CN113839146B - Lithium ion battery diaphragm coated with negative electrode active material, and preparation method and application thereof - Google Patents
Lithium ion battery diaphragm coated with negative electrode active material, and preparation method and application thereof Download PDFInfo
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- CN113839146B CN113839146B CN202111094077.6A CN202111094077A CN113839146B CN 113839146 B CN113839146 B CN 113839146B CN 202111094077 A CN202111094077 A CN 202111094077A CN 113839146 B CN113839146 B CN 113839146B
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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
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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
- 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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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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
- H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
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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 relates to a lithium ion battery diaphragm coated with a negative electrode active material, and belongs to the technical field of diaphragms. The lithium ion battery diaphragm coated with the negative electrode active material comprises a first layer film and a second layer film; the first layer film is a base film, the second layer film comprises a polymer base material, a negative electrode active substance and a conductive agent, and the weight ratio of the polymer base material to the negative electrode active substance to the conductive agent is 0.5-99.5:0.5-99:0.5-10; the negative electrode active material is at least one of a mixture of ceramic particles and graphite, lithium titanate and a silicon-carbon material. The second layer film brings extra battery capacity, and improves the energy density of the battery; the second layer film can play a role of a traditional diaphragm ceramic layer, and can provide the effects of thermal stability and mechanical strength similar to those of traditional ceramic coatings such as alumina; the second film also increases the interfacial stability and compatibility between the separator and the negative electrode.
Description
Technical Field
The invention relates to a lithium ion battery diaphragm coated with a negative electrode active material, and belongs to the technical field of diaphragms.
Background
With the continuous development of new energy electric automobiles and portable electronic devices, lithium ion batteries have become the first choice of commercial batteries, and in the structure of lithium batteries, a separator is one of the key inner layer components. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The separator has the main function of separating the positive electrode from the negative electrode of the battery, preventing the two electrodes from contacting and shorting, and also has the function of allowing ions to pass through. The separator material is non-conductive, and its physicochemical properties have a great influence on the performance of the battery. Since the electrolyte is an organic solvent system, a separator material resistant to an organic solvent is required for a lithium ion battery, and the separator is required to have the following properties:
in a battery system, the chemical stability is good, and the used materials can resist organic solvents; the mechanical strength is high, and the service life is long; the ionic conductivity of the organic electrolyte is lower than that of the aqueous system, and in order to reduce the resistance, the electrode area must be as large as possible, so the separator must be thin; when the battery system is abnormal, the temperature is increased, and in order to prevent the danger, the thermoplastic diaphragm is melted at the beginning of the rapid heat generation temperature (120-140 ℃), and the micropores are closed and become an insulator; from the perspective of lithium batteries, it is desirable to be sufficiently impregnated with an organic electrolyte and to maintain a high degree of impregnation during repeated charge and discharge.
The lithium ion battery generally employs a polyolefin porous film having high strength and being formed into a thin film, and a separator commonly used is a polypropylene (PP) and Polyethylene (PE) microporous separator, a copolymer of propylene and ethylene, a polyethylene homopolymer, or the like. The advantages of applying ceramic powder for diaphragm coating: can prevent lithium dendrite penetration, resist high temperature shrinkage, and ensure lithium safety; isolating the positive electrode and the negative electrode to realize electronic insulation between the positive electrode and the negative electrode; providing an ion channel between the anode and the cathode to realize the charge and discharge functions of the lithium ion battery; absorbing and maintaining electrolyte to ensure the cycle life of the lithium battery; and the sufficient porosity is ensured, and the multiplying power characteristic of the lithium ion battery is ensured. And the safety index of the lithium battery is effectively improved.
At present, the wet-process diaphragm coating material takes an alumina coating as a main material, occupies the market share of the main flow, and simultaneously contains rich coating products such as PVDF coating, PVDF/alumina mixed coating, alumina+PVDF overlapped composite coating, boehmite, aramid fiber, nano composite material and the like. Because the aluminum oxide is used as an inorganic substance, the aluminum oxide has high thermal stability and chemical inertness, and is a good choice for the ceramic coating of the battery diaphragm. One of the interesting trends is that due to the low hardness of boehmite, the abrasion to the machinery during cutting and coating is small, the preparation is simpler, and the cost can be effectively reduced. Compared with alumina, the boehmite coating process has lower energy consumption and is more environment-friendly. Boehmite thus starts to occupy the market. However, it has also been found that boehmite is used in lithium battery separators, which can cause excessive sodium impurities to leach into the electrolyte, thereby causing thermal runaway, inefficiency, and shortened life of the lithium battery. In addition, inert coatings based on alumina and boehmite, while improving separator stability, reduce the energy density of the battery.
Disclosure of Invention
The invention aims to provide a lithium ion battery diaphragm coated with a negative electrode active material.
In order to solve the first technical problem, the lithium ion battery separator coated with the negative electrode active material comprises a first layer film and a second layer film; the first layer film is a base film, the second layer film comprises a polymer base material, a negative electrode active substance and a conductive agent, and the weight ratio of the polymer base material to the negative electrode active substance to the conductive agent is 0.5-99.5:0.5-99:0.5-10; preferably, the weight ratio of the polymer base material, the negative electrode active material and the conductive agent is 0.5-99.5:0.5-95:2.5-5;
the negative electrode active material is at least one of a mixture of ceramic particles and graphite, lithium titanate and a silicon-carbon material.
In one embodiment, the base film is a polypropylene, polyethylene, a bilayer polypropylene/polyethylene composite film, a trilayer polypropylene/polyethylene/polypropylene composite film, a nitrocellulose film, a cellulose acetate film, a polyamide film, a polyethylene terephthalate, a polyester film, a thermoplastic polyimide, a thermosetting polyimide, a polyamide-imide, a polyether imide, a ground-to-mole fiber film, a polyamide film, a metal film, an alloy film, a ceramic film, a molecular sieve composite film, a zeolite film, or a glass film.
In a specific embodiment, the polymer substrate is at least one of polyvinylidene fluoride polymer, polybutyl acrylate, polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinylidene fluoride, polydimethoxyethoxyethanol-phosphazene, polyvinyl chloride, polydimethylsiloxane, polyvinylidene fluoride-hexafluoropropylene, polyperfluorosulfonic acid, sulfonated polytetrafluoroethylene, sulfonated perfluoroalkoxy derivatives of polytetrafluoroethylene, sulfonated poly-alum, sulfonated polyether ketone, sulfonated polyether ether ketone, sulfonated polystyrene, sulfonated polyimide, sulfonated styrene-butadiene copolymer, sulfonated poly-chloro-trifluoroethylene, sulfonated perfluoroethylene-propylene copolymer, sulfonated ethylene-chlorotrifluoroethylene copolymer, sulfonated polyvinylidene fluoride, sulfonated copolymer of polyvinylidene fluoride and hexafluoropropylene and tetrafluoroethylene, sulfonated copolymer of ethylene and tetrafluoroethylene, polybenzimidazole, and chemical derivatives and copolymers thereof.
In a specific embodiment, the conductive agent is one or more of acetylene black, 350G, carbon fiber, carbon nanotube, ketjen black, graphite conductive agent, graphene and Super P; the KetjenbackEC 300J, ketjenblackEC JD, carbon ECP600JD are preferable; the graphite conductive agent is preferably KS-6, KS-15, SFG-6, SFG-15.
In one embodiment, the first film has a thickness of 5 to 40 μm and the second film has a thickness of 1 to 20 μm.
The second technical problem to be solved by the invention is to provide a preparation method of the lithium ion battery diaphragm coated with the negative electrode active material.
In order to solve the second technical problem of the invention, the preparation method of the lithium ion battery diaphragm coated with the anode active material comprises the following steps:
a. adding the polymer substrate into a solvent, and stirring to form stable slurry A;
b. adding a conductive agent into the slurry, and uniformly stirring to form slurry B;
c. adding the negative electrode active material into the slurry B, and uniformly dispersing to obtain a slurry C;
d. uniformly coating the slurry C on the base film, and removing the solvent;
preferably, the mass of the solvent accounts for 60-80% of the total mass of the slurry C;
the steps a to c are preferably carried out in a closed vessel.
In a specific embodiment, the step c is that the uniform dispersion is carried out by stirring uniformly and ultrasonic dispersion, and stirring is continued after ultrasonic treatment; the stirring is preferably 500-1000 r/min, and stirring is carried out for 12-24 h; the ultrasonic wave is preferably 30-40 kHz and lasts for 25-35 min;
and d, uniformly coating the slurry C on the base film by spraying, casting, screen printing, dip-coating or electrophoresis.
In one embodiment, the solvent is selected from at least one of N-methylpyrrolidone, acetone, 1, 3-dioxolane, 1, 2-dimethoxyethane, tetraethyleneglycol dimethyl ether, poly (ethyleneglycol) dimethyl ether, diethyleneglycol dibutyl ether, 2-ethoxyethyl ether, ethylene carbonate, dimethyl carbonate, methylethyl carbonate, methyl carbonate, benzene, toluene, xylene, methyl acetate, fluoroethylene carbonate, vinylene carbonate, allyl ethyl carbonate, hydrofluoroether, ionic liquid solvents, cyclohexane, cyclohexanone, toluene cyclohexanone, chlorobenzene, dichlorobenzene, dichloromethane, isopropanol, diethyl ether, propylene oxide, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl butanone, methyl isopropyl Ding Tonger ethyl ester, ethyl propionate, methyl propionate, propylene carbonate, gamma-butyrolactone, acetonitrile, ethyl acetate, propyl formate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol.
The third technical problem to be solved by the invention is to provide the application of the lithium ion battery separator coated with the negative electrode active material in the preparation of a lithium ion battery, wherein the positive electrode of the battery faces to the second layer film, and the negative electrode of the battery faces to the first layer film.
In one embodiment, the negative electrode active material is contained in a material of a positive electrode of the battery.
The negative electrode active material contained in the material of the positive electrode of the battery means that the negative electrode active material has better effect as the material of the positive electrode, for example, the positive electrode is lithium titanate, and then the negative electrode active material is lithium titanate. On the premise of not reducing the safety, active substances in the separator can contribute energy to the battery, so that the battery separator with more excellent performance is obtained.
The beneficial effects are that:
the second layer film brings extra battery capacity, and improves the energy density of the battery;
the second layer film can play a role of a traditional diaphragm ceramic layer, and can provide the effects of thermal stability and mechanical strength similar to those of traditional ceramic coatings such as alumina;
in addition, the second film also increases the interfacial stability and compatibility between the separator and the negative electrode.
Drawings
FIG. 1 is a contact angle test;
FIG. 2 is a tensile test of a separator prepared in the examples;
fig. 3 is a cyclic test experiment of comparative examples 1 and 2, example 2 and PP as separator directly.
Fig. 4 is a cyclic test experiment of comparative examples 1 and 2, example 1 and PP as separator directly.
Detailed Description
In order to solve the first technical problem, the lithium ion battery separator coated with the negative electrode active material comprises a first layer film and a second layer film; the first layer film is a base film, the second layer film comprises a polymer base material, a negative electrode active substance and a conductive agent, and the weight ratio of the polymer base material to the negative electrode active substance to the conductive agent is 0.5-99.5:0.5-99:0.5-10; preferably, the weight ratio of the polymer base material, the negative electrode active material and the conductive agent is 0.5-99.5:0.5-95:2.5-5;
the negative electrode active material is at least one of a mixture of ceramic particles and graphite, lithium titanate and a silicon-carbon material.
In one embodiment, the base film is a polypropylene, polyethylene, a bilayer polypropylene/polyethylene composite film, a trilayer polypropylene/polyethylene/polypropylene composite film, a nitrocellulose film, a cellulose acetate film, a polyamide film, a polyethylene terephthalate, a polyester film, a thermoplastic polyimide, a thermosetting polyimide, a polyamide-imide, a polyether imide, a ground-to-mole fiber film, a polyamide film, a metal film, an alloy film, a ceramic film, a molecular sieve composite film, a zeolite film, or a glass film.
In a specific embodiment, the polymer substrate is at least one of polyvinylidene fluoride polymer, polybutyl acrylate, polyacrylonitrile, polyethylene oxide, polypropylene oxide, polymethyl methacrylate, polyvinylidene fluoride, polydimethoxyethoxyethanol-phosphazene, polyvinyl chloride, polydimethylsiloxane, polyvinylidene fluoride-hexafluoropropylene, polyperfluorosulfonic acid, sulfonated polytetrafluoroethylene, sulfonated perfluoroalkoxy derivatives of polytetrafluoroethylene, sulfonated poly-alum, sulfonated polyether ketone, sulfonated polyether ether ketone, sulfonated polystyrene, sulfonated polyimide, sulfonated styrene-butadiene copolymer, sulfonated poly-chloro-trifluoroethylene, sulfonated perfluoroethylene-propylene copolymer, sulfonated ethylene-chlorotrifluoroethylene copolymer, sulfonated polyvinylidene fluoride, sulfonated copolymer of polyvinylidene fluoride and hexafluoropropylene and tetrafluoroethylene, sulfonated copolymer of ethylene and tetrafluoroethylene, polybenzimidazole, and chemical derivatives and copolymers thereof.
In a specific embodiment, the conductive agent is one or more of acetylene black, 350G, carbon fiber, carbon nanotube, ketjen black, graphite conductive agent, graphene and Super P; the KetjenbackEC 300J, ketjenblackEC JD, carbon ECP600JD are preferable; the graphite conductive agent is preferably KS-6, KS-15, SFG-6, SFG-15.
In one embodiment, the first film has a thickness of 5 to 40 μm and the second film has a thickness of 1 to 20 μm.
The second technical problem to be solved by the invention is to provide a preparation method of the lithium ion battery diaphragm coated with the negative electrode active material.
In order to solve the second technical problem of the invention, the preparation method of the lithium ion battery diaphragm coated with the anode active material comprises the following steps:
a. adding the polymer substrate into a solvent, and stirring to form stable slurry A;
b. adding a conductive agent into the slurry, and uniformly stirring to form slurry B;
c. adding the negative electrode active material into the slurry B, and uniformly dispersing to obtain a slurry C;
d. uniformly coating the slurry C on the base film, and removing the solvent;
preferably, the mass of the solvent accounts for 60-80% of the total mass of the slurry C;
the steps a to c are preferably carried out in a closed vessel.
In a specific embodiment, the step c is that the uniform dispersion is carried out by stirring uniformly and ultrasonic dispersion, and stirring is continued after ultrasonic treatment; the stirring is preferably 500-1000 r/min, and stirring is carried out for 12-24 h; the ultrasonic wave is preferably 30-40 kHz and lasts for 25-35 min;
and d, uniformly coating the slurry C on the base film by spraying, casting, screen printing, dip-coating or electrophoresis.
In one embodiment, the solvent is selected from at least one of N-methylpyrrolidone, acetone, 1, 3-dioxolane, 1, 2-dimethoxyethane, tetraethyleneglycol dimethyl ether, poly (ethyleneglycol) dimethyl ether, diethyleneglycol dibutyl ether, 2-ethoxyethyl ether, ethylene carbonate, dimethyl carbonate, methylethyl carbonate, methyl carbonate, benzene, toluene, xylene, methyl acetate, fluoroethylene carbonate, vinylene carbonate, allyl ethyl carbonate, hydrofluoroether, ionic liquid solvents, cyclohexane, cyclohexanone, toluene cyclohexanone, chlorobenzene, dichlorobenzene, dichloromethane, isopropanol, diethyl ether, propylene oxide, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl butanone, methyl isopropyl Ding Tonger ethyl ester, ethyl propionate, methyl propionate, propylene carbonate, gamma-butyrolactone, acetonitrile, ethyl acetate, propyl formate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol.
The third technical problem to be solved by the invention is to provide the application of the lithium ion battery separator coated with the negative electrode active material in the preparation of a lithium ion battery, wherein the positive electrode of the battery faces to the second layer film, and the negative electrode of the battery faces to the first layer film.
In one embodiment, the negative electrode active material is contained in a material of a positive electrode of the battery.
The negative electrode active material contained in the material of the positive electrode of the battery means that the negative electrode active material has better effect as the material of the positive electrode, for example, the positive electrode is lithium titanate, and then the negative electrode active material is lithium titanate. On the premise of not reducing the safety, active substances in the separator can contribute energy to the battery, so that the battery separator with more excellent performance is obtained.
The following describes the invention in more detail with reference to examples, which are not intended to limit the invention thereto.
Example 1
The first separator is a PP-based film.
The preparation method of the second layer diaphragm solution comprises the following steps:
(1) 0.14g of polymer base material polyvinylidene fluoride (PVDF), ketjenblack EC300J0.06g and anode active material 1.8g of mixture of silica powder and graphite, wherein the mass ratio of silica powder to graphite is 1:89, and solvent N-methyl pyrrolidone (NMP) accounting for 80% of the total mass of the solution are weighed.
(2) Adding the polymer substrate PVDF into a solvent, and stirring to form a stable transparent colloid;
(3) Adding 0.06g of Keqin black as a conductive agent into the colloid to form a second colloid.
(4) And adding graphite containing 1% of silicon powder as a negative electrode active material into the second colloid, uniformly stirring, and performing ultrasonic dispersion for 30min. Steps (2) to (4) are carried out in a closed vessel.
(5) And continuously stirring the ultrasonic glue solution for 18 hours, and uniformly mixing to form the slurry for the second layer of diaphragm.
(6) And casting the second part of colloid on the PP commercial base film by the slurry prepared by the method, so as to ensure that the thickness of the second layer of film is between 1 and 20 mu m.
(7) And (3) placing the electrode slurry with uniform thickness, which is coated in the step (6), in a vacuum oven at 60 ℃ for drying for 18 hours, wherein the vacuum degree is the lowest.
(8) And (3) packaging and storing the membrane dried in the step (7), taking two smooth and clean plastic films, and clamping the membrane in the plastic films.
The graphite/metal lithium button half cell is used for testing, and the graphite pole piece (positive electrode) of the cell comprises 90% of graphite, 7% of polymer and 3% of conductive agent. The electrolyte is prepared according to the formula of 1.0M LiPF6 in EC:DMC =3: 7Vol% of secondary electrolyte LB-063. The lithium titanate electrode faces the second layer film and the lithium metal sheet faces the first layer film when the battery is assembled. After the battery is assembled, performing battery cycle test on a Xinwei battery test system at 25 ℃, calculating the weight of active substances contained in a single pole piece through the total weight of a lithium titanate electrode, and then passing through i 1C The magnitude of the current of 0.1C and 0.5C circulating at the time of battery test is calculated, and for the cycle test, the charge and discharge test of 0.1C for 2-3 cycles is required, which is mainly to activate the battery so that the battery capacity can be optimized. The battery was then subjected to a charge-discharge test at a rate of 0.5C, and its cycle performance was observed. The test results of example 1 and comparative example are shown in Table 1 and FIG. 4.
TABLE 1 results of cycle performance test
| Product(s) | Cycle 50 efficiency％ | 50 times of capacity mAh/g are circulated | Cycle 100 cycles efficiency% | 100 circles of capacity mAh/g are circulated |
| Example 1 | 101 | 345 | 99.8 | 347 |
| Comparative example 1 | 101 | 293.3 | 100.5 | 294.5 |
| Comparative example 2 | 101 | 289.3 | 100.5 | 291.3 |
| PP | 99.8 | 283 | 99.8 | 285 |
Example 2
This example differs from example 1 in that the negative electrode active material was lithium titanate, and the other steps were the same as in example 1.
The lithium titanate/metal lithium button half battery is adopted for testing, the lithium titanate pole piece (positive electrode) of the battery comprises 90 percent of lithium titanate, 5 percent of conductive agent, 5 percent of polymer and electrolyteFormulation 1.0M LiPF6 in EC:DMC =3: 7Vol% of secondary electrolyte LB-063. The lithium titanate electrode faces the second layer film and the lithium metal sheet faces the first layer film when the battery is assembled. After the battery is assembled, performing battery cycle test on a Xinwei battery test system at 25 ℃, calculating the weight of active substances contained in a single pole piece through the total weight of a lithium titanate electrode, and then passing through i 1C The magnitude of the current of 0.1C and 0.5C circulating at the time of battery test is calculated, and for the cycle test, the charge and discharge test of 0.1C for 2-3 cycles is required, which is mainly to activate the battery so that the battery capacity can be optimized. The battery was then subjected to a charge-discharge test at a rate of 0.5C, and its cycle performance was observed. The test results of example 1 and comparative example are shown in Table 2 and FIG. 3.
TABLE 2 results of cycle performance test
| Product(s) | Cycle 50 cycles efficiency% | 50 times of capacity mAh/g are circulated | Cycle 100 cycles efficiency% | 100 circles of capacity mAh/g are circulated |
| Example 2 | 99.9 | 165.4 | 99.7 | 162.4 |
| Comparative example 1 | 100.3 | 144.7 | 99.6 | 141.7 |
| Comparative example 2 | 99 | 143.8 | 99.2 | 140.5 |
| PP | 99.9 | 141.4 | 99.5 | 140 |
Comparative example 1
The difference between this experiment and example 1 is that the second film PVDF polymer weight is 97% of the film forming material weight, the superconductive carbon black weight is 3% of the film forming material weight, and no negative electrode active material is present.
Comparative example 2
The experiment differs from example 1 in that the second film PVDF polymer comprises 7% by weight of the film forming material, the superconductive carbon black comprises 3% by weight of the film forming material, and the alumina (Al 2 O 3 ) The specific gravity was 90%.
As can be seen from the contact angle test of FIG. 1, examples 1-2 coated Si/C film, lithium titanate (Li 4 Ti 5 O 12 ) The hydrophilicity of the coating film is stronger.
The tensile strength and tensile fracture rate of the coated membrane of fig. 2 are both significantly improved, and the mechanical properties are increased.
As can be seen from fig. 3 and 4, the separator has a significant improvement in battery capacity, and the PP film and the film coated with aluminum oxide and 97% pvdf have a small difference in battery capacity, but the stability and mechanical properties of the separator are enhanced, but the lithium titanate and Si/C coating of the present invention has a significant improvement in capacity. The increased number of cycles can be seen to give a stronger coating layer stability.
Claims (11)
1. A negative active material coated lithium ion battery separator characterized in that the separator comprises a first layer film and a second layer film; the first layer film is a base film, the second layer film comprises a polymer base material, a negative electrode active material and a conductive agent, the weight ratio of the polymer base material to the negative electrode active material to the conductive agent is 7:90:3, the thickness of the first layer film is 5-40 mu m, and the thickness of the second layer film is 1-20 mu m;
the negative electrode active material is a mixture of silicon powder and graphite, wherein the mass ratio of the silicon powder to the graphite is 1:89; the polymer base material is polyvinylidene fluoride polymer; the conductive agent is ketjenbackec 300J, ketjen black.
2. The anode active material coated lithium ion battery separator according to claim 1, wherein the base film is polypropylene, polyethylene, a double-layer polypropylene/polyethylene composite film, a three-layer polypropylene/polyethylene/polypropylene composite film, a nitrocellulose film, a cellulose acetate film, a polyamide film, polyethylene terephthalate, a polyester film, a thermoplastic polyimide, a thermosetting polyimide, a polyamide-imide, a polyether imide, a ground-to-ground fiber film, a polyamide film, a metal film, an alloy film, a ceramic film, a molecular sieve composite film, a zeolite film, or a glass film.
3. The method for preparing a negative electrode active material coated lithium ion battery separator according to claim 1 or 2, comprising:
a. adding the polymer substrate into a solvent, and stirring to form stable slurry A;
b. adding a conductive agent into the slurry, and uniformly stirring to form slurry B;
c. adding the negative electrode active material into the slurry B, and uniformly dispersing to obtain a slurry C;
d. and uniformly coating the slurry C on the base film, and removing the solvent.
4. The method for preparing a negative active material coated lithium ion battery separator according to claim 3, wherein the mass of the solvent is 60 to 80% of the total mass of the slurry C.
5. The method for preparing a negative electrode active material coated lithium ion battery separator according to claim 3, wherein the steps a to c are performed in a closed container.
6. The method for preparing a lithium ion battery diaphragm coated with a negative electrode active material according to claim 3, wherein in the step c, the uniform dispersion is carried out by stirring uniformly and ultrasonic dispersion is carried out, and stirring is continued after ultrasonic treatment;
and d, uniformly coating the slurry C on the base film by spraying, casting, screen printing, dip-coating or electrophoresis.
7. The method for preparing a negative electrode active material coated lithium ion battery separator according to claim 6, wherein the stirring is 500-1000 r/min for 12-24 hours.
8. The method for preparing a negative electrode active material coated lithium ion battery separator according to claim 6, wherein the ultrasonic wave is 30 to 40kHz for 25 to 35 minutes.
9. The method for producing a negative electrode active material-coated lithium ion battery separator according to claim 3 or 4, wherein the solvent is at least one selected from the group consisting of N-methylpyrrolidone, acetone, 1, 3-dioxolane, 1, 2-dimethoxyethane, tetraethyleneglycol dimethyl ether, poly (ethyleneglycol) dimethyl ether, diethyleneglycol dibutyl ether, 2-ethoxyethyl ether, ethylene carbonate, dimethyl carbonate, methylethyl carbonate, methyl carbonate, benzene, toluene, xylene, methyl acetate, fluoroethylene carbonate, vinylene carbonate, allyl ethyl carbonate, hydrofluoroether, an ionic liquid solvent, cyclohexane, cyclohexanone, toluene cyclohexanone, chlorobenzene, dichlorobenzene, dichloromethane, isopropyl alcohol, diethyl ether, propylene oxide, methyl acetate, ethyl acetate, propyl acetate, acetone, methyl butanone, methyl isobutyl Ding Tonger ethyl acetate, ethyl propionate, methyl propionate, propylene carbonate, γ -butyrolactone, acetonitrile, ethyl acetate, propyl formate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetonitrile, pyridine, phenol.
10. Use of a negative electrode active material coated lithium ion battery separator according to claim 1 or 2 for the preparation of a lithium ion battery, the positive electrode of which faces the second layer film and the negative electrode faces the first layer film.
11. The use according to claim 10, wherein the negative electrode active material is contained in a material of a positive electrode of the battery.
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| CN115020920A (en) * | 2022-04-21 | 2022-09-06 | 电子科技大学长三角研究院(湖州) | Integrated preparation method of lithium battery diaphragm and battery |
| CN115579508A (en) * | 2022-09-28 | 2023-01-06 | 电子科技大学长三角研究院(湖州) | Sodium ion battery diaphragm and preparation method thereof |
| CN116632455B (en) * | 2023-07-20 | 2023-10-20 | 宁德新能源科技有限公司 | Separator, electrochemical device including the same, and electronic device |
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