Lead paste formulation and method for improving utilization of active material in lead-acid batteries

Abstract

The title of the present application is lead paste formula and preparation method for improving utilization rate of active material of lead-acid battery. It belongs to the technical field of lead-acid battery. It mainly solves the problem that the low-temperature performance and discharge performance of the battery will decrease when the utilization rate of negative active material is improved. Its main features are: the formula of the negative lead paste is as follows in terms of weight fraction: lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 45-60 parts, short fiber 0.12-0.2 parts, lignin 0.5-0.8 parts, carbon black 0.3-0.5 parts, carbon nanotube 0.3-0.5 parts, and barium sulfate 0.8-1 part. The negative lead paste has the characteristics of high water content, high porosity, improved conductive network of the negative lead paste, and the ability to improve the utilization rate of negative active material while ensuring the good low-temperature performance of the starting lead-acid battery, and is mainly used for improving the utilization rate of negative active material of the starting lead-acid battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lead-acid storage batteries, and particularly relates to a lead paste formula for improving the utilization rate of active substances of a lead-acid storage battery and a preparation method thereof. BACKGROUND

[0002] Chinese patent CN 117855406 A discloses a conductive polymer / acetylene black composite material for lead-acid battery negative electrode, a lead-acid battery negative electrode, a lead-acid battery and a related preparation method: the conductive polymer / acetylene black composite material is formed by growing a conductive polymer on the surface of acetylene black through in-situ polymerization, and the conductive polymer / acetylene black composite material presents a form of conductive polymer coating acetylene black particles, the acetylene black particles are spherical structures, and the conductive polymer fibers can be clearly observed in the SEM image. The conductive polymer is polyaniline and / or polypyrrole. The acetylene black is modified by using the conductive polymer material such as polyaniline, which can effectively improve the hydrogen evolution overpotential of the acetylene black, thereby improving the electrochemical performance of the lead-acid battery. When used as a negative electrode additive of the lead-acid battery, the conductive polymer / acetylene black composite material can effectively improve the discharge specific capacity and cycle life of the lead-acid battery.

[0003] Chinese patent CN 114335537 B discloses a polypyrrole-coated conductive carbon black / indium oxide composite material, a preparation method and application thereof: the composite material has a core-shell structure, the shell material is polypyrrole, the core material is conductive carbon black and indium oxide, the chemical formula of the composite material is [PPy@(C / In2O3)], and the mass ratio of the conductive carbon black, polypyrrole and indium oxide is (5-40):(2-8):1. The polypyrrole-coated conductive carbon black / indium oxide composite material, as a negative electrode additive of a lead-acid battery, can construct a hydrophilic three-dimensional ion transport network structure in the negative electrode, effectively improve the "sulfation" phenomenon of the lead-acid battery negative electrode, and improve the cycle life of the lead-acid battery in a high-rate partial state of charge.

[0004] Chinese patent CN 115911379 A discloses a graphene battery negative electrode material and a preparation method thereof: including the following steps: adding an auxiliary agent and alkyl siloxane into a polytetrafluoroethylene emulsion, stirring to obtain a binder; adding three-dimensional graphene, barium sulfate, an organic additive and lead powder into an ethanol aqueous solution, stirring, then adding the binder, continuing to stir to obtain a slurry, spray drying to obtain a powder; dispersing fibers in deionized water to obtain a dispersion liquid, adding the dispersion liquid and the powder into a paste mixing machine, stirring, then adding a 45-51wt% sulfuric acid solution, continuing to stir to obtain a lead paste; coating the lead paste on a lead-acid battery grid, drying to obtain the graphene battery negative electrode material; selecting three-dimensional graphene as a conductive agent, combining with the self-made binder to realize the close combination and uniform distribution of active substances and carbon powder, and to endow the negative electrode material with excellent mechanical properties and electrochemical properties.

[0005] The above-mentioned patent uses polyaniline, polypyrrole, polytetrafluoroethylene, etc. to form a framework of high-conductivity carbon material and form a chain-like conductive network. However, the conductive performance of polyaniline, polypyrrole, polytetrafluoroethylene, etc. is far lower than that of carbon material, which greatly reduces the improvement effect.

[0006] When the negative active material (or negative paste amount) in the battery is limited, if the utilization rate of the negative active material is to be improved (the negative paste amount is to be reduced), the low-temperature performance and discharge performance of the battery will decrease. SUMMARY

[0007] The purpose of the present application is to provide a negative lead paste and a preparation method thereof, which can improve the utilization rate of negative active material and ensure good low-temperature performance of a lead-acid storage battery.

[0008] The technical solution of the lead paste formula of the present application is: a lead paste formula for improving the utilization rate of active material of a lead-acid storage battery, which is used to improve the utilization rate of negative active material of a starting lead-acid storage battery, and is characterized in that the formula of the negative lead paste comprises, by weight: 100 parts of lead powder, 45-60 parts of a dilute sulfuric acid solution with a concentration of 1.15 g / ml-1.20 g / ml, 0.12-0.2 parts of short fibers, 0.5-0.8 parts of lignin, 0.3-0.5 parts of carbon black, 0.3-0.5 parts of carbon nanotubes, and 0.8-1 parts of barium sulfate.

[0009] In the technical solution of the lead paste formula of the present application, the lead powder is lead powder with an oxidation degree of 75%.

[0010] In the technical solution of the lead paste formula of the present application, the formula of the negative lead paste comprises, by weight: 100 parts of lead powder, 50-60 parts of a dilute sulfuric acid solution with a concentration of 1.15 g / ml-1.20 g / ml, 0.16-0.2 parts of short fibers, 0.5-0.6 parts of lignin, 0.3-0.4 parts of carbon black, 0.3-0.4 parts of carbon nanotubes, and 0.9-1 parts of barium sulfate.

[0011] In the technical solution of the lead paste formula of the present application, the formula of the negative lead paste comprises, by weight: 100 parts of lead powder, 60 parts of a dilute sulfuric acid solution with a concentration of 1.15 g / ml-1.20 g / ml, 0.2 parts of short fibers, 0.5 parts of lignin, 0.3 parts of carbon black, 0.3 parts of carbon nanotubes, and 1 part of barium sulfate.

[0012] In the technical solution of the lead paste formula of the present application, the formula of the negative lead paste comprises, by weight: 100 parts of lead powder, 45-50 parts of a dilute sulfuric acid solution with a concentration of 1.15 g / ml-1.20 g / ml, 0.12-0.16 parts of short fibers, 0.6-0.8 parts of lignin, 0.4-0.5 parts of carbon black, 0.4-0.5 parts of carbon nanotubes, and 0.8-0.9 parts of barium sulfate.

[0013] The negative lead paste formula in the technical solution of the lead paste formula of the application is as follows in terms of weight fraction: lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 45 parts, short fiber 0.12 part, lignin 0.8 part, carbon black 0.5 part, carbon nanotube 0.5 part, and barium sulfate 0.8 part.

[0014] The negative lead paste formula in the technical solution of the lead paste formula of the application is as follows in terms of weight fraction: lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 52-58 parts, short fiber 0.17-0.19 part, lignin 0.5-0.6 part, carbon black 0.3-0.4 part, carbon nanotube 0.3-0.4 part, and barium sulfate 0.9-1 part.

[0015] The mass ratio of the 1.15g / ml-1.20g / ml dilute sulfuric acid solution to the lead powder in the technical solution of the lead paste formula of the application is 12.5%-13.5%; the apparent density of the negative lead paste after the paste ends is 3.60g / ml-3.80g / ml; and the water content of the negative lead paste is 14.5%-17.0%.

[0016] The basic particle size of the carbon black in the technical solution of the lead paste formula of the application is between 30nm and 300nm, the OAN oil absorption value is between 80ml / 100g and 120ml / 100g, and the nitrogen adsorption specific surface area is between 70m 2 / g and 90m 2 / g; the diameter of the carbon nanotube is between 20nm and 100nm, and the length is between 10um and 50um.

[0017] The lignin in the technical solution of the lead paste formula of the application is single lignin or multiple lignins; and the solubility of at least one lignin in the single lignin or multiple lignins in a 1.29g / ml dilute sulfuric acid solution at 25℃ is not more than 300mg / L.

[0018] The technical solution of the preparation method is: a lead paste preparation method for improving utilization rate of active material of lead-acid storage battery, characterized by the following negative electrode and paste process: short fibers, lignin, carbon black, carbon nanotubes and barium sulfate are put into a mixing and pasting machine, then about 30% of dilute sulfuric acid is added into the mixing and pasting machine within 2 minutes, the mixing and pasting machine is started to stir while the dilute sulfuric acid is being added, then lead powder is added into the mixing and pasting machine within 2 minutes, the stirring is continued, after the lead powder is added completely, the remaining about 70% of 1.15-1.25 g / ml dilute sulfuric acid solution is added, the time for adding the dilute sulfuric acid is controlled to be about 15-20 minutes, the mixing and pasting machine is started to be vacuumized during the process of adding the dilute sulfuric acid for the second time, the temperature inside the mixing and pasting machine is controlled to be not more than 60 DEG C, after the adding of the acid is completed, the vacuumizing is stopped, the inside of the mixing and pasting machine is returned to normal pressure, and the lead paste is continuously stirred for about 3-5 minutes, and the mixing and pasting is completed.

[0019] The traditional carbon material is in a spherical particle structure, and exists in a point distribution state in the negative electrode lead paste after mixing and pasting, which is not conducive to forming a coherent conductive network, while the carbon nanotube slurry as the negative electrode additive is conducive to forming a carbon chain structure and enhancing the conductivity between the negative electrode materials. Meanwhile, compared with the traditional spherical particle structure carbon material, the addition of the carbon nanotube has a smaller influence on the increased hydrogen evolution of the negative electrode. On the other hand, increasing the addition amount of lignin can inhibit the hydrogen evolution of the negative electrode while ensuring the low temperature performance.

[0020] In the prior art, the mass ratio of sulfuric acid to lead powder in the lead paste of the starting lead-acid storage battery is generally within 3.5%-7%, and even the research data in the literature is not more than 12%. The mass ratio of sulfuric acid to lead powder in the lead paste of the present application is generally 12.5%-13%.

[0021] In the prior art, the sulfuric acid added in the lead paste process of the starting lead-acid storage battery is generally with a density of 1.35 g / ml-1.40 g / ml, and the dilute sulfuric acid solution with a density of 1.15 g / ml-1.20 g / ml is used in the present application.

[0022] In the prior art, the lead paste preparation process of the starting lead-acid storage battery is generally: adding auxiliary materials, adding pure water, adding lead powder, adding dilute sulfuric acid, continuously stirring, and completing the mixing and pasting. The lead paste preparation process of the present application is: adding auxiliary materials, adding about 30% of dilute sulfuric acid, adding lead powder, adding the remaining about 70% of dilute sulfuric acid, continuously stirring, and completing the mixing and pasting.

[0023] The beneficial effects of the present application are:

[0024] The application greatly increases the sulfuric acid addition amount of negative lead paste and preparation time, prepares high water content and high porosity negative lead paste, uses carbon nanotubes to improve the conductive network of negative lead paste and the effective connection between negative active materials, and can partially offset the influence of the conductive network deterioration caused by the shrinkage of negative active materials after the battery is charged. The application can ensure the good low temperature performance of the starting lead-acid storage battery while realizing the improvement of the utilization rate of negative active materials.

[0025] The application is mainly used for improving the utilization rate of negative active materials of the starting lead-acid storage battery. DETAILED DESCRIPTION

[0026] The following is a further detailed description of the embodiments of the application.

[0027] The application is a lead paste formula for improving the utilization rate of active materials of lead-acid storage battery, which is used for improving the utilization rate of negative active materials of the starting lead-acid storage battery. The formula of the negative lead paste is as follows in terms of weight fraction: lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 45-60 parts, short fiber 0.12-0.2 parts, lignin 0.5-0.8 parts, carbon black 0.3-0.5 parts, carbon nanotube 0.3-0.5 parts, and barium sulfate 0.8-1 part.

[0028] The optimized formula of the negative lead paste is as follows in terms of weight fraction: lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 50-60 parts, short fiber 0.16-0.2 parts, lignin 0.5-0.6 parts, carbon black 0.3-0.4 parts, carbon nanotube 0.3-0.4 parts, and barium sulfate 0.9-1 part; or lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 52-58 parts, short fiber 0.17-0.19 parts, lignin 0.5-0.6 parts, carbon black 0.3-0.4 parts, carbon nanotube 0.3-0.4 parts, and barium sulfate 0.9-1 part; or lead powder 100 parts, 1.15g / ml-1.20g / ml dilute sulfuric acid solution 45-50 parts, short fiber 0.12-0.16 parts, lignin 0.6-0.8 parts, carbon black 0.4-0.5 parts, carbon nanotube 0.4-0.5 parts, and barium sulfate 0.8-0.9 part.

[0029] The mass ratio of the 1.15g / ml-1.20g / ml dilute sulfuric acid solution to the lead powder is 12.5%-13.5%; the apparent density of the negative lead paste and the negative lead paste after the paste is finished is 3.60g / ml-3.80g / ml; the water content of the negative lead paste is 14.5%-17.0%; the basic particle size of the carbon black is between 30nm and 300nm, the OAN oil absorption value is between 80ml / 100g and 120ml / 100g, the nitrogen adsorption specific surface area is between 70m 2 / g and 90m2 The diameter of the carbon nanotube is 20-100 nm, and the length is 10-50 um; the lignin is single lignin or multiple lignins; the solubility of at least one of the single lignin or multiple lignins in a 1.29 g / ml dilute sulfuric acid solution at 25 DEG C is not more than 300 mg / L.

[0030] The application discloses a preparation method of lead paste for improving utilization rate of negative active material of a starting lead-acid storage battery, and the negative electrode and paste process are as follows: short fibers, lignin, carbon black, carbon nanotubes and barium sulfate are put into a mixing and pasting machine, then about 30% of dilute sulfuric acid is added into the mixing and pasting machine within 2 minutes, the mixing and pasting machine is started to stir while the dilute sulfuric acid is being added, then lead powder is added into the mixing and pasting machine within 2 minutes, the stirring is continued, after the lead powder is added completely, the remaining about 70% of 1.15-1.25 g / ml dilute sulfuric acid solution is added, the time for adding the dilute sulfuric acid is controlled to be about 15-20 minutes, the mixing and pasting machine is started to be vacuumized in the process of adding the dilute sulfuric acid for the second time, and the temperature in the mixing and pasting machine is controlled to be not more than 60 DEG C; after the adding of the acid is completed, the vacuumization is stopped, the inside of the mixing and pasting machine is returned to normal pressure, and the lead paste is continuously stirred for about 3-5 minutes, and the mixing and pasting is completed.

[0031] Example 1

[0032] The negative lead paste formula material is as follows: 100 kg of lead powder with an oxidation degree of 75%, 60 kg of dilute sulfuric acid solution with a density of 1.15 g / ml, 0.2 kg of short fibers, 0.5 kg of lignin, 0.3 kg of carbon black, 0.3 kg of carbon nanotubes and 1 kg of barium sulfate.

[0033] The negative lead paste and pasting process are as follows: the short fibers, lignin, carbon black, carbon nanotubes and barium sulfate are put into a mixing and pasting machine, then 20 kg of dilute sulfuric acid is added into the mixing and pasting machine within 2 minutes, the mixing and pasting machine is started to stir while the dilute sulfuric acid is being added, then 100 kg of lead powder is added into the mixing and pasting machine within 2 minutes, the stirring is continued, after the lead powder is added completely, the remaining 40 kg of 1.15 g / ml dilute sulfuric acid solution is added, the time for adding the dilute sulfuric acid is controlled to be 20 minutes, the mixing and pasting machine is started to be vacuumized in the process of adding the dilute sulfuric acid for the second time, and the temperature in the mixing and pasting machine is controlled to be not more than 55 DEG C; after the adding of the acid is completed, the vacuumization is stopped, the inside of the mixing and pasting machine is returned to normal pressure, and the lead paste is continuously stirred for 3 minutes, and the mixing and pasting is completed. The apparent density of the lead paste is measured to be 3.65 g / ml, and the water content of the lead paste is measured to be 16.8%.

[0034] Example 2

[0035] The negative lead paste formula material is as follows: 100 kg of lead powder with an oxidation degree of 75%, 45 kg of dilute sulfuric acid solution with a density of 1.20 g / ml, 0.12 kg of short fibers, 0.8 kg of lignin, 0.5 kg of carbon black, 0.5 kg of carbon nanotubes and 0.8 kg of barium sulfate.

[0036] The negative lead paste and paste process: first put the short fibers, lignin, carbon black, carbon nanotubes and barium sulfate into the paste machine, then add 15 kg of dilute sulfuric acid into the paste machine within 2 min, start the stirring function of the paste machine while adding the dilute sulfuric acid, then add 100 kg of lead powder into the paste machine within 2 min, continue stirring, after the lead powder is added, start to add the remaining 30 kg of 1.20 g / ml dilute sulfuric acid solution, the time for adding the dilute sulfuric acid is 15 min, during the second time of adding the dilute sulfuric acid, the paste machine is started to be vacuumized, the internal temperature of the paste machine is 60°C at most; after the acid addition is completed, stop vacuumizing, the internal pressure of the paste machine is restored to normal, continue stirring the lead paste for 5 min, and the pasting is completed. The apparent density of the measured lead paste is 3.78 g / ml, and the water content of the measured lead paste is 14.6%.

[0037] Comparative Example (current)

[0038] The negative lead paste formula material: lead powder with an oxidation degree of 75% 100 kg, dilute sulfuric acid solution with a density of 1.38 g / ml 10 kg, pure water 12 kg, short fibers 0.08 kg, lignin 0.3 kg, carbon black 0.3 kg, barium sulfate 0.8 kg.

[0039] The negative lead paste and paste process: first put the short fibers, lignin, carbon black, barium sulfate into the paste machine, then add 11 kg of pure water into the paste machine within 2 min, start the stirring function of the paste machine while adding the pure water, then add 100 kg of lead powder into the paste machine within 2 min, continue stirring, after the lead powder is added, start to add 10 kg of 1.38 g / ml dilute sulfuric acid solution, the time for adding the dilute sulfuric acid is 15 min, during the process of adding the dilute sulfuric acid, the paste machine is started to be vacuumized, the internal temperature of the paste machine is 60°C at most; after the acid addition is completed, stop vacuumizing, the internal pressure of the paste machine is restored to normal, continue stirring the lead paste for 5 min, and the pasting is completed. The apparent density of the measured lead paste is 4.35 g / ml, and the water content of the measured lead paste is 11.8%.

[0040] The mass ratio of sulfuric acid to lead oxide in the negative lead paste formula of Example 1 and Example 2 is about 13%, and the mass ratio of sulfuric acid to lead oxide in the negative lead paste formula of the comparative example is about 5%.

[0041] The negative lead paste prepared in Example 1, Example 2 and the comparative example is coated on the plate according to the paste coating amount of 95 g / piece, and the current conventional positive plate (paste coating amount of 100 g / piece) is prepared into a 100 Ah SLI battery according to the electrode group structure of 9 pieces of positive plate and 8 pieces of negative plate, and the C20 capacity and Cre capacity (reserve capacity) of the battery are tested according to “GBT 5008.1-2023 Starting Lead-acid Storage Batteries Part 1 Technical Conditions and Test Methods”.

[0042] The capacity test data is shown in the following table:

[0043]

[0044] The C20 capacity and Cre capacity (reserve capacity) of Example 1 and Example 2 are improved compared with the comparative example, and the improvement of the Cre capacity (reserve capacity) is particularly obvious. The first Cre capacity of Example 1 is improved by about 8% compared with the comparative example, and the first Cre capacity of Example 2 is improved by about 13.6% compared with the comparative example.

[0045] The above examples introduce in detail the lead paste formula and the preparation method thereof for improving the utilization rate of active material of lead-acid storage battery provided by the present application. The principles and implementation manners of the present application are described by using specific examples. The above examples are only used to help understand the method and the core idea of the present application. Meanwhile, for the general skilled in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In summary, the content of the present application should not be understood as a limitation of the present application.

Claims

1. A lead paste formula for improving the utilization rate of active materials in lead-acid batteries, used to improve the utilization rate of the negative electrode active material in starting lead-acid batteries, characterized in that... The negative electrode lead paste formula is as follows by weight: 100 parts lead powder, 45-60 parts dilute sulfuric acid solution of 1.15g / ml-1.20g / ml, 0.12-0.2 parts short fiber, 0.5-0.8 parts lignin, 0.3-0.5 parts carbon black, 0.3-0.5 parts carbon nanotubes, and 0.8-1 parts barium sulfate; the mass ratio of sulfuric acid to lead powder in the 1.15g / ml-1.20g / ml dilute sulfuric acid solution is 12.5%-13.5%.

2. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to claim 1, characterized in that: The lead powder is lead powder with an oxidation degree of 75%.

3. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to claim 1 or 2, characterized in that: The formula for negative electrode lead paste is as follows by weight: 100 parts lead powder, 50-60 parts dilute sulfuric acid solution of 1.15g / ml-1.20g / ml, 0.16-0.2 parts short fiber, 0.5-0.6 parts lignin, 0.3-0.4 parts carbon black, 0.3-0.4 parts carbon nanotubes, and 0.9-1 parts barium sulfate.

4. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to claim 3, characterized in that: The formula for negative electrode lead paste is as follows by weight: 100 parts lead powder, 60 parts dilute sulfuric acid solution of 1.15g / ml-1.20g / ml, 0.2 parts short fiber, 0.5 parts lignin, 0.3 parts carbon black, 0.3 parts carbon nanotubes, and 1 part barium sulfate.

5. The lead paste formulation for improving the utilization rate of active materials in lead-acid batteries according to claim 1 or 2, characterized in that... The formula for negative electrode lead paste is as follows by weight: 100 parts lead powder, 45-50 parts dilute sulfuric acid solution of 1.15g / ml-1.20g / ml, 0.12-0.16 parts short fiber, 0.6-0.8 parts lignin, 0.4-0.5 parts carbon black, 0.4-0.5 parts carbon nanotubes, and 0.8-0.9 parts barium sulfate.

6. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to claim 5, characterized in that: The formula for negative electrode lead paste is as follows by weight: 100 parts lead powder, 45 parts dilute sulfuric acid solution of 1.15g / ml-1.20g / ml, 0.12 parts short fiber, 0.8 parts lignin, 0.5 parts carbon black, 0.5 parts carbon nanotubes, and 0.8 parts barium sulfate.

7. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to any one of claims 1-2, 4, and 6, characterized in that: The apparent density of the negative electrode lead paste and the negative electrode lead paste after the paste is applied is 3.60 g / ml-3.80 g / ml; the moisture content of the negative electrode lead paste is 14.5%-17.0%.

8. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to any one of claims 1-2, 4, and 6, characterized in that: The carbon black has a basic particle size between 30nm and 300nm, an OAN oil absorption value of 80ml / 100g-120ml / 100g, and a nitrogen adsorption specific surface area of ​​70m2 / g-90m2 / g; the carbon nanotubes have a diameter of 20nm-100nm and a length of 10um-50um.

9. The lead paste formula for improving the utilization rate of active materials in lead-acid batteries according to any one of claims 1-2, 4, and 6, characterized in that: The lignin is a single lignin or multiple lignins; the solubility of at least one of the single lignin or multiple lignins in a 1.29 g / ml dilute sulfuric acid solution at 25°C does not exceed 300 mg / L.

10. A method for preparing lead paste according to any one of claims 1-9 to improve the utilization rate of active materials in lead-acid batteries, characterized in that: The negative electrode paste mixing process is as follows: First, short fibers, lignin, carbon black, carbon nanotubes, and barium sulfate are added to the paste mixing machine. Then, within 2 minutes, 30% of the dilute sulfuric acid is added to the paste mixing machine. While adding the dilute sulfuric acid, the mixing machine is turned on with a stirring function. Next, within 2 minutes, lead powder is added to the paste mixing machine and stirring is continued. After the lead powder is added, the remaining 70% of the 1.15-1.20 g / ml dilute sulfuric acid solution is added. The time for adding dilute sulfuric acid is controlled at 15-20 minutes. During the second addition of dilute sulfuric acid, the paste mixing machine is turned on with a vacuum to control the internal temperature of the paste mixing machine to not exceed 60℃. After the acid addition is completed, the vacuum is stopped, the internal pressure of the paste mixing machine is restored to normal, and the lead paste is stirred for another 3-5 minutes. The paste mixing process is then complete.

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