CN112687833B - Dry method electrode plate preparation method, electrode plate prepared by dry method electrode plate preparation method and application - Google Patents
Dry method electrode plate preparation method, electrode plate prepared by dry method electrode plate preparation method and application Download PDFInfo
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Abstract
The invention provides a dry-method electrode pole piece preparation method, an electrode pole piece prepared by the method and application of the electrode pole piece, wherein the dry-method electrode pole piece preparation method comprises the following steps: mixing raw material powder, heating and fiberizing to obtain pole piece powder, sequentially performing vertical rolling and horizontal rolling on the pole piece powder to obtain a diaphragm, feeding the diaphragm and foil together into a laminating roller, and performing roll forming to obtain the electrode pole piece. The preparation method provided by the invention comprises the steps of dry powder stirring, crushing and fiber crushing and rolling and laminating in sequence, and in the whole preparation process, no slurry solvent is required to be added, no toxic gas is discharged, no coating oven is required, the process equipment is simplified, and the process problem caused by homogenate coating is avoided.
Description
Technical Field
The invention belongs to the technical field of pole piece preparation, and relates to a dry method electrode pole piece preparation method, an electrode pole piece prepared by the method and application of the electrode pole piece.
Background
With global energy shortage and environmental protection awareness increasing, new energy development becomes a current important development direction, and lithium ion batteries become a hotspot of the energy industry by virtue of the advantages of high working voltage, no memory effect, small self-discharge, long cycle life and the like, and are widely applied to mobile electronic products such as mobile phones, computers and the like.
In the production of lithium ion batteries, electrode manufacturing, cell assembly and encapsulation, and battery pre-charging and activation are three main working stages, namely, a front process, a middle process and a back process in the lithium battery population. The electrode is manufactured by producing blood meat of the lithium battery, the electric core is assembled and packaged to form a framework of the lithium battery, the lithium battery is precharged and activated to cast the soul of the lithium battery, and the three parts are compact, dependent and inseparable whole bodies and play an important role in the production process of the lithium battery. Any one of the factors, such as raw materials, cell design, manufacturing equipment and processes, environment, etc., may cause a slight defect in the performance of the battery product.
Electrodes for commercial lithium ion batteries are produced by applying a wet coating to the surface of a current collector. The slurry contains active substances, conductive additives and a binder dissolved in an organic solvent or water, and the specific material type and proportion depend on the system of the binder. For a common electrode system, the electrode drying process is the most energy consuming link in the lithium ion battery production process. On a production line for producing 100 ten thousand batteries every year, the energy consumption of the coating and drying processes of 20.5Ah and 3.7V lithium ion batteries is about 51 percent of the total energy consumption, and most of the energy consumption is used for heating large-scale drying devices and compensating energy loss.
In addition, the coating or slurry casting process commonly used for the electrodes of lithium ion batteries has the following disadvantages: (1) the treatment of harmful substances such as waste gas is required; (2) residual solvent in the coated electrode may reduce the operating life of the battery; (3) the binder dissolved at the surface of the coated active material increases the resistivity of the battery, thereby reducing the energy density and power density of the lithium battery; (4) low electrode compaction density, resulting in low energy density, high resistance and low cycle life; (5) the process cycle is long.
Compared with wet pulping, dry pulping can effectively avoid the problems of processes and equipment such as toxic gas release, oven energy consumption, thickness compaction and the like. The technological process of dry pulping is that active matter, conducting agent and other powder matter are first premixed at certain speed. And after mixing, adding the binder, mixing and stirring, gradually adding the solvent for mixing and dispersing, and finally adding a certain amount of solvent for dilution and adjustment to the viscosity required by coating. In the dry pulping process, the mixing and dispersing process of the lithium ion battery slurry can be divided into a macro mixing process and a micro dispersing process, and the two processes are always accompanied with the whole process of preparing the lithium ion battery slurry.
CN111725477A discloses a method for preparing a dry electrode material of a lithium ion battery, comprising the following steps: growing graphene serving as a conductive agent on the outer layer of the active particles in a chemical vapor deposition or electrostatic spraying mode; or electrostatically spraying graphene oxide on the surface of the active particles, and reducing the graphene oxide into graphene through subsequent reaction with hydrogen; and then coating the polymer binder powder on the outer layers of the active particles and the graphene by an electrostatic spraying method to form a uniformly mixed dry material.
CN106654177A discloses a method for preparing a battery capacitor composite electrode by a dry method, which comprises the following steps: weighing a composite electrode raw material A type active substance, a composite electrode raw material B type active substance, binder dry powder and a conductive agent, fully mixing the composite electrode raw materials, heating to 500-580 ℃ in an inert atmosphere of nitrogen and/or argon, calcining at the high temperature for 2-8 hours, cooling to room temperature, wherein the flow rate of inert gas is 200-280 ml/min, and the heating rate is 4-9 ℃/min; extruding the mixed composite electrode raw material to prepare a dry electrode film; and coating a layer of conductive adhesive with the thickness of 1-10 mu m on the surface of the current collector to obtain a conductive coating, pasting the prepared dry electrode film on the conductive coating, and rolling to obtain the composite electrode of the battery capacitor.
CN109755473A discloses a dry preparation method of a lithium battery electrode, which comprises the steps of uniformly mixing, finely crushing and carrying out multi-pass high-temperature rolling on an electrode composite material consisting of an active material, an additive of a conductive material and a polymer binder to form an electrode film strip; and compounding the electrode film strip on an electrode current collector by high-temperature rolling to obtain a coiled lithium battery electrode, wherein the high-temperature rolling temperature is 100-200 ℃, the electrode current collector is a metal foil strip with an adhesive coating, the electrode current collector comprises a positive electrode and a negative electrode, a collector of the negative electrode is a copper foil, a collector of the positive electrode is an aluminum foil, and the active material, the additive of the conductive material and the polymer binder respectively account for 70-98%, 0-10% and 2-20% of the total mixture.
In summary, in the existing wet coating process, the positive and negative electrode main materials NCM or GR are respectively mixed, dispersed and stirred with the binder, the conductive agent and the aqueous solution or NM solvent to prepare the electrode slurry, the slurry is extruded and sprayed on the copper or aluminum foil to prepare the electrode sheet by an extrusion coating method, and the electrode sheet is rolled to the required thickness by using a cold and hot roll press. However, the process has the problems of process and equipment such as water system slurry viscosity difference I, coating surface density consistency, pole piece corrugation, NMP toxic gas release, oven energy consumption, compaction thickness and the like.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a dry-method electrode piece preparation method, an electrode piece prepared by the dry-method electrode piece preparation method and application of the electrode piece.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a method for preparing a dry electrode pole piece, which comprises the following steps:
the electrode plate is prepared by mixing raw material powder, heating and fiberizing to obtain pole piece powder, sequentially performing vertical rolling and horizontal rolling on the pole piece powder to obtain a diaphragm, feeding the diaphragm and foil together into a laminating roller, and performing roll forming.
The invention provides a preparation method of a dry-method electrode piece, which comprises the steps of sequentially stirring dry powder, crushing and fibering, rolling and attaching, wherein the raw material powder after mixing and stirring is in a micro-expansion state, the micro-expansion state is changed into a fluffy state through heating, and then, fiberization treatment is carried out on the electrode piece powder to change the state of the electrode piece powder from the fluffy state into a spider-web wire-drawing state, the formation of the spider-web wire-drawing state is favorable for subsequent roll forming, and if complete fiberization is not achieved, a diaphragm is easily crushed and cannot be formed in the subsequent roll forming process. The fiberized pole piece powder is sequentially subjected to vertical rolling and horizontal rolling forming, the thickness and the compaction density of the diaphragm can be well controlled by rolling twice and adjusting rolling process parameters, and meanwhile, the previous fiberization process further facilitates the diaphragm forming. In the preparation method provided by the invention, no slurry solvent is required to be added, no toxic gas is discharged, no coating oven is used, the process equipment is simplified, and the process problem caused by homogenate coating is avoided.
As a preferable embodiment of the present invention, the raw material powder includes an active material, a conductive agent, and a binder.
Preferably, the active materials are divided into a positive electrode active material and a negative electrode active material.
Preferably, the positive electrode active material includes NCM and/or LFP.
Preferably, the negative active material includes graphite and/or silicon carbon.
Preferably, the conductive agent comprises one or a combination of at least two of SP, ECP, CNT, or VGCF.
Preferably, the binder comprises one or a combination of at least two of PTFE, CMC or PVDF.
Preferably, the mass ratio of the active material, the conductive agent and the binder is (70-90): (5-10): 3-10), and may be, for example, 70:5:3, 75:7:5, 80:8:6, 85:9:8 or 90:10:10, but is not limited to the recited values, and other values not recited within the range of values are also applicable.
In a preferred embodiment of the present invention, the stirring rate in the mixing process is 600 to 1300rpm/min, such as 600rpm/min, 650rpm/min, 700rpm/min, 750rpm/min, 800rpm/min, 850rpm/min, 900rpm/min, 950rpm/min, 1000rpm/min, 1050rpm/min, 1100rpm/min, 1150rpm/min, 1200rpm/min, 1250rpm/min or 1300rpm/min, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.
Preferably, the mixing time is 40-60 min, such as 40min, 42min, 44min, 46min, 48min, 50min, 52min, 54min, 56min, 58min or 60min, but is not limited to the values listed, and other values not listed in the range are also applicable.
Preferably, the bulk density of the mixed raw material powder is 0.6 to 0.85g/cm3For example, it may be 0.6g/cm3、0.62g/cm3、0.64g/cm3、0.66g/cm3、0.68g/cm3、0.7g/cm3、0.72g/cm3、0.72g/cm3、0.74g/cm3、0.76g/cm3、0.78g/cm3、0.8g/cm3、0.82g/cm3、0.84g/cm3Or 0.85g/cm3However, the numerical values recited are not intended to be limiting, and other numerical values not recited within the numerical range may be equally applicable.
As a preferred technical solution of the present invention, the heating process is performed in an oven.
Preferably, the heating temperature is 40 to 50 ℃, for example, 40 ℃, 41 ℃, 42 ℃, 43 ℃, 44 ℃, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃ or 50 ℃, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
Preferably, the heating time is 10-20 min, such as 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20min, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
As a preferable technical scheme of the invention, the fiberization process adopts jet milling.
Preferably, the air pressure applied in the air flow crushing process is 0.2-0.8 Mpa, such as 0.2Mpa, 0.25Mpa, 0.3Mpa, 0.35Mpa, 0.4Mpa, 0.45Mpa, 0.5Mpa, 0.55Mpa, 0.6Mpa, 0.65Mpa, 0.7Mpa, 0.75Mpa or 0.8Mpa, but not limited to the recited values, and other values in the range of the recited values are also applicable.
Preferably, the volume density of the fiberized pole piece powder obtained after jet milling is 0.3-0.5 g/cm3For example, it may be 0.3g/cm3、0.32g/cm3、0.34g/cm3、0.36g/cm3、0.38g/cm3、0.4g/cm3、0.42g/cm3、0.44g/cm3、0.46g/cm3Or 0.5g/cm3However, the numerical values recited are not intended to be limiting, and other numerical values not recited within the numerical range may be equally applicable.
As a preferred technical scheme, the vertical rolling process is carried out in a hot roller press, the hot roller press comprises two axially horizontal hot pressing rollers which are arranged side by side, and the pole piece powder penetrates through a gap between the two hot pressing rollers from top to bottom and is formed under the extrusion action of the two hot pressing rollers;
preferably, the pressure of the vertical rolling is 0 to 75t, for example, 5t, 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t, 55t, 60t, 65t, 70t or 75t, but is not limited to the listed values, and other values not listed in the range of the values are also applicable.
Preferably, the temperature of the vertical rolling is 110 to 180 ℃, for example, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃ or 180 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the gap width between the two hot press rolls is 0 to 2 μm, and may be, for example, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2.0 μm, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
As a preferable technical scheme, the horizontal rolling process is carried out in a horizontal rolling machine, the horizontal rolling machine comprises two horizontal rollers which are arranged side by side and are in horizontal axial direction, and pole piece powder after vertical rolling passes through a gap between the two horizontal rollers along the horizontal direction and is molded under the extrusion action of the two horizontal rollers to obtain the membrane.
Preferably, the pressure of the horizontal rolling is 0 to 55t, for example, 5t, 10t, 15t, 20t, 25t, 30t, 35t, 40t, 45t, 50t or 55t, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
Preferably, the gap width between the two horizontal rolls is 0 to 2 μm, and may be, for example, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2.0 μm, but is not limited to the values listed, and other values not listed in the range of values are also applicable.
As a preferred technical scheme of the invention, the active material is a positive active material, the prepared membrane is a positive membrane, the positive membrane and the aluminum foil enter a laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller;
preferably, the active material is a negative electrode active material, the prepared membrane is a negative electrode membrane, the negative electrode membrane and the copper foil enter the laminating roller together, and the negative electrode membrane is laminated on the surface of the copper foil under the extrusion action of the laminating roller.
In a second aspect, the invention provides an electrode plate prepared by the preparation method of the first aspect.
Preferably, the thickness of the electrode plate is 300-1000 μm, for example, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1000 μm, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
In a third aspect, the present invention provides a battery cell, which includes the electrode sheet of the second aspect.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a preparation method of a dry-method electrode pole piece, which comprises the steps of sequentially stirring dry powder, crushing and fibering, rolling and attaching, wherein the raw material powder after mixing and stirring is in a micro-expansion state, the micro-expansion state is converted into a fluffy state through heating, and then the pole piece powder is fiberized after airflow crushing, the state of the pole piece powder is converted into a cobweb wire drawing state from the fluffy state, the cobweb wire drawing state is formed to be beneficial to subsequent roll forming, and if the complete fiberization is not achieved, the diaphragm is easily crushed and cannot be formed in the subsequent roll forming process. The fiberized pole piece powder is sequentially subjected to vertical rolling and horizontal rolling forming, the thickness and the compaction density of the diaphragm can be well controlled by rolling twice and adjusting rolling process parameters, and meanwhile, the previous fiberization process further facilitates the diaphragm forming. In the preparation method provided by the invention, no slurry solvent is required to be added, no toxic gas is discharged, and no coating oven is provided, so that the process equipment is simplified, and the process problem caused by homogenate coating is avoided.
Drawings
FIG. 1 is an electron micrograph of a positive electrode plate prepared in example 1 of the present invention;
FIG. 2 is an electron micrograph of a positive electrode sheet prepared in comparative example 4 of the present invention;
fig. 3 is a process flow diagram provided in example 1 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Example 1
The embodiment provides a method for preparing a dry electrode pole piece, and the preparation method is shown in fig. 3 and comprises the following steps:
(1) adding NCM, SP and PTFE into a stirrer according to the mass ratio of 70:5:3, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 600rpm/min, the stirring time is 60min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.6g/cm3；
(2) Conveying the pole piece powder into a drying oven at 40 ℃ for heat preservation for 10min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then transferring the pole piece powder in a fluffy state into a jet mill, wherein the pressure of the air flow is 0.2Mpa, the pole piece powder is changed from the fluffy state into a spider-web wire drawing state under the impact action of the air flow, and the volume density of the pole piece powder is 0.3g/cm3；
(4) Vertically rolling the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot press rollers from top to bottom, and is formed under the extrusion action of the two hot press rollers, the pressure of vertical rolling is 5t, the temperature of vertical rolling is 180 ℃, and the width of the gap between the two hot press rollers is 0.5 mu m;
(5) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a positive pole diaphragm, wherein the pressure of the horizontal rolling is 5t, and the width of the gap between the two horizontal rollers is 0.5 mu m;
(6) and the positive membrane and the aluminum foil enter the laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller to obtain the positive pole piece.
The prepared positive pole piece has a flat surface and no wrinkles, and the thickness of the positive pole piece can reach 300 mu m. The microscopic morphology is shown in fig. 1, and it can be seen from fig. 1 that the pole piece powder is in a spider-web wire-drawing state, and the adhesive and the material are in point contact, obviously, the adhesive dosage of the point contact is correspondingly reduced.
Example 2
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) LFP, ECP and CMC are added into a stirrer according to the mass ratio of 75:6:5 and stirred to obtain pole piece powder, the stirring speed of the stirrer is 740rpm/min, the stirring time is 56min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the pole piece powder is 0.68g/cm3；
(2) Sending the pole piece powder into a 42 ℃ oven for heat preservation for 12min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then transferring the pole piece powder in a fluffy state into an airflow pulverizer, wherein the airflow pressure is 0.32Mpa, the pole piece powder is converted into a cobweb wire-drawing state from the fluffy state under the impact action of airflow, and the volume density of the pole piece powder is 0.35g/cm3；
(4) Vertically rolling the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot press rollers from top to bottom, and is formed under the extrusion action of the two hot press rollers, the pressure of vertical rolling is 20t, the temperature of vertical rolling is 166 ℃, and the width of the gap between the two hot press rollers is 0.8 mu m;
(5) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a positive pole diaphragm, wherein the pressure of the horizontal rolling is 15t, and the width of the gap between the two horizontal rollers is 0.8 mu m;
(6) and the positive membrane and the aluminum foil enter the laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller to obtain the positive pole piece.
The prepared positive pole piece has a flat surface and no wrinkles, and the thickness of the positive pole piece can reach 410 mu m.
Example 3
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding NCM, CNT and PVDF into a stirrer according to the mass ratio of 80:07:06, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 880rpm/min, the stirring time is 52min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.72g/cm3；
(2) Feeding the pole piece powder into a drying oven at 44 ℃ for heat preservation for 14min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then transferring the pole piece powder in a fluffy state into an airflow pulverizer, wherein the airflow pressure is 0.44Mpa, the pole piece powder is converted into a cobweb wire-drawing state from the fluffy state under the impact action of airflow, and the bulk density of the pole piece powder is 0.39g/cm3；
(4) Carrying out vertical rolling on the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot-pressing rollers from top to bottom, and is formed under the extrusion action of the two hot-pressing rollers, the pressure of the vertical rolling is 35t, the temperature of the vertical rolling is 152 ℃, and the width of the gap between the two hot-pressing rollers is 1.2 mu m;
(5) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a positive pole diaphragm, wherein the pressure of the horizontal rolling is 25t, and the width of the gap between the two horizontal rollers is 1.2 mu m;
(6) and the positive membrane and the aluminum foil enter the laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller to obtain the positive pole piece.
The prepared positive pole piece has a flat surface and no wrinkles, and the thickness of the positive pole piece can reach 550 mu m.
Example 4
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding graphite, SP and PTFE into a stirrer according to a mass ratio of 83:8:7, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 1020rpm/min, the stirring time is 48min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.74g/cm3；
(2) Conveying the pole piece powder into a drying oven at 46 ℃ for heat preservation for 16min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then transferring the pole piece powder in a fluffy state into an airflow pulverizer, wherein the airflow pressure is 0.56Mpa, the pole piece powder is converted into a cobweb wire-drawing state from the fluffy state under the impact action of airflow, and the bulk density of the pole piece powder is 0.41g/cm3；
(4) Vertically rolling the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot press rollers from top to bottom, and is formed under the extrusion action of the two hot press rollers, the pressure of vertical rolling is 50t, the temperature of vertical rolling is 138 ℃, and the width of the gap between the two hot press rollers is 1.5 mu m;
(5) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a negative pole diaphragm, wherein the pressure of the horizontal rolling is 35t, and the width of the gap between the two horizontal rollers is 1.5 mu m;
(6) and the negative electrode diaphragm and the copper foil enter the laminating roller together, and the positive electrode diaphragm is laminated on the surface of the copper foil under the extrusion action of the laminating roller to obtain a negative electrode pole piece.
The prepared positive pole piece has a smooth surface and no wrinkles, and the thickness of the positive pole piece can reach 640 mu m.
Example 5
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding silicon carbon, ECP and CMC into a stirrer according to a mass ratio of 85:9:8, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 1160rpm/min, the stirring time is 44min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.78g/cm3；
(2) Conveying the pole piece powder into a drying oven at 48 ℃ for heat preservation for 18min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then, the pole piece powder in a fluffy state is transferred into a jet mill, the airflow pressure is 0.68Mpa, the pole piece powder is changed into a cobweb wire drawing state from the fluffy state under the impact action of the airflow, and the volume density of the pole piece powder is 0.47g/cm3；
(4) Carrying out vertical rolling on the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot pressing rollers from top to bottom, and is formed under the extrusion action of the two hot pressing rollers, the pressure of the vertical rolling is 65t, the temperature of the vertical rolling is 124 ℃, and the width of the gap between the two hot pressing rollers is 1.8 mu m;
(5) carrying out horizontal rolling on the pole piece powder after vertical rolling, enabling the pole piece powder to pass through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a negative electrode diaphragm, wherein the pressure of the horizontal rolling is 45t, and the width of the gap between the two horizontal rollers is 1.8 mu m;
(6) and (3) the negative electrode diaphragm and the copper foil enter a laminating roller together, and the positive electrode diaphragm is laminated on the surface of the copper foil under the extrusion action of the laminating roller to obtain a negative electrode pole piece.
The prepared positive pole piece has a flat surface and no wrinkles, and the thickness of the positive pole piece can reach 880 mu m.
Example 6
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding graphite, VGCF and PVDF into a stirrer according to a mass ratio of 90:10:10, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 1300rpm/min, the stirring time is 40min, and the mixed pole piece powder is in a micro-expansion state and has a volumeThe density is 0.85g/cm3；
(2) Sending the pole piece powder into a drying oven at 50 ℃ for heat preservation for 20min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then, the pole piece powder in a fluffy state is transferred into a jet mill, the airflow pressure is 0.8Mpa, the pole piece powder is changed into a cobweb wire drawing state from the fluffy state under the impact action of the airflow, and the volume density of the pole piece powder is 0.5g/cm3；
(4) Carrying out vertical rolling on the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot pressing rollers from top to bottom, and is formed under the extrusion action of the two hot pressing rollers, the pressure of the vertical rolling is 75t, the temperature of the vertical rolling is 110 ℃, and the width of the gap between the two hot pressing rollers is 2 mu m;
(5) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a negative pole diaphragm, wherein the pressure of the horizontal rolling is 55t, and the width of the gap between the two horizontal rollers is 2 mu m;
(6) and the negative electrode diaphragm and the copper foil enter the laminating roller together, and the positive electrode diaphragm is laminated on the surface of the copper foil under the extrusion action of the laminating roller to obtain a negative electrode pole piece.
The prepared positive pole piece has a flat surface and no wrinkles, and the thickness of the positive pole piece can reach 1000 mu m.
Comparative example 1
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding NCM, SP and PTFE into a stirrer according to the mass ratio of 70:5:3, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 600rpm/min, the stirring time is 60min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.6g/cm3；
(2) Transferring the mixed pole piece powder into an airflow pulverizer, wherein the airflow pressure is 0.2Mpa, the pole piece powder is converted into a fluffy state from a micro-expansion state under the impact action of the airflow, and the bulk density of the pole piece powder is 0.53g/cm3；
(3) Vertically rolling the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot press rollers from top to bottom, and is formed under the extrusion action of the two hot press rollers, the pressure of vertical rolling is 5t, the temperature of vertical rolling is 180 ℃, and the width of the gap between the two hot press rollers is 0.5 mu m;
(4) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a positive pole diaphragm, wherein the pressure of the horizontal rolling is 5t, and the width of the gap between the two horizontal rollers is 0.5 mu m;
(5) and the positive membrane and the aluminum foil enter the laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller to obtain the positive pole piece.
The prepared positive pole piece cannot be molded at one time, because the surface temperature of powder is reduced, and the sufficient bulkiness cannot be maintained, so that the fibrosis is insufficient.
Comparative example 2
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding NCM, SP and PTFE into a stirrer according to the mass ratio of 70:5:3, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 600rpm/min, the stirring time is 60min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.6g/cm3；
(2) Conveying the pole piece powder into a drying oven at 40 ℃ for heat preservation for 10min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) vertically rolling the pole piece powder, wherein the pole piece powder penetrates through a gap between two hot press rollers from top to bottom, and is formed under the extrusion action of the two hot press rollers, the pressure of vertical rolling is 5t, the temperature of vertical rolling is 180 ℃, and the width of the gap between the two hot press rollers is 0.5 mu m;
(4) horizontally rolling the pole piece powder after vertical rolling, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a positive pole diaphragm, wherein the pressure of the horizontal rolling is 5t, and the width of the gap between the two horizontal rollers is 0.5 mu m;
(5) and the positive membrane and the aluminum foil enter a laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller to obtain the positive pole piece.
The prepared positive pole piece can not be molded, because the powder is not fiberized, the subsequent roll forming is influenced.
Comparative example 3
The embodiment provides a preparation method of a dry-method electrode piece, which comprises the following steps:
(1) adding NCM, SP and PTFE into a stirrer according to the mass ratio of 70:5:3, stirring to obtain pole piece powder, wherein the stirring speed of the stirrer is 600rpm/min, the stirring time is 60min, the mixed pole piece powder is in a micro-expansion state, and the volume density of the mixed pole piece powder is 0.6g/cm3；
(2) Conveying the pole piece powder into a drying oven at 40 ℃ for heat preservation for 10min, so that the pole piece powder in a micro-expansion state is converted into a fluffy state;
(3) then transferring the pole piece powder in a fluffy state into a jet mill, wherein the pressure of the air flow is 0.2Mpa, the pole piece powder is changed from the fluffy state into a spider-web wire drawing state under the impact action of the air flow, and the volume density of the pole piece powder is 0.3g/cm3；
(4) Horizontally rolling the pole piece powder, enabling the pole piece powder to penetrate through a gap between two horizontal rollers along the horizontal direction, and forming under the extrusion action of the two horizontal rollers to obtain a positive pole diaphragm, wherein the pressure of the horizontal rolling is 5t, and the width of the gap between the two horizontal rollers is 0.5 mu m;
(5) and the positive membrane and the aluminum foil enter the laminating roller together, and the positive membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller to obtain the positive pole piece.
The prepared positive pole piece can be molded without wrinkles, but the thickness cannot be controlled, because the horizontal rolling is insufficient, and the secondary rolling is needed.
Comparative example 4
The embodiment provides a preparation method of a wet electrode pole piece, which comprises the following steps:
(1) uniformly mixing a lithium cobaltate positive electrode active substance, graphene, PVDF and NMP to obtain positive electrode slurry; the mass ratio of the lithium cobaltate positive electrode active substance to the graphene to the PVDF is 95.8:2.2: 2; the mass percentage of the total mass of the lithium cobaltate positive electrode active substance, the graphene and the PVDF to the NMP solvent is 31: 69;
(2) coating the positive electrode slurry on the surface of the aluminum foil, and drying and rolling to obtain the positive electrode piece.
The surface of the prepared positive pole piece material has no wrinkles, but the thickness of the positive pole piece material cannot reach the lower limit of the thickness range defined by the application, and the thickness of the positive pole piece material is only 280 micrometers. The microscopic morphology is shown in fig. 2, the magnification of fig. 2 is the same as that of fig. 1, and it can be seen from fig. 2 that the binder of the electrode wraps the whole surface of the material, and obviously, the amount of the binder is increased correspondingly.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (14)
1. A preparation method of a dry electrode pole piece with the thickness of 300-1000 mu m is characterized by comprising the following steps:
mixing raw material powder, heating and fiberizing to obtain pole piece powder, wherein the stirring speed in the mixing process is 600-1300 rpm/min, the mixing time is 40-60 min, and the bulk density of the mixed raw material powder is 0.6-0.85 g/cm3The heating temperature is 40-50 ℃, the heating time is 10-20 min, the pole piece powder is sequentially subjected to vertical rolling and horizontal rolling to obtain a membrane, the membrane and the foil enter a laminating roller together, and the electrode pole piece is obtained through roll forming;
wherein the fiberization process adopts jet milling, and the jet milling process adoptsThe airflow pressure is 0.2-0.8 Mpa, and the volume density of the fiberized pole piece powder obtained after airflow pulverization is 0.5-0.3 g/cm3；
The vertical rolling process is carried out in a hot roller press, the hot roller press comprises two axially horizontal hot pressing rollers which are arranged side by side, and the pole piece powder penetrates through a gap between the two hot pressing rollers from top to bottom and is formed under the extrusion action of the two hot pressing rollers;
the pressure of the vertical rolling is 5-75 t;
the temperature of the vertical rolling is 110-180 ℃;
the horizontal rolling process is carried out in a horizontal rolling machine, the horizontal rolling machine comprises two horizontal rollers which are arranged side by side and axially horizontal, and the pole piece powder after vertical rolling passes through a gap between the two horizontal rollers along the horizontal direction and is molded under the extrusion action of the two horizontal rollers to obtain a diaphragm;
the pressure of the horizontal rolling is 5-55 t.
2. The method according to claim 1, wherein the raw material powder comprises an active material, a conductive agent and a binder.
3. The method according to claim 2, wherein the active materials are divided into a positive electrode active material and a negative electrode active material.
4. The method according to claim 3, wherein the positive electrode active material comprises NCM and/or LFP.
5. The method according to claim 3, wherein the negative electrode active material comprises graphite and/or silicon carbon.
6. The method of claim 2, wherein the conductive agent comprises one or a combination of at least two of SP, ECP, CNT, or VGCF.
7. The method of claim 2, wherein the binder comprises one or a combination of at least two of PTFE, CMC, or PVDF.
8. The method according to claim 2, wherein the mass ratio of the active material, the conductive agent and the binder is (70-90): 5-10): 3-10.
9. The method of claim 1, wherein the heating is performed in an oven.
10. The method according to claim 1, wherein a gap width between the two heat and pressure rollers is 0 to 2 μm.
11. The preparation method according to claim 2, wherein the active material is a positive electrode active material, the prepared membrane is a positive electrode membrane, the positive electrode membrane and the aluminum foil enter the laminating roller together, and the positive electrode membrane is laminated on the surface of the aluminum foil under the extrusion action of the laminating roller.
12. The preparation method according to claim 2, wherein the active material is a negative electrode active material, the prepared membrane is a negative electrode membrane, the negative electrode membrane and the copper foil enter the laminating roller together, and the negative electrode membrane is laminated on the surface of the copper foil under the extrusion action of the laminating roller.
13. The electrode piece prepared by the preparation method of any one of claims 1 to 12, wherein the thickness of the electrode piece is 300-1000 μm.
14. A cell comprising the electrode sheet of claim 13.
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| CN114039021B (en) * | 2021-09-26 | 2023-06-16 | 三一技术装备有限公司 | Dry electrode film preparation device and battery production line |
| CN114122309B (en) * | 2021-10-14 | 2023-11-17 | 三一技术装备有限公司 | Dry electrode preparation method and battery production line |
| CN114014383A (en) * | 2021-11-05 | 2022-02-08 | 广东佳纳能源科技有限公司 | High-tap-density positive electrode material and preparation method of positive electrode piece |
| CN114243104A (en) * | 2021-12-20 | 2022-03-25 | 惠州亿纬锂能股份有限公司 | Flexible electrolyte membrane, battery and preparation method |
| CN114759158A (en) * | 2022-04-13 | 2022-07-15 | 合肥国轩高科动力能源有限公司 | Preparation method of dry-method electrode pole piece and secondary battery |
| CN114725320B (en) * | 2022-04-15 | 2023-06-20 | 三一技术装备有限公司 | Preparation method of dry pole piece |
| CN114759167A (en) * | 2022-04-20 | 2022-07-15 | 江西安驰新能源科技有限公司 | Manufacturing process of lithium battery positive plate |
| CN114784219A (en) * | 2022-04-26 | 2022-07-22 | 江西安驰新能源科技有限公司 | Manufacturing process of lithium battery negative plate |
| CN114914405A (en) * | 2022-05-25 | 2022-08-16 | 楚能新能源股份有限公司 | Method for preparing battery pole piece by dry method |
| CN115084445A (en) * | 2022-06-09 | 2022-09-20 | 广东嘉拓自动化技术有限公司 | Negative electrode dry film forming preparation process and negative electrode dry film |
| CN114824173B (en) * | 2022-06-10 | 2024-02-09 | 蜂巢能源科技(无锡)有限公司 | Dry electrode plate, preparation method thereof and application thereof in energy storage battery |
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