CN114142176B - Battery cell - Google Patents
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- CN114142176B CN114142176B CN202111449035.XA CN202111449035A CN114142176B CN 114142176 B CN114142176 B CN 114142176B CN 202111449035 A CN202111449035 A CN 202111449035A CN 114142176 B CN114142176 B CN 114142176B
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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
- H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
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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
- H01M10/05—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
- 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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
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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
- H01M50/417—Polyolefins
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- 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
Abstract
The invention provides a battery which has long circulation and low expansion, wherein a diaphragm in the battery comprises a polymer layer, the polymer layer comprises a first polymer and a second polymer, the arrangement of the first polymer and the second polymer not only can promote the dry pressure bonding force between the diaphragm and positive and negative pole pieces, but also can promote the wet pressure bonding force between the diaphragm and the positive and negative pole pieces, ensure that the battery has good bonding property and avoids deformation after the battery circulates, ensure that the bonding retention rate of the bonding force between the diaphragm and the positive and negative pole pieces after the battery circulates for 200 weeks is more than or equal to 90%, ensure that the positive and negative pole pieces of the battery have better interfaces so as to reduce the circulation expansion, further reduce the damage and recombination of SEI films, thereby improving the stability of a positive electrode material under high temperature and high voltage, effectively improving the circulation life of the battery and simultaneously effectively reducing the circulation expansion of the battery.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a battery, in particular to a long-cycle low-expansion battery.
Background
In recent years, batteries have been widely used in the fields of smart phones, tablet computers, smart wear, electric tools, electric automobiles, and the like. With the widespread use of batteries, consumer demands for the service life of batteries have increased, which has required that batteries have a long cycle life.
At present, the battery has potential safety hazards in the use process, for example, when the battery is used for a long time, the battery has the problems of increased thickness expansion and the like, and serious safety accidents, such as fire and even explosion, are easily caused. The main reason for the above problem is that the interface between the separator and the pole piece becomes poor as the cycle time of the battery increases, and the main reason for the interface between the separator and the pole piece becomes poor is that the adhesion between the separator and the pole piece decreases as the cycle time increases.
Based on this current situation, development of a battery having a long cycle life and low expansion is urgently required.
Disclosure of Invention
In order to solve the problems of serious adhesive force attenuation and the like between a diaphragm and a pole piece in the using process of the traditional battery, the invention provides a battery which has long cycle life and low expansibility. The invention can slowly attenuate the bonding force between the diaphragm and the pole piece along with the increase of the circulation time by increasing the bonding stability between the diaphragm and the pole piece.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a battery includes a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and a nonaqueous electrolytic solution;
the separator includes a substrate, a heat resistant layer disposed on a first surface of the substrate, and a polymer layer disposed on a second surface of the substrate opposite the first surface and/or on the heat resistant layer;
the polymer layer includes a first polymer and a second polymer; the first polymer is a copolymer of a first monomer and a second monomer; the second polymer is a copolymer of a third monomer and a fourth monomer;
the first monomer comprises at least one of vinylidene fluoride, methacrylic acid ester (such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate) and acrylonitrile; the second monomer comprises at least one of perfluoropropylene, trifluorochloroethylene, tetrafluoroethylene, chloroethylene, styrene, vinylidene chloride and tetrachloroethylene;
the third monomer comprises at least one of vinylidene fluoride, methacrylic acid ester (such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate) and acrylonitrile; the fourth monomer comprises at least one of perfluoropropylene, trifluorochloroethylene, tetrafluoroethylene, chloroethylene, styrene, vinylidene chloride and tetrachloroethylene;
wherein the number average molecular weight of the first polymer is less than the number average molecular weight of the second polymer.
According to the invention, the number average molecular weight of the first polymer is 5 to 50 tens of thousands; the second polymer has a number average molecular weight of greater than 50 ten thousand, and is exemplified by greater than 50 ten thousand to 200 ten thousand or less.
According to the present invention, in the first polymer, the mass of the second monomer is 0.5% to 20% of the total mass of the first monomer and the second monomer, for example, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%, 12%, 14%, 15%, 16%, 18% or 20%. Within this range, the first polymer may achieve better dry-press bond properties.
According to the present invention, in the second polymer, the mass of the fourth monomer is 0.5% to 10%, for example, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 9% or 10% of the total mass of the third monomer and the fourth monomer. Within this range, the second polymer may achieve better wet-press bonding properties.
It has been found that the first polymer can provide dry pressure adhesion to the separator and the second polymer can provide wet pressure adhesion to the separator, and the combined use of the first and second polymers can increase the adhesion stability between the separator and the pole piece, allowing the adhesion between the separator and the pole piece to decay slowly with increasing cycle time.
According to the invention, the mass ratio of the first polymer to the second polymer is (5-50): (95-50), for example 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55 or 50:50.
According to the invention, the thickness of the polymer layer is 0.5 μm to 2 μm, exemplary 0.5 μm, 1 μm or 2 μm.
According to the invention, the adhesion between the polymer layer and the positive electrode sheet is 5N/m or more.
According to the invention, the adhesion between the polymer layer and the negative electrode sheet is 5N/m or more.
According to the present invention, the adhesion retention rate between the polymer layer and the positive electrode sheet is 90% or more after 200 weeks (25 ℃,1C rate) of the battery cycle.
According to the present invention, the adhesion retention between the polymer layer and the negative electrode sheet was 90% or more after 200 weeks (25 ℃,1C rate) of the battery cycle.
According to the invention, the heat resistant layer comprises a ceramic and a binder.
Preferably, the mass of the ceramic in the heat-resistant layer is 20 to 99wt.%, illustratively 20wt.%, 30wt.%, 40wt.%, 60wt.%, 80wt.%, 90wt.%, 95wt.%, 99wt.%, or any value in the range of the numerical compositions stated above.
Preferably, the mass of the binder in the heat-resistant layer is 1 to 80wt.%, illustratively 1wt.%, 5wt.%, 10wt.%, 20wt.%, 30wt.%, 50wt.%, 60wt.%, 80wt.%, or any value in the range of the numerical compositions stated above for each other.
According to the present invention, the ceramic in the heat-resistant layer is selected from one, two or more of alumina, boehmite, magnesium oxide, boron nitride and magnesium hydroxide.
According to the present invention, the binder in the heat-resistant layer is selected from one, two or more of polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer (for example, polyvinylidene fluoride-hexafluoropropylene copolymer), polyimide, polyacrylonitrile, and polymethyl methacrylate.
According to the invention, the thickness of the heat-resistant layer is 0.5 μm to 5 μm, for example 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.
According to the invention, the thickness of the substrate is 3 μm to 20 μm, for example 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 18 μm or 20 μm.
According to the invention, the substrate is at least one selected from the group consisting of polyethylene, polypropylene, polyethylene and polypropylene composites, polyamide, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyparaphenylene.
According to the invention, the separator is disposed between the positive electrode sheet and the negative electrode sheet.
According to the invention, the first surface of the base material is close to the negative electrode sheet, and the second surface of the base material opposite to the first surface is close to the positive electrode sheet.
According to the invention, the battery is, for example, a lithium ion battery.
According to the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both side surfaces of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, a conductive agent, and a binder.
According to the present invention, the positive electrode active material is selected from lithium cobalt oxide (LiCoO) 2 ) Or lithium cobalt oxide (LiCoO) subjected to coating treatment by doping two or more elements in Al, mg, mn, cr, ti, zr 2 ) The chemical formula of the lithium cobaltate subjected to the doping and coating treatment of two or more elements in Al, mg, mn, cr, ti, zr is Li x Co 1-y1-y2-y3-y4 A y1 B y2 C y3 D y4 O 2 The method comprises the steps of carrying out a first treatment on the surface of the X is more than or equal to 0.95 and less than or equal to 1.05,0.01, y1 is more than or equal to 0.1, y2 is more than or equal to 0.01 and less than or equal to 0.1, y3 is more than or equal to 0 and less than or equal to 0.1, y4 is more than or equal to 0 and less than or equal to 0.1, and A and B, C, D are selected from two or more elements of Al, mg, mn, cr, ti, zr.
According to the present invention, the conductive agent in the positive electrode active material layer is selected from acetylene black, and the amount of the conductive agent is 0.01 to 5wt% based on the total mass of the positive electrode active material layer.
According to the present invention, the binder in the positive electrode active material layer is selected from polyvinylidene fluoride (PVDF), and the amount of the binder is 0.01 to 5wt% based on the total mass of the positive electrode active material layer.
According to the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both side surfaces of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder.
According to the present invention, the negative electrode active material is selected from graphite.
According to the present invention, the anode active material further optionally contains SiOx/C or Si/C, wherein 0< x <2. For example, the negative electrode active material further contains 1 to 15wt% siox/C or Si/C, and is exemplified by 1 wt%, 2wt%, 5wt%, 8 wt%, 10 wt%, 12 wt%, 15wt%, or any point value in the range of the foregoing numerical compositions.
According to the present invention, the conductive agent in the anode active material layer is selected from acetylene black, and the amount of the conductive agent is 0.01 to 5wt% based on the total mass of the anode active material layer.
According to the present invention, the binder in the anode active material layer is selected from sodium carboxymethyl cellulose, and the amount of the binder is 0.01 to 5wt% of the total mass of the anode active material layer.
According to the invention, the battery has a charge cut-off voltage of 4.45V or more.
The invention has the beneficial effects that:
the invention provides a battery which has long circulation and low expansion, wherein a diaphragm in the battery comprises a polymer layer, the polymer layer comprises a first polymer and a second polymer, the arrangement of the first polymer and the second polymer not only can promote the dry pressure bonding force between the diaphragm and positive and negative pole pieces, but also can promote the wet pressure bonding force between the diaphragm and the positive and negative pole pieces, ensure that the battery has good bonding property and avoids deformation after the battery circulates, ensure that the bonding retention rate of the bonding force between the diaphragm and the positive and negative pole pieces after the battery circulates for 200 weeks is more than or equal to 90%, ensure that the positive and negative pole pieces of the battery have better interfaces so as to reduce the circulation expansion, further reduce the damage and recombination of SEI films, thereby improving the stability of a positive electrode material under high temperature and high voltage, effectively improving the circulation life of the battery and simultaneously effectively reducing the circulation expansion of the battery.
Drawings
Fig. 1: a schematic cross-sectional view of a separator according to a preferred embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the examples described below are commercially available unless otherwise specified.
The preparation methods of the first polymer and the second polymer used in the following examples were prepared by methods known in the art.
In the description of the present invention, it should be noted that the terms "first," "second," "third," "fourth," and the like are used for descriptive purposes only and are not indicative or implying relative importance.
Comparative examples 1 to 4 and examples 1 to 10
The lithium ion batteries of comparative examples 1 to 4 and examples 1 to 10 were each prepared according to the following preparation method, except that the first polymer and the second polymer in the separator surface polymer layer were different, and the specific differences are shown in table 1.
(1) Preparation of positive plate
LiCoO as positive electrode active material 2 Mixing polyvinylidene fluoride (PVDF) as a binder and acetylene black as a conductive agent according to a weight ratio of 98:1.0:1.0, adding N-methylpyrrolidone (NMP), and stirring under the action of a vacuum stirrer until the mixed system forms anode slurry with uniform fluidity; uniformly coating the anode slurry on an aluminum foil with the thickness of 10 mu m; and baking the coated aluminum foil in 5 sections of ovens with different temperature gradients, drying the aluminum foil in an oven with the temperature of 120 ℃ for 8 hours, and rolling and slitting the aluminum foil to obtain the required positive plate.
(2) Preparation of negative plate
The preparation method comprises the steps of preparing a slurry from 97% by mass of artificial graphite anode material, 0.1% by mass of single-walled carbon nanotube (SWCNT) conductive agent, 0.8% by mass of conductive carbon black (SP) conductive agent, 1% by mass of sodium carboxymethylcellulose (CMC) binder and 1.1% by mass of styrene-butadiene rubber (SBR) binder by a wet process, coating the slurry on the surface of a copper foil with the thickness of 6 mu m of an anode current collector, and drying (temperature: 85 ℃ for 5 hours), rolling and die cutting to obtain the anode sheet.
(3) Preparation of nonaqueous electrolyte
In a glove box filled with argon (moisture)<10ppm, oxygen content<1 ppm), ethylene Carbonate (EC), propylene Carbonate (PC) and Propyl Propionate (PP) were uniformly mixed in a mass ratio of 2:1.5:2, and 14wt.% LiPF based on the total mass of the nonaqueous electrolytic solution was slowly added to the mixed solution 6 Stirring uniformly to obtain the non-aqueous electrolyte.
(4) Preparation of separator
The first polymer and the second polymer (the relevant parameters of the first polymer and the second polymer are defined as shown in Table 1) in a specific mass ratio were dispersed in DMAC by stirring at a stirring speed of 1500rpm for 120min in a ratio of 6% solids, to obtain a slurry L comprising the first polymer and the second polymer.
A first surface of a polyethylene substrate having a thickness of 5 μm was coated with an alumina layer having a thickness of 2 μm (composition of 92wt% alumina, 4wt% methacrylic acid, 4wt% sodium polymethyl cellulose), a second surface of the polyethylene substrate opposite to the first surface and the surface of the alumina layer were each coated with a polymer layer having a thickness of 2 μm, specifically, slurry L was coated on both sides of the polyethylene substrate having a thickness of 5 μm and the alumina layer having a thickness of 2 μm by using a gravure roll coating method, and a separator having both sides of each polymer layer having a thickness of 2 μm was obtained after drying, as shown in fig. 1.
(5) Preparation of lithium ion batteries
Winding the prepared positive plate, diaphragm and negative plate to obtain a bare cell without liquid injection (wherein the first surface of the polyethylene base material is close to one side of the negative plate, and the second surface of the polyethylene base material opposite to the first surface is close to one side of the positive plate); and placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried bare cell, and performing the procedures of vacuum packaging, standing, formation, secondary packaging, sorting and the like to obtain the required lithium ion battery.
Table 1 lithium ion batteries prepared in comparative examples 1 to 4 and examples 1 to 10
Electrochemical performance tests were performed on the batteries obtained in the above comparative examples and examples, and the following description is given below:
(1) 25 ℃ cycle experiment:
placing the batteries obtained in the examples and the comparative examples in an environment with the temperature of (25+/-2), standing for 2-3h, when the battery body reaches the temperature of (25+/-2), charging the battery according to the constant current of 1C to stop current of 0.05C, standing for 5min after the battery is fully charged, discharging the battery to the stop voltage of 3.0V by the constant current of 1C, recording the highest discharge capacity of the previous 3 weeks of circulation as initial capacity Q, and recording the discharge capacity Q of the last week of the battery circulation when the circulation cycle number reaches 1000 weeks 1 The method comprises the steps of carrying out a first treatment on the surface of the The initial thickness T of the cell was recorded, and the thickness when cycled to 1000 weeks was recorded as T 1 The results are recorded in table 2.
The calculation formula used therein is as follows:
capacity retention (%) =q 1 Q.times.100%; thickness change rate (%) = (T) 1 -T)/T×100％。
(2) The method for measuring the binding force between the polymer layer on the surface of the diaphragm and the negative electrode comprises the following steps:
placing the batteries obtained in the examples and the comparative examples in an environment of (25+/-2), standing for 2-3h, when the battery body reaches (25+/-2), charging the batteries according to a constant current of 0.7C, wherein the cutoff current is 0.05C, changing the battery terminal voltage to constant voltage charge until the charging current is less than or equal to the cutoff current, stopping charging and standing for 5min, dissecting the fully charged batteries, selecting a diaphragm with a length of 30mm and a width of 15mm along the tab direction, testing the diaphragm and the negative electrode on a universal stretcher at a speed of 100mm/min and with a test displacement of 50mm, wherein the test result is recorded as the adhesive force N (unit N/m) between the diaphragm and the negative electrode, the adhesive force tested by the fresh batteries is N1 (unit N/m), and the adhesive force tested by the batteries in 200 cycles is N2 (unit N/m);
the calculation formula used therein is as follows:
change rate of adhesion between separator surface polymer layer and anode (%) = (N1-N2)/n1×100%
Table 2 results of experimental tests on batteries obtained in comparative examples 1 to 4 and examples 1 to 10
From the results in table 2, it can be seen that: according to the invention, through the synergistic effect of the first polymer and the second polymer in the diaphragm, not only is the dry pressure bonding force between the diaphragm and the positive and negative pole pieces improved, but also the wet pressure bonding force between the diaphragm and the positive and negative pole pieces is improved, the battery is ensured to have good bonding property so as to avoid deformation after the battery is circulated, the bonding force between the diaphragm and the positive and negative pole pieces is ensured to be slowly attenuated, so that the positive and negative pole pieces of the battery have better interfaces so as to reduce the circulating expansion, and further the damage and recombination of CEI films are reduced, thereby improving the stability of the positive electrode material under high temperature and high voltage, effectively prolonging the circulating life of the battery, and simultaneously effectively reducing the circulating expansion of the battery.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A battery includes a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and a nonaqueous electrolytic solution; wherein the separator comprises a substrate, a heat resistant layer disposed on a first surface of the substrate, and a polymer layer disposed on a second surface of the substrate opposite the first surface and/or on the heat resistant layer;
the polymer layer includes a first polymer and a second polymer; the first polymer is a copolymer of a first monomer and a second monomer; the second polymer is a copolymer of a third monomer and a fourth monomer;
the first monomer comprises at least one of vinylidene fluoride, methacrylic acid, methacrylate and acrylonitrile; the second monomer comprises at least one of perfluoropropylene, trifluorochloroethylene, tetrafluoroethylene, chloroethylene, styrene, vinylidene chloride and tetrachloroethylene;
the third monomer comprises at least one of vinylidene fluoride, methacrylic acid, methacrylate and acrylonitrile; the fourth monomer comprises at least one of perfluoropropylene, trifluorochloroethylene, tetrafluoroethylene, chloroethylene, styrene, vinylidene chloride and tetrachloroethylene;
wherein the number average molecular weight of the first polymer is less than the number average molecular weight of the second polymer;
in the first polymer, the mass of the second monomer accounts for 0.5-20% of the total mass of the first monomer and the second monomer; in the second polymer, the mass of the fourth monomer accounts for 0.5-2% of the total mass of the third monomer and the fourth monomer;
the number average molecular weight of the first polymer is 5-50 ten thousand; the number average molecular weight of the second polymer is more than 50 ten thousand and less than or equal to 200 ten thousand;
the mass ratio of the first polymer to the second polymer is (10-30): 90-70.
2. The battery of claim 1, wherein the thickness of the polymer layer is 0.5 μιη to 2 μιη.
3. The battery according to claim 1, wherein the heat-resistant layer has a thickness of 0.5 μm to 5 μm.
4. The battery according to any one of claims 1 to 3, wherein a binding force between the polymer layer and the positive electrode sheet is 5N/m or more;
and/or the adhesive force between the polymer layer and the negative plate is more than or equal to 5N/m.
5. The battery according to any one of claims 1 to 3, wherein a retention of adhesion between the polymer layer and the positive electrode sheet is 90% or more after cycling at 25 ℃ and 1C magnification for 200 weeks;
and/or, after the battery is cycled for 200 weeks at 25 ℃ and 1C multiplying power, the bonding retention rate between the polymer layer and the negative plate is more than or equal to 90%.
6. A battery according to any one of claims 1-3, wherein the heat resistant layer comprises a ceramic and a binder.
7. The battery of claim 6, wherein the mass of ceramic in the heat resistant layer is 20wt.% to 99wt.% of the total mass of the heat resistant layer, and the mass of binder in the heat resistant layer is 1wt.% to 80wt.% of the total mass of the heat resistant layer.
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| KR101904296B1 (en) * | 2015-12-22 | 2018-11-13 | 삼성에스디아이 주식회사 | A separator comprising porous bonding layer and an electrochemical battery comprising the separator |
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| JP2012048917A (en) * | 2010-08-25 | 2012-03-08 | Sony Corp | Positive electrode, nonaqueous electrolyte battery, positive electrode mixture, and binder |
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