CN113380983A - High-compaction negative pole piece, preparation method thereof and lithium ion battery comprising pole piece - Google Patents

High-compaction negative pole piece, preparation method thereof and lithium ion battery comprising pole piece Download PDF

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CN113380983A
CN113380983A CN202110370210.XA CN202110370210A CN113380983A CN 113380983 A CN113380983 A CN 113380983A CN 202110370210 A CN202110370210 A CN 202110370210A CN 113380983 A CN113380983 A CN 113380983A
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pole piece
compaction
negative pole
negative electrode
negative
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马子朋
邱申
张睿成
许梦清
许海萍
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Wanxiang A123 Systems Asia Co Ltd
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Wanxiang Group Corp
Wanxiang A123 Systems Asia 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a high-compaction negative pole piece, a preparation method thereof and a lithium ion battery comprising the same, wherein the high-compaction negative pole piece comprises a negative pole coating and a negative pole current collector; the negative electrode coating comprises a negative electrode active material, an additive, a conductive agent, a suspending agent and a binder, wherein the additive is a high compaction additive. According to the invention, the high compaction additive is added into the negative pole piece, so that the negative pole piece can be stressed to slide in the negative pole rolling process and the artificial graphite particles with irregular shapes are rearranged, and the good flexibility fills the larger gaps in the pole piece so as to improve the pole piece compaction density; secondly, the high-compaction additive has the capacity characteristic equivalent to that of artificial graphite, and does not have negative influence on the capacity of a negative pole piece; finally, the high-compaction additive can effectively reduce the rebound of the rolled negative pole piece and the internal resistance of the battery.

Description

High-compaction negative pole piece, preparation method thereof and lithium ion battery comprising pole piece
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a high-compaction negative pole piece, a preparation method thereof and a lithium ion battery comprising the pole piece.
Background
Lithium ion batteries have gained large-scale use in the last decade since their appearance in the last century. The lithium ion battery commonly used at present mainly comprises a metal oxide anode with the characteristic of lithium intercalation and deintercalation, a graphite cathode, electrolyte and a diaphragm. The manufacturing process of the lithium ion battery generally comprises several important steps of pulping, tabletting, assembling and activating. In actual production, the preparation of the pole piece is taken as the most important link, and the performance and quality of the pole piece are determined.
At present, the most common lithium ion battery negative electrode plate is generally composed of a graphite negative electrode material, a carbon black conductive agent, a binder and a copper foil. In actual production, the negative pole piece is mainly prepared by dispersing and pulping a graphite negative pole, carbon black, sodium carboxymethyl cellulose, styrene butadiene rubber and pure water, coating the obtained product on a copper foil, baking and drying the product, and then rolling the product according to a certain compaction density; and then assembling the positive and negative pole pieces and the diaphragm into a battery cell according to the production flow of the lithium ion soft package battery. And finally, packaging and injecting the battery cell, and preparing the lithium ion battery after formation and activation.
Chinese patent publication No. CN108923018A, published as 20018, 11, month and 30, entitled a method for improving the compaction density of a battery pole piece, and the obtained battery pole piece and a battery disclose that isostatic pressing equipment is adopted to carry out compaction treatment on the battery pole piece so as to improve the compaction density.
Due to the demand on the volume energy density of the lithium ion battery, the pole piece design at the present stage puts higher requirements on the compaction density. The compaction density range is obtained according to parameters such as the real density, the material composition, the hardness and the like of the material, and for the current negative pole piece system, the pole piece compaction density is limited by the compaction density of the graphite material. As for the conventional artificial graphite negative electrode material, the compacted density of the negative electrode pole piece is usually not more than 1.75g/cm due to the influence of the shape, the structure and the like3And other materials are limited by the addition amount and the structural reason of the materials can not provide effective help for improving the pole piece compaction. The compaction density is selected incorrectly when the compaction density is too large or too small, the porosity in the pole piece is higher when the compaction density is too small, the contact of active substance particles is not tight, and the electrochemical performance of the lithium battery is influenced by the large internal resistance of the battery; the excessive compaction density can cause the structural damage of the active substances, no enough gaps exist among particles, the internal repulsive force is excessive, and the thickness rebounds after rolling.
Disclosure of Invention
In order to solve the technical problem, the invention discloses a high-compaction negative pole piece, a preparation method thereof and a lithium ion battery comprising the pole piece. The high anisometric scale graphite additive is added into the negative pole piece, so that the compaction density of the pole piece is improved while the capacity of the negative pole is not influenced, the internal resistance is reduced, and the rebound of the pole piece is reduced.
The specific technical scheme of the invention is as follows: a high compaction negative pole piece comprises a negative pole coating and a negative pole current collector; the negative electrode coating comprises a negative electrode active substance, an additive, a conductive agent, a suspending agent and a binder, and is characterized in that the additive is a high compaction additive, and the high compaction additive is highly anisometric scaly graphite.
According to the invention, the high compaction additive is added into the negative pole piece, so that the negative pole piece can be stressed to slide in the rolling process of the negative pole and the artificial graphite particles with irregular shapes are rearranged, thereby improving the compaction density of the pole piece; secondly, the high-compaction additive has the capacity characteristic equivalent to that of artificial graphite, and does not have negative influence on the capacity of a negative pole piece; finally, the high compaction additive has good flexibility, deforms in the rolling process, fills large gaps in the pole piece, and further improves the compactness of the pole piece.
Preferably, the highly anisometric flaky graphite is anisotropic crystal structure graphite, the gram capacity of the highly anisometric flaky graphite is 350 mAh/g-370 Ah/g, the D50 is 3-9 mu m, and the BET is 9-20 m2The mass of the coating is 2.0-10.0% of the mass of the negative electrode coating.
The added high anisometric crystalline flake graphite has the characteristics of high specific surface area, high crystallinity and low structural defects, the characteristic that the material is easier to slip than other materials is determined by the unique anisometric structure and the high crystallization characteristic, and the slip degree is obviously enhanced by the superfine powder structure and the high specific surface area characteristic.
Preferably, the negative electrode active material is secondary granulated artificial graphite, and accounts for 85-95% of the mass of the negative electrode coating.
Preferably, the suspending agent is CMC and accounts for 1.0-1.5% of the mass of the negative coating.
Preferably, the conductive agent is one or more of Super P, C65, VGCF and SWCNT, and accounts for 0.5-1.0% of the mass of the negative electrode coating.
Preferably, the binder is styrene butadiene rubber emulsion, the solid content is 40-50%, and the mass of the binder accounts for 1.5-2.5% of that of the negative electrode coating.
In addition, the invention discloses a preparation method of the high-compaction negative pole piece, which comprises the following steps:
dissolving a suspending agent into a solvent to prepare a uniform solution;
adding a conductive agent into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
thirdly, dry mixing the high compaction additive and the negative active material, adding the mixture into the conductive mixed liquid obtained in the second step, and uniformly mixing the mixture through high-speed dispersion to obtain a uniform mixture;
adding the binder into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
fifthly, adding a solvent into the mixed slurry obtained in the step IV, uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
coating the negative electrode slurry on a negative electrode current collector, and coating and drying to obtain a coated negative electrode piece;
and seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece.
In the third step, the high compaction additive and the negative active material are subjected to dry mixing treatment to improve the dispersibility of the additive in the negative active material, so that the compaction effect is improved.
Preferably, the density of the coating surface in the step (4) is 250 to 300g/m2。
Finally, the invention discloses a lithium ion battery, which comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm; the high-compaction negative pole piece is characterized in that the negative pole piece is the high-compaction negative pole piece.
Compared with the prior art, the invention has the beneficial effects that:
1. an anisometric scale graphite additive with quite reversible capacity is added in the negative pole piece, and the scale graphite can be stressed to slide in the negative pole rolling process and rearrange the artificial graphite particles with irregular shapes, so that the pole piece compaction density is improved; in addition, the flake graphite has good flexibility, deforms in the rolling process, fills a larger gap in the pole piece, and further improves the compactness of the pole piece.
2. The flake graphite additive has the capacity characteristic equivalent to that of artificial graphite, and has no negative influence on the capacity of a negative pole piece.
3. The technical innovation of the invention can improve the limit compaction density of the current negative pole piece and is helpful for improving the energy density of the lithium ion battery.
4. The additive used in the invention can reduce the internal resistance of the pole piece and reduce the rebound thickness of the pole piece.
Drawings
FIG. 1 is an electron micrograph of highly anisometric exfoliated graphite;
FIG. 2 is a graph of negative pole bounce data;
FIG. 3 is a graph comparing battery capacities;
fig. 4 is a comparison of internal resistances of the batteries.
Detailed Description
The present invention will be further described with reference to the following examples. The raw materials and equipment involved in the invention are common raw materials and equipment in the field if not specified; the methods used in the invention are conventional methods in the field if not specified; the reagents used in the invention are all lithium battery grade.
General example:
a high-compaction negative pole piece comprises a negative pole coating and copper foil; the negative electrode coating comprises a negative electrode active substance, an additive, a conductive agent, a suspending agent and a binder, and is characterized in that the additive is a high compaction additive, and the high compaction additive is highly anisometric scaly graphite.
The crystal structure of the high anisometric scaly graphite has anisotropy, the gram capacity of the high anisometric scaly graphite is 350 mAh/g-370 Ah/g, the D50 is 3 mu m-9 mu m, and the BET is 9-20 m2The mass of the coating is 2.0-10.0% of the mass of the negative electrode coating.
The negative active material is artificial graphite subjected to secondary granulation, and accounts for 85-95% of the mass of the negative coating.
The suspending agent is CMC and accounts for 1.0-1.5% of the mass of the negative coating.
The conductive agent is one or more of Super P, C65, VGCF and SWCNT, and accounts for 0.5-1.0% of the mass of the negative coating.
The binder is styrene-butadiene rubber emulsion, the solid content is 40-50%, and the mass of the binder accounts for 1.5-2.5% of that of the negative electrode coating.
A preparation method of the high-compaction negative pole piece comprises the following steps:
dissolving a suspending agent into a solvent to prepare a uniform solution;
adding a conductive agent into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
thirdly, dry mixing the high compaction additive and the negative active material, adding the mixture into the conductive mixed liquid obtained in the second step, and uniformly mixing the mixture through high-speed dispersion to obtain a uniform mixture;
adding the binder into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
fifthly, adding a solvent into the mixed slurry obtained in the step IV, uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, coating the negative electrode slurry on copper foil, and coating and drying to obtain a coated negative electrode piece;
and seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece.
The density of the coated surface in the step (c) is 250 to 300g/m2。
A lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm; the high-compaction negative pole piece is characterized in that the negative pole piece is the high-compaction negative pole piece.
The first embodiment is as follows:
dissolving 1.3g of a suspending agent into pure water to prepare a uniform solution;
adding 1.0g of Super P into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
③ 2.0g, the gram volume of 370Ah/g, the D50 of 3 μm, the BET of 20m2Dry-mixing and pre-dispersing the high anisometric flaky graphite and 93.5g of secondary granulation artificial graphite, adding the mixture into the conductive mixed solution obtained in the step (II), performing high-speed dispersion by using a double-planet high-speed dispersion machine, and uniformly mixing to obtain a uniform mixture;
adding 2.3g of styrene-butadiene rubber emulsion with the solid content of 40% into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
adding pure water into the mixed slurry obtained in the step (iv), uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, the stepsThe negative electrode slurry is coated on a copper foil with the thickness of 6 mu m, a transfer type coating machine is adopted in the coating process, and the coating surface density is 276g/m2Coating and drying to obtain a coated negative pole piece;
seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece, testing the thickness of the pole piece and calculating the compaction density of the negative pole piece;
and assembling the lithium ion battery by using the high-pressure compacted negative pole piece.
Example two:
dissolving 1.3g of a suspending agent into pure water to prepare a uniform solution;
adding 0.5g of Super P into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
③ 2.0g, the gram volume of 370Ah/g, the D50 of 3 μm, the BET of 20m2Dry-mixing and pre-dispersing the high anisometric scaly graphite and 95g of secondary granulation artificial graphite, adding the mixture into the conductive mixed solution obtained in the step (II), performing high-speed dispersion by using a double-planet high-speed dispersion machine, and uniformly mixing to obtain a uniform mixture;
adding 1.5g of styrene-butadiene rubber emulsion with the solid content of 40% into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
adding pure water into the mixed slurry obtained in the step (iv), uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, coating the negative electrode slurry on a copper foil with the thickness of 6 mu m by adopting a transfer type coating machine in the coating process, wherein the coating surface density is 276g/m2Coating and drying to obtain a coated negative pole piece;
seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece, testing the thickness of the pole piece and calculating the compaction density of the negative pole piece;
and assembling the lithium ion battery by using the high-pressure compacted negative pole piece.
Example three:
dissolving 1.3g of a suspending agent into pure water to prepare a uniform solution;
adding 1.0g of Super P into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
③ 10g, the gram volume of 370Ah/g, the D50 of 3 μm, the BET of 20m2Dry-mixing and pre-dispersing the high anisometric flaky graphite and 85.5g of secondary granulation artificial graphite, adding the mixture into the conductive mixed solution obtained in the step (II), performing high-speed dispersion by using a double-planet high-speed dispersion machine, and uniformly mixing to obtain a uniform mixture;
adding 2.3g of styrene-butadiene rubber emulsion with the solid content of 40% into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
adding pure water into the mixed slurry obtained in the step (iv), uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, coating the negative electrode slurry on a copper foil with the thickness of 6 mu m by adopting a transfer type coating machine in the coating process, wherein the coating surface density is 276g/m2Coating and drying to obtain a coated negative pole piece;
seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece, testing the thickness of the pole piece and calculating the compaction density of the negative pole piece;
and assembling the lithium ion battery by using the high-pressure compacted negative pole piece.
Example four:
dissolving 1.0g of suspending agent into pure water to prepare a uniform solution;
adding 0.5g of Super P into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
③ 2.0g, the gram volume is 350mAh/g, the D50 is 9 μm, the BET is 9m2Dry-mixing and pre-dispersing the high anisometric scaly graphite and 95g of secondary granulation artificial graphite, adding the mixture into the conductive mixed solution obtained in the step (II), performing high-speed dispersion by using a double-planet high-speed dispersion machine, and uniformly mixing to obtain a uniform mixture;
adding 1.5g of styrene-butadiene rubber emulsion with the solid content of 50% into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
adding pure water into the mixed slurry obtained in the step (iv), uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, coating the negative electrode slurry on a copper foil with the thickness of 6 mu m by adopting a transfer type coating machine in the coating process, wherein the coating surface density is 250g/m2Coating and drying to obtain a coated negative pole piece;
seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece, testing the thickness of the pole piece and calculating the compaction density of the negative pole piece;
and assembling the lithium ion battery by using the high-pressure compacted negative pole piece.
Example five:
dissolving 1.5g of a suspending agent into pure water to prepare a uniform solution;
adding 1.0g of Super P into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
③ 10g, the gram volume is 350mAh/g, the D50 is 9 μm, the BET is 9m2Dry-mixing and pre-dispersing the high anisometric scaly graphite and 85g of secondary granulation artificial graphite, adding the mixture into the conductive mixed solution obtained in the step II, performing high-speed dispersion by using a double-planet high-speed dispersion machine, and uniformly mixing to obtain a uniform mixture;
adding 2.5g of styrene-butadiene rubber emulsion with the solid content of 50% into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
adding pure water into the mixed slurry obtained in the step (iv), uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, coating the negative electrode slurry on a copper foil with the thickness of 6 mu m by adopting a transfer type coating machine in the coating process, wherein the coating surface density is 300g/m2Coating and drying to obtain a coated negative pole piece;
seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece, testing the thickness of the pole piece and calculating the compaction density of the negative pole piece;
and assembling the lithium ion battery by using the high-pressure compacted negative pole piece.
Comparative example:
dissolving 1.3g of a suspending agent into pure water to prepare a uniform solution;
adding 1.0g of Super P into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
adding 95.5g of secondary granulation artificial graphite into the conductive mixed liquid, performing high-speed dispersion by using a double-planet high-speed dispersion machine, and uniformly mixing to obtain a uniform mixture;
adding 2.3g of styrene-butadiene rubber emulsion with the solid content of 40% into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
adding pure water into the mixed slurry obtained in the step (iv), uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
sixthly, coating the negative electrode slurry on a copper foil with the thickness of 6 mu m by adopting a transfer type coating machine in the coating process, wherein the coating surface density is 276g/m2Coating and drying to obtain a coated negative pole piece;
seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece, testing the thickness of the pole piece and calculating the compaction density of the negative pole piece;
and assembling the lithium ion battery by using the high-pressure compacted negative pole piece.
The specific scheme is as follows:
negative electrode active material High compaction additive Conductive agent Suspending agent Binder
Comparative example 95.5 0 1 1.3 2.3
Example 1 93.5 2 1 1.3 2.3
Example 2 90.5 5 1 1.3 2.3
Example 3 85.5 10 1 1.3 2.3
Example 4 95 2 0.5 1.0 1.5
Example 5 85 10 1.0 1.5 2.5
The compaction density of the negative pole piece calculated by testing the thickness of the pole piece is as follows:
Figure BDA0003008975310000071
the compaction density calculation method comprises the following steps:
the compacted density is the area density/(pole piece thickness-copper foil thickness), and the copper foil thickness is 6 μm;
as shown in the table above, the negative electrode sheet limit compaction density increases with increasing proportion of high compaction additive. The use of the high compaction additive has an obvious effect on improving the compaction of the negative pole piece.
The additive is subjected to electron microscope characterization to determine the morphology of the additive, and the result is shown in figure 1.
The negative pole piece of the comparative example and the negative pole pieces of the examples 1 to 3 are mixed according to the proportion of 1.75g/cm3And rolling, recording the thickness change of the pole piece from rolling to baking, and calculating the thickness rebound of the pole piece. The anode bounce data of each example and comparative example were obtained. As a result, as shown in fig. 2, the negative electrode tab bounce decreased with the increase in the high compaction additive, and when the high compaction additive was added in an amount exceeding 5g, the negative electrode bounce decreased tendency became gentle. The use of the high-capacity and high-compaction additive has a remarkable effect on reducing the rebound of the negative electrode.
The battery capacity of the negative electrode plate of the comparative example and the negative electrode plates of examples 1 to 3 was tested. Capacity data were obtained for each of the examples and comparative examples. The results are shown in fig. 3, where the cell capacity of each example was not significantly different from that of the comparative example, indicating that the addition of the high compaction additive did not adversely affect the cell capacity.
And (3) respectively assembling the negative pole pieces of the comparative example and the examples 1-3 into a battery, and testing the internal resistance of the battery to obtain the internal resistance data of the battery of each example and comparative example. As a result, as shown in FIG. 4, the internal resistance of the cell decreased with the increase of the high compaction additive, and when the amount of the high compaction additive added exceeded 5g, the tendency of the decrease in the internal resistance of the cell became gentle. The application of the high-volume compaction additive has a remarkable effect on reducing the internal resistance of the battery.
All the data show that the use of the high compaction additive in the negative electrode system meets the requirement of improving the compaction of the negative electrode plate, reduces the rebound of the rolled negative electrode plate and the internal resistance of the battery, and has no negative influence on the battery capacity.
Will be at a level of 1.75g/cm3And assembling the negative pole piece rolled by compaction density, the positive pole and the diaphragm into a battery cell, preparing the 7Ah soft package battery according to the production process of the lithium ion soft package battery well known by the industry, and activating and testing the 7Ah soft package battery.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims (9)

1. A high compaction negative pole piece comprises a negative pole coating and a negative pole current collector; the negative electrode coating comprises a negative electrode active substance, an additive, a conductive agent, a suspending agent and a binder, and is characterized in that the additive is a high compaction additive, and the high compaction additive is highly anisometric scaly graphite.
2. The high-compaction negative electrode plate of claim 1, wherein the highly anisometric flaky graphite is anisotropic crystal structure graphite with a gram capacity of 350mAh/g to 370Ah/g, D50 of 3 to 9 μm, and BET of 9 to 20m2G, in the coating of the negative electrode2.0 to 10.0% by mass.
3. The high-compaction negative electrode piece of claim 1, wherein the negative active material is secondary-granulated artificial graphite accounting for 85-95% of the mass of the negative coating.
4. The high-compaction negative electrode piece of claim 1, wherein the suspending agent is CMC, and accounts for 1.0-1.5% of the mass of the negative electrode coating.
5. The high-compaction negative electrode plate of claim 1, wherein the conductive agent is one or more of Super P, C65, VGCF and SWCNT, and accounts for 0.5-1.0% of the mass of the negative electrode coating.
6. The high-compaction negative electrode plate of claim 1, wherein the binder is styrene-butadiene rubber emulsion, has a solid content of 40-50%, and accounts for 1.5-2.5% of the mass of the negative electrode coating.
7. A preparation method of the high-compaction negative pole piece comprising any one of claims 1 to 6 comprises the following steps:
dissolving a suspending agent into a solvent to prepare a uniform solution;
adding a conductive agent into the solution obtained in the step I, and uniformly mixing to obtain a conductive mixed solution;
thirdly, dry mixing the high compaction additive and the negative active material, adding the mixture into the conductive mixed liquid obtained in the second step, and uniformly mixing the mixture through high-speed dispersion to obtain a uniform mixture;
adding the binder into the uniform mixture obtained in the step (c), and uniformly dispersing at a high speed to obtain mixed slurry;
fifthly, adding a solvent into the mixed slurry obtained in the step IV, uniformly mixing, and removing bubbles in vacuum to obtain negative electrode slurry;
coating the negative electrode slurry on a negative electrode current collector, and coating and drying to obtain a coated negative electrode piece;
and seventhly, rolling the coated negative pole piece to obtain the high-compaction negative pole piece.
8. The method for preparing a high-compaction negative electrode plate of claim 7, wherein the density of the coating surface in the step (c) is 250-300 g/m2。
9. A lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm; the high-voltage compact negative pole piece is characterized in that the negative pole piece is the high-voltage compact negative pole piece in any one of claims 1 to 6.
CN202110370210.XA 2021-04-07 2021-04-07 High-compaction negative pole piece, preparation method thereof and lithium ion battery comprising pole piece Pending CN113380983A (en)

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