CN114639922B - Lithium ion battery diaphragm and lithium ion battery - Google Patents
Lithium ion battery diaphragm and lithium ion battery Download PDFInfo
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- CN114639922B CN114639922B CN202210378108.9A CN202210378108A CN114639922B CN 114639922 B CN114639922 B CN 114639922B CN 202210378108 A CN202210378108 A CN 202210378108A CN 114639922 B CN114639922 B CN 114639922B
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/426—Fluorocarbon polymers
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/431—Inorganic material
- H01M50/434—Ceramics
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a lithium ion battery diaphragm and a lithium ion battery, which comprise a base film, wherein at least one side of the base film is provided with a coating, the raw material of the coating comprises a first slurry and a second slurry, wherein: the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent and 2-7 parts of a pore-forming agent; the second slurry comprises the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder and 35-70 parts of water. According to the invention, the pore-forming agent is added into the slurry to perform pore-forming on the coating, so that the pore size and the distribution consistency of the diaphragm are improved, and the problem of blocking an ion channel due to the compact coating is solved; by adopting the water-based PVDF and the ceramic mixed coating, the adhesive property and the liquid retention property of the diaphragm are met, and the safety performance of the battery cell can be improved.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery diaphragm and a lithium ion battery.
Background
As a new green energy, the lithium ion battery has the advantages of high working voltage, high energy density, small self-discharge, long cycle life, light weight and the like, and is widely applied to the fields of electronic communication, transportation and the like. The lithium ion battery mainly comprises an anode, a cathode, electrolyte, a diaphragm and the like. The diaphragm plays a crucial role in the performance of the lithium ion battery, the capacity, the cycle performance, the high temperature resistance, the safety performance and the like of the battery are closely related to the performance of the diaphragm, and the development of a new diaphragm material and the improvement of the performance of the diaphragm are necessary requirements of future high-energy and high-power batteries.
At present, the coating diaphragm has the advantages of improving the interface of a pole piece, improving the flatness of a battery core, and improving the liquid retention capacity and the safety performance, and becomes one of the future diaphragm development directions. The coated membrane is mainly coated with a material for improving the performance on one side or two sides of a base membrane in a coating mode. The PVDF coating process mainly includes oil coating and water coating. The oil coating process requires a large amount of organic solvents, and is environmentally friendly and costly. The water-based coating mainly adopts a coating process using water as a solvent, has little pollution to the environment, and is the development direction of mass production of PVDF coating membranes. Specifically, the water-based coating is mainly characterized in that PVDF powder is blended into water to prepare turbid liquid, and the turbid liquid is transferred to a base material to form a coating through processes such as micro gravure, spraying and the like. However, the coating prepared by the preparation process is compact, and easily blocks an ion channel, so that the performance of the battery is influenced.
Disclosure of Invention
The invention mainly aims to provide a lithium ion battery diaphragm and a lithium ion battery, and aims to solve the problem that a coating prepared by a water-based coating process is compact.
In order to achieve the above object, the present invention provides a lithium ion battery separator, which includes a base film, at least one side of the base film is provided with a coating, and raw materials of the coating include a first slurry and a second slurry, wherein:
the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent and 2-7 parts of a pore-forming agent;
the second slurry comprises the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder and 35-70 parts of water.
Optionally, in the coating, the weight ratio of the PVDF powder to the ceramic powder is 1: (2-6).
Optionally, the coating has a thickness of 1-5 μm; and/or the presence of a gas in the atmosphere,
the thickness of the base film is 5-20 μm; and/or the presence of a gas in the gas,
the porosity of the base film is 20-70%.
Optionally, the ceramic powder comprises at least one of alumina, magnesia, zirconia, zinc oxide, titania, silica, aluminum hydroxide, calcium chloride, calcium carbonate nanoparticles; and/or the presence of a gas in the atmosphere,
the pore-forming agent comprises at least one of ammonium bicarbonate, ammonium carbonate and ammonium chloride; and/or the presence of a gas in the gas,
the first thickening agent and the second thickening agent are respectively and independently selected from at least one of carboxymethyl cellulose, hydroxymethyl cellulose, bentonite and attapulgite clay; and/or the presence of a gas in the atmosphere,
the first aqueous binder and the second aqueous binder are respectively and independently selected from at least one of acrylic polymer and polyurethane binder.
Optionally, the ceramic powder has a specific surface area of 4-15m 2 The grain diameter is 0.2-8 mu m.
Optionally, the first slurry further comprises a first dispersant, and the weight part of the first dispersant added is not higher than 1 part per 6-11 parts of PVDF powder; and/or the presence of a gas in the gas,
the first slurry also comprises an adhesion promoter, and the weight part of the adhesion promoter added is not higher than 1 part per 6-11 parts of PVDF powder; and/or the presence of a gas in the atmosphere,
the second slurry also comprises a second dispersing agent, and the weight part of the second dispersing agent added is not higher than 1 part per 60-75 parts of the ceramic powder; and/or the presence of a gas in the gas,
the second slurry also comprises a wetting agent, and the weight part of the wetting agent added is not higher than 0.3 part per 60-75 parts of the ceramic powder.
Optionally, the first dispersant comprises at least one of polyvinyl alcohol, polyacrylic alcohol, hexadecylbenzene sulfonic acid, polyethylene glycol, modified polyacrylic acid, carboxylated modified styrene-butadiene latex, polyacrylonitrile-modified copolymer, polyacrylamide, polyvinyl acetamide, ammonium polyacrylate, polyether derivatives, and polycarboxylate; and/or the presence of a gas in the atmosphere,
the second dispersant comprises at least one of polyvinyl alcohol, polyacrylic alcohol, hexadecyl benzene sulfonic acid, polyethylene glycol, modified polyacrylic acid, carboxylated modified styrene-butadiene latex, polyacrylonitrile modified copolymer, polyacrylamide, polyvinyl acetamide, ammonium polyacrylate, polyether derivative and polycarboxylate.
Optionally, the wetting agent comprises at least one of a fluoroalkyl methoxy ether alcohol, a fluoroalkyl ethoxy ether alcohol, an alkylphenol ethoxylate, a fatty alcohol ethoxylate, and a fatty acid ethoxylate.
Optionally, the base film is made of polyethylene, polypropylene/polyethylene/polypropylene, polyimide, polyvinylidene fluoride, or non-woven fabric.
The invention further provides a lithium ion battery, which comprises a positive pole piece, a lithium ion battery diaphragm and a negative pole piece which are sequentially stacked, wherein the lithium ion battery diaphragm is the lithium ion battery diaphragm.
According to the technical scheme provided by the invention, the pore-forming agent is added into the slurry to perform pore-forming on the coating, so that the pore size and the distribution consistency of the diaphragm are improved, and the problem that the ion channel is blocked due to the compact coating is solved; by adopting the water-based PVDF and the ceramic mixed coating, the adhesive property and the liquid retention property of the diaphragm are met, and the safety performance of the battery cell can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an embodiment of a lithium ion battery separator according to the present invention.
The reference numbers illustrate:
| reference numerals | Name (R) | Reference numerals | Name(s) |
| 1 | |
2 | Coating layer |
The implementation, functional features and advantages of the present invention will be further described with reference to the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments.
It should be noted that those whose specific conditions are not specified in the examples were performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
At present, the coating diaphragm has the advantages of improving the interface of a pole piece, improving the flatness of a battery core, and improving the liquid retention capacity and the safety performance, and becomes one of the future diaphragm development directions. The coated membrane is mainly coated with a material for improving performance on one side or two sides of a base membrane in a coating mode. The PVDF coating process mainly includes oil coating and water coating. The oil coating process requires a large amount of organic solvents, and is environmentally friendly and costly. The water-based coating mainly adopts a coating process using water as a solvent, has little pollution to the environment, and is the development direction of mass production of PVDF coating membranes. Specifically, the water-based coating is mainly characterized in that PVDF powder is blended into water to prepare turbid liquid, and the turbid liquid is transferred to a substrate to form a coating through processes such as micro gravure and spraying. However, the coating prepared by the preparation process is compact, and easily blocks an ion channel, so that the performance of the battery is influenced.
In view of this, the present invention provides a lithium ion battery, which includes a positive electrode plate, a lithium ion battery diaphragm and a negative electrode plate, which are sequentially stacked. The invention mainly aims at improving a lithium ion battery diaphragm and provides the lithium ion battery diaphragm capable of preventing an ion channel from being blocked due to the compactness of a coating 2. Fig. 1 is a specific embodiment of a lithium ion battery separator according to the present invention.
Referring to fig. 1, the lithium ion battery separator includes a base film 1, at least one side of the base film 1 is provided with a coating layer 2, raw materials of the coating layer 2 include a first slurry and a second slurry, wherein: the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF (polyvinylidene fluoride) powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent and 2-7 parts of a pore-forming agent; the second slurry comprises the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder and 35-70 parts of water.
All of the above materials are commercially available. Wherein the description relating to "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Taking the first thickener and the second thickener as an example, the first thickener and the second thickener are only used for distinguishing specific types of thickeners added into the two kinds of slurry, namely, the thickener used in the first slurry and the thickener in the second slurry can be the same type of thickener or different types of thickeners, and the two thickeners are respectively and independently selected when selecting materials. Likewise, the first aqueous binder and the second aqueous binder may be the same aqueous binder or may be different types of aqueous binders.
According to the technical scheme provided by the invention, the pore-forming agent is added into the slurry to form pores on the coating 2, the pores formed by the pore-forming agent are consistent in size and uniform in distribution, the pore size and the distribution consistency of the diaphragm are effectively improved, the defect that the coating 2 prepared by the traditional PVDF coating process is too compact is overcome, and the problem that the coating 2 is more compact and blocks an ion channel is effectively solved; through adopting aqueous PVDF and pottery to mix and scribble, improved the intensity of diaphragm on the one hand, can prevent effectively that the diaphragm from punctureing, promoted the security performance of electric core, on the other hand, aqueous PVDF and pottery all have stronger liquid retention performance, ensured the liquid retention performance of diaphragm, in addition, setting up of coating 2 makes bonding effect better between just/negative pole and the diaphragm, can bond into an organic whole each other for the shaping degree of electric core is better, and the outward appearance is more level and smooth.
Specifically, in the coating 2, the weight ratio of the PVDF powder to the ceramic powder is 1: (2-6); in this embodiment, the first slurry and the second slurry in the above ratio are mixed, and the prepared coating 2 can well balance the performance of each functional component, so that the diaphragm has good adhesion performance, liquid retention performance, electrical performance and safety performance.
The coating 2 can be arranged on one side of the base film 1 facing the positive pole piece or one side of the base film 1 facing the negative pole piece according to actual needs; two layers can be arranged and are respectively arranged on two sides of the base film 1, so that the positive pole piece, the lithium ion battery diaphragm and the negative pole piece are integrated. In addition, the coating layer 2 should not be too thick to avoid affecting the electrical performance of the battery, and in view of this, the thickness of the coating layer 2 is 1-5 μm in this embodiment.
The base film 1 can be made of any one of polyethylene, polypropylene/polyethylene/polypropylene, polyimide, polyvinylidene fluoride and non-woven fabrics; it is understood that polypropylene/polyethylene/polypropylene refers to a composite film of polypropylene, polyethylene and polypropylene.
Since the base film 1 is too thick to affect ion transport and too thin to be easily penetrated, the thickness of the base film 1 is 5 to 20 μm in this embodiment. Further, base film 1 is preferably a film suitable for air permeability, and specifically, base film 1 has a porosity of 20 to 70%, so that the problem of ion channel clogging can be further improved.
The raw material of the first slurry and the second slurry may be any material commonly used in the art, for example, the pore-forming agent may be any pore-forming agent commonly used in the market. Preferably, in some embodiments, the ceramic powder comprises at least one of alumina, magnesia, zirconia, zinc oxide, titania, silica, aluminum hydroxide, calcium chloride, calcium carbonate nanoparticles; and/or the pore forming agent comprises at least one of ammonium bicarbonate, ammonium carbonate and ammonium chloride; and/or the first thickening agent and the second thickening agent are respectively and independently selected from at least one of carboxymethyl cellulose, hydroxymethyl cellulose, bentonite and attapulgite clay; and/or the first aqueous binder and the second aqueous binder are respectively and independently selected from at least one of acrylic polymer and polyurethane binder. That is, the ceramic powder may be any one of nanoparticles of alumina, magnesia, zirconia, zinc oxide, titania, silica, aluminum hydroxide, calcium chloride, calcium carbonate, or a mixture of any two or more thereof; the pore-forming agent can be any one of ammonium bicarbonate, ammonium carbonate and ammonium chloride, or a mixture of any two of the ammonium bicarbonate, the ammonium carbonate and the ammonium chloride, or a mixture of three of the ammonium bicarbonate, the ammonium carbonate and the ammonium chloride; the first thickener can be any one of carboxymethyl cellulose, hydroxymethyl cellulose, bentonite and attapulgite clay, or a mixture of any more than two of them; the second thickener can be any one of carboxymethyl cellulose, hydroxymethyl cellulose, bentonite and attapulgite clay, or a mixture of any more than two of them; the first aqueous binder may be an acrylic polymer and/or a polyurethane-based binder; the second aqueous binder may be an acrylic polymer and/or a polyurethane-based binder. When a material is a multi-component mixture, the components may be mixed in any ratio, and the present invention is not limited thereto.
Further, in some embodiments, the ceramic powder has a specific surface area of 4 to 15m 2 The grain diameter is 0.2-8 mu m, the ceramic powder in the parameter range has larger specific surface area, has better liquid retention performance, and is beneficial to further improving the liquid retention performance of the lithium ion battery diaphragm.
In addition, the first slurry may further include a first dispersant, and the weight part of the first dispersant added per 6 to 11 parts of PVDF powder is not higher than 1 part, that is, in this embodiment, the first slurry includes the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent, 2-7 parts of a pore-forming agent and a first dispersing agent with the weight part not higher than 1 part. By adding the first dispersing agent, the dispersing effect of the first slurry is improved, so that the components are better mixed, and when the first dispersing agent is mixed with the second slurry, the two slurries can be better combined, so that the respective advantageous characteristics of the PVDF powder and the ceramic powder are better kept, and the advantages of the PVDF powder and the ceramic powder are synergistically exerted. Specifically, the first dispersant includes at least one of polyvinyl alcohol, polyacrylic alcohol, hexadecylbenzene sulfonic acid, polyethylene glycol, modified polyacrylic acid, carboxylated modified styrene-butadiene latex, polyacrylonitrile-modified copolymer, polyacrylamide, polyvinyl acetamide, ammonium polyacrylate, polyether derivative, and polycarboxylate.
In addition, the second slurry may further include a second dispersant, and the weight part of the second dispersant added per 60 to 75 parts of the ceramic powder is not higher than 1 part, that is, in this embodiment, the second slurry includes the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder, 35-70 parts of water and not more than 1 part of a second dispersing agent by weight. The addition of the second dispersing agent is helpful for improving the dispersing effect of the second slurry, so that the components are better mixed, and when the second dispersing agent is mixed with the first slurry, the two slurries can be better combined, so that the respective advantageous characteristics of the PVDF powder and the ceramic powder can be better retained, and the advantages of the PVDF powder and the ceramic powder can be synergistically exerted. Specifically, the second dispersant includes at least one of polyvinyl alcohol, polyacrylic alcohol, hexadecylbenzene sulfonic acid, polyethylene glycol, modified polyacrylic acid, carboxylated modified styrene-butadiene latex, polyacrylonitrile-modified copolymer, polyacrylamide, polyvinyl acetamide, ammonium polyacrylate, polyether derivative, and polycarboxylate.
In some embodiments, the first slurry further comprises an adhesion promoter, and the parts by weight of adhesion promoter added per 6-11 parts PVDF powder is no higher than 1 part, i.e., in this embodiment, the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent, 2-7 parts of a pore-forming agent and an adhesion promoter with the weight part not higher than 1 part. Further, preferably, the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent, 2-7 parts of a pore-forming agent, 1 part by weight or less of a first dispersing agent and 1 part by weight or less of an adhesion promoter.
In some embodiments, the second slurry further comprises a wetting agent, and the weight part of the wetting agent added is not higher than 0.3 parts per 60-75 parts of the ceramic powder. That is, in this embodiment, the second slurry includes the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder, 35-70 parts of water and a wetting agent with the weight part not higher than 0.3 part. Further, preferably, the second slurry comprises the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder, 35-70 parts of water, not more than 0.3 part of a wetting agent and not more than 1 part of a second dispersing agent. Specifically, the wetting agent comprises at least one of fluoroalkyl methoxy ether alcohol, fluoroalkyl ethoxy ether alcohol, alkylphenol ethoxylate, fatty alcohol polyoxyethylene ether and fatty acid polyoxyethylene ether.
Based on the above examples, the present invention further provides a preferred coating 2 formulation. Specifically, in this embodiment, the raw materials of the coating 2 include a first slurry and a second slurry, wherein: the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent, 2-7 parts of a pore-forming agent, 1 part by weight or less of a first dispersing agent and 1 part by weight or less of an adhesion promoter; the second slurry comprises the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder, 35-70 parts of water, not more than 0.3 part of a wetting agent and not more than 1 part of a second dispersing agent.
Furthermore, the invention also provides a preparation method of the lithium ion battery separator, which is used for preparing the lithium ion battery separator. For convenience of description, the water in the first slurry is set as the first water, and the water in the second slurry is set as the second water. The preparation method of the lithium ion battery diaphragm comprises the following steps:
step S10, preparing first slurry: adding a first thickening agent into a part of first water, uniformly stirring, adding PVDF powder, and kneading to disperse the PVDF powder into the water to obtain a suspension; and adding a first water-based binder, a flatting agent and a pore-forming agent into the residual first water, uniformly mixing, adding turbid liquid, and uniformly dispersing to obtain a first slurry.
Specifically, when the first dispersant is further included in the components of the first slurry, the first dispersant and the first thickener are added together to the portion of the first water at the time of performing step S10; when an adhesion promoter is also included in the components of the first slurry, the adhesion promoter is added to the remaining first water prior to the first aqueous binder.
It can be understood that the above-mentioned components are added in the following parts: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent, 2-7 parts of a pore-forming agent, not more than 1 part of a first dispersing agent and not more than 1 part of an adhesion promoter.
Step S20, preparing second slurry: and adding ceramic powder into the second water, grinding after uniform dispersion, then adding a second thickening agent and uniformly stirring, and then adding a second aqueous binder and uniformly stirring to obtain a second slurry.
Specifically, when the second slurry further includes a second dispersant and a wetting agent in the components, the step S20 specifically includes:
and adding a second dispersant into second water, uniformly dispersing, adding ceramic powder, uniformly dispersing again, grinding, adding a second thickener, uniformly stirring, adding a second aqueous binder, uniformly stirring, adding a wetting agent, and uniformly stirring to obtain a second slurry.
It can be understood that the above-mentioned components are added in the following parts: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder, 35-70 parts of water, not more than 0.3 part of a wetting agent and not more than 1 part of a second dispersing agent.
And step S30, mixing the first slurry and the second slurry, and uniformly stirring to obtain the slurry of the coating 2.
Wherein the weight ratio of the first slurry to the second slurry is 1: (2-6) mixing.
And S40, coating the slurry of the coating 2 on at least one side of the base film 1 subjected to corona treatment to form the coating 2 distributed in a dot matrix manner, and curing to obtain the lithium ion battery diaphragm.
In practical operation, the coating can be performed by using a flexo printing, gravure printing, screen printing or letterpress printing process.
The preparation method is simple to operate and low in process difficulty, the PVDF and the ceramic can be well mixed uniformly, the respective advantages of the PVDF and the ceramic can be effectively exerted, the prepared lithium ion battery diaphragm meets the cohesiveness of the diaphragm, the safety performance of the battery is enhanced, and the problem that the coating 2 is compact and blocks an ion channel can be solved.
The technical solutions of the present invention are further described in detail with reference to the following specific examples, which should be understood as merely illustrative and not limitative.
The lithium ion battery separator manufactured in the following example has a structure in which a first coating layer 2, a base film 1, and a second coating layer 2 are sequentially stacked from bottom to top.
Example 1
TABLE 1
The preparation method comprises the following steps:
adding a first dispersing agent and a first thickening agent into a part of water for the first slurry, uniformly stirring, slowly adding PVDF powder, transferring into a kneader, setting the rotation speed of the kneader to be 1200rpm, and treating for 60min through a kneading process to completely melt PVDF into water to prepare a PVDF suspension; and adding the adhesion promoter, the first water-based binder and the flatting agent into the rest water, and uniformly mixing for 30min at the rotating speed of 1000rpm. And then adding a pore-forming agent, stirring to uniformly mix for 10min at the rotation speed of 1500rpm, finally adding the prepared PVDF suspension, mixing and stirring for 60min at the rotation speed of 1200rpm, and preparing a first slurry.
Adding the second dispersant into the second slurry water, uniformly dispersing, and adding ceramic powder (with a specific surface area of 4-15 m) 2 G, the grain diameter is 0.2-8 mu m), the stirring time is 70min, the rotating speed is 1800rpm, and the grinding is carried out after the uniform dispersion; then, adding a second thickening agent into the mixture for stirring for 40min at the rotating speed of 100rpm; adding a second aqueous binder for stirring, wherein the stirring time is 30min and the rotating speed is 120rpm; and finally, adding a wetting agent into the mixture for stirring for 40min at the rotating speed of 50rpm to obtain second slurry.
And mixing and stirring the obtained first slurry and second slurry for 60min at the rotating speed of 1500rpm to obtain coating slurry.
Coating the coating slurry on one side of a base film with the thickness of 5-20 mu m and the porosity of 20-70% at the coating speed of 60m/min to obtain a coating with the thickness of 1-5 mu m; then drying the film in a drying oven at the temperature of 30-60 ℃, wherein the pore-forming agent is decomposed and volatilized to form apertures with uniform size and distribution, and a base film with a coating on one side is obtained; and then coating the coating slurry on the other side of the base film, and drying to obtain the lithium ion battery diaphragm.
Example 2
TABLE 2
The preparation method comprises the following steps:
adding a first dispersing agent and a first thickening agent into a part of water for the first slurry, uniformly stirring, slowly adding PVDF powder, transferring into a kneader, setting the rotation speed of the kneader to be 1300rpm, and treating for 50min through a kneading process to completely dissolve PVDF into the water to prepare a PVDF suspension; and adding the adhesion promoter, the first water-based binder and the flatting agent into the rest water, and uniformly mixing for 20min at the rotating speed of 1000rpm. And then adding a pore-forming agent, stirring to uniformly mix, wherein the stirring time is 40min and the rotating speed is 1500rpm, finally adding the prepared PVDF suspension, mixing and stirring, wherein the stirring time is 50min and the rotating speed is 2000rpm, and preparing a first slurry.
Adding the second dispersant into the second slurry water, uniformly dispersing, and adding ceramic powder (with a specific surface area of 4-15 m) 2 G, the grain diameter is 0.2-8 mu m), the stirring time is 50min, the rotating speed is 2000rpm, and the grinding is carried out after the uniform dispersion; then, adding a second thickening agent into the mixture for stirring for 30min at the rotating speed of 200rpm; adding a second aqueous binder for stirring, wherein the stirring time is 20min, and the rotating speed is 200rpm; and finally, adding a wetting agent into the mixture for stirring for 30min at the rotating speed of 100rpm to obtain second slurry.
And mixing and stirring the obtained first slurry and the second slurry for 80min at the rotating speed of 1200rpm to obtain the coating slurry.
Coating the coating slurry on one side of a base film with the thickness of 5-20 μm and the porosity of 20-70% at a coating speed of 60m/min to obtain a coating with the thickness of 1-5 μm; then drying the film in a drying oven at the temperature of 30-60 ℃, wherein the pore-forming agent is decomposed and volatilized to form apertures with uniform size and distribution, and a base film with a coating on one side is obtained; and then coating the coating slurry on the other side of the base film, and drying to obtain the lithium ion battery diaphragm.
The following examples all used the same preparation method as in example 1.
Example 3
TABLE 3
Example 4
TABLE 4
Example 5
TABLE 5
Example 6
TABLE 6
Comparative example 1
The procedure was as in example 1 except that no pore-forming agent was added.
Comparative example 2
The only difference from example 1 is that the only raw material of the coating layer is the first paste.
Comparative example 3
The difference from example 1 is in the preparation method of the coating slurry, and the preparation method of this comparative example comprises the following steps:
all the components in table 1 were mixed and ground after adding ceramic powder to make the components uniformly dispersed to prepare a coating slurry.
The lithium ion battery separators of the above examples and comparative examples were subjected to a cell performance test (test cell model: 18650).
The positive electrode plate, the isolation film and the lithium ion battery diaphragm are sequentially laminated to form the lithium ion battery, and the preparation method can refer to a conventional lithium ion battery assembly method in the market, and details are not described herein. The anode plate is made of one or more of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium manganate and lithium iron phosphate, and the cathode plate is made of graphite. And then carrying out performance test on the lithium ion battery, wherein the test items comprise a voltage drop test, a cycle performance test and an electrode assembly full charge expansion rate test, and the test method comprises the following steps:
1. voltage drop test:
10-20 battery cells are taken and charged to 4.2V at constant current and constant voltage of 1C, the cut-off current is 0.02C, the initial voltage of the battery cells is tested and recorded after the battery cells are placed for 4h, the voltage of the battery cells is tested every day for 1 month, and finally the total K value (mV/h) of one month is calculated.
2. And (3) testing cycle performance:
the battery cell is charged to 4.2V at a constant current and a constant voltage of 1C, the current is cut off to 0.02C, and then discharged to 3.0V at a constant current of 1C, and the capacity retention rate is recorded after the cycle is repeated for 500 weeks.
3. Full charge expansion rate test of the electrode assembly:
the method comprises the steps of discharging the battery cell to 3.0V at a constant current of 1C, measuring the diameter of the battery cell, charging the battery cell to 4.2V at a constant current and a constant voltage of 1C, measuring the full-electricity diameter of the same position of the battery cell, and finally calculating the full-electricity size expansion rate of the battery cell.
The results are reported in table 7 below.
TABLE 7 Electrical core Performance test
And (4) analyzing results:
firstly, as can be seen from the above detection data, all the embodiments can prepare the battery cell with higher flatness, and the battery cell integrally shows better liquid retention capability and safety performance, and has excellent cycle performance, which indicates that the lithium ion battery diaphragm of the invention can have better adhesive property, liquid retention capability and safety performance, and avoids the problem of ion channel blockage.
Second, cross-direction comparison with comparative example. Wherein, the comparison of example 1 and comparative example 1 shows that the pore size distribution of the diaphragm is not uniform without adding pore-forming agent, which results in the deterioration of self-discharge rate and cycle performance of the battery cell, and the comparison of comparative example 2 shows that the pressure drop of the battery cell is slightly deteriorated without adding ceramic, but the stability of the cycle is greatly influenced, and in addition, the thermal stability and safety performance of the battery cell are greatly reduced, and the comparison of comparative example 3 shows that if the ceramic powder is directly added into the PVDF slurry, the dispersion of the coating slurry is not uniform, the pressure drop of the battery cell and the stability of the cycle performance are influenced, and the consistency of the final battery cell is poor.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (9)
1. The lithium ion battery separator is characterized by comprising a base film, wherein at least one side of the base film is provided with a coating, and the raw material of the coating comprises a first slurry and a second slurry, wherein:
the first slurry comprises the following components in parts by weight: 6-11 parts of PVDF powder, 2-6 parts of a first thickening agent, 3-6 parts of a first aqueous binder, 35-70 parts of water, 1-4 parts of a leveling agent and 2-7 parts of a pore-forming agent;
the second slurry comprises the following components in parts by weight: 60-75 parts of ceramic powder, 15-25 parts of a second thickening agent, 5-10 parts of a second aqueous binder and 35-70 parts of water;
wherein the thickness of the coating layer is 1-5 μm, the thickness of the base film is 13-20 μm, and the porosity of the base film is 20-70%.
2. The lithium ion battery separator of claim 1, wherein the weight ratio of the PVDF powder to the ceramic powder in the coating is 1: (2-6).
3. The lithium ion battery separator of claim 1, wherein the ceramic powder comprises at least one of alumina, magnesia, zirconia, zinc oxide, titania, silica, aluminum hydroxide, calcium chloride, calcium carbonate nanoparticles; and/or the presence of a gas in the gas,
the pore-forming agent comprises at least one of ammonium bicarbonate, ammonium carbonate and ammonium chloride; and/or the presence of a gas in the gas,
the first thickening agent and the second thickening agent are respectively and independently selected from at least one of carboxymethyl cellulose, hydroxymethyl cellulose, bentonite and attapulgite clay; and/or the presence of a gas in the atmosphere,
the first aqueous binder and the second aqueous binder are respectively and independently selected from at least one of acrylic polymer and polyurethane binder.
4. The lithium ion battery separator according to claim 1, wherein the ceramic powder has a specific surface area of 4 to 15m 2 (iii) a particle size of 0.2-8 μm/g.
5. The lithium ion battery separator according to claim 1, wherein the first slurry further comprises a first dispersant, and the weight part of the first dispersant added per 6-11 parts of PVDF powder is not higher than 1 part; and/or the presence of a gas in the atmosphere,
the first slurry also comprises an adhesion promoter, and the weight part of the adhesion promoter added is not higher than 1 part per 6-11 parts of PVDF powder; and/or the presence of a gas in the gas,
the second slurry also comprises a second dispersing agent, and the weight part of the second dispersing agent added is not more than 1 part per 60-75 parts of the ceramic powder; and/or the presence of a gas in the atmosphere,
the second slurry also comprises a wetting agent, and the weight part of the wetting agent added is not higher than 0.3 part per 60-75 parts of the ceramic powder.
6. The lithium ion battery separator of claim 5, wherein the first dispersant comprises at least one of polyvinyl alcohol, polyacrylic alcohol, hexadecylbenzene sulfonic acid, polyethylene glycol, modified polyacrylic acid, carboxylated modified styrene-butadiene latex, polyacrylonitrile modified copolymer, polyacrylamide, polyvinyl acetamide, ammonium polyacrylate, polyether derivatives, and polycarboxylate; and/or the presence of a gas in the atmosphere,
the second dispersant comprises at least one of polyvinyl alcohol, polyacrylic alcohol, hexadecyl benzene sulfonic acid, polyethylene glycol, modified polyacrylic acid, carboxylated modified styrene-butadiene latex, polyacrylonitrile modified copolymer, polyacrylamide, polyvinyl acetamide, ammonium polyacrylate, polyether derivative and polycarboxylate.
7. The lithium ion battery separator according to claim 6, wherein the wetting agent comprises at least one of a fluoroalkyl methoxy ether alcohol, a fluoroalkyl ethoxy ether alcohol, an alkylphenol ethoxylate, a fatty alcohol ethoxylate, and a fatty acid ethoxylate.
8. The lithium ion battery separator according to claim 1, wherein the material of the base film comprises polyethylene, polypropylene/polyethylene/polypropylene, polyimide, polyvinylidene fluoride, or non-woven fabric.
9. A lithium ion battery is characterized by comprising a positive pole piece, a lithium ion battery diaphragm and a negative pole piece which are sequentially stacked, wherein the lithium ion battery diaphragm is the lithium ion battery diaphragm of any one of claims 1 to 8.
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| CN102916149B (en) * | 2012-09-26 | 2015-10-28 | 东莞市创明电池技术有限公司 | A kind of lithium battery micro-pore septum and preparation technology thereof |
| CN104064705B (en) * | 2014-06-09 | 2017-01-04 | 东莞市魔方新能源科技有限公司 | A kind of lithium rechargeable battery composite diaphragm, its manufacture method and the electrochemical appliance containing this barrier film |
| CN104993089B (en) * | 2015-07-29 | 2018-03-16 | 沧州明珠隔膜科技有限公司 | A kind of lithium ion battery separator of aramid fiber coating and preparation method thereof |
| CN105591055A (en) * | 2015-12-17 | 2016-05-18 | 中南大学 | High-multiplying power lithium ion battery and preparation method thereof |
| CN105845872A (en) * | 2016-05-04 | 2016-08-10 | 合肥国轩高科动力能源有限公司 | Coating slurry for bonding lithium battery separator and pole piece and preparation method of coating slurry |
| CN108258299B (en) * | 2018-01-10 | 2020-04-17 | 深圳市正翔电池能源有限公司 | Lithium ion power battery |
| CN109346650A (en) * | 2018-10-25 | 2019-02-15 | 苏州捷力新能源材料有限公司 | A kind of lithium ion battery separator and preparation method of the mixed painting of ceramics PVDF |
| CN109860472A (en) * | 2018-11-28 | 2019-06-07 | 湖南中锂新材料有限公司 | Porous composite diaphragm, preparation method and the lithium ion battery comprising it |
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| CN111987273A (en) * | 2019-05-23 | 2020-11-24 | 河北金力新能源科技股份有限公司 | PVDF&Al2O3Mixed coating slurry, preparation method thereof, lithium ion battery diaphragm and lithium ion battery |
| CN110429225A (en) * | 2019-06-26 | 2019-11-08 | 高芳 | A kind of preparation method of lithium ion battery ceramic coating membrane |
| CN111584798B (en) * | 2019-09-11 | 2022-11-01 | 河北金力新能源科技股份有限公司 | Lithium battery diaphragm slurry, diaphragm prepared from lithium battery diaphragm slurry and application of lithium battery diaphragm slurry |
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