Preparation method of graphene lead sulfate composite material

Abstract

The application relates to the technical field of lead-acid storage batteries, and discloses a preparation method of a graphene lead sulfate composite material; the method comprises the following steps: mixing and stirring graphite, concentrated sulfuric acid and sodium nitrate at low temperature, adding potassium permanganate in the stirring process to obtain a low-temperature reaction product; increasing the low-temperature reaction product to medium temperature and reacting for a period of time to obtain a medium-temperature reaction product; adding distilled water and hydrogen peroxide to the medium-temperature reaction product after temperature reduction, washing the reaction product with a hydrochloric acid solution and distilled water after the reaction is completed, drying the reaction product to obtain solid material; mixing the solid material with lead sulfate trihydrate, performing ultrasonic treatment, and then performing immersion; performing extraction and filtration on the precipitated product after the immersion, and performing drying to obtain the graphene lead sulfate composite material. The graphene lead sulfate composite material is prepared by oxidizing and compounding the graphite, so that the conductivity of the material is improved; the graphene lead sulfate composite material can be subjected to graphite interlayer peeling during the manufacturing process, the specific surface area is increased, the conductivity of the battery is improved, and the conduction process is accelerated.

Description

Technical Field

[0001] This invention relates to the field of lead-acid battery technology, and in particular to a method for preparing a graphene-lead sulfate composite material. Background Technology

[0002] The graphite material used in the existing negative electrode material formulation of lead-acid batteries cannot fully utilize the active material of the electrode plate. In fact, only a portion of the active material is utilized during charging and discharging. Moreover, with the addition of carbon materials, the conductivity of the battery tends to decrease.

[0003] Current anode formulations directly incorporate graphite materials, which cannot guarantee the formation of a uniform conductive network within the active material. Many unconnected areas result in large lead sulfate particles, meaning only a portion of the active material is utilized during cycling. Over time, this leads to the formation of unconvertible lead sulfate particles, further reducing battery conductivity. Therefore, some have proposed adding modified graphene oxide composites to lead paste to improve this situation. However, existing graphene oxide preparation processes often require stringent reaction conditions, such as reacting at 100°C.

[0004] Therefore, there is an urgent need for a method to prepare graphene-lead sulfate composite material to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to solve the problems in the prior art, and to disclose a method for preparing graphene-lead sulfate composite material. The specific method is as follows:

[0006] A method for preparing a graphene-lead sulfate composite material includes the following steps:

[0007] S1 Low-temperature reaction: Graphite, concentrated H2SO4 (concentrated sulfuric acid), and NaNO3 (sodium nitrate) are mixed and stirred at low temperature. During the stirring process, KMnO4 (potassium permanganate) is added. After the addition is completed, the reaction continues for a period of time to obtain the low-temperature reaction product.

[0008] S2 medium-temperature reaction: The low-temperature reaction product obtained in step S1 is raised to a medium temperature and reacted for a period of time to obtain the medium-temperature reaction product.

[0009] S3 After cooling the product from the medium-temperature reaction in step S2, distilled water and hydrogen peroxide are added. After the reaction is completed, the product is washed with hydrochloric acid solution and distilled water, and then dried to obtain a solid material.

[0010] S4 The solid material obtained in step S3 is mixed with Pb(CH3COO)2·3H2O (lead acetate trihydrate), ultrasonically treated, and then impregnated; the impregnated product is precipitated in dilute sulfuric acid, and after extraction, filtration, and drying, graphene lead sulfate composite material is obtained.

[0011] Preferably, in step S1, the reaction temperature is 0-5℃.

[0012] Specifically, step S1 is as follows: take natural graphite, concentrated H2SO4 and NaNO3, pour them into a flask, place it in an ice-water bath, stir for 30 minutes at below 4°C, and add KMnO4 in batches during the stirring process. After the addition is complete, keep the temperature for 2 hours to complete the low-temperature stage.

[0013] Preferably, in step S2, the reaction temperature is 60°C and the reaction time is 10 hours.

[0014] Preferably, in step S2, the intermediate temperature reaction is completed under ultrasonic conditions.

[0015] Specifically, step S2 involves raising the low-temperature reaction product to 60°C, maintaining the temperature for 10 hours, and completing the intermediate-temperature reaction under ultrasonic conditions.

[0016] Preferably, in step S3, the volume fraction of hydrogen peroxide is 10% and the volume fraction of hydrochloric acid solution is 5%.

[0017] Preferably, in step S3, the washed reactants are dispersed in water, ultrasonically treated, and then dried.

[0018] Specifically, step S3 is as follows: The medium-temperature reaction product is cooled to room temperature (specifically, to 20°C) in ice water. A large amount of distilled water is added, along with hydrogen peroxide (10% by volume). The process is stopped when the solution changes from dark brown to a bright yellow. (In this process, the purpose of the hydrogen peroxide is to ensure complete reaction of the oxidant; there is no specific dosage requirement, just observe the color change. The distilled water used for washing is in excess, just enough to ensure thorough washing.) The resulting reaction product is washed with a large amount of HCl solution (5% by volume), followed by rinsing with distilled water until the pH of the washing solution is close to 7. Finally, the washed reaction product is dispersed in water, sonicated for 8 hours, and then dried in a vacuum drying oven to obtain a solid material.

[0019] Preferably, in step S4, the impregnation is performed at room temperature and pressure for 96 hours.

[0020] Specifically, step S4 is as follows: the solid material obtained in step S3 is mixed with an appropriate amount of Pb(CH3COO)2·3H2O (specifically, the molar mass ratio of the solid material obtained in step S3 to Pb(CH3COO)2·3H2O is 1:10), ultrasonically treated, impregnated at room temperature and pressure for 96 hours, the impregnated product is precipitated in dilute sulfuric acid, then filtered, and dried in an oven at 50°C to obtain graphene lead sulfate composite material.

[0021] Beneficial effects:

[0022] This invention improves the conductivity of graphite materials through oxidative composite processing. Furthermore, the introduction of small lead sulfate crystals between the graphite layers effectively mitigates the accumulation of large lead sulfate particles on the negative electrode surface, preventing irreversible sulfation. Additionally, the graphene-lead sulfate composite material undergoes interlayer exfoliation during manufacturing, resulting in a single layer of graphene oxide with a larger specific surface area, allowing it to accommodate more H₂ during charge and discharge. + and HSO4 - This improves the battery's conductivity and accelerates the conduction process. Attached Figure Description

[0023] Figure 1 This is a diagram showing the battery weights of lead-acid battery A and lead-acid battery B.

[0024] Figure 2 This is a diagram showing the battery capacity of lead-acid battery A and lead-acid battery B.

[0025] Figure 3 Charging acceptance diagrams for lead-acid battery A and lead-acid battery B at 90% state of charge;

[0026] Figure 4 Charging acceptance diagrams for lead-acid battery A and lead-acid battery B at 80% state of charge;

[0027] Figure 5 This is a continuous cycle diagram of lead-acid battery A and lead-acid battery B at 17.5% state of charge. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments. The illustrative embodiments and descriptions herein are used to explain the present invention, but are not intended to limit the present invention.

[0029] All raw materials used in this invention are not particularly restricted in their source and can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0030] There are no particular restrictions on the purity of any of the raw materials used in this invention; however, it is preferred to use materials with conventional purity levels used in the field.

[0031] Unless otherwise specified, the apparatus used in this invention employs commonly used devices in the field.

[0032] Example 1

[0033] A method for preparing a graphene-lead sulfate composite material includes the following steps:

[0034] 1. Take 1g of natural graphite, 23mL of concentrated H2SO4 and 0.5g of NaNO3, pour them into a flask, place it in an ice-water bath, stir for 30min at 4℃ or below, and add 3g of KMnO4 in batches during the stirring process. After the addition is complete, keep the reaction at the temperature for 2h to complete the low temperature stage.

[0035] 2. Raise the system temperature to 60℃ and maintain the temperature for 10 hours. The system completes the mesophilic reaction under ultrasonic conditions.

[0036] 3. After the intermediate-temperature reaction is complete, the obtained product is cooled in ice water, and a large amount of distilled water is added, along with hydrogen peroxide (10% by volume). The reaction is stopped when the solution changes from dark brown to bright yellow. The obtained product is then washed with a large amount of HCl (5% by volume) and distilled water until the pH of the washing solution is close to 7. Finally, the washed product is dispersed in water, sonicated for 8 hours, and then dried in a vacuum drying oven to obtain a solid material.

[0037] 4. Mix the solid material obtained in step 3 with Pb(CH3COO)2·3H2O, wherein the molar mass ratio of the solid material obtained in step 3 to Pb(CH3COO)2·3H2O is 1:10. Sonicate the mixture and impregnate it at room temperature and pressure for 96 hours. The impregnated product is precipitated in dilute sulfuric acid, then filtered and dried in an oven at 50°C to obtain graphene lead sulfate composite material.

[0038] Comparative Example 1

[0039] 1. Take 1g of natural graphite, 23mL of concentrated H2SO4 and 0.5g of NaNO3, pour them into a flask, place it in an ice-water bath, stir for 30min at 4℃ or below, and add 3g of KMnO4 in batches during the stirring process. After the addition is complete, keep the reaction at the temperature for 2h to complete the low temperature stage.

[0040] 2. Raise the system temperature to 35℃ and maintain the temperature for 3 hours to complete the mesophilic reaction.

[0041] 3. Raise the system temperature to 100℃, add 46mL of distilled water dropwise, and react for 1 hour to complete the high-temperature reaction.

[0042] 4. After the reaction is complete, add 75 mL of distilled water and 15 mL of hydrogen peroxide, stir continuously for 15 min, filter while hot, and wash with a large amount of HCl (5% by volume) followed by a large amount of distilled water until the pH of the product is close to 7. Finally, disperse the obtained product in water, sonicate for 8 h, and dry in a vacuum drying oven to obtain graphene oxide.

[0043] The comparative example is a method for producing graphene oxide in the prior art. From this process, it can be understood that the preparation process of Example 1 of the present invention does not involve a high-temperature reaction process, and the reaction process of the present invention is easier to implement.

[0044] Experiments and Tests

[0045] The graphene-lead sulfate composite material obtained in Example 1 was added to the negative electrode formulation of a lead-acid battery at 2% of the lead powder mass as negative electrode paste A; graphite was added to the same negative electrode formulation of a lead-acid battery at 2% of the lead powder mass as negative electrode paste B. Lead-acid batteries were prepared using negative electrode paste A and negative electrode paste B respectively through the same process; lead-acid battery A and lead-acid battery B were then tested.

[0046] Lead paste A is composed of: lead powder, acid, water, fiber, graphene-lead sulfate composite material, humic acid, and lignin. Specifically, the following amounts are added: acid at 5% of the lead powder mass, water at 10% of the lead powder mass, fiber at 0.05% of the lead powder mass, graphene-lead sulfate composite material at 0.25% of the lead powder mass, and humic acid-lignin premix (slurry) at 1.7% of the lead powder mass. The graphene-lead sulfate composite material in lead paste A is mixed with other materials through grinding.

[0047] Lead paste B is composed of: lead powder, acid, water, fiber, graphite, humic acid, and lignin. Specifically, the following additives are used: acid at 5% of the lead powder mass, water at 10% of the lead powder mass, fiber at 0.05% of the lead powder mass, graphite at 0.25% of the lead powder mass, and humic acid-lignin premix (slurry) at 1.7% of the lead powder mass. During testing, the test results obtained from lead-acid battery A are labeled "complex," and the test results from lead-acid battery B are labeled "blank."

[0048] like Figure 1 The diagram shows the battery weights of lead-acid battery A and lead-acid battery B. The battery weights of lead-acid battery A and lead-acid battery B are almost identical, so the error caused by battery weight can be ignored.

[0049] like Figure 2 The diagram shows the battery capacity of lead-acid battery A and lead-acid battery B; the battery capacity of lead-acid battery A is about 2% higher than that of lead-acid battery B.

[0050] like Figure 3 The diagram shows the charging acceptance of lead-acid battery A and lead-acid battery B at 90% state of charge; lead-acid battery A is about 28% higher than lead-acid battery B.

[0051] like Figure 4 The diagram shows the charging acceptance of lead-acid battery A and lead-acid battery B at 80% state of charge; lead-acid battery A is about 29% higher than lead-acid battery B.

[0052] like Figure 5 The figure shows the continuous cycle diagram of lead-acid battery A and lead-acid battery B at a state of 17.5% charge; lead-acid battery A is about 26% higher than lead-acid battery B.

[0053] In this invention, the high-temperature stage of the intermediate-temperature reaction stage is replaced by extending the time and increasing the temperature of the intermediate-temperature stage. This design primarily aims to reduce the decomposition of potassium permanganate during the high-temperature stage, thereby allowing for a more complete reaction between graphite and the oxidant, increasing the degree of oxidation between graphite layers, and further improving the quality and yield of graphene oxide.

[0054] The method of this invention aims to better distribute lead sulfate on graphene and to better combine it with additives such as lignin and humic acid in the negative electrode formulation of lead-acid batteries, thereby forming a more stable molecular network to improve the conductivity of lead paste. Figure 3 , Figure 4 At 90% and 80% charge, compared with lead-acid battery B, lead-acid battery A has a more stable molecular network, which is conducive to the transfer of electrons between the grid and the lead paste. Therefore, at the same charge state, the battery with graphene lead sulfate composite material will have a larger conductive current, which enhances the battery's charging acceptance.

[0055] In the intermediate-temperature reaction stage, ultrasound assistance is used. Utilizing the high energy and strong penetrating power of ultrasound, the reaction rate can be accelerated and the quality of the product improved. Furthermore, it ensures a uniform distribution of graphite layers, facilitating the subsequent production of homogeneous graphene. Combined with… Figure 2 , Figure 4 It can also be seen that, due to the addition of graphene-lead sulfate composite material with a more uniform distribution, the uniform distribution of carbon material inside the lead paste can be effectively improved, thereby increasing the utilization rate of the lead paste. As a result, the capacity and cycle life of lead-acid batteries will also be improved.

[0056] A novel composite material, graphene-lead sulfate composite, was formed by oxidizing graphene in the battery negative electrode formulation and adding lead sulfate. This composite material was then added to the negative electrode formulation through purification and grinding processes (the rinsing and drying in Example 1 was for product purification, and the grinding process was to better disperse the graphene-lead sulfate composite material among the active materials to form a conductive network), replacing the original graphite in the formulation. Performance verification of the battery with the added graphene-lead sulfate composite material showed significant improvements in capacity, charge acceptance, and cycle life.

[0057] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a graphene-lead sulfate composite material, characterized in that: Includes the following steps: S1 Low-temperature reaction: Graphite, concentrated H2SO4, and NaNO3 are mixed and stirred at low temperature. KMnO4 is added during the stirring process. After the addition is completed, the reaction continues for a period of time to obtain the low-temperature reaction product. S2 medium-temperature reaction: The low-temperature reaction product obtained in step S1 is raised to a medium temperature and reacted for a period of time to obtain the medium-temperature reaction product. S3 After cooling the product from the medium-temperature reaction in step S2, distilled water and hydrogen peroxide are added. After the reaction is completed, the product is washed with hydrochloric acid solution and distilled water, and then dried to obtain a solid material. S4 The solid material obtained in step S3 is mixed with Pb(CH3COO)2•3H2O, ultrasonically treated, and then impregnated; the impregnated product is precipitated in dilute sulfuric acid, and after extraction, filtration, and drying, graphene lead sulfate composite material is obtained. In step S1, the reaction temperature is 0-5℃; In step S2, the reaction temperature is 60℃ and the reaction time is 10h.

2. The method for preparing a graphene-lead sulfate composite material according to claim 1, characterized in that: In step S2, the intermediate temperature reaction is completed under ultrasonic conditions.

3. The method for preparing a graphene-lead sulfate composite material according to claim 1, characterized in that: In step S3, the volume fraction of hydrogen peroxide is 10%, and the volume fraction of hydrochloric acid solution is 5%.

4. The method for preparing a graphene-lead sulfate composite material according to claim 1, characterized in that: In step S3, the washed graphene oxide is dispersed in water, ultrasonically treated, and then dried.

5. The method for preparing a graphene-lead sulfate composite material according to claim 1, characterized in that: In step S4, the immersion is performed at room temperature and pressure for 96 hours.

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