CN113745511A - Conductive slurry, preparation method of conductive slurry, negative current collector, negative plate, lithium ion battery cell, lithium ion battery pack and application of negative current collector, negative plate, lithium ion battery cell and lithium ion battery pack - Google Patents

Conductive slurry, preparation method of conductive slurry, negative current collector, negative plate, lithium ion battery cell, lithium ion battery pack and application of negative current collector, negative plate, lithium ion battery cell and lithium ion battery pack Download PDF

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CN113745511A
CN113745511A CN202010481686.6A CN202010481686A CN113745511A CN 113745511 A CN113745511 A CN 113745511A CN 202010481686 A CN202010481686 A CN 202010481686A CN 113745511 A CN113745511 A CN 113745511A
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conductive
lithium ion
ion battery
negative
current collector
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焦一峰
李进
梅骜
何娜
李�根
徐峤
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Gac Aion New Energy Vehicle Co ltd
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Guangzhou Automobile Group 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
    • H01M4/62—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • 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
    • 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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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
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  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

The invention discloses a conductive paste and a preparation method thereof, a negative current collector, a negative plate, a lithium ion cell, a lithium ion battery pack and application thereof. The three conductive agents are used together to form a three-dimensional conductive network, the conductive slurry layer has excellent electronic conductivity and strong bonding force with the copper foil substrate, and meanwhile, the bonding force between the negative electrode slurry layer and the conductive slurry layer is effectively improved, so that the negative electrode slurry layer is not easy to fall off; the prepared lithium ion battery core has good mechanical properties and longer cycle service life, and obtains more excellent cycle stability improvement effect than the conductive slurry containing a single conductive agent.

Description

Conductive slurry, preparation method of conductive slurry, negative current collector, negative plate, lithium ion battery cell, lithium ion battery pack and application of negative current collector, negative plate, lithium ion battery cell and lithium ion battery pack
Technical Field
The invention relates to the field of energy storage devices, in particular to conductive slurry, a preparation method, a negative current collector, a negative plate, a lithium ion battery cell, a lithium ion battery pack and application thereof.
Background
The current collector is one of indispensable components in a lithium ion battery, and it is required not only to carry an active material but also to collect and output a current generated from an electrode active material. Therefore, the current collector with excellent performance is beneficial to reducing the internal resistance of the lithium ion battery and improving the coulombic efficiency, the circulation stability, the rate capability and the charging/discharging efficiency of the battery. An ideal battery current collector should meet several conditions: high conductivity and electrochemical stability, good compatibility with electrode active substances, high binding force, good mechanical strength of materials, low cost and light weight. However, in the practical application process, various problems still exist in different current collector materials, and the above multi-dimensional requirements cannot be completely met.
However, the contact area between the rigid metal current collector and the battery active material particles is limited, the interface resistance is large, and negative effects exist on the battery performance, particularly the performance under the condition of large-current charge and discharge; in addition, because the adhesive strength between the metal current collector and the active material is limited, the active material and the current collector are easy to expand and separate in the continuous charging and discharging process, so that the internal resistance of the battery is further increased, and the cycle life and the safety performance of the battery are influenced. Therefore, improving the bonding strength between the two is an important means for improving the performance of the lithium ion battery.
Wanghangfei, Zhang flood, etc. propose a copper foil-graphene current collector and a preparation method (CN 201710810200). The graphene is directly coated and grown on the surface of the copper foil by using a vapor deposition method, so that the graphene and the copper foil form an integrated composite material, the bonding strength between a current collector and an active substance is improved, repeated expansion and separation from the current collector are prevented, the current collector and the active substance are bonded more tightly, the interface resistance is reduced, the rate discharge performance of a battery is improved, and the cycle service life of the battery is prolonged.
The invention discloses a graphene modified copper foil electrode (CN201810080208) for a silicon-based negative electrode power battery, which comprises a copper foil substrate, wherein a graphene buffer layer and an active material layer are sequentially arranged on the copper foil substrate, the graphene buffer layer grows on the copper foil substrate and forms a current collecting layer together with the copper foil substrate, and the active material layer is a silicon-based alloy negative electrode coating layer. The structure improves the compatibility and the bonding strength between the active material and the current collector, and stabilizes the physical, chemical and electrochemical properties of the active material.
At present, relevant documents and patent reports of carbon-coated copper foils for lithium ion batteries show that graphene is generally applied to preparation of conductive paste for improving the electron conductivity of a coating layer, however, only graphene is used, the coating performance of the paste is deteriorated due to the characteristic that the graphene is difficult to disperse, and in order to meet the requirement of conductivity, a certain requirement is placed on the use amount of the graphene, which greatly increases the cost of the conductive paste. In addition, in the aspect of coating layer thickness, due to the characteristic that graphene is easy to expand, the coating thickness of the prior art cannot meet the requirement of the lithium ion battery negative plate on the thickness, and then the requirement of the power battery on higher volume energy density is difficult to achieve.
In view of the background art, it is mentioned that the tightness of the bonding between the negative active material, especially the silicon system active material, and the copper foil is limited, the peel strength of the pole piece is low, and the resistance of the pole piece is large, so that the cycle attenuation of the battery is rapid. The invention provides a current collector which can effectively improve the performance of a negative plate and improve the cycle performance of a lithium ion battery so as to overcome the defects.
Disclosure of Invention
The first purpose of the invention is to provide conductive paste and a preparation method thereof, and the lithium ion battery prepared from the conductive paste has good electrochemical performance and long cycle life.
The second purpose of the invention is to provide a negative current collector, and the lithium ion battery prepared by the negative current collector has good electrochemical performance and long cycle life.
The third purpose of the invention is to provide a negative plate, and the lithium ion battery cell prepared by the negative plate has good electrochemical performance and long cycle life.
A fourth object of the present invention is to provide a lithium ion cell having good electrochemical performance and long cycle life.
A fifth object of the present invention is to provide a lithium ion battery pack, which includes a lithium ion battery cell with good electrochemical performance and long cycle life.
A sixth object of the present invention is to apply a lithium ion battery pack, which includes a lithium ion battery cell having high energy density and long cycle life, to an automobile, a motorcycle, or a bicycle.
In order to achieve the above object, the present invention provides a conductive paste for coating on a surface of a pretreated copper foil, the conductive paste including a dispersant, a conductive agent, a water-based binder, and a solvent, the conductive agent including a spherical conductive agent, a tubular conductive agent, and a sheet conductive agent.
Further, the dispersing agent is at least one of ethanol, Sodium Dodecyl Sulfate (SDS), polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG), and the mass fraction of the dispersing agent is 0.5-5%.
The aqueous binder is at least one of hydroxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and LA-based binder, such as LA133, and the mass fraction of the aqueous binder is 1-5%.
Further, the spherical conductive agent is selected from at least one of Super P, Ketjen black, acetylene black and 350G, and the mass fraction of the spherical conductive agent is 5-20%.
Further, the tubular conductive agent is selected from at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon fibers.
Further, the sheet-like conductive agent is selected from at least one of mono-graphene, flake graphite, and KS-6.
Further, the mass fraction of the spherical conductive agent is 5-10 times of the mass fraction of the tubular conductive agent, and the mass fraction of the spherical conductive agent is 10-20 times of the mass fraction of the small sheet-shaped conductive agent.
Further, the solid content of the conductive paste is 15-25%, and the viscosity of the conductive paste is 20-100 mPa & s.
Further, the solvent is deionized water, and the conductivity of the solvent is less than or equal to 20 us/cm.
The present invention also provides a method for preparing the conductive paste as described above, the preparation method comprising the steps of: 1) weighing a certain amount of dispersing agent, adding the dispersing agent into a solvent, and stirring to obtain a dispersed solution A, wherein the stirring speed is 20-25 Hz, and the stirring time is 25-40 min; 2) adding a conductive agent into the dispersion solution A, wherein the conductive agent comprises a spherical conductive agent, a tubular conductive agent and a flaky conductive agent, and stirring at a stirring speed of 20-25 Hz for 30-45 min, and then stirring at a high speed of 20-35 Hz for 35-50 min to obtain a mixed solution B; 3) And adding a water-based binder into the mixed solution B, and stirring at a stirring speed of 10-20 Hz for 20-40 min to obtain the required conductive slurry.
The invention also provides a negative current collector which comprises a copper foil base material and a conductive slurry layer, wherein the copper foil base material is pretreated, the conductive slurry layer is formed on one surface or two surfaces of the pretreated copper foil base material, and the conductive slurry layer is formed by coating and drying the conductive slurry according to any one of claims 1 to 9.
Further, the pretreatment method of the copper foil substrate comprises the following steps: preparing a dilute sulfuric acid solution with the mass concentration of 0.1-0.3 mol/L, heating the dilute sulfuric acid solution to 50-65 ℃, drawing and soaking the copper foil substrate to be treated in the dilute sulfuric acid solution, moving the copper foil substrate at a constant speed of 8-15 m/min for 2-5 min for surface treatment, taking out the copper foil substrate, and drying at 75-90 ℃ under the protection of nitrogen to obtain the pretreated copper foil substrate.
Further, the thickness of copper foil base material is 6 ~ 10 um.
Further, the thickness of the conductive paste layer is 0.2-1 um, and the peeling force of the conductive paste layer is 0.06-1.2N.
The invention also provides a negative plate, which comprises a negative current collector and a negative slurry layer, wherein the negative slurry layer is formed on one surface or two surfaces of the negative current collector, and the negative current collector is the negative current collector in any one of claims 11 to 14.
The present invention also provides a lithium ion battery cell, comprising: the negative pole piece, the positive pole piece, the isolating membrane and the packaging bag are arranged, wherein the isolating membrane is arranged between the negative pole piece and the positive pole piece, the packaging bag is made of an aluminum-plastic film composite material, and the negative pole piece, the positive pole piece and the bare cell made of the isolating membrane are arranged in the packaging bag. The positive plate comprises a positive current collector and a positive slurry layer positioned on the positive current collector. The positive current collector is aluminum foil.
The invention also provides a lithium ion battery pack which comprises the lithium ion battery cell.
The lithium ion battery pack is also applied to automobiles, motorcycles or bicycles.
Compared with the prior art, the invention provides the conductive paste which is used for coating the surface of the copper foil after pretreatment, and the conductive paste comprises a dispersing agent, a conductive agent, a water-based adhesive and a solvent, wherein the conductive agent comprises a spherical conductive agent, a tubular conductive agent and a sheet conductive agent. The three conductive agents are used together to form a three-dimensional conductive network, the conductive slurry layer has excellent electronic conductivity and strong bonding force with the copper foil substrate, and meanwhile, the bonding force between the negative electrode slurry layer and the conductive slurry layer is effectively improved, so that the negative electrode slurry layer is not easy to fall off; the prepared lithium ion battery core has good mechanical properties and longer cycle service life, and obtains more excellent cycle stability improvement effect than the conductive slurry containing a single conductive agent.
Drawings
Fig. 1 is a schematic view of the conductive paste of the present invention coated on a copper foil substrate.
Detailed Description
The "ranges" disclosed herein are in the form of lower and upper limits. There may be one or more lower limits, and one or more upper limits, respectively. The given range is defined by the selection of a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this manner are inclusive and combinable, i.e., any lower limit can be combined with any upper limit to form a range. For example, ranges of 60-120 and 80-110 are listed for particular parameters, with the understanding that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present invention, all embodiments and preferred embodiments mentioned herein may be combined with each other to form a new technical solution, if not specifically stated.
In the present invention, all the technical features mentioned herein and preferred features may be combined with each other to form a new technical solution, if not specifically stated.
In the present invention, all the steps mentioned herein may be performed sequentially or randomly, if not specifically stated, but preferably sequentially.
The invention provides a lithium ion battery pack, which comprises a battery module, a circuit board, a shell and the like, wherein the battery module, the circuit board and the like are assembled in the shell to form the lithium ion battery pack, the lithium ion battery pack has various specifications, can be adjusted and designed according to needs, and is not limited in the process, and the assembly mode of the lithium ion battery pack in the prior art can be applied to the invention.
The battery module is composed of a plurality of lithium ion battery cells connected in series and in parallel, and similarly, the battery module has various specifications and can be adjusted and designed according to needs.
The lithium ion battery pack can be applied to an automobile, a motorcycle or a bicycle to provide power for the automobile, the motorcycle or the bicycle.
Various embodiments of the negative current collector, negative plate, lithium ion cell, and lithium ion battery pack of the present invention are described below.
Example 1
(1) Preparation of negative current collector
1) Copper foil base material pretreatment: selecting a copper foil base material with the thickness of 6 microns, preparing a dilute sulfuric acid solution with the mass concentration of 0.1mol/L, heating the dilute sulfuric acid solution to 50 ℃, drawing and soaking the copper foil base material to be treated in the dilute sulfuric acid solution, moving the copper foil at a constant speed of 12m/min for 3min for surface treatment, taking out the copper foil, and drying at 85 ℃ under the protection of nitrogen to obtain the pretreated copper foil base material;
2) preparing conductive slurry: 1. adding 75g polyethylene glycol (PEG) into 1500g deionized water, stirring in a dispersion tank for 35min to completely dissolve; 2. adding 400g of Super P (spherical conductive agent), 80g of single-walled carbon nanotube (tubular conductive agent) and 20g of graphene (flaky conductive agent) into the stirring tank, and stirring in a dispersion tank for 35 min; 3. adding 70g of CMC into the dispersion tank in the step 2, and stirring for 30min to obtain conductive slurry with the viscosity of 30mPa & S;
3) and coating the conductive paste on the surface of the pretreated copper foil base material by adopting a gravure printing technology, controlling the speed of a plate roller, and drying to finally form a conductive paste layer with the thickness of 0.8 um. The coating amount of the conductive paste layer is 0.35g/m2Controlling the specific surface area of the conductive paste layer to be 1.9m after coating2The peel strength is more than or equal to 0.1N.
(2) Preparation of positive plate
LiNi-Co-Mn LiNi as positive electrode active material0.5Co0.2Mn0.3O2Bonding with conductive agent super-P, CNTPVDF (polyvinylidene fluoride) serving as a solvent in a mass ratio of 96.8: 1.5: 0.5: 1.2, adding N-methyl pyrrolidone (NMP), and stirring and mixing uniformly by a vacuum stirrer to obtain the anode active material slurry. And (3) uniformly coating the slurry on two surfaces of a current collector of an aluminum foil (with the thickness of 12 mu m), and drying, cold-pressing and slitting to obtain the positive plate.
(3) Preparation of negative plate
Mixing the negative active material artificial graphite, the Si/C composite material, the conductive agent super-P, CNT, the adhesive Styrene Butadiene Rubber (SBR), the sodium carboxymethylcellulose (CMC) and the polyacrylic acid (PAA) according to a mass ratio of 85: 9: 1.5: 0.5: 2.2: 1.4: 0.4, adding deionized water, and stirring and mixing uniformly by a vacuum stirrer to obtain the cathode slurry. And (3) uniformly coating the negative electrode slurry on two surfaces of the negative electrode current collector (with the total thickness of 7.6um), and drying, cold pressing and slitting to obtain the negative electrode sheet.
(4) Preparation of lithium ion cell
The lithium ion battery comprises a positive plate, a negative plate, an isolating film, an aluminum-plastic film composite material and a packaging bag, wherein the isolating film (with the thickness of 15 microns) is arranged between the positive plate and the negative plate, a square naked battery cell is prepared in a winding mode, the packaging bag is made of the aluminum-plastic film composite material, the naked battery cell is packaged in the packaging bag to obtain the naked battery cell, and the naked battery cell is subjected to procedures of baking, dewatering, liquid injection, sealing, standing, formation, degassing packaging, capacity grading and the like to obtain the lithium ion battery cell.
It should be noted that, in this embodiment, the square bare cell is prepared by winding, of course, in other embodiments, the bare cell may also be prepared by lamination, or the bare cell may also be prepared into other shapes, such as a cylinder or an ellipse, that is, the conventional preparation method of the lithium ion cell may be applied to the present invention, and is not limited herein.
Example 2
The negative current collector, the positive plate, the negative plate and the lithium ion battery cell were prepared according to the method described in example 1, the only difference being that the spherical conductive agent added in the preparation of the conductive paste was ketjen black.
Example 3
The negative electrode current collector, the positive plate, the negative plate and the lithium ion battery cell were prepared according to the method described in example 1, with the only difference that the dispersant added in the preparation of the conductive paste was Sodium Dodecyl Sulfate (SDS).
Example 4
The negative electrode current collector, the positive plate, the negative plate and the lithium ion battery cell were prepared according to the method described in example 1, except that the amount of the spherical conductive agent Super P added in the preparation of the conductive paste was 500 g. .
Example 5
The negative current collector, the positive plate, the negative plate and the lithium ion battery cell were prepared according to the method described in example 1, the only difference being that the amount of the tubular conductive agent single-walled carbon nanotube added during the preparation of the conductive paste was 100 g.
Comparative example 1
The negative current collector, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, the only difference is that no conductive slurry layer is arranged, and the negative slurry layer is directly coated on the copper foil substrate.
Comparative example 2
The negative current collector, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the tubular conductive agent single-walled carbon nanotube is not added during the preparation of the conductive slurry.
Comparative example 3
The negative current collector, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the sheet-shaped conductive agent graphene is not added during the preparation of the conductive slurry.
Comparative example 4
The negative current collector, the positive plate, the negative plate and the lithium ion battery cell are prepared according to the method in the embodiment 1, and the only difference is that the copper foil substrate is not pretreated when the negative current collector is prepared.
Comparative example 5
The negative electrode current collector, the positive plate, the negative plate and the lithium ion battery cell were prepared according to the method described in example 1, except that the amount of the spherical conductive agent Super P added in the preparation of the conductive paste was 100 g.
The above examples and comparative examples were tested for lithium ion battery performance:
the lithium ion batteries obtained in the above examples and comparative examples were charged to 4.25V at a constant current of 1C, then charged at a constant voltage to a current of 0.05C, and then discharged to 2.75V at a constant current of 1C in a thermostat at 25C, and thus charge/discharge cycles were performed, and the capacity retention ratio after 200 cycles of the batteries was recorded.
The lithium ion battery 200-cycle capacity retention ratio (%) -200-cycle discharge capacity/1-cycle discharge capacity 100%.
The data of the cycle capacity retention rate of the lithium ion cells in the examples 1 to 5 and the comparative examples 1 to 5 are shown in Table 1.
TABLE 1 retention of circulating capacity of each of the examples and comparative examples
Figure BDA0002514394590000091
From comparative example 1 and examples 1 to 5, it is known that the cycle performance of a lithium ion battery can be effectively improved by using the negative electrode current collector.
As can be seen from comparative examples 2-3 and example 1, the electronic conductivity of the conductive paste layer is affected by reducing the influence of any type of conductive agent, and the three-dimensional conductive network formed by adding the three types of conductive agents can improve the cycle performance of the lithium ion battery 1C/1C, as shown in FIG. 1.
As can be seen from comparative example 4 and examples 1 to 5, the surface roughness of the copper foil substrate is enhanced by the pretreatment of the copper foil substrate, the binding force between the conductive slurry layer and the copper foil substrate is enhanced, and the step is finally beneficial to improving the electrochemical performance of the battery.
From comparative example 5 and examples 1 to 5, it is clear that the ratio of the spherical, tubular and sheet-like conductive agents has a certain influence on the performance of the carbon-coated copper foil material, and if the ratio is out of the range specified in the claims, the performance of the lithium ion battery is finally deteriorated.
According to the invention, the conductive slurry is coated on the copper foil substrate, and the conductive slurry layer can enhance the binding force between the copper foil substrate and the negative electrode slurry in a manner of increasing the specific surface area of the copper foil substrate. The solidified conductive slurry layer is more closely combined with the copper foil substrate and the negative slurry layer respectively, and the negative current collector coated with the conductive slurry is adopted as the negative current collector of the lithium ion battery cell, so that the peel strength of the pole piece can be effectively improved, and the powder falling problem of the negative pole piece caused by insufficient binding power in the processing and transferring process is reduced. The conductive slurry layer can not generate the insertion and the separation of lithium ions in the charge and discharge process of the negative plate, can not generate volume expansion and contraction per se, and can also provide buffer for the expansion and the contraction of a negative active material in the negative slurry. Therefore, the phenomenon that the negative active material is separated from the foil due to volume expansion and contraction in the charge and discharge processes can be effectively avoided.
In addition, when the conductive paste is prepared, the spherical conductive agent, the tubular conductive agent and the flaky conductive agent are adopted simultaneously, the advantages of the spherical conductive agent, the tubular conductive agent and the flaky conductive agent are fully exerted, the flaky conductive agent can reduce the interface resistance, the spherical conductive agent can enhance the surface roughness of the conductive paste layer while enhancing the conductive agent, the tubular conductive agent has a large length-diameter ratio, the spherical conductive agent and the flaky conductive agent can be connected in series, and the integral conductive capability of the coating is improved. As shown in fig. 1, the three interact to form a three-dimensional conductive network, which reduces the impedance of the negative plate and reduces the voltage drop inside the lithium ion battery cell.
Compared with the prior art, the invention provides the conductive paste which is used for coating the surface of the copper foil after pretreatment, and the conductive paste comprises a dispersing agent, a conductive agent, a water-based adhesive and a solvent, wherein the conductive agent comprises a spherical conductive agent, a tubular conductive agent and a sheet conductive agent. The three conductive agents are used together to form a three-dimensional conductive network, the conductive slurry layer has excellent electronic conductivity and strong bonding force with the copper foil substrate, and meanwhile, the bonding force between the negative electrode slurry layer and the conductive slurry layer is effectively improved, so that the negative electrode slurry layer is not easy to fall off; the prepared lithium ion battery core has good mechanical properties and longer cycle service life, and obtains more excellent cycle stability improvement effect than the conductive slurry containing a single conductive agent.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.

Claims (18)

1. The conductive paste is characterized by being applied to the surface of a copper foil after pretreatment, and comprising:
a dispersant;
a conductive agent comprising a spherical conductive agent, a tubular conductive agent, and a sheet conductive agent;
an aqueous adhesive; and
a solvent.
2. The conductive paste according to claim 1, wherein the dispersant is at least one of ethanol, Sodium Dodecyl Sulfate (SDS), polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG), and the mass fraction of the dispersant is 0.5% to 5%.
3. The conductive paste according to claim 1, wherein the water-based binder is at least one of a hydroxymethylcellulose (CMC), a polyvinyl alcohol (PVA) and a LA-based binder, and the mass fraction of the water-based binder is 1% to 5%.
4. The conductive paste according to claim 1, wherein the spherical conductive agent is at least one selected from Super P, Ketjen black, acetylene black and 350G, and the mass fraction of the spherical conductive agent is 5-20%.
5. The conductive paste according to claim 1, wherein the tubular conductive agent is selected from at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and conductive carbon fibers.
6. The conductive paste according to claim 1, wherein the sheet-like conductive agent is selected from at least one of mono-graphene, flake graphite, and KS-6.
7. The conductive paste according to claim 1, wherein the mass fraction of the spherical conductive agent is 5 to 10 times that of the tubular conductive agent, and the mass fraction of the spherical conductive agent is 10 to 20 times that of the small sheet-like conductive agent.
8. The conductive paste according to claim 1, wherein the solid content of the conductive paste is 15 to 25%, and the viscosity of the conductive paste is 20 to 100 mPas.
9. The conductive paste according to claim 1, wherein the solvent is deionized water, and the conductivity of the solvent is less than or equal to 20 us/cm.
10. A method for preparing the electroconductive paste according to any one of claims 1 to 9, comprising the steps of:
1) weighing a certain amount of dispersing agent, adding the dispersing agent into a solvent, and stirring to obtain a dispersed solution A, wherein the stirring speed is 20-25 Hz, and the stirring time is 25-40 min;
2) adding a conductive agent into the dispersion solution A, wherein the conductive agent comprises a spherical conductive agent, a tubular conductive agent and a flaky conductive agent, and stirring at a stirring speed of 20-25 Hz for 30-45 min, and then stirring at a high speed of 20-35 Hz for 35-50 min to obtain a mixed solution B;
3) and adding a water-based binder into the mixed solution B, and stirring at a stirring speed of 10-20 Hz for 20-40 min to obtain the required conductive slurry.
11. An anode current collector, comprising:
the copper foil base material is pretreated; and
a conductive paste layer formed on one or both surfaces of the copper foil substrate after pretreatment, the conductive paste layer being formed by coating and drying the conductive paste according to any one of claims 1 to 9.
12. The negative electrode current collector of claim 11, wherein the copper foil substrate is pretreated by: preparing a dilute sulfuric acid solution with the mass concentration of 0.1-0.3 mol/L, heating the dilute sulfuric acid solution to 50-65 ℃, drawing and soaking the copper foil substrate to be treated in the dilute sulfuric acid solution, moving the copper foil substrate at a constant speed of 8-15 m/min for 2-5 min for surface treatment, taking out the copper foil substrate, and drying at 75-90 ℃ under the protection of nitrogen to obtain the pretreated copper foil substrate.
13. The negative electrode current collector of claim 11, wherein the copper foil substrate has a thickness of 6 to 10 um.
14. The negative electrode current collector of claim 11, wherein the thickness of the conductive paste layer is 0.2-1 um, and the peel force of the conductive paste layer is 0.06-1.2N.
15. A negative plate is characterized by comprising a negative current collector and a negative slurry layer, wherein the negative slurry layer is formed on one surface or two surfaces of the negative current collector, and the negative current collector is the negative current collector as claimed in any one of claims 11 to 14.
16. A lithium ion battery cell, comprising:
the negative electrode sheet of claim 15;
a positive plate;
the isolating film is arranged between the negative plate and the positive plate; and
the packaging bag is made of an aluminum-plastic film composite material, and the negative pole piece, the positive pole piece and the bare cell made of the isolating film are arranged in the packaging bag.
17. A lithium ion battery pack, characterized in that it comprises a lithium ion cell according to claim 16.
18. Applying the lithium ion battery pack of claim 17 to an automobile, motorcycle, or bicycle.
CN202010481686.6A 2020-05-29 2020-05-29 Conductive slurry, preparation method of conductive slurry, negative current collector, negative plate, lithium ion battery cell, lithium ion battery pack and application of negative current collector, negative plate, lithium ion battery cell and lithium ion battery pack Pending CN113745511A (en)

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