A gelatin-based aqueous binder for hard carbon anode of sodium-ion battery and its preparation method

Abstract

The present invention relates to the field of binders, and specifically, to a gelatin-based aqueous binder for hard carbon anodes of sodium-ion batteries and a preparation method thereof. The raw materials for preparing the gelatin-based aqueous binder for hard carbon anodes of sodium-ion batteries include: gelatin, acrylic acid monomers, acrylate monomers, acrylic polyol esters, initiators, pH regulators, and deionized water; wherein the acrylic polyol esters include ethylene glycol diacrylate. The gelatin-based aqueous binder for hard carbon anodes of sodium-ion batteries prepared by the present invention has excellent adhesion performance, and the peel strength can reach 8 N / m, showing significant progress compared with the prior art.

Description

Technical Field

[0001] The present invention relates to the field of binders, and more specifically, to a gelatin-based aqueous binder for hard carbon anodes of sodium-ion batteries and a preparation method thereof. Background Art

[0002] Sodium is one of the common elements on the earth, and its resource reserves are abundant, far higher than those of lithium. Therefore, sodium-ion batteries have significant advantages in terms of raw material costs, which is conducive to reducing the overall manufacturing cost of the batteries. Generally speaking, the cost of sodium-ion batteries can be reduced by 30% - 40% compared with that of lithium-ion batteries. In terms of safety, sodium-ion batteries have an ultra-wide operating temperature range, and the normal operating temperature range is from -40 °C to 800 °C. Even at high temperatures, it is not easy to have thermal runaway. Compared with lithium-ion batteries, the short-circuit current and instantaneous heat generation of sodium-ion batteries are smaller, and it is less likely to cause fire or spontaneous combustion. In addition, although the production of sodium-ion batteries also involves raw materials such as heavy metals, compared with the environmental impact of lithium ore mining for lithium-ion batteries, the damage to the environment caused by sodium-ion batteries in terms of raw material acquisition is relatively smaller.

[0003] The ionic radius of sodium ions is much larger than that of lithium ions, and conventional soft carbon graphite anodes are not suitable. It is necessary to adjust to amorphous carbon anode materials. Amorphous carbon has the characteristics of a large specific surface area, small particle size, and low tap density, and has higher requirements for the adhesion and cohesion of the binder. Currently, for carbon anode materials, common binders include SBR or CMC. For example, patent document CN110854367B discloses a slurry of a silicon-carbon anode material, and its preparation raw materials include SBR (styrene-butadiene latex binder) and CMC (sodium carboxymethyl cellulose); however, the binding performance of SBR or CMC to carbon materials is limited, and the application effect is average.

[0004] Based on this, for those skilled in the art, how to prepare an adhesive with high peel strength and suitable for hard carbon anodes of sodium-ion batteries is an industry-wide technical problem that needs to be solved urgently at present. Summary of the Invention

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a gelatin-based aqueous binder for hard carbon anodes of sodium-ion batteries, and its preparation raw materials include: gelatin, acrylic acid monomer, acrylate monomer, acrylic polyol ester, initiator, pH regulator, and deionized water.

[0006] As an implementable case, the mass ratio of the gelatin, acrylic acid monomer, acrylate monomer, acrylic polyol ester, and initiator is (10 - 15):(1 - 3):(5 - 8):(0.5 - 1):(0.1 - 0.6).

[0007] The gelatin molecular chain contains active groups such as amino, carboxyl, and hydroxyl groups, which can react with acrylic monomers, acrylate monomers, and acrylic polyol esters to achieve the modification of gelatin. Through modification, the physical and chemical properties of the gelatin-based binder can be adjusted to meet the requirements of the hard carbon anode of sodium-ion batteries; in addition, through physical or chemical cross-linking modification, gels with an interpenetrating network structure or a double network structure can be formed, and the product has reversible bonding properties. At the same time, gelatin can absorb 5-10 times its weight of water, which enables the gelatin-based waterborne binder to maintain good bonding properties in a humid environment, especially suitable for use in sodium-ion batteries.

[0008] As an implementable case, the acrylic monomers described include: acrylic acid and / or methacrylic acid.

[0009] As an implementable case, the acrylate monomers described include: one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate.

[0010] Furthermore, the acrylate monomers described include: one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxyethyl methacrylate.

[0011] As an implementable case, the acrylic polyol esters described include: one or more of ethylene glycol diacrylate, 1,4-butanediol diacrylate, pentaerythritol triacrylate, and bisphenol A glycerol dimethacrylate.

[0012] Furthermore, the acrylic polyol ester is ethylene glycol diacrylate.

[0013] Acrylic polyol esters can increase the cohesion and strength of the binder, which helps to improve the bonding performance of the product. An appropriate amount of acrylic monomers can improve the wettability and adhesion between the polymer and the carbon anode material, thereby enhancing the bonding performance; acrylate monomers contain hydroxyl functional groups, which can form hydrogen bonds with the polar groups on the surface of the carbon anode material, enhancing the binding force between the polymer and the carbon anode material; at the same time, acrylate monomers can also be used as cross-linking agents to increase the cross-linking density and water resistance of the polymer, which helps to improve the bonding performance. The inventors of the present invention found that when acrylic monomers, acrylate monomers, and acrylic polyol esters are selected as raw materials and undergo a cross-linking reaction under an initiator to form a three-dimensional network structure with a high cross-linking density; the increase in the cross-linking density helps to improve the cohesion and strength of the adhesive, thereby enhancing the bonding performance, and the peel strength of the product can reach more than 8 N / m.

[0014] As an implementable case, the initiator is an azo initiator and / or a peroxide initiator.

[0015] As an implementable case, the azo initiator includes one or more of azobisisobutyronitrile, azodiisopentanenitrile, azodiisobutamidine hydrochloride, and azodiisobimidazoline hydrochloride.

[0016] As an implementable case, the peroxide initiator includes one or more of benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, cumene hydroperoxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, tert-butyl peroxybenzoate, cumene hydroperoxide, tert-butyl hydroperoxide, ammonium persulfate, potassium persulfate, and sodium persulfate.

[0017] Furthermore, the initiator includes one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0018] As an implementable case, the pH regulator includes one of aqueous sodium hydroxide solution, aqueous lithium hydroxide solution, aqueous sodium bicarbonate solution, and ammonia water.

[0019] As an implementable case, the mass concentration of the aqueous sodium hydroxide solution is 1-3 wt%.

[0020] The second aspect of the present invention provides a preparation method of a water-based binder for a hard carbon negative electrode of a gelatin-based sodium ion battery, including:

[0021] S1. Mix deionized water, gelatin, and acrylic acid monomer, add them to a reaction kettle, heat up to 35-40 °C, and stir for 30-60 min;

[0022] S2. Then add acrylate monomer, acrylic polyol ester, and initiator, and under the atmosphere of inert gas, heat up to 55-65 °C, and then react for 5-10 h;

[0023] S3. After the reaction is completed, cool the system to room temperature, then add a pH regulator to adjust the pH of the system to 6.5-7.5, and then dilute and stir evenly to obtain the product.

[0024] Beneficial effects

[0025] (1) The present invention selects gelatin as the main raw material for preparing the binder, which can ensure that the product has certain binding properties, and gelatin has high stability at high and low temperatures, especially suitable for use in sodium ion batteries; in addition, gelatin not only does not cause harmful effects on the human body, but can also be naturally degraded in the organism, avoiding the environmental protection problems that may be brought by traditional binders.

[0026] (2) The present invention selects acrylic monomers, acrylate monomers, and polyacrylate polyols to be compounded as raw materials for the binder. The three components can undergo a cross-linking polymerization reaction, which can further improve the bonding performance of the product, and the peel strength can reach more than 8 N / m.

[0027] (3) In the present invention, the mass ratio of acrylic monomers, acrylate monomers, and polyacrylate polyols is further defined as (1 - 3):(5 - 8):(0.5 - 1), which can further improve the cohesion and strength of the binder and extend its service life.

[0028] (4) The raw materials for preparation in the present invention do not include organic solvents, the product system is relatively environmentally friendly, and the preparation process is relatively simple. It only needs to add the raw materials in a certain feeding order, stir, and react to obtain the product; the raw materials have a wide source, relatively low cost, and excellent use performance of the product, especially suitable for use in the hard carbon negative electrode of sodium-ion batteries.

[0029] (5) At present, most of the binders used in the hard carbon negative electrode of sodium-ion batteries on the market are prepared from SBR and CMC as raw materials, but their bonding performance is average. However, a novel modified gelatin-based aqueous binder for the hard carbon negative electrode of sodium-ion batteries provided by the present invention has more excellent bonding performance and significant progress compared with the prior art. Description of the Drawings

[0030] Figure 1 Schematic diagram of the peel strength of the gelatin-based aqueous binder for the hard carbon negative electrode of sodium-ion batteries prepared in Example 1. Detailed Description of the Invention

[0031] Example 1

[0032] In the first aspect of this example, a gelatin-based aqueous binder for the hard carbon negative electrode of sodium-ion batteries is provided. Its raw materials for preparation include, by weight: 100 g of gelatin, 10 g of acrylic acid, 50 g of hydroxyethyl acrylate, 5 g of ethylene glycol diacrylate, 1.65 g of ammonium persulfate, 555 g of an aqueous sodium hydroxide solution with a mass concentration of 1 wt%, and 2148 g of deionized water.

[0033] The gelatin is purchased from Hengshui Hongcai Adhesive Co., Ltd.

[0034] In the second aspect of this example, a preparation method of a gelatin-based aqueous binder for the hard carbon negative electrode of sodium-ion batteries is provided, including:

[0035] S1. By weight, 835 g of deionized water, 100 g of gelatin, and 10 g of acrylic acid are mixed, added to a reaction kettle, heated to 35 °C, and stirred for 45 min until the gelatin is completely dissolved;

[0036] S2. Then add 50 g of hydroxyethyl acrylate, 5 g of ethylene glycol diacrylate and 1.65 g of ammonium persulfate, introduce high-purity nitrogen at 0.1 MPa, with the gas introduction time being 30 min, heat up to 65 °C under a nitrogen atmosphere, and react for 8 h;

[0037] S3. After the reaction is completed, cool the system to room temperature of 25 °C, then add 555 g of an aqueous sodium hydroxide solution with a mass concentration of 1 wt%, adjust the pH of the system to 6.8, add 1313 g of deionized water to dilute the product to a solid content of 6%, and stir evenly to obtain the product.

[0038] The schematic diagram of the peel strength of the water-based binder for the hard carbon anode of the gelatin-based sodium-ion battery prepared in this example is as Figure 1 shown; a total of 4 tests were conducted, and the average value of the 4 tests was taken as the final result.

[0039] Example 2

[0040] In the first aspect of this example, a water-based binder for the hard carbon anode of a gelatin-based sodium-ion battery is provided. Its preparation raw materials by weight include: 150 g of gelatin, 30 g of acrylic acid, 80 g of hydroxyethyl acrylate, 10 g of ethylene glycol diacrylate, 5.4 g of ammonium persulfate, 833 g of an aqueous sodium hydroxide solution with a mass concentration of 2 wt% and 3760 g of deionized water.

[0041] The gelatin is purchased from Hengshui Hongcai Adhesive Co., Ltd.

[0042] In the second aspect of this example, a preparation method of a water-based binder for the hard carbon anode of a gelatin-based sodium-ion battery is provided, including:

[0043] S1. By weight, mix 730 g of deionized water, 150 g of gelatin and 30 g of acrylic acid, add them to a reaction kettle, heat up to 35 °C, and stir for 45 min until the gelatin is completely dissolved;

[0044] S2. Then add 80 g of hydroxyethyl acrylate, 10 g of ethylene glycol diacrylate and 5.4 g of ammonium persulfate, introduce high-purity nitrogen at 0.1 MPa, with the gas introduction time being 30 min, heat up to 55 °C under a nitrogen atmosphere, and react for 5 h;

[0045] S3. After the reaction is completed, cool the system to room temperature of 25 °C, then add 833 g of an aqueous sodium hydroxide solution with a mass concentration of 2 wt%, adjust the pH of the system to 7.0, add 3030 g of deionized water to dilute the product to a solid content of 6%, and stir evenly to obtain the product.

[0046] Example 3

[0047] In the first aspect of this example, a water-based binder for hard carbon anode of gelatin-based sodium ion battery is provided. The preparation raw materials include, by weight: 120 g of gelatin, 20 g of methacrylic acid, 65 g of 2-hydroxyethyl acrylate, 7 g of ethylene glycol diacrylate, 2.12 g of ammonium persulfate, 310 g of sodium hydroxide aqueous solution with a mass concentration of 3 wt%, and 3199 g of deionized water.

[0048] The gelatin is purchased from Hengshui Hongcai Adhesive Co., Ltd.

[0049] In the second aspect of this example, a preparation method of a water-based binder for hard carbon anode of gelatin-based sodium ion battery is provided, including:

[0050] S1. Mix 786 g of deionized water, 120 g of gelatin and 20 g of methacrylic acid by weight, add them into a reaction kettle, heat up to 35 °C, and stir for 45 min until the gelatin is completely dissolved;

[0051] S2. Then add 65 g of 2-hydroxypropyl acrylate, 7 g of ethylene glycol diacrylate and 2.12 g of ammonium persulfate, introduce high-purity nitrogen with a pressure of 0.1 MPa, the gas injection time is 30 min, heat up to 60 °C under the nitrogen atmosphere, and react for 7 h;

[0052] S3. After the reaction is completed, cool the system to room temperature of 25 °C, then add 310 g of sodium hydroxide aqueous solution with a mass concentration of 3 wt%, adjust the pH of the system to 6.9, add 2413 g of deionized water to dilute the product to a solid content of 6%, and stir evenly to obtain.

[0053] Example 4

[0054] In the first aspect of this example, a water-based binder for hard carbon anode of gelatin-based sodium ion battery is provided. The preparation raw materials include, by weight: 140 g of gelatin, 15 g of methacrylic acid, 70 g of 2-hydroxypropyl acrylate, 8 g of ethylene glycol diacrylate, 2.33 g of ammonium persulfate, 555 g of sodium hydroxide aqueous solution with a mass concentration of 3 wt%, and 2752 g of deionized water.

[0055] The gelatin is purchased from Hengshui Hongcai Adhesive Co., Ltd.

[0056] In the second aspect of this example, a preparation method of a water-based binder for hard carbon anode of gelatin-based sodium ion battery is provided, including:

[0057] S1. Mix 765 g of deionized water, 140 g of gelatin and 15 g of methacrylic acid by weight, add them into a reaction kettle, heat up to 40 °C, and stir for 40 min until the gelatin is completely dissolved;

[0058] S2. Then add 70 g of hydroxypropyl acrylate, 8 g of ethylene glycol diacrylate and 2.33 g of ammonium persulfate, introduce high-purity nitrogen at 0.1 MPa, with the aeration time being 30 min. Heat up to 60 °C under a nitrogen atmosphere and react for 6 h;

[0059] S3. After the reaction ends, cool the system to room temperature of 25 °C, then add 555 g of an aqueous sodium hydroxide solution with a mass concentration of 3 wt%, adjust the pH of the system to 6.8, add 1987 g of deionized water to dilute the product to a solid content of 6%, and stir evenly to obtain the product.

[0060] Comparative Example 1

[0061] This example provides an aqueous binder. By weight, the raw materials for preparation include: 29.47 g of SBR (50% solid content), 6.32 g of CMC, and 423.23 g of deionized water.

[0062] The preparation method of the aqueous binder is as follows: Mix and stir 29.47 g of SBR, 6.32 g of CMC, and 423.23 g of deionized water at room temperature of 25 °C to obtain the product.

[0063] The SBR and CMC mentioned above are both purchased from Guangzhou Songbai Chemical Industry Co., Ltd.

[0064] Comparative Example 2

[0065] The specific implementation method of this example is the same as that of Example 1, and the difference is that the raw materials for preparation in this example do not include ethylene glycol diacrylate.

[0066] Performance Test

[0067] 1. Peel Strength

[0068] Dilute 216 g of the binder of Examples 1 - 4 with 243 g of deionized water, add 5 g of conductive agent and 500 g of hard carbon material. After the raw materials are completely infiltrated, disperse them at high speed for 4 h (rotation speed: linear velocity 10 m / min), then add 72 g of deionized water to adjust the viscosity to 2500 mPa·s. Coat the prepared slurry on the copper foil through a single-sided intermittent coater and bake it, then perform coating again. Place the coated electrode sheet in an oven at 120 °C and dry it for 12 h. Roll press, cut the dried electrode sheet, and measure it according to the 180° peel strength test method for adhesives in GB / T 2790 - 1995.

[0069] Specific test method for Comparative Example 1: 5.26 g of conductive agent and 500 g of hard carbon material were added to 459.02 g of the binder of Comparative Example 1. After the raw materials were completely infiltrated, they were dispersed at high speed for 4 h. Then, 77 g of deionized water was added to adjust the viscosity to 2500 mPa·s. The prepared slurry was coated on copper foil by a single-sided intermittent coater and baked, and then coated again (single-sided coating, areal density of 0.95 g / dm 2 ), and the coated electrode was placed in an oven at 120 °C and dried for 12 h. The dried electrode was rolled, cut, and measured according to the adhesive 180° peel strength test method in GB / T 2790-1995.

[0070] The above-mentioned conductive agent was of the model Super P and was purchased from Shanghai Huiping New Energy Co., Ltd.; the hard carbon material was of the model BSHC-300 and was purchased from BETRAY New Energy Materials Group Co., Ltd.

[0071] See Figure 1 and Table 1 for the test results.

[0072] Table 1

[0073]

[0074] Among them, the peel strength of Example 1 was the average value of 4 tests, and the specific peel strength test results corresponded to Table 2.

[0075] Table 2

[0076]

[0077] Among them, serial number 1 represents Figure 1 the data of the red line in

[0078] Serial number 2 represents Figure 1 the data of the yellow line in

[0079] Serial number 3 represents Figure 1 the data of the blue line in

[0080] Serial number 4 represents Figure 1 the data of the green line in

[0081] It can be seen from the test results of the above Examples 1-4 that the peel strength of the binder prepared by the present invention is above 8 N / m, while the peel strength of the aqueous binder prepared by compounding SBR and CMC in the prior art is significantly less than the product provided by the present invention; in addition, it can be seen from Comparative Example 2 that the non-addition of acrylic polyol ester also has a significant impact on the bonding performance of the product.

Claims

1. A gelatin-based sodium ion battery hard carbon negative electrode aqueous binder, characterized in that: The preparation raw materials include: gelatin, acrylic acid monomer, acrylic ester monomer, acrylic acid polyol ester, initiator, pH regulator and deionized water; The mass ratio of the gelatin, acrylic acid monomer, acrylic ester monomer, acrylic acid polyol ester and initiator is (10-15): (1-3): (5-8): (0.5-1): (0.1-0.6); The acrylic polyol ester includes one or more of ethylene glycol diacrylate, 1,4-butylene glycol diacrylate, pentaerythritol triacrylate, and bisphenol A propylene glycol dimethacrylate.

2. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to claim 1, characterized in that: The acrylic acid monomers include: acrylic acid and / or methacrylic acid.

3. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to claim 1, characterized in that: The acrylic acid ester monomers include: one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, hydroxymethyl acrylate, hydroxyethyl acrylate and hydroxypropyl acrylate.

4. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to any one of claims 1 to 3, characterized in that: The initiator is an azo initiator and / or a peroxide initiator.

5. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to claim 4, characterized in that: The azo initiator includes one or more of azobisisobutyronitrile, azobisisoheptylnitrile, azobisisobutyramidine hydrochloride, and azobisisobutylimidazoline hydrochloride.

6. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to claim 4, characterized in that: The peroxide initiator includes one or more of benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, diisopropyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, tert-butyl perbenzoate, cumene hydroperoxide, tert-butyl hydroperoxide, ammonium persulfate, potassium persulfate, and sodium persulfate.

7. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to claim 1, characterized in that: The pH regulator comprises: one of a sodium hydroxide aqueous solution, a lithium hydroxide aqueous solution, a sodium bicarbonate aqueous solution, and ammonia water.

8. The gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to claim 7, characterized in that: The mass concentration of the sodium hydroxide aqueous solution is 1-3wt%.

9. A method for preparing a gelatin-based sodium ion battery hard carbon negative electrode aqueous binder according to any one of claims 1 to 8, characterized in that: include: S1. Mix deionized water, gelatin and acrylic acid monomer, add them into a reactor, heat to 35-40°C, and stir for 30-60 minutes; S2, adding acrylate monomer, acrylic polyol and initiator, heating to 55-65°C in an inert gas atmosphere, and then reacting for 5-10 hours; S3. After the reaction is completed, the system is cooled to room temperature, and a pH regulator is added to adjust the pH of the system to 6.5-7.5, and then diluted and stirred evenly to obtain the product.

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