CN113471553B - Lithium-supplement positive pole piece and preparation method and application thereof - Google Patents

Lithium-supplement positive pole piece and preparation method and application thereof Download PDF

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CN113471553B
CN113471553B CN202110761896.5A CN202110761896A CN113471553B CN 113471553 B CN113471553 B CN 113471553B CN 202110761896 A CN202110761896 A CN 202110761896A CN 113471553 B CN113471553 B CN 113471553B
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stirring
lithium
slurry
solvent
pole piece
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CN113471553A (en
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方杰雄
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Hubei Eve Power 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • 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
    • 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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Abstract

The invention provides a lithium-supplement positive pole piece and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) Mixing the binder and the conductive agent, adding a part of first solvent, stirring, adding the rest of first solvent and the lithium supplement additive, stirring, and stirring in vacuum to obtain first slurry; (2) Mixing a main positive electrode material, a binder and 65-75% of a second solvent, adding a conductive agent and a lithium supplement additive after stirring, adding 12-18% of the second solvent, stirring, adding the rest of the second solvent and the conductive slurry, stirring, and then stirring in vacuum to obtain a second slurry; (3) The first slurry is coated on the surface of the positive current collector and baked to obtain a bottom-coated pole piece, then the second slurry is coated on the coating of the bottom-coated pole piece, and the lithium-supplement positive pole piece is obtained through baking.

Description

Lithium-supplement positive pole piece and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a lithium supplement positive pole piece and a preparation method and application thereof.
Background
Lithium ion secondary batteries are widely used because of their high output voltage, good cycle performance, high energy density, and environmental friendliness. With the increasing reduction of fossil energy and the rising of global environmental awareness, new energy electric vehicles are considered as the best choice for replacing fuel vehicles in the future. The popularization of new energy vehicles inevitably puts higher and higher requirements on the performance of the lithium ion battery, such as long endurance, so that market demands and resource supply are given to the research and development of the high-energy density battery. The high energy density is the key for enabling new energy vehicles to enter the market to replace fuel vehicles in the future while the requirements of safety performance, rate performance and cycle performance of batteries are met.
A solid electrolyte interface film (SEI) generated on the surface of a negative active material during the first charging process of a lithium ion battery is an important cause of the reduction of the energy density of the battery, and the generation of the SEI film needs to consume a lithium source in a positive active material to cause the loss of the capacity of a battery cell and the reduction of the first effect, which is particularly obvious in a negative plate taking a silicon/tin alloy material as an active material. Meanwhile, the SEI film has the function of stabilizing the battery cell system and protecting the negative active material, so that the SEI film with moderate thickness and uniform load is indispensable.
In order to ensure the existence of the SEI film and reduce the irreversible capacity of the battery cell caused by the generation of the SEI film, regarding the lithium supplement method of the lithium ion battery anode at home and abroad, the lithium supplement additive is generally added into the anode material slurry during homogenizing, or the lithium supplement additive is coated on the surface of an anode plate and then is rolled.
CN110137433A discloses a method for supplementing lithium to a lithium ion battery positive plate, which comprises coating positive slurry on the surface of the positive plate, spraying a positive lithium supplementing additive on the surface of the positive plate immediately, and drying the positive plate. The uniformity of lithium supplement of the method is poor.
CN110120493A discloses a lithium supplement method for a lithium ion battery anode, which is used for lithium supplement of the lithium ion battery anode. In the positive electrode pulping process, the lithium supplement material is uniformly mixed with the main positive electrode material, the conductive agent, the binder, the solvent and other materials, and then the lithium battery is prepared by the working procedures of coating, rolling, assembling, injecting, forming, grading and the like. The method has long operation period and poor homogenization effect, so that the energy density of the prepared lithium ion battery is low.
The above scheme has the problem of long operation period or poor lithium supplement uniformity (poor homogenization effect), so that the development of the positive pole piece for the lithium ion battery, which has short operation period and good lithium supplement uniformity, is necessary.
Disclosure of Invention
The invention aims to provide a lithium-supplement positive pole piece and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a preparation method of a lithium-supplement positive pole piece, which comprises the following steps:
(1) Mixing the binder and the conductive agent, adding a part of first solvent, stirring for the first time, adding the rest first solvent and the lithium supplement additive, stirring for the second time, and stirring for the first time in vacuum to obtain first slurry;
(2) Mixing a main positive electrode material, a binder and 65-75% of a second solvent, stirring for three times, adding a conductive agent and a lithium supplement additive, stirring for four times, adding 12-18% of the second solvent, stirring for five times, adding the rest of the second solvent and the conductive slurry, stirring for six times, and then stirring in vacuum for two times to obtain a second slurry;
(3) And coating the first slurry on the surface of a positive current collector, baking for the first time to obtain a first slurry primary coating pole piece, coating the second slurry on the slurry side of the first slurry primary coating pole piece, and baking for the second time to obtain the lithium supplement positive pole piece.
The method optimizes the slurry homogenizing process in the preparation process of the positive pole piece, not only can save stirring time and cost, but also can improve the uniformity of the prepared slurry, and simultaneously can reduce lithium ions consumed by an SEI film formed by a negative pole during charging, so that the lithium ions extracted from the positive pole piece are not wasted on the formed SEI film. In the beginning of the preparation of the positive plate, a layer of primer slurry with the lithium supplement additive is coated on the aluminum foil of the positive current collector, and then the positive slurry with the lithium supplement additive is coated to manufacture the lithium supplement positive plate, so that the energy density of the lithium ion battery using the positive plate can be improved.
According to the invention, most of the solvent is used for dissolving the binder and the conductive agent in the process of preparing the first slurry, so that the binder and the conductive agent can be uniformly mixed, and the uniformly dispersed first slurry can be obtained more quickly after the lithium supplement additive is added.
In the process of preparing the second slurry, most of the solvent is used for dissolving the main anode material and the binder to be uniformly mixed, then the lithium supplement additive and a small part of the solvent are simultaneously added into the slurry, so that the lithium supplement additive can be rapidly and uniformly mixed, and finally a small part of the solvent and the conductive slurry are added to obtain the uniformly mixed second slurry in a relatively short time.
Preferably, the binder of step (1) comprises polyvinylidene fluoride.
Preferably, the conductive agent of step (1) comprises conductive carbon black SP.
Preferably, the first solvent of step (1) comprises azomethylpyrrolidone.
Preferably, the manner of adding the first solvent in step (1) comprises spraying.
Preferably, the revolution speed of one stirring in the step (1) is 10 to 20rpm, for example: 10rpm, 12rpm, 15rpm, 18rpm.
Preferably, the dispersing speed of the one-time stirring in the step (1) is 150 to 250rpm, for example: 150rpm, 180rpm, 200rpm, 250rpm, or the like.
Preferably, the time for one stirring in step (1) is 20 to 40min, for example: 20min, 25min, 30min, 35min or 40min and the like.
In the process of preparing the first slurry, the adhesive and the conductive agent are mixed firstly, partial solvent is added in a spraying mode, and the powder or wet material layer on the stirring paddle is washed, so that the adhesive and the conductive agent can be uniformly mixed in a short time, and the solvent can be saved.
Preferably, the lithium supplement additive in step (1) comprises Li 3 N。
Preferably, the mass ratio of the binder, the conductive agent and the lithium supplement additive in the step (1) is (2-4): 40-44): 52-58, for example: 40, 41.
Preferably, the revolution speed of the secondary stirring in the step (1) is 15 to 25rpm, for example: 15rpm, 18rpm, 20rpm, 23rpm, 25rpm, or the like.
Preferably, the dispersion speed of the secondary stirring in the step (1) is 800 to 1200rpm, for example: 800rpm, 900rpm, 1000rpm, 1100rpm, 1200rpm, or the like.
Preferably, the time for the second stirring in step (1) is 20 to 40min, for example: 20min, 25min, 30min, 35min or 40min and the like.
Preferably, the vacuum degree of the primary vacuum stirring in the step (1) is less than or equal to-0.085 MPa.
Preferably, the revolution speed of the one vacuum stirring in the step (1) is 20 to 30rpm, for example: 20rpm, 22rpm, 25rpm, 28rpm, 30rpm, or the like.
Preferably, the dispersion speed of the one-time vacuum stirring in the step (1) is 1200-1800 rpm, for example: 1200rpm, 1300rpm, 1400rpm, 1500rpm, 1600rpm, 1700rpm, 1800rpm, or the like.
Preferably, the time of the one-time vacuum stirring in the step (1) is 50 to 70min, for example: 50min, 55min, 60min, 65min or 70min and the like.
Preferably, the positive electrode main material in the step (2) comprises any one of lithium iron phosphate, a ternary nickel cobalt manganese material or a lithium cobaltate material or a combination of at least two of the materials.
Preferably, the binder of step (2) comprises polyvinylidene fluoride.
Preferably, the second solvent of step (2) comprises N-methylpyrrolidone.
Preferably, the manner of adding the second solvent in step (2) comprises spraying.
Preferably, the revolution speed of the three times of stirring in the step (2) is 15 to 25rpm, for example: 15rpm, 18rpm, 20rpm, 13rpm, 25rpm, or the like.
Preferably, the dispersion speed of the three times of stirring in the step (2) is 400 to 600rpm, for example: 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, or the like.
Preferably, the time for the three times of stirring in the step (2) is 40 to 50min, for example: 40min, 42min, 45min, 48min or 50min and the like.
In the process of preparing the second slurry, the solvent is continuously added into the mixer in a spraying mode to wash the powder or wet material layer on the stirring paddle, the stirring is carried out for 45min while adding, the powder material continuously sinks to the bottom of the stirring paddle to be soaked, and the continuous kneading and the friction dispersion are carried out.
Preferably, the conductive agent of step (2) comprises conductive carbon black SP.
Preferably, the lithium supplement additive of step (2) comprises Li 3 N。
Preferably, the mass ratio of the positive electrode main material, the binder, the conductive agent and the lithium supplement additive in the step (2) is (96-98): (1.2-1.5): 0.3-0.8): 0.5-0.9), for example: 97, 0.8.
Preferably, the revolution speed of the four times of stirring in the step (2) is 15 to 25rpm, for example: 15rpm, 18rpm, 20rpm, 23rpm, 25rpm, or the like.
Preferably, the dispersing speed of the four times of stirring in the step (2) is 800-1200 rpm, for example: 800rpm, 900rpm, 1000rpm, 1100rpm, 1200rpm, or the like.
Preferably, the four times of stirring in step (2) are carried out for 10 to 20min, for example: 10min, 12min, 15min, 18min or 20min and the like.
Preferably, the revolution speed of the five times of stirring in the step (2) is 20 to 30rpm, for example: 20rpm, 22rpm, 25rpm, 28rpm, 30rpm, or the like.
Preferably, the dispersing speed of the five times of stirring in the step (2) is 1800-2200 rpm, for example: 1800rpm, 1900rpm, 2000rpm, 2100rpm, 2200rpm, or the like.
Preferably, the time for five times of stirring in step (2) is 10 to 20min, for example: 10min, 12min, 15min, 18min or 20min and the like.
Preferably, the conductive paste of step (2) comprises a carbon nanotube conductive paste.
Preferably, the mass concentration of the conductive paste in the step (2) is 0.4-0.6%, for example: 0.4%, 0.45%, 0.5%, 0.55%, or 0.6%, etc.
Preferably, the mass ratio of the conductive agent in the conductive paste in the step (2) to the positive electrode main material is (0.4-0.6): (96-98), such as: 0.4.
Preferably, the revolution speed of the six times of stirring in the step (2) is 20-30 rpm, for example: 20rpm, 22rpm, 25rpm, 28rpm, 30rpm, or the like.
Preferably, the dispersing speed of the six times of stirring in the step (2) is 1800-2200 rpm, for example: 1800rpm, 1900rpm, 2000rpm, 2100rpm, 2200rpm, or the like.
Preferably, the six times of stirring in step (2) are carried out for 25 to 35min, for example: 25min, 28min, 30min, 32min or 35min and the like.
Preferably, the vacuum degree of the secondary vacuum stirring in the step (2) is less than or equal to-0.085 MPa.
Preferably, the revolution speed of the secondary vacuum stirring in the step (2) is 20 to 30rpm, for example: 20rpm, 22rpm, 25rpm, 28rpm, 30rpm, or the like.
Preferably, the dispersion speed of the secondary vacuum stirring in the step (2) is 1800-2200 rpm, for example: 1800rpm, 1900rpm, 2000rpm, 2100rpm, 2200rpm, or the like.
Preferably, the time of the second vacuum stirring in the step (2) is 40 to 50min, for example: 40min, 42min, 45min, 48min or 50min and the like.
In a second aspect, the invention provides a lithium supplement positive electrode piece, which is prepared by the method in the first aspect.
In a third aspect, the invention provides a lithium ion battery, which comprises the lithium-supplementing positive electrode piece according to the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) The method for preparing the lithium supplement anode piece has short preparation time, and the lithium supplement additive is uniformly distributed in the slurry, so that the energy density of the prepared lithium supplement anode piece is improved, lithium ions consumed by an SEI (solid electrolyte interphase) film formed by a negative electrode during charging are reduced, and the lithium ions extracted from an anode material are not wasted on the SEI film.
(2) The conductive agent of the square lithium-supplement positive pole piece prepared by the method disclosed by the invention is only rarely agglomerated, the agglomeration of the conductive agent can be avoided by adjusting the dispersion speed, the stripping force of the prepared pole piece can reach over 0.15N, and the stripping force of the prepared pole piece can reach 0.25N by adjusting the dispersion speed.
Drawings
FIG. 1 is a schematic diagram of the coating process of the positive electrode plate of the present invention, 1-first slurry coating, 2-roller, 3-roller, 4-primary baking, 5-roller passing, 6-second slurry coating, 7-roller passing, 8-secondary baking, 9-roller passing and 10-roller passing.
Detailed Description
The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a positive pole piece, and a preparation method of the positive pole piece comprises the following steps:
(1) Mixing 0.3kg polyvinylidene fluoride and 4.2kg conductive carbon black SP, adding 60% azomethyl pyrrolidone at revolution speed of 15rpm, dispersing at 200rpm while adding the materials under stirring, adding the rest azomethyl pyrrolidone and 5.5kg Li after 30min 3 Adding N into a mixer simultaneously, adding NMP while adding powder, continuously spraying and adding NMP, continuously stirring and dispersing, stirring at a revolution speed of 20rpm and a dispersion speed of 1000rpm for 30min at a high speed, opening the vacuum of the mixer to be less than or equal to-0.085MPa, at a revolution speed of 25rpm and at a dispersion speed of 1500rpm, uniformly mixing the slurry at a high speed, fully stirring the slurry uniformly, and stirring for 60min to prepare first slurry;
(2) 97kg of lithium iron powder, 1.3kg of polyvinylidene fluoride and 70% of azomethidone were mixed and simultaneously automatically fed into a mixer. Continuously adding NMP into a mixer in a spraying mode to wash a powder or wet material layer on a stirring paddle, stirring at the revolution speed of 20rpm and the dispersion speed of 500rpm, stirring for 45min while adding, and then adding 0.5kg of conductive carbon black SP and 0.7kg of Li 3 Stirring N at 20rpm revolution speed and 1000rpm dispersion speed for 15min, adding a 15-percent NMP solvent into a mixer, adding NMP in a spraying manner, stirring and dispersing at 25rpm revolution speed and 2000rpm dispersion speed for 15min, finally adding the remaining 15-percent NMP solvent and 1kg of CNT conductive slurry with solid content of 0.5 percent into the mixer simultaneously, continuously spraying NMP into the CNT slurry on a scouring stirring paddle to enable the CNT slurry to sink to the bottom of the stirring paddle, and stirring and dispersing at 25rpm revolution speed and 2000rpm dispersion speed for 30min; (5) uniformly mixing the stirrer at a vacuum opening of less than or equal to-0.085MPa, a revolution speed of 25rpm and a dispersion speed of 2000rpm at a high speed to fully and uniformly stir the slurry for 45min to obtain a second slurry;
(3) Coating the first slurry on the surface of a positive current collector, baking for the first time to obtain a first slurry priming pole piece, coating the second slurry on the coating of the first slurry priming pole piece, baking for the second time to obtain the lithium-supplementing positive pole piece, wherein the flow chart of the coating process is shown in figure 1.
Example 2
The embodiment provides a positive pole piece, and a preparation method of the positive pole piece comprises the following steps:
(1) Mixing 0.3kg polyvinylidene fluoride and 4.2kg conductive carbon black SP, adding 62% azomethyl pyrrolidone at 18rpm revolution speed, adding the materials while stirring at 220rpm dispersion speed, adding the rest azomethyl pyrrolidone and 5.5kg Li after 32min 3 Adding N into a mixer simultaneously, adding NMP while adding powder, continuously spraying and adding NMP, continuously stirring and dispersing, stirring for 28min at a revolution speed of 23rpm and a dispersion speed of 1100rpm at a high speed, opening the vacuum of the mixer to be less than or equal to-0.085MPa, the revolution speed of 28rpm and the dispersion speed of 1580rpm at a high speed, uniformly stirring the slurry fully, and stirring for 55min to prepare first slurry;
(2) 97kg of NCM811 powder, 1.3kg of polyvinylidene fluoride and 68% azomethylpyrrolidone were mixed while automatically feeding into the mixer. Continuously adding NMP into the mixer in a spraying manner to wash the powder or wet material layer on the stirring paddle, stirring at revolution speed of 22rpm and dispersion speed of 520rpm, stirring for 48min while adding, adding 0.5kg of conductive carbon black SP and 0.7kg of Li 3 N is stirred for 18min at the revolution speed of 23rpm and the dispersion speed of 1100rpm, then 16 percent of NMP solvent is added into a mixer, NMP is added in a spraying mode, stirring and dispersion are carried out for 18min at the revolution speed of 28rpm and the dispersion speed of 2100rpm, finally the residual 16 percent of NMP solvent and CNT conductive slurry are simultaneously added into the mixer, NMP is continuously sprayed and added into CNT slurry on a flushing stirring paddle to enable the CNT slurry to sink at the bottom of the stirring paddle, and stirring and dispersion are carried out for 32min at the revolution speed of 28rpm and the dispersion speed of 2200 rpm; (5) the vacuum opening of the stirrer is less than or equal to-0.085MPa, the revolution speed of 28rpm and the dispersion speed of 2200rpm are uniformly mixed at a high speed, so that the slurry is fully and uniformly stirred, and the stirring time is 48min to obtain a second slurry;
(3) And coating the first slurry on the surface of a positive current collector, baking for the first time to obtain a first slurry priming pole piece, coating the second slurry on the coating of the first slurry priming pole piece, and baking for the second time to obtain the lithium-supplement positive pole piece.
Example 3
This implementationExample only differs from example 1 in that the addition of Li as described in step (1) 3 The dispersion speed after N was 600rpm, and the other conditions and parameters were exactly the same as those in example 1.
Example 4
This example differs from example 1 only in that the addition of Li as described in step (1) 3 The dispersion speed after N was 1500rpm, and the other conditions and parameters were exactly the same as those in example 1.
Example 5
This example differs from example 1 only in that the addition of Li as described in step (2) 3 The dispersion speed after N was 600rpm, and the other conditions and parameters were exactly the same as those in example 1.
Example 6
This example differs from example 1 only in that the addition of Li as described in step (2) 3 The dispersion speed after N was 1500rpm, and the other conditions and parameters were exactly the same as those in example 1.
Comparative example 1
This comparative example differs from example 1 only in that NMP, conductive carbon black SP, PVDF and Li are directly mixed in step (1) 3 N to produce a first slurry, under otherwise identical conditions and parameters as in example 1.
Comparative example 2
This comparative example differs from example 1 only in that step (2) adds Li 3 After N, the remaining 30% solvent and CNT conductive paste were directly introduced into the blender, and the other conditions and parameters were exactly the same as in example 1.
Comparative example 3
The comparative example is different from example 1 only in that the first slurry is not prepared, the positive pole piece is prepared by coating the second slurry, and other conditions and parameters are completely the same as example 1.
Comparative example 4
This comparative example is different from example 1 only in that the conductive carbon black SP and the carbon nanotubes are directly mixed and added to the slurry in step (2) and other conditions and parameters are exactly the same as those of example 1.
Comparative example 5
This comparative example differs from example 1 only in that the amounts of solvent added in three times in step (3) are 40%, 30%, respectively, and the other conditions and parameters are exactly the same as those in example 1.
And (4) performance testing:
(1) And (3) testing the pole piece by using an SEM (scanning electron microscope), and observing the distribution condition of each component in the plane and the section of the pole piece according to the multiplying power of 2K,5K,1W,3W and 5W to judge whether the conductive agent is agglomerated or not.
(2) The pole piece peel force was tested and the test results are shown in table 1:
TABLE 1
Pole piece SEM test Peel force (Standard > 0.2N)
Example 1 Without agglomeration 0.25
Example 2 Without agglomeration 0.23
Example 3 Slight agglomeration of SP 0.20
Example 4 Slight agglomeration of SP 0.18
Example 5 Small amount of SP agglomeration 0.16
Example 6 Small amount of SP agglomeration 0.15
Comparative example 1 Intermediate agglomeration of SP 0.13
Comparative example 2 Moderate agglomeration of SP and CNT 0.10
Comparative example 3 Moderate agglomeration of SP and CNT 0.06
Comparative example 4 Severe agglomeration of SP and CNT 0.06
Comparative example 5 Severe agglomeration of SP and CNT 0.05
As can be seen from Table 1, the conductive agent of the square lithium-supplement positive electrode plate prepared by the method of the invention has the worst occurrence of only a small amount of agglomeration, the agglomeration of the conductive agent can be avoided by adjusting the dispersion speed, the stripping force of the prepared electrode plate can reach more than 0.15N, and the stripping force of the prepared electrode plate can reach 0.25N by adjusting the dispersion speed.
Compared with the embodiment 1 and the embodiment 3-4, in the process of preparing the first slurry in the step (1), the dispersing speed after the lithium supplement additive is added influences the performance of the prepared positive pole piece, the positive pole piece with excellent performance can be prepared by controlling the dispersing speed at 800-1200 rpm, if the dispersing speed is too high, the energy consumption of stirring equipment is high, the equipment is greatly abraded, the powder is collided by a turntable and washed to the upper layer of the inner wall of a stirrer, the powder is not uniformly mixed, the integrity of particles is damaged by crushing, and if the dispersing speed is too low, the components of the slurry are not uniformly dispersed, so that the effect of mixing and homogenizing the slurry cannot be achieved.
Compared with the embodiment 1 and the embodiment 5-6, in the process of preparing the second slurry in the step (2), the dispersing speed after the lithium supplement additive is added influences the performance of the prepared positive pole piece, the positive pole piece with excellent performance can be prepared by controlling the dispersing speed at 800-1200 rpm, if the dispersing speed is too high, the energy consumption of stirring equipment is high, the equipment is greatly abraded, the powder is collided by a turntable and washed to the upper layer of the inner wall of a stirrer, the powder is not uniformly mixed, the integrity of particles is damaged by crushing, and if the dispersing speed is too low, the components of the slurry are not uniformly dispersed, so that the effect of mixing and homogenizing the slurry cannot be achieved.
Compared with the comparative examples 1 and 1-2, the method disclosed by the invention has the advantages that the slurry is prepared by adopting a multi-step material adding method, the homogenizing time can be shortened by controlling the material adding ratio of each step and the homogenizing condition, the slurry with a good dispersing effect can be prepared, and the performance of the prepared pole piece is further improved.
Compared with the comparative example 3, the embodiment 1 can obtain the results that the coating of the positive electrode slurry with the lithium supplement additive on the aluminum foil of the positive electrode current collector is firstly carried out, and then the coating of the positive electrode slurry with the lithium supplement additive is carried out to prepare the lithium supplement positive electrode plate, so that the electric conductivity of the electrode plate can be improved, the contact resistance between the second coating and the current collector is reduced, the electronic conductivity of the electrode plate is improved, and the good pore distribution and lithium ion channel can be formed in the electrode plate by the double-layer coating slurry for lithium supplement, thereby being beneficial to the electrode plate to absorb the electric liquid and realizing a better lithium ion transmission path.
Compared with the comparative example 4, the invention can improve the performance of the prepared positive pole piece by firstly mixing the conductive agent and the lithium supplement additive and then adding the conductive slurry containing another conductive agent.
Compared with the comparative example 5, in the process of preparing the second slurry, the volume of the solvent added for three times can influence the homogenization effect, and when the positive electrode main material is added at the same time, the amount of the solvent is far larger than that of the solvent added subsequently, so that the positive electrode main material is uniformly distributed, and the performance of the prepared positive electrode plate is improved.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein fall within the scope and disclosure of the present invention.

Claims (43)

1. The preparation method of the lithium-supplement positive pole piece is characterized by comprising the following steps:
(1) Mixing the binder and the conductive agent, adding a part of first solvent, stirring for the first time, adding the rest first solvent and the lithium supplement additive, stirring for the second time, and stirring for the first time in vacuum to obtain first slurry;
(2) Mixing a main positive electrode material, a binder and 65-75% of a second solvent, stirring for three times, adding a conductive agent and a lithium supplement additive, stirring for four times, adding 12-18% of the second solvent, stirring for five times, adding the rest of the second solvent and the conductive slurry, stirring for six times, and then stirring in vacuum for two times to obtain a second slurry;
(3) Coating the first slurry on the surface of a positive current collector, baking for the first time to obtain a first slurry priming coating pole piece, coating the second slurry on the coating of the first slurry priming coating pole piece, and baking for the second time to obtain the lithium-supplement positive pole piece;
wherein, the conductive agent in the step (2) comprises conductive carbon black SP, and the conductive slurry comprises carbon nano tube conductive slurry.
2. The method of claim 1, wherein the binder of step (1) comprises polyvinylidene fluoride.
3. The method of claim 1, wherein the conductive agent of step (1) comprises conductive carbon black SP.
4. The method of claim 1, wherein the first solvent of step (1) comprises azomethylpyrrolidone.
5. The method of claim 1, wherein the step (1) of adding the first solvent comprises spraying.
6. The method according to claim 1, wherein the revolution speed of the one-time stirring in the step (1) is 10 to 20rpm.
7. The method according to claim 1, wherein the dispersion speed of the primary stirring in the step (1) is 150 to 250rpm.
8. The method according to claim 1, wherein the time for one stirring in the step (1) is 20 to 40min.
9. The method of claim 1, wherein the lithium supplement additive of step (1) comprises Li 3 N。
10. The method according to claim 1, wherein the mass ratio of the binder, the conductive agent and the lithium supplement additive in the step (1) is (2-4): (40-44): (52-58).
11. The method according to claim 1, wherein the revolution speed of the secondary stirring in the step (1) is 15 to 25rpm.
12. The method of claim 1, wherein the dispersion speed of the secondary stirring in the step (1) is 800 to 1200rpm.
13. The method of claim 1, wherein the secondary stirring in step (1) is carried out for 20 to 40min.
14. The method according to claim 1, wherein the degree of vacuum in the primary vacuum stirring in the step (1) is not more than-0.085 MPa.
15. The method according to claim 1, wherein the revolution speed of the one vacuum stirring in the step (1) is 20 to 30rpm.
16. The method according to claim 1, wherein the dispersion speed of the primary vacuum stirring in the step (1) is 1200 to 1800rpm.
17. The method of claim 1, wherein the time for the one-time vacuum stirring in the step (1) is 50 to 70min.
18. The preparation method according to claim 1, wherein the positive electrode main material in the step (2) comprises any one of lithium iron phosphate, ternary nickel cobalt manganese material or lithium cobaltate material or a combination of at least two of the materials.
19. The method of claim 1, wherein the binder of step (2) comprises polyvinylidene fluoride.
20. The method of claim 1, wherein the second solvent of step (2) comprises N-methylpyrrolidone.
21. The method of claim 1, wherein the second solvent is added in step (2) by a spray.
22. The method according to claim 1, wherein the revolution speed of the tertiary stirring in the step (2) is 15 to 25rpm.
23. The method of claim 1, wherein the dispersion speed of the three times of stirring in the step (2) is 400 to 600rpm.
24. The method of claim 1, wherein the time for the three times of stirring in the step (2) is 40 to 50min.
25. The method of claim 1, wherein the lithium supplement additive of step (2) comprises Li 3 N。
26. The method according to claim 1, wherein the mass ratio of the positive electrode main material, the binder, the conductive agent and the lithium supplement additive in the step (2) is (95-98): 1.2-1.5): 0.3-0.8): 0.5-0.9.
27. The method according to claim 1, wherein the revolution speed of the four times of stirring in the step (2) is 15 to 25rpm.
28. The method of claim 1, wherein the dispersing speed of the four times of stirring in the step (2) is 800 to 1200rpm.
29. The method according to claim 1, wherein the time for the four times of stirring in the step (2) is 10 to 20min.
30. The method according to claim 1, wherein the revolution speed of the five times of stirring in the step (2) is 20 to 30rpm.
31. The method of claim 1, wherein the dispersing speed of the five times of stirring in step (2) is 1800 to 2200rpm.
32. The method of claim 1, wherein the five times of stirring in step (2) is 10 to 20min.
33. The method according to claim 1, wherein the mass concentration of the conductive paste in the step (2) is 0.4 to 0.6%.
34. The production method according to claim 1, wherein the mass ratio of the conductive agent to the positive electrode main material in the conductive paste of step (2) is (0.4-0.6) to (96-98).
35. The method according to claim 1, wherein the revolution speed of the six times of stirring in the step (2) is 20 to 30rpm.
36. The method of claim 1, wherein the six times of stirring in step (2) are performed at a dispersion speed of 1800 to 2200rpm.
37. The method of claim 1, wherein the six times of stirring in step (2) are carried out for 25 to 35min.
38. The method of claim 1, wherein the vacuum degree of the secondary vacuum stirring in the step (2) is not more than-0.085 MPa.
39. The method according to claim 1, wherein the revolution speed of the secondary vacuum stirring in the step (2) is 20 to 30rpm.
40. The method of claim 1, wherein the dispersion speed of the second vacuum stirring in the step (2) is 1800 to 2200rpm.
41. The method according to claim 1, wherein the time for the second vacuum stirring in step (2) is 40 to 50min.
42. A lithium-supplementing positive pole piece, which is prepared by the method of any one of claims 1 to 41.
43. A lithium ion battery, characterized in that the lithium ion battery comprises the lithium-supplementing positive pole piece of claim 42.
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