CN113193200A - Conductive adhesive layer, negative electrode coating pole piece and rate type lithium ion power battery - Google Patents
Conductive adhesive layer, negative electrode coating pole piece and rate type lithium ion power battery Download PDFInfo
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- CN113193200A CN113193200A CN202110489963.2A CN202110489963A CN113193200A CN 113193200 A CN113193200 A CN 113193200A CN 202110489963 A CN202110489963 A CN 202110489963A CN 113193200 A CN113193200 A CN 113193200A
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- 239000012790 adhesive layer Substances 0.000 title claims abstract description 73
- 238000000576 coating method Methods 0.000 title claims abstract description 21
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- 239000011248 coating agent Substances 0.000 title claims abstract description 20
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 20
- 239000000843 powder Substances 0.000 claims abstract description 49
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- 239000000919 ceramic Substances 0.000 claims abstract description 33
- 239000006258 conductive agent Substances 0.000 claims abstract description 33
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 46
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 7
- 229910052744 lithium Inorganic materials 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
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- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 4
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- 230000001070 adhesive effect Effects 0.000 claims description 4
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- 239000004584 polyacrylic acid Substances 0.000 claims description 4
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- PLOYJEGLPVCRAJ-UHFFFAOYSA-N buta-1,3-diene;prop-2-enoic acid;styrene Chemical compound C=CC=C.OC(=O)C=C.C=CC1=CC=CC=C1 PLOYJEGLPVCRAJ-UHFFFAOYSA-N 0.000 claims description 3
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- NJVOHKFLBKQLIZ-UHFFFAOYSA-N (2-ethenylphenyl) prop-2-enoate Chemical compound C=CC(=O)OC1=CC=CC=C1C=C NJVOHKFLBKQLIZ-UHFFFAOYSA-N 0.000 claims description 2
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- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 2
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- 239000008112 carboxymethyl-cellulose Substances 0.000 claims description 2
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims description 2
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- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 2
- 239000011734 sodium Substances 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 2
- 239000011115 styrene butadiene Substances 0.000 claims description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 claims description 2
- 239000002245 particle Substances 0.000 abstract description 12
- 238000005520 cutting process Methods 0.000 abstract description 9
- 238000009830 intercalation Methods 0.000 abstract description 3
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- 239000007773 negative electrode material Substances 0.000 description 2
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- 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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- Battery Electrode And Active Subsutance (AREA)
Abstract
本发明公开了一种导电胶层、负极涂层极片与倍率型锂离子动力电池。所述导电胶层包括导电剂、粘结剂和陶瓷粉，以所述导电胶层的重量为100％计，所述导电剂的重量占比为80％～90％，所述粘结剂的重量占比为2％～15％，所述陶瓷粉的重量占比为2％～10％。将其设置于负极片表面，不仅可以防止负极片分切时，分切处应力释放引起极片分切边缘掉粉问题，还可以解决倍率型电芯负极片面密度小造成的负极表面颗粒问题，将其设置在倍率型负极片表面组成负极，可以获得良好的导电性和离子快速脱嵌性能，可以有效减少电池自放电，降低电池阻抗，提升电池的倍率性能，延长电池循环性能。
The invention discloses a conductive adhesive layer, a negative electrode coating pole piece and a rate type lithium ion power battery. The conductive adhesive layer includes a conductive agent, a binder and ceramic powder. Based on 100% of the weight of the conductive adhesive layer, the weight ratio of the conductive agent is 80% to 90%. The weight proportion is 2% to 15%, and the weight proportion of the ceramic powder is 2% to 10%. Placing it on the surface of the negative electrode sheet can not only prevent the problem of powder dropping at the cutting edge of the polar sheet caused by the stress release at the cutting position when the negative electrode sheet is cut, but also solve the problem of particles on the negative electrode surface caused by the low surface density of the negative electrode sheet of the rate-type cell. It can be arranged on the surface of the rate-type negative electrode sheet to form a negative electrode, which can obtain good electrical conductivity and rapid ion de-intercalation performance, which can effectively reduce the self-discharge of the battery, reduce the battery impedance, improve the rate performance of the battery, and prolong the battery cycle performance.
Description
Technical Field
The invention relates to the technical field of batteries, and relates to a conductive adhesive layer, a negative electrode coating pole piece and a rate type lithium ion power battery.
Background
The multiplying power type lithium ion power battery is mainly applied to a lithium ion battery for a 48V start-stop power supply, and the lithium ion battery is mainly characterized by high power performance requirement and continuous high multiplying power discharge operation at extremely low temperature. The electrode is designed as an important component of the battery cell and plays a decisive role in the high-rate performance of the battery cell. The high rate performance means that lithium ions can rapidly shuttle back and forth between the positive electrode and the negative electrode of the battery, wherein the design of the negative electrode of the lithium battery plays a key role.
The negative electrode of the lithium battery comprises electrode materials such as a negative active material, a conductive agent, a binder and a dispersing agent. The negative active material of the lithium ion battery for the 48V start-stop power supply is usually selected from intermediate-phase carbon microspheres, single-particle artificial graphite, hard carbon, soft carbon and other rate type graphite, and meanwhile, in order to meet the requirement of large rate charge and discharge performance of the battery, the graphite is selected to be small in particle size, and the graphite is subjected to soft carbon coating carbonization treatment, so that the D50 is less than or equal to 7 microns, the amount of graphite micropowder is large, and the surface area is large. After negative pole graphite is manufactured into a negative pole piece, when the pole piece is cut to manufacture the battery cell, the pole piece is easy to fall off powder, and the battery cell is short-circuited when the battery cell is assembled. CN105140460A discloses a coating and slitting design method for preventing the powder falling of the edge of a negative electrode, which divides a coating main area into an area A and an area B in the transverse direction, and can improve the condition that the edge of the area B is stressed unevenly when slitting through the gradual change of the thickness of the area B, and avoid the condition that the material falls off due to uneven stress of the slitting edge. CN206271808U discloses a pole piece of preventing powder falling and burr cuts device, improves through the structure of cutting the mechanism, and when cutting the pole piece, the both sides pole piece of cutter is being pressed by preforming frame one and preforming frame two respectively, has just reduced the production of burr when cutting, has improved the quality of pole piece cutting process. However, the above methods are all improved from the viewpoint of cutting method and apparatus, industrialization has certain limitations, and it is important to provide a method for improving only pole pieces without changing slitting process and apparatus. Regarding the improvement method of the pole piece, in order to promote the adhesion between the graphite and prevent the powder falling of the pole piece, the using amount of the adhesive needs to be increased, and meanwhile, the dispersing performance of the large-specific surface small-particle graphite in the slurry is poor, and the using amount of the dispersing agent needs to be increased. The increase of the binder and the dispersant leads to the increase of the wrapping area of graphite particles and the reduction of the passage of lithium ions entering and exiting from the graphite layers, thereby deteriorating the power performance of the negative electrode.
In addition, in order to meet the high-power performance requirement of lithium ions for 48V start-stop power supply, the surface density of the negative pole piece of the battery is small, and the single-side surface density is small, and is usually 35-50 g/m2And the single-sided active material layer of the coated negative pole piece is 30-45 mu m. Usually, the maximum particle size Dmax of the graphite powder is less than or equal to 25 μm, and the micro-agglomerated graphite powder or the graphite with large particle size in the slurry is easy to form particles in the negative plate, so that micro short circuit of the battery cell is caused.
Disclosure of Invention
In view of the problems in the background art, the present application aims to provide a conductive adhesive layer, a negative electrode coating pole piece and a rate type lithium ion power battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a conductive adhesive layer for a negative electrode, which comprises a conductive agent, a binder and ceramic powder, wherein the conductive agent accounts for 80-90 wt%, the binder accounts for 2-15 wt%, and the ceramic powder accounts for 2-10 wt%, based on 100 wt% of the conductive adhesive layer.
In the conductive adhesive layer of the present invention, the weight ratio of the conductive agent is 80% to 90%, for example, 80%, 81%, 82%, 83.5%, 85%, 86%, 88%, or 90%, etc., based on 100% by weight of the conductive adhesive layer; the weight ratio of the binder is 2-15%, such as 2%, 3%, 5%, 6%, 8%, 10%, 12%, 13% or 15%; the weight ratio of the ceramic powder is 2-10%, such as 2%, 3%, 5%, 6%, 8% or 10%.
In the conductive adhesive layer, the binder can bind the negative plate, so that the situation that the cut edge of the negative plate is subjected to powder falling caused by the stress release at the cut part when the negative plate is cut is prevented; the ceramic powder can form pores on the conductive adhesive layer, so that the porosity of the conductive adhesive layer is increased, and lithium ions can be favorably desorbed from and embedded into the negative electrode layer (such as a graphite negative electrode layer). The components are controlled within the range, particles on the surface of the negative plate can be covered under a certain coating thickness, good conductivity and cohesiveness are obtained, the problem of negative plate powder falling is solved, the occurrence of battery short circuit is reduced, the rapid de-intercalation of lithium ions can be ensured, and the requirements of high power, long cycle life and the like of a multiplying power battery are met.
In a preferred embodiment of the conductive adhesive layer of the present invention, the conductive agent is 80 to 88 wt% and the binder is 6 to 15 wt% based on 100 wt% of the conductive adhesive layer. According to the preferred technical scheme, a small amount of conductive agent is used, and the adhesive and the ceramic powder are matched, so that a better comprehensive effect can be obtained, and the rate capability is more excellent.
Preferably, the conductive adhesive layer is a water-based conductive adhesive layer or an oil-based conductive adhesive layer, wherein the water-based conductive adhesive layer further comprises a dispersant.
Preferably, the weight ratio of the dispersant in the aqueous conductive paste layer is 1% to 3%, for example, 1%, 1.5%, 2%, 2.5%, 3%, or the like.
Preferably, the conductive agent includes any one of conductive carbon black, conductive graphite, acetylene black, ketjen black, porous carbon, graphene, conductive carbon fiber, or carbon nanotube, or a mixture of at least two thereof.
Preferably, the ceramic powder comprises either or a mixture of alumina ceramic powder or boehmite powder.
In the invention, the conductive adhesive layer can be prepared by adopting water-based conductive paste (namely a water-based system) or oil-based conductive paste (namely an oil-based system). The conductive adhesive layer prepared from the water-based conductive paste is a water-based conductive adhesive layer, and the conductive adhesive layer prepared from the oil-based conductive paste is an oil-based conductive adhesive layer.
Preferably, the conductive adhesive layer is prepared by an aqueous system, and the solvent in the aqueous system comprises water and/or ethanol. However, the solvent is not limited to the above-mentioned solvents, and other aqueous solvents commonly used in the art may be used in the present invention.
Preferably, the binder in the aqueous system includes any one of or a mixture of at least two of styrene butadiene emulsion, styrene acrylate emulsion, styrene butadiene acrylate emulsion, polyethylene emulsion, polypropylene emulsion, polyacrylic acid solution, polyacrylonitrile solution, polyacrylic acid-acrylamide copolymer solution, polyacrylic acid-acrylonitrile solution, or polyacrylic acid-acrylamide-acrylonitrile copolymer solution.
Preferably, the aqueous system further comprises a dispersant, and the dispersant comprises any one or a mixture of at least two of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, sodium carboxyethyl cellulose, lithium carboxyethyl cellulose and polyvinylpyrrolidone.
For a water system, the dispersant is added to better disperse the conductive agent and the ceramic powder to obtain water-based conductive slurry with good dispersibility, so that a glue layer with good uniformity can be obtained in the subsequent coating process.
Preferably, in the aqueous system, the dry weight of the binder is 2% to 12% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, etc.), the dry weight of the dispersant is 1% to 3% (e.g., 1%, 1.2%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, etc.), the dry weight of the conductive agent is 80% to 90% (e.g., 80%, 82%, 83%, 85%, 86%, 88%, 90%, etc.), and the dry weight of the ceramic powder is 2% to 10% (e.g., 2%, 3%, 4%, 5%, 6%, 8%, 9%, etc.); the aqueous system has a solid content of 5% to 15% (e.g., 5%, 6%, 8%, 9%, 10%, 12%, 13%, 15%, etc.) and a viscosity of 500mpa.s to 1000mpa.s (e.g., 500mpa.s, 550mpa.s, 600mpa.s, 650mpa.s, 700mpa.s, 800mpa.s, 900mpa.s, 1000mpa.s, etc.).
Preferably, the conductive adhesive layer is prepared by an oil system, and a solvent in the oil system comprises N-methylpyrrolidone. However, the solvent is not limited to the above-mentioned solvents, and other oil-based solvents commonly used in the art may be used in the present invention.
Preferably, the binder in the oil system comprises any one of or a mixture of at least two of polyacrylic acid solution, polyacrylonitrile solution, polyacrylic acid-acrylamide copolymer solution, polyacrylic acid-acrylonitrile solution, polyacrylic acid-acrylamide-acrylonitrile copolymer solution, polyvinylidene fluoride, polytetrafluoroethylene or polyhexafluoropropylene.
Preferably, in the oil-based system, the dry weight of the binder is 3% to 15% (e.g., 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 13%, 14%, or 15%), the dry weight of the conductive agent is 80% to 90% (e.g., 80%, 82%, 83%, 85%, 86%, 88%, or 90%, etc.), and the dry weight of the ceramic powder is 2% to 10% (e.g., 2%, 3%, 4%, 5%, 6%, 8%, or 9%, etc.); the oil system has a solid content of 5% to 15% (for example, 5%, 6%, 8%, 9%, 10%, 12%, 13%, 15%, etc.) and a viscosity of 500mPa.S to 1000mPa.S (for example, 500mPa.S, 550mPa.S, 600mPa.S, 650mPa.S, 700mPa.S, 800mPa.S, 900mPa.S, 1000mPa.S, etc.).
In a second aspect, the present invention provides a negative electrode coating electrode sheet, which includes a negative electrode sheet and the conductive adhesive layer of the first aspect disposed on two side surfaces of the negative electrode sheet.
In the invention, the thicknesses of the conductive adhesive layers on the two side surfaces can be the same or different.
Preferably, the thickness of the conductive adhesive layer on the two side surfaces of the negative electrode sheet is independently 1 μm to 3 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm. The "independently" means: the thickness of the two side glue layers can be selected to be the same or different.
The preparation method of the negative electrode coating pole piece can adopt the method disclosed in the prior art, for example, the water-based conductive slurry or the oil-based conductive slurry is coated on the negative electrode piece, and after drying, the double-layer coating negative electrode piece is formed.
The conductive adhesive layer is particularly suitable for being formed on the two side surfaces of the rate type negative plate, and obviously improves the rate performance.
In a third aspect, the invention provides a rate lithium ion power battery, which comprises the negative electrode coating pole piece of the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
the conductive adhesive layer provided by the invention comprises a conductive agent, a binder and ceramic powder which are specially composed, and the conductive adhesive layer is arranged on the surface of a negative plate, so that the problem of powder falling of the cut edge of the negative plate caused by stress release of the cut part when the negative plate is cut can be prevented, the problem of negative surface particles caused by small surface density of the negative plate of a multiplying power type battery cell can be solved, the conductive adhesive layer is arranged on the surface of the multiplying power type negative plate to form a negative electrode, good conductivity and quick ion de-intercalation performance can be obtained, the self-discharge of the battery can be effectively reduced, the impedance of the battery is reduced, the multiplying power performance of the battery is improved, and the cycle performance of the battery is prolonged.
Drawings
FIG. 1 is a schematic diagram of a negative coating pole piece of the invention, 1-a current collector, 2-a graphite layer, and 3-a conductive adhesive layer.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Example 1
This embodiment provides a conductive adhesive layer of a negative electrode, which comprises the following components, based on 100% of the total weight of the conductive adhesive layer: the conductive agent accounts for 85% by weight, the binder accounts for 10% by weight, and the ceramic powder accounts for 5% by weight. The conductive agent is a mixture of carbon nanotubes, porous carbon and acetylene black according to the mass ratio of 1:1:1, the binder is polyhexafluoropropylene, and the ceramic powder is alumina ceramic powder.
The conductive adhesive layer is prepared by an oil system, wherein the oil system comprises the following components in parts by weight: the N-methyl pyrrolidone, the binder, the conductive agent and the ceramic powder are prepared into oil conductive slurry with certain viscosity, the solid content of the oil conductive slurry is 8%, and the viscosity is 852 mPa.S.
The embodiment also provides a negative electrode coating pole piece (with a structural schematic view as shown in fig. 1), which comprises a rate type negative pole piece and the conductive adhesive layers arranged on the surfaces of the two sides of the rate type negative pole piece, wherein the thickness of the conductive adhesive layers on the two sides of the rate type negative pole piece is 2 μm;
multiplying power type negative pole piece includes the mass flow body 1 and is located the graphite layer 2 on the mass flow body both sides surface, and the graphite layer 2 on both sides surface contacts with conducting resin layer 3 respectively, the mass flow body 1 is the copper foil, the negative pole active material that the graphite layer adopted is D50 for 6 mu m's graphite, and single face areal density is 40g/m2。
Example 2
This embodiment provides a conductive adhesive layer of a negative electrode, which comprises the following components, based on 100% of the total weight of the conductive adhesive layer: the conductive agent accounts for 83% by weight, the binder accounts for 7% by weight, and the ceramic powder accounts for 10% by weight. The conductive agent is a mixture of conductive carbon fibers and conductive carbon black according to the mass ratio of 1:1, the binder is polyacrylonitrile, and the ceramic powder is alumina ceramic powder.
The conductive adhesive layer is prepared by an oil system, wherein the oil system comprises the following components in parts by weight: the N-methyl pyrrolidone, the binder, the conductive agent and the ceramic powder are prepared into oil conductive slurry with certain viscosity, wherein the solid content of the oil conductive slurry is 10%, and the viscosity is 645 mPa.S.
The embodiment also provides a negative electrode coating pole piece (with a structural schematic view as shown in fig. 1), which comprises a rate type negative pole piece and the conductive adhesive layers arranged on the surfaces of the two sides of the rate type negative pole piece, wherein the thickness of the conductive adhesive layers on the two sides of the rate type negative pole piece is 2 μm;
multiplying power type negative pole piece includes the mass flow body 1 and is located the graphite layer 2 on the mass flow body both sides surface, and the graphite layer 2 on both sides surface contacts with conducting resin layer 3 respectively, the mass flow body 1 is the copper foil, the negative pole active material that the graphite layer adopted is D50 for 6.5 mu m's graphite, and single face areal density is 35g/m2。
Example 3
The difference from the example 1 is that the composition is as follows, based on the total weight of the conductive adhesive layer as 100%: the conductive agent accounts for 90% by weight, the binder accounts for 5% by weight, and the ceramic powder accounts for 5% by weight.
Example 4
This embodiment provides a conductive adhesive layer of a negative electrode, which comprises the following components, based on 100% of the total weight of the conductive adhesive layer: the conductive agent accounts for 87% by weight, the binder accounts for 7% by weight, the dispersant accounts for 1% by weight, and the ceramic powder accounts for 5% by weight. The conductive agent is a mixture of carbon nano tubes, graphene and acetylene black according to a mass ratio of 1:1:1, the binder is styrene butadiene acrylate, the dispersing agent is polyvinylpyrrolidone, and the ceramic powder is alumina ceramic powder.
The conductive adhesive layer is prepared by a water system, wherein the water system comprises the following components: the water-based conductive paste with certain viscosity is prepared from ethanol, a binder, a conductive agent, a dispersing agent and ceramic powder, wherein the solid content of the oil-based conductive paste is 5%, and the viscosity is 745 mPa.S.
The embodiment also provides a negative electrode coating pole piece (with a structural schematic view as shown in fig. 1), which comprises a rate type negative pole piece and the conductive adhesive layers arranged on the surfaces of the two sides of the rate type negative pole piece, wherein the thicknesses of the conductive adhesive layers on the two sides of the rate type negative pole piece are respectively 3 μm and 2.5 μm;
multiplying power type negative pole piece includes the mass flow body 1 and is located the graphite layer 2 on the mass flow body both sides surface, and the graphite layer 2 on both sides surface contacts with conducting resin layer 3 respectively, the mass flow body 1 is the copper foil, the negative pole active material that the graphite layer adopted is D50 for 7 mu m's graphite, and single face areal density is 33g/m2。
Comparative example 1
The difference from the example 1 is that the weight ratio of the conductive agent to the binder is ensured to be the same as that of the example 1 without adding the ceramic powder.
Comparative example 2
The difference from the example 1 is that the composition is as follows, based on the total weight of the conductive adhesive layer as 100%: the conductive agent accounts for 94% by weight, the binder accounts for 1% by weight, and the ceramic powder accounts for 5% by weight.
And (3) detection: the negative coating pole piece of each example was used as a negative pole piece, with a positive pole piece, a separator and an electrolyte (1mol/L LiPF)6And EC: EMC volume ratio is 1:1) to assemble the rate lithium ion battery and detect the electrochemical performance of the rate lithium ion battery, and the test results are shown in Table 1. Wherein, the active material that positive pole piece adopted is NCM622, and NCM 622: conductive carbon black: multi-walled carbon nanotubes: 96 wt% of PVDF, 2.0 wt% of PVDF, 1.0 wt% of PVDF and 1.0 wt% of PVDF.
The performance test method comprises the following steps: and carrying out charge and discharge tests on the obtained battery at the temperature of 25 +/-2 ℃, wherein the charge and discharge voltage is 4.2-3.0V. Respectively testing the 20C rate performance under the normal temperature condition and the capacity retention rate of 500 cycles at 45 ℃.
And testing the 20C rate performance under the normal temperature condition: charging to 4.2V at constant current and constant voltage of 0.2C at normal temperature, and cutting off 0.02C; constant current discharging to 3.0V at 0.2C, and recording the 0.2C discharge capacity as D0mAh; charging to 4.2V at constant current and constant voltage at 0.2C, and cutting off at 0.02C; constant current discharging at 20C to 3.0V, and recording the 20C discharge capacity as D1mAh; 20C discharge Rate Performance D1/D0Different scheme D1/D0The larger the value, the better the rate performance;
capacity retention test at 45 ℃ cycling 1000 weeks: charging to 4.2V at 45 ℃ under constant current and constant voltage of 2C, stopping charging at 0.02C, and standing for 10 minutes; discharging at 2C constant current to 3.0V, standing for 10 min, and circulating for 1000 weeks; wherein, the first week discharge capacity is recorded as D0mAh, recording the 1000-week discharge capacity as D1000mAh, 1000 cycle Performance D1000/D0Different scheme D1000/D0The larger the indicated cycle performance, the better the 1000 cycles.
TABLE 1
| 20C Rate Performance (%) | 1000 cycle Performance (%) | |
| Example 1 | 94.5 | 90.5 |
| Example 2 | 97.4 | 94.1 |
| Example 3 | 93.1 | 89.2 |
| Example 4 | 92.2 | 88.1 |
| Comparative example 1 | 91.1 | 84.6 |
| Comparative example 2 | 90.5 | 79.2 |
And (3) analysis:
as can be seen from the comparison between example 1 and example 3, the content of each composition has an important influence on the negative electrode sheet modified by the conductive adhesive layer, and the improvement effect is better when the preferable ranges (the weight ratio of the conductive agent is 80% to 88%, the weight ratio of the binder is 6% to 15%, and the weight ratio of the ceramic powder is 2% to 10%) are satisfied.
It can be seen from the comparison between example 1 and comparative example 1 that the ceramic powder is an essential component, and if the ceramic powder is not added, the conductive layer particles are compact, the porosity of the surface layer is low, and further, the lithium ions are blocked from being inserted into the channels on the surface layer, thereby reducing the rate performance, and as the number of cycles of charging and discharging increases, part of the active lithium cannot be inserted into the graphite layer and is diluted out from the surface of the conductive layer, thereby reducing the cycle performance.
It can be seen from the comparison between example 1 and comparative example 2 that if the content of the conductive agent is too large and the content of the binder is too small, the specific surface area of the powder particles increases while the content of the ceramic powder remains unchanged, more binder is adsorbed on the surface of the conductive agent, and the binding force between the conductive adhesive layer and the graphite layer decreases, and the conductive layer easily falls off from the surface of the graphite layer, thereby causing a micro short circuit inside the battery and reducing the rate and cycle performance.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
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