CN110190258B - Silicon-carbon composite material water-based composite slurry, preparation method thereof and lithium ion battery - Google Patents
Silicon-carbon composite material water-based composite slurry, preparation method thereof and lithium ion battery Download PDFInfo
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- CN110190258B CN110190258B CN201910492163.9A CN201910492163A CN110190258B CN 110190258 B CN110190258 B CN 110190258B CN 201910492163 A CN201910492163 A CN 201910492163A CN 110190258 B CN110190258 B CN 110190258B
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- 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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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H—ELECTRICITY
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- H01M4/02—Electrodes composed of, or comprising, active material
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- H—ELECTRICITY
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- 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
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- 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
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Abstract
The invention discloses silicon-carbon composite material water-based composite slurry, a preparation method thereof and a lithium ion battery. Which comprises the following steps: dry powder stirring is carried out on the silicon-carbon composite material and SP to obtain a material A; soaking and stirring the material A, water and CMC colloid to obtain slurry with solid content of 40-45%; thirdly, stirring the slurry, the SBR emulsion and the PAA emulsion at a medium speed, defoaming and standing; and fourthly, adjusting the viscosity to 2000 to 3000 mPas. The aqueous composite binder slurry provided by the invention takes water as a solvent, is uniformly dispersed, shortens the time of secondary stirring in the preparation process, can effectively improve the distribution uniformity of the binder on a pole piece, effectively inhibits the decomposition of electrolyte in the circulation process, and forms a more uniform SEI film, so that the prepared lithium ion battery has high initial coulombic efficiency and good circulation performance.
Description
Technical Field
The invention relates to silicon-carbon composite material water-based composite slurry, a preparation method thereof and a lithium ion battery.
Background
In recent years, with the decrease of fossil energy and the increase of environmental problems, lithium ion batteries are receiving more and more attention in the fields of electric vehicles and energy storage. Lithium ion batteries are currently considered to be the most promising electrical energy storage devices due to their higher energy and power densities relative to other types of batteries. However, the energy density and power density of the existing lithium ion battery are still low, and the safety and cycle life of the existing lithium ion battery do not meet the requirements of future electric vehicles and energy storage system applications.
Graphite-based negative electrode materials have been widely used in the production of lithium ion batteries because of their high cycle efficiency and good cycle performance. However, the lithium storage capacity is low, the theoretical specific capacity is 372mAh/g, the lithium intercalation potential is close to the metallic lithium potential, and potential safety hazards still exist during high-rate charge and discharge, so that development of novel cathode materials becomes a hotspot in the research field at present, research on high-capacity cathode materials at present mainly focuses on metals which can be electrochemically alloyed with Li, such as Si, Sn, Sb, Al, Pb and the like, the reversible Li intercalation and deintercalation amount of the alloy cathodes is far greater than that of graphite, for example, the theoretical specific capacity of silicon (Si) based cathode materials is up to 4200mAh/g, and the advantages of low lithium intercalation potential, low cost and the like are generally considered as the cathode materials of next-generation lithium ion batteries.
The silicon (Si) based negative electrode material has high theoretical specific capacity (4200mAh/g) and a proper lithium intercalation/deintercalation platform, and is an ideal high-capacity negative electrode material for the lithium ion battery. However, in the charging and discharging process, i.e. in the lithium releasing and inserting process, the volume change of the silicon material is large (the volume expansion is as high as 400%), the internal stress generated by the severe volume change easily causes the silicon particles to crack and differentiate, so that the silicon particles and the conductive network are subjected to lithium releasing (electrode pulverization and peeling), the internal resistance is increased, the reversible capacity is rapidly attenuated, and the cycle performance is greatly reduced.
In lithium ion batteries, binders are one of the important factors affecting the structural stability of the electrode. The lithium ion battery binder may be classified into an oily binder using an organic solvent as a dispersant and an aqueous binder using water as a dispersant according to the properties of a dispersion medium.
CN102916190A discloses an aqueous slurry for battery electrodes, and as disclosed in paragraph 12, line 4 of the specification, PVDF can be used in water-based slurries, thus maintaining the chemical and electrochemical advantages of PVDF. As disclosed in paragraphs 13-16 of the specification, which mainly refers to the use of PVDF in aqueous binder, PVDF can be used in aqueous solvent by some improvement methods, and some advantages of the aqueous binder can be inherited, and it does not disclose the technical scheme of slurry composition as PAA + SBR + CMC. It is known from the general knowledge in the art that PVDF is not normally soluble in aqueous solvents (typically deionized water), which is used in PAA or SBR as a solvent for PVDF, which is used as a laminating agent (as disclosed in paragraph 13), whereas silicon-based materials in general (SiOx and graphite composites) generally use only aqueous solvents. And the technology of preparing the slurry by the SBR emulsion is not disclosed, and if the SBR emulsion is subjected to a demulsification phenomenon in a long stirring process, namely, the viscosity of the SBR emulsion is reduced after the stirring process is carried out for a long time, so that the SBR emulsion cannot be used as a binder well.
Disclosure of Invention
The invention provides silicon-carbon composite material aqueous composite slurry, a preparation method thereof and a lithium ion battery, and aims to overcome the defects that in the prior art, SBR emulsion has poor strength and cannot be applied to high-volume expanded Si matrix materials. The aqueous composite binder slurry provided by the invention takes water as a solvent, is uniformly dispersed, shortens the time of secondary stirring in the preparation process, can effectively improve the distribution uniformity of the binder on a pole piece, effectively inhibits the decomposition of electrolyte in the circulation process, and forms a more uniform SEI film, so that the prepared lithium ion battery has high initial coulombic efficiency and good circulation performance.
The invention solves the technical problems through the following technical scheme.
The invention provides a preparation method of silicon-carbon composite material water-based composite slurry, which comprises the following steps:
1) dry powder stirring is carried out on the silicon-carbon composite material and the conductive carbon black (SP) to obtain a material A;
2) soaking and stirring a material A, water and sodium carboxymethylcellulose colloid to obtain slurry, wherein the solid content of the slurry is 40-45%;
3) stirring the slurry, styrene butadiene rubber emulsion (SBR) and polyacrylic acid emulsion (PAA) at a medium speed, defoaming and standing;
4) the viscosity is adjusted to 2000 to 3000 mPas.
In the present invention, preferably, the raw materials of the silicon-carbon composite aqueous composite slurry comprise, in addition to water, the following components: silicon-carbon composite material, conductive carbon black, sodium carboxymethyl cellulose, styrene butadiene rubber and polyacrylic acid.
In step 1), the silicon-carbon composite material is generally in a powder form. The type of the silicon carbon composite material may be conventional in the art. At present, commercial silicon-carbon composite materials are mainly obtained by respectively compounding silicon monoxide and nano silicon with graphite. By adding 5-10% of silicon material by mass fraction, the reversible capacity of the obtained silicon-carbon composite material can reach 450-650 mA.h/g, can partially meet the application requirements in the aspects of coulomb efficiency, cycle performance, rate performance and the like, and is gradually applied to the fields of consumer electronics, electric automobiles and the like. In the invention, the capacity of the silicon-carbon composite material is generally 450-650 mAh/g.
In step 1), the conductive carbon black may be conductive carbon black conventionally commercially available in the art.
In step 1), the operation and conditions for the dry powder stirring can be conventional in the art, and are generally performed by using a planetary rotor stirrer. The revolution speed of the dry powder stirring is preferably 1800-2200 r/min, such as 2000 r/min. The time for stirring the dry powder is preferably 25 to 35min, and more preferably 30 min.
In the step 2), the sodium carboxymethyl cellulose colloid is generally a colloid formed by dissolving sodium carboxymethyl cellulose powder in water. The concentration of the sodium carboxymethylcellulose colloid can be conventional in the field, and is preferably 2-5%.
In step 2), the operation and conditions of the soaking and stirring can be conventional in the art, and are generally performed by using a planetary rotor stirrer. The revolution speed of the infiltration stirring is preferably 500-2000 r/min, such as 500r/min, 1000r/min, 1500r/min or 2000 r/min. The soaking and stirring time is preferably 10-30 min, for example 20 min.
In step 2), the water may be water conventionally used in the art, and is generally deionized water. The amount of water used is generally determined by the solids content of the slurry. As is known in the art, the solid content is (silicon carbon composite + conductive carbon black + sodium carboxymethylcellulose + binder)/(silicon carbon composite + conductive carbon black + sodium carboxymethylcellulose + binder + deionized water).
In the step 3), preferably, the styrene-butadiene rubber emulsion and the polyacrylic acid emulsion are premixed and then mixed with the slurry. The operation and conditions of the premixing may be conventional in the art.
In step 3), the styrene-butadiene rubber emulsion can be a conventional commercial product in the field. The solid content of the styrene-butadiene rubber emulsion can be conventional in the field, such as 40-60%. In one embodiment, the styrene-butadiene rubber emulsion may have a solid content of 50%.
In step 3), the polyacrylic acid emulsion may be a commercially available product that is conventional in the art. The solids content of the polyacrylic emulsion may be conventional in the art, for example 20-40%. In one embodiment, the polyacrylic acid emulsion may have a solids content of 30%.
In the step 3), if the styrene-butadiene rubber emulsion is stirred for a long time, the emulsion breaking phenomenon exists, namely, the viscosity is reduced after the stirring time is too long, and the styrene-butadiene rubber emulsion cannot be well used as a binder. Only within the above specific process range of the present invention can the SBR emulsion be ensured to play its role, and the technical problem of the present invention can be solved.
In step 3), the moderate stirring operation and conditions may be conventional in the art. The revolution speed of the medium-speed stirring is preferably 900 to 1300rpm, more preferably 1000 to 1200 rpm. The stirring time at the medium speed is preferably 3-5 min. If the stirring time is too long, the viscosity of the adhesive is reduced, the subsequent coating cannot be carried out, and the surface phenomenon of the pole piece exists.
In the invention, the mass ratio of the silicon-carbon composite material, the conductive carbon black, the sodium carboxymethyl cellulose, the styrene-butadiene rubber SBR and the polyacrylic acid PAA can be conventional in the field, and is preferably (85-93): (2-5): (2-4): (2-4): (2-4).
In the invention, when the capacity of the silicon-carbon composite material is 650mAh/g, the mass ratio of the silicon-carbon composite material, the conductive carbon black, the sodium carboxymethyl cellulose, the styrene-butadiene rubber and the polyacrylic acid is preferably 85: 5: 4: 3.
In the invention, when the capacity of the silicon-carbon composite material is 450mAh/g, the mass ratio of the silicon-carbon composite material, the conductive carbon black, the sodium carboxymethyl cellulose, the styrene-butadiene rubber and the polyacrylic acid can be 93: 2: 1.5.
In step 3), the operation and conditions for the deaeration may be conventional in the art. The revolution speed of the defoaming is generally 1000-1200r/min, and the defoaming time is generally 1-2 min.
In step 3), the operation and conditions of the standing may be conventional in the art. The standing time is generally 1-5 min, preferably 2 min.
In step 4), water is generally used to adjust the viscosity of the system, according to common knowledge in the art.
In the step 4), according to the common knowledge in the field, after the system viscosity is generally adjusted, the system is placed in vacuum, and coating is carried out after removing bubbles.
The invention also provides the silicon-carbon composite material aqueous composite slurry prepared by the preparation method.
The invention also provides a lithium ion battery, and the negative plate of the lithium ion battery is coated with the silicon-carbon composite material aqueous composite slurry.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
the preparation method of the silicon-carbon composite material water-based composite slurry is simple and convenient, the total preparation time is about 45min, the operation is convenient and controllable, and the industrial application production can be realized; the obtained slurry has good dispersibility. The slurry can effectively improve the distribution uniformity of binder particles in a pole piece, can be used for a silicon-carbon negative pole system with large volume change, effectively inhibits the volume expansion effect of an electrode material in the lithium desorption process, reduces the decomposition of electrolyte, and improves the stability of an SEI film formed in the volume expansion of the pole piece in the lithium desorption process in the circulation process; the lithium ion battery prepared from the slurry has good cycle performance and high first coulombic efficiency.
Drawings
Fig. 1 is a first charge-discharge curve of the slurry prepared in example 1 at a rate of 0.5C.
Fig. 2 is a graph showing the first charge and discharge curves of the slurry prepared in comparative example 1 at a rate of 0.5C.
Fig. 3 is a first charge and discharge curve at a rate of 0.5C for the slurry prepared in comparative example 2.
FIG. 4 is a graph showing the cycle performance test at 0.5C rate for batteries manufactured using the slurries obtained in example 1 and comparative examples 1 to 2.
Fig. 5 is a graph showing cycle performance test at 0.5C rate for batteries manufactured using the slurries of example 2 and comparative example 3.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
The raw material silicon-carbon composite materials adopted in the embodiments 1-3 and the comparative examples 1 and 2 are mainly obtained by respectively compounding the silicon monoxide and the nano silicon with graphite, and the reversible capacity of the silicon-carbon composite material can reach 650 mA.h/g by adding silicon materials with the mass fraction of 5-10%. The raw material silicon-carbon composite material can be obtained commercially.
Example 1
Preparing water-based composite slurry of the silicon-carbon composite material:
1) taking 1.7g of powdery silicon-carbon composite material (650mAh/g) and 0.1g of conductive carbon black, and stirring the powder for 30min by adopting a planetary rotor stirrer; wherein, the revolution speed is 2000 r/min;
2) adding 1.3g of deionized water and 1.6g (with the content of 5%) of sodium carboxymethylcellulose colloid into the dry powder mixed in the step (1), infiltrating and stirring in a planetary rotor stirrer for 20min to obtain uniform primary slurry, and controlling the proportion of the total solid content to be about 45%; wherein the revolution speed of the infiltration stirring is 1500 r/min;
3) continuously adding mixed emulsion of 0.12g (the content is 50%) of styrene-butadiene rubber emulsion and 0.2g (the content is 30%) of polyacrylic emulsion into the slurry after soaking and stirring, stirring at medium speed for short time, defoaming for 2min (the defoaming revolution speed is 1000-; in the process of stirring at medium speed and short time, the revolution speed is 1200r/min, and the time is 5 min;
the mass ratio of the silicon-carbon composite material to the conductive carbon black to the sodium carboxymethylcellulose to the styrene butadiene rubber SBR to the polyacrylic acid PAA is 85: 5: 4: 3: 3;
4) and adjusting the viscosity of the slurry stirred at a medium speed for a short time to 2000-3000mPa & s, standing in vacuum to remove bubbles, and coating.
Example 2
Preparing water-based composite slurry of the silicon-carbon composite material:
1) taking 3.72g of powdery silicon-carbon composite material (the capacity is 450mAh/g) and 0.08g of conductive carbon black, and stirring the powdery silicon-carbon composite material and the conductive carbon black in a planetary rotor stirrer for dry powder for 25 min; wherein, the revolution speed is 2200 r/min;
2) adding 1.6g (content: 5%) of deionized water and sodium carboxymethylcellulose colloid into the dry powder mixed in the step (1), infiltrating and stirring in a planetary rotor stirrer for 30min to obtain uniform primary slurry, and controlling the proportion of the total solid content to be about 45%; wherein, the revolution speed of infiltration stirring is 1000 r/min;
3) continuously adding mixed emulsion of 0.12g (the content is 60%) of styrene-butadiene rubber emulsion and 0.2g (the content is 30%) of polyacrylic emulsion into the slurry after soaking and stirring, stirring at medium speed for short time, defoaming for 1min (the defoaming revolution speed is 1000-; in the process of stirring at medium speed and short time, the revolution speed is 1200r/min, and the time is 5 min;
the mass ratio of the silicon-carbon composite material to the conductive carbon black to the sodium carboxymethylcellulose to the styrene butadiene rubber SBR to the polyacrylic acid PAA is 93: 2: 2: 1.5: 1.5.
4) and adjusting the viscosity of the slurry stirred at a medium speed for a short time to 2000-3000mPa & s, standing in vacuum to remove bubbles, and coating.
Comparative example 1
Preparing water-based composite slurry of the silicon-carbon composite material:
1) taking 1.7g of powdery silicon-carbon composite material (the capacity is 650mAh/g) and 0.1g of conductive carbon black, and stirring the powdery silicon-carbon composite material and the conductive carbon black in a planetary rotor stirrer for dry powder for 30 min; wherein, the revolution speed is 2000 r/min;
2) adding 1.3g of deionized water and 1.6g (with the content of 5%) of sodium carboxymethylcellulose colloid into the dry powder mixed in the step (1), infiltrating and stirring in a planetary rotor stirrer for 20min to obtain uniform primary slurry, and controlling the solid content ratio to be about 45%; wherein, the revolution speed of infiltration stirring is 1500 r/min;
3) continuously adding 0.24g (the content is 50%) of styrene-butadiene rubber emulsion into the slurry after soaking and stirring, stirring at a medium speed for a short time, defoaming for 2min (the defoaming revolution speed is 1200r/min), and standing for 2 min; in the process of stirring at medium speed and short time, the revolution is 1200r/min, and the time is 5 min;
4) and adjusting the viscosity of the slurry stirred at a medium speed for a short time to 2000-3000mPa & s, standing in vacuum to remove bubbles, and coating.
Comparative example 2
1) Taking 1.7g of powdery silicon-carbon composite material (the capacity is 650mAh/g) and 0.1g of conductive carbon black, and stirring the powdery silicon-carbon composite material and the conductive carbon black in a planetary rotor stirrer for dry powder for 30 min; wherein, the revolution speed is 2000 r/min;
2) adding 1.3g of deionized water and 1.6g (with the content of 5%) of sodium carboxymethylcellulose colloid into the dry powder mixed in the step (1), infiltrating and stirring in a planetary rotor stirrer for 20min to obtain uniform primary slurry, and controlling the solid content ratio to be about 45%; wherein, the revolution speed of infiltration stirring is 1500 r/min;
3) continuously adding 0.4g (the content is 30%) of polyacrylic emulsion into the soaked and stirred slurry, stirring at a medium speed for a short time, defoaming for 2min (the defoaming revolution speed is 1200r/min), and standing for 2 min; in the process of stirring at medium speed and short time, the revolution is 1200r/min, and the time is 5 min;
4) the viscosity of the slurry stirred at a medium speed for a short time was adjusted to 3000 mPas, and the slurry was left standing in a vacuum to remove bubbles and applied.
Comparative example 3
Preparing water-based composite slurry of the silicon-carbon composite material:
1) taking 3.72g of powdery silicon-carbon composite material (the capacity is 450mAh/g) and 0.08g of conductive carbon black, and stirring the powdery silicon-carbon composite material and the conductive carbon black in a planetary rotor stirrer for dry powder for 35 min; wherein, the revolution speed is 1800 r/min;
2) adding 1.6g (content: 5%) of deionized water and sodium carboxymethylcellulose colloid into the dry powder mixed in the step (1), infiltrating and stirring in a planetary rotor stirrer for 10min to obtain uniform primary slurry, and controlling the proportion of the total solid content to be about 45%; wherein, the revolution speed of infiltration stirring is 2000 r/min;
3) continuously adding 0.24g (the content is 50%) of styrene-butadiene rubber emulsion into the slurry after soaking and stirring, stirring at a medium speed for a short time, defoaming for 2min (the defoaming revolution speed is 1000-1200r/min), and standing for 2 min; in the process of stirring at medium speed and short time, the revolution speed is 1000r/min, and the time is 3 min;
the mass ratio of the silicon-carbon composite material to the conductive carbon black to the sodium carboxymethyl cellulose to the styrene butadiene rubber SBR is 93: 2: 2: 3.
4) and adjusting the viscosity of the slurry stirred at a medium speed for a short time to 2000-3000mPa & s, standing in vacuum to remove bubbles, and coating.
Effects of the embodiment
The electrochemical performance test process of the silicon-carbon composite material combined binder battery slurry prepared in the embodiments 1-2 and the comparative examples 1-3 is as follows:
the battery slurry prepared in example 1 was coated on a current collector copper foil. At 1.0mol/L LiPF6The electrolyte solution is/EC + DMC (volume ratio is 1:1) + VC + FEC (1%: 10%), the cathode is Li piece, the diaphragm is Cellgard-2400 type polypropylene membrane produced in America, and the CR2032 type button cell is assembled in a glove box filled with argon. Then, the prepared material was subjected to a battery cycle performance test on a CT2001A type battery test system manufactured by blue-electricity electronics gmbh of wuhan city, and the button cell was charged and discharged at a rate of 0.5C.
The battery pastes prepared in example 2 and comparative examples 1-3 were used to prepare CR2032 button cells and corresponding tests as indicated above.
Fig. 1 is a first charge-discharge curve of the slurry prepared in example 1 at a rate of 0.5C. As can be seen from FIG. 1, the first discharge capacity was 843mAh/g, the first charge capacity was 695.9mAh/g, and the first efficiency was 82.5%. The first discharge capacity of the battery performance of the battery paste prepared in example 1 was significantly improved, and the first coulombic efficiency was improved at the same time.
Fig. 2 is a graph showing the first charge and discharge curves of the slurry prepared in comparative example 1 at a 0.5C rate. As can be seen from FIG. 2, the first discharge capacity was 805mAh/g, the first charge capacity was 679.5mAh/g, and the first efficiency was 84%.
Fig. 3 is a first charge and discharge curve at a rate of 0.5C for the slurry prepared in comparative example 2. As can be seen from FIG. 3, the first discharge capacity was 827.4mAh/g, the first charge capacity was 683.2mAh/g, and the first efficiency was 82%.
FIG. 4 is a graph showing the cycle performance test at 0.5C rate for batteries manufactured using the slurries obtained in example 1 and comparative examples 1 to 2. As can be seen from fig. 4, the battery paste prepared in example 1 was effective in improving the cycle performance of the battery.
Fig. 5 is a graph showing cycle performance test at 0.5C rate for batteries manufactured using the slurries of example 2 and comparative example 3. As can be seen from fig. 5, the battery paste prepared in example 2 was effective in improving the cycle performance of the battery.
Electrochemical data of the materials obtained in examples 1-2 and comparative examples 1-3 at a rate of 0.5C are shown in Table 1.
TABLE 1
Claims (13)
1. The preparation method of the silicon-carbon composite material water-based composite slurry is characterized by comprising the following steps of:
1) dry powder stirring is carried out on the silicon-carbon composite material and the conductive carbon black to obtain a material A;
2) soaking and stirring a material A, water and sodium carboxymethylcellulose colloid to obtain slurry, wherein the solid content of the slurry is 40-45%;
3) stirring the slurry, the styrene-butadiene rubber emulsion and the polyacrylic acid emulsion at a medium speed, defoaming and standing; the revolution speed of the medium-speed stirring is 900-1300 rpm; the medium-speed stirring time is 3-5 min;
4) adjusting the viscosity to 2000-3000mPa & s;
the mass ratio of the silicon-carbon composite material, the conductive carbon black, the sodium carboxymethyl cellulose, the styrene-butadiene rubber and the polyacrylic acid is (85-93): (2-5): (2-4): (2-4): (2-4).
2. The method for preparing the silicon-carbon composite aqueous composite slurry according to claim 1, wherein the raw materials of the silicon-carbon composite aqueous composite slurry comprise the following components except water: silicon-carbon composite material, conductive carbon black, sodium carboxymethyl cellulose, styrene butadiene rubber and polyacrylic acid.
3. The method for preparing the aqueous composite slurry of silicon-carbon composite material according to claim 1, wherein the capacity of the silicon-carbon composite material is 450-650 mAh/g;
and/or in the step 1), the revolution speed of the dry powder stirring is 1800-2200 r/min; the dry powder is stirred for 25-35 min.
4. The method for preparing the silicon-carbon composite aqueous composite slurry according to claim 3, wherein in the step 1), the revolution speed of the dry powder stirring is 2000 r/min.
5. The method for preparing the silicon-carbon composite aqueous composite slurry according to claim 3, wherein in the step 1), the dry powder is stirred for 30 min.
6. The method for preparing the silicon-carbon composite aqueous composite slurry according to claim 1, wherein in the step 2), the concentration of the sodium carboxymethylcellulose colloid is 2-5%;
and/or in the step 2), the revolution speed of the infiltration stirring is 500-2000 r/min;
and/or, in the step 2), the soaking and stirring time is 10-30 min.
7. The method for preparing the aqueous composite slurry of silicon-carbon composite material according to claim 6, wherein in the step 2), the infiltration stirring revolution speed is 500r/min, 1000r/min, 1500r/min or 2000 r/min;
and/or, in the step 2), the soaking and stirring time is 20 min.
8. The method for preparing the aqueous composite slurry of silicon-carbon composite material according to claim 1, wherein in the step 3), the styrene-butadiene rubber emulsion and the polyacrylic acid emulsion are premixed and then mixed with the slurry;
and/or in the step 3), the solid content of the styrene-butadiene rubber emulsion is 40-60%;
and/or in the step 3), the solid content of the polyacrylic acid emulsion is 20-40%.
9. The method for preparing the aqueous composite slurry of silicon-carbon composite material according to claim 8, wherein in the step 3), the solid content of the styrene-butadiene rubber emulsion is 50%;
and/or in the step 3), the solid content of the polyacrylic acid emulsion is 30%.
10. The method for preparing the aqueous composite slurry of silicon-carbon composite material according to claim 1, wherein in the step 3), the revolution speed of the medium-speed stirring is 1000-1200 rpm.
11. The method for preparing the silicon-carbon composite aqueous composite slurry according to claim 1, wherein when the capacity of the silicon-carbon composite is 650mAh/g, the mass ratio of the silicon-carbon composite, the conductive carbon black, the sodium carboxymethyl cellulose, the styrene-butadiene rubber and the polyacrylic acid is 85: 5: 4: 3: 3;
when the capacity of the silicon-carbon composite material is 450mAh/g, the mass ratio of the silicon-carbon composite material, the conductive carbon black, the sodium carboxymethyl cellulose, the styrene-butadiene rubber and the polyacrylic acid is 93: 2: 2: 4: 2.
12. the silicon-carbon composite material aqueous composite slurry prepared by the preparation method of the silicon-carbon composite material aqueous composite slurry as claimed in any one of claims 1 to 11.
13. A lithium ion battery having a negative electrode sheet coated with the aqueous composite slurry of silicon-carbon composite according to claim 12.
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