CN106784857B - Water-based undercoat current collector for lithium ion battery and preparation method and application thereof - Google Patents

Water-based undercoat current collector for lithium ion battery and preparation method and application thereof Download PDF

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CN106784857B
CN106784857B CN201710012108.6A CN201710012108A CN106784857B CN 106784857 B CN106784857 B CN 106784857B CN 201710012108 A CN201710012108 A CN 201710012108A CN 106784857 B CN106784857 B CN 106784857B
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water
current collector
conductive carbon
undercoat
slurry
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CN106784857A (en
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孔令涌
尚伟丽
方东升
黄少真
胡晓宁
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Shenzhen Dynanonic Co ltd
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Shenzhen Dynanonic Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H01M4/662—Alloys
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • 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

Abstract

The invention provides a preparation method of a lithium ion battery water-based undercoat current collector, which comprises the following steps: preparing water-based primer slurry: mixing a water-based dispersant and water, adding the flaky conductive carbon and the spherical conductive carbon, stirring, and adding a water-based binder to obtain water-based primer slurry; and coating the water-based priming slurry on the surface of the current collector substrate, and drying to form a priming coating to obtain the water-based priming current collector. The water-system base coat current collector has high surface roughness, can improve the peeling strength between the water-system base coat current collector and an active substance, and improves the contact resistance between the water-system base coat current collector and the active substance, thereby reducing the internal resistance of the battery, improving the compaction density and the energy density of the battery and providing possibility for the power endurance of the battery.

Description

Water-based undercoat current collector for lithium ion battery and preparation method and application thereof
Technical Field
The invention relates to a preparation method of a functional conductive current collector of a lithium ion battery, in particular to a water system base coating current collector for the lithium ion battery and a preparation method and application thereof.
Background
A typical electrochemical cell has a cathode and an anode that participate in an electrochemical reaction. To manufacture an electrode, an electrode active material (electroactive material) may be coated on a current collector, which may serve as a positive and negative electrode material of a battery. Maintaining electrical contact between the electrode active material and the conductive current collector is critical to the efficient operation of the electrochemical cell.
As is known, a transition layer, referred to as a "primer" or "undercoat", applied between an electrode active material and a current collector may adhere between the electrode active material and the current collector and provide electrical conduction between the electrode active material and the current collector, thereby reducing contact resistance between the active material and the current collector. Currently, primer pastes have been developed, but many of the existing primers fail to provide good electrical contact between the layers while also improving good adhesion of the electrode active material to the current collector.
Disclosure of Invention
In view of the above, the present invention provides a water-based undercoat current collector for a lithium ion battery, which can improve the good conductivity between the current collector and an electrode active material, and can also improve the adhesion of the electrode active material on the current collector coated with water-based undercoat slurry (i.e., the obtained water-based undercoat current collector), thereby improving the performances of the battery, such as compaction density, energy density, and the like.
In a first aspect, the invention provides a preparation method of a water-based undercoat current collector, which comprises the following steps:
(1) mixing a water system dispersant and water, and uniformly stirring to obtain a mixture A;
(2) adding sheet conductive carbon and spherical conductive carbon into the mixture A, uniformly stirring, and sanding until the D50 of the sheet conductive carbon and the spherical conductive carbon is 20-90 mu m to obtain a mixture B;
(3) adding a water-based binder into the mixture B, and stirring to obtain a water-based base coating slurry for the lithium ion battery, wherein in the water-based base coating slurry, the mass fraction of the water-based dispersant is 0.5-10%, the mass fraction of the flaky conductive carbon is 5-25%, the mass fraction of the spherical conductive carbon is 5-50%, and the mass fraction of the water-based binder is 2-10%;
(4) and (3) taking a current collector substrate, coating the water-based priming slurry on the surface of the current collector substrate, and drying to form a priming coating so as to obtain the water-based priming current collector.
Preferably, the viscosity of the water-based priming slurry is 0.05-8 Pa-s.
Preferably, in the water-based primer slurry, the mass fraction of water is 30-80%. More preferably 40 to 70%.
Preferably, in step (1), the stirring time is 0.5 to 4 hours.
Preferably, in the step (2), the stirring time is 0.5 to 4 hours.
Preferably, in the step (3), the stirring speed is 3000-5000 r/min.
In the invention, in the process of preparing the base coat slurry, the flaky conductive carbon and the spherical conductive carbon are simultaneously used as conductive agents, wherein the flaky conductive carbon can effectively reduce the interface resistance, the spherical conductive carbon can effectively enhance the conductivity and enhance the roughness, and a conductive network structure can be formed together by the interaction of the flaky conductive carbon and the spherical conductive carbon (the flaky conductive carbon forms a conductive network frame, and the spherical conductive carbon is inserted between the layers of the flaky conductive carbon to avoid the aggregation of the flaky conductive carbon or the spherical conductive carbon is fully dispersed among flaky conductive carbon molecules). When the undercoat slurry is coated on a current collector, the improvement of the conductivity between the current collector and an electrode active material is facilitated, the formation of a large-area undercoat with an uneven rough surface is facilitated, the adhesion of an electrode active material on the current collector is facilitated, and more electrode active materials are supported, so that the energy density of a battery is improved, and the internal resistance of the battery is reduced.
In addition, in the process of preparing the base coating slurry, the aqueous dispersant is mixed with water, the conductive agent is added, and the aqueous binder is added at last, so that the problem that the viscosity of the slurry is increased due to the fact that the aqueous binder is added firstly, the influence on the dispersion of the subsequently added flaky and spherical conductive carbon can be avoided, and the stirring time is prolonged.
According to the invention, the mass fractions of the flaky conductive carbon and the spherical conductive carbon in the water-based undercoat slurry are mainly controlled to be 5-25% and 5-50%, respectively, and based on the synergistic effect of a water-based dispersant, a binder and water, the undercoat has proper roughness and proper gaps, so that stable and high-adhesion bearing of an electrode active material on the undercoat of the water-based undercoat current collector is facilitated.
The mass fractions of the spherical conductive carbon and the flaky conductive carbon in the slurry should be controlled within a certain range, if the spherical conductive carbon is too much and the flaky conductive carbon is too little, the spherical conductive carbon can form close packing on the surface of the bottom coating, so that the adhesion of an electrode active material on a water-based bottom coating current collector is influenced, and further the energy density of the battery is influenced; if the amount of the flake conductive carbon is too large and the amount of the spherical conductive carbon is too small, voids in the formed overall structure are too large, the roughness of the undercoat is insufficient, and the adhesion of the electrode active material on the aqueous undercoat current collector is unstable.
Preferably, the mass fraction of the sheet-shaped conductive carbon in the aqueous undercoat slurry is 4 to 15%.
Preferably, the mass fraction of the spherical conductive carbon in the water-based primer slurry is 10-25%. More preferably 12 to 23%.
In the present invention, the mass ratio of the spherical conductive carbon to the flaky conductive carbon is (0.2 to 10): 1. preferably, the mass ratio of the spherical conductive carbon to the flaky conductive carbon is (1-5): 1.
in the step (2), the flake conductive carbon and the spherical conductive carbon which are ground until D50 is 20-90 μm are used as main components for forming the water-based base coating slurry, so that the conductive agent in the particle size range can be well dispersed in the water-based base coating slurry, the base coating performance of the slurry is excellent, the phenomenon that the coating thickness is affected by too large particle size range can be avoided, and the phenomenon that the particle size is too small and the roughness of the formed base coating is insufficient can be avoided.
Preferably, the sheet-like conductive carbon is selected from one or more of graphene, flake graphite, expanded graphite, and KS-6.
Preferably, the spherical conductive carbon is one or more of carbon black conductive agents (SP) such as super P, ketjen black, acetylene black, and 350G.
In the present invention, the graphene includes a single layer of graphene or a plurality of layers of graphene including two or more layers and one hundred layers or less. The monolayer of graphene refers to a sheet of carbon molecules having 1 atomic layer of sp2 bonds. Preferably, the graphene is a multilayer graphene having 2 to 10 layers.
Preferably, the diameter of the graphene is 5-10 μm, and the thickness of the graphene is 10-20 nm.
In an embodiment of the present invention, the flake conductive carbon is graphene, and the spherical conductive carbon is 350G.
In one embodiment of the present invention, the flake conductive carbon is KS-6, and the spherical conductive carbon is ketjen black.
In an embodiment of the present invention, the flake conductive carbon is graphene and expanded graphite, and the spherical conductive carbon is acetylene black and ketjen black.
In one embodiment of the invention, the flake conductive carbon is flake graphite and KS-6, and the spherical conductive carbon is acetylene black and 350G.
Preferably, the aqueous dispersant is one or more of ethanol, Sodium Dodecyl Sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), octylphenyl polyoxyethylene ether (triton X-100), polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG).
In one embodiment of the present invention, the molecular weight of the PEG is 1 to 5 ten thousand.
Preferably, the water-based binder includes one or more of sodium carboxymethylcellulose (CMC), polyvinyl alcohol (abbreviated as PVA), and LA-series aqueous binders (e.g., LA133, LA132, LA135), but is not limited thereto.
More preferably, the mass fraction of the aqueous binder in the aqueous base coating slurry is 2 to 6%. More preferably 3-5%.
In one embodiment of the present invention, the molecular weight of the PVA is 5 to 30 ten thousand.
Preferably, the water-based priming slurry further comprises one or more of a surfactant, a defoaming agent and a stabilizer.
Preferably, the thickness of the primer layer is 0.2 to 10 μm. More preferably 0.5 to 2 μm.
Preferably, the peel strength of the primer layer is 0.05 to 1N. The peeling strength is measured by a universal mechanical testing machine, the peeling force is gradually increased from zero by the universal mechanical testing machine, and the force used when the coating is separated from the fluid substrate is the peeling force of the coating.
Preferably, the current collector substrate is a copper foil or an aluminum foil. Further preferably an aluminum foil.
The preparation method of the water-based undercoat current collector provided by the first aspect of the invention is simple and easy to operate, the preparation time of the undercoat slurry is short, and the undercoat slurry which is uniformly stirred can be easily obtained.
In a second aspect, the invention provides a water-based undercoated current collector prepared by the method of the first aspect of the invention. Wherein the water-based undercoated current collector comprises a current collector substrate and an undercoating layer formed on the current collector substrate. Wherein the undercoat layer comprises a water-based dispersant, a sheet-like conductive carbon, a spherical conductive carbon, and a water-based binder.
In the present application, the flake-shaped conductive carbon and the spherical conductive carbon are uniformly dispersed in an aqueous dispersant and an aqueous binder constituting an undercoat layer slurry, and the undercoat layer formed after drying has a rough surface with irregularities.
The water system primary coating current collector provided by the second aspect of the invention has an uneven rough surface, and when an electrode active substance is coated on the surface of the water system primary coating current collector, the good conductivity between the active substance and the water system primary coating current collector is ensured, and the adhesion and the peeling strength between the subsequent active substance and the water system primary coating current collector can be increased (by about more than 50%).
In a third aspect, the invention provides an electrode plate, which comprises a water-based undercoat current collector and an electrode active substance layer, wherein the water-based undercoat current collector comprises a current collector substrate and an undercoat layer formed on the current collector substrate, and the electrode active substance layer is arranged on the undercoat layer.
Wherein the electrode active material layer includes a positive electrode active material, a conductive agent, and a solvent. The electrode active material layer may further include a binder or the like.
Wherein the electrode active material layer includes a negative electrode active material, a conductive agent, and a solvent. The electrode active material layer may further include a binder or the like.
The anode active material comprises common anode materials such as lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminate and the like. The negative active material includes graphite or the like.
In a fourth aspect, the invention further provides a lithium ion battery, wherein the positive electrode or negative electrode active material is coated on the water-based undercoat current collector, and the lithium ion battery is obtained through coating, tabletting, liquid injection, formation and capacity grading.
The internal resistance of the current collector substrate and the active material is large, so that the migration rate of lithium ions is influenced, and the performance of the lithium ion battery is further influenced. Compared with a simple current collector substrate, the water-based undercoat current collector provided by the invention can reduce the electron transfer resistance between the current collector substrate and an active material based on the action of the undercoat, can reduce the sheet resistance of a battery pole piece by more than 85%, can reduce the alternating current impedance of a formed half battery by more than 40%, and can reduce the internal resistance of a full battery by more than 30%.
More importantly, the special surface structure of the bottom coating in the water system base coat current collector can obviously increase the cohesiveness and the peeling strength between the active substance and the water system base coat current collector (about 50% or more), greatly increase the load degree of the active substance on the water system base coat current collector, improve the compaction density of the battery, increase the energy density of the battery and provide possibility for the power endurance of the battery.
The water-based undercoat current collector provided by the invention can ensure that the compaction density of a battery (such as lithium iron phosphate serving as a positive electrode material) is from 2.2 to 2.3g/cm3Increased to 2.4-2.6g/cm3The energy density of the battery is increased from 115-125wh/kg to 130-140 wh/kg.
Advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the invention.
Drawings
Fig. 1 is a schematic structural diagram of a water-based undercoat current collector provided in embodiment 1 of the present invention;
FIG. 2 is a Scanning Electron Microscope (SEM) photograph of the undercoat on the water-based undercoat current collector obtained in example 1 of the present invention;
fig. 3 is a schematic structural diagram of a positive electrode plate of a battery provided in embodiment 1 of the present invention.
Detailed Description
While the following is a description of the preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Example 1
A preparation method of a water-based undercoat current collector comprises the following steps:
1. adding 60g of PEG into 1400g of deionized water, and stirring in a dispersion tank for 30min to completely dissolve the PEG;
2. adding 180G of graphene (sheet) and 435G of 350G (spherical) into the dispersion tank, stirring for 30min, sanding for 4-5 times by using a sand mill after the graphene (sheet) and the 350G (spherical) are uniformly dispersed until the granularity D50 of the mixture is 20 microns, and stopping sanding;
3. adding 80g of CMC into the dispersion tank in the step 2, and stirring to obtain water-based base coating slurry with the viscosity of about 4 mPas;
4. and coating the obtained water-based priming slurry on the surface of an aluminum foil current collector substrate by adopting a scraper technology, and drying to form a priming coating with the thickness of 1 micron to obtain the water-based priming current collector.
Fig. 1 is a schematic structural view of the water-based undercoating current collector obtained in example 1 of the present invention. In fig. 1, 10 is a copper foil current collector substrate, 20 is a primer layer, and 20 and 10 stacked on 10 together constitute the water-based primer current collector. Further, the peel strength of the undercoat layer was 0.07N.
Fig. 2 is a Scanning Electron Microscope (SEM) photograph of the undercoat layer in the present embodiment, and it can be seen from fig. 2 that the undercoat layer has irregularities, high roughness, and certain voids, which facilitate the adhesion and embedding of the subsequent electrode active material.
Application 1: coating a positive active material (including 5g of lithium iron phosphate (LFP) with a particle size of 0.1 micron, 3g of deionized water, and 7.8g of a conductive liquid, which are mixed to form the positive active material) on the water-based undercoat current collector obtained in the embodiment 1, drying the positive active material at 100 ℃ for 5min, drying the positive active material at 120 ℃ for 2min, and cutting the pieces to obtain the battery positive pole piece. The conductive liquid used was CN-1N/CN-1F Germany nanotechnology Co.
Application 2: manufacturing a half cell: coating a positive active material (including 5g of LFP with a particle size of 0.1 micron, 3g of deionized water and 7.8g of conductive liquid which are mixed to form the positive active material) on the water-based undercoat current collector obtained in the embodiment 1, drying, rolling, punching to obtain a positive pole piece, adhering the obtained positive pole piece on a positive pole shell, using a lithium piece as a negative pole, and pressing to obtain a button cell to obtain the half cell.
Application 3: manufacturing the full cell: laminating and winding the cathode sheet formed by the prepared anode sheet and graphite and a diaphragm to obtain an electric core, arranging the diaphragm between the anode sheet and the cathode sheet, placing the electric core into the accommodating space of the shell, injecting electrolyte, and sealing to obtain the lithium ion battery (namely a full battery, such as a common 18650 battery or a soft package battery)
Fig. 3 is a schematic structural diagram of the positive electrode plate of the battery obtained in embodiment 1 of the present invention. In fig. 3, 10 is a copper foil current collector substrate, 20 is a primer layer, and 20 and 10 laminated on 10 together constitute the water-based primer current collector 100, and 30 is a positive electrode active site. As is apparent from fig. 3, the active material can be sufficiently embedded in the undercoat layer of the water-based undercoat current collector, and the firm adhesion of the active material to the water-based undercoat current collector is achieved by the uneven and high-roughness undercoat layer, thereby increasing the peel strength and the peel difficulty between the water-based undercoat current collector and the active material.
To highlight the technical effect of the invention, the following comparative example 1 was used: the same positive active material was coated on the surface of a common copper foil current collector to prepare a positive electrode plate of a battery, and the performance of the positive electrode plate was tested, and the results are shown in table 1 below.
TABLE 1 comparison of the Properties of inventive example 1 and comparative example 1
Figure GDA0002196102680000081
In table 1, the peel force, the sheet resistance, and the compaction density were measured for the positive electrode sheet; the internal resistance, ac impedance, is a test for half cells, and the energy density is a test for cells.
As is apparent from table 1, the undercoat layer formed by the aqueous undercoat slurry provided by the present invention can modify the current collector substrate well to obtain an aqueous undercoat current collector with high surface roughness, and the aqueous undercoat current collector can improve the conductivity between the aqueous undercoat current collector and the electrode active material, can also provide the viscosity between the aqueous undercoat current collector and the electrode active material, and can improve the compaction density and energy density of the battery, thereby providing a possibility for the power endurance of the battery.
In order to highlight the technical effect of the invention, the following 2 comparative examples are also set for example 1:
comparative example 2
A preparation method of a water-based undercoat current collector comprises the following steps:
1. adding 60g of PEG into 215g of deionized water, and stirring for 30min in a dispersion tank to completely dissolve the PEG;
2. adding 600G of graphene (sheet) and 1200G of 350G (spherical) into the dispersion tank, stirring for 30min, sanding for 4-5 times by using a sand mill after the graphene (sheet) and the 1200G of graphene (spherical) are uniformly dispersed until the granularity D50 of the mixture is 20 microns, and stopping sanding;
3. adding 80g of CMC into the dispersion tank in the step 2, and stirring to obtain water-based primer slurry;
4. and coating the obtained water-based priming slurry on the surface of an aluminum foil current collector substrate by adopting a scraper technology, and drying to form a priming coating so as to obtain the water-based priming current collector.
Comparative example 3
A preparation method of a water-based undercoat current collector comprises the following steps:
1. adding 60g of PEG into 1855g of deionized water, and stirring for 30min in a dispersion tank to completely dissolve the PEG;
2. adding 75G of graphene (sheet) and 85G of 350G (spherical) into the dispersion tank, stirring for 30min, sanding for 4-5 times by using a sand mill after the graphene (sheet) and 85G of graphene (spherical) are uniformly dispersed until the granularity D50 of the mixture is 20 microns, and stopping sanding;
3. adding 80g of CMC into the dispersion tank in the step 2, and stirring to obtain water-based primer slurry;
4. and coating the obtained water-based priming slurry on the surface of an aluminum foil current collector substrate by adopting a scraper technology, and drying to form a priming coating so as to obtain the water-based priming current collector.
The water-based undercoat current collectors obtained in comparative examples 2 and 3 were fabricated into a positive electrode plate, a half cell, and a battery, respectively, in the same manner as in example 1, and tested for relevant properties, with the results shown in table 2 below:
TABLE 2 comparison of the Properties of inventive example 1 and comparative examples 2 and 3
Performance of Comparative example 2 Comparative example 3 Example 1
Peel force (N) 0.3821 0.2991 0.581
Square resistance (omega) 10 21 0.103
Internal resistance (m omega) 21 37,6 9
AC impedance (1000Hz) (omega) 14.6 25 9.27
Compacted density (g/cm)3) 2.32 2.28 2.32
Energy density (wh/kg) 121 118 132
In example 1, the mass fraction of the sheet-shaped conductive carbon was 8.35%, and the mass fraction of the spherical conductive carbon was 20%, whereas in comparative example 2, the mass fraction of the sheet-shaped conductive carbon was 27.8%, and the mass fraction of the spherical conductive carbon was 55.6%, and in comparative example 3, the mass fraction of the sheet-shaped conductive carbon was 3.4%, and the mass fraction of the spherical conductive carbon was 4%.
As can be seen from table 2 above, when the mass fraction of the flake conductive carbon in the aqueous undercoat slurry exceeds 25% or is less than 5%, the peeling force of the undercoat layer obtained when the mass fraction of the spherical conductive carbon exceeds 50% or is less than 5% is low, and the compacted density of the battery electrode sheet is also low, which indicates that in the aqueous undercoat slurry, the flake conductive carbon and the spherical conductive carbon should be controlled within a certain content range, so that the obtained aqueous undercoat current collector has more excellent properties.
Example 2
A preparation method of a water-based undercoat current collector comprises the following steps:
1. adding 72g of triton X-100 into 1485g of deionized water, and stirring in a dispersion tank for 60min to completely dissolve the triton X-100;
2. adding 115g of KS-6 (flaky) and 500g of Keqin black (spherical) into the dispersion tank, stirring for 2 hours, sanding for 4-5 times by using a sand mill after the mixture is uniformly dispersed until the granularity D50 of the mixture is 20-90 mu m, and stopping sanding;
3. adding 90g of LA132 into the dispersion tank in the step 2, and stirring to obtain water-based priming slurry with the viscosity of about 3 mPas;
4. and coating the obtained water-based priming slurry on the surface of a copper foil current collector substrate by adopting a scraper technology, and drying to form a priming coating so as to obtain the water-based priming current collector.
The undercoat layer of the aqueous undercoat current collector obtained in example 2 was coated with a positive active material (a slurry mixture including LFP having a particle size of 0.2 μm, distilled water, and a conductive liquid), and dried to obtain a positive electrode sheet for a battery.
Example 3
A preparation method of a water-based undercoat current collector comprises the following steps:
1. adding 65g of polyvinylpyrrolidone PVP into 1480g of deionized water, and stirring for 45min in a dispersion tank to completely dissolve the polyvinylpyrrolidone;
2. adding 250g of flake graphite (flake graphite) and 350g of acetylene black (spherical) into the dispersion tank, stirring for 2 hours, sanding for 4-5 times by using a sand mill after the flake graphite and the acetylene black are uniformly dispersed until the granularity D50 of the mixture is 20-90 mu m, and stopping sanding;
3. adding 70g of water-based binder LA133 into the dispersion tank in the step 2, and stirring to obtain water-based priming slurry with the viscosity of about 8Pa & s;
4. and coating the obtained water-based priming slurry on the surface of a copper foil current collector substrate by adopting a scraper technology, and drying to form a priming coating so as to obtain the water-based priming current collector.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A preparation method of a water-based undercoat current collector for a lithium ion battery is characterized by comprising the following steps:
(1) mixing a water system dispersant and water, and uniformly stirring to obtain a mixture A;
(2) adding sheet conductive carbon and spherical conductive carbon into the mixture A, uniformly stirring, and then sanding until the D50 of the sheet conductive carbon and the spherical conductive carbon is 20-90 mu m to obtain a mixture B;
(3) adding a water-based binder into the mixture B, and stirring to obtain a water-based base coating slurry for the lithium ion battery, wherein in the water-based base coating slurry, the mass fraction of the water-based dispersant is 0.5-10%, the mass fraction of the flaky conductive carbon is 5-25%, the mass fraction of the spherical conductive carbon is 12-23%, the mass fraction of the water-based binder is 2-10%, and the mass fraction of water is 40-70%;
(4) and (3) taking a current collector substrate, coating the water-based priming slurry on the surface of the current collector substrate, and drying to form a priming coating so as to obtain the water-based priming current collector.
2. The method according to claim 1, wherein the viscosity of the aqueous primer paste is 0.05 to 8 Pa-s.
3. The production method according to claim 1, wherein the sheet-like conductive carbon is selected from one or more of graphene, flake graphite, expanded graphite, and KS-6.
4. The method according to claim 1, wherein the spherical conductive carbon is one or more of super P, Ketjen black, acetylene black, and 350G.
5. The production method according to claim 1, wherein the mass ratio of the flake-shaped conductive carbon to the spherical conductive carbon is 1: (0.5-8).
6. The method of claim 1, wherein the primer layer has a thickness of 0.2 to 10 μm.
7. The method of claim 1, wherein the peel strength of the primer layer is 0.05 to 1N.
8. An aqueous based undercoat current collector, characterized in that the aqueous based undercoat current collector is prepared by the method of any one of claims 1 to 7, and comprises a current collector substrate and an undercoat formed on the current collector substrate.
9. An electrode sheet comprising the water-based undercoated current collector according to claim 8 and an electrode active material layer, the electrode active material being provided on the undercoating layer of the water-based undercoated current collector.
10. A lithium ion battery comprising the electrode sheet of claim 9.
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