CN110350196B - Composite binder, silicon-based negative plate and preparation method thereof - Google Patents
Composite binder, silicon-based negative plate and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/0402—Methods of deposition of the material
- H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
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- 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
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- H—ELECTRICITY
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- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a composite binder, a silicon-based negative plate and a preparation method thereof. The preparation method of the silicon-based negative plate comprises the following steps: mixing polyvinylidene fluoride with different molecular weights by a ball mill to obtain a composite binder; dissolving the composite binder in an organic solvent to obtain a binder glue solution; dispersing a conductive agent in a binder glue solution to obtain a conductive glue solution; adding silicon-carbon composite material powder and an organic solvent into the conductive glue solution to prepare electrode slurry; coating the electrode slurry on a negative current collector, and carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry; and rolling the obtained negative pole piece to obtain the silicon-based negative pole piece. The prepared silicon-based negative plate can effectively improve the performance of the lithium battery electrode material, and improve the rate capability and cycle life of the battery.
Description
Technical Field
The invention relates to a high-performance composite binder, a silicon-based negative plate based on the binder and a preparation method of the silicon-based negative plate, and belongs to the technical field of energy storage batteries.
Background
The lithium ion battery has high energy density, high working voltage, no memory effect and long cycle life, and is widely applied to intelligent wearable equipmentAnd new energy vehicles and the like. However, since the application conditions of the lithium ion battery are complex, people have higher requirements on the aspects of energy density, cycle life, safety performance and the like. Research and development of high-energy-density silicon negative electrode (theoretical specific capacity 4200mAh g)-1) To replace the prior graphite cathode (with the theoretical specific capacity of 372mAh & g)-1) Is an important way for improving the performance of the lithium ion battery. However, during charging and discharging, the silicon material changes in volume greatly (much higher than graphite), causing self-pulverization, causing the active material to fall off from the current collector, resulting in poor cycle stability of the battery. The adoption of the adhesive for inhibiting the electrode expansion is an important method for solving the problem of silicon volume expansion. The adhesive can tightly bond the silicon-carbon composite material, the conductive agent and the current collector together, thereby stabilizing the electrode structure and solving the problem of silicon volume expansion.
Currently used lithium ion battery binders include styrene-butadiene rubber (SBR), multipolymers of acrylonitrile (LA-series polymers), and polyvinylidene fluoride (PVDF) types. The poor affinity of SBR and polar electrolyte leads to difficult lithium ion conduction in a binder in the charging and discharging process, increases the internal resistance of the battery, and is difficult to meet the requirement of a lithium battery, particularly a power battery, on high-rate charging and discharging. The LA series polymer has too high glass transition temperature, and the pole piece is easy to harden and become brittle, so that the processing performance is poor. For example, the coating is easy to crack during coating and generate stripes after rolling, which restrict the application of the coating in lithium batteries, especially power batteries. Although the traditional PVDF (with the molecular weight of about 100 ten thousand) has better electrochemical stability and excellent flexibility, the PVDF is easy to swell when being acted with propylene carbonate in an electrolyte, so that the electrode structure is deformed, and meanwhile, the binding force is reduced, so that the cycle performance of a battery is deteriorated, and the application of the PVDF in inhibiting the expansion of a silicon-based negative electrode is limited.
Disclosure of Invention
The invention aims to provide a high-performance composite binder, a silicon-based negative plate based on the binder and a preparation method of the silicon-based negative plate.
In order to achieve the above object, the present invention provides a method for preparing a silicon-based negative electrode plate, which is characterized by comprising the following steps:
step 1: mixing 10-80 wt% of polyvinylidene fluoride with the weight-average molecular weight of 150-300 ten thousand, 10-70 wt% of polyvinylidene fluoride with the weight-average molecular weight of 80-140 ten thousand and 0-60 wt% of polyvinylidene fluoride with the weight-average molecular weight of 20-60 ten thousand by a ball mill to obtain a composite binder;
step 2: dissolving the composite binder obtained in the step 1 in an organic solvent to obtain a binder glue solution;
and step 3: dispersing a conductive agent in the adhesive liquid obtained in the step 2 to obtain a conductive liquid adhesive;
and 4, step 4: adding silicon-carbon composite material powder and an organic solvent into the conductive glue solution obtained in the step 3 to prepare electrode slurry;
and 5: coating the electrode slurry obtained in the step (4) on a negative current collector through an automatic coating machine to obtain the current collector coated with the electrode slurry;
step 6: carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry;
and 7: and rolling the obtained negative pole piece to obtain the silicon-based negative pole piece.
Preferably, the silicon-carbon composite material is a mixture of silicon-based and carbon-based materials. More preferably, the carbon-based material is one or more of hard carbon, soft carbon, natural graphite and artificial graphite. More preferably, the silicon-based material is one or more of micro silicon, nano silicon, silicon monoxide and silicon oxide.
Preferably, the conductive agent is one of acetylene black, ketjen black, carbon fiber, and Super P.
Preferably, the organic solvent is one of N-methylpyrrolidone, acetonitrile and dimethylformamide.
Preferably, the mass fraction of the adhesive glue solution is 5-50%. More preferably, the mass fraction of the adhesive glue solution is 5-10%.
Preferably, the specific step of "dissolving the composite binder obtained in step 1 in an organic solvent" in step 2 comprises: bonding the composite obtained in the step 1Adding the agent into an organic solvent at 10-60 deg.C for 100--1Stirring for 10-72h at the rotating speed to prepare the adhesive liquid. More preferably, the specific step of "dissolving the composite binder obtained in step 1 in an organic solvent" in step 2 comprises: adding the composite binder obtained in the step 1 into an organic solvent at the temperature of 15-45 ℃ at the temperature of 100-2500 r.min-1Stirring for 10-72h at the rotating speed to prepare the adhesive liquid.
Preferably, the mass fraction of the conductive agent in the conductive glue solution is 5-20%.
Preferably, the specific step of "dispersing the conductive agent in the binder glue solution obtained in step 2" includes: adding conductive agent into the adhesive liquid, at the temperature of 10-60 ℃ and at the temperature of 100--1Stirring for 5-300min at the rotating speed of (1).
Preferably, the viscosity of the electrode slurry is 500-25000 mPas.
Preferably, the specific preparation step of the electrode slurry in step 4 comprises: adding the silicon-carbon composite material powder into the conductive glue solution, and performing heat treatment at 10-60 ℃ for 1000 r.min at 100--1Stirring for 5-100min at the rotating speed of (1), adding an organic solvent at the speed of 100-1500 r.min-1Stirring at a rotating speed for 10-500min to obtain the electrode slurry.
Preferably, the coating process in step 5 comprises: coating the electrode slurry on a negative current collector at a thickness of 10-300 μm at a temperature of 15-60 deg.C with an automatic coating machine at a coating speed of 1-8m min-1The water content of the slurry at the time of coating is 100ppm or less.
Preferably, the specific steps of the vacuum high-temperature desolventizing treatment comprise: and (3) placing the current collector coated with the electrode slurry in an oven at the temperature of 80-130 ℃, wherein the relative vacuum degree value is less than or equal to-0.1 MPa, and the treatment time is 10-25 h.
Preferably, after the rolling, the thickness of the negative pole piece is 10-100 μm.
The invention also provides a composite binder which is characterized by comprising 10-80 wt% of polyvinylidene fluoride with the weight-average molecular weight of 150-300 ten thousand, 10-70 wt% of polyvinylidene fluoride with the weight-average molecular weight of 80-140 ten thousand and 0-60 wt% of polyvinylidene fluoride with the weight-average molecular weight of 20-60 ten thousand.
Preferably, the high-performance composite binder consists of 10-80 wt% of polyvinylidene fluoride with the weight-average molecular weight of 22000000, 10-70 wt% of polyvinylidene fluoride with the weight-average molecular weight of 10500000, and 10-60 wt% of polyvinylidene fluoride with the weight-average molecular weight of 5700000.
The invention also provides a preparation method of the high-performance composite binder, which is characterized by comprising the following steps: mixing 10-80 wt% of polyvinylidene fluoride with the weight-average molecular weight of 150-300 ten thousand, 10-70 wt% of polyvinylidene fluoride with the weight-average molecular weight of 80-140 ten thousand and 0-60 wt% of polyvinylidene fluoride with the weight-average molecular weight of 20-60 ten thousand by a ball mill to obtain the high-performance composite binder.
The invention firstly prepares a high-performance composite binder (the molecular weight is about 200 ten thousand), solves the problem that the processability and the structural stability of the polyvinylidene fluoride with single molecular weight are difficult to jointly optimize, and then provides a preparation method of a silicon-based negative plate based on the binder. The carbon-silicon cathode for the lithium ion battery prepared by the high-performance composite binder can solve the technical problems of poor multiplying power performance and short cycle life of a silicon material battery in the prior art. The prepared silicon-based negative plate effectively improves the performance of the lithium battery electrode material, improves the rate capability and prolongs the cycle life of the battery.
Compared with the prior art, the invention has the following technical effects:
1. the preparation method of the composite binder is simple, the high-performance silicon-based negative binder can be prepared only by utilizing the polyvinylidene fluoride with larger molecular weight difference, and the method is simple and easy to implement, low in cost, free of pollution and easy to industrialize.
2. The composite binder has the advantages of good structural stability, high electrolyte retention amount and the like, and a more stable and elastic network frame can be constructed between electrodes after the polyvinylidene fluoride with different molecular weights is compounded, so that the technical problems of silicon material pulverization and poor multiplying power charge-discharge performance of the silicon-based negative electrode material in the process of lithium ion intercalation and deintercalation can be solved.
3. The silicon-carbon negative electrode prepared by the method has excellent mechanical properties, particularly excellent flexibility and bonding strength, greatly improves the technical problem that cracks are easily generated on the surface of a pole piece in the roll-to-roll lamination process of the silicon-carbon negative electrode, further reduces the defective rate, and has the potential of large-scale production.
4. The composite binder prepared by the invention combines the advantages of good thermal stability, good chemical resistance, easy processability and the like of polyvinylidene fluoride with different molecular weights, effectively widens the application range of the material, and further has wide application prospect in the technical fields of flexible lithium batteries, optical catalysis, air purification and the like.
5. The high-performance composite binder has excellent structural stability and electrolyte retention, can solve the technical problem of pulverization of a silicon material in the process of lithium ion intercalation and deintercalation of the silicon-based negative electrode material, effectively solves the problems of low cycle performance, poor rate performance and the like of a silicon-carbon negative electrode prepared in the prior art, and improves the performance of a battery.
Drawings
FIG. 1 is an SEM image of polyvinylidene fluoride (weight average molecular weight 2200000) powder particles.
FIG. 2 is an SEM image of polyvinylidene fluoride (weight average molecular weight 1050000) powder particles.
FIG. 3 is an SEM image of the surface topography of the negative electrode tab of example 1.
Fig. 4 is a rate diagram of a silicon carbon negative half cell of example 1.
FIG. 5 is an SEM image of polyvinylidene fluoride (weight average molecular weight 570000) powder particles.
FIG. 6 is an SEM image of the surface topography of the negative electrode plate of example 2.
FIG. 7 is an SEM image of the surface topography of the negative electrode plate of example 3.
FIG. 8 is an SEM image of the surface morphology of the negative electrode plate of the comparative example.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
Polyvinylidene fluoride (model VW-770) having a weight average molecular weight of 2200000, polyvinylidene fluoride (model threeway 5130) having a weight average molecular weight of 1050000, and polyvinylidene fluoride (model akoma 761A) having a weight average molecular weight of 570000 were used in the following examples.
The powder of the negative electrode material used in the following examples was a beiibrari (650 type) silicon carbon composite powder (SiO)x:C＝7:3)。
The assembly method of the CR2025 type half cell described in the following examples was: the pole piece is cut into a circular sheet with the diameter of 13mm by a cutter, then the circular sheet, the positive plate and the diaphragm are sequentially stacked according to the sequence (the current collector of the pole piece faces the positive plate shell), then electrolyte is injected, then the lithium plate, the gasket, the elastic sheet and the negative plate shell are sequentially stacked on the diaphragm, and finally the CR2025 button cell is assembled by an electric sealing machine of the button cell under the conditions that the sealing pressure and the sealing time are respectively 350N and 20S.
Example 1
A preparation method of a high-performance composite binder and a silicon-based negative plate comprises the following specific steps:
(1) weighing 3g of composite polyvinylidene fluoride powder, placing the composite polyvinylidene fluoride powder in a ball mill, wherein the composite polyvinylidene fluoride powder consists of polyvinylidene fluoride powder with the weight average molecular weights of 2200000 and 1050000 respectively, the mass ratio is 7:3, and then, the weight average molecular weight is 1200 r.min-1Mixing materials through a ball mill at a rotating speed to prepare the composite binder.
(2) Adding the composite binder prepared in the step (1) into N-methyl pyrrolidone, and heating at 25 ℃ for 1100 r.min-1Stirring for 48 hours at a rotating speed to dissolve the composite binder in the N-methyl pyrrolidone to prepare a binder glue solution with the mass fraction of 5.5%.
(3) Adding conductive agent Keqin black into the glue solution, wherein the mass ratio of the glue solution to the conductive agent Keqin black is 18:1, and the glue solution is heated at 25 ℃ for 300 r.min-1Stirring for 25min at the rotating speed of the adhesive to disperse the conductive agent in the adhesive liquid to prepare the conductive adhesive liquid.
(4) Mixing fenofibrate (650 type) silicon-carbon composite material powder (SiO)xC7: 3) is added into the conductive glue solution, the mass ratio of the conductive glue solution to the silicon-carbon composite powder is 12:5, and the mixture is stirred in a stirrer at the temperature of 25 ℃ for 500 r.min-1Stirring at the rotating speed of (1) for 30min, adding N-methylpyrrolidone to adjust the viscosity of the solution to 10000 mPa.s, and stirring at 500 r.min-1Stirring at a rotating speed for 20min to prepare the electrode slurry.
(5) Coating the electrode slurry on a negative current collector by an automatic coating machine at a thickness of 75 μm, wherein the coating temperature is 25 deg.C and the coating speed is 2.5 m.min-1And when the water content of the slurry is below 100ppm during coating, obtaining the current collector coated with the electrode slurry.
(6) And carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry, wherein the vacuum high-temperature solvent removal treatment specifically comprises the following steps: placing the current collector coated with the electrode slurry in an oven at the temperature of 100 ℃, wherein the relative vacuum degree value is less than or equal to-0.1 MPa, and the treatment time is 25 h;
(7) rolling the slurry coated on the negative current collector, and controlling the compacted surface density of the slurry to be 2.5 g-cm-2And after rolling, the thickness of the negative pole piece is 35 mu m, and a semi-finished product of the negative pole piece is prepared.
(8) And (4) blanking the rolled semi-finished product of the negative plate into a designed size.
Measuring the viscosity of the glue solution to 3200mPa & s by using an SNB series digital display viscometer, assembling the silicon-carbon negative electrode prepared in the step 7 into a CR2025 type half battery, and performing battery performance test to obtain the silicon-carbon negative electrode half battery, wherein the specific capacity of the first loop of the silicon-carbon negative electrode half battery in 0.1C discharging is 632mAh & g-1And the specific capacity of 1C during discharge is 327mAh g-1。
Example 2
A preparation method of a high-performance composite binder and a silicon-based negative plate comprises the following specific steps:
(1) weighing 3.5g of composite polyvinylidene fluoride powder in a ball mill, wherein the composite polyvinylidene fluoride powder consists of polyvinylidene fluoride powder with weight average molecular weights of 2200000 and 1050000 respectively, the mass ratio is 4:1, and then the weight ratio is 1000 r.min-1Mixing materials through a ball mill at a rotating speed to prepare a composite materialAnd (3) a binder.
(2) Adding the composite binder prepared in the step 1 into N-methyl pyrrolidone, and heating at the temperature of 15 ℃ for 1100 r.min-1Stirring for 36h at a rotating speed to dissolve the composite binder in the N-methyl pyrrolidone to prepare a binder glue solution with the mass fraction of 10%.
(3) Adding conductive agent Keqin black into the glue solution, wherein the mass ratio of the glue solution to the conductive agent is 15:1, and the glue solution and the conductive agent are heated at 15 ℃ for 400 r.min-1Stirring for 20min at the rotating speed of the adhesive to disperse the conductive agent in the adhesive liquid to prepare the conductive adhesive liquid.
(4) Mixing fenofibrate (650 type) silicon-carbon composite material powder (SiO)xC7: 3) is added into the conductive adhesive liquid, the mass ratio of the conductive adhesive liquid to the silicon-carbon composite powder is 4:1, and the mixture is stirred in a stirrer at the temperature of 30 ℃ for 500 r.min-1Stirring at the rotation speed of (1) for 25min, adding N-methylpyrrolidone to adjust the solution viscosity to 9000mPa & s, and stirring at 500r & min-1Stirring for 15min at a rotating speed to prepare the electrode slurry.
(5) Coating the electrode slurry on a negative current collector by an automatic coating machine at a thickness of 100 μm, wherein the coating temperature is 20 deg.C and the coating speed is 4m min-1And when the slurry is coated, the water content of the slurry is below 80ppm, and the current collector coated with the electrode slurry is obtained.
(6) And (2) carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry, wherein the vacuum high-temperature solvent removal treatment specifically comprises the following steps: placing the current collector coated with the electrode slurry in an oven at the temperature of 120 ℃, wherein the relative vacuum degree value is less than or equal to-0.3 MPa, and the treatment time is 24 h;
(7) rolling the slurry coated on the negative current collector, and controlling the compacted surface density of the slurry to be 3.2 g-cm-2And after rolling, the thickness of the negative pole piece is 55 mu m, and a semi-finished product of the negative pole piece is prepared.
(8) And (4) blanking the rolled semi-finished product of the negative plate into a designed size.
Measuring the viscosity of the glue solution to 2400mPa & s by using an SNB series digital display viscometer, assembling the silicon-carbon cathode prepared in the step 7 into a CR2025 type half battery, and carrying out battery performance test to obtain the silicon-carbonThe specific capacity of the first circle of the negative electrode half battery in 0.1C discharge is 610mAh g-1And the specific capacity of 1C during discharge is 282mAh g-1。
Example 3
A preparation method of a high-performance composite binder and a silicon-based negative plate comprises the following specific steps:
(1) weighing 4g of composite polyvinylidene fluoride powder, placing the composite polyvinylidene fluoride powder into a ball mill, wherein the composite polyvinylidene fluoride powder consists of polyvinylidene fluoride powder with the weight average molecular weights of 2200000, 1050000 and 570000 respectively, the mass ratio is 3:2:1, and then the mixture is stirred at 900 r.min-1Mixing materials through a ball mill at a rotating speed to prepare the composite binder.
(2) Adding the composite binder prepared in the step 1 into N-methyl pyrrolidone, and performing reaction at the temperature of 30 ℃ for 1000 r.min-1Stirring for 30 hours at a rotating speed to dissolve the composite binder in the N-methyl pyrrolidone to prepare a binder glue solution with the mass fraction of 8%.
(3) Adding conductive agent Keqin black into the glue solution, wherein the mass ratio of the glue solution to the conductive agent is 14:1, and the glue solution and the conductive agent are heated at 30 ℃ for 400 r.min-1Stirring for 15min at the rotating speed of the adhesive to disperse the conductive agent in the adhesive liquid to prepare the conductive adhesive liquid.
(4) Mixing fenofibrate (650 type) silicon-carbon composite material powder (SiO)xC7: 3) is added into the conductive adhesive liquid, the mass ratio of the conductive adhesive liquid to the silicon-carbon composite powder is 5:1, and the mixture is stirred in a stirrer at the temperature of 20 ℃ for 600r min-1Stirring at the rotating speed of (1) for 30min, adding N-methylpyrrolidone to adjust the viscosity of the solution to 9000mPa & s, and stirring at 600r & min-1Stirring for 15min at a rotating speed to prepare the electrode slurry.
(5) Coating the electrode slurry on a negative current collector by an automatic coating machine at a thickness of 150 μm, wherein the coating temperature is 23 deg.C and the coating speed is 1.0m min-1And the water content of the slurry during coating is less than 90ppm, and the current collector coated with the electrode slurry is obtained.
(6) And carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry, wherein the vacuum high-temperature solvent removal treatment specifically comprises the following steps: placing the current collector coated with the electrode slurry in an oven at the temperature of 80 ℃, wherein the relative vacuum degree value is less than or equal to-0.2 MPa, and the treatment time is 20 h;
(7) rolling the slurry coated on the negative current collector, and controlling the compacted surface density of the slurry to be 3.8 g-cm-2And after rolling, the thickness of the negative pole piece is 65 mu m, and a semi-finished product of the negative pole piece is prepared.
(8) And (4) blanking the rolled semi-finished product of the negative plate into a designed size.
Measuring the viscosity of the glue solution to be 2000mPa & s by an SNB series digital display viscometer, assembling the silicon-carbon negative electrode prepared in the step 7 into a CR2025 type half battery, and carrying out battery performance test to obtain the silicon-carbon negative electrode half battery, wherein the specific capacity of the first loop of the silicon-carbon negative electrode half battery in 0.1C discharging is 602mAh & g-1And the specific capacity of 1C during discharge is 270 mAh.g-1。
Comparative example
A preparation method of a monomolecular binder and a silicon-based negative plate comprises the following specific steps:
(1) weighing 3g polyvinylidene fluoride with molecular weight of 1050000, adding into N-methylpyrrolidone, and heating at 30 deg.C for 800 r.min-1Stirring for 20h at the rotating speed to prepare the adhesive liquid with the mass fraction of 5.5 percent.
(2) Adding conductive agent Keqin black into the glue solution, wherein the mass ratio of the glue solution to the conductive agent is 17:1, and the glue solution is heated at 25 ℃ for 900 r.min-1Stirring for 15min at the rotating speed of the adhesive to disperse the conductive agent in the adhesive liquid to prepare a conductive adhesive liquid;
(3) adding fibrate (650 type) silicon-carbon composite powder (SiO) into the conductive liquidxC is 7:3), the mass ratio of the conductive liquid to the silicon-carbon composite powder is 5:1, and the mixing ratio is 500 r.min-1Stirring at the rotation speed of (1) for 20min, adding N-methylpyrrolidone to adjust the viscosity of the solution to 8000 mPa.s at 500 r.min-1Stirring for 10min at a rotating speed to prepare slurry.
(4) Coating the electrode slurry on a negative current collector by an automatic coating machine at a thickness of 75 μm, wherein the coating temperature is 40 deg.C and the coating speed is 4.5 m.min-1And when the slurry is coated, the water content of the slurry is below 95ppm, and the current collector coated with the electrode slurry is obtained.
(5) And (2) carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry, wherein the vacuum high-temperature solvent removal treatment specifically comprises the following steps: placing the current collector coated with the electrode slurry in an oven at the temperature of 110 ℃, wherein the relative vacuum degree value is less than or equal to-0.1 MPa, and the treatment time is 12 h;
(6) rolling the slurry coated on the negative current collector, and controlling the compacted surface density of the slurry to be 2.7 g-cm-2And after rolling, the thickness of the negative pole piece is 35 mu m, and a semi-finished product of the negative pole piece is prepared.
(7) And blanking the rolled semi-finished product of the negative plate into a designed size.
Measuring the viscosity of the glue solution to be 1500mPa & s by an SNB series digital display viscometer, assembling the silicon-carbon negative electrode prepared in the step 7 into a CR2025 type half battery, and performing battery performance test to obtain the silicon-carbon negative electrode half battery, wherein the first-loop specific capacity of the silicon-carbon negative electrode half battery in 0.1C discharging is 580mAh & g-1And the specific capacity of 1C during discharge is 221mAh g-1。
Test example 1:
the polyvinylidene fluoride (molecular weight 2200000) used in the examples was subjected to SEM test, and the obtained spectrum was as shown in fig. 1.
Test example 2:
the polyvinylidene fluoride (molecular weight 1050000) used in the examples was subjected to SEM test, and the obtained spectrum is shown in FIG. 2.
Test example 3:
the high-performance composite binder silicon-based negative electrode prepared in example 1 was subjected to SEM test, and the obtained spectrum is shown in fig. 3.
Test example 4:
the high-performance composite binder silicon-based negative electrode prepared in example 1 is assembled into a CR2025 type half cell, and a half cell rate performance test is performed, and the test result is shown in fig. 4. As can be seen from FIG. 4, the specific capacity of the first circle of the silicon-carbon negative electrode half cell at 0.1C discharge time is 632mAh g-1And the specific capacity of 1C during discharge is 327mAh g-1。
Test example 5:
the polyvinylidene fluoride (molecular weight 570000) used in the examples was subjected to SEM test, and the obtained spectrum is shown in FIG. 5.
Test example 6:
the high-performance composite binder silicon-based negative electrode prepared in example 2 was subjected to SEM test, and the obtained spectrum is shown in fig. 6.
Test example 7:
the high-performance composite binder silicon-based negative electrode prepared in example 3 was subjected to SEM test, and the obtained spectrum is shown in fig. 7.
Test example 8:
the monomolecular binder silicon-based negative electrode plate prepared in example 4 was subjected to SEM test, and the obtained spectrum was shown in fig. 8.
The embodiments described above are presented to enable those skilled in the art to make and use the invention. It will be readily apparent to those skilled in the art that various modifications to this embodiment can be readily made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the embodiments described herein, and those skilled in the art should make improvements and modifications to the present invention based on the disclosure of the present invention within the protection scope of the present invention.
Claims (9)
1. The preparation method of the silicon-based negative plate is characterized by comprising the following steps of:
step 1: mixing 10-80 wt% of polyvinylidene fluoride with the weight-average molecular weight of 150-300 ten thousand, 10-70 wt% of polyvinylidene fluoride with the weight-average molecular weight of 80-140 ten thousand and 0-60 wt% of polyvinylidene fluoride with the weight-average molecular weight of 57-60 ten thousand by a ball mill to obtain a composite binder;
step 2: dissolving the composite binder obtained in the step 1 in an organic solvent to obtain a binder glue solution;
and step 3: dispersing a conductive agent in the adhesive liquid obtained in the step 2 to obtain a conductive liquid adhesive;
and 4, step 4: adding silicon-carbon composite material powder and an organic solvent into the conductive glue solution obtained in the step 3 to prepare electrode slurry;
and 5: coating the electrode slurry obtained in the step (4) on a negative current collector through an automatic coating machine to obtain the current collector coated with the electrode slurry;
step 6: carrying out vacuum high-temperature solvent removal treatment on the current collector coated with the electrode slurry;
and 7: and rolling the obtained negative pole piece to obtain the silicon-based negative pole piece.
2. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the silicon-carbon composite material is a mixture of silicon-based and carbon-based materials; the carbon-based material is one or more of hard carbon, soft carbon, natural graphite and artificial graphite; the silicon-based material is one or more of micron silicon, nano silicon, silicon monoxide and silicon oxide.
3. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the conductive agent is one of acetylene black, ketjen black, carbon fiber and Super P; the organic solvent is one of N-methyl pyrrolidone, acetonitrile and dimethylformamide; the mass fraction of the adhesive liquid is 5-50%; the mass fraction of the conductive agent in the conductive glue solution is 5-20%; the viscosity of the electrode slurry is 500-25000 mPa-s.
4. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the specific step of dissolving the composite binder obtained in the step 1 in the organic solvent in the step 2 comprises: adding the composite binder obtained in the step 1 into an organic solvent at the temperature of 10-60 ℃ for 100-2500 r.min-1Stirring for 10-72h at the rotating speed to prepare the adhesive liquid.
5. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the specific step of dispersing the conductive agent in the binder glue solution obtained in the step 2 comprises the following steps: adding conductive agent into the adhesive liquid, at the temperature of 10-60 ℃ and at the temperature of 100--1Stirring for 5-300min at the rotating speed of (1).
6. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the specific preparation step of the electrode slurry in the step 4 comprises the following steps: adding the silicon-carbon composite material powder into the conductive glue solution, and performing heat treatment at 10-60 ℃ for 1000 r.min at 100--1Stirring at the rotating speed of (1) for 5-100min, adding an organic solvent at the speed of 100--1Stirring at a rotating speed for 10-500min to obtain the electrode slurry.
7. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the coating process in the step 5 comprises: coating the electrode slurry on a negative current collector at a thickness of 10-300 μm at a temperature of 15-60 deg.C with an automatic coating machine at a coating speed of 1-8m min-1The water content of the slurry at the time of coating is 100ppm or less.
8. The method for preparing the silicon-based negative electrode plate according to claim 1, wherein the vacuum high-temperature desolvation treatment comprises the following specific steps: and (3) placing the current collector coated with the electrode slurry in an oven at the temperature of 80-130 ℃, wherein the relative vacuum degree value is less than or equal to-0.1 MPa, and the treatment time is 10-25 h.
9. The composite binder is characterized by comprising 10-80 wt% of polyvinylidene fluoride with the weight-average molecular weight of 150-300 ten thousand, 10-70 wt% of polyvinylidene fluoride with the weight-average molecular weight of 80-140 ten thousand and 0-60 wt% of polyvinylidene fluoride with the weight-average molecular weight of 57-60 ten thousand.
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| CN113394363B (en) * | 2020-03-13 | 2022-05-20 | 宁德新能源科技有限公司 | Preparation method of negative pole piece, battery and electronic device |
| CN111781040B (en) * | 2020-06-18 | 2022-09-06 | 合肥国轩高科动力能源有限公司 | Method for processing cross section of lithium ion battery material powder sample |
| CN111682217A (en) * | 2020-07-08 | 2020-09-18 | 重庆金美新材料科技有限公司 | Conductive adhesive solution and battery pole piece |
| WO2023023945A1 (en) * | 2021-08-24 | 2023-03-02 | 株式会社吴羽 | Adhesive composition, electrode mixture, electrode, and non-aqueous electrolyte secondary battery |
| CN114497444B (en) * | 2022-02-16 | 2023-05-30 | 华鼎国联四川动力电池有限公司 | Ceramic slurry for lithium ion battery pole piece protective coating and preparation method thereof |
| WO2024026702A1 (en) * | 2022-08-03 | 2024-02-08 | 宁德时代新能源科技股份有限公司 | Negative electrode sheet and preparation method therefor, secondary battery, battery module, battery pack, and electrical apparatus |
| WO2024045631A1 (en) * | 2022-08-30 | 2024-03-07 | 宁德时代新能源科技股份有限公司 | Binder composition, positive electrode sheet, secondary battery and electric device |
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