CN110071293B - Battery cell and battery, liquid-retaining coating and battery pole piece and preparation method thereof - Google Patents

Battery cell and battery, liquid-retaining coating and battery pole piece and preparation method thereof Download PDF

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Publication number
CN110071293B
CN110071293B CN201910410982.4A CN201910410982A CN110071293B CN 110071293 B CN110071293 B CN 110071293B CN 201910410982 A CN201910410982 A CN 201910410982A CN 110071293 B CN110071293 B CN 110071293B
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liquid
retaining
coating
battery
current collector
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CN110071293A (en
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李景夫
易四勇
林琳
林洋
任超
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Soundon New Energy Technology Co Ltd
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Soundon New Energy Technology 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
    • H01M4/04—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention relates to a battery cell, a battery, a liquid-retaining coating, a battery pole piece and a preparation method thereof, wherein the battery cell comprises two first negative pole pieces, a positive pole piece positioned between the two first negative pole pieces and a diaphragm positioned between the first negative pole pieces and the positive pole piece; the first negative electrode plate comprises a current collector, an active material coating arranged on one surface of the current collector and a liquid-retaining coating arranged on the other surface of the current collector; and the liquid-retaining coating on the first negative electrode plate is far away from the positive electrode plate; the liquid-retaining coating contains a liquid-retaining additive which is at least one selected from linear crystalline polyvinylidene fluoride polymer, butyronitrile and polyvinyl chloride blend powder, polypropylene micropowder and ultra-high molecular weight polyethylene powder. According to the invention, the liquid-retaining coating is arranged on one surface of the first negative electrode plate, which is far away from the positive electrode plate, and the liquid-retaining additive is contained in the liquid-retaining coating, so that the liquid-retaining amount of the battery can be greatly improved, and the multiplying power and the cycle performance are not influenced.

Description

Battery cell and battery, liquid-retaining coating and battery pole piece and preparation method thereof
Technical Field
The invention relates to the technical field of batteries, in particular to a battery cell, a battery pole piece and a preparation method thereof.
Background
With the lack of non-renewable energy sources and the environmental pollution control of the whole society, the development of new energy sources has become an unblockable potential. The lithium ion battery has the advantages of large specific energy, light weight, long cycle life, low self-discharge rate, no memory effect, environmental friendliness and the like, and is widely applied to the fields of electric automobiles and energy storage. With the continuous expansion of the application range of lithium ion batteries, various industries put forward more stringent requirements on the performance of the lithium ion batteries, such as improvement of the battery capacity, increase of the battery cycle life, improvement of the deformation resistance of the batteries, and the like. The soft-package lithium ion battery is a main battery type currently applied to the field of electric automobiles, the electrolyte content in the soft-package lithium ion battery has great influence on the cycle performance and the multiplying power performance of the battery, the performance of the battery can be improved to a certain extent by increasing the liquid retention amount of the soft-package lithium ion battery in the manufacturing process, but in the current lithium ion battery, besides the adsorption effect of a pole piece and a diaphragm on the electrolyte, the free electrolyte can be pumped out of the battery in the battery degassing and forming process, so that the liquid retention amount can not be effectively improved by increasing the amount of the electrolyte injected into the soft-package lithium ion battery.
In order to improve the liquid retention of the battery, the method is mainly realized by gluing and modifying the diaphragm, increasing the surface roughness of the diaphragm and the like. For example, the liquid absorption capacity of the diaphragm is improved by preparing a water-based rubberized diaphragm in a rotary spraying mode, and the method can improve the electrolyte holding amount of the battery core to a certain extent, but the diaphragm rubberizing can increase the ventilation value of the diaphragm, so that the transmission of lithium ions is blocked to a certain extent, and the circulation and the multiplying power performance of the battery are negatively influenced; the method can improve the physical adsorption capacity of the diaphragm to the electrolyte, and can improve the liquid retention capacity of the battery, but the improvement degree is limited, and the requirement of high liquid retention capacity cannot be met.
Disclosure of Invention
Based on this, it is necessary to provide a battery cell that can well improve the liquid retention capacity of the battery without affecting the cycle performance and the rate performance of the battery.
An electric core comprises two first negative electrode pieces, a positive electrode piece positioned between the two first negative electrode pieces, and a diaphragm positioned between the first negative electrode pieces and the positive electrode piece;
the first negative electrode plate comprises a current collector, an active material coating arranged on one surface of the current collector and a liquid-retaining coating arranged on the other surface of the current collector; and the liquid-retaining coating on the first negative electrode plate is far away from the positive electrode plate;
the liquid-retaining coating contains a liquid-retaining additive and ceramic microsphere powder, wherein the liquid-retaining additive is at least one selected from the group consisting of butyronitrile and polyvinyl chloride blend powder, polypropylene micropowder, ultra-high molecular weight polyethylene powder and linear crystalline polyvinylidene fluoride polymer.
Ultra High Molecular Weight Polyethylene (UHMWPE) is an unbranched linear polyethylene having a molecular weight of 150 ten thousand or more.
In an embodiment, the battery cell further comprises a second negative electrode plate, wherein the second negative electrode plate comprises a negative electrode current collector and negative electrode active material coatings respectively arranged on two surfaces of the negative electrode current collector;
the number of the positive pole pieces is m, and m is an integer greater than or equal to 2; the number of the second negative pole pieces is m-1;
the m positive pole pieces and the m-1 second negative pole pieces are alternately arranged, and the diaphragms are arranged between the adjacent positive pole pieces and the adjacent second negative pole pieces.
In one embodiment, the liquid-retaining coating further contains ceramic microsphere powder, wherein the D50 of the ceramic microsphere powder is 0.1-50 μm, and the ceramic microsphere powder is at least one selected from the group consisting of bur stone, silicon dioxide, aluminum oxide, magnesium hydroxide, aluminum oxide, zirconium oxide, magnesium oxide, mullite and cordierite of spherical powder.
D50 is also referred to as median or median particle size, meaning that the particle size is greater than 50% of its particles and less than 50% of its particles.
Another object of the present invention is to provide a battery comprising the above-mentioned cell.
It is still another object of the present invention to provide a liquid-repellent coating for forming the liquid-repellent coating described above.
The liquid-retaining coating comprises the following components in parts by weight:
58-77 parts of solvent, 5-13 parts of anti-settling agent, 85-100.8 parts of liquid retention additive and 0.3-0.9 part of surface wetting agent;
wherein the liquid retention additive is at least one selected from the group consisting of butyronitrile and polyvinyl chloride blend powder, polypropylene micropowder, ultra-high molecular weight polyethylene powder and linear crystalline polyvinylidene fluoride polymer.
In one embodiment, 65-89 parts of ceramic microsphere powder is also contained in the liquid-retaining coating.
Further, the D50 of the ceramic microsphere powder is 0.1-50 mu m, and the ceramic microsphere powder is at least one selected from the group consisting of bur stone, silicon dioxide, aluminum oxide, magnesium hydroxide, aluminum oxide, zirconium oxide, magnesium oxide, mullite and cordierite of spherical powder.
In one embodiment, the solvent is selected from at least one of dimethyl carbonate, acetone, absolute ethyl alcohol, and N-methyl pyrrolidone; and/or
The anti-settling agent is at least one selected from sodium carboxymethyl cellulose, ammonium polyacrylate salt, polyoxyethylene fatty alcohol sulfate and polyglycol ether; and/or
The surface wetting agent is at least one selected from gamma-methacryloxypropyl trimethoxysilane, vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tris (beta-methoxyethoxy) silane, N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, ethylenediamine propyl triethoxysilane and ethylenediamine propyl methyl dimethoxy silane.
The invention also provides a preparation method of the liquid-retaining paint, which comprises the following steps: mixing the raw materials of the liquid-retaining coating according to a formula
In one embodiment, the step of mixing is:
mixing and stirring the solvent, the anti-settling agent and the liquid-retention additive to obtain a first mixed mixture;
and mixing the first mixed solution, the ceramic microsphere powder and the surface wetting agent, and uniformly stirring under a vacuum condition.
A further object of the present invention is to provide a battery pole piece, including a current collector, an active material coating layer disposed on one surface of the current collector, and a liquid-retaining coating layer disposed on the other surface of the current collector;
the liquid-retaining coating is prepared from the liquid-retaining coating or the liquid-retaining coating prepared by the preparation method.
The invention also aims to provide a preparation method of the battery pole piece, which comprises the following steps:
providing a current collector;
coating an active material coating on one surface of the current collector to form an active material coating;
and coating a liquid-retaining coating on the other surface of the current collector to form a liquid-retaining coating, wherein the liquid-retaining coating is the liquid-retaining coating or prepared by adopting the preparation method.
The invention has the following beneficial effects:
1) According to the battery cell, the first negative electrode plate is arranged, and the liquid-retaining coating is arranged on one surface of the first negative electrode plate, which is far away from the positive electrode plate (namely, the negative electrode active coating on the negative electrode plate on the outermost layer of the traditional battery cell is replaced by the liquid-retaining coating), so that the liquid-retaining additive in the liquid-retaining coating has a long-line structure, has good electrolyte-philic performance and is easy to intertwine, and after the electrolyte is injected into the battery, the electrolyte can be fully immersed into the liquid-retaining coating formed by the liquid-retaining coating and is reserved at the molecular gap of the liquid-retaining additive intertwined with each other, and the electrolyte is locked, so that the liquid-retaining capacity of the battery is improved, and therefore, the electrolyte can be timely supplemented when the electrolyte is continuously consumed in the working process of the battery; the negative electrode active material on the negative electrode plate at the outermost layer does not participate in chemical reaction in the battery, so that after the negative electrode active material is changed into a liquid-retaining coating, the liquid-retaining amount of the battery is improved, the performances such as internal resistance, energy density and capacity of the battery are not influenced, and the cycle performance and multiplying power performance of the battery can be greatly improved;
2) The liquid-retaining coating of the battery cell also contains ceramic microsphere powder, the ceramic microsphere powder can improve the hardness of the battery cell, eliminate the problem that the battery cell becomes soft due to the increase of electrolyte in the battery cell, and ensure that the battery cell has high liquid-retaining capacity and can not deform or even be damaged due to external force.
3) The liquid-retaining coating provided by the invention takes the long-line polymer as a liquid-retaining additive, and takes the long-line polymer and ceramic microsphere powder as main components, and can be uniformly coated on a battery pole piece by being matched with other components according to a proportion, so that a uniform liquid-retaining coating is formed, and the binding force with the battery pole piece is good; the electrolyte-retaining additive has a long-line structure, so that the electrolyte-philic additive has good performance, and the molecular structures of the electrolyte-philic additive are easy to intertwine, and after the electrolyte is injected into a battery, the electrolyte-retaining additive can be fully immersed into a liquid-retaining coating formed by the liquid-retaining coating and is reserved at a molecular gap of the intertwined liquid-retaining additive, so that the electrolyte is locked, and the effect of improving the liquid-retaining capacity of the battery is achieved.
4) The preparation method disclosed by the invention is simple in process and easy to realize, basically does not need to modify and adjust the existing equipment, and simultaneously can reduce the manufacturing cost of the battery, so that the preparation method is suitable for large-scale popularization.
Drawings
FIG. 1 is a longitudinal cross-sectional view of a battery pole piece according to an embodiment of the present invention;
fig. 2 is a longitudinal cross-sectional view of a second negative electrode tab according to an embodiment of the invention;
FIG. 3 is a longitudinal cross-sectional view of a positive electrode sheet according to an embodiment of the present invention;
fig. 4 is a longitudinal cross-sectional view of a cell according to an embodiment of the present invention;
fig. 5 is a longitudinal cross-sectional view of a cell according to a comparative example of the present invention;
fig. 6 is a longitudinal sectional view of a cell according to another comparative example of the present invention.
Description of the embodiments
The present invention will be described more fully hereinafter in order to facilitate an understanding of the present invention, and preferred embodiments of the present invention are set forth. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The invention provides a liquid-retaining coating for a battery pole piece, which comprises the following components in parts by weight: 58-77 parts of solvent, 5-13 parts of anti-settling agent, 85-100.8 parts of liquid retention additive and 0.3-0.9 part of surface wetting agent;
wherein the liquid retention additive is at least one selected from the group consisting of a blend powder of butyronitrile and polyvinyl chloride, linear crystalline polyvinylidene fluoride polymer, polypropylene micropowder and ultra-high molecular weight polyethylene powder.
In one embodiment, the liquid-retaining coating further comprises 65-89 parts of ceramic microsphere powder, wherein the ceramic microsphere powder is at least one selected from the group consisting of bur stone, silicon dioxide, aluminum oxide, magnesium hydroxide, aluminum oxide, zirconium oxide, magnesium oxide, mullite, cordierite and the like of spherical powder, and D50 of the ceramic microsphere powder is 0.1-50 mu m.
In one embodiment, the solvent is selected from at least one of dimethyl carbonate, acetone, absolute ethanol, and N-methylpyrrolidone.
In one embodiment, the anti-settling agent is selected from at least one of sodium carboxymethyl cellulose, an ammonium polyacrylate salt, a polyoxyethylene fatty alcohol sulfate salt, and a polyglycol ether.
In one embodiment, the surface wetting agent is selected from at least one of gamma-methacryloxypropyl trimethoxysilane, vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tris (beta-methoxyethoxy) silane, N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, ethylenediamine propyl triethoxysilane, and ethylenediamine propyl methyldimethoxy silane.
Another embodiment of the present invention provides a method for preparing the above-mentioned liquid-retaining coating, including the following steps:
and mixing the raw materials according to the raw material formula of the liquid-retaining coating.
In an embodiment, the steps of mixing the raw materials of the liquid-retaining coating are as follows:
mixing and stirring the solvent, the anti-settling agent and the liquid-retaining additive to obtain a first mixed mixture;
mixing the first mixed solution, the ceramic microsphere powder and the surface wetting agent, and uniformly stirring under a vacuum condition.
In one embodiment, the vacuum conditions are-70 KPa to-90 KPa.
Further, stirring is carried out by adopting a stirrer, and the revolution speed of the stirrer is 10 r/min-15 r/min, and the rotation is 100 r/min-300 r/min.
Specifically, firstly adding a solvent, an anti-settling agent and a liquid-retaining additive into a stirrer, revolving for 10 r-15 r/min, rotating for 100 r-300 r/min, stirring for 30-150 min, then adding ceramic microsphere powder and a surface wetting agent into the stirrer, vacuumizing to-70 KPa to-90 KPa, and continuously stirring for 30-210 min at the same rotating speed to obtain the uniformly dispersed liquid-retaining coating.
A further embodiment of the present invention provides a battery pole piece 10, as shown in fig. 1, comprising a current collector 11, an active material coating 12 disposed on one surface of the current collector 11, and a liquid retaining coating 13 disposed on the other surface of the current collector 11. Wherein the liquid-retaining coating 13 contains a liquid-retaining additive, and the liquid-retaining additive is at least one selected from polyvinylidene fluoride polymer in crystalline form, mixed powder of butyronitrile and polyvinyl chloride, polypropylene micropowder and ultra-high molecular weight polyethylene powder.
Specifically, the raw material of the liquid-retaining coating 13 is the liquid-retaining coating described above or the liquid-retaining coating prepared by the preparation method described above.
In one embodiment, the thickness of the current collector 11 is 4 μm to 12 μm.
In one embodiment, the thickness of the liquid-retaining coating 13 is the same as the thickness of the active 12.
In this embodiment, the current collector 11 is copper foil, and the active material coating 12 is an active material coating including graphite, a conductive agent, an adhesive, and an auxiliary agent. I.e. the battery pole piece 10 is a negative pole piece.
The invention further provides a preparation method of the battery pole piece, which comprises the following steps:
s1, providing a current collector.
The current collector refers to a structure or a part for collecting current, and can be specifically a metal foil, such as an aluminum foil, a copper foil, and the like.
In this embodiment, the current collector is copper foil. It will be appreciated that in other embodiments, the current collector may be a current collector of other materials.
S2, coating an active material coating on one surface of the current collector to form an active material coating.
In this particular embodiment, the active material coating is a negative electrode active material coating.
Specifically, graphite, a conductive agent, an adhesive and an auxiliary agent are mixed, a negative electrode active material coating is prepared through a homogenization process, then the negative electrode active material coating is coated on one surface of a current collector by a coating machine, and after the current collector is dried by a continuous oven, an active material coating is formed.
And S3, coating the liquid-retaining coating on the other surface of the current collector or preparing the liquid-retaining coating by adopting the method to form a liquid-retaining coating.
Specifically, a coating machine is adopted to coat the liquid-retaining coating on the other surface of the current collector, and the liquid-retaining coating is formed after the liquid-retaining coating is dried by a continuous oven.
It will be appreciated that the steps S2 and S3 are not strictly required in order, and the step S2 may be performed first, the step S3 may be performed first, or the operations of the step S2 and the step S3 may be performed simultaneously.
In one embodiment, the method for preparing the battery pole piece further comprises the steps of rolling, slitting and transverse cutting the coiled material after the liquid-retaining coating is formed.
Another embodiment of the present invention provides a battery cell, as shown in fig. 2, the battery cell 100 includes two first negative electrode pieces 110, at least one positive electrode piece 120 located between the two first negative electrode pieces, and a separator 130 located between the first negative electrode pieces 110 and the positive electrode piece 120.
Wherein the first negative electrode tab 110 includes a current collector 111, a negative electrode active material coating 112 and a liquid-retaining coating 113 coated on opposite surfaces of the current collector, respectively; the current collector 111 is copper foil, the liquid-retaining coating 113 contains the liquid-retaining additive, and the liquid-retaining coating 113 on the first negative electrode plate 110 is far away from the positive electrode plate 120.
Specifically, the first negative electrode tab 110 is a battery tab with the current collector being copper foil, or a battery tab prepared by the above method.
As shown in fig. 3, the positive electrode tab 120 includes a positive electrode current collector 121 and positive electrode active material coatings 122 respectively provided on two opposite surfaces of the positive electrode current collector 121.
The separator 130 is selected from at least one of a double-sided ceramic and a single-sided ceramic separator.
The separator 130 includes a base film (not shown) of PE (polyethylene) film or PP (polypropylene) film, which has a porosity of 35% -60%, and a thickness of 9-20 μm, and a ceramic coating (not shown) provided on the base film.
In an embodiment, the battery cell 100 further includes a second negative electrode tab 140. As shown in fig. 4, the second negative electrode tab 140 includes a negative electrode current collector 141 and negative electrode active material coatings 142 respectively provided on both opposite surfaces of the negative electrode current collector 141.
Specifically, the number of the first negative electrode pieces 110 is 2, the number of the positive electrode pieces 120 is m, and m is an integer greater than or equal to 2; the number of the second negative electrode tabs 140 is m-1; the m positive pole pieces 120 and the m-1 second negative pole pieces 140 are alternately arranged, and a diaphragm 130 is arranged between each adjacent positive pole piece 120 and second negative pole piece 140.
Specifically, the first negative electrode plate, the positive electrode plate, the second negative electrode plate and the diaphragm are assembled and packaged in a lamination mode, so that the battery cell is obtained.
The lamination process is to assemble the first negative electrode plate, the positive electrode plate and the second negative electrode plate on a lamination machine through a diaphragm.
Another embodiment of the present invention provides a battery including the above-described battery cell.
Specifically, the assembled and packaged battery cell is subjected to the procedures of liquid injection, infiltration, formation, capacity division and the like to manufacture the battery.
Wherein the electrolyte used for injection comprises PC (polycarbonate), DMC (dimethyl carbonate), EC (ethylene carbonate), EMC (ethylmethyl carbonate) and LiPF 6 (lithium hexafluorophosphate), and the like.
The following are specific examples
Examples
1. Preparation of negative electrode active material coating
Adding graphite, conductive carbon black, sodium carboxymethyl cellulose, water-based styrene-butadiene latex SBR and deionized water into a homogenizing mixer in batches according to the mass ratio of 91.5:6:1.2:1.3:102, sequentially adding deionized water, sodium carboxymethyl cellulose, conductive carbon black, graphite and water-based styrene-butadiene latex SBR, stirring for 300min at revolution of 15r/min before adding graphite, stirring for 150min at revolution of 15r/min after adding graphite at rotation of 800r/min under the vacuum degree of-85 KPa, obtaining uniformly dispersed cathode active material coating after homogenizing, placing the coating into a transfer tank, and stirring at low speed of 15r/min for later use.
2. Preparation of liquid-retaining paint
The preparation method comprises the steps of mixing the burm stone microsphere powder, N-methylpyrrolidone, sodium carboxymethylcellulose, linear crystalline polyvinylidene fluoride polymer and gamma-methacryloxypropyl trimethoxy silane according to the mass ratio: 7.7:5.8:0.8:9.3:0.03, sequentially adding N-methylpyrrolidone, sodium carboxymethylcellulose and linear crystalline polyvinylidene fluoride polymer into a homogenizing mixer, adding the N-methylpyrrolidone, sodium carboxymethylcellulose and linear crystalline polyvinylidene fluoride polymer into the mixer, stirring for 50min at revolution of 10r/min and rotation of 150r/min, adding primary rock microsphere powder and gamma-methacryloxypropyl trimethoxysilane into the mixer, vacuumizing to-90 KPa, continuously stirring for 210min at the same rotating speed, obtaining uniformly dispersed liquid-retaining paint, and placing the paint into a transfer tank for later use at a low speed of 15 r/min.
3. Preparation of battery pole piece
The coating machine for the negative electrode active material coating is firstly coated on one side of a current collector copper foil, after the current collector copper foil is dried by a continuous oven, the liquid-retaining coating is coated on the other side of the copper foil, after the current collector copper foil is dried, rolled, striped and die-cut are carried out on the coiled material after the coating is completed, and a battery pole piece with one side being the negative electrode active material coating and the other side being the liquid-retaining coating is obtained, wherein the thickness of the negative electrode active material coating is the same as the thickness of the liquid-retaining coating, namely the first negative electrode pole piece.
And respectively coating the anode active material coating on two sides of a current collector copper foil by using a coating machine, and drying by using a continuous oven to obtain a second anode plate with anode active material coatings on two surfaces.
And respectively coating the positive electrode active coating of the lithium battery on two sides of the aluminum foil of the current collector by using a coating machine, and drying by using a continuous oven to obtain positive electrode plates with the positive electrode active material coatings on the two surfaces.
4. Preparation of cells and batteries
And assembling the first negative electrode plate, the second negative electrode plate and the positive electrode plate on an automatic lamination machine through a diaphragm, wherein the diaphragm is a double-sided ceramic diaphragm, the base film is PE, the porosity is 45%, and the thickness is 9 mu m, so that the battery cell is prepared. The number of positive pole pieces is 15, the number of first negative pole pieces is 2, the number of second negative pole pieces is 15, the lamination sequence of the first negative pole pieces is that the 1 st layer is the first negative pole pieces, the 2 nd to 30 th layers are that the positive pole pieces and the second negative pole pieces are alternately stacked, the 31 st layer is the first negative pole pieces, one surface of the 1 st layer and the 31 st negative pole pieces, provided with negative pole active material coatings, is opposite to the positive pole pieces of the 2 nd layer and the 30 th layer respectively, and adjacent pole pieces are separated by a diaphragm.
After the preparation of the battery core is finished, the lithium ion battery with high liquid retention is prepared through the procedures of packaging, liquid injection, formation, capacity division and the like.
Examples
Example 2 is substantially the same as example 1 except that the liquid-retaining coating of example 2 comprises the following components in mass ratio: 8.9:7.7:1.3:8.5:0.05.
Examples
Example 3 was substantially the same as example 1 except that each component was simultaneously added to a stirrer and then stirred at revolution of 10r/min, rotation of 150r/min for 260min, and vacuum was turned on for 50min while stirring, and the vacuum degree was the same as example 1, when the liquid-retaining paint was prepared in example 3.
Comparative example 1
Comparative example 1 is substantially the same as example 1 except that the number of first negative electrode tabs in the battery cell of comparative document 1 is 1, and the other one of the first negative electrode tabs is replaced with a second negative electrode tab. Specifically, the lamination sequence in comparative example 1 is: the 1 st layer is a first negative electrode plate, the 2 nd to 31 st layers are positive electrode plates and second negative electrode plates which are alternately stacked, wherein one surface of the 1 st layer of the first negative electrode plate coated with the negative electrode active material coating is opposite to the 2 nd layer of the positive electrode plate, and other procedures are the same as in the embodiment 1, so that the battery cell 200 shown in fig. 5 is obtained, and the battery cell 200 only contains 1 first negative electrode plate 110. Comparative example 2
Comparative example 2 is substantially the same as example 1 except that the battery cell of comparative document 2 has no first negative electrode tab, that is, a second negative electrode tab is used instead of two first negative electrode tabs in example 1, as shown in fig. 6, and the battery cell 300 is formed by alternately stacking second negative electrode tabs 140 and positive electrode tabs 120, and separator 130 is provided between adjacent second negative electrode tabs 140 and positive electrode tabs 120.
Comparative example 3
Comparative example 3 is basically the same as example 1, except that the liquid-retaining coating is coated on two sides of a PE film in comparative example 3, the PE film has a porosity of 9 μm and a porosity of 45%, a double-sided adhesive membrane is manufactured, the manufactured adhesive membrane, 15 positive electrode pieces and 16 second negative electrode pieces are assembled by a lamination machine, a battery cell is manufactured, and the positive electrode pieces and the second negative electrode pieces in the battery cell are alternately stacked in sequence; and then carrying out the subsequent working procedures of liquid injection, infiltration, formation, capacity division and the like to prepare the battery.
The dosage of the liquid-retaining coating is the same as that of the embodiment 1, namely the liquid-retaining coating with the same weight as that of the embodiment 1 is uniformly coated on the surface of the PE film of the comparative example 3, and then the PE film, the positive pole piece and the second negative pole piece are assembled through a lamination machine.
Comparative example 4
Comparative example 4 is essentially the same as example 1 except that no primary stone ceramic microsphere powder was added to the liquid-retaining coating of comparative example 4.
Comparative example 5
Comparative example 5 is substantially the same as example 1 except that comparative example 5 replaces the linear crystalline polyvinylidene fluoride polymer of example 1 with an equal amount of polytetrafluoroethylene micropowder.
Comparative example 6
Comparative example 6 is substantially the same as example 1 except that the mass ratio of the primary particles, the N-methylpyrrolidone, the sodium carboxymethylcellulose, the linear crystalline polyvinylidene fluoride polymer and the gamma-methacryloxypropyl trimethoxysilane in the liquid-retaining coating of comparative example 6 is: 5.0:5.8:0.8:9.3:0.03.
Performance testing
1. Liquid retention and internal resistance test
The cells prepared in examples 1 to 3 and comparative examples 1 to 6 were counted for the liquid absorption rate and the liquid loss rate of each group of cells, and the internal resistance was measured, and the results are shown in table 1 below.
Liquid absorption = liquid absorption/liquid injection 100%; fluid loss rate = fluid loss/fluid injection 100%.
TABLE 1
As can be seen from Table 1, examples 1 to 3 are capable of ensuring a high retention rate and a low liquid loss rate as compared with comparative examples 1 to 6. In example 3, the retention rate of another cell was relatively different from that of the other cell, and the analysis may be that all the raw materials were added to the mixer at the same time in the homogenization process for preparing the retention coating, resulting in uneven slurry mixing and thus a difference in retention rate of the cells. The liquid retention amount of examples 1-3 is obviously increased compared with that of comparative example 2 (conventional cell), and the internal resistance of the battery is not greatly different from that of the conventional cell, namely the liquid retention amount of the battery of examples 1-3 is obviously increased, the liquid loss rate is low, and the internal resistance of the battery is not influenced.
2. Electrochemical performance test
The battery cells prepared in examples 1 to 3 and comparative examples 1 to 6 were subjected to low-temperature, normal-temperature discharge rate performance and normal-temperature cycle performance tests and the capacity retention rate was recorded, and the results are shown in table 2.
TABLE 2
As can be seen from table 2, the batteries of examples 1 to 3 significantly improved in normal temperature rate performance and cycle performance as compared with the battery of comparative example 2 (i.e., conventional battery); meanwhile, the battery of comparative example 1 has only 1 first negative electrode tab, and its rate performance and cycle performance are improved, but its degree of improvement is limited.
As can be seen from the data in table 1 and table 2, the embodiment of the invention can significantly improve the electrolyte retention amount of the battery by arranging two first negative electrode plates, greatly improve the rate capability and the cycle performance of the battery, and can not affect the internal resistance of the battery.
3. Deformation resistance test
1000 cells (ea) prepared by the methods of examples 1-3 and comparative examples 1-4 are fully charged at normal temperature and then are left to stand for 3 hours, then extrusion and drop tests are carried out according to GB/T31485-2015, and the deformation degree (deformation degree judgment standard is shown in table 3) and the experimental passing rate of each group of cells are counted, and the test results are shown in table 4.
TABLE 3 definition criteria for cell deformation
TABLE 4 Table 4
Initial K values of each group of cells of examples 1 to 3 and comparative examples 1 to 4 were tested and recorded, and tracking test of K values was performed on cells passing the extrusion and drop test, each test was performed at three days intervals, and the test results were averaged and shown in table 5.
TABLE 5
Note that: k is mV/day; k (K) 0 Testing after the manufacturing of the battery cell is completed, namely an initial K value of the battery cell; k (K) 1 Testing for the third day after drop or squeeze experiments; k (K) 2 For K 1 Testing the third day after the testing is completed; k (K) 3 For K 2 The third day after the test is completed, and each group of data is the average value of the test of the corresponding group.
As can be seen from the test results of examples 1-3 and comparative examples 2-4, in the examples of the present invention, the addition of the hard ceramic microsphere powder to the liquid-retaining coating significantly improves the deformation resistance of the battery, and after the drop and extrusion test, the deformation degree of the battery is significantly smaller than that of comparative examples 2-4, and in the subsequent K value tracking test, it is also found that the K value of the battery of examples 1-3 is less after the extrusion and drop test due to the small deformation degree, which means that the micro short circuit area inside the battery is less after the drop and extrusion test, and the K value of the battery of comparative examples 2-4 is significantly increased after the drop and extrusion test, which means that the resistance of the battery of comparative examples 2-4 to plastic deformation is poor.
In summary, in embodiments 1 to 3 of the present invention, by providing the first negative electrode plate with the liquid-retaining coating, since the liquid-retaining coating contains the specific liquid-retaining additive and the ceramic microsphere powder, the liquid-retaining amount of the battery can be greatly improved, the multiplying power and the cycle performance can be improved, and the internal resistance of the battery can not be affected; and at the same time, the deformation resistance of the battery can be improved.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (9)

1. The battery cell is characterized by comprising two first negative electrode pieces, a positive electrode piece positioned between the two first negative electrode pieces and a diaphragm positioned between the first negative electrode pieces and the positive electrode piece; the first negative pole piece is the outermost pole piece of the battery cell;
the first negative electrode plate comprises a current collector, an active material coating arranged on one surface of the current collector and a liquid-retaining coating arranged on the other surface of the current collector; and the liquid-retaining coating on the first negative electrode plate is far away from the positive electrode plate;
the liquid-retaining coating contains a liquid-retaining additive and ceramic microsphere powder, wherein the liquid-retaining additive is at least one of butyronitrile and polyvinyl chloride blend powder, polypropylene micropowder, ultra-high molecular weight polyethylene powder and linear crystalline polyvinylidene fluoride polymer; the ceramic microsphere powder is at least one selected from the group consisting of bur stone, silica, magnesium hydroxide, alumina, zirconia, magnesia, mullite and cordierite of spherical powder.
2. The cell of claim 1, further comprising a second negative electrode tab comprising a negative electrode current collector and a negative electrode active material coating disposed on both surfaces of the negative electrode current collector, respectively;
the number of the positive pole pieces is m, and m is an integer greater than or equal to 2; the number of the second negative pole pieces is m-1;
the m positive pole pieces and the m-1 second negative pole pieces are alternately arranged, and the diaphragms are arranged between the adjacent positive pole pieces and the adjacent second negative pole pieces.
3. The cell of claim 1 or 2, wherein the ceramic microsphere powder has a D50 of 0.1-50 μm.
4. A battery comprising the cell of any one of claims 1-3.
5. The liquid-retaining coating is characterized by comprising the following components in parts by weight:
58-77 parts of solvent, 5-13 parts of anti-settling agent, 85-100.8 parts of liquid retention additive, 65-89 parts of ceramic microsphere powder and 0.3-0.9 part of surface wetting agent;
wherein the liquid retention additive is at least one selected from the group consisting of a blend powder of butyronitrile and polyvinyl chloride, polypropylene micropowder, ultra-high molecular weight polyethylene powder and linear crystalline polyvinylidene fluoride polymer; the ceramic microsphere powder is at least one selected from the group consisting of bur stone, silica, magnesium hydroxide, alumina, zirconia, magnesia, mullite and cordierite of spherical powder.
6. The liquid-retaining coating according to claim 5, wherein the ceramic microsphere powder has a D50 of 0.1 μm to 50 μm; and/or
The solvent is at least one selected from dimethyl carbonate, acetone, absolute ethyl alcohol and N-methyl pyrrolidone; and/or
The anti-settling agent is at least one selected from sodium carboxymethyl cellulose, ammonium polyacrylate salt, polyoxyethylene fatty alcohol sulfate and polyglycol ether; and/or
The surface wetting agent is at least one selected from gamma-methacryloxypropyl trimethoxysilane, vinyl triethoxysilane, vinyl trimethoxysilane, vinyl tris (beta-methoxyethoxy) silane, N- (beta-aminoethyl) -gamma-aminopropyl triethoxysilane, mercaptopropyl trimethoxysilane, mercaptopropyl triethoxysilane, ethylenediamine propyl triethoxysilane and ethylenediamine propyl methyl dimethoxy silane.
7. The method for preparing the liquid-retaining paint as claimed in claim 5 or 6, comprising the following steps:
mixing and stirring the solvent, the anti-settling agent and the liquid-retention additive to obtain a first mixed mixture;
and mixing the first mixed solution, the ceramic microsphere powder and the surface wetting agent, and uniformly stirring under a vacuum condition.
8. The battery pole piece is characterized by comprising a current collector, an active material coating arranged on one surface of the current collector and a liquid-retaining coating arranged on the other surface of the current collector;
the liquid-retaining coating is prepared from the liquid-retaining coating according to claim 5 or 6 or the liquid-retaining coating prepared by the preparation method according to claim 7.
9. The preparation method of the battery pole piece is characterized by comprising the following steps:
providing a current collector;
coating an active material coating on one surface of the current collector to form an active material coating;
and coating a liquid-retaining coating on the other surface of the current collector to form a liquid-retaining coating, wherein the liquid-retaining coating is the liquid-retaining coating according to claim 5 or 6 or prepared by the preparation method according to claim 7.
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