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CN114068857A - Preparation method and application of electrode slice - Google Patents

Preparation method and application of electrode slice Download PDF

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Publication number
CN114068857A
CN114068857A CN202111276543.2A CN202111276543A CN114068857A CN 114068857 A CN114068857 A CN 114068857A CN 202111276543 A CN202111276543 A CN 202111276543A CN 114068857 A CN114068857 A CN 114068857A
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electrode
powder
electrode material
particle size
preparation
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王志斌
徐雄文
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Hunan Lifang New Energy Science and Technology Co Ltd
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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
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • H01M4/04—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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • Y02E60/10—Energy storage using batteries

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  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a preparation method and application of an electrode plate, which comprises the following steps: s1, mixing the first electrode material with a conductive agent and a binder to prepare powder A; s2, mixing a second electrode material with a conductive agent and a binder to prepare powder B, wherein the second electrode material and the first electrode material are the same material, and the particle size D50 of the second electrode material is larger than the particle size D50 of the first electrode material; s3, spreading the powder A on at least one surface of a current collector, spreading the powder B on the surface of the powder A away from the current collector, and compounding by hot rolling to finish the preparation of the electrode plate. Compared with the prior art, the invention adopts the dry mixing hot rolling technology to prepare the multilayer electrode slice consisting of different particle size gradients, and solves the problems of easy cracking and poor lithium conducting performance of the existing thick electrode slice preparation method.

Description

Preparation method and application of electrode slice
Technical Field
The invention relates to the field of secondary batteries, in particular to a preparation method and application of an electrode plate.
Background
In order to deal with global energy crisis, lithium ion batteries are used as efficient and green battery technologies in many fields such as computers and electric vehicles. With the gradual expansion of market demands, new requirements are also put on the energy density of lithium ion batteries. On the premise that a positive electrode material and a negative electrode material with larger specific capacity are not found, the main means for improving the energy density of the single battery is to improve the specific gravity of an active material in a battery material (or reduce the mass ratio of an inactive material). At present, the method of using thinner separators and current collectors to reduce the mass fraction of inactive materials has not been able to do so because thinner separators and current collectors have reached the technical bottleneck. Therefore, the application of thick pole pieces to batteries to increase energy density is one of the most important methods. However, the thicker the electrode sheet, the more difficult the coating, the more the internal resistance of the battery, and the inferior rate and cycle performance.
The prior proposal discloses a thick electrode with good electrochemical performance and a preparation method thereof, which realizes the gradient distribution of porosity and conductivity by a way of secondary or multiple slurry coating, and the porosity from an inner-layer membrane close to a current collector to an outer-layer membrane far away from the current collector is increased in steps and the conductivity is reduced in sequence, thereby solving the problems of large internal resistance and serious polarization of the thick electrode. However, the slurry coating method will cause material dissolution and even porosity change in the second and later coating processes, and finally affect the electrolyte wetting and ion conductivity.
In addition, the scheme discloses a high-rate thick electrode and a preparation method and application thereof, wherein a plurality of single-layer electrode membranes with different porosities are stacked and pressed to form a composite electrode membrane, and the composite electrode membrane has the characteristic that the porosities are sequentially reduced from outside (far away from a current collector) to inside (close to the current collector), so that the ionic conductivity of the thick electrode plate is improved. However, in the composite electrode film formed by the conventional pressing method, the bonding force between every two layers of electrode films is poor, so that stable and effective connection is difficult to form, and the expansion stress of the electrodes easily causes stripping of the pole pieces in the charging and discharging processes, thereby influencing the service life of the battery. In addition, the manufacturing process of the composite electrode film is complicated, and the interface contact between the films of each single layer is not tight, so that the problems of large interface internal resistance and poor conductivity are easily caused.
In view of the above, it is necessary to provide a technical solution to the above problems.
Disclosure of Invention
One of the objects of the present invention is: the preparation method of the electrode plate is provided to solve the problems of easy cracking and poor lithium conducting performance of the conventional thick electrode plate, so that the purposes of improving the dynamic performance and energy density of the lithium battery are achieved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of an electrode slice comprises the following steps:
s1, mixing the first electrode material with a conductive agent and a binder to prepare powder A;
s2, mixing a second electrode material with a conductive agent and a binder to prepare powder B, wherein the second electrode material and the first electrode material are the same material, and the particle size D50 of the second electrode material is larger than the particle size D50 of the first electrode material;
s3, spreading the powder A on at least one surface of a current collector, spreading the powder B on the surface of the powder A away from the current collector, and compounding by hot rolling to finish the preparation of the electrode plate.
Preferably, the first electrode material and the second electrode material are both positive electrode materials, the particle size D50 of the first electrode material is less than or equal to 9 μm, and the particle size D50 of the second electrode material is greater than 9 μm.
Preferably, the mass ratio of the powder A to the powder B is 1: (1.1-2).
Preferably, the first electrode material and the second electrode material are both negative electrode materials, the particle size D50 of the first electrode material is less than or equal to 12 μm, and the particle size D50 of the second electrode material is greater than 12 μm.
Preferably, the mass ratio of the powder A to the powder B is 1: (2-10).
Preferably, in step S1, the first electrode material, the conductive agent and the binder are mixed by a V-type mixing device; in step S2, the second electrode material, the conductive agent, and the binder are mixed by a V-type mixing device.
Preferably, in step S3, the hot rolling conditions are: the temperature is 30-300 ℃, and the pressure is 5-25 MPa.
Preferably, the binder is at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene and styrene butadiene rubber; the conductive agent is at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube and graphene.
Another object of the present invention is to provide an electrode sheet produced by the method for producing an electrode sheet according to any one of the above aspects.
The invention also provides a secondary battery, which comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, wherein the positive plate and/or the negative plate is the electrode plate.
Compared with the prior art, the invention has the beneficial effects that: according to the preparation method of the electrode slice, the multilayer electrode slice composed of different particle size gradients is prepared by adopting a dry mixing hot rolling technology, and the formed thick electrode slice has good cohesive force and good dynamic performance, so that the problems of easiness in cracking and poor lithium conducting performance existing in the conventional preparation method of the thick electrode slice are solved.
Drawings
Fig. 1 is a schematic structural view of an electrode sheet according to the present invention.
FIG. 2 is a graph showing the cycle performance test of example 13 of the present invention and comparative example 1.
Detailed Description
The invention provides a preparation method of an electrode plate, which comprises the following steps:
s1, mixing the first electrode material with a conductive agent and a binder to prepare powder A;
s2, mixing a second electrode material with a conductive agent and a binder to prepare powder B, wherein the second electrode material and the first electrode material are the same material, and the particle size D50 of the second electrode material is larger than the particle size D50 of the first electrode material;
s3, spreading the powder A on at least one surface of a current collector, spreading the powder B on the surface of the powder A away from the current collector, and compounding by hot rolling to finish the preparation of the electrode plate.
The current preparation method of the multilayer electrode plate comprises a secondary wet coating method and a composite membrane method. However, the method has some disadvantages, which greatly limits the application of the multilayer electrode plate, resulting in the application of the high energy density battery being greatly limited. The secondary wet coating has the disadvantages that the material is easy to dissolve out during the secondary wet coating so as to influence the material performance, and the method has complex process, long time consumption and large energy consumption; the composite membrane method is mainly characterized in that a plurality of single-layer membranes are respectively subjected to conventional rolling to form the composite membrane, but the membrane formed by the method has high interface internal resistance and poor binding force, and the service life of a battery is influenced.
According to the preparation method of the multilayer electrode plate, thermoplasticity of the binder is utilized, powder is distributed according to different particle size gradients, and the thick electrode plate formed in the way has good binding power and good dynamic performance by adopting dry mixing hot roller pressing.
The active electrode material of the powder A close to one surface of the current collector is a small-particle-size electrode material, and compared with a large-particle-size electrode material, the active electrode material has better conductivity and dynamic performance due to close contact among small-particle-size particles, but does not have the advantage of high capacity; the powder B is arranged on the surface of the powder A far away from the current collector, the active electrode material is a large-particle-size electrode material, and compared with a small-particle-size electrode material, the active electrode material has the advantages of high capacity due to high material crystallinity and complete crystal form. Compared with the electrode plate with mixed use of the large and small particle sizes, the electrode plate has better conductivity and more advantages in dynamic performance in the active layer close to the current collector side, and finally achieves more beneficial effect on the thick electrode plate. In general, in an electrode sheet using a mixture of a large particle size and a small particle size, a high energy density effect is achieved by filling up pores between large particle sizes with a small particle size, but the conductivity of an active layer near a current collector is not improved, and the problem of poor conductivity of a thick electrode sheet cannot be solved.
In some embodiments, the first electrode material and the second electrode material are both positive electrode materials, the particle size D50 of the first electrode material is ≦ 9 μm, and the particle size D50 of the second electrode material is >9 μm.
When the electrode material is a positive electrode material, the mass ratio of the powder A to the powder B is 1: (1.1-2). Preferably, the mass ratio of the powder A to the powder B is 1: (1.25-1.5).
Wherein the positive electrode material may be of a chemical formula including but not limited to LiaNixCoyMzO2-bNb(wherein a is more than or equal to 0.95 and less than or equal to 1.2, x>0, y is more than or equal to 0, z is more than or equal to 0, and x + y + z is 1,0 is more than or equal to b and less than or equal to 1, M is selected from one or more of Mn and Al, N is selected from one or more of F, P and S), and the positive electrode active material can also be selected from one or more of LiCoO (lithium LiCoO), but not limited to2、LiNiO2、LiVO2、LiCrO2、LiMn2O4、LiCoMnO4、Li2NiMn3O8、LiNi0.5Mn1.5O4、LiCoPO4、LiMnPO4、LiFePO4、LiNiPO4、LiCoFSO4、CuS2、FeS2、MoS2、NiS、TiS2And the like.
In some embodiments, the first electrode material and the second electrode material are both negative electrode materials, the particle size D50 of the first electrode material is less than or equal to 12 μm, and the particle size D50 of the second electrode material is greater than 12 μm.
When the electrode material is a negative electrode material, the mass ratio of the powder A to the powder B is 1: (2-10). More preferably, the mass ratio of the powder A to the powder B is 1: (3-5).
Wherein, the negative electrode material can be at least one of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium; the graphite can be one or more selected from artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy.
Under the condition that the total thickness of the pole piece is constant, if the active layer obtained from the powder A is thick, the active layer obtained from the powder B is thin, so that the energy density of the thick pole piece is relatively low, and the advantage of high energy density of the thick pole piece cannot be highlighted. If the active layer obtained from powder A is thin, the active layer obtained from powder B is thick, and the energy density of the final thick pole piece is high. Specifically, the thickness can be adjusted by regulating and controlling the quality of the powder A and the powder B, so that various performances of the lithium ion battery are improved to a greater extent.
Preferably, for the positive electrode material, when the thickness of the active layer A formed by the powder material A is 80-100 μm, the thickness of the active layer B formed by the powder material B is 105-120 μm; in the negative electrode material, the thickness of the active layer A formed of the powder A is 50 to 70 μm, and the thickness of the active layer B formed of the powder B is 150 to 210 μm. More preferably, for the positive electrode material, when the thickness of the active layer A formed of the powder A is 88 μm, the thickness of the active layer B formed of the powder B is 115 μm; in the case of the negative electrode material, when the thickness of the active layer A formed of the powder A is 60 μm and the thickness of the active layer B formed of the powder B is 183 μm, the electrochemical performance of the obtained lithium ion battery is further improved.
Preferably, in step S1, the first electrode material, the conductive agent and the binder are mixed by a V-type mixing device; in step S2, the second electrode material, the conductive agent, and the binder are mixed by a V-type mixing device.
Preferably, in step S3, the hot rolling conditions are: the temperature is 30-300 ℃, and the pressure is 5-25 MPa. Specifically, the hot rolling temperature can be 30-80 ℃, 80-100 ℃, 100-150 ℃, 150-200 ℃, 200-250 ℃ and 250-300 ℃; the pressure can be 5-8 MPa, 8-10 MPa, 10-15 MPa, 15-18 MPa, 18-20 MPa, 20-25 MPa. The powder A and the powder B can be well pressed at a proper hot rolling temperature, and not only can be well bonded, so that the problems of large internal resistance and poor bonding force of a contact interface are avoided, and the preparation process is simple and low in energy consumption.
Preferably, the binder is at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene and styrene butadiene rubber; the conductive agent is at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube and graphene.
The second aspect of the present invention is to provide an electrode sheet prepared by the method for preparing an electrode sheet according to any one of the above embodiments. As shown in fig. 1.
The third aspect of the invention provides a secondary battery, which comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, wherein the positive plate and/or the negative plate is the electrode plate.
In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantages will be described in further detail below with reference to the following detailed description and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
Example 1
A preparation method of a positive plate comprises the following steps:
s1, uniformly mixing small-particle-size lithium cobaltate (D50 is 8 mu m), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder A;
s2, uniformly mixing large-particle-size lithium cobaltate (D50 is 14 microns), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder B;
s3, spreading the powder A on at least one surface of an aluminum foil, spreading the powder B on the surface of the powder A far away from the aluminum foil, wherein the mass ratio of the powder A to the powder B is 4:5, and the single-side coating surface density is 40.0mg/cm2(ii) a Then compounding by hot rolling at 100 ℃ and 10 MPa; the thickness of the obtained active layer A was 88 μm, and the thickness of the obtained active layer B was 115 μm, to complete the preparation of the positive electrode sheet.
The positive plate is used in a lithium ion battery, the negative electrode is made of conventional graphite materials, the lithium ion battery is formed by winding, and electrolyte is injected to obtain the lithium ion battery.
Example 2
Different from example 1, the temperature of the hot rolling was 30 ℃.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
Unlike example 1, the temperature of the hot rolling was 200 ℃.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
Different from example 1, the temperature of hot rolling was 300 ℃.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
Different from example 1 in the mass ratio of powder A to powder B, which was 1: 2.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
Different from example 1 in the mass ratio of powder A to powder B, 5: 4.
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
A preparation method of a negative plate comprises the following steps:
s1, uniformly mixing small-particle-size graphite (D50 is 10 mu m), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder A;
s2, uniformly mixing large-particle-size graphite (D50 is 15 microns), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder B;
s3, spreading the powder A on at least one surface of a copper foil, spreading the powder B on the surface of the powder A far away from the copper foil, wherein the mass ratio of the powder A to the powder B is 1:3, and the single-side coating surface density is 22.0mg/cm2(ii) a Then compounding by hot rolling at 80 ℃ and 10 MPa; the thickness of the obtained active layer a was 60 μm and the thickness of the obtained active layer B was 183 μm, and the preparation of the negative electrode sheet was completed.
The negative plate is used in a lithium ion battery, the positive electrode is made of conventional lithium cobaltate materials, the lithium ion battery is formed by winding, and electrolyte is injected to obtain the lithium ion battery.
Example 8
Unlike example 7, the temperature of the hot rolling was 30 ℃.
The rest is the same as embodiment 7, and the description is omitted here.
Example 9
Unlike example 7, the temperature of the hot rolling was 200 ℃.
The rest is the same as embodiment 7, and the description is omitted here.
Example 10
Different from example 7, the temperature of hot rolling was 300 ℃.
The rest is the same as embodiment 7, and the description is omitted here.
Example 11
Different from example 7 in the mass ratio of powder A to powder B, 1: 8.
The rest is the same as embodiment 7, and the description is omitted here.
Example 12
Different from example 7 in the mass ratio of powder A to powder B, 2: 1.
The rest is the same as embodiment 7, and the description is omitted here.
Example 13
A preparation method of a positive plate comprises the following steps:
s1, uniformly mixing small-particle-size lithium cobaltate (D50 is 8 mu m), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder A;
s2, uniformly mixing large-particle-size lithium cobaltate (D50 is 14 microns), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder B;
s3, spreading the powder A on at least one surface of an aluminum foil, spreading the powder B on the surface of the powder A far away from the aluminum foil, wherein the mass ratio of the powder A to the powder B is 4:5, and the single-side coating surface density is 40.0mg/cm2(ii) a Then compounding by hot rolling at 100 ℃ and 10 MPa; the thickness of the obtained active layer A was 88 μm, and the thickness of the active layer B was 115 μm; and finishing the preparation of the positive plate.
A preparation method of a negative plate comprises the following steps:
s1, uniformly mixing small-particle-size graphite (D50 is 10 mu m), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder A;
s2, uniformly mixing large-particle-size graphite (D50 is 15 microns), a conductive agent Super-p and a binder PVDF according to the mass ratio of 97:1:2 to prepare powder B;
s3, spreading the powder A on at least one surface of a copper foil, spreading the powder B on the surface of the powder A far away from the copper foil, wherein the mass ratio of the powder A to the powder B is 1:3, and the single-side coating surface density is 22.0mg/cm2(ii) a Then compounding by hot rolling at 80 ℃ and 10 MPa; the thickness of the obtained active layer a was 60 μm and the thickness of the obtained active layer B was 183 μm, and the preparation of the negative electrode sheet was completed.
And (3) using the obtained positive plate and negative plate in a lithium ion battery, winding to form the lithium ion battery, and injecting electrolyte to obtain the lithium ion battery.
Comparative example 1
The preparation method of the positive plate comprises the following steps: uniformly mixing and stirring lithium cobaltate, conductive carbon Super-p and a binder PVDF by wet stirring according to the mass ratio of 97:1:2 to prepare anode slurry; coating the positive electrode slurry on an aluminum foil, drying and rolling to obtain a positive electrode plate with the single-side coating surface density of 40.0mg/cm2。
The preparation method of the negative plate comprises the following steps: uniformly mixing and stirring graphite, conductive carbon Super-p and a binder PVDF by wet stirring according to a mass ratio of 97:1:2 to prepare cathode slurry; coating the negative electrode slurry on a copper foil, drying and rolling to obtain a negative electrode sheet, wherein the single-side coating surface density of the negative electrode sheet is 22.0mg/cm2。
And (3) using the obtained positive plate and negative plate in a lithium ion battery, winding to form the lithium ion battery, and injecting electrolyte to obtain the lithium ion battery.
The lithium ion batteries obtained in the above examples 1 to 13 and comparative example 1 were subjected to a rate discharge test at 0.2 to 3C, respectively.
The test results are shown in table 1 and fig. 2.
TABLE 1
Figure BDA0003329567360000101
Figure BDA0003329567360000111
It can be seen from the test results of the above examples 1 to 13 and comparative example 1 that the cycle performance of the lithium ion battery obtained by using the electrode sheet obtained by the preparation method of the present invention is more excellent regardless of the positive electrode sheet, the negative electrode sheet, or the positive and negative electrode sheets. The preparation method is mainly realized by matching the active layer with the particle size with a dry-method material mixing and hot rolling preparation, so that the adhesion of the pole piece is ensured, and the dynamic performance of the pole piece is also ensured.
In addition, as can be seen from the comparison of examples 1 to 6 and 7 to 12, the hot roll pressing conditions for the preparation of the two and the mass ratio of the active layer have different effects on the cycle performance. When the large-particle-size electrode material is arranged in a large amount, the cycle performance is more excellent, and the overall energy density of the battery is higher due to the fact that the large-particle-size electrode material is arranged in a large amount.
The preparation method provided by the invention solves the problems that the current thick electrode plate is difficult to coat and easy to crack and has poor lithium conducting performance, has simple process and environmental friendliness, and is more suitable for the current requirements on high-energy-density batteries.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. The preparation method of the electrode plate is characterized by comprising the following steps:
s1, mixing the first electrode material with a conductive agent and a binder to prepare powder A;
s2, mixing a second electrode material with a conductive agent and a binder to prepare powder B, wherein the second electrode material and the first electrode material are the same material, and the particle size D50 of the second electrode material is larger than the particle size D50 of the first electrode material;
s3, spreading the powder A on at least one surface of a current collector, spreading the powder B on the surface of the powder A away from the current collector, and compounding by hot rolling to finish the preparation of the electrode plate.
2. The method for preparing the electrode sheet according to claim 1, wherein the first electrode material and the second electrode material are both positive electrode materials, the particle size D50 of the first electrode material is not more than 9 μm, and the particle size D50 of the second electrode material is more than 9 μm.
3. The method for preparing the electrode sheet according to claim 2, wherein the mass ratio of the powder A to the powder B is 1: (1.1-2).
4. The method for preparing the electrode sheet according to claim 1, wherein the first electrode material and the second electrode material are both negative electrode materials, the particle size D50 of the first electrode material is not more than 12 μm, and the particle size D50 of the second electrode material is more than 12 μm.
5. The preparation method of the electrode sheet according to claim 4, wherein the mass ratio of the powder A to the powder B is 1: (2-10).
6. The method for preparing an electrode sheet according to claim 1, wherein in step S1, the first electrode material is mixed with a conductive agent and a binder by a V-type mixing device; in step S2, the second electrode material, the conductive agent, and the binder are mixed by a V-type mixing device.
7. The method for producing an electrode sheet according to claim 1, wherein in step S3, the conditions for the hot rolling are: the temperature is 30-300 ℃, and the pressure is 5-25 MPa.
8. The method for preparing the electrode sheet according to claim 1, wherein the binder is at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, and styrene-butadiene rubber; the conductive agent is at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotube and graphene.
9. An electrode sheet produced by the method for producing an electrode sheet according to any one of claims 1 to 8.
10. A secondary battery comprising a positive electrode tab, a negative electrode tab, and a separator interposed between the positive electrode tab and the negative electrode tab, wherein the positive electrode tab and/or the negative electrode tab is the electrode tab according to claim 9.
CN202111276543.2A 2021-10-29 2021-10-29 Preparation method and application of electrode slice Pending CN114068857A (en)

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