CN108183219B - Lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel and preparation method thereof - Google Patents
Lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
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- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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Abstract
The invention belongs to the field of lithium batteries, and provides a lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel and a preparation method thereof, wherein the cathode slurry comprises the following components in parts by weight: 95-97 parts of graphene-silicon dioxide composite aerogel powder, 0-2 parts of a conductive agent, 0-1 part of a dispersing agent, 0.5-2.5 parts of an adhesive, 0-2 parts of a thickening agent and 160 parts of water 140-. The negative electrode slurry contains the graphene-silicon dioxide composite aerogel material, the specific surface area is large, the flexibility is high, and after the graphene-silicon dioxide composite aerogel material is coated on the surface of a negative electrode piece and solidified, the surface of the obtained negative electrode piece is smooth and has weak rough feeling, so that a diaphragm can be effectively prevented from being pierced, and the service life of a battery is prolonged.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel and a preparation method thereof.
Background
With the development of new energy, lithium ion batteries have been developed in various fields. And the anode and cathode materials of the lithium ion battery play a key role in improving the performance of the lithium ion battery. For lithium ion negative electrode materials, carbon materials were used at the earliest, and then silicon, titanium, composite materials, and the like were developed. On the other hand, graphene has a single-layer two-dimensional sheet structure, a large specific surface area, excellent electrical conductivity, thermal conductivity, low resistivity and the like, and is very suitable for being used as a negative electrode material, and the negative electrode sheet of many lithium ion batteries in the prior art is already applied. The graphene or other composite materials of the graphene and other negative electrode materials are used as the negative electrode, so that the internal resistance of the battery can be obviously reduced, and the cycle performance of the battery can be improved.
Although graphene has numerous advantages, through research, the present inventors have found that graphene also has some disadvantages: although graphene has a single-layer two-dimensional sheet structure, in the actual use process, the inter-sheet distance between adjacent graphene layers is gradually reduced, so that the stripping degree of graphene is reduced, the flexibility of graphene is reduced, and the hardness of graphene is increased. When graphene is used as a negative electrode material and coated on the surface of a negative electrode current collector (usually copper foil) for curing, the surface of a negative electrode sheet becomes very rough due to hard graphene and other negative electrode particle materials, and after a lithium ion battery works for a long time, due to long-term extrusion contact and high-temperature influence of a battery diaphragm and the negative electrode sheet, the diaphragm is easily pierced by the negative electrode sheet, and micro short circuit or even diaphragm failure is easily caused.
In general, in order to improve the puncture resistance of the diaphragm in the prior art, a ceramic coating is coated on the surface of the diaphragm, but the ceramic coating causes new problems: due to the arrangement of the ceramic coating, the air permeability of the diaphragm and the wettability of electrolyte are greatly reduced, so that the performance of the battery is influenced.
Patent 201210533334.6 discloses a graphene composite lithium ion battery cathode material and a preparation method thereof, the cathode material comprises a plurality of graphene sheet layers, a hollow nanometer cathode particle layer is arranged between adjacent graphene sheet layers, the hollow nanometer cathode particles are surrounded and spaced one by the graphene sheet layers, and a gap is reserved between the adjacent graphene sheet layers; the hollow nanometer cathode particles consist of a carbon outer layer and a hollow metal cathode material inner layer. The preparation method comprises the following steps: mixing and reacting an organic precursor of silicon dioxide, a cationic surfactant, a tin salt solution and an organic carbon source; adding graphene oxide or graphene dispersion liquid for reaction and drying to obtain an intermediate product; then the primary product is obtained by treatment of the treatment liquid; and carrying out heat treatment on the primary product to obtain a product. The cathode material has the advantages of good conductivity, large electrochemical lithium storage capacity, high energy density and good cycle performance. The preparation is easy to realize industrialization and has low cost.
Although the above patent adopts graphene-loaded negative electrode particles (carbon and silicon materials), which are similar to the technical scheme of the present invention from the surface, the problem that the negative electrode material is coated with graphene only to solve the technical problem that the negative electrode material is easy to expand to cause the failure of the negative electrode material, and the technical problem that the rear surface of the negative electrode sheet made of graphene and other negative electrode materials is rough cannot be solved.
Disclosure of Invention
In order to solve the technical problems, the invention provides graphene-silicon dioxide composite aerogel-based lithium ion battery negative electrode slurry and a preparation method thereof.
The technical scheme of the invention is as follows: the graphene-silicon dioxide composite aerogel-based lithium ion battery cathode slurry comprises the following components in parts by weight:
95-97 parts of graphene-silicon dioxide composite aerogel powder,
0-2 parts of a conductive agent,
0-1 part of a dispersant, namely,
0.5 to 2.5 portions of adhesive,
0-2 parts of a thickening agent,
140 portions of water and 160 portions.
The negative electrode slurry contains the graphene-silicon dioxide composite aerogel material, the specific surface area is large, the flexibility is high, and after the graphene-silicon dioxide composite aerogel material is coated on the surface of a negative electrode piece and solidified, the surface of the obtained negative electrode piece is smooth and has weak rough feeling, so that a diaphragm can be effectively prevented from being pierced, and the service life of a battery is prolonged.
As a further preferred method, the graphene-silica composite aerogel fine particles are prepared as follows:
a) and carrying out ultrasonic washing on the graphene oxide, and drying under a negative pressure condition.
b) Adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 3-4 by using a citric acid solution, and standing and hydrolyzing for 36-72h at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:1-3:4-6: 6-8.
c) Adding ammonia water and sodium bicarbonate solution into the suspension to adjust the pH to 8-10, and heating to 60-70 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 36-72h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid to obtain the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 200-300 ℃ in a reducing atmosphere, carrying out reduction reaction for 2-4h, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
The invention utilizes a special process to prepare graphene-silicon dioxide composite aerogel powder, and specifically comprises the following steps:
in step a), the graphene oxide is subjected to ultrasonic washing before reaction, and is dried under a negative pressure condition. Wherein the ultrasonic washing has the function of releasing impurities originally adsorbed between graphene oxide sheet layers; the effect of the negative pressure is to remove air between the graphene oxide sheets by using the air pressure difference. The treatment can release the adsorption capacity of the graphene to the maximum extent, improve the adsorbability of the graphene and facilitate subsequent operation.
In the step b), the graphene oxide is added into ethyl orthosilicate to enable the ethyl orthosilicate to fully penetrate into the space between the lamellar structures of the graphene oxide. Then adding water and ethanol and adjusting the solution to be acidic so as to lead the tetraethoxysilane to generate hydrolysis reaction. In this process, since a large amount of ethyl orthosilicate is adsorbed between graphene oxide lamellar structures, a hydrolysis reaction of ethyl orthosilicate occurs between the graphene oxide lamellar structures. Hydrolysis is exothermic reaction, and is comparatively violent to generate the silica colloid between the lamellar structure, the existence of heat and silica colloid can strut graphite alkene lamellar structure, from making the stripping degree of graphite alkene improve, has bigger deformation space, and the flexibility increases. On the other hand, since silica is coated with flexible single-layer graphene, the roughness is also reduced. When the graphene-silicon dioxide composite aerogel is used as a negative electrode material and coated on the surface of a negative current collector for curing, the smoothness of the surface of a negative electrode piece can be improved, and the diaphragm is not easy to pierce. Although the technical solution of patent 201210533334.6 mentioned in the background of the present invention is similar to the technical solution of the present invention in a view of surface, it is only to coat the negative electrode material with graphene to solve the technical problem that the negative electrode material is easy to expand and the negative electrode material is ineffective, and the addition of graphene is after the hydrolysis reaction, so the amount of silica colloid directly generated in the graphene lamellar structure is small and the distance between graphene lamellar structures cannot be sufficiently expanded. The coating negative electrode material mainly depends on the physical adsorption of graphene; on the other hand, the patent 201210533334.6 does not recognize the technical problem to be solved by the present invention, and therefore, it cannot solve the technical problem that the rear surface of the negative electrode sheet made of graphene and other negative electrode materials is rough.
In addition, the mass ratio of the graphene oxide to the tetraethoxysilane is specially adjusted in the step b), and the using amount of the tetraethoxysilane is increased, so that the tetraethoxysilane is saturated and loaded between graphene oxide lamellar structures, and the lamellar spacing is increased.
In the step c), when the pH is adjusted, besides ammonia water, sodium bicarbonate is used, the effect of the sodium bicarbonate is that in the subsequent heating process, the sodium bicarbonate is decomposed to release carbon dioxide, and in the sol generation process, the porosity of the sol can be increased, so that the specific surface area of the negative electrode material is increased, and the battery performance is improved.
As a further preferred, in step a), the graphene oxide is modified by carboxylation: adding graphene oxide into toluene, uniformly dispersing, adding azodiisohexanenitrile with the mass 0.1-0.3 times that of the graphene oxide under the stirring condition, heating to 60-80 ℃ under the protection of nitrogen, stirring for reacting for 4-6h, and sequentially filtering, washing and vacuum drying; adding the product into an ethanol aqueous solution with the sodium hydroxide concentration of 20-30wt%, stirring and reacting for 24-48h at 75-85 ℃, then adjusting the pH value to 2-3, and sequentially filtering, washing and vacuum drying to obtain the carboxylated modified graphene oxide.
More preferably, in step c), after adjusting the pH to 8 to 10, aminosilane is added to the suspension in an amount of 0.5 to 1 times the mass of graphene oxide.
A silica sol prepared by a sol-gel method, which has a large number of hydroxyl groups on the surface thereof, to which silane groups on aminosilane can be bonded; meanwhile, the graphene oxide is specially subjected to carboxylation modification, and amino groups on aminosilane can react with carboxyl groups to generate amido bonds. Therefore, in the curing process of the sol, the graphene oxide and the silicon dioxide are fully bonded, the silicon dioxide is locked between the lamellar structures of the graphene oxide, and the stability of the graphene oxide is improved.
As a further preference, in step d), the drying conditions of the supercritical fluid are 5-10MPa pressure, 40-55 ℃ temperature and 6-12h time.
As a further preference, the binder is styrene butadiene rubber.
As a further preferred, the conductive agent is carbon nanotubes or Super P.
As a further preference, the dispersant is polyvinylpyrrolidone.
As a further preferred, the thickener is sodium carboxymethyl cellulose.
A preparation method of lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel comprises the following steps:
1) weighing the components according to the proportion.
2) Firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under the stirring condition, and adding the rest water after uniformly dispersing.
3) And grinding the obtained slurry to obtain the cathode slurry.
The invention has the following beneficial effects:
the negative electrode slurry contains the graphene-silicon dioxide composite aerogel material, the specific surface area is large, the flexibility is high, and after the graphene-silicon dioxide composite aerogel material is coated on the surface of a negative electrode piece and solidified, the surface of the obtained negative electrode piece is smooth and has weak rough feeling, so that a diaphragm can be effectively prevented from being pierced, and the service life of a battery is prolonged.
Detailed Description
The following is a detailed description of embodiments of the invention, but the invention can be implemented in many different ways, as defined and covered by the claims.
Example 1
The graphene-silicon dioxide composite aerogel-based lithium ion battery cathode slurry comprises the following components in parts by weight:
96 parts of graphene-silicon dioxide composite aerogel powder, 1 part of Super P, 0.5 part of polyvinylpyrrolidone, 1.5 parts of styrene butadiene rubber, 1 part of sodium carboxymethylcellulose and 150 parts of water.
A preparation method of lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel comprises the following steps:
1) weighing the components according to the proportion.
2) Firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under the stirring condition, and adding the rest water after uniformly dispersing.
3) And grinding the obtained slurry to obtain the cathode slurry.
The preparation method of the graphene-silicon dioxide composite aerogel particles comprises the following steps:
a) and carrying out ultrasonic washing on the graphene oxide, and drying under a negative pressure condition.
b) Adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 3.5 by using a citric acid solution, and standing and hydrolyzing for 50 hours at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:2:5: 7.
c) Adding ammonia water and a sodium bicarbonate solution into the suspension to adjust the pH to 9, and heating to 65 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 50h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid (the pressure is 8MPa, the temperature is 48 ℃, and the time is 9 hours) to obtain the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 250 ℃ in a reducing atmosphere, carrying out reduction reaction for 3h, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
Example 2
The graphene-silicon dioxide composite aerogel-based lithium ion battery cathode slurry comprises the following components in parts by weight:
96 parts of graphene-silicon dioxide composite aerogel powder, 1 part of carbon nano tube, 0.5 part of polyvinylpyrrolidone, 1.5 parts of styrene butadiene rubber, 1 part of sodium carboxymethylcellulose and 150 parts of water.
A preparation method of lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel comprises the following steps:
1) weighing the components according to the proportion.
2) Firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under the stirring condition, and adding the rest water after uniformly dispersing.
3) And grinding the obtained slurry to obtain the cathode slurry.
The preparation method of the graphene-silicon dioxide composite aerogel particles comprises the following steps:
carboxylation modification of graphene oxide: adding graphene oxide into toluene, uniformly dispersing, adding azodiisohexanenitrile with the mass 0.2 times that of the graphene oxide under the stirring condition, heating to 70 ℃ under the protection of nitrogen, stirring for reacting for 5 hours, and sequentially filtering, washing and vacuum drying; and adding the product into an ethanol aqueous solution with the sodium hydroxide concentration of 25 wt%, stirring and reacting for 36h at 80 ℃, then adjusting the pH value to 2.5, and sequentially filtering, washing and vacuum drying to obtain the carboxylated modified graphene oxide.
a) And carrying out ultrasonic washing on the graphene oxide, and drying under a negative pressure condition.
b) Adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 3.5 by using a citric acid solution, and standing and hydrolyzing for 50 hours at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:2:5: 7.
c) To the suspension, ammonia water and a sodium bicarbonate solution were added to adjust the pH to 9, and aminosilane (0.75 times the mass of graphene oxide) was added to the suspension. Heating to 65 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 50h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid (the pressure is 8MPa, the temperature is 48 ℃, and the time is 9 h. ) And obtaining the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 250 ℃ in a reducing atmosphere, carrying out reduction reaction for 3h, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
Example 3
The graphene-silicon dioxide composite aerogel-based lithium ion battery cathode slurry comprises the following components in parts by weight:
95 parts of graphene-silicon dioxide composite aerogel powder, 2 parts of carbon nano tubes, 1 part of polyvinylpyrrolidone, 1.5 parts of styrene butadiene rubber, 0.5 part of sodium carboxymethylcellulose and 140 parts of water.
A preparation method of lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel comprises the following steps:
1) weighing the components according to the proportion.
2) Firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under the stirring condition, and adding the rest water after uniformly dispersing.
3) And grinding the obtained slurry to obtain the cathode slurry.
The preparation method of the graphene-silicon dioxide composite aerogel particles comprises the following steps:
carboxylation modification of graphene oxide: adding graphene oxide into toluene, uniformly dispersing, adding azodiisohexanenitrile with the mass 0.1 time that of the graphene oxide under the stirring condition, heating to 60 ℃ under the protection of nitrogen, stirring for reacting for 6 hours, and sequentially filtering, washing and vacuum drying; and adding the product into an ethanol aqueous solution with the sodium hydroxide concentration of 20 wt%, stirring and reacting for 48h at 75 ℃, then adjusting the pH value to 2, and sequentially filtering, washing and vacuum drying to obtain the carboxylated modified graphene oxide.
a) And carrying out ultrasonic washing on the graphene oxide, and drying under a negative pressure condition.
b) Adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 3 by using a citric acid solution, and standing and hydrolyzing for 36 hours at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:1:4: 6.
c) To the suspension, ammonia water and a sodium bicarbonate solution were added to adjust the pH to 8, and aminosilane (0.5 times the mass of graphene oxide) was added to the suspension. Heating to 60 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 36h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid (the pressure is 5MPa, the temperature is 40 ℃, and the time is 12 h. ) And obtaining the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 200 ℃ in a reducing atmosphere, carrying out reduction reaction for 4 hours, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
Example 4
The graphene-silicon dioxide composite aerogel-based lithium ion battery cathode slurry comprises the following components in parts by weight:
96.4 parts of graphene-silicon dioxide composite aerogel powder, 0.1 part of carbon nano tube, 0.5 part of polyvinylpyrrolidone, 2.5 parts of styrene butadiene rubber, 0.5 part of sodium carboxymethylcellulose and 160 parts of water.
A preparation method of lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel comprises the following steps:
1) weighing the components according to the proportion.
2) Firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under the stirring condition, and adding the rest water after uniformly dispersing.
3) And grinding the obtained slurry to obtain the cathode slurry.
The preparation method of the graphene-silicon dioxide composite aerogel particles comprises the following steps:
carboxylation modification of graphene oxide: adding graphene oxide into toluene, uniformly dispersing, adding azodiisohexanenitrile with the mass 0.3 time that of the graphene oxide under the stirring condition, heating to 80 ℃ under the protection of nitrogen, stirring for reacting for 4 hours, and sequentially filtering, washing and vacuum drying; adding the product into an ethanol aqueous solution with the sodium hydroxide concentration of 30wt%, stirring and reacting for 24h at 85 ℃, then adjusting the pH value to 3, and sequentially filtering, washing and vacuum drying to obtain the carboxylated modified graphene oxide.
a) And carrying out ultrasonic washing on the graphene oxide, and drying under a negative pressure condition.
b) Adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 4 by using a citric acid solution, and standing and hydrolyzing for 72 hours at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:3:6: 8.
c) To the suspension, ammonia water and a sodium bicarbonate solution were added to adjust the pH to 10, and aminosilane (1 time the mass of graphene oxide) was added to the suspension. Heating to 70 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 36h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid (the pressure is 10MPa, the temperature is 55 ℃, and the time is 6 h. ) And obtaining the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 300 ℃ in a reducing atmosphere, carrying out reduction reaction for 2 hours, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
Example 5
The graphene-silicon dioxide composite aerogel-based lithium ion battery cathode slurry comprises the following components in parts by weight:
95.5 parts of Super P0.5 part of graphene-silicon dioxide composite aerogel powder, 1 part of polyvinylpyrrolidone, 2 parts of styrene butadiene rubber, 1 part of sodium carboxymethylcellulose and 150 parts of water.
A preparation method of lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel comprises the following steps:
1) weighing the components according to the proportion.
2) Firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under the stirring condition, and adding the rest water after uniformly dispersing.
3) And grinding the obtained slurry to obtain the cathode slurry.
The preparation method of the graphene-silicon dioxide composite aerogel particles comprises the following steps:
carboxylation modification of graphene oxide: adding graphene oxide into toluene, uniformly dispersing, adding azodiisohexanenitrile with the mass 0.2 times that of the graphene oxide under the stirring condition, heating to 65 ℃ under the protection of nitrogen, stirring for reacting for 5.5 hours, and sequentially filtering, washing and vacuum drying; and adding the product into an ethanol aqueous solution with the sodium hydroxide concentration of 25 wt%, stirring and reacting for 30h at 80 ℃, then adjusting the pH value to 2.6, and sequentially filtering, washing and vacuum drying to obtain the carboxylated modified graphene oxide.
a) And carrying out ultrasonic washing on the graphene oxide, and drying under a negative pressure condition.
b) Adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 3.4 by using a citric acid solution, and standing and hydrolyzing for 48 hours at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:2.5:5: 6.5.
c) To the suspension, ammonia water and a sodium bicarbonate solution were added to adjust the pH to 9.2, and aminosilane (0.6 times the mass of graphene oxide) was added to the suspension. Heating to 65 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 50h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid (the pressure is 6MPa, the temperature is 45 ℃, and the time is 8 hours) to obtain the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 280 ℃ in a reducing atmosphere, carrying out reduction reaction for 3.5h, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
Comparative example 1
The lithium ion battery cathode slurry comprises the following components in parts by weight:
56 parts of silicon dioxide, 40 parts of graphene, 1 part of Super P, 0.5 part of polyvinylpyrrolidone, 1.5 parts of styrene butadiene rubber, 1 part of sodium carboxymethylcellulose and 150 parts of water.
Comparative example 2
The lithium ion battery cathode slurry comprises the following components in parts by weight:
96 parts of graphene-silicon dioxide composite aerogel powder, 1 part of Super P, 0.5 part of polyvinylpyrrolidone, 1.5 parts of styrene butadiene rubber, 1 part of sodium carboxymethylcellulose and 150 parts of water.
The preparation method of the graphene-silicon dioxide composite aerogel particles comprises the following steps:
a) uniformly mixing ethyl orthosilicate, water and ethanol to prepare a solution, adjusting the pH value to 3.4 by using a citric acid solution, and standing and hydrolyzing for 48 hours at room temperature; wherein the mass ratio of the ethyl orthosilicate to the water to the ethanol is 2.5:5: 6.5.
b) Adding graphene into the hydrolysate, and uniformly dispersing, wherein the mass ratio of the graphene oxide to the ethyl orthosilicate is 1: 2.5.
c) Adding ammonia water into the suspension to adjust the pH to 9.2 to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 50h, and washing off impurities to obtain the graphene oxide-silicon dioxide composite gel.
d) And (3) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid (the pressure is 6MPa, the temperature is 45 ℃, and the time is 8 hours) to obtain the graphene oxide-silicon dioxide composite aerogel.
e) And (3) heating the graphene oxide-silicon dioxide composite aerogel to 280 ℃ in a reducing atmosphere, carrying out reduction reaction for 3.5h, and grinding to obtain graphene-silicon dioxide composite aerogel powder.
The physical mixed material of silicon dioxide and graphene is directly adopted in the comparative example 1, and graphene is added after hydrolysis reaction in the preparation process of the graphene-silicon dioxide composite aerogel powder in the comparative example 2.
The negative electrode slurry prepared in the examples 1-2 and the comparative examples 1-2 of the invention was coated on the surface of a negative electrode copper foil under the same conditions to prepare a negative electrode sheet, and sensory evaluation was performed on the surface of the negative electrode sheet.
| Group number | Average thickness of coating | Sense of the surface of the coating |
| Example 1 | 24.5μm | Smooth hand feeling and weak rough feeling |
| Example 2 | 24.6μm | Smooth hand feeling and weak rough feeling |
| Comparative example 1 | 24.7μm | Rough hand feeling and fine and sharp spines |
| Comparative example 2 | 24.3μm | Rough hand feeling and fine and sharp spines |
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. The lithium ion battery cathode slurry based on the graphene-silicon dioxide composite aerogel is characterized by comprising the following components in parts by weight:
95-97 parts of graphene-silicon dioxide composite aerogel powder,
0-2 parts of a conductive agent,
0-1 part of a dispersant, namely,
0.5 to 2.5 portions of adhesive,
0-2 parts of a thickening agent,
140 portions of water and 160 portions of water;
the preparation method of the graphene-silicon dioxide composite aerogel powder comprises the following steps:
a) carrying out ultrasonic washing on graphene oxide, and drying under a negative pressure condition;
b) adding graphene oxide into ethyl orthosilicate, fully stirring, then adding water and ethanol, uniformly mixing to prepare a suspension, adjusting the pH value to 3-4 by using a citric acid solution, and standing and hydrolyzing for 36-72h at room temperature; wherein the mass ratio of the graphene oxide to the ethyl orthosilicate to the water to the ethanol is 1:1-3:4-6: 6-8;
c) adding ammonia water and sodium bicarbonate solution into the suspension to adjust the pH to 8-10, adding aminosilane into the suspension, wherein the addition amount of aminosilane is 0.5-1 times of the mass of graphene oxide, and heating to 60-70 ℃ to obtain graphene oxide-silicon dioxide composite sol; standing and curing for 36-72h, and washing off impurities to obtain graphene oxide-silicon dioxide composite gel;
d) fully replacing water and ethanol in the graphene oxide-silicon dioxide composite gel with n-hexane, taking out the gel, and drying with a carbon dioxide supercritical fluid to obtain the graphene oxide-silicon dioxide composite aerogel;
e) heating the graphene oxide-silicon dioxide composite aerogel to 200-300 ℃ in a reducing atmosphere, carrying out reduction reaction for 2-4h, and grinding to obtain graphene-silicon dioxide composite aerogel powder;
in the step a), the graphene oxide is modified by carboxylation: adding graphene oxide into toluene, uniformly dispersing, adding azodiisohexanenitrile with the mass 0.1-0.3 times that of the graphene oxide under the stirring condition, heating to 60-80 ℃ under the protection of nitrogen, stirring for reacting for 4-6h, and sequentially filtering, washing and vacuum drying; adding the product into an ethanol aqueous solution with the sodium hydroxide concentration of 20-30wt%, stirring and reacting for 24-48h at 75-85 ℃, then adjusting the pH value to 2-3, and sequentially filtering, washing and vacuum drying to obtain the carboxylated modified graphene oxide.
2. The graphene-silica composite aerogel-based lithium ion battery negative electrode slurry as claimed in claim 1, wherein in the step d), the drying condition of the supercritical fluid is 5-10MPa, 40-55 ℃ and 6-12 h.
3. The graphene-silica composite aerogel-based lithium ion battery negative electrode slurry as claimed in claim 1, wherein the binder is styrene butadiene rubber.
4. The graphene-silica composite aerogel-based lithium ion battery negative electrode slurry as claimed in claim 1, wherein the conductive agent is carbon nanotubes or Super P.
5. The graphene-silica composite aerogel-based lithium ion battery negative electrode slurry as claimed in claim 1, wherein the dispersant is polyvinylpyrrolidone.
6. The graphene-silicon dioxide composite aerogel-based lithium ion battery negative electrode slurry as claimed in claim 1, wherein the thickener is sodium carboxymethylcellulose.
7. The preparation method of the graphene-silica composite aerogel based lithium ion battery anode slurry according to any one of claims 1 to 6, characterized by comprising the following steps:
1) weighing the components according to the proportion;
2) firstly, adding a thickening agent into water with a half formula amount, then sequentially adding an adhesive, a dispersing agent, a conductive agent and graphene-silicon dioxide composite aerogel powder under a stirring condition, and adding the rest water after uniformly dispersing;
3) and grinding the obtained slurry to obtain the cathode slurry.
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| CN110422850A (en) * | 2019-06-25 | 2019-11-08 | 华南理工大学 | High-specific surface area strong-hydrophobicity graphene oxide/silicon dioxide composite aerogel atmospheric preparation method |
| CN113013385A (en) * | 2019-12-19 | 2021-06-22 | 山西沃特海默新材料科技股份有限公司 | Coating agent, silicon-carbon material and preparation process |
| CN111769281A (en) * | 2020-06-18 | 2020-10-13 | 合肥国轩高科动力能源有限公司 | Lithium ion battery conductive agent and lithium ion battery |
| CN111682206B (en) * | 2020-07-07 | 2021-11-05 | 江苏日御光伏新材料科技有限公司 | Lithium ion battery cathode slurry based on graphene-silicon dioxide composite aerogel and preparation method thereof |
| CN115282890B (en) * | 2022-08-01 | 2023-11-17 | 东莞澳中新材料科技股份有限公司 | Preparation method of silicon-graphene reinforced composite aerogel and preparation method of electrode |
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