obtained in the third example is higher than that of the button cell prepared from the electrode material obtained in the first comparative example. In addition, in the process of multiple cycles of charge and discharge of the button cell, the rate capability of the button cell prepared from the electrode material obtained in the third embodiment is always greater than that of the button cell prepared from the electrode material obtained in the first embodiment. From the above, the rate performance of the button cell prepared from the electrode material obtained in example three is better.
Fig. 11 is a graph showing the cycle performance of the button cell prepared in the example of the invention, wherein the curve a in fig. 11 is the cycle performance curve of the button cell prepared from the electrode material obtained in the third example, and the curve B is the cycle performance curve of the button cell prepared from the electrode material obtained in the first comparative example. From fig. 11, it can be found that: after the circulation for 350 times, the retention rate of the button cell prepared by the electrode material obtained in the third embodiment is up to 99%, the 0.5C specific discharge capacity is maintained at 510mAh/g, while the retention rate of the button cell prepared by the electrode material obtained in the first comparative example is only 68%, and the 0.5 capacity is reduced from 550mAh/g to 37 mAh/g. From the above, the button cell prepared from the electrode material obtained in example three has better cycle performance.
Fig. 12 shows an SEM image of the electrode material containing a carboxylated carbon material, after 500 cycles of a button cell made of the electrode material containing a carboxylated carbon material. As can be seen from fig. 12, after 500 cycles, the silicon thin film in the electrode material containing the carboxylated carbon material was only roughened, but the silicon thin film did not show exfoliation. Fig. 13 shows SEM images of electrode materials containing carbon-based materials at the time of maintenance after the button cell made of electrode materials containing unmodified carbon-based materials was cycled 500 times. As can be seen from fig. 13, since there is no electrostatic attraction and support in the electrode material containing the unmodified carbon-based material, a part of the silicon particles are agglomerated, which results in severe expansion and surface roughness of the electrode material during the circulation process.
The carbon material with negative charge on the surface, the silicon material with positive charge on the surface and the graphene material with negative charge on the surface are combined through electrostatic interaction, so that the dispersion uniformity of the silicon material on the graphene sheet layer and the carbon material can be improved, the carbon material and the carbon material are mutually supported, the agglomeration phenomenon and volume expansion in the charging and discharging process when only a single component exists are relieved, the circulation stability of the material is improved, and the charging and discharging performance and the rate capability of the prepared button cell are better.
In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and shall cover the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A preparation method of an electrode material is characterized by comprising the following steps:
s140, mixing a carbon material, a graphene material, a binder and a silicon material together to obtain a precursor;
s150, sintering the precursor in an inert environment to convert the carbon material contained in the precursor into a graphite carbon material with a lamellar structure so as to obtain an electrode material;
wherein, step S140 includes:
s141, preparing the graphene material and the silicon material into silicon-graphene material dispersion liquid;
s142, uniformly mixing the carbon material, the binder and the silicon-graphene material dispersion liquid to obtain a precursor solution;
s143, granulating the precursor solution to obtain a precursor;
wherein the mass ratio of the silicon material, the graphene material, the binder and the carbon material is 3: (1.5 to 3.5): (1.5 to 3.5): (20 to 25);
the carbon material is a carbon material with negative charges, the graphene material is a graphene material with negative charges, and the silicon material is a silicon material with positive charges; the carbon material with negative charges is a carbon material with carboxyl on the surface; the graphene material with negative charges is provided with a plurality of sheets, the graphene material with negative charges is carboxylated graphene, and at least one sheet in the plurality of sheets of the carboxylated graphene contains carboxyl; the silicon material with positive charges is nano silicon with amino on the surface.
2. The method for preparing an electrode material according to claim 1, wherein the step S141 comprises:
s1411, preparing the graphene material into a graphene material dispersion liquid; preparing the silicon material into silicon material dispersion liquid;
and S1412, adding the silicon material dispersion liquid into the graphene material dispersion liquid to obtain a silicon-graphene material dispersion liquid.
3. The method for preparing an electrode material according to claim 1, wherein the step S142 comprises:
s1421, preparing a carbon material into a carbon material dispersion liquid; preparing the adhesive into an adhesive dispersion;
s1422, uniformly mixing the carbon material dispersion liquid and the adhesive dispersion liquid with the silicon-graphene material dispersion liquid in a ball milling manner to obtain a precursor solution; granulating the precursor solution to obtain a precursor;
step S1422 includes:
and (2) spray-drying the precursor solution at the temperature of 260-280 ℃ under the pressure of 0.3mPa to 0.5mPa and the rotation speed of 3-5rpm to obtain the precursor.
4. The method for preparing an electrode material according to claim 1, wherein the step S150 comprises:
and under an inert environment, heating the precursor to 650-900 ℃ at a heating rate of 2-5 ℃/min, and then preserving heat to obtain the electrode material.
5. The method for preparing the electrode material according to claim 1, wherein the tap density of the carbon-based material is greater than the tap density of the graphene-based material; and/or the presence of a gas in the gas,
the carbon material comprises one or more of graphite material, carbohydrate material, lipid material and acetylene material.
6. The method for preparing an electrode material according to any one of claims 1 to 5, wherein the method for preparing an electrode material further comprises, before step S140:
s110, mixing the organic carboxylation reagent with the carbon material in a solid-phase mixing mode to obtain the carbon material with negative charges;
s120, mixing an organic carboxylation reagent with graphene in a solid-phase mixing mode to obtain a graphene material with negative charges;
s130, modifying the nano silicon by using an organic amination reagent to enable the surface of the nano silicon to have amino groups so as to obtain the silicon material with positive charges.
7. The method for preparing an electrode material according to claim 6, wherein the step S110 comprises:
s111, mixing the organic carboxylation reagent and the carbon material in a ball milling mode to enable the carbon material and the organic carboxylation reagent to generate a carboxylation reaction to obtain a crude product of a carboxylated carbon material;
s112, removing the coarse product of the carboxylated carbon material with poor dispersion effect from the coarse product of the carboxylated carbon material to obtain the carboxylated carbon material;
and/or the presence of a gas in the gas,
step S120 includes:
s121, mixing the organic carboxylation reagent and graphene in a ball milling mode, so that the graphene and the organic carboxylation reagent are subjected to carboxylation reaction to obtain a carboxylated graphene crude product;
s122, removing graphene contained in the carboxylated graphene crude product to obtain carboxylated graphene;
and/or the presence of a gas in the gas,
the step S130 includes:
s134, adding an alkaline substance into the ethanol dispersion liquid of the nano silicon to obtain an alkaline nano silicon dispersion liquid;
s135, dropwise adding an organic amination reagent into the alkaline nano-silicon dispersion liquid and stirring at room temperature to enable nano-silicon contained in the alkaline nano-silicon dispersion liquid to react with the organic amination reagent to obtain dispersion liquid containing silicon materials with positive charges;
s136 separating the positively charged silicon material from the dispersion containing the positively charged silicon material.
8. The method for producing an electrode material according to claim 6,
the organic carboxylation reagent comprises one or two of carboxymethyl cellulose and carboxyethyl cellulose;
and/or the presence of a gas in the gas,
the organic amination reagent comprises: one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, triethylene tetramine and ethylenediamine;
and/or the presence of a gas in the gas,
the mass ratio of the organic carboxylation reagent to the carbon material is 1 (15 to 45), the mass ratio of the organic carboxylation reagent to the graphene is 1 (15 to 45), and the mass ratio of the organic carboxylation reagent to the nano silicon is (5 to 10): 2.
9. an electrode material, characterized in that the electrode material is prepared by the method for preparing the electrode material according to any one of claims 1 to 8.
10. A battery comprising the electrode material according to claim 9.
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