Negative plate grid and preparation method thereof

Abstract

The invention discloses a negative plate grid and a preparation method thereof, and belongs to the technical field of preparation of electrode materials, and the negative plate grid comprises a lead plate grid blank body and lead paste covering the surface of the lead plate grid blank body, the lead paste comprises the following raw materials: lead powder, deionized water, cationic polyacrylamide, graphene, activated carbon, concentrated sulfuric acid, bamboo charcoal fibers, modified silicon dioxide and sodium sulfate; wherein the modified silicon dioxide is silicon dioxide grafted by hyperbranched polysilane, and the hyperbranched polysilane is obtained by carrying out hydrolytic condensation on gamma-glycidyl ether oxypropyl trimethoxy silane, heptadecafluorodecyl trimethoxy silane and 3-{[dimethyl (3-trimethoxy silyl) propyl] ammonium}-propane-1-sulfonate. The negative plate grid prepared by the invention has excellent corrosion resistance, and has excellent cycle performance and conductivity after being assembled into a battery.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of electrode materials, and in particular relates to a negative electrode grid and a preparation method thereof. Background Art

[0002] With the advent of the new energy era, electric vehicles (including hybrid and pure electric power) are developing rapidly. At present, the heart of electric vehicles, the power part - batteries, has become the focus of the electric vehicle industry. In the context that the safety and cost-effectiveness of lithium batteries have yet to be significantly improved, and other chemical power sources have not yet been widely used by civilians, lead-acid batteries have become the core power source of the electric vehicle industry with their broad user base and strong practicality. In response to the life of power lead-acid batteries, many companies in the industry are exploring in depth, striving to control the quality of the plates by optimizing the production process, thereby extending the battery life.

[0003] The negative electrode plate of a lead-acid battery is mainly made of lead or lead alloy, which is prone to electrochemical corrosion in sulfuric acid electrolyte. In particular, during the battery charging and discharging process, the negative electrode plate releases electrons, causing the coating or substrate of the negative terminal to be oxidized, and then corroded. This corrosion phenomenon may manifest as terminal discoloration, coating peeling or even complete breakage, which seriously affects the performance and service life of the battery. In order to improve the corrosion resistance of the negative electrode plate, some measures have been taken in the prior art. For example, alloy materials with better corrosion resistance are used as negative electrode plates; surface treatment of negative electrode plates is performed, such as electroplating corrosion-resistant coatings; battery design is optimized to reduce overflow and leakage of sulfuric acid electrolyte. However, these measures cannot completely prevent the occurrence of corrosion, especially in harsh use environments, the corrosion resistance of negative electrode plates is still a prominent problem. Therefore, it is necessary to continue to research and develop new materials and processes to improve their corrosion resistance, so as to extend the service life of the battery and improve its performance stability. Summary of the invention

[0004] In order to solve the problem that the existing technical measures in the background technology cannot completely prevent the occurrence of corrosion, especially in harsh usage environments, the corrosion resistance of negative electrode plates is still a prominent problem, the purpose of the present invention is to provide a negative electrode grid and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a negative electrode grid, comprising a lead grid blank and a lead paste covering the surface of the lead grid blank, wherein the lead paste is made of the following raw materials in parts by weight: 90-100 parts of lead powder, 120-125 parts of deionized water, 1-3 parts of cationic polyacrylamide, 2-3 parts of graphene, 2-4 parts of activated carbon, 90-95 parts of concentrated sulfuric acid, 0.8-1 parts of bamboo charcoal fiber, 3-4 parts of modified silica, and 1-2 parts of sodium sulfate; wherein the modified silica is silica grafted with hyperbranched polysilane.

[0007] The combination of graphene powder and activated carbon powder can improve the conductivity of the negative electrode lead paste, increase specific energy and improve large current discharge capability, thereby extending the service life of power lead-acid batteries.

[0008] Furthermore, the fiber length of the bamboo charcoal fiber is 3-5 mm.

[0009] Furthermore, the concentrated sulfuric acid is 2.1 g / cm 3 .

[0010] Furthermore, the preparation method of the modified silicon dioxide is:

[0011] Add silica, acetic acid aqueous solution and anhydrous ethanol into a flask, and after ultrasonic dispersion for 1 hour, control the temperature at 70-75°C, add hyperbranched silane monomer, keep the temperature for reaction for 24 hours, filter, wash and vacuum dry to obtain modified silica.

[0012] The mass ratio of silicon dioxide, acetic acid aqueous solution, anhydrous ethanol and hyperbranched silane monomer is 0.2:1:(7-8):2; the hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate in a mass ratio of 1:(0.2-0.6):(0.4-0.8), and the mass fraction of the acetic acid aqueous solution is 65-70%.

[0013] As an additive for the negative electrode lead paste of lead-acid batteries, silicon dioxide can improve the performance of batteries from multiple perspectives, including improving pore structure, enhancing mechanical strength, inhibiting hydrogen evolution reaction, improving low temperature performance and cycle life, etc. These effects together improve the overall performance and service life of lead-acid batteries.

[0014] However, the surface energy of silica particles is relatively high, especially when the particle size reaches the nanometer level. The high surface energy makes the particles tend to gather together to reduce the surface energy, thereby reaching a more stable state. In this regard, the present invention utilizes an acid-catalyzed hydrolysis method to graft hyperbranched polysilane onto the surface of silica, and its mechanism of action is: the methoxyl group in the hyperbranched silane monomer undergoes a hydrolysis reaction to produce silanol, which is then bonded to the hydroxyl group on the silica surface through hydrogen bonds, and finally dehydrated and condensed. The remaining hydroxyl groups on the silanol are dehydrated and condensed with the silanol produced by the hydrolysis of the hyperbranched silane monomer, and the dehydration and condensation reaction is repeated to finally form a modified silica containing a hyperbranched polysilane structure.

[0015] In a second aspect, the present invention further provides a method for preparing a negative electrode grid, comprising the following steps:

[0016] Step A1: cationic polyacrylamide, graphene, activated carbon, bamboo charcoal fiber, modified silicon dioxide, and sodium sulfate are placed in a batching kettle according to the formula, stirred at a speed of 1500 r / min for 30 minutes to obtain a mixed powder, which is taken out, lead powder is added to the mixed powder, stirred for 10-20 minutes, then deionized water is added to the above system, stirred for 10-20 minutes, and finally concentrated sulfuric acid is added. During the acid addition process, the system temperature is controlled between 30-40° C., and the whole process is continuously stirred for 20-30 minutes to obtain a lead paste;

[0017] Step A2: Apply lead paste to the lead grid blank, dry and solidify it to obtain a negative electrode grid.

[0018] Furthermore, in step A2, the drying and curing temperature is 50° C. and the time is 24-48 hours.

[0019] Beneficial effects of the present invention:

[0020] The present invention adds modified silicon dioxide to the raw materials for preparing the lead paste, and the modified silicon dioxide is silicon dioxide grafted with hyperbranched polysilane. The molecular structure of the hyperbranched polysilane is large and complex. When grafted to the surface of silicon dioxide, a certain steric hindrance is formed between the particles. This steric hindrance can effectively prevent the silicon dioxide particles from approaching and agglomerating each other, thereby improving its dispersibility, improving the conductivity and service life of the negative electrode lead paste, and further improving the comprehensive performance of the negative electrode grid prepared by the negative electrode lead paste. In addition, the hyperbranched polysilane molecular structure has an SiO bond, which has a high bond energy and can remain stable at low temperatures, thereby improving the low temperature resistance of the battery prepared by the negative electrode grid of the present invention.

[0021] In addition, the hyperbranched polysilane is obtained by hydrolysis and condensation of γ-glycidyloxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate. γ-glycidyloxypropyltrimethoxysilane can make the surface of modified silica carry epoxy groups, which can react with carboxyl groups on the surface of raw materials such as graphene, activated carbon, and bamboo charcoal fiber, thereby making silica more evenly dispersed in the lead paste raw materials, giving full play to the conductivity and other properties of silica, and improving the comprehensive performance of the negative electrode grid. Heptadecafluorodecyltrimethoxysilane contains fluoroalkyl chains, which have significant chemical stability and can effectively resist the erosion of chemical substances such as strong acids, strong bases and solvents, and can improve the corrosion resistance of the negative electrode grid. The fluoroalkyl chain is a hydrophobic group, which is not conducive to the dispersion of modified nano-silica. However, 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate contains hydrophilic groups, which can make the modified nano-silica improve the corrosion resistance of the grid while having good dispersibility in water, and can further increase the corrosion resistance, conductivity and cycle performance of the negative electrode grid. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1

[0024] A negative electrode grid, comprising a lead grid blank and a lead paste covering the surface of the lead grid blank, wherein the lead paste is made of the following raw materials in parts by weight: 90 parts of lead powder, 120 parts of deionized water, 1 part of cationic polyacrylamide, 2 parts of graphene, 2 parts of activated carbon, 90 parts of concentrated sulfuric acid, 0.8 parts of bamboo charcoal fiber, 3 parts of modified silicon dioxide, and 1 part of sodium sulfate. The fiber length of the bamboo charcoal fiber is 4 mm; the concentrated sulfuric acid is 2.1 g / cm 3 .

[0025] The preparation method of modified silicon dioxide is:

[0026] Add silica, 65% acetic acid aqueous solution and anhydrous ethanol to a flask, ultrasonically disperse for 1 hour, control the temperature at 70°C, add hyperbranched silane monomer, keep warm for 24 hours, filter, wash, and vacuum dry to obtain modified silica. The mass ratio of silica, acetic acid aqueous solution, anhydrous ethanol, and hyperbranched silane monomer is 0.2:1:7:2; the hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate in a mass ratio of 1:0.2:0.8.

[0027] The method for preparing a negative electrode grid comprises the following steps:

[0028] Step A1: cationic polyacrylamide, graphene, activated carbon, bamboo charcoal fiber, modified silicon dioxide, and sodium sulfate are placed in a batching kettle according to the formula, stirred at a speed of 1500 r / min for 30 minutes to obtain a mixed powder, which is taken out, lead powder is added to the mixed powder, stirred for 10 minutes, then deionized water is added to the above system, stirred for 10 minutes, and finally concentrated sulfuric acid is added. During the acid addition process, the system temperature is controlled at 30° C. The whole process is continuously stirred for 20 minutes to obtain a lead paste;

[0029] Step A2: Apply lead paste to the lead grid blank, dry and solidify it at 50°C for 24 hours to obtain a negative electrode grid.

[0030] Example 2

[0031] A negative electrode grid, comprising a lead grid blank and a lead paste covering the surface of the lead grid blank, wherein the lead paste is made of the following raw materials in parts by weight: 95 parts of lead powder, 122.5 parts of deionized water, 2 parts of cationic polyacrylamide, 2.5 parts of graphene, 3 parts of activated carbon, 92.5 parts of concentrated sulfuric acid, 0.9 parts of bamboo charcoal fiber, 3.5 parts of modified silicon dioxide, and 1.5 parts of sodium sulfate. The fiber length of the bamboo charcoal fiber is 4 mm; the concentrated sulfuric acid is 2.1 g / cm 3 .

[0032] The preparation method of modified silicon dioxide is:

[0033] Add silica, 70% acetic acid aqueous solution and anhydrous ethanol to a flask, ultrasonically disperse for 1 hour, control the temperature at 70°C, add hyperbranched silane monomer, keep warm for 24 hours, filter, wash, and vacuum dry to obtain modified silica. The mass ratio of silica, acetic acid aqueous solution, anhydrous ethanol, and hyperbranched silane monomer is 0.2:1:8:2; the hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate in a mass ratio of 1:0.4:0.6.

[0034] The method for preparing a negative electrode grid comprises the following steps:

[0035] Step A1: cationic polyacrylamide, graphene, activated carbon, bamboo charcoal fiber, modified silicon dioxide, and sodium sulfate are placed in a batching kettle according to the formula, stirred at a speed of 1500 r / min for 30 minutes to obtain a mixed powder, which is taken out, lead powder is added to the mixed powder, stirred for 15 minutes, then deionized water is added to the above system, stirred for 15 minutes, and finally concentrated sulfuric acid is added. During the acid addition process, the system temperature is controlled at 40° C. The whole process is continuously stirred for 25 minutes to obtain a lead paste;

[0036] Step A2: Apply lead paste to the lead grid blank, dry and solidify it at 50° C. for 48 hours to obtain a negative electrode grid.

[0037] Example 3

[0038] A negative electrode grid, comprising a lead grid blank and a lead paste covering the surface of the lead grid blank, wherein the lead paste is made of the following raw materials in parts by weight: 100 parts of lead powder, 25 parts of deionized water, 3 parts of cationic polyacrylamide, 3 parts of graphene, 4 parts of activated carbon, 95 parts of concentrated sulfuric acid, 1 part of bamboo charcoal fiber, 4 parts of modified silicon dioxide, and 2 parts of sodium sulfate. The fiber length of the bamboo charcoal fiber is 4 mm; the concentrated sulfuric acid is 2.1 g / cm 3 .

[0039] The preparation method of modified silicon dioxide is:

[0040] Add silica, 70% acetic acid aqueous solution and anhydrous ethanol to a flask, ultrasonically disperse for 1 hour, control the temperature to 75°C, add hyperbranched silane monomer, keep warm for 24 hours, filter, wash, and vacuum dry to obtain modified silica. The mass ratio of silica, acetic acid aqueous solution, anhydrous ethanol, and hyperbranched silane monomer is 0.2:1:8:2; the hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate in a mass ratio of 1:0.5:0.5.

[0041] The method for preparing a negative electrode grid comprises the following steps:

[0042] Step A1: cationic polyacrylamide, graphene, activated carbon, bamboo charcoal fiber, modified silicon dioxide, and sodium sulfate are placed in a batching kettle according to the formula, stirred at a speed of 1500 r / min for 30 minutes to obtain a mixed powder, which is taken out, lead powder is added to the mixed powder, stirred for 20 minutes, then deionized water is added to the above system, stirred for 20 minutes, and finally concentrated sulfuric acid is added. During the acid addition process, the system temperature is controlled at 35° C., and the whole process is continuously stirred for 30 minutes to obtain a lead paste;

[0043] Step A2: Apply lead paste to the lead grid blank, dry and solidify it at 50° C. for 48 hours to obtain a negative electrode grid.

[0044] Example 4

[0045] Compared with Example 1, this embodiment is different in that:

[0046] The modified silicon dioxide in Example 1 was replaced with 2.5 parts, and the remaining raw materials and steps were the same as in Example 1.

[0047] Example 5

[0048] Compared with Example 3, this embodiment is different in that:

[0049] The modified silicon dioxide in Example 3 was replaced with 4.5 parts, and the remaining raw materials and steps were the same as in Example 3.

[0050] Comparative Example 1

[0051] Compared with Example 1, this comparative example is different in that:

[0052] The hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane in a mass ratio of 1:1. The remaining raw materials and steps are the same as in Example 1.

[0053] Comparative Example 2

[0054] Compared with Example 1, this comparative example is different in that:

[0055] The hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate in a mass ratio of 1:1, and the remaining raw materials and steps are the same as in Example 1.

[0056] Comparative Example 3

[0057] Compared with Example 1, this comparative example is different in that:

[0058] The hyperbranched monomer is γ-glycidyloxypropyltrimethoxysilane, and the other raw materials and steps are the same as in Example 1.

[0059] Comparative Example 4

[0060] Compared with Example 1, this comparative example is different in that:

[0061] Add silicon dioxide, 65% acetic acid aqueous solution and anhydrous ethanol into a flask, and after ultrasonic dispersion for 1 hour, control the temperature at 70°C, add γ-glycidyloxypropyltrimethoxysilane, keep the temperature for 24 hours, filter, wash, and vacuum dry to obtain modified silicon dioxide. The mass ratio of silicon dioxide, acetic acid aqueous solution, anhydrous ethanol, and γ-glycidyloxypropyltrimethoxysilane is 0.2:1:7:0.04.

[0062] The remaining materials and steps are the same as in Example 1.

[0063] Comparative Example 5

[0064] Compared with Example 1, this comparative example is different in that:

[0065] The modified silica was replaced by silica, and the remaining raw materials and steps were the same as in Example 1.

[0066] Performance tests were performed on Examples 1 to 5 and Comparative Examples 1 to 5. The test items are as follows, and the results are shown in Table 1:

[0067] 1. Conductivity, low temperature resistance and cycle performance tests: The negative electrode grids of Examples 1 to 5 and Comparative Examples 1 to 5 were assembled into power-type lead-acid batteries, and performance tests were performed on them.

[0068] II. Corrosion resistance test: The power lead-acid batteries assembled with the negative grids of Examples 1 to 5 and Comparative Examples 1 to 5 were placed in a 60°C water bath and connected in series for a corrosion test with constant current charging. A constant current polarization test was performed using a μC-XCF08 charge and discharge tester, and the apparent corrosion current density of the corroded grid was 2.3 mA·cm-2 , the constant current corrosion time is 300h. After the grid corrosion is completed, the corrosion products on the grid surface are removed by soaking in sugar-alkali solution. The corroded grid is washed with deionized water, vacuum dried and weighed (m 2 ), by calculating the weight loss of the grid before and after electrochemical corrosion (m 1 -m 2 ), and then calculate the average corrosion rate of the grid.

[0069] Table 1

[0070]

[0071] It can be seen from Table 1 that the comprehensive performance of the batteries prepared by the negative electrode grids of Examples 1 to 5 is better than the comprehensive performance of the batteries prepared by the negative electrode grids of Comparative Examples 1 to 5. It can be seen from the results of Example 4 and Example 5 that too much or too little modified silicon dioxide will affect the comprehensive performance of the battery; Comparative Example 1 does not contain 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate, and its dispersibility is poorer than that of Example 1, and the comprehensive performance is reduced; Comparative Example 2 does not contain heptadecafluorodecyltrimethoxysilane, and its corrosion resistance is reduced; Comparative Example 3 does not contain 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate and heptadecafluorodecyltrimethoxysilane, and its corrosion resistance and conductivity and other properties are reduced; Comparative Example 4 does not contain a hyperbranched structure, the modified silicon dioxide has poor dispersibility, and the comprehensive performance of the battery is poor; Comparative Example 5 does not use modified silicon dioxide, its dispersibility is the worst, and the comprehensive performance of the battery is also relatively the worst.

[0072] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0073] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A negative electrode grid, characterized in that: The negative electrode grid comprises a lead grid body and a lead paste covering the surface of the lead grid body, wherein the lead paste is made of the following raw materials in parts by weight: 90-100 parts of lead powder, 120-125 parts of deionized water, 1-3 parts of cationic polyacrylamide, 2-3 parts of graphene, 2-4 parts of activated carbon, 90-95 parts of concentrated sulfuric acid, 0.8-1 parts of bamboo charcoal fiber, 3-4 parts of modified silicon dioxide, and 1-2 parts of sodium sulfate; wherein the modified silicon dioxide is silicon dioxide grafted with hyperbranched polysilane.

2. A negative electrode grid according to claim 1, characterized in that: The fiber length of the bamboo charcoal fiber is 3-5 mm.

3. A negative electrode grid according to claim 1, characterized in that: The concentrated sulfuric acid is 2.1 g / cm 3 .

4. A negative electrode grid according to claim 1, characterized in that: The preparation method of the modified silicon dioxide is: Add silica, acetic acid aqueous solution and anhydrous ethanol into a flask, and after ultrasonic dispersion for 1 hour, control the temperature at 70-75°C, add hyperbranched silane monomer, keep the temperature for reaction for 24 hours, filter, wash and vacuum dry to obtain modified silica.

5. A negative electrode grid according to claim 4, characterized in that: The mass ratio of silicon dioxide, acetic acid aqueous solution, anhydrous ethanol and hyperbranched silane monomer is 0.2:1:(7-8):

2.

6. A negative electrode grid according to claim 4, characterized in that: The hyperbranched silane monomer is composed of γ-glycidyloxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane and 3-{[dimethyl(3-trimethoxysilyl)propyl]ammonium}-propane-1-sulfonate in a mass ratio of 1:(0.2-0.6):(0.4-0.8).

7. A negative electrode grid according to claim 4, characterized in that: The mass fraction of the acetic acid aqueous solution is 65-70%.

8. A method for preparing a corrosion-resistant lead-acid battery plate according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step A1: cationic polyacrylamide, graphene, activated carbon, bamboo charcoal fiber, modified silicon dioxide, and sodium sulfate are placed in a batching kettle according to the formula, stirred at a speed of 1500 r / min for 30 minutes to obtain a mixed powder, which is taken out, lead powder is added to the mixed powder, stirred for 10-20 minutes, then deionized water is added to the above system, stirred for 10-20 minutes, and finally concentrated sulfuric acid is added to obtain lead paste; Step A2: Apply lead paste to the lead grid blank, dry and solidify it to obtain a negative electrode grid.

9. The method for preparing a corrosion-resistant lead-acid battery plate according to claim 8, characterized in that: In step A1, the system temperature is controlled between 30-40° C. during the acid addition process, and stirring is continued for 20-30 min throughout the process.

10. The method for preparing a corrosion-resistant lead-acid battery plate according to claim 8, characterized in that: In step A2, the drying and curing temperature is 50° C. and the time is 24-48 hours.

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