CN113351450A - Coating process and coating device for lithium ion battery pole piece - Google Patents
Coating process and coating device for lithium ion battery pole piece Download PDFInfo
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- CN113351450A CN113351450A CN202110614035.4A CN202110614035A CN113351450A CN 113351450 A CN113351450 A CN 113351450A CN 202110614035 A CN202110614035 A CN 202110614035A CN 113351450 A CN113351450 A CN 113351450A
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- 238000000576 coating method Methods 0.000 title claims abstract description 58
- 239000011248 coating agent Substances 0.000 title claims abstract description 27
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 23
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 23
- 239000011230 binding agent Substances 0.000 claims abstract description 113
- 239000011267 electrode slurry Substances 0.000 claims abstract description 53
- 239000011888 foil Substances 0.000 claims abstract description 36
- 239000002002 slurry Substances 0.000 claims abstract description 32
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 17
- 239000010439 graphite Substances 0.000 claims abstract description 17
- 238000002156 mixing Methods 0.000 claims abstract description 12
- 230000003247 decreasing effect Effects 0.000 claims abstract description 9
- 239000002994 raw material Substances 0.000 claims abstract description 3
- 238000005507 spraying Methods 0.000 claims description 12
- 239000006258 conductive agent Substances 0.000 claims description 8
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- 239000011889 copper foil Substances 0.000 claims description 3
- 229920005822 acrylic binder Polymers 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 18
- 238000013508 migration Methods 0.000 abstract description 11
- 230000005012 migration Effects 0.000 abstract description 11
- 230000008569 process Effects 0.000 abstract description 10
- 239000006185 dispersion Substances 0.000 abstract description 4
- 230000009467 reduction Effects 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 11
- 239000002245 particle Substances 0.000 description 10
- 239000000853 adhesive Substances 0.000 description 8
- 230000001070 adhesive effect Effects 0.000 description 8
- 238000009826 distribution Methods 0.000 description 8
- 238000001035 drying Methods 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- 239000006257 cathode slurry Substances 0.000 description 6
- 239000002174 Styrene-butadiene Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 4
- 230000008020 evaporation Effects 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000003384 imaging method Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004043 dyeing Methods 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000006255 coating slurry Substances 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 230000005499 meniscus Effects 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000007581 slurry coating method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 229920001909 styrene-acrylic polymer Polymers 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/36—Successively applying liquids or other fluent materials, e.g. without intermediate treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/50—Multilayers
- B05D7/56—Three layers or more
- B05D7/58—No clear coat specified
- B05D7/582—No clear coat specified all layers being cured or baked together
-
- 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
- H01M4/0409—Methods of deposition of the material by a doctor blade method, slip-casting or roller coating
-
- 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
-
- 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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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Materials Engineering (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a coating process of a lithium ion battery pole piece, which comprises the steps of dividing a binder raw material into a plurality of parts of binders with gradually decreased mass, and mixing the parts of binders with gradually decreased mass with a plurality of parts of negative electrode graphite slurry respectively to prepare a plurality of parts of negative electrode slurry containing binders with different mass concentrations. The invention also provides a device using the coating process. According to the invention, a concentration gradient coating mode is adopted, a plurality of parts of negative electrode slurry are sequentially sprayed on the foil according to the sequence that the mass concentration of the binder in the negative electrode slurry is from high to low, and in the baking process, the content of the binder at the lower layer close to the foil is reduced and the content of the binder at the upper layer far away from the foil is increased along with the migration and the floating of the binder, so that the content of the binder in the multi-layer negative electrode slurry is basically consistent, the dispersion of the binder in the pole piece is uniform, and the problems of the reduction of the bonding strength and the increase of the internal resistance of the pole piece caused by the migration of the binder in the coating process of the lithium ion battery are solved.
Description
Technical Field
The invention relates to the technical field of lithium ion power batteries, in particular to a coating process and a coating device for a lithium ion battery pole piece.
Background
The coating process of the battery pole piece is a process of uniformly coating the uniformly stirred slurry on a current collector and drying an organic solvent in the slurry. For example, patent CN110379997A discloses a coating process for positive and negative electrode plates of a lithium ion battery, which comprises the following steps: s1: weighing a consolidation source, a lithium source and a titanium source, mixing, stirring the mixed solution for 3 hours to form transparent sol in the mixing process, adding a diluent to keep the viscosity, standing for 3 hours at the temperature of 40-130 ℃ in the mixing process, and then stirring for the second time; s2: mixing a positive electrode active material or a negative electrode active material of a lithium ion battery with a conductive agent and a binder according to a certain proportion, and stirring to obtain positive electrode slurry or negative electrode slurry; s3: and mixing and stirring the sol in the S1 and the sol in the S2 according to a certain ratio, and drying and coating. The manufacturing process of the battery pole piece comprises five procedures of slurry preparation, slurry coating, pole piece rolling, pole piece slitting, pole piece drying and the like.
The peeling strength of the lithium battery pole piece refers to the firmness degree of the adhesion of the active substance of the pole piece and the current collector, is one of important indexes of the lithium battery pole piece, and has influence on the internal resistance and the cycle performance of the battery. Whether the binder is uniformly dispersed in the slurry plays a crucial role in the peel strength of the pole piece. The uniform coating slurry is beneficial to improving the peeling strength of the pole piece.
In the drying process of the pole piece, the SBR binder and the carbon black can migrate to the surface along with the evaporation of the solvent, so that a concentration gradient is generated inside the pole piece, particularly in the high-speed baking process. In the initial stage of drying, all components are uniformly distributed in the electrode, and in the drying process, as the solvent is evaporated, a concentration gradient exists at a gas-liquid interface, and a meniscus can be formed on the surface of the solid particle layer. The solvent migrates between the graphite particles to the surface by capillary forces and is accompanied by expansion of the particle layer. The particle size of the SBR adhesive is at least 100 times smaller than that of graphite, the spacing of graphite particles is enough to allow the SBR to move freely, and the polymer and the small-particle SBR are carried by the flowing of the solvent to migrate and float together, so that the adhesive particles are enriched on the upper layer of the pole piece. Under the condition of high-speed baking, the concentration gradient distribution of the binder from the current collector to the gas-liquid interface is continuously increased, the binder is rarely distributed at the current collector and the coating area, the binding between the binder and the foil is influenced, the peeling strength of the pole piece is directly reduced, and the internal resistance of the electrode is correspondingly increased. This will directly affect the performance of the battery and the lifetime. Therefore, in the process of manufacturing the battery, the defect of floating due to migration of the binder is reduced in the pole piece coating process, the coating quality and the yield are improved, the manufacturing cost is reduced, and the method is an important task to be solved in research and development of professionals in the lithium battery industry.
Disclosure of Invention
The invention aims to solve the technical problems of reduced bonding strength and increased internal resistance of a pole piece caused by the migration of a bonding agent in the coating process of the conventional battery pole piece.
The invention solves the technical problems through the following technical means:
a coating process of a lithium ion battery pole piece comprises the following steps:
(1) dividing the raw material of the binder into a plurality of parts of binders with gradually decreased mass;
(2) mixing a plurality of parts of binders with gradually decreased mass in the step (1) with a plurality of parts of negative electrode graphite slurry respectively to obtain a plurality of parts of negative electrode slurry containing binders with different mass concentrations;
(3) during coating, according to the sequence of the mass concentration of the binder in the negative electrode slurry from high to low, firstly spraying the negative electrode slurry containing the binder with high mass concentration on the foil, then spraying the negative electrode slurry containing the binder with medium mass concentration, and finally spraying the negative electrode slurry containing the binder with lowest mass concentration; the coating thicknesses of the negative electrode slurry containing the binders with different mass concentrations are kept consistent;
(4) and (5) baking to be dry after coating.
According to the invention, a concentration gradient coating mode is adopted, and a plurality of parts of negative electrode slurry are sequentially sprayed on the foil according to the sequence that the mass concentration of the binder in the negative electrode slurry is from high to low, so that the content of the binder at the lower layer close to the foil is highest, the content of the binder at the upper layer far away from the foil is lowest, the binder at the lower layer close to the foil floats upwards along with the migration of the binder in the baking process, the content of the binder at the upper layer far away from the foil is lower, the content of the binder at the upper layer is higher, the content of the binder in the multi-layer negative electrode slurry is basically consistent, the dispersion of the binder in the pole piece becomes uniform, the method for improving the phenomenon that the binder particles float upwards along with the evaporation migration of the solvent in the coating process is adopted, and the problems of the reduction of the binding strength and the increase of the internal resistance of the pole piece caused by the migration of the binder in the coating process of the lithium ion battery are solved.
Preferably, the coating thickness of the plurality of portions of the anode slurry containing the binders with different mass concentrations is kept uniform.
Preferably, the foil is a copper foil, and the thickness of the foil is 6-8 μm.
Preferably, the binder comprises Styrene Butadiene Rubber (SBR) or acrylic (PAA) binder.
Preferably, the mass concentration ratio of graphite to the conductive agent in the negative electrode graphite slurry is 95%: 1 percent.
Preferably, the binder is divided into three portions.
The invention also provides a device for using the coating process of the lithium ion battery pole piece, which comprises a slot and a plurality of slurry tanks; the feed end of the slot is respectively communicated with the discharge ends of the slurry tanks through a plurality of pipelines; each pipeline is connected with a vacuum pump;
and a plurality of negative electrode slurry containing binders with different mass concentrations are respectively arranged in a plurality of slurry tanks.
Furthermore, a plurality of groove dies are arranged in the narrow groove, and a feed inlet of each groove die is respectively communicated with discharge outlets of the plurality of pipelines.
Furthermore, the slurry tanks are three, and the feed ends of the slots are respectively communicated with the discharge ends of the three slurry tanks through three pipelines.
Further, three slot dies are arranged in the slot.
The invention has the following beneficial effects: according to the invention, a concentration gradient coating mode is adopted, and a plurality of parts of negative electrode slurry are sequentially sprayed on the foil according to the sequence that the mass concentration of the binder in the negative electrode slurry is from high to low, so that the content of the binder at the lower layer close to the foil is highest, and the content of the binder at the upper layer far away from the foil is lowest, and in the baking process, the content of the binder at the lower layer close to the foil is lowered, and the content of the binder at the upper layer far away from the foil is raised along with the migration of the binder, so that the content of the binder in the multi-layer slurry is basically consistent, the dispersion of the binder in the pole piece is uniform, the method for improving the phenomenon that the binder particles float along with the evaporation migration of the solvent in the coating process is adopted, and the problems of the reduction of the bonding strength.
Drawings
Fig. 1 is a schematic structural diagram of a device used in a coating process of a lithium ion battery pole piece according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the distribution of the binder in the coated battery plate of example 2 of the present invention;
fig. 3 is a schematic diagram of the binder distribution in a coated battery pole piece of a comparative example of the present invention.
Description of the reference numerals
1. A slot; 11. a slot die; 2. a slurry tank; 3. a vacuum pump; 4. a round roller; 5. and (3) foil material.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.
Example 1
As shown in fig. 1, the embodiment discloses a device used in a coating process of a lithium ion battery pole piece, which comprises a slot 1 and three slurry tanks 2;
as shown in fig. 1, a slot 1 of the present embodiment is internally provided with three slot dies 11, feed inlets of the three slot dies 11 are respectively communicated with discharge ends of three slurry tanks 2 through three pipelines, one end of the pipeline is welded and fixed with and communicated with the feed inlet of the slot die 11, and the other end of the pipeline is welded and fixed with and communicated with a discharge outlet of the slurry tank 2;
as shown in fig. 1, each of the pipes of the present embodiment is equipped with a vacuum pump 3.
The three slurry tanks 2 of the embodiment are respectively filled with the cathode slurry of the high-mass-concentration binder, the cathode slurry of the medium-mass-concentration binder and the cathode slurry of the lowest-mass-concentration binder, wherein the mass concentrations of the cathode slurry, the cathode slurry and the cathode slurry are gradually decreased.
During coating, the foil 5 is required to be placed on the round roller 4, then the three vacuum pumps 3 are started in sequence according to the different content of the binders in the negative electrode slurry in the three slurry tanks 2, the negative electrode slurry in the three slurry tanks 2 enters the three groove dies 11 of the slot 1 through the three pipelines respectively according to the sequence that the mass concentration of the binders in the negative electrode slurry is from high to low, the three groove dies 11 can spray the negative electrode slurry respectively, the negative electrode slurry containing the binders with high mass concentration is sprayed on the foil 5 firstly, then the negative electrode slurry containing the binders with medium mass concentration is sprayed, finally the negative electrode slurry containing the binders with lowest mass concentration is sprayed, and the coating thickness of the three negative electrode slurries is ensured to be the same.
Example 2
A coating process of a lithium ion battery pole piece comprises the following steps:
(1) dividing the SBR binder into three binders with the mass gradually decreased in a gradient manner, wherein the mass ratio of the three binders is 3.5: 3: 2.5;
(2) and (2) mixing the components in the step (1) in a mass ratio of 3.5: 3: and 2.5, respectively mixing the three parts of binder with the three parts of negative electrode graphite slurry to obtain three parts of negative electrode slurry containing binders with different mass concentrations, wherein the mass concentration ratio of each component in the first part of negative electrode slurry is graphite: conductive agent: adhesive: CMC is 95%: 1%: 3.5%: 0.5 percent, and the mass concentration ratio of each component in the second part of negative electrode slurry is graphite: conductive agent: adhesive: CMC is 95%: 1%: 3%: 1% and the third part is 95%: 1%: 3.5 ═ 95%: 1%: 2.5%: 1.5%, keeping the total binder usage of the battery pole piece unchanged;
(3) respectively filling the prepared three negative electrode slurry into three slurry tanks 2 of a coating device;
(4) during coating, according to the sequence that the mass concentration of the binder in the negative electrode slurry is from top to bottom, spraying a first part of negative electrode slurry on the foil 5, wherein the thickness of the foil 5 is 6 microns, then spraying a second part of negative electrode slurry, and finally spraying a third part of negative electrode slurry, so that the content of the binder in the experimental group of pole pieces before baking is in concentration gradient distribution, the content of the binder at the lower layer close to the foil is 3.5%, the middle concentration is 3%, and the content of the binder at the upper layer far away from the foil is 2.5%; the coating thicknesses of the three negative electrode pastes are ensured to be the same, and the distribution of the binder in the coated battery pole piece is shown in figure 2.
Example 3
A coating process of a lithium ion battery pole piece comprises the following steps:
(1) dividing the PAA binder into three binders with the mass gradually decreased, so that the mass ratio of the three binders is 3.5: 3: 2.5;
(2) and (2) mixing the components in the step (1) in a mass ratio of 3.5: 3: and 2.5, respectively mixing the three parts of binder with the three parts of negative electrode graphite slurry to obtain three parts of negative electrode slurry containing binders with different mass concentrations, wherein the mass concentration ratio of each component in the first part of negative electrode slurry is graphite: conductive agent: adhesive: CMC is 95%: 1%: 3.5%: 0.5 percent, and the mass concentration ratio of each component in the second part of negative electrode slurry is graphite: conductive agent: adhesive: CMC is 95%: 1%: 3%: 1% and the third part is 95%: 1%: 3.5 ═ 95%: 1%: 2.5%: 1.5%, keeping the total binder usage of the battery pole piece unchanged;
(3) respectively filling the prepared three negative electrode slurry into three slurry tanks 2 of a coating device;
(4) during coating, according to the sequence that the mass concentration of the binder in the negative electrode slurry is from top to bottom, spraying a first part of negative electrode slurry on the foil 5, wherein the thickness of the foil 5 is 7 micrometers, then spraying a second part of negative electrode slurry, and finally spraying a third part of negative electrode slurry, so that the content of the binder in the experimental group of pole pieces before baking is in concentration gradient distribution, the content of the binder at the lower layer close to the foil is 3.5%, the middle concentration is 3%, and the content of the binder at the upper layer far away from the foil is 2.5%; the coating thickness of the three negative electrode slurry is ensured to be the same.
Comparative example
In the comparative example, a copper foil of 6um was used, Styrene Butadiene Rubber (SBR) was used as a binder, and the ratio of the mass concentration of each component in the negative electrode slurry used was graphite: conductive agent: adhesive: CMC is 95%: 1%: 3%: 1%, the content of the binder in the prepared unbaked pole piece is 3%, and the distribution of the binder in the coated battery pole piece is shown in figure 3.
Example 4
The battery pole pieces coated in the example 2 (experimental group) and the comparative example (comparative group) are placed under the same conditions of baking speed, baking temperature, baking time, air quantity and the like for drying, the baking speed is 8m/min, the baking temperature is 75 ℃/85 ℃, the gradient baking is carried out, the baking time is 4min, the air quantity is 25 +/-10 Hz, the peeling strength and the resistivity of the comparative group and the experimental group before and after rolling the pole pieces are detected under the same conditions, and OsO is made on the fresh pole pieces of the comparative group and the experimental group after baking4And (3) dyeing imaging test, namely observing the distribution of the binder in the pole piece, and detecting the alternating current internal resistance of the batteries of the comparison group and the experimental group after the batteries with the same specification are prepared.
Further analysis shows that the experimental results are shown in the following table 1, the peeling of the comparative group of pole pieces before and after rolling is lower than that of the experimental group, the resistivity of the experimental group is lower than that of the comparative group, and the alternating current internal resistance of the battery of the experimental group is also obviously lower than that of the comparative group, which indicates that the peeling strength and the internal resistance of the pole pieces are effectively improved by adopting the method of adhesive content gradient coating; further, fresh pole pieces OsO of the baked comparative group and the baked experimental group4The dyeing imaging image shows that the contrast group binder migrates and floats upwards in the baking process, the red color of the upper layer binder is obviously darker, the color of the lower layer binder is lighter, and the colors of the upper, middle and lower layers of the experimental group pole piece imaging are lighterThe color is basically consistent, the binder is dispersed more uniformly, and the color is consistent with the experimental result.
Table 1 shows the comparison results of the peel strength and resistivity of the rolled pole pieces of the comparison group and the experimental group
In conclusion, the invention adopts a concentration gradient coating mode, and a plurality of parts of negative electrode slurry are sequentially sprayed on the foil 5 according to the sequence that the mass concentration of the binder in the negative electrode slurry is from high to low, so that the content of the binder at the lower layer close to the foil 5 is the highest, and the content of the binder at the upper layer far from the foil 5 is the lowest, and in the baking process, along with the migration and the floating of the binder, the content of the binder at the lower layer close to the foil 5 is reduced, and the content of the binder at the upper layer far from the foil 5 is increased, so that the content of the binder in the multi-layer slurry is basically consistent, the dispersion of the binder in the pole piece becomes uniform, the method for improving the phenomenon that the binder particles float upwards along with the evaporation of the solvent in the coating process is adopted, and the problems of the reduction of the bonding strength and the increase of the internal resistance of the pole piece caused by the migration of the binder in the coating process of the lithium ion battery are solved.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A coating process of a lithium ion battery pole piece is characterized by comprising the following steps:
(1) dividing the raw material of the binder into a plurality of parts of binders with gradually decreased mass;
(2) mixing a plurality of parts of binders with gradually decreased mass in the step (1) with a plurality of parts of negative electrode graphite slurry respectively to obtain a plurality of parts of negative electrode slurry containing binders with different mass concentrations;
(3) during coating, according to the sequence of the mass concentration of the binder in the negative electrode slurry from high to low, firstly spraying the negative electrode slurry containing the binder with high mass concentration on the foil, then spraying the negative electrode slurry containing the binder with medium mass concentration, and finally spraying the negative electrode slurry containing the binder with lowest mass concentration;
(4) and (5) baking to be dry after coating.
2. The coating process of the lithium ion battery pole piece, according to claim 1, is characterized in that: the coating thickness of the negative electrode slurry containing the binders with different mass concentrations is kept consistent.
3. The coating process of the lithium ion battery pole piece, according to claim 1, is characterized in that: the foil is a copper foil, and the thickness of the foil is 6-8 mu m.
4. The coating process of the lithium ion battery pole piece, according to claim 1, is characterized in that: the binder includes, but is not limited to, styrene butadiene rubber or acrylic binders.
5. The coating process of the lithium ion battery pole piece, according to claim 1, is characterized in that: the mass concentration ratio of graphite to the conductive agent in the negative electrode graphite slurry is 95%: 1 percent.
6. The coating process of the lithium ion battery pole piece, according to claim 1, is characterized in that: the binder is divided into three portions.
7. An apparatus using the coating process of the lithium ion battery pole piece according to any one of claims 1 to 6, characterized in that: comprises a slot and a plurality of slurry tanks; the feed end of the slot is respectively communicated with the discharge ends of the slurry tanks through a plurality of pipelines; each pipeline is connected with a vacuum pump;
and a plurality of negative electrode slurry containing binders with different mass concentrations are respectively arranged in a plurality of slurry tanks.
8. The apparatus of claim 7, wherein the coating process comprises: and a plurality of groove dies are arranged in the narrow groove, and the feed inlet of each groove die is respectively communicated with the discharge outlets of the plurality of pipelines.
9. The apparatus of claim 7, wherein the coating process comprises: the slurry tank is provided with three, the feed end of slot communicates with the discharge end of three slurry tank respectively through three pipeline.
10. The apparatus of claim 9, wherein the coating process comprises: and three slot dies are arranged in the slot.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110614035.4A CN113351450A (en) | 2021-06-02 | 2021-06-02 | Coating process and coating device for lithium ion battery pole piece |
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| CN202110614035.4A CN113351450A (en) | 2021-06-02 | 2021-06-02 | Coating process and coating device for lithium ion battery pole piece |
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Cited By (5)
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| CN115064653A (en) * | 2022-08-18 | 2022-09-16 | 成都特隆美储能技术有限公司 | Safe gel lithium ion battery for energy storage and preparation method thereof |
| WO2023133780A1 (en) | 2022-01-14 | 2023-07-20 | 宁德时代新能源科技股份有限公司 | Multilayer electrode sheet, and negative electrode, battery, and electrical apparatus using same |
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Application publication date: 20210907 |