Modified acrylic resin for negative electrode material and preparation method of negative electrode material

Abstract

This application relates to the field of negative electrode material technology, specifically disclosing a modified acrylic resin for use as a negative electrode material and a method for preparing the negative electrode material. The modified acrylic resin for use as a negative electrode material is composed of the following raw materials in parts by weight: 35-45 parts hydroxypropyl acrylate; 25-34 parts acrylamide. The modified acrylic resin is prepared by emulsion polymerization. The modified acrylic resin for use as a negative electrode material in this application can be used to prepare negative electrode materials and can address the issue of hydrogen evolution and leakage caused by corrosion of zinc electrodes.

Description

Technical Field

[0001] The present application relates to the technical field of negative electrode materials, and more specifically, to a modified acrylic resin for negative electrode materials and a method for preparing the negative electrode materials. Background Art

[0002] Alkaline zinc-manganese batteries are a new type of civilian power source, using zinc powder as their negative electrode material. While these batteries offer significant advantages and promising development prospects, they also face challenges. The zinc powder in the negative electrode of alkaline zinc-manganese batteries self-discharges in alkaline solutions. This self-discharge causes the zinc metal to dissolve and release hydrogen gas. The continuous accumulation of hydrogen gas increases the internal pressure of the battery, leading to leakage and posing a significant safety hazard.

[0003] To solve the problem of zinc electrode corrosion, hydrogen evolution and leakage, people usually add corrosion inhibitors to the electrolyte. However, some current corrosion inhibitors have poor corrosion inhibition effects, and the zinc electrode will still corrode to produce a large amount of hydrogen, causing battery leakage. Summary of the Invention

[0004] In order to solve the problem of hydrogen evolution and liquid leakage caused by corrosion of zinc electrodes, the present application provides a modified acrylic resin for negative electrode materials and a method for preparing the negative electrode materials.

[0005] In the first aspect, the modified acrylic resin for negative electrode materials provided in this application adopts the following technical solution:

[0006] A modified acrylic resin for negative electrode materials is prepared by emulsion polymerization. The modified acrylic resin is composed of the following raw materials in parts by weight: 35-45 parts of hydroxypropyl acrylate and 25-34 parts of acrylamide.

[0007] By adopting the above technical solution, hydroxypropyl acrylate and acrylamide are polymerized to form a modified acrylic resin. The modified acrylic resin contains hydroxyl groups, ester groups, and amide groups. The above groups contain O atoms and N atoms. The O atoms and N atoms have lone pairs of electrons, which can form coordinate covalent bonds with the negative electrode material zinc powder, so that the modified acrylic resin is adsorbed on the surface of the zinc powder and forms a protective film, reducing the possibility of water and hydroxide in the electrolyte contacting the zinc powder, inhibiting zinc corrosion, and inhibiting the generation of hydrogen, thereby solving the problem of zinc electrode corrosion and hydrogen evolution leakage.

[0008] Preferably, the preparation method of the modified acrylic resin comprises the following steps:

[0009] Adding emulsifier, hydroxypropyl acrylate and acrylamide into water and stirring to obtain an emulsion;

[0010] An initiator is added to the emulsion, the temperature is raised to 55-68° C. for polymerization reaction, the temperature is further raised to 80-85° C., the mixture is kept warm, dried, and crushed to obtain a modified acrylic resin.

[0011] By adopting the above technical solution and then raising the temperature to 80-85° C. at a later stage, the unreacted monomers in the emulsion can be reacted completely.

[0012] Preferably, the emulsifier is prepared by compounding dodecylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mass ratio of dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is (0.3-0.7):1.

[0013] By adopting the above technical solution, when the mass ratio of dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is (0.3-0.7):1, the obtained latex particles are not easy to agglomerate, the emulsion particle size distribution is narrow, and the emulsion stability is good.

[0014] Preferably, the mass ratio of the dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is (0.5-0.6):1.

[0015] By adopting the above technical solution and optimizing the mass ratio of dodecylphenol polyoxyethylene ether and sodium lauryl sulfate, the stability of the emulsion is further improved.

[0016] In a second aspect, the present application provides a method for preparing a negative electrode material, which adopts the following technical solution:

[0017] The negative electrode material is prepared by adding the modified acrylic resin to a KOH solution to obtain an electrolyte, wherein the weight of the modified acrylic resin accounts for 0.4-0.8 wt% of the weight of the electrolyte;

[0018] Zinc powder is added to the electrolyte and ball milled to obtain the negative electrode material, and the weight ratio of the electrolyte to the zinc powder is 1:(4-6).

[0019] By adopting the above technical solution, when the weight of the modified acrylic resin accounts for less than 0.4wt% of the weight of the electrolyte, the obtained film layer is too thin and the corrosion resistance of the zinc powder is poor; when the weight of the modified acrylic resin accounts for more than 0.8wt% of the weight of the electrolyte, the obtained film layer is too thick and uneven, and the corrosion resistance of the zinc powder is also poor.

[0020] Preferably, the weight ratio of the electrolyte to the zinc powder is 1:(4.5-5).

[0021] By adopting the above technical solution, when the weight ratio of electrolyte to zinc powder is 1:(4.5-5), the amount of electrolyte used is moderate, and the zinc electrode can react completely during discharge, avoiding corrosion and hydrogen evolution by the remaining zinc powder. In addition, the electrolyte is not easy to pierce the diaphragm and enter the positive electrode, and is not easy to cause alkaline leakage of the battery.

[0022] Preferably, bismuth chloride is added to the electrolyte, and the weight ratio of bismuth chloride to modified acrylic resin is (0.2-0.7):1.

[0023] By adopting this technical solution, bismuth chloride can, on the one hand, form bismuth through a replacement reaction, coating the zinc powder's surface with bismuth, increasing the zinc powder's hydrogen evolution overpotential and inhibiting zinc powder corrosion and hydrogen evolution. Furthermore, bismuth can accept lone pairs of electrons from the modified acrylic resin, coordinate with the modified acrylic resin, and enhance the adsorption of the film formed by the modified acrylic resin to the zinc powder. The synergistic effect of bismuth chloride and the modified acrylic resin solves the problem of zinc electrode corrosion and hydrogen evolution leakage. When the battery discharges, the film will fall off due to changes in potential, thus not affecting battery discharge. Once the battery is in an open circuit state, the film will re-adsorb onto the zinc powder's surface, inhibiting zinc corrosion.

[0024] Preferably, the weight ratio of the bismuth chloride to the modified acrylic resin is (0.4-0.5):1.

[0025] By adopting the above technical solution, when the weight ratio of bismuth chloride to modified acrylic resin is (0.4-0.5):1, the synergistic effect between the two is more obvious.

[0026] Preferably, a binder is added to the electrolyte, and the weight of the binder accounts for 0.1-0.3wt% of the weight of the electrolyte; the binder is prepared by compounding polyacrylic acid and sodium polyacrylate, and the weight ratio of polyacrylic acid to sodium polyacrylate is (1.8-2):1.

[0027] Polyacrylic acid acts as a binder in the zinc paste, and sodium polyacrylate is not easily hydrolyzed and acts as a thickener in the battery zinc paste. When the weight of the binder accounts for 0.1-0.3wt% of the weight of the electrolyte and the weight ratio of polyacrylic acid to sodium polyacrylate is (1.8-2):1, the negative electrode material has moderate adhesion and consistency, good conductivity, and complete reaction during discharge of the zinc electrode, reducing the possibility of residual zinc powder corroding and releasing hydrogen. The electrolyte will not enter the positive electrode, causing the negative electrode zinc powder to lack electrolyte, and the zinc powder will not be exposed to alkaline solution and corroded and released hydrogen.

[0028] In summary, this application has the following beneficial effects:

[0029] 1. This application uses hydroxypropyl acrylate and acrylamide to prepare a modified acrylic resin. The modified acrylic resin contains oxygen atoms and nitrogen atoms. The lone pairs of electrons on the oxygen atoms and nitrogen atoms can coordinate with zinc to form a film layer adsorbed on the surface of the zinc powder, blocking water and hydroxide from contacting the zinc powder, inhibiting hydrogen evolution corrosion of zinc, and solving the problem of zinc electrode corrosion and hydrogen evolution leakage.

[0030] 2. In the present application, bismuth chloride is added to the electrolyte. On the one hand, bismuth chloride can generate bismuth through a replacement reaction and cover the surface of the zinc powder, thereby increasing the hydrogen evolution overpotential of the zinc powder. On the other hand, bismuth can coordinate with the modified acrylic resin to enhance the adsorption of the film layer and the zinc powder. The synergistic effect of bismuth chloride and the modified acrylic resin solves the problem of hydrogen evolution leakage caused by corrosion of the zinc electrode.

[0031] 3. The present application adds a binder to the electrolyte. By optimizing the binder components and ratios, a negative electrode material with moderate adhesion and consistency and good conductivity is obtained. The zinc electrode reacts completely during discharge, suppressing the possibility of hydrogen evolution due to zinc powder corrosion. DETAILED DESCRIPTION

[0032] The present application is further described in detail below with reference to the embodiments.

[0033] Example

[0034] Example 1

[0035] The modified acrylic resin used for negative electrode materials has the following formula:

[0036] Hydroxypropyl acrylate 35g; Acrylamide 25g.

[0037] The preparation method of modified acrylic resin for negative electrode material comprises the following steps:

[0038] Add emulsifiers (dodecylphenol polyoxyethylene ether and sodium lauryl sulfate), hydroxypropyl acrylate, and acrylamide into water and stir to obtain an emulsion, wherein the weight of the emulsifier accounts for 0.1wt% of the total weight of hydroxypropyl acrylate and acrylamide, and the mass ratio of dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is 0.3:1;

[0039] An initiator (sodium persulfate) was added to the emulsion, and the temperature was initially raised to 55° C. for polymerization reaction, kept warm, dried, and crushed to obtain a modified acrylic resin. The weight of the initiator accounted for 0.08 wt % of the total weight of hydroxypropyl acrylate and acrylamide.

[0040] Example 2-3

[0041] The modified acrylic resin used for the negative electrode material is different from that of Example 1 in that the raw material composition of the modified acrylic resin is different. The specific composition is shown in Table 1 below:

[0042] Table 1. Raw material composition

[0043] project Hydroxypropyl acrylate (g) Acrylamide (g) Example 1 35 25 Example 2 45 34 Example 3 40 30

[0044] Examples 4-5

[0045] The modified acrylic resin used for the negative electrode material is different from that of Example 3 in that the temperature at which the emulsion is initially heated during the polymerization reaction is different. The specific temperatures are shown in Table 2 below:

[0046] Table 2. Temperature of initial heating

[0047] project Initial heating temperature (℃) Example 3 55 Example 4 68 Example 5 63

[0048] Examples 6-8

[0049] The modified acrylic resin used for the negative electrode material is different from that in Example 5 in that: after the initial polymerization reaction of the emulsion at elevated temperature, the emulsion is heated again. The specific temperatures are shown in Table 3 below:

[0050] Table 3. Reheating temperature

[0051] project Reheating temperature (℃) Example 6 80 Example 7 85 Example 8 82

[0052] Examples 9-12

[0053] The modified acrylic resin used for the negative electrode material is different from that of Example 8 in that the mass ratio of dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is different. The specific mass ratios are shown in Table 4 below:

[0054] Table 4. Mass ratio of dodecylphenol polyoxyethylene ether and sodium lauryl sulfate

[0055]

[0056]

[0057] Comparative Example

[0058] Comparative Example 1

[0059] The modified acrylic resin used for the negative electrode material is different from that in Example 12 in that acrylamide is replaced by ethyl acrylate.

[0060] Comparative Example 2

[0061] The modified acrylic resin used for the negative electrode material is different from that in Example 12 in that hydroxypropyl acrylate is replaced by ethyl acrylate.

[0062] Comparative Example 3

[0063] The modified acrylic resin used for the negative electrode material is different from that in Example 12 in that hydroxypropyl acrylate is replaced by 2-butenol.

[0064] Application Examples

[0065] Application Examples 1-12

[0066] The method for preparing the negative electrode material comprises the following steps:

[0067] The modified acrylic resin prepared in Example 1-12 was added to a 40% KOH solution and stirred to obtain an electrolyte, wherein the weight of the modified acrylic resin accounted for 0.4 wt % of the weight of the electrolyte;

[0068] Zinc powder was added to the electrolyte and ball-milled to obtain the negative electrode material. The weight ratio of the electrolyte to the zinc powder was 1:4. The sources of the modified acrylic resin used in Application Examples 1-12 are shown in Table 5 below:

[0069] Table 5. Sources of modified acrylic resins

[0070]

[0071]

[0072] Application Examples 13-14

[0073] The difference between the preparation method of the negative electrode material and Application Example 12 is that the weight percentage of the modified acrylic resin to the weight of the electrolyte is different, and the specific percentage is shown in Table 6 below:

[0074] Table 6. Weight of modified acrylic resin as a percentage of electrolyte weight

[0075]

[0076] Application Examples 15-18

[0077] The method for preparing the negative electrode material differs from that of Application Example 14 in that the weight ratio of the electrolyte to the zinc powder is different. The specific weight ratios are shown in Table 7 below:

[0078] Table 7. Weight ratio of electrolyte to zinc powder

[0079] project Weight ratio of electrolyte to zinc powder Application Example 14 1:4 Application Example 15 1:6 Application Example 16 1:4.5 Application Example 17 1:5 Application Example 18 1:4.7

[0080] Application Examples 19-23

[0081] The method for preparing the negative electrode material differs from that of Application Example 18 in that bismuth chloride is added to the electrolyte. The weight ratio of bismuth chloride to modified acrylic resin is shown in Table 8 below:

[0082] Table 8. Weight ratio of bismuth chloride to modified acrylic resin

[0083]

[0084]

[0085] Application Examples 24-26

[0086] The method for preparing the negative electrode material differs from that of Application Example 23 in that a binder is added to the electrolyte, and the weight percentage of the binder to the weight of the electrolyte is shown in Table 9 below; the binder is prepared by compounding polyacrylic acid and sodium polyacrylate, and the weight ratio of polyacrylic acid to sodium polyacrylate is 1.8:1.

[0087] Table 9. Percentage of binder weight to electrolyte weight

[0088] project The weight of the binder as a percentage of the electrolyte weight (wt%) Application Example 24 0.1 Application Example 25 0.3 Application Example 26 0.2

[0089] Application Examples 27-28

[0090] The method for preparing the negative electrode material differs from that of Application Example 26 in that the weight ratio of polyacrylic acid to sodium polyacrylate is different. The specific mass ratios are shown in Table 10 below:

[0091] Table 10. Weight ratio of polyacrylic acid and sodium polyacrylate

[0092] project Weight ratio of polyacrylic acid and sodium polyacrylate Application Example 26 1.8:1 Application Example 27 2:1 Application Example 28 1.9:1

[0093] Application comparison

[0094] Application Comparative Examples 1-3

[0095] The method for preparing the negative electrode material differs from that of Application Example 12 in that the source of the modified acrylic resin is different. The specific sources are shown in Table 11 below:

[0096] Table 11. Sources of modified acrylic resins

[0097] project Sources of modified acrylic resin Comparative Application Example 1 Comparative Example 1 Application Comparative Example 2 Comparative Example 2 Application Comparative Example 3 Comparative Example 3

[0098] Application Comparative Examples 4-5

[0099] The difference between the preparation method of the negative electrode material and Application Example 12 is that the weight percentage of the modified acrylic resin to the weight of the electrolyte is different, and the specific percentage is shown in Table 12 below:

[0100] Table 12. Weight of modified acrylic resin as a percentage of electrolyte weight

[0101]

[0102] Detection method

[0103] Equal masses of Application Examples 1-28, Comparative Application Examples 1-5, and a blank control group (zinc powder was added to a 40% KOH electrolyte and ball-milled to obtain a negative electrode material, with the weight ratio of electrolyte to zinc powder being 1:4) were added.

[0104] The prepared negative electrode materials are added to the gas generator through the feeding port, and the feeding port is tightly plugged with a ground-mouth plug made of vaseline. The gas generator is connected to the liquid storage bottle through an air duct, and water is injected into the liquid storage bottle. The liquid storage bottle is provided with a liquid duct extending to the bottom of the bottle, and the liquid duct is connected to the liquid volumetric flask. The liquid volumetric flask is provided with a scale, and the gas generating device is kept warm at 45°C.

[0105] The amount of hydrogen generated by the negative electrode material was measured by the water displacement method, and the amount of hydrogen evolved after 6 days was obtained by observing the change in the liquid level scale of each liquid volumetric flask. The percentage of the hydrogen evolved amount of the negative electrode materials prepared in Application Examples 1-28 and Comparative Examples 1-5 to the hydrogen evolved amount of the blank control group was calculated to evaluate the corrosion inhibition effect of the negative electrode material. The specific test results are shown in Table 13 below.

[0106] Table 13. Negative electrode material performance test

[0107]

[0108]

[0109] It can be seen from Table 13 that the negative electrode materials prepared in the application examples of this application have good corrosion resistance. The percentage of hydrogen evolution in application examples 1-28 to the blank control group is less than 41%, among which application example 28 is the best application example.

[0110] Combining Application Example 12 with Comparative Application Examples 1-3 and Table 13, it can be seen that the amount of hydrogen evolution in the negative electrode material prepared in Application Example 12 accounts for 26% of the blank control group, which is much lower than that in Comparative Application Examples 1-3. This may be because the modified acrylic resin in Example 12 is polymerized from acrylamide and hydroxypropyl acrylate. The acrylamide contains an amide group, and the N atom on the amide group has a lone pair of electrons, which can form a coordinate covalent bond with the zinc powder of the negative electrode material, resulting in a film with strong adsorption capacity. The hydroxypropyl acrylate contains a hydroxyl group and an ester group, and both the hydroxyl group and the ester group contain an O atom, which has a lone pair of electrons and can form a coordinate covalent bond with the zinc powder of the negative electrode material. The film formed has a strong adsorption capacity, which can solve the problem of hydrogen evolution and leakage caused by zinc electrode corrosion.

[0111] Combining Application Example 12 with Comparative Examples 4-5 and Table 13, it can be seen that the amount of hydrogen evolution of the negative electrode material prepared in Application Example 12 accounts for 26% of the blank control group, which is much lower than that of Comparative Examples 4-5. This may be because: in Comparative Example 4, when the weight of the modified acrylic resin accounts for less than 0.4wt% of the weight of the electrolyte, the obtained film layer is too thin and the corrosion resistance of the zinc powder is poor; in Comparative Example 5, when the weight of the modified acrylic resin accounts for more than 0.8wt% of the weight of the electrolyte, the obtained film layer is too thick and uneven, and the corrosion resistance of the zinc powder is also poor.

[0112] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a negative electrode material, characterized in that: The steps include: 1) adding a modified acrylic resin to a KOH solution to obtain an electrolyte, wherein the weight of the modified acrylic resin accounts for 0.4-0.8wt% of the weight of the electrolyte, and the modified acrylic resin is composed of the following raw materials in parts by weight: 35-45 parts of hydroxypropyl acrylate; 25-34 parts of acrylamide, and the modified acrylic resin is prepared by emulsion polymerization; adding a binder to the electrolyte, wherein the weight of the binder accounts for 0.1-0.3wt% of the weight of the electrolyte; the binder is prepared by compounding polyacrylic acid and sodium polyacrylate, and the weight ratio of polyacrylic acid to sodium polyacrylate is (1.8-2):1; 2) Add zinc powder to the electrolyte and ball mill to obtain the negative electrode material. The weight ratio of electrolyte to zinc powder is 1:(4-6).

2. The preparation method according to claim 1, characterized in that The preparation method of the modified acrylic resin comprises the following steps: adding an emulsifier, hydroxypropyl acrylate and acrylamide into water and stirring to obtain an emulsion; adding an initiator into the emulsion, heating the emulsion to 55-68° C. for polymerization reaction, heating the emulsion to 80-85° C., keeping the temperature, drying and crushing to obtain the modified acrylic resin.

3. The preparation method according to claim 2, wherein: The emulsifier is prepared by compounding dodecylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mass ratio of dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is (0.3-0.7):

1.

4. The preparation method according to claim 3, wherein: The mass ratio of the dodecylphenol polyoxyethylene ether to sodium lauryl sulfate is (0.5-0.6):

1.

5. The preparation method according to claim 1, wherein: The weight ratio of the electrolyte to the zinc powder is 1:(4.5-5).

6. The preparation method according to claim 1, wherein: Bismuth chloride is added to the electrolyte, and the weight ratio of bismuth chloride to modified acrylic resin is (0.2-0.7):

1.

7. The preparation method according to claim 6, characterized in that: The weight ratio of the bismuth chloride to the modified acrylic resin is (0.4-0.5):1.

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