CN112466681A - Electrode and preparation method thereof - Google Patents
Electrode and preparation method thereof Download PDFInfo
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- CN112466681A CN112466681A CN202011306435.0A CN202011306435A CN112466681A CN 112466681 A CN112466681 A CN 112466681A CN 202011306435 A CN202011306435 A CN 202011306435A CN 112466681 A CN112466681 A CN 112466681A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
- H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The invention relates to an electrode for a supercapacitor and a preparation method thereof, wherein the preparation method comprises the following steps: s1, dry-mixing the active substance, the conductive agent and the binder uniformly to obtain mixed dry powder; s2, impacting the mixed dry powder by using electromagnetic shock waves to obtain fiberized mixed dry powder; s3, rolling the fiberized mixed dry powder to form a self-supporting dry film; and S4, compounding the self-supporting dry film on the current collector after heating the current collector by using a high-frequency electromagnetic induction device to obtain the electrode. When the electrode obtained by the preparation method is applied to the super capacitor, the initial capacity, the direct current internal resistance and the high-temperature load performance of the super capacitor are obviously improved.
Description
Technical Field
The invention relates to the technical field of super capacitors, in particular to an electrode for a super capacitor and a preparation method thereof.
Background
The double-layer type supercapacitor consists of electrodes, a separator, an electrolyte and a case, and stores energy by forming an electric double layer at the interface of the electrodes and the electrolyte. Wherein, the electrode is the core component of the super capacitor. The electrode preparation process of the supercapacitor taking the carbon material as the active material generally needs to bond the active material and the conductive agent to a current collector by using a binder. The preparation process of the electrode for the supercapacitor can be divided into two types according to whether a solvent for wetting the binder, the active material and the conductive agent is introduced in the mixing process of the electrode preparation: wet and dry processes.
The wet process is the traditional process for preparing the electrode for the super capacitor. When the electrode for the supercapacitor is prepared by a wet process, firstly, a binder, an active substance, a conductive agent, a dispersing agent and a solvent are stirred into slurry, then the stirred slurry is coated on a current collector to form a wet electrode, the coated wet electrode is transferred to an oven to be dried to obtain a dry electrode, and finally the dry electrode is rolled to obtain a finished electrode. The process for preparing the electrode for the supercapacitor according to the wet method has the defects of complex working procedures, high equipment cost, solvent, high energy consumption, low energy density and discharge rate, drying cracking caused by over-thick coating and the like.
For example, in JP2010171346A, a wet compounding process is adopted to sequentially add water vapor activated carbon, alkali activated carbon and a binder into a dispersion solvent and stir the mixture into slurry, and then the stirred slurry is sequentially coated, dried and rolled to obtain a finished electrode. The solid content of the slurry prepared by the simple wet mixing method is generally low, a large amount of pores are remained due to solvent volatilization in the drying process, so that the compactness of electrode coating contact particles is generally low, and the compaction density of an electrode after rolling is generally lower than 0.6g/cm3。
The dry process is a novel process for preparing the electrode for the supercapacitor, and when the electrode for the supercapacitor is prepared by the dry process, the dry binder, the active substance and the conductive agent are generally stirred into a dry mixture, then the high shear action is carried out on the stirred dry mixture to enable the dry binder in the dry mixture to be fiberized, then the dry mixture after the fiberization treatment is rolled into a self-supporting dry film, and finally the self-supporting dry film is rolled into the self-supporting dry filmAnd compounding the mixture on a current collector to obtain a finished product electrode. Compared with the traditional process for preparing the electrode for the supercapacitor by the wet method, the process for preparing the electrode for the supercapacitor by the dry method has the advantages of simplifying working procedures, reducing equipment investment, having no solvent, having low energy consumption and reducing CO2The discharge, the environmental friendliness, higher active substance loading capacity, higher energy density, larger charge-discharge multiplying power and the like.
For example, chinese patent CN102569719B discloses a dry process for preparing an electrode for a supercapacitor. The method comprises the following steps: grinding a dry carbon comprising activated carbon and conductive carbon and a fiberizable dry binder particle mixture, compressing the ground dry mixture into a dry film, and applying the dry film to a substrate to form an electrode. The dry process for preparing the electrode simplifies the working procedures to a great extent, reduces the equipment investment, has no solvent and is environment-friendly. However, in the dry process, the dry carbon containing the activated carbon and the conductive carbon and the dry binder particle mixture capable of being fiberized are ground by using air jet to achieve fiberization of the dry binder particles, so that a large amount of compressed air is consumed, the energy consumption is high, the pressure of the air jet is limited, the fiberization degree of the binder particles is low, multiple times of injection are needed, the fiberization direction of the binder particles is uncontrollable in each injection process, the compressed air needs to have an outlet to release pressure after being injected, part of mixed dry powder is taken away in the pressure release process, and the mixed dry powder is adsorbed on a filter bag or a filter screen, so that the material loss is caused.
Disclosure of Invention
The invention aims to:
(1) aiming at the problems of more material loss, uncontrollable fiberization direction of mixed dry powder, large usage amount of binder and the like in the material-gas separation process after the mixed dry powder is ground by using air flow jet in the existing dry electrode process, the fiberization method which has no material loss, controllable fiberization direction and small usage amount of binder is provided;
(2) aiming at the problem that the bonding strength is low after a self-supporting dry film and a current collector are compounded in the existing dry method electrode process, a method for compounding the self-supporting dry film and the current collector with high bonding strength is provided.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
in one aspect, the present invention provides a method for preparing an electrode, comprising the steps of:
s1, dry-mixing the active substance, the conductive agent and the binder uniformly to obtain mixed dry powder;
s2, impacting the mixed dry powder by using electromagnetic shock waves to obtain fiberized mixed dry powder;
s3, rolling the fiberized mixed dry powder to form a self-supporting dry film;
and S4, compounding the self-supporting dry film on the current collector after heating the current collector by using a high-frequency electromagnetic induction device to obtain the electrode.
In some embodiments, the active substance is selected from at least one of graphene, activated carbon powder, activated carbon fiber, activated carbon spheres.
In some embodiments, the conductive agent is selected from at least one of metal powder, conductive graphite, carbon nanotubes, acetylene black, ketjen black, furnace black.
In some embodiments, the binder is a high molecular weight polymer having a molecular weight of 500 to 2000 ten thousand, a crystallinity of 90 to 95%, and a D50 particle size of 400 to 700 μm.
Preferably, the molecular weight of the polymer is 800-1200 ten thousand, the crystallinity is 92-93%, and the particle size of D50 is 600-700 μm.
In some embodiments, the polymer is selected from at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyethylene terephthalate, ethylene-tetrafluoroethylene interpolymer, tetrafluoroethylene-hexafluoropropylene interpolymer, high density polyethylene-polycarbonate.
In the invention, the selected adhesive is a high molecular weight polymer capable of being fiberized, the fiberization degree of the adhesive is closely related to the molecular weight and the crystallinity of the polymer, the polymer molecules with the molecular weight of 500-2000 ten thousand and the crystallinity of 90-95 percent are particles wound into a sphere in a curling way, the electromagnetic shock wave is a plane wave, the polymer chains of the polymer molecules are spread along the direction of the shock wave by adopting the shock wave to form a fully fiberized structure, and the spreading direction of the polymer molecular chains can be controlled by controlling the direction of the shock wave, so that the forming direction of the fiberized structure of the polymer is controlled.
In some embodiments, in step S1, the active material is 60 to 98 wt%, the conductive agent is 1 to 20 wt%, and the binder is 1 to 20 wt%, based on 100 wt% of the total mass of the active material, the conductive agent, and the binder.
Preferably, the total mass of the active substance, the conductive agent and the binder is 100 wt%, the active substance is 80-98 wt%, the conductive agent is 1-10 wt%, and the binder is 1-10 wt%.
More preferably, the total mass of the active material, the conductive agent and the binder is 100 wt%, the active material is 90-98 wt%, the conductive agent is 1-5 wt%, and the binder is 1-10 wt%.
In some embodiments, in step S1, the dry blending process is performed in a double cone rotary vacuum mixer, a double motion mixer, a planetary mixer, a three-dimensional blender, or a V-blender.
In some embodiments, in step S2, the parameters of the electromagnetic shock wave are set as: impact energy is 3-10 MPa, and impact area is 0.1-1 cm2The impact frequency is 10-50 Hz. In this range, the electromagnetic shock wave has a range of action much greater than the D50 particle size of the polymer particles, and the energy of the shock wave is sufficient to cause sufficient fiberization of the polymer molecules.
In particular embodiments of the invention, the impact energy is 3MPa, 4MPa, 5MPa, 6MPa, 7MPa, 8MPa, 9MPa, 10MPa, and the like.
In particular embodiments of the invention, the impact frequency is 10Hz, 15Hz, 16Hz, 20Hz, 25Hz, 30Hz, 32Hz, 35Hz, 40Hz, 45Hz, 50Hz, and the like.
In a particular embodiment of the invention, the impact area is 0.1cm2、0.2cm2、0.3cm2、0.4cm2、0.5cm2、0.6cm2、0.7cm2、0.785cm2、0.8cm2、0.9cm2、1cm2And the like.
In a particular embodiment of the invention, the impact process is: the mixed dry powder is focused and impacted by an electromagnetic shock wave generator to enable the adhesive to be fiberized. In the impact process, the mixed dry powder continuously passes through a sealed pipeline with a certain cross section, such as a guide pipe with the length of 1m and the inner diameter of 1cm, when high-energy impact waves are focused and then applied to the adhesive particles, the adhesive particles are subjected to high shearing force, polymer molecular chains are unfolded to form fibers and generate directional motion, so that the surrounding active substance particles and conductive agent particles are adhered, the energy of the impact waves is absorbed by the adhesive particles, the energy is weakened, and the damage of the high-energy impact waves to the sealed pipeline is avoided.
In some embodiments, the specific operations of step S3 are: conveying the fiberization mixed dry powder to a calender by using an automatic feeding machine to be calendered into a self-supporting dry film; the automatic feeding machine is selected from any one of a vibration blanking powder paving machine, a screw rod feeding machine, an electrostatic transfer feeding machine and a vacuum feeding machine.
In the invention, the fiberization mixed dry powder is placed in a dry environment with the dew point lower than minus 30 ℃ to prevent the fiberization mixed dry powder from agglomerating after absorbing water.
In some embodiments, the self-supporting dry film has a thickness of 30 to 200 μm, preferably 50 to 150 μm.
In particular embodiments of the invention, the self-supporting dry film has a thickness of 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, and the like.
In some embodiments, in step S4, the current collector is a carbon-coated metal foil, and a surface of the current collector contains a conductive adhesive. The current collector can be a current collector with a single surface containing conductive adhesive or with two surfaces containing conductive adhesive.
In some embodiments, the current collector is one of a carbon-coated aluminum foil, a carbon-coated copper foil, a carbon-coated silver foil, a carbon-coated titanium foil, a carbon-coated gold foil, a carbon-coated platinum foil.
In some embodiments, the conductive adhesive is at least one of Achenson Dag Eb-012, Achenson Dag Eb-815, polyacrylate dispersed graphite milk.
The self-supporting dry film can be compounded on one side of the current collector and also can be compounded on the two sides of the current collector.
In a specific embodiment of the invention, the self-supporting dry film is laminated on both sides of the carbon-coated aluminum foil.
In some embodiments, the high frequency electromagnetic induction device has an induction frequency of 200 to 400kHz, a heating time of 2 to 5 seconds, and a heating temperature of 200 to 300 ℃. Within this range, the conductive paste on the surface of the current collector is melted, thereby bonding the self-supporting dry film to the current collector.
In a specific embodiment of the present invention, the induction frequency of the high-frequency electromagnetic induction device is 200kHz, 250kHz, 300kHz, 350kHz, 400kHz, or the like.
In a specific embodiment of the present invention, the heating time of the high-frequency electromagnetic induction device is 2s, 2.5s, 3s, 3.5s, 4s, 4.5s, 5s, or the like.
In a specific embodiment of the present invention, the heating temperature of the high-frequency electromagnetic induction device is 200 ℃, 210 ℃, 221 ℃, 220 ℃, 230 ℃, 236 ℃, 240 ℃, 245 ℃, 250 ℃, 254 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃ or the like.
In another aspect, the invention provides an electrode for a supercapacitor, which is prepared by the above preparation method.
In another aspect, the present invention provides a super capacitor, comprising the above electrode.
The invention has the beneficial effects that:
1. the invention adopts high-energy electromagnetic shock wave to fibrillate the binder, compared with the air jet milling, the shock wave is energy, after the mixed dry powder is impacted, the shock wave energy is weakened, and the pressure is not required to be released from an outlet, thereby avoiding the material loss caused in the material-gas separation process, simultaneously improving the fibrillating degree of the binder, further reducing the using amount of the binder, and obviously improving the tensile stress and tensile strain of a self-supporting dry film, thereby improving the capacity of the super capacitor and reducing the internal resistance.
2. The electromagnetic shock wave can carry out energy focusing, the adhesive can be fully fiberized only through single action, the direction of the shock wave is controllable, the fiberizing direction of the adhesive tends to be consistent, the unidirectional tensile strength and tensile strain of the self-supporting dry film are good, and the self-supporting dry film is favorable for compounding with a current collector and ion transmission, so that the internal resistance of the supercapacitor can be reduced; the airflow jet grinding is difficult to improve energy because the direction of the airflow jet is uncontrollable, and the airflow jet grinding needs to be continuously carried out, so that the fiberization direction of the binder is disordered.
3. The high-frequency electromagnetic induction device is utilized to heat the current collector and then compound the current collector with the self-supporting dry film, so that the heating time is short, and the bonding strength of the dry electrode coating is improved.
4. The super capacitor obtained by adopting the electrode provided by the invention is obviously improved in the aspects of initial capacity, direct current internal resistance and high temperature load performance.
Definition of terms
All ranges cited herein are inclusive, unless expressly stated to the contrary.
The term "at least one" is used herein to describe the elements and components described herein. This is done merely for convenience and to provide a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.
The numbers in this disclosure are approximate, regardless of whether the word "about" or "approximately" is used. The numerical value of the number may have differences of 1%, 2%, 5%, 7%, 8%, 10%, etc. Whenever a number with a value of N is disclosed, any number with a value of N +/-1%, N +/-2%, N +/-3%, N +/-5%, N +/-7%, N +/-8% or N +/-10% is explicitly disclosed, wherein "+/-" means plus or minus, and a range between N-10% and N + 10% is also disclosed.
The following definitions, as used herein, should be applied unless otherwise indicated. For the purposes of the present invention, the chemical elements are in accordance with the CAS version of the periodic Table of elements, and the 75 th version of the handbook of chemistry and Physics, 1994. In addition, general principles of Organic Chemistry can be referred to as described in "Organic Chemistry", Thomas Sorrell, University Science Books, Sausaltito: 1999, and "March's Advanced Organic Chemistry" by Michael B.Smith and Jerry March, John Wiley & Sons, New York:2007, the entire contents of which are incorporated herein by reference.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of embodiments of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety, unless a specific section is cited. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Drawings
FIG. 1 is a scanning electron micrograph of the fiberized mixed dry powder of example 1;
FIG. 2 is a scanning electron micrograph of the fiberized mixed dry powder of example 2;
FIG. 3 is a scanning electron micrograph of the fiberized mixed dry powder of the comparative example;
FIG. 4 is a schematic structural view of a heating composite electrode of the high-frequency electromagnetic induction device; wherein, 1 is carbon-coated aluminum foil; 2 is a self-supporting dry film; 3 is an induction heating power supply; 4 is a lead; 5 is a metal device; 6 is an induction coil; and 7, a roller.
Detailed Description
The following description is of the preferred embodiment of the present invention only, and is not intended to limit the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
The polytetrafluoroethylene powder used in the following examples had a molecular weight of 960 ten thousand, a crystallinity of 92.7% and a D50 particle size of 672 μm.
Example 1
S1, sequentially weighing 950g of activated carbon powder, 20g of acetylene black and 30g of polytetrafluoroethylene powder, adding the materials into a double-cone rotary vacuum mixer, and uniformly mixing to obtain 1000g of mixed dry powder;
s2, connecting a double-cone rotary vacuum mixer and a material receiving barrel from top to bottom by a guide pipe with the length of 1m and the inner diameter of 1cm, immediately focusing and impacting the freely falling mixed dry powder in the guide pipe by a high-energy electromagnetic shock wave generator after opening a guide pipe switch, wherein the shock energy is set to be 6MPa, the shock frequency is set to be 25Hz, and the shock area is set to be 0.785cm2Until all the mixed dry powder in the double-cone rotary vacuum mixer freely falls into a material receiving barrel below through a guide pipe, 1000g of fiberized mixed dry powder is obtained;
s3, quantitatively dropping the fiberized mixed dry powder obtained in the step S2 to the center of a double-roller gap of a calender by using a vibration blanking and powder spreading machine according to the width of 300mm and the thickness of 230 mu m, and obtaining a self-supporting dry film with the thickness of 100 mu m after calendering by the calender;
s4, heating the carbon-coated aluminum foil for 2S by a high-frequency electromagnetic induction device at the induction frequency of 250kHz, instantly heating the carbon-coated aluminum foil to 221 ℃ to melt the conductive adhesive on the two sides of the carbon-coated aluminum foil, and immediately compounding the self-supporting dry film obtained in the step S3 on the carbon-coated aluminum foil on the two sides by a compound machine to obtain the electrode.
Example 2
S1, weighing 930g of activated carbon powder, 20g of acetylene black and 50g of polytetrafluoroethylene powder in sequence, adding the weighed materials into a double-cone rotary vacuum mixer, and uniformly mixing to obtain 1000g of mixed dry powder;
s2, connecting a double-cone rotary vacuum mixer and a material receiving barrel from top to bottom by a guide pipe with the length of 1m and the inner diameter of 1cm, immediately focusing and impacting the freely falling mixed dry powder in the guide pipe by a high-energy electromagnetic shock wave generator after opening a guide pipe switch, wherein the shock energy is set to be 6MPa, the shock frequency is set to be 25Hz, and the shock area is set to be 0.785cm2Until all the mixed dry powder in the double-cone rotary vacuum mixer freely falls into a material receiving barrel below through a guide pipe, 1000g of fiberized mixed dry powder is obtained;
s3, quantitatively dropping the fiberized mixed dry powder obtained in the step S2 to the center of a double-roller gap of a calender by using a vibration blanking and powder spreading machine according to the width of 300mm and the thickness of 230 mu m, and obtaining a self-supporting dry film with the thickness of 100 mu m after calendering by the calender;
s4, heating the carbon-coated aluminum foil for 2S by a high-frequency electromagnetic induction device at the induction frequency of 300kHz, instantly heating the carbon-coated aluminum foil to 236 ℃ to melt the conductive adhesive on the two sides of the carbon-coated aluminum foil, and immediately compounding the self-supporting dry film obtained in the step S3 on the carbon-coated aluminum foil on the two sides by a compound machine to obtain the electrode.
Example 3
S1, weighing 930g of activated carbon powder, 20g of acetylene black and 50g of polytetrafluoroethylene powder in sequence, adding the weighed materials into a double-cone rotary vacuum mixer, and uniformly mixing to obtain 1000g of mixed dry powder;
s2, connecting a double-cone rotary vacuum mixer and a material receiving barrel from top to bottom by a guide pipe with the length of 1m and the inner diameter of 1cm, immediately focusing and impacting the freely falling mixed dry powder in the guide pipe by a high-energy electromagnetic shock wave generator after opening a guide pipe switch, wherein the shock energy is set to be 8MPa, the shock frequency is set to be 32Hz, and the shock area is set to be 0.785cm2Until all the mixed dry powder in the double-cone rotary vacuum mixer freely falls into a material receiving barrel below through a guide pipe, 1000g of fiberized mixed dry powder is obtained;
s3, quantitatively dropping the fiberized mixed dry powder obtained in the step S2 to the center of a double-roller gap of a calender by using a vibration blanking and powder spreading machine according to the width of 300mm and the thickness of 230 mu m, and obtaining a self-supporting dry film with the thickness of 100 mu m after calendering by the calender;
s4, heating the carbon-coated aluminum foil for 2S by a high-frequency electromagnetic induction device at the induction frequency of 350kHz, instantly heating the carbon-coated aluminum foil to 245 ℃ to melt the conductive adhesive on the two sides of the carbon-coated aluminum foil, and immediately compounding the self-supporting dry film obtained in the step S3 on the carbon-coated aluminum foil on the two sides by a compound machine to obtain the electrode.
Example 4
S1, weighing 930g of activated carbon powder, 20g of acetylene black and 50g of polytetrafluoroethylene powder in sequence, adding the weighed materials into a double-cone rotary vacuum mixer, and uniformly mixing to obtain 1000g of mixed dry powder;
s2, self-loading with 1m long catheter with 1cm inner diameterA double-cone rotary vacuum mixer and a material receiving barrel are connected downwards, the free falling mixed dry powder in the impact conduit is immediately focused by a high-energy electromagnetic shock wave generator after the conduit switch is opened, the impact energy is set to be 9MPa, the impact frequency is set to be 50Hz, and the impact area is set to be 0.785cm2Until all the mixed dry powder in the double-cone rotary vacuum mixer freely falls into a material receiving barrel below through a guide pipe, 1000g of fiberized mixed dry powder is obtained;
s3, quantitatively dropping the fiberized mixed dry powder obtained in the step S2 to the center of a double-roller gap of a calender by using a vibration blanking and powder spreading machine according to the width of 300mm and the thickness of 230 mu m, and obtaining a self-supporting dry film with the thickness of 100 mu m after calendering by the calender;
s4, heating the carbon-coated aluminum foil for 2S by a high-frequency electromagnetic induction device at the induction frequency of 300kHz, instantly heating the carbon-coated aluminum foil to 254 ℃ to melt the conductive adhesive on the two sides of the carbon-coated aluminum foil, and immediately compounding the self-supporting dry film obtained in the step S3 on the carbon-coated aluminum foil on the two sides by a compound machine to obtain the electrode.
Comparative example
S1, weighing 930g of activated carbon powder, 20g of acetylene black and 50g of polytetrafluoroethylene powder in sequence, adding the weighed materials into a double-cone rotary vacuum mixer, and uniformly mixing to obtain 1000g of mixed dry powder;
s2, carrying out jet grinding on the mixed dry powder obtained in the step S1 by using 1MPa compressed air, and carrying out material-gas separation by using a film-coated filter bag with the aperture of 0.3 mu m to obtain 960g of fibrosis mixed dry powder;
s3, stacking and adding the fiberized mixed dry powder obtained in the step S2 between the roll gaps of a calender, and obtaining a self-supporting dry film with the thickness of 100 mu m after 3 times of calendering;
and S4, adjusting the roll surface temperature of a compound machine to 236 ℃, and compounding the self-supporting dry film obtained in the step S3 on the carbon-coated aluminum foil on two sides to obtain the electrode.
Evaluation of Performance
Testing the performance of the self-supporting dry film and the electrode:
1) and calculating the material loss rate of the mixed dry powder after the fiberization treatment.
2) The self-supporting dry films obtained in examples 1 to 4 and comparative example were punched into a sample strip of 8cm × 1cm using a die cutter, and the tensile strength and tensile strain of the self-supporting dry film sample strip were tested using a U.S. Instron universal testing machine.
3) The supported dry films obtained in examples 1 to 4 and comparative examples were punched into 10cm × 2cm sample strips by a die cutter, the electrode active material layer was bonded to a test platform of a peel strength tester by a 3M double-sided tape, one end of the carbon-coated aluminum foil was stretched at a stretching speed of 50mm/min in the vertical direction, and the stress at the time of peeling was measured. This measurement was performed 3 times, and the average value was determined as the peel strength.
The test results are shown in table 1.
TABLE 1
| Numbering | Percentage of Material loss (%) | Tensile Strength (N/cm) | Tensile strain (%) | Peel strength (N/cm) |
| Example 1 | 0 | 1.8 | 10.8 | 2.2 |
| Example 2 | 0 | 2.6 | 12.5 | 2.2 |
| Example 3 | 0 | 2.9 | 12.9 | 2.2 |
| Example 4 | 0 | 3.0 | 13.1 | 2.2 |
| Comparative example | 4 | 1.1 | 6.4 | 2.0 |
And (3) testing the electrical property of the super capacitor:
the electrodes obtained in examples 1 to 4 and comparative examples were cut into pieces having a width of 35mm, a positive electrode length of 570mm and a negative electrode length of 525mm by a cutter. A TF4035 type diaphragm special for a super capacitor produced by the Japan NKK company is adopted to be wound into a cell together with the cut positive and negative electrodes. And (3) putting 10 battery cores into DLC301 electrolyte, vacuum-dipping to a saturated liquid-absorbing state, putting the dipped battery cores into a shell, sealing to obtain a phi 22X 45 welding-pin type super capacitor monomer, and testing the initial capacity and the internal resistance of the monomer. The obtained monomer was electrified at 60 ℃ for 2000 hours at a constant voltage of 2.7V, and then the capacity and internal resistance of the monomer were retested. The test results are shown in table 2.
TABLE 2
As can be seen from the test results in tables 1 and 2, the preparation method of the invention has no material loss in the process of fiberizing the mixed dry powder, the prepared self-supporting dry film has good tensile strength, large tensile strain and large peeling strength with the current collector, and the assembled super capacitor has high capacity, low internal resistance and good high-temperature load performance.
As can be seen from fig. 1 to 3, the fiberization direction of the binder obtained by the electromagnetic shock wave method is controllable, the fiberization direction is basically consistent, and the fiberization direction of the binder obtained by the conventional air jet grinding method is disordered, so that the performance of the obtained supercapacitor is poor.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A preparation method of an electrode is characterized by comprising the following steps:
s1, dry-mixing the active substance, the conductive agent and the binder uniformly to obtain mixed dry powder;
s2, impacting the mixed dry powder by using electromagnetic shock waves to obtain fiberized mixed dry powder;
s3, rolling the fiberized mixed dry powder to form a self-supporting dry film;
and S4, compounding the self-supporting dry film on the current collector after heating the current collector by using a high-frequency electromagnetic induction device to obtain the electrode.
2. The preparation method according to claim 1, wherein the active material is selected from at least one of graphene, activated carbon powder, activated carbon fiber, and activated carbon sphere; the conductive agent is at least one selected from metal powder, conductive graphite, carbon nano tube, acetylene black, Ketjen black and furnace black.
3. The preparation method according to claim 1, wherein the binder is a high molecular weight polymer having a molecular weight of 500 to 2000 ten thousand, a crystallinity of 90 to 95%, and a D50 particle size of 400 to 700 μm;
preferably, the polymer is selected from at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyethylene terephthalate, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, high density polyethylene-polycarbonate.
4. The method according to claim 1, wherein in step S1, the active material is 60 to 98 wt%, the conductive agent is 1 to 20 wt%, and the binder is 1 to 20 wt%, based on 100 wt% of the total mass of the active material, the conductive agent, and the binder.
5. The method of claim 1, wherein the dry mixing process is performed in a double cone rotary vacuum mixer, a double motion mixer, a planetary mixer, a three-dimensional blender, or a V-blender in step S1.
6. The method according to claim 1, wherein in step S2, the parameters of the electromagnetic shock wave are set as: impact energy is 3-10 MPa, and impact area is 0.1-1 cm2The impact frequency is 10-50 Hz.
7. The preparation method according to claim 1, wherein the specific operation of step S3 is: conveying the fiberization mixed dry powder to a calender by using an automatic feeding machine to be calendered into a self-supporting dry film; the automatic feeding machine is selected from any one of a vibration blanking powder paving machine, a screw rod feeding machine, an electrostatic transfer feeding machine and a vacuum feeding machine.
8. The preparation method according to claim 1, wherein in the step S4, the current collector is a carbon-coated metal foil, and the surface of the current collector contains a conductive adhesive, and the conductive adhesive is at least one of Achenson Dag Eb-012, Achenson Dag Eb-815 and polyacrylate-dispersed graphite milk;
preferably, the induction frequency of the high-frequency electromagnetic induction device is 200-400 kHz, the heating time is 2-5 s, and the heating temperature is 200-300 ℃.
9. An electrode for a supercapacitor, which is produced by the production method according to any one of claims 1 to 8.
10. A supercapacitor comprising the electrode of claim 9.
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