High-low temperature bonding slurry, preparation method for lithium battery separator, and lithium battery

Abstract

A high-low temperature bonding slurry, a preparation method for a lithium battery separator, and a lithium battery, relating to the technical field of lithium batteries. The high-low temperature bonding slurry comprises the following components in parts by mass: 10-15 parts of a bonding material, 5-15 parts of a thickener, 2-15 parts of a binder, 0-0.5 parts of a dispersant, and 50-80 parts of water, wherein the bonding material is formed by coating a high-temperature bonding material with a low-temperature bonding material, and raw materials of the bonding material include the low-temperature bonding material and the high-temperature bonding material having a mass ratio ranging from 1:9 to 9:1. The described technical solution solves the problems in the related art that the adhesive strength between a water-based bonding material for a lithium battery and an electrode sheet is poor, and high-temperature softening is required to achieve good adhesion.

Description

A high-low temperature adhesive paste, a preparation method of a lithium battery separator and a lithium battery TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a high-low temperature adhesive paste, a preparation method of a lithium battery separator and a lithium battery. BACKGROUND

[0002] With the increasing demand for battery energy density, the amount of emerging materials such as high-nickel and silicon-carbon is increasing. These materials provide high capacity, but during charging and discharging, they have significant cycle shrinkage, which causes the electrode-separator-electrode system to twist and deform in the process of creeping, and even form gaps, which may cause the battery to swell, and in severe cases, may cause lithium precipitation on the negative electrode surface, resulting in internal short-circuit, self-discharge, spontaneous combustion, explosion and other safety hazards.

[0003] To solve the above problems, the commonly used method is to modify the surface of the separator to make it adhesive, so that an adhesive layer is formed between the electrode-separator-electrode system to solidify the interface. Commonly used adhesive materials include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP copolymer), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), etc. The process routes used include oil-based (polymer is dissolved in organic solvent, the solution is coated, and the surface of the polyolefin-based film is modified) and water-based (polymer is dispersed in water to form a suspension of the polymer, the suspension is coated, and the surface of the polyolefin-based film is modified).

[0004] The adhesive effect of the oil-based route separator and electrode is good, but the cost of the solvent and the cost of environmental control are high. The most commonly used water-based route is PVDF-HFP copolymer, and the dispersion system used is water, which produces no waste gas and waste liquid, has low cost and good environmental friendliness, but the adhesion to the electrode is weak and needs to be softened at high temperature to have good adhesion. SUMMARY

[0005] The present application provides a high-low temperature adhesive paste, a preparation method of a lithium battery separator and a lithium battery, which solves the problem of poor adhesion of water-based adhesive materials for lithium batteries to electrode sheets and the need for softening at high temperature to have good adhesion.

[0006] The technical scheme of the present application is as follows: a high-low temperature adhesive paste, comprising the following components by mass: 10-15 parts of adhesive material, 5-15 parts of thickening agent, 2-15 parts of binder, 0-0.5 parts of dispersing agent, and 50-80 parts of water, wherein the adhesive material is a low-temperature adhesive material coated with a high-temperature adhesive material, and the raw materials of the adhesive material include a low-temperature adhesive material and a high-temperature adhesive material in a mass ratio of 1:9-9:1.

[0007] As a further technical solution, the thickening agent comprises one or both of sodium carboxymethyl cellulose and polyacrylamide.

[0008] As a further technical solution, the binder comprises one or both of polyvinyl alcohol and acrylic acid.

[0009] As a further technical solution, the dispersant comprises one or more of a quaternary ammonium salt dispersant, an acrylate type high molecular dispersant, and a polyester type high molecular dispersant.

[0010] As a further technical solution, the mass of the low-temperature adhesive material is less than or equal to the mass of the high-temperature adhesive material.

[0011] The present application limits the mass of the low-temperature adhesive material to be less than or equal to the mass of the high-temperature adhesive material, further improving the high and low temperature adhesion of the adhesive slurry to the pole piece.

[0012] As a further technical solution, the mass ratio of the low-temperature adhesive material to the high-temperature adhesive material is 1:2 to 4.

[0013] In the present application, the mass ratio of the low-temperature adhesive material to the high-temperature adhesive material is limited to 1:2 to 4, further improving the high and low temperature adhesion of the adhesive slurry to the pole piece.

[0014] As a further technical solution, the low-temperature adhesive material is a polyacrylate polymer, and the high-temperature adhesive material is a fluorine-containing polymer.

[0015] As a further technical solution, the polyacrylate polymer is polymethyl methacrylate, and the fluorine-containing polymer can be any polymer containing fluorine atoms, such as one or more of polytetrafluoroethylene, polyvinylidene fluoride, and polyvinylidene fluoride-hexafluoropropylene copolymer, preferably polyvinylidene fluoride-hexafluoropropylene copolymer.

[0016] As a further technical solution, the preparation method of the adhesive material comprises the following steps: uniformly mixing the low-temperature adhesive material and the high-temperature adhesive material, melt extruding, and granulating to obtain the adhesive material.

[0017] As a further technical solution, the adhesive material is an ethylene-vinyl alcohol copolymer modified adhesive material.

[0018] In the present application, the adhesive material is modified by ethylene-vinyl alcohol copolymer, further improving the high and low temperature adhesion of the adhesive slurry to the pole piece.

[0019] As a further technical solution, the raw material of the ethylene-vinyl alcohol copolymer modified adhesive material comprises ethylene-vinyl alcohol copolymer and adhesive material in a mass ratio of 1 to 5:15.

[0020] As a further technical scheme, the raw material of the ethylene-vinyl alcohol copolymer modified adhesive material comprises ethylene-vinyl alcohol copolymer and adhesive material in a mass ratio of 1:5.

[0021] The application limits the raw material of the ethylene-vinyl alcohol copolymer modified adhesive material to comprise ethylene-vinyl alcohol copolymer and adhesive material in a mass ratio of 1:5, and further improves the high and low temperature adhesion of the adhesive slurry to the pole piece.

[0022] As a further technical scheme, the preparation method of the ethylene-vinyl alcohol copolymer modified adhesive material comprises the following steps: dissolving ethylene-vinyl alcohol copolymer in a solvent, adding adhesive material and mixing uniformly, drying, and obtaining the ethylene-vinyl alcohol copolymer modified adhesive material.

[0023] As a further technical scheme, the solvent can be any solvent that can dissolve ethylene-vinyl alcohol copolymer, and preferably a mixed solvent of water and n-propanol.

[0024] The application further provides a preparation method of a lithium battery separator, comprising the following steps: coating the high and low temperature adhesive slurry on the surface of a polyolefin-based film, and drying to obtain a lithium battery separator.

[0025] As a further technical scheme, the coating comprises one of full coating, point coating, intermittent coating, and stripe coating.

[0026] As a further technical scheme, the full coating adopts gravure coating; and as a further technical scheme, the point coating adopts spraying to form random points or adopts point coating equipment to form matrix uniform distribution points.

[0027] The application further provides a lithium battery, which comprises the lithium battery separator.

[0028] The application has the following working principle and beneficial effects: the application provides a high and low temperature adhesive slurry with good adhesion to a pole piece, which comprises adhesive material, thickening agent, binder, dispersant, and water, wherein the adhesive material is a low temperature adhesive material coated with a high temperature adhesive material, the adhesive material not only has room temperature adhesion, but also has strong high temperature adhesion, and the adhesion temperature range covers most of the scenarios from the preparation of a lithium battery to subsequent use, so that the separator and the pole piece have sufficient adhesion, and the performance stability of the battery during the whole life cycle can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0029] The application will be further described in detail below in combination with the drawings and specific embodiments.

[0030] Figure 1 is a SEM image of a point-coated adhesive-coated lithium battery separator prepared from the high-low temperature adhesive slurry of Example 1, magnified 15.00K times; Figure 2 is a SEM image of a point-coated adhesive-coated lithium battery separator prepared from the high-low temperature adhesive slurry of Example 1, magnified 100 times; Figure 3 is a SEM image of a point-coated adhesive-coated lithium battery separator prepared from the high-low temperature adhesive slurry of Comparative Example 1, magnified 15.00K times. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor also fall within the scope of protection of the present application.

[0032] The parameters of the raw materials in the following examples and comparative examples are as follows: the poly(methyl methacrylate) is PMMACM-211; the poly(vinylidene fluoride-co-hexafluoropropylene) has a brand of sigma, an average Mw of 400000, and an average Mn of 130000; the ethylene-vinyl alcohol copolymer is purchased from Shanghai Zhenjun Biological Technology Co., Ltd., and has a product number of 55207345; the polyvinyl alcohol is PVA 2488; and the polyacrylamide is a cationic polyacrylamide with a weight average molecular weight of 18 million.

[0033] Example 1 S1, 13.5 parts of poly(methyl methacrylate) and 1.5 parts of poly(vinylidene fluoride-co-hexafluoropropylene) were uniformly mixed, melt-extruded, and granulated to obtain an adhesive material; S2, 69.9 parts of water and 0.1 part of octadecyl dimethyl benzyl ammonium chloride quaternary ammonium salt were mixed and stirred for 10 min, then 15 parts of the adhesive material was added and stirred for 90 min, 5 parts of sodium carboxymethyl cellulose was added and stirred for 10 min, and finally 10 parts of polyvinyl alcohol was added and stirred for 30 min to obtain a high-low temperature adhesive slurry (SEM image as shown in Figure 1).

[0034] Example 2 S1, 13.5 parts of poly(methyl methacrylate) and 1.5 parts of poly(vinylidene fluoride-co-hexafluoropropylene) were uniformly mixed, melt-extruded, and granulated to obtain an adhesive material; S2, 50 parts of water and 0.5 parts of EFKA-4560 high molecular weight polyacrylate dispersant were mixed and stirred for 5 min, then 10 parts of the adhesive material was added and stirred for 10 min, 10 parts of polyacrylamide was added and stirred for 5 min, and finally 2 parts of acrylic acid was added and stirred for 5 min to obtain a high-low temperature adhesive slurry.

[0035] Example 3 S1, poly (methyl methacrylate) 13.5 parts and poly (vinylidene fluoride-hexafluoropropylene) copolymer 1.5 parts were mixed uniformly, melt extrusion, granulation, to get the bonding material; S2, water 80 parts and bonding material 13 parts were stirred for 120 min, polyacrylamide 15 parts was added and stirred for 20 min, and finally acrylic acid 15 parts was added and stirred for 30 min to obtain a high and low temperature bonding slurry.

[0036] Example 4 The difference from example 1 is only that: S1, poly (methyl methacrylate) 7.5 parts and poly (vinylidene fluoride-hexafluoropropylene) copolymer 7.5 parts were mixed uniformly, melt extrusion, granulation, to get the bonding material.

[0037] Example 5 The difference from example 1 is only that: S1, poly (methyl methacrylate) 5 parts and poly (vinylidene fluoride-hexafluoropropylene) copolymer 10 parts were mixed uniformly, melt extrusion, granulation, to get the bonding material.

[0038] Example 6 The difference from example 1 is only that: S1, poly (methyl methacrylate) 3 parts and poly (vinylidene fluoride-hexafluoropropylene) copolymer 12 parts were mixed uniformly, melt extrusion, granulation, to get the bonding material.

[0039] Example 7 The difference from example 1 is only that: S1, poly (methyl methacrylate) 1.5 parts and poly (vinylidene fluoride-hexafluoropropylene) copolymer 13.5 parts were mixed uniformly, melt extrusion, granulation, to get the bonding material.

[0040] Example 8 S1, poly (methyl methacrylate) 3 parts and poly (vinylidene fluoride-hexafluoropropylene) copolymer 12 parts were mixed uniformly, melt extrusion, granulation, to get the bonding material; S2, ethylene-vinyl alcohol copolymer 1 g was dissolved in a mixed solvent of water and n-propanol with a volume ratio of 1:1 100 mL, and then 15 g of the bonding material was added and stirred at 500 rpm for 20 min, and then filtered and dried to obtain ethylene-vinyl alcohol copolymer modified bonding material; S3, water 69.9 parts and octadecyl dimethyl benzyl ammonium chloride quaternary ammonium salt 0.1 parts were mixed and stirred for 10 min, then 15 parts of ethylene-vinyl alcohol copolymer modified bonding material was added and stirred for 90 min, then 5 parts of sodium carboxymethyl cellulose was added and stirred for 10 min, and finally 10 parts of polyvinyl alcohol was added and stirred for 30 min to obtain a high and low temperature bonding slurry.

[0041] Example 9 The difference from example 8 is only that: ethylene-vinyl alcohol copolymer 3 g.

[0042] Example 10 The difference from example 8 is only that: ethylene-vinyl alcohol copolymer 5 g.

[0043] Comparative Example 1 Water 69.9 parts and octadecyl dimethyl benzyl ammonium chloride quaternary ammonium salt 0.1 part were mixed and stirred for 10 min, then polymethyl methacrylate 13.5 parts, polyvinylidene fluoride-hexafluoropropylene copolymer 1.5 parts were added and stirred for 90 min, sodium carboxymethyl cellulose 5 parts was added and stirred for 10 min, finally polyvinyl alcohol 10 parts was added and stirred for 30 min to obtain a high-low temperature bonding slurry (SEM image as shown in Figure 2).

[0044] Preparation of lithium battery separator: (1) The high-low temperature bonding slurry obtained in Example 1 was point-coated on the surface of a polyolefin-based film at a speed of 130 m / min, the thickness of the polyolefin-based film was 5 μm, the coating surface moisture was dried by passing through an 80°C oven, to obtain a point-coated bonding coating lithium battery separator, the coating thickness was 3.5 μm, the coverage rate was 15%, and the SEM image is shown in Figures 1-2.

[0045] (2) The high-low temperature bonding slurry obtained in Example 1 was roll-coated on the surface of a polyolefin-based film at a speed of 100 m / min, the thickness of the polyolefin-based film was 5 μm, the coating surface moisture was dried by passing through an 80°C oven, to obtain a full roll-coated bonding coating lithium battery separator, the coating thickness was 1.5 μm.

[0046] (3) The high-low temperature bonding slurry obtained in Example 1 was sprayed on the surface of a polyolefin-based film at a speed of 130 m / min, the thickness of the polyolefin-based film was 5 μm, the coating surface moisture was dried by passing through an 80°C oven, to obtain a sprayed bonding coating lithium battery separator, the coating thickness was 3.5 μm, the coverage rate was 28%.

[0047] (4) The high-low temperature bonding slurry obtained in Comparative Example 1 was point-coated on the surface of a polyolefin-based film at a speed of 130 m / min, the thickness of the polyolefin-based film was 5 μm, the coating surface moisture was dried by passing through an 80°C oven, to obtain a point-coated bonding coating lithium battery separator, the coating thickness was 3.5 μm, the coverage rate was 15%, and the SEM image is shown in Figure 3.

[0048] Performance test: The high-low temperature bonding slurries obtained in Examples 1-10 and Comparative Example 1 were tested for bonding strength, the test method was as follows: referring to the method of preparing the lithium battery separator (1), the high-low temperature bonding slurries obtained in Examples 1-10 and Comparative Example 1 were respectively prepared into point-coated bonding coating lithium battery separators and point-coated bonding coating pole pieces, then 100 mm x 30 mm samples were cut, the separator coating side and the pole piece coating side were corresponded and placed under a hot press, the adhesion between the separator coating and the pole piece coating was measured by using an electronic tensile testing machine after hot pressing at 80°C and 0.3 MPa for 1 s, and the results are shown in Table 1.

[0049] Table 1 Adhesion between separator coating and pole piece coating

[0050] As can be seen from Table 1, the adhesive paste provided by the present application has a 30℃ adhesive force of 1.2 N / m or more, a 50℃ adhesive force of 2.1 N / m or more, a 70℃ adhesive force of 2.7 N / m or more, and a 90℃ adhesive force of 3.3 N / m or more, and has good high and low temperature adhesive force with the pole piece.

[0051] Compared with Comparative Example 1, the low-temperature adhesive material coats the high-temperature adhesive material in Example 1, and the adhesive force of the adhesive paste obtained at 30℃, 50℃, 70℃ and 90℃ is better than that of Comparative Example 1, which shows that the low-temperature adhesive material coating the high-temperature adhesive material as the adhesive material can improve the high and low temperature adhesive force of the adhesive paste with the pole piece.

[0052] The adhesive force of the adhesive paste obtained at 30℃, 50℃, 70℃ and 90℃ in Examples 4-7 is better than that of Example 1, which shows that the mass of the low-temperature adhesive material is less than that of the high-temperature adhesive material, and further improves the high and low temperature adhesive force of the adhesive paste with the pole piece.

[0053] The adhesive force of the adhesive paste obtained at 30℃, 50℃, 70℃ and 90℃ in Examples 5-6 is better than that of Examples 4 and 7, which shows that the mass ratio of the low-temperature adhesive material to the high-temperature adhesive material is 1:2-4, and further improves the high and low temperature adhesive force of the adhesive paste with the pole piece.

[0054] The adhesive force of the adhesive paste obtained at 30℃, 50℃, 70℃ and 90℃ in Examples 8-10 is better than that of Example 6, which shows that after the adhesive material is modified by ethylene-vinyl alcohol copolymer, the high and low temperature adhesive force of the adhesive paste with the pole piece is further improved.

[0055] The adhesive force of the adhesive paste obtained at 30℃, 50℃, 70℃ and 90℃ in Example 9 is better than that of Examples 8 and 10, which shows that the mass ratio of the ethylene-vinyl alcohol copolymer to the adhesive material is 1:5, and the high and low temperature adhesive force of the adhesive paste with the pole piece is further improved.

[0056] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high and low temperature bonding paste, characterized by, The adhesive material is a low-temperature adhesive material coated with a high-temperature adhesive material, and the raw materials of the adhesive material include a low-temperature adhesive material and a high-temperature adhesive material in a mass ratio of 1:9-9:

1.

2. The high and low temperature adhesive paste according to claim 1, characterized in that, The mass of the low-temperature adhesive material is ≤ the mass of the high-temperature adhesive material.

3. The high and low temperature adhesive paste according to claim 2, characterized in that, The mass ratio of the low-temperature adhesive material to the high-temperature adhesive material is 1:2-4.

4. The high and low temperature adhesive paste of claim 3, wherein, The low-temperature adhesive material is a polyacrylate polymer, and the high-temperature adhesive material is a fluorine-containing polymer.

5. The high and low temperature adhesive paste of claim 1, wherein, The preparation method of the adhesive material includes the following steps: uniformly mixing the low-temperature adhesive material and the high-temperature adhesive material, melt-extruding, granulating, and obtaining the adhesive material.

6. The high and low temperature adhesive paste of claim 5, wherein, The adhesive material is an ethylene-vinyl alcohol copolymer modified adhesive material.

7. The high and low temperature adhesive paste of claim 6, wherein, The raw materials of the ethylene-vinyl alcohol copolymer modified adhesive material include ethylene-vinyl alcohol copolymer and adhesive material in a mass ratio of 1-5:

15.

8. The high and low temperature adhesive paste of claim 7, wherein, The preparation method of the ethylene-vinyl alcohol copolymer modified adhesive material includes the following steps: dissolving ethylene-vinyl alcohol copolymer in a solvent, adding adhesive material, uniformly mixing, drying, and obtaining the ethylene-vinyl alcohol copolymer modified adhesive material.

9. A method of producing a lithium battery separator, characterized by, The method includes the following steps: coating the high-low-temperature adhesive slurry according to any one of claims 1-8 on the surface of a polyolefin-based film, drying, and obtaining a lithium battery separator.

10. A lithium battery, characterized by, The raw materials include the lithium battery separator according to claim 9.

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