CN116780097A - Porous functional coating diaphragm, preparation method thereof and lithium ion battery - Google Patents
Porous functional coating diaphragm, preparation method thereof and lithium ion battery Download PDFInfo
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- CN116780097A CN116780097A CN202310850028.3A CN202310850028A CN116780097A CN 116780097 A CN116780097 A CN 116780097A CN 202310850028 A CN202310850028 A CN 202310850028A CN 116780097 A CN116780097 A CN 116780097A
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- 239000011248 coating agent Substances 0.000 title claims abstract description 89
- 238000000576 coating method Methods 0.000 title claims abstract description 89
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 31
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 239000002131 composite material Substances 0.000 claims abstract description 82
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims abstract description 58
- 239000004926 polymethyl methacrylate Substances 0.000 claims abstract description 58
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 57
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 57
- 230000001502 supplementing effect Effects 0.000 claims abstract description 51
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims abstract description 41
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 39
- 238000000034 method Methods 0.000 claims abstract description 39
- 238000007731 hot pressing Methods 0.000 claims abstract description 37
- 230000008569 process Effects 0.000 claims abstract description 32
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 30
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 24
- 239000011148 porous material Substances 0.000 claims abstract description 22
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 8
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 8
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 8
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 8
- 239000002002 slurry Substances 0.000 claims description 42
- 238000003756 stirring Methods 0.000 claims description 42
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 27
- 239000012528 membrane Substances 0.000 claims description 11
- 238000001953 recrystallisation Methods 0.000 claims description 10
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 7
- 239000012047 saturated solution Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 6
- 239000003792 electrolyte Substances 0.000 claims description 5
- 239000003960 organic solvent Substances 0.000 claims description 5
- 239000007774 positive electrode material Substances 0.000 claims description 5
- 238000005096 rolling process Methods 0.000 claims description 5
- 238000011049 filling Methods 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 3
- 239000010439 graphite Substances 0.000 claims description 3
- 239000007773 negative electrode material Substances 0.000 claims description 3
- 238000004804 winding Methods 0.000 claims description 3
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 2
- 239000004966 Carbon aerogel Substances 0.000 claims description 2
- 239000004917 carbon fiber Substances 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 2
- 239000008236 heating water Substances 0.000 claims description 2
- 239000013589 supplement Substances 0.000 claims description 2
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 claims 1
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical group [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 claims 1
- 150000002500 ions Chemical class 0.000 abstract description 8
- 239000002033 PVDF binder Substances 0.000 description 14
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 14
- 239000010410 layer Substances 0.000 description 12
- 239000000758 substrate Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 230000035699 permeability Effects 0.000 description 9
- 210000004027 cell Anatomy 0.000 description 8
- 239000011230 binding agent Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 239000000853 adhesive Substances 0.000 description 6
- 230000001070 adhesive effect Effects 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000004698 Polyethylene Substances 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- 239000008367 deionised water Substances 0.000 description 5
- 229910021641 deionized water Inorganic materials 0.000 description 5
- 229920000573 polyethylene Polymers 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 239000004743 Polypropylene Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 238000004090 dissolution Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 229920001155 polypropylene Polymers 0.000 description 4
- 230000000903 blocking effect Effects 0.000 description 3
- 238000013329 compounding Methods 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 230000000704 physical effect Effects 0.000 description 3
- 238000009423 ventilation Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- -1 Polyethylene Polymers 0.000 description 2
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000004026 adhesive bonding Methods 0.000 description 1
- 239000012790 adhesive layer Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 210000000170 cell membrane Anatomy 0.000 description 1
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- 239000006188 syrup Substances 0.000 description 1
- 235000020357 syrup Nutrition 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
Classifications
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
Abstract
The invention belongs to the technical field of batteries, relates to a lithium ion battery diaphragm, and in particular relates to a porous functional coating diaphragm, a preparation method thereof and a lithium ion battery. The porous functional coating diaphragm comprises a diaphragm base layer and a porous functional coating, wherein the porous functional coating is positioned on one side of the diaphragm base layer, the porous functional coating is formed by mixing PMMA and a lithium supplementing composite material, the lithium supplementing composite material is a composite material of lithium oxalate and porous carbon, the lithium oxalate is filled in a pore channel structure of the porous carbon, and/or the surface of the porous carbon is coated with the lithium oxalate; when the diaphragm is used for preparing the lithium ion battery, in the hot pressing process, the diaphragm and the positive plate are bonded together by the porous functional coating; in the formation process, lithium oxalate in the lithium supplementing composite material is decomposed into lithium salt and carbon dioxide. The invention can improve the ion passing efficiency of the diaphragm after hot pressing and can endow the bonding layer with the lithium supplementing function.
Description
Technical Field
The invention belongs to the technical field of batteries, relates to a lithium ion battery diaphragm, and in particular relates to a porous functional coating diaphragm, a preparation method thereof and a lithium ion battery.
Background
The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.
The diaphragm is used as one of four main materials of the lithium ion battery, and plays a role in blocking contact short circuit of the anode and the cathode, and meanwhile, the micropore structure provides an effective channel for ions, so that a complete charge-discharge loop is formed. Currently, commercially used separator materials are mainly made of Polyethylene (PE) and polypropylene (PP), and are coated with ceramic or high temperature resistant organic materials to improve high temperature resistance. In order to improve the hardness of the battery cell and improve the interface performance of the diaphragm and the pole piece, a layer of bonding layer is added. The common gluing means is mainly aqueous/oil-based polyvinylidene fluoride (PVDF) coating, but has the problems of increased air permeability, hole blocking and the like, so that the internal resistance of the battery is increased. On the other hand, in the process of first charge and discharge of the lithium ion battery, part of active lithium ions are consumed due to the formation of the SEI film, so that the first charge and discharge efficiency is low, and the capacity and energy density of the lithium ion battery are reduced.
The industry typically employs oil-based PVDF coating to create holes to improve air permeability or spray coating to reduce air permeability. The inventors found that the following problems exist in the pore-forming process adopted to improve the problem of air permeability increase in the process of coating PVDF in oil systems at present: 1. the pore-forming agent is added, the pore is formed after extraction and solidification, the process is complex, and the cost is high; 2. the porous PVDF coating diaphragm is easy to collapse in the hot pressing process of the battery core, so that ventilation is increased, and the rate performance of the battery is affected.
Disclosure of Invention
The invention aims to provide a porous functional coating diaphragm, a preparation method thereof and a lithium ion battery in order to improve the ion passing efficiency of the diaphragm after hot pressing and enable the lithium supplementing function of an adhesive layer.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
in one aspect, the porous functional coating diaphragm comprises a diaphragm base layer and a porous functional coating, wherein the porous functional coating is positioned on one side of the diaphragm base layer, the porous functional coating is formed by mixing PMMA (polymethyl methacrylate) and a lithium supplementing composite material, the lithium supplementing composite material is a composite material of lithium oxalate and porous carbon, the lithium oxalate is filled in a pore channel structure of the porous carbon, and/or the lithium oxalate is coated on the surface of the porous carbon;
when the diaphragm is used for preparing the lithium ion battery, in the hot pressing process, the diaphragm and the positive plate are bonded together by the porous functional coating; in the formation process, lithium oxalate in the lithium supplementing composite material is decomposed into lithium salt and carbon dioxide.
In order to avoid channel blockage caused by channel collapse in the hot pressing process, the invention adopts the binder and the porous material, and by compounding the lithium supplementing agent in the porous material in advance, the invention not only can avoid the blocking of the channel by the binder in the hot pressing process, but also can supplement lithium to the porous functional coating. The lithium oxalate is selected as a lithium supplementing agent, and can be decomposed in the formation process, so that pore channels in the porous material are vacated, and the porous carbon is selected to reduce the decomposition voltage of the lithium oxalate in the formation process, so that the battery performance is effectively improved. However, when the conventional PVDF adhesive is adopted, the adhesion between the porous functional coating formed by compounding the PVDF adhesive and the pole piece is obviously reduced due to the addition of the lithium supplementing composite material, and the adhesion between the diaphragm and the pole piece is not facilitated, so that PMMA is selected as the adhesive, the adhesion between the porous functional coating formed by compounding the PMMA and the lithium supplementing composite material and the pole piece is not obviously reduced, the adhesion between the diaphragm and the pole piece is facilitated, and the hardness and the interface performance of the battery cell are ensured.
On the other hand, the preparation method of the porous functional coating diaphragm comprises the following steps:
filling lithium oxalate into a pore channel structure of the porous carbon and/or coating the lithium oxalate on the surface of the porous carbon through recrystallization to obtain a lithium supplementing composite material;
dispersing PMMA into an organic solvent to obtain PMMA slurry;
adding the lithium supplementing composite material into PMMA slurry, uniformly dispersing to obtain composite slurry, and rolling the composite slurry on one side surface of the diaphragm base layer to form a porous functional coating by the composite slurry.
In a third aspect, the lithium ion battery is a hot-pressing composite battery cell, and comprises a positive plate, the porous functional coating diaphragm, electrolyte and a negative plate, wherein the positive plate, the porous functional coating diaphragm and the negative plate are formed by hot-pressing composite.
The beneficial effects of the invention are as follows:
compared with the traditional lithium supplementing agent, the lithium oxalate is selected, is easy to store and use, is compounded with porous carbon (especially ordered mesoporous carbon), and is decomposed into lithium salt and carbon dioxide in the formation stage, wherein the lithium salt is used as the lithium supplementing agent to participate in the lithium ion circulation of the battery, and the generated carbon dioxide gas is discharged in the formation stage; meanwhile, the addition of the porous carbon can effectively reduce the decomposition voltage of lithium oxalate. The battery core (lithium ion battery) manufactured by the porous functional coating diaphragm provided by the invention has obvious improvement in the aspects of initial coulomb efficiency and cycle performance, and the higher the initial coulomb efficiency is, the better the lithium supplementing effect is, the more a lithium source is used for forming an SEI film, the utilization rate of active lithium of a positive electrode material is increased, and the cycle life is prolonged. And lithium oxalate in the ordered mesoporous carbon is decomposed into battery circulation, and the vacated channels provide lithium ion shuttling, so that pore-forming effect is achieved, the ventilation value of the diaphragm is reduced, and the liquid retention capacity and the ion passing rate of the diaphragm are improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is an SEM image of ordered mesoporous carbon CMK-3 employed in an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a porous functional coating membrane prepared by the embodiment of the invention, namely 1 a lithium supplementing composite material, 2 a PMMA binder, and 3 a lithium supplementing composite material.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
In view of the problems that the existing method for improving the air permeability by diaphragm pore-forming is not suitable for hot-pressing a composite battery core, and part of active lithium ions are consumed when SEI is formed in the first charge and discharge process of a lithium ion battery, the invention provides a porous functional coating diaphragm, a preparation method thereof and the lithium ion battery.
According to an exemplary embodiment of the invention, a porous functional coating diaphragm is provided, and comprises a diaphragm base layer and a porous functional coating, wherein the porous functional coating is positioned on one side of the diaphragm base layer, the porous functional coating is formed by mixing PMMA (polymethyl methacrylate) and a lithium supplementing composite material, the lithium supplementing composite material is a composite material of lithium oxalate and porous carbon, the lithium oxalate is filled in a pore channel structure of the porous carbon, and/or the lithium oxalate is coated on the surface of the porous carbon;
when the diaphragm is used for preparing the lithium ion battery, in the hot pressing process, the diaphragm and the positive plate are bonded together by the porous functional coating; in the formation process, lithium oxalate in the lithium supplementing composite material is decomposed into lithium salt and carbon dioxide.
In the hot pressing process, PMMA bonds the diaphragm and the pole piece together, so that the hardness and interface performance of the battery cell are ensured. In the formation process, lithium oxalate in the ordered mesoporous carbon is decomposed into lithium salt and carbon dioxide, and the carbon dioxide is discharged in an exhaust process. While the lithium salt will dissolve in the electrolyte and participate in the battery cycle. The channel vacated by the mesoporous carbon can be provided for lithium ion shuttle, so that the liquid retention capacity and the ion passing rate of the diaphragm are improved.
Through PMMA and lithium supplementing composite material, the pore canal of ordered mesoporous carbon is not easy to be filled with PMMA to block the pore canal due to the filling of lithium oxalate in the hot pressing process. In the formation process, lithium oxalate is decomposed, and the pore canal is used for ions to pass through, so that compared with the traditional bonding layer, the pore structure is formed after the hot pressing process of the battery cell, and collapse in the hot pressing process is avoided, so that the lithium-supplementing bonding layer has a higher pore structure, and lithium supplementing and energizing are carried out on the bonding layer.
In some embodiments, the porous carbon is one or more of ordered mesoporous carbon CMK-3, nanoporous carbon NCP, porous activated carbon, porous carbon nanotubes, porous carbon fibers, and porous carbon aerogels. Ordered mesoporous carbon CMK-3 is preferred.
In some embodiments, the mass ratio of PMMA to lithium-supplemented composite is 8-10:2-5.
In some embodiments, the membrane substrate is a membrane substrate or a ceramic composite membrane. The diaphragm base material is PP or PE. The ceramic composite diaphragm is made of a composite material of polymer and ceramic, and the polymer is PP or PE.
In another embodiment of the present invention, a method for preparing the porous functional coating membrane is provided, including the following steps:
filling lithium oxalate into a pore channel structure of the porous carbon and/or coating the lithium oxalate on the surface of the porous carbon through recrystallization to obtain a lithium supplementing composite material;
dispersing PMMA into an organic solvent to obtain PMMA slurry;
adding the lithium supplementing composite material into PMMA slurry, uniformly dispersing to obtain composite slurry, and rolling the composite slurry on one side surface of the diaphragm base layer to form a porous functional coating by the composite slurry.
In some embodiments, the lithium-supplemented composite is prepared by recrystallization by: heating water to 80-100 ℃, adding lithium oxalate to prepare saturated solution, adding porous carbon to disperse uniformly, cooling to 0-50 ℃, and filtering to obtain the lithium supplementing composite material. The stirring speed after adding the porous carbon and dispersing uniformly is 500-1000 r/min, and the stirring time is 10-40 min.
In one or more embodiments, the mass ratio of water, lithium oxalate, and porous carbon is 80-100:2-8:5-15.
In some embodiments, the organic solvent used in preparing the PMMA syrup is N-methylpyrrolidone.
In some embodiments, a planetary mixer is used to mix the PMMA slurry. The stirring time is 60-90 min, the stirring speed revolution is 30-40 r/min, and the rotation is 800-1500 r/min.
In some embodiments, the PMMA particles range in size from 0.2 to 10 μm when preparing PMMA slurry.
In some embodiments, the lithium-supplemented composite material is added to the PMMA slurry and stirred using a planetary stirrer to disperse it uniformly. The stirring time is 60-90 min, the stirring speed revolution is 30-40 r/min, and the rotation is 800-1500 r/min.
In some embodiments, the composite slurry is coated on one side of the separator substrate by gravure roll coating. The thickness of the coating is preferably 1 to 10. Mu.m. The coating speed is preferably 20 to 100m/min. The gravure roll speed ratio is preferably 50 to 120%. The oven temperature is preferably 50 to 100 ℃. The unreeling tension is preferably 10 to 30N. The oven tension is preferably 10 to 35N. The winding tension is preferably 10 to 30N.
The third embodiment of the invention provides a lithium ion battery which is a hot-pressing composite battery core and comprises a positive plate, the porous functional coating diaphragm, electrolyte and a negative plate, wherein the positive plate, the porous functional coating diaphragm and the negative plate are formed by hot-pressing composite.
Specifically, the positive electrode sheet is composed of a positive electrode material, a binder, a conductive agent, and a current collector. The positive electrode material of the positive electrode plate can be nickel cobalt lithium manganate.
Specifically, the negative electrode sheet is composed of a negative electrode material, a binder, a conductive agent, and a current collector. The negative electrode material of the negative electrode sheet may be graphite.
Specifically, the preparation process of the lithium ion battery comprises a hot pressing process, wherein the hot pressing temperature is 50-100 ℃, the hot pressing time is 20-180 s, and the hot pressing pressure is 0.1-0.6 MPa.
Specifically, the preparation process of the lithium ion battery comprises a formation process, wherein in the formation process, the charging current is 0.01-0.33 ℃, the cut-off voltage is 3.7-4.5V, the formation pressure is 0.1-0.8 MPa, and the formation temperature is 30-70 ℃.
In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail below with reference to specific examples and comparative examples.
Example 1
The preparation method of the porous functional coating diaphragm comprises the following steps:
1. and (3) preparing a lithium supplementing composite material: 100kg of deionized water is heated to 90 ℃, 3kg of lithium oxalate is added to prepare saturated solution, 5kg of ordered mesoporous carbon CMK-3 (with the surface structure shown in figure 1) is added to be dispersed and stirred by a high-speed stirrer for 30min, the stirring speed is 800r/min, the temperature is reduced to 25 ℃, and the lithium-supplementing composite material is obtained by recrystallization and filtration.
2. Preparing PMMA slurry: 10kg of PMMA is dissolved in 100kg of N methyl pyrrolidone, the mixture is stirred by a planetary stirrer for full dissolution, the stirring time is 60min, the revolution speed of stirring is 30r/min, the rotation speed is 800r/min, and the particle size of PMMA is 0.8 mu m.
3. Preparing composite slurry: and (2) adding 5kg of the lithium supplementing composite material in the step (1) into the PMMA solution obtained in the step (2), stirring and mixing by using a planetary stirrer for 75min, and rotating for 1200r/min at a stirring rate revolution of 35 r/min.
4. Coating the composite slurry in the step 3 on one side of a 9 mu m PE substrate diaphragm by using a gravure roll, wherein the thickness of the coating is 2 mu m; coating speed is 50m/min, gravure roll speed ratio is 80%, oven temperature is 80 ℃, unreeling tension is 20N, oven tension is 18N, and reeling tension is 15N.
The structure of the prepared porous functional coating diaphragm is shown in figure 2, a porous functional coating is formed on the surface of a substrate diaphragm 3, and the porous functional coating is formed by winding and bonding PMMA adhesive 2 on lithium supplementing composite material 1.
Example 2
The preparation method of the porous functional coating diaphragm comprises the following steps:
1. and (3) preparing a lithium supplementing composite material: and heating 100kg of deionized water to 90 ℃, adding 3kg of lithium oxalate to prepare a saturated solution, adding 5kg of ordered mesoporous carbon CMK-3, carrying out dispersion stirring by a high-speed stirrer for 30min, cooling to 45 ℃ for recrystallization, and filtering to obtain the lithium supplementing composite material.
2. Preparing PMMA slurry: 10kg of PMMA is dissolved in 100kg of N methyl pyrrolidone, the mixture is stirred by a planetary stirrer for full dissolution, the stirring time is 60min, the revolution speed of stirring is 30r/min, the rotation speed is 800r/min, and the particle size of PMMA is 0.8 mu m.
3. Preparing composite slurry: and (2) adding 5kg of the lithium supplementing composite material in the step (1) into the PMMA solution obtained in the step (2), stirring and mixing by using a planetary stirrer for 75min, and rotating for 1200r/min at a stirring rate revolution of 35 r/min.
4. Coating the composite slurry in the step 3 on one side of a substrate diaphragm by using a gravure roll, wherein the thickness of the coating is 2 mu m; coating speed is 50m/min, gravure roll speed ratio is 80%, oven temperature is 80 ℃, unreeling tension is 20N, oven tension is 18N, and reeling tension is 15N.
Example 3
The preparation method of the porous functional coating diaphragm comprises the following steps:
1. and (3) preparing a lithium supplementing composite material: and heating 100kg of deionized water to 90 ℃, adding 3kg of lithium oxalate to prepare a saturated solution, adding 5kg of ordered mesoporous carbon CMK-3, carrying out dispersion stirring by a high-speed stirrer for 30min, cooling to 60 ℃ for recrystallization, and filtering to obtain the lithium supplementing composite material.
2. Preparing PMMA slurry: 10kg of PMMA is dissolved in 100kg of N methyl pyrrolidone, the mixture is stirred by a planetary stirrer for full dissolution, the stirring time is 60min, the revolution speed of stirring is 30r/min, the rotation speed is 800r/min, and the particle size of PMMA is 0.8 mu m.
3. Preparing composite slurry: and (2) adding 5kg of the lithium supplementing composite material in the step (1) into the PMMA solution obtained in the step (2), stirring and mixing by using a planetary stirrer for 75min, and rotating for 1200r/min at a stirring rate revolution of 35 r/min.
4. Coating the composite slurry in the step 3 on one side of a substrate diaphragm by using a gravure roll, wherein the thickness of the coating is 2 mu m; coating speed is 50m/min, gravure roll speed ratio is 80%, oven temperature is 80 ℃, unreeling tension is 20N, oven tension is 18N, and reeling tension is 15N.
Example 4
The preparation method of the porous functional coating diaphragm comprises the following steps:
1. and (3) preparing a lithium supplementing composite material: heating 100kg of deionized water to 90 ℃, adding 3kg of lithium oxalate to prepare a saturated solution, adding 5kg of ordered mesoporous carbon CMK-3, carrying out dispersion stirring by a high-speed stirrer for 30min, cooling to 45 ℃ for recrystallization, and filtering to obtain a lithium supplementing composite material;
2. preparing PMMA slurry: 7kg of PMMA is dissolved in 100kg of N methyl pyrrolidone, the mixture is fully dissolved by stirring through a planetary stirrer, the stirring time is 60min, the revolution speed of stirring is 30r/min, the rotation speed is 800r/min, and the particle size of PMMA is 0.8 mu m;
3. preparing composite slurry: and (2) adding 5kg of the lithium supplementing composite material in the step (1) into the PMMA solution obtained in the step (2), stirring and mixing by using a planetary stirrer for 75min, and rotating for 1200r/min at a stirring rate revolution of 35 r/min.
4. Coating the composite slurry in the step 3 on one side of a substrate diaphragm by using a gravure roll, wherein the thickness of the coating is 2 mu m; coating speed is 50m/min, gravure roll speed ratio is 80%, oven temperature is 80 ℃, unreeling tension is 20N, oven tension is 18N, and reeling tension is 15N.
Comparative example 1
The preparation method of the porous functional coating diaphragm comprises the following steps:
1. and (3) preparing a lithium supplementing composite material: and heating 100kg of deionized water to 90 ℃, adding 3kg of lithium oxalate to prepare a saturated solution, adding 5kg of ordered mesoporous carbon CMK-3, carrying out dispersion stirring by a high-speed stirrer for 30min, cooling to 45 ℃ for recrystallization, and filtering to obtain the lithium supplementing composite material.
2. Preparing PVDF slurry: 10kg of PVDF is dissolved in 100kg of N methyl pyrrolidone, the PVDF is fully dissolved by stirring by a planetary stirrer, the stirring time is 60min, the stirring speed revolution is 30r/min, the rotation speed is 800r/min, and the particle size of the PVDF is 0.8 mu m.
3. Preparing composite slurry: adding 5kg of the lithium supplementing composite material in the step 1 into the PVDF solution obtained in the step 2, stirring and mixing by a planetary stirrer for 75min, and revolution of stirring speed of 35r/min and rotation of 1200r/min.
4. Coating the composite slurry in the step 3 on one side of a substrate diaphragm by using a gravure roll, wherein the thickness of the coating is 2 mu m; coating speed is 50m/min, gravure roll speed ratio is 80%, oven temperature is 80 ℃, unreeling tension is 20N, oven tension is 18N, and reeling tension is 15N.
Comparative example 2
The preparation method of the diaphragm comprises the following steps:
1. preparing PMMA slurry: 10kg of PMMA is dissolved in 100kg of N methyl pyrrolidone, the mixture is stirred by a planetary stirrer for full dissolution, the stirring time is 60min, the revolution speed of stirring is 30r/min, the rotation speed is 800r/min, and the particle size of PMMA is 0.8 mu m.
2. Coating PMMA slurry in the step 1 on one side of a substrate diaphragm by using a gravure roll, wherein the thickness of the coating is 2 mu m; coating speed is 50m/min, gravure roll speed ratio is 80%, oven temperature is 80 ℃, unreeling tension is 20N, oven tension is 18N, and reeling tension is 15N.
Preparation of a battery: and (3) stirring the nickel cobalt lithium manganate, the binder PVDF, the CNT and the conductive agent SP with the solvent NMP according to the mass ratio of 96:2:1:1 for 6 hours, coating the mixture on an aluminum foil by using a coating machine, drying, rolling and cutting to obtain the positive plate. Graphite, aqueous binder, CNT, SP in mass ratio 94:4:0.5:0.5: and 1, stirring and mixing the copper foil with a solvent, coating the slurry on the copper foil, drying, rolling, slitting, and preparing the negative plate. The electrolyte is
1mol/LLiPF6/EC+PC+DEC+EMC (volume ratio 1:0.3:1:1). The positive plate, the negative plate, the example and the comparative example diaphragm are made into a soft package battery.
And (3) hot pressing: and hot-pressing the prepared battery cell by using a hot press, wherein the hot-pressing temperature is 80 ℃, the hot-pressing time is 120s, and the hot-pressing pressure is 0.3MPa.
The formation process comprises the following steps: and (3) placing the hot-pressed battery cell on a formation cabinet for charging, wherein the charging current is 0.1 ℃, the cut-off voltage is 4.3V, the formation pressure is 0.6MPa, and the formation temperature is 45 ℃.
And after formation, the battery is subjected to air bag shearing and secondary packaging.
Physical properties of the separators of examples 1 to 4 and comparative examples 1 to 2 and electrochemical properties of the flexible battery were measured as follows:
and (3) physical property detection: air permeability test the membrane to be tested was cut into 10 x 10cm samples for testing using an Asahi EG01-55-1MR apparatus of the Japanese Asahi company; the adhesive force test is carried out by using a universal tensile testing machine, wherein the diaphragm to be tested and the pole piece are bonded in a hot-pressing mode, the hot-pressing temperature is 80 ℃, the hot-pressing time is 60S, and the sample is fixed on a tensile machine for 180-degree tensile adhesive force test after hot pressing;
and (3) testing electrical properties: and (3) performing charge and discharge tests on the battery by using a charge and discharge tester, performing charge and discharge capacity data test under the condition of 0.33 ℃, and repeating the cycle performance test.
The results of the detection are shown in tables 1 to 2.
Table 1 physical property comparison of separators of examples 1 to 4 and comparative examples 1 to 2
By comparing each example with comparative example 1 in table 1, the pole piece adhesion is significantly improved and there is some reduction compared with comparative example 2. This illustrates that PMMA has a higher pole piece adhesion than PVDF coating, and no significant downtrend was found compared to continuous phase PMMA adhesion. In the embodiment, the cell membrane after the first circle of circulation is tested, the air permeability is obviously reduced, and in the embodiment 2, the air permeability is obviously increased, which proves that lithium oxalate is decomposed into circulation, the pore channel structure of ordered mesoporous carbon provides an effective channel for ion transportation, and in the embodiment, PMMA bonding layer partially enters into the pore channels of the membrane, so that the pore channels are blocked, and the air permeability value is suddenly increased. Therefore, the pore-forming mode after thermocompression forming is favorable for the generation of ion pore canals so as to reduce the ventilation value of the diaphragm.
Table 2 electrochemical properties of the pouch batteries using the separators of examples 1 to 4 and comparative examples 1 to 2
As can be seen from table 2, in the examples, the lithium-supplementing material cell has significantly improved first-turn coulombic efficiency and cycle performance, and the higher the first-turn coulombic efficiency, the better the lithium supplementing effect, the more the lithium source is used for forming the SEI film, the more active lithium utilization rate of the positive electrode material is increased, and the cycle life is prolonged. Further, the lithium oxalate in the ordered mesoporous carbon is decomposed into the battery circulation, and the vacated channels provide lithium ion shuttling, so that the effects of pore forming and lithium supplementing are achieved.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. 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 (10)
1. The porous functional coating diaphragm is characterized by comprising a diaphragm base layer and a porous functional coating, wherein the porous functional coating is positioned on one side of the diaphragm base layer, the porous functional coating is formed by mixing PMMA (polymethyl methacrylate) and a lithium supplementing composite material, the lithium supplementing composite material is a composite material of lithium oxalate and porous carbon, the lithium oxalate is filled in a pore channel structure of the porous carbon, and/or the lithium oxalate is coated on the surface of the porous carbon;
when the diaphragm is used for preparing the lithium ion battery, in the hot pressing process, the diaphragm and the positive plate are bonded together by the porous functional coating; in the formation process, lithium oxalate in the lithium supplementing composite material is decomposed into lithium salt and carbon dioxide.
2. The porous functional coated separator of claim 1, wherein the porous carbon is one or more of ordered mesoporous carbon CMK-3, nanoporous carbon NCP, porous activated carbon, porous carbon nanotubes, porous carbon fibers, and porous carbon aerogel; ordered mesoporous carbon CMK-3 is preferred.
3. The porous functional coating diaphragm of claim 1, wherein the mass ratio of PMMA to lithium supplement composite is 8-10:2-5.
4. A method for preparing the porous functional coating membrane according to claims 1 to 3, which is characterized by comprising the following steps:
filling lithium oxalate into a pore channel structure of the porous carbon and/or coating the lithium oxalate on the surface of the porous carbon through recrystallization to obtain a lithium supplementing composite material;
dispersing PMMA into an organic solvent to obtain PMMA slurry;
adding the lithium supplementing composite material into PMMA slurry, uniformly dispersing to obtain composite slurry, and rolling the composite slurry on one side surface of the diaphragm base layer to form a porous functional coating by the composite slurry.
5. The method for preparing a porous functional coating membrane according to claim 4, wherein the process for preparing the lithium-supplementing composite material by recrystallization comprises the following steps: heating water to 80-100 ℃, adding lithium oxalate to prepare saturated solution, adding porous carbon to disperse uniformly, cooling to 0-50 ℃, and filtering to obtain a lithium supplementing composite material;
preferably, the mass ratio of the water to the lithium oxalate to the porous carbon is 80-100:2-8:5-15.
6. The method for preparing a porous functional coating membrane according to claim 4, wherein the organic solvent used in preparing PMMA slurry is N-methylpyrrolidone;
or, when PMMA slurry is prepared, stirring by adopting a planetary stirrer; preferably, the stirring time is 60-90 min, the stirring speed revolution is 30-40 r/min, and the rotation is 800-1500 r/min;
or, when preparing PMMA slurry, the particle size of PMMA is 0.2-10 μm.
7. The method for preparing a porous functional coating membrane according to claim 4, wherein the lithium supplementing composite material is added into PMMA slurry and stirred by a planetary stirrer to be uniformly dispersed; preferably, the stirring time is 60-90 min, the stirring speed revolution is 30-40 r/min, and the rotation is 800-1500 r/min.
8. The method for preparing a porous functional coated separator according to claim 4, wherein the composite slurry is coated on one side of the separator base layer by gravure roll; the thickness of the coating is preferably 1-10 mu m; the coating speed is preferably 20-100 m/min; the speed ratio of the gravure roll is preferably 50-120%; the temperature of the oven is preferably 50-100 ℃; the unreeling tension is preferably 10-30N; the tension of the oven is preferably 10-35N; the winding tension is preferably 10 to 30N.
9. The lithium ion battery is characterized by being a hot-pressing composite battery core and comprising a positive plate, the porous functional coating diaphragm, electrolyte and a negative plate, wherein the positive plate, the porous functional coating diaphragm and the negative plate are formed by hot-pressing composite.
10. The lithium ion battery of claim 9, wherein the positive electrode material of the positive electrode sheet is lithium nickel cobalt manganese oxide;
or the negative electrode material of the negative electrode plate is graphite;
or the preparation process of the lithium ion battery comprises a hot-pressing process, wherein the hot-pressing temperature is 50-100 ℃, the hot-pressing time is 20-180 s, and the hot-pressing pressure is 0.1-0.6 MPa;
or the preparation process of the lithium ion battery comprises a formation process, wherein in the formation process, the charging current is 0.01-0.33 ℃, the cut-off voltage is 3.7-4.5V, the formation pressure is 0.1-0.8 MPa, and the formation temperature is 30-70 ℃.
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