Preparation method of low-foam high-adhesion lithium battery slurry and diaphragm

Abstract

The invention relates to the technical field of lithium batteries, and provides a preparation method of low-foam high-adhesion lithium battery slurry and a diaphragm. The low-foam high-adhesion lithium battery slurry is prepared from the following components in percentage by weight: 10%-15% of polyvinylidene fluoride, 0.5%-1.0% of a dispersing agent, 9%-15% of a thickening agent, 10%-20% of a binding agent, 0.2%-0.5% of a foam inhibitor and the balance of water, the foam inhibitor comprises a polyether-polysiloxane copolymer and nano calcium carbonate in a weight ratio of (1-9): 1. According to the technical scheme, the problem of poor binding power of the diaphragm prepared from the lithium battery slurry in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and specifically, to a preparation method of a low-foaming and highly adhesive lithium battery slurry and a separator Background Art

[0002] In the structure of a lithium battery, the separator is one of the key inner components. The performance of the separator determines the interface structure, internal resistance, etc. of the battery, directly affecting the characteristics such as the capacity, cycle, and safety performance of the battery. A separator with excellent performance plays an important role in improving the comprehensive performance of the battery

[0003] The wet-process separator has the advantages of being relatively thin in thickness, having uniform micropores, a high porosity, a relatively low air permeability, and better wettability than the dry-process separator, etc., which can effectively ensure the energy density and cycle performance of the battery and is more suitable for high-energy-density batteries. Although the wet-process separator has many advantages, its melting temperature is low and its heat resistance is poor. At high temperatures (less than 120 °C), the shrinkage rate is as high as 10%, which may cause the exposure of the electrode sheet. To improve the performance of the wet-process separator, the current mainstream direction is to coat a functional material on the surface of the base film, thereby improving the thermal stability of the separator and its bonding strength, and thus extending the battery cycle life

[0004] During the preparation of the slurry usually used for the coating layer on the surface of the base film, bubbles will be generated due to high-speed dispersion. Although in the pulp-making process, a vacuum environment is adopted or traditional defoamers are added to achieve the defoaming purpose, during the use of the slurry, in order to prevent the slurry from settling, the stirring paddle often needs to be turned on to make the slurry in a uniform state. Due to the existence of stirring, new bubbles are generated in the slurry, and these bubbles cannot be quickly eliminated, which affects the internal stability and uniformity of the slurry, forms defects inside the separator, and also causes the separator to be missed coated, thus affecting the bonding force between the separator and the electrode sheet

[0005] Therefore, researching and developing a low-foaming and highly adhesive lithium battery slurry with a uniform and dense internal structure, so as to have good bonding force, plays an important role in improving the life and safety of lithium batteries Summary of the Invention

[0006] The present invention provides a preparation method of a low-foaming and highly adhesive lithium battery slurry and a separator, which solves the problem of poor bonding force of the separator obtained from the lithium battery slurry in the related art

[0007] The technical solution of the present invention is as follows The present invention provides a low-foaming and highly adhesive lithium battery slurry, which is composed of the following components in weight percentage 10% - 15% of polyvinylidene fluoride, 0.5% - 1.0% of dispersant, 9% - 15% of thickener, 10% - 20% of binder, 0.2% - 0.5% of antifoaming agent, and the balance is water The defoamer comprises a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 1-9:1.

[0008] As a further technical solution, the weight ratio of the polyether-polysiloxane copolymer to the nano calcium carbonate is 3-4:1.

[0009] When the weight ratio of the polyether-polysiloxane copolymer to the nano calcium carbonate > 4:1, such as 8:1, the adhesion force between the separator and the positive electrode plate can reach 11.9 N / m, and the adhesion force between the separator and the negative electrode plate can reach 10.2 N / m; when the weight ratio of the polyether-polysiloxane copolymer to the nano calcium carbonate < 3:1, such as 1.5:1, the adhesion force between the separator and the positive electrode plate can reach 11.3 N / m, and the adhesion force between the separator and the negative electrode plate can reach 9.4 N / m. When the weight ratio of the polyether-polysiloxane copolymer to the nano calcium carbonate is 3-4:1, the adhesion force between the separator and the electrode plate can reach the optimum, the adhesion force between the separator and the positive electrode plate can reach 13.0-13.4 N / m, and the adhesion force between the separator and the negative electrode plate can reach 11.3-11.6 N / m.

[0010] As a further technical solution, the polyether-polysiloxane copolymer comprises the following components in parts by weight: 1-2 parts of siloxane copolymer, 1-1.5 parts of organosilicon polyether, 0.05-0.1 part of thickener, 0.5-1.2 parts of emulsifier, 8-12 parts of organic solvent.

[0011] As a further technical solution, the preparation method of the polyether-polysiloxane copolymer comprises the following steps: A1. Mix the siloxane copolymer, organosilicon polyether and organic solvent evenly, adjust the pH value to 8-10, and react to obtain a mixture; A2. Add the remaining components of the polyether-polysiloxane copolymer to the mixture, and mix evenly to obtain the polyether-polysiloxane copolymer.

[0012] By mixing the siloxane copolymer, organosilicon polyether and organic solvent evenly and reacting after adjusting the pH value, a polyether-polysiloxane copolymer with good defoaming and antifoaming effects can be obtained under the action of the remaining components. Then, combined with nano calcium carbonate, the defoamer can have good defoaming and antifoaming effects, thereby improving the adhesion force between the separator and the electrode plate.

[0013] As a further technical solution, in step A1, during the reaction, the temperature is 100-120 °C and the reaction time is 4-8 h.

[0014] As a further technical solution, in step A2, when mixing evenly, the stirring speed is 15-30 r / min and the stirring time is 30-60 min.

[0015] As a further technical solution, when adjusting the pH value to 8-11, potassium hydroxide or sodium hydroxide is used.

[0016] As a further technical solution, the nano calcium carbonate is 3,4-dimethoxybenzoic acid composite nano calcium carbonate, and the raw materials of the 3,4-dimethoxybenzoic acid composite nano calcium carbonate include nano calcium carbonate and 3,4-dimethoxybenzoic acid.

[0017] In the present invention, the compounding effect of 3,4-dimethoxybenzoic acid on nano calcium carbonate can reduce the agglomeration phenomenon of nano calcium carbonate, improve the interfacial bonding effect between nano calcium carbonate and other components in the system, play the role of foam inhibition and defoaming, and at the same time, make the prepared separator more uniform and stable, thereby improving the puncture resistance of the separator.

[0018] As a further technical solution, the weight ratio of the nano calcium carbonate to 3,4-dimethoxybenzoic acid is 30:3-5.

[0019] When the weight ratio of nano calcium carbonate to 3,4-dimethoxybenzoic acid > 10:1, such as 15:1, the puncture strength of the separator can reach 16.8 N; when the weight ratio of nano calcium carbonate to 3,4-dimethoxybenzoic acid < 6:1, such as 5:1, the puncture strength of the separator can reach 17.2 N; and when the weight ratio of nano calcium carbonate to 3,4-dimethoxybenzoic acid is 30:3-5, the compounding effect of 3,4-dimethoxybenzoic acid on nano calcium carbonate can reach the optimal, and the puncture strength of the separator can reach 17.9-18.1 N.

[0020] As a further technical solution, the preparation method of the 3,4-dimethoxybenzoic acid composite nano calcium carbonate includes the following steps: dissolving the 3,4-dimethoxybenzoic acid in ethanol, adding the nano calcium carbonate, dispersing evenly, concentrating, and drying to obtain the 3,4-dimethoxybenzoic acid composite nano calcium carbonate.

[0021] As a further technical solution, the dispersant is one or more of ammonium polyacrylate, sodium dodecylbenzenesulfonate, and sodium polyacrylate, and preferably ammonium polyacrylate.

[0022] In the present invention, the addition of the dispersant can effectively reduce the surface energy between the components in the lithium battery slurry, make polyvinylidene fluoride and various additives evenly dispersed in the slurry, and improve the dispersion stability of the lithium battery slurry.

[0023] As a further technical solution, the thickener is one or two of sodium carboxymethyl cellulose and sodium carboxymethyl cellulose, and preferably sodium carboxymethyl cellulose.

[0024] As a further technical solution, the binder is one or both of bisphenol A epoxy resin and bisphenol F epoxy resin, and preferably bisphenol A epoxy resin.

[0025] In the present invention, the thickener can adjust the viscosity of the lithium battery slurry to make the viscosity and rheological properties of the lithium battery slurry in a suitable state; the binder can provide good binding properties for the lithium battery slurry, so that the prepared separator and the electrode have a certain adhesive force.

[0026] As a further technical solution, the particle size of the nano calcium carbonate is 50-200 nm.

[0027] As a further technical solution, the siloxane copolymer is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0028] As a further technical solution, the organosilicon polyether is formed by condensation of a siloxane chain segment and a polyether chain segment. The siloxane chain segment is dimethylsilanediol, and the polyether chain segment is polyethylene oxide.

[0029] As a further technical solution, the molecular weight of the polyethylene oxide is 600-800.

[0030] As a further technical solution, the preparation method of the organosilicon polyether includes the following steps: adding toluene into a synthesis reaction kettle, adding dimethylsilanediol, concentrated sulfuric acid and polyethylene oxide, reacting at 130-150 °C for 4-6 h, separating and purifying to obtain the organosilicon polyether.

[0031] As a further technical solution, the molar ratio of dimethylsilanediol to polyethylene oxide is 2-3:1, and the addition amount of concentrated sulfuric acid is 0.1%-0.3% of the total mass of dimethylsilanediol and polyethylene oxide; the mass fraction of the concentrated sulfuric acid is 98%.

[0032] As a further technical solution, the mass-volume ratio of dimethylsilanediol to toluene is 1 g:20 mL.

[0033] As a further technical solution, among the components of the polyether-polysiloxane copolymer, the thickener is one or more of hydroxyethyl cellulose, alginate derivatives, polyethylene glycol 6000 distearate, and preferably polyethylene glycol 6000 distearate.

[0034] As a further technical solution, the emulsifier is one or more of polyoxyethylene ether, sorbitan stearate, and methyl glucoside sesquistearate, and preferably sorbitan stearate.

[0035] The organic solvent is one of dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide, preferably dimethyl sulfoxide.

[0036] The present invention provides a method for preparing a low-foaming high-adhesion lithium battery slurry, comprising the following steps: mixing the polyvinylidene fluoride, dispersant, defoaming agent, and water uniformly, and then adding the remaining components of the low-foaming high-adhesion lithium battery slurry and dispersing uniformly to obtain the low-foaming high-adhesion lithium battery slurry.

[0037] As a further technical solution, when mixing uniformly, the rotation speed of the planetary stirring device is 1800 - 2400 r / min, the revolution speed is 30 - 60 r / min, and the stirring time is 60 - 80 min; when dispersing uniformly, the rotation speed is 800 - 1100 r / min, the revolution speed is 20 - 40 r / min, and the stirring time is 20 - 40 min.

[0038] The present invention also provides a separator, which is obtained by coating a base film with the low-foaming high-adhesion lithium battery slurry described above or the low-foaming high-adhesion lithium battery slurry prepared by the preparation method described above; The base film is one of a polypropylene film and a polyethylene film; When coating, the coating speed is 30 - 50 m / min; When coating, the thickness of the formed coating is 2 - 5 μm.

[0039] The working principle and beneficial effects of the present invention are as follows: 1. In the present invention, using polyvinylidene fluoride and a binder as the main materials, with the assistance of a dispersant, thickener, and defoaming agent, a lithium battery slurry with a uniform and stable internal structure is obtained. Among them, polyvinylidene fluoride and the binder, as the main materials, have good chemical stability and bonding properties. While maintaining the integrity of the separator formed by the slurry, they can enhance the bonding force between the separator and the electrode, thereby reducing the phenomenon of shedding and pulverization of the electrode during charge and discharge, and extending the service life of the battery.

[0040] 2. The defoaming agent includes a polyether-polysiloxane copolymer and nano-calcium carbonate. By using the polyether-polysiloxane copolymer and nano-calcium carbonate together, weak points can be formed in the bubble liquid film in the system relatively quickly, resulting in rapid bubble rupture, enhancing the defoaming and antifoaming effects. Even if new bubbles are formed during stirring, their stability can be quickly destroyed, making the lithium battery slurry more uniform and stable, reducing the problem of uneven contact between the separator and the electrode due to the presence of bubbles, and further improving the bonding force between the separator and the electrode. By adjusting the content ratio of the defoaming agent, when its weight percentage is 0.2% - 0.5%, the defoaming and antifoaming effects can reach the optimal, thereby improving the bonding force between the separator and the electrode. Brief Description of the Drawings

[0041] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0042] Figure 1 The separator obtained by preparing a low-foaming and highly adhesive lithium-ion battery slurry for Example 1; Figure 2 The separator obtained by preparing a low-foaming and highly adhesive lithium-ion battery slurry for Comparative Example 1. Specific Embodiments

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of the present invention.

[0044] In the following examples and comparative examples: The model of polyvinylidene fluoride is FR905; The viscosity of sodium carboxymethyl cellulose is 1000 mPa·s; The model of bisphenol A epoxy resin is E-20; The viscosity of polyethylene glycol 6000 distearate is 2000 mPa·s; The particle size of nano calcium carbonate is 100 nm; The preparation method of organosilicon polyether is as follows: Toluene is added to a synthesis reaction kettle, dimethylsilanediol, concentrated sulfuric acid with a mass fraction of 98%, and polyethylene oxide with a molecular weight of 660 are added. After reacting at 140 °C for 5 h, separation and purification are carried out to obtain organosilicon polyether. Among them, the molar ratio of dimethylsilanediol to polyethylene oxide is 1.5:1, and the concentrated sulfuric acid with a mass fraction of 98% is 0.2% of the total mass of dimethylsilanediol and polyethylene oxide.

[0045] Example 1 The polyether-polysiloxane copolymer comprises the following components in parts by weight: 1 part of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 1 part of organosilicon polyether, 0.05 part of polyethylene glycol 6000 distearate, 0.5 part of sorbitan stearate, 8 parts of dimethyl sulfoxide; The preparation method of the polyether-polysiloxane copolymer comprises the following steps: A1. Mix N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, organosilicon polyether, and dimethyl sulfoxide evenly, adjust the pH value to 8 with potassium hydroxide, and react at 100 °C for 8 h to obtain a mixture; A2. Add polyethylene glycol 6000 distearate and sorbitan stearate to the mixture, stir at 15 r / min for 60 min, and mix evenly to obtain a polyether-polysiloxane copolymer; The low-foaming and highly adhesive lithium battery slurry consists of the following components by weight percentage: Polyvinylidene fluoride 10%, ammonium polyacrylate 0.5%, sodium carboxymethyl cellulose 9%, bisphenol A epoxy resin 10%, defoaming agent 0.2%, and the balance is water; Among them, the defoaming agent includes a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 1:1; The preparation method of the low-foaming and highly adhesive lithium battery slurry includes the following steps: Stir polyvinylidene fluoride, ammonium polyacrylate, defoaming agent and water in a planetary stirring device with a rotation speed of 1800 r / min and a revolution speed of 30 r / min for 80 min. After mixing evenly, add sodium carboxymethyl cellulose and bisphenol A epoxy resin, and stir in a planetary stirring device with a rotation speed of 800 r / min and a revolution speed of 20 r / min for 40 min to disperse evenly to obtain the low-foaming and highly adhesive lithium battery slurry.

[0046] Example 2 The polyether-polysiloxane copolymer includes the following components by weight: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane 1.1 parts, organosilicon polyether 1.2 parts, polyethylene glycol 6000 distearate 0.08 parts, sorbitan stearate 0.9 parts, dimethyl sulfoxide 10 parts; The preparation method of the polyether-polysiloxane copolymer includes the following steps: A1. Mix N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, organosilicon polyether and dimethyl sulfoxide evenly, adjust the pH value to 9 with potassium hydroxide, and react at 105 °C for 6 h to obtain a mixture; A2. Add polyethylene glycol 6000 distearate and sorbitan stearate to the mixture, stir at 25 r / min for 50 min, and mix evenly to obtain a polyether-polysiloxane copolymer; The low-foaming and highly adhesive lithium battery slurry consists of the following components by weight percentage: Polyvinylidene fluoride 11%, ammonium polyacrylate 0.6%, sodium carboxymethyl cellulose 13%, bisphenol A epoxy resin 18%, defoaming agent 0.4%, and the balance is water; Among them, the defoaming agent includes a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 1.5:1; The preparation method of the low-foaming and high-adhesive lithium battery slurry comprises the following steps: Stir polyvinylidene fluoride, ammonium polyacrylate, defoaming agent and water in a planetary stirring device with a self-rotation speed of 2200 r / min and a revolution speed of 40 r / min for 70 min. After mixing evenly, add sodium carboxymethyl cellulose and bisphenol A epoxy resin, and stir for 30 min in a planetary stirring device with a self-rotation speed of 1000 r / min and a revolution speed of 30 r / min until evenly dispersed to obtain the low-foaming and high-adhesive lithium battery slurry.

[0047] Example 3 The polyether-polysiloxane copolymer comprises the following components in parts by weight: 2 parts of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 1.5 parts of organosilicon polyether, 0.1 part of polyethylene glycol 6000 distearate, 1.2 parts of sorbitan stearate, 12 parts of dimethyl sulfoxide; The preparation method of the polyether-polysiloxane copolymer comprises the following steps: A1. Mix N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, organosilicon polyether and dimethyl sulfoxide evenly, adjust the pH value to 10 with potassium hydroxide, and react at 120 °C for 4 h to obtain a mixture; A2. Add polyethylene glycol 6000 distearate and sorbitan stearate to the mixture, stir at 30 r / min for 30 min, and mix evenly to obtain the polyether-polysiloxane copolymer; The low-foaming and high-adhesive lithium battery slurry is composed of the following components in weight percentages: 15% of polyvinylidene fluoride, 1.0% of ammonium polyacrylate, 15% of sodium carboxymethyl cellulose, 20% of bisphenol A epoxy resin, 0.5% of defoaming agent, and the balance is water; Wherein the defoaming agent comprises a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 9:1; The preparation method of the low-foaming and high-adhesive lithium battery slurry comprises the following steps: Stir polyvinylidene fluoride, ammonium polyacrylate, defoaming agent and water in a planetary stirring device with a self-rotation speed of 2400 r / min and a revolution speed of 60 r / min for 60 min. After mixing evenly, add sodium carboxymethyl cellulose and bisphenol A epoxy resin, and stir for 20 min in a planetary stirring device with a self-rotation speed of 1100 r / min and a revolution speed of 40 r / min until evenly dispersed to obtain the low-foaming and high-adhesive lithium battery slurry.

[0048] Example 4 The difference between this example and Example 2 is only that in this example, the defoaming agent comprises a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 8:1.

[0049] Example 5 The difference between this example and Example 2 is only that in this example, the defoamer comprises a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 3:1.

[0050] Example 6 The difference between this example and Example 2 is only that in this example, the defoamer comprises a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 4:1.

[0051] Example 7 The difference between this example and Example 6 is only that in this example, the nano calcium carbonate is 3,4-dimethoxybenzoic acid composite nano calcium carbonate, and its preparation method comprises the following steps: dissolving 2 parts of 3,4-dimethoxybenzoic acid in 40 parts of ethanol, then adding 30 parts of nano calcium carbonate, dispersing evenly, concentrating, and drying to obtain 3,4-dimethoxybenzoic acid composite nano calcium carbonate.

[0052] Example 8 The difference between this example and Example 7 is only that in the preparation process of 3,4-dimethoxybenzoic acid composite nano calcium carbonate in this example, the added 3,4-dimethoxybenzoic acid is 6 parts.

[0053] Example 9 The difference between this example and Example 7 is only that in the preparation process of 3,4-dimethoxybenzoic acid composite nano calcium carbonate in this example, the added 3,4-dimethoxybenzoic acid is 3 parts.

[0054] Example 10 The difference between this example and Example 7 is only that in the preparation process of 3,4-dimethoxybenzoic acid composite nano calcium carbonate in this example, the added 3,4-dimethoxybenzoic acid is 5 parts.

[0055] Example 11 The difference between this example and Example 1 is only that in this example, the preparation method of the low-foaming and high-adhesion lithium battery slurry comprises the following steps: stirring polyvinylidene fluoride, ammonium polyacrylate and water in a planetary stirring device with a rotation speed of 1800 r / min and a revolution speed of 30 r / min for 80 min, mixing evenly, then adding a defoamer, sodium carboxymethyl cellulose, and bisphenol A type epoxy resin, and stirring and dispersing evenly in a planetary stirring device with a rotation speed of 800 r / min and a revolution speed of 20 r / min for 40 min to obtain the low-foaming and high-adhesion lithium battery slurry.

[0056] Comparative Example 1 The difference between this comparative example and Example 1 is only that in this comparative example, the polyether-polysiloxane copolymer in the defoamer is replaced with an equal amount of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0057] Comparative Example 2 The difference between this comparative example and Example 1 is only that in this comparative example, the nano calcium carbonate in the defoamer is replaced with an equal amount of nano silicon dioxide.

[0058] Comparative Example 3 The difference between this comparative example and Example 1 is only that in this comparative example, no defoamer is added.

[0059] Comparative Example 4 The difference between this comparative example and Example 1 is only that in this comparative example, the addition amount of the defoamer is 0.1%.

[0060] Comparative Example 5 The difference between this comparative example and Example 1 is only that in this comparative example, the addition amount of the defoamer is 0.6%.

[0061] Experimental Example 1 Bonding Strength Test Preparation of diaphragm: The low-foaming high-adhesion lithium-ion battery slurry prepared in Examples 1 to 6, Example 11 and Comparative Examples 1 to 5 was respectively coated on a polyethylene film at a coating speed of 40 m / min on one side, and dried at 60 °C for 2 min to obtain a diaphragm with a coating thickness of 3 μm; the thickness of the diaphragm was 11.35 μm; the diaphragm obtained from the low-foaming high-adhesion lithium-ion battery slurry prepared in Example 1 was as Figure 1 shown, and the diaphragm obtained from the low-foaming high-adhesion lithium-ion battery slurry prepared in Comparative Example 1 was as Figure 2 shown; The diaphragms obtained above were respectively stacked with the positive electrode or negative electrode, and thermally pressed at 90 °C and 3 MPa for 1 min to bond the diaphragm with the positive electrode or negative electrode together. The bonding force between the diaphragm and the positive electrode or negative electrode was tested by a peeling tester. During the test, the width of the specimen was 25 mm and the peeling speed was 300 mm / min. The test results are shown in Table 1 below: Table 1 Test Results of the Bonding Force between the Electrodes of Examples 1 to 6, Example 11 and Comparative Examples 1 to 5

[0062] As can be seen from Table 1, after the diaphragm is prepared from the low-foaming high-adhesion lithium-ion battery slurry prepared by this solution, the diaphragm and the electrode have good bonding force. The bonding force between the diaphragm and the positive electrode can reach at least 9.4 N / m, and the bonding force between the diaphragm and the negative electrode can reach at least 7.6 N / m; among them, compared with Comparative Examples 1 to 5, the bonding force between the diaphragm and the electrode prepared in Example 1 is improved, indicating that by using a polyether-polysiloxane copolymer and nano calcium carbonate together and reasonably adjusting the content ratio of the defoamer, when its weight percentage is 0.2% to 0.5%, the bonding force between the diaphragm and the electrode can be improved. In addition, Figure 1 andFigure 2 It was found by comparison that when using polyether-polysiloxane copolymer and nano-calcium carbonate as compound defoamers, compared with conventional defoamers, the phenomenon of missing coating on the battery separator prepared was improved, thereby enhancing the adhesion between the separator and the electrode sheet.

[0063] Experimental Example 2 Puncture Resistance Performance Test After obtaining the separator from the low-foaming and high-adhesion lithium-ion battery slurry prepared in Examples 6 to 10 according to the above-mentioned separator preparation method, the puncture strength test of the separator was carried out according to the method in GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries". Among them, the puncture rate was 110 mm / min, and the test results are shown in Table 2 below: Table 2 Puncture Resistance Performance Test Results of Examples 6 to 10

[0064] It can be seen from Table 2 that compared with Example 6, the puncture strength of the separators prepared in Examples 7 to 10 was improved, indicating that the composite effect of 3,4-dimethoxybenzoic acid on nano-calcium carbonate can improve the puncture resistance performance of the separator; among them, compared with Examples 7 to 8, the puncture strength of the separators prepared in Examples 9 to 10 was improved, indicating that when the weight ratio of nano-calcium carbonate to 3,4-dimethoxybenzoic acid is 30:3 to 5, the composite effect of 3,4-dimethoxybenzoic acid on nano-calcium carbonate can reach the optimum, and the puncture strength of the separator can reach 17.9 to 18.1 N.

[0065] Experimental Example 3 After obtaining the separator from the low-foaming and high-adhesion lithium-ion battery slurry prepared in Example 1 according to the above-mentioned separator preparation method, air permeability test, basis weight test and peel strength test were carried out, where: ① Air permeability test: The air permeability of the separator was tested according to the method in GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries". Among them, the size of the separator specimen was 100 mm × 100 mm, and the test result was the average value of 3 specimens; ② Peel strength test: Three samples with a width of 15 mm were cut longitudinally from the separator, and the cut samples were adhered to the separator with transparent pressure-sensitive tape. After pasting, the free end of the sample was folded by 180°, and the bonding surface was peeled off by 15 mm by hand, and the peel strength was tested by a tensile testing machine; The test results are shown in Table 3 below: Table 3 Other Performance Test Results of Example 1

[0066] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A low-foaming high-adhesion lithium battery slurry, characterized in that It consists of the following components by weight percentage: 10% - 15% of polyvinylidene fluoride, 0.5% - 1.0% of dispersant, 9% - 15% of thickener, 10% - 20% of binder, 0.2% - 0.5% of defoamer, and the balance is water; The defoamer includes a polyether-polysiloxane copolymer and nano calcium carbonate with a weight ratio of 1 - 9:

1.

2. The low-foam high-adhesion lithium battery paste according to claim 1, wherein The weight ratio of the polyether-polysiloxane copolymer to nano calcium carbonate is 3 - 4:

1.

3. A low-foam high-adhesion lithium battery slurry according to claim 1, characterized in that, The polyether-polysiloxane copolymer includes the following components by weight parts: 1 - 2 parts of siloxane copolymer, 1 - 1.5 parts of organosilicon polyether, 0.05 - 0.1 part of thickener, 0.5 - 1.2 parts of emulsifier, 8 - 12 parts of organic solvent.

4. A low-foam high-adhesion lithium battery paste according to claim 3, characterized in that The preparation method of the polyether-polysiloxane copolymer includes the following steps: A1. Mix the siloxane copolymer, organosilicon polyether and organic solvent evenly, adjust the pH value to 8 - 10, react to obtain a mixture; A2. Add the remaining components of the polyether-polysiloxane copolymer to the mixture, mix evenly to obtain the polyether-polysiloxane copolymer.

5. A low-foam high-adhesion lithium battery paste according to claim 1, wherein, The nano calcium carbonate is 3,4-dimethoxybenzoic acid composite nano calcium carbonate, and the raw materials of the 3,4-dimethoxybenzoic acid composite nano calcium carbonate include nano calcium carbonate and 3,4-dimethoxybenzoic acid.

6. The low-foam high-adhesion lithium battery paste according to claim 5, wherein The weight ratio of the nano calcium carbonate to 3,4-dimethoxybenzoic acid is 30:3 - 5.

7. The low-foaming and high-adhesion lithium battery paste according to claim 1, characterized in that, The dispersant is one or more of ammonium polyacrylate, sodium dodecylbenzenesulfonate, sodium polyacrylate; and / or The thickener is one or two of sodium carboxymethyl cellulose, sodium carboxymethyl cellulose; The binder is one or two of bisphenol A epoxy resin, bisphenol F epoxy resin.

8. A low-foaming high-adhesion lithium battery paste according to claim 3, characterized in that The siloxane copolymer is N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; Among the components of the polyether-polysiloxane copolymer, the thickener is one or more of hydroxyethyl cellulose, alginic acid derivatives, polyethylene glycol 6000 distearate; and / or The emulsifier is one or more of polyoxyethylene ether, sorbitan stearate, methyl glucoside sesquistearate; and / or The organic solvent is one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide.

9. The preparation method of a low-foaming and high-adhesion lithium battery paste according to any one of claims 1 to 8, characterized in that, It includes the following steps: After mixing the polyvinylidene fluoride, dispersant, defoamer and water evenly, add the remaining components of the low-foaming high-adhesion lithium battery slurry, disperse evenly to obtain the low-foaming high-adhesion lithium battery slurry.

10. A separator is obtained by coating a base film with a low-foaming high-adhesion lithium battery slurry according to any one of claims 1 - 8 or a low-foaming high-adhesion lithium battery slurry prepared by the preparation method of claim 9; The base film is one of a polypropylene film and a polyethylene film.

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