A Pb atomic cluster / ordered mesoporous carbon composite material, its preparation method and application

Abstract

The Pb atom cluster / ordered mesoporous carbon composite material to be protected by the present invention has the characteristics of inhibiting the growth of PbSO4 crystal particles and the hydrogen evolution reaction at the negative electrode. A Pb atom cluster / ordered mesoporous carbon material uses ordered mesoporous carbon as a carrier, and Pb is loaded on the ordered mesoporous carbon in the form of Pb atom clusters aggregated by 10 - 5000 (preferably 20 - 2000, more preferably 20 - 500) Pb atoms. The mass content of Pb in the material is 0.001 - 10%, preferably 0.005 - 1%, more preferably 0.01 - 0.5%. This material is prepared by depositing Pb atoms into the pores of the ordered mesoporous carbon by using the PVD method. The ordered mesoporous carbon has an appropriate specific surface area, and Pb exists in the form of atom clusters in its pores.

Description

Technical Field

[0001] The present invention relates to the field of lead-carbon batteries, and particularly to a carbon additive for the negative electrode of lead-carbon batteries. Background Art

[0002] Lead-acid batteries have the advantages of simple and reliable structure, low cost, high safety, good recyclability, etc., and have been applied in the energy storage field and widely used in emergency lights, automobiles, navigation, aviation, military and other fields. Especially in the fields of internal combustion engine starting, backup power supply, and hybrid vehicles, lead-acid batteries have an irreplaceable position and value. However, hybrid vehicles require lead-acid batteries to work under high-rate conditions. The low energy density, sulfation of the negative active material, and low cycle life under high-rate conditions severely restrict the application of lead-acid batteries under high-rate and partial state of charge conditions. Therefore, solving the problem of sulfate formation on the negative electrode under high-rate conditions and improving the energy density of lead-acid batteries are urgent problems to be solved at present. In recent years, in-depth studies have been carried out on problems such as the low power density, low cycle life, and battery failure under high-rate conditions of lead-acid batteries. It has been found that the power density of lead-acid batteries mainly depends on the utilization rate of the active material in the negative electrode. The discharge product of lead-acid batteries is insulating PbSO4. Large particle PbSO4 crystals form an insulating layer on the negative electrode, hindering the reaction between the internal active material and the electrolyte, resulting in battery failure. To solve the above problems, researchers have tried to use carbon materials as additives in the battery negative electrode, that is, carbon materials such as carbon black, carbon nanotubes, acetylene black, activated carbon, etc. are added as additives to the NAM to construct an internal hybrid lead-carbon battery.

[0003] The research found that after adding carbon materials, the overall conductivity of the battery was improved, and the sulfation of the negative electrode under high-rate conditions was also inhibited. It was found that adding carbon materials to the negative electrode could form a conductive network in the negative electrode active material, providing a channel for the transfer of electrons during charge and discharge, thereby improving the charge and discharge capacity of the battery. In addition, some researchers also found that the sulfation of the negative electrode of lead-acid batteries was related to the size of PbSO4 crystal particles. When the discharge current was too large, large particles of PbSO4 crystals would be generated, forming an insulating layer on the electrode surface. If small particles of lead sulfate crystals were generated during the discharge process, battery failure could be avoided because small particles of lead sulfate grains had good electrochemical activity. Further research found that when high specific capacitance carbon materials were added to the negative electrode, these carbon materials could act as the electrodes of supercapacitors, reducing the discharge current of the battery active material, thereby reducing the size of PbSO4 crystal particles and improving the cycle life of the battery. If the specific surface area of the carbon material was too high, the low-temperature capacity retention rate of the battery would decrease. The main reason for this phenomenon was that carbon materials with a high specific surface area would seriously adsorb organic additives in the negative electrode active material. For the negative electrode additives of the internal mixing type lead-carbon battery, two main conditions needed to be met: (1) having an inhibitory effect on the growth of PbSO4 crystal particles; (2) having a high hydrogen evolution overpotential. There have been reports on the ability of Pb oxides to inhibit the hydrogen evolution reaction on the carbon additives of the negative electrode of lead-acid batteries (Zheqi Lin, Nan Lin, Haibo Lin, Wenli Zhang, Significance of PbO deposition ratio inactivated carbon-based lead carbon composites for lead-carbon battery underhigh-rate partial state-of-charge operation, Electrochimica Acta 338(2020)135868). In addition, the researchers also found that the introduction of Pb oxides could also increase the specific capacitance of carbon materials. Although introducing lead elements into carbon materials was expected to obtain high-performance lead-carbon composites, due to the too low melting point of metallic Pb, it was difficult to prepare lead-carbon composites using traditional impregnation and high-temperature roasting processes because during the high-temperature roasting process, lead salts or oxides would be reduced by C to metallic Pb. The reduced metallic Pb would melt and aggregate into metal balls, separating from the carbon materials.) Summary of the Invention

[0004] The technical problem to be solved by the present invention (the purpose of the invention)

[0005] The Pb atom cluster / ordered mesoporous carbon composite material to be protected by the present invention has the characteristics of inhibiting the growth of PbSO4 crystal particles and the hydrogen evolution reaction of the negative electrode.

[0006] A Pb atomic cluster / ordered mesoporous carbon material, with ordered mesoporous carbon as the carrier, and Pb is loaded on the ordered mesoporous carbon in the form of Pb atomic clusters aggregated by 10 - 5000 (preferably 20 - 2000, more preferably 20 - 500) Pb atoms. The mass content of Pb in the material is 0.005 - 1%, more preferably 0.01 - 0.5%.

[0007] Using ordered mesoporous carbon as the carrier, the Pb atoms are deposited on the outer surface and pore channels of the ordered mesoporous carbon by the PVD method to obtain the material.

[0008] The preparation process of the ordered mesoporous carbon is as follows.

[0009] Weigh the carbon source and sulfuric acid solution, where the mass concentration of the H2SO4 solution is 94 - 98% and it is dissolved in water. The ratio of the sum of the mass of the carbon source and the sulfuric acid solution to the mass of water is (0.1 - 10):3, preferably (0.3 - 2):3. Then weigh 15 g of the template agent (the template agent is one or more of F127, P123, SBA15, etc., preferably SBA - 15) and add it to the solution. Among them, the mass fraction ratio of the carbon source, sulfuric acid solution, and template agent is: 1 - 200:0.1 - 20:1 - 150 (preferably 10 - 30:1 - 5:10 - 20). The mixture is dried in the first stage, and then the temperature is raised for the second - stage drying. Subsequently, the product is transferred to an atmosphere environment for carbonization and sintering. The obtained product is soaked in a dilute hydrofluoric acid solution to remove the template agent. The prepared ordered mesoporous carbon has a specific surface area of 800 m 2 / g - 2800 m 2 / g; the average pore diameter is 0.5 nm - 5 μm;

[0010] The drying temperature in the first stage is 60 - 120 °C, and the drying time is 0.5 - 24 hours. The function of the first - stage drying is to remove the excess water in the product and concentrate the sulfuric acid solution. The second - stage drying is at 200 - 300 °C, and the drying time is 0.5 - 24 hours. The purpose is to pre - carbonize the ordered mesoporous carbon material by the strong oxidation of sulfuric acid and reserve a certain amount of concentrated sulfuric acid solution or sulfate ions in the mesopores.

[0011] The temperature of the carbonization and sintering process is 800 - 1200 °C, the carbonization time is 0.5 - 24 hours, preferably 4 - 6 hours; the sintering is carried out in nitrogen and / or an inert atmosphere (such as one or more of helium, neon, argon);

[0012] Among them, the ratio of the total mass of the template agent to the total mass of the hydrofluoric acid aqueous solution is: 20 - 80:100 - 500, the concentration of the hydrofluoric acid aqueous solution is 0.1 - 20%, preferably 2 - 8%; the carbon source is one or more of sucrose, glucose, xylitol, dopamine, etc.

[0013] The process of the PVD (Physical Vapor Deposition) method is as follows:

[0014] The lead foil substrate cleaned with dilute nitric acid (mass concentration 0.1%-15%) is placed in a magnetron sputtering coating machine with the mass ratio of the substrate to the carbon material being (0.1-10):1 (preferably (0.1-5):1), and the vacuum is pumped. When the vacuum degree of the coating chamber is lower than 1.0×10 -3 Pa, turn on the substrate heating power supply and heat up to 100-350°C (preferably 180-240°C); turn on the ion source to perform ion cleaning on the surface of the substrate for 1-500 min (preferably 1-30 min); after the ion cleaning is completed, turn on the sputtering power supply and start depositing Pb elements on the prepared ordered mesoporous carbon for 1-500 min (preferably 1-60 min).

[0015] This electrode is applied to the negative electrode of a lead-carbon battery.

[0016] The lead-carbon battery is an internal mixing type lead-carbon battery, an internal parallel type lead-carbon battery or a full carbon negative electrode type lead-carbon battery.

[0017] Advantages of the present invention:

[0018] This material is prepared by depositing Pb atoms into the pores of ordered mesoporous carbon by the PVD method. The ordered mesoporous carbon has an appropriate specific surface area, and Pb exists in the form of atomic clusters in its pores. Since the melting point of lead element is lower than the generation temperature of carbon material during the sintering process, the conventional preparation method cannot generate lead atomic clusters on the surface of carbon material while preparing carbon material. On the contrary, if the impregnation reduction method is used to prepare lead atomic clusters, the size of the atomic clusters is uncontrollable and large particle lead crystals are easily generated. The present invention uses physical vapor deposition to prepare Pb atomic cluster / ordered mesoporous carbon composite materials. In the negative electrode of a lead-carbon battery, the Pb atomic clusters can play a role in inhibiting the hydrogen evolution reaction in the pores of the ordered mesoporous carbon material and serving as the crystal seeds for the precipitation reaction of PbSO4 crystal particles. Applying the Pb atomic cluster / ordered mesoporous carbon composite material as a negative electrode additive to a lead-carbon battery can significantly improve the cycle life of the battery, reduce the gas generation amount and water consumption of the battery, and improve the low-temperature performance of the battery. Specific embodiments

[0019] Example 1

[0020] 1. The Pb atom cluster / ordered mesoporous carbon is prepared by the following method: Weigh 20 g of sucrose and 2 g of 98% H₂SO₄ by mass concentration and dissolve them in 75 ml of H₂O. Subsequently, weigh 15 g of SBA15 (mesoporous molecular sieve SBA-15) and add it to the mixed solution. Transfer the mixture to an oven at 100 °C and dry it for 1 hour. Then, raise the oven temperature to 250 °C and keep it for 6 hours. Subsequently, transfer the product to a tube furnace in a nitrogen environment for sintering. The sintering temperature is 900 °C and the sintering time is 5 hours. Immerse the obtained product in 200 ml of 5% HF solution by mass concentration for washing to remove the SBA15 template. An ordered mesoporous carbon composite material is obtained. The average particle size of the mesoporous carbon composite material is about 10 nm, and the mesoporous size on its surface is 0.1 - 2 nm.

[0021] Take a lead foil substrate cleaned with 20 g of 5% nitric acid by mass concentration. Put the lead foil substrate and the carbon composite material prepared above into a magnetron sputtering coater. Turn on the vacuum pumping unit. When the vacuum degree in the coating chamber is lower than 1.0×10 -3 Pa, turn on the substrate heating power supply and heat it up to 200 °C. Subsequently, close the vacuum gauge and turn on the power supply, turn on the ion source, and perform ion cleaning on the substrate surface for 5 minutes. After the ion cleaning is completed, turn on the sputtering power supply and start depositing Pb elements on the surface and inside of the prepared ordered mesoporous carbon. The deposition time is 20 minutes to obtain Pb atom cluster / ordered mesoporous carbon. Perform thermogravimetric testing on the product. The testing environment is an air environment. The sample is heated from room temperature to 600 °C. The heating process can ensure that the carbon material is completely sintered clean. By weighing the remaining mass of the product, it can be known that in the composite material prepared under this condition, the mass of lead element accounts for 0.11% of the total mass. Place the product sample under a high-resolution transmission electron microscope. Through measurement and analysis, it can be known that the average size of the lead atom clusters supported on the mesoporous carbon surface is about 1 nm, the number of atoms in the atom cluster is 20 - 2000, and the average number of atoms contained is about 450.

[0022] 2. The negative electrode of the lead-carbon battery is prepared by the following steps: (1) 600 g of lead powder, 9 g of Pb atomic cluster / ordered mesoporous carbon, 8.4 g of barium sulfate, and 0.3 g of polypropylene short fibers with a length of 5 mm are premixed with a high-speed mixer. While stirring, 84 g of deionized water is added to the premixed powder, and continuous stirring is carried out for 10 min to obtain a lead paste; (2) The lead paste is scraped onto a metallic lead grid and dried and cured to obtain the negative electrode of the lead-carbon battery. The curing temperature is 40 °C, the humidity is 80%, and the curing time is 20 hours; the drying temperature is 80 °C, and the time is 24 hours; (3) The positive electrode of the lead-acid battery is prepared by the same process. Four internally mixed lead-carbon battery electrodes with modified activated carbon are connected in parallel as the negative electrode, and are connected in series with three connected-in-parallel positive electrodes of the lead-acid battery to assemble an internally mixed lead-carbon battery. The positive active material of the lead-acid battery is lead oxide with a mass of 20.0 g. Except for the grid of the negative electrode, the total mass of the material filled into the grid voids is 14.3 g. The positive and negative grids use conventional lead grids; (4) Three positive plates and two negative plates are arranged at intervals. The positive and negative electrodes are placed in a tightly assembled battery case, where the length of the battery case is 76 mm, the width is 40 mm, and the height is 100 mm. 83 g of sulfuric acid electrolyte with a density of 1.275 g / ml is injected into the battery case; (5) The battery is subjected to a capacity test. The test conditions are as follows: at room temperature, constant current discharge is carried out at 0.52 A until the battery voltage reaches 1.8 V, and the room temperature capacity of the battery is recorded. Constant current and constant voltage charging are carried out at 0.52 A current and 2.4 V voltage for 24 hours. Subsequently, the battery is left standing at -10 °C for 10 hours. After 10 hours, constant current discharge is carried out at 0.52 A current until the battery voltage is 1.8 V, and the low-temperature capacity of the battery is recorded.

[0023] Under this condition, the low-temperature capacity of the lead-carbon battery with modified activated carbon can reach 4140 mAh, and the ratio of the low-temperature capacity to the room temperature capacity is 75%. Compared with the test results of a common lead-carbon battery under the same test conditions (low-temperature capacity 3869 mAh, ratio of low-temperature capacity to room temperature capacity 72%), the low-temperature capacity of the lead-carbon battery with Pb atomic cluster / ordered mesoporous carbon is 7% higher than that of the common lead-carbon battery.

[0024] Example 2

[0025] Under the conditions of Example 1, when the mass of sucrose was changed to 15 g, the test results of the assembled internal mixing type battery showed that the low-temperature capacity of the lead-carbon battery with modified activated carbon could reach 4233 mAh under this condition, and the ratio of low-temperature capacity to normal-temperature capacity was 74%. Compared with the test results of a common lead-carbon battery under the same test conditions (low-temperature capacity 3869 mAh, ratio of low-temperature capacity to normal-temperature capacity 72%), the low-temperature capacity of the lead-carbon battery with Pb atomic clusters / ordered mesoporous carbon was 9% higher than that of the common lead-carbon battery. Due to the reduction of sucrose content, the prepared ordered mesoporous carbon structure was more porous, reducing the internal resistance of the final product, and thus reducing the internal resistance of the prepared lead-carbon battery, so the low-temperature capacity of the lead-carbon battery was improved.

[0026] Example 3

[0027] Under the conditions of Example 1, when the mass of SBA15 was changed to 25 g, since the change in the mass of the template agent led to a change in the specific surface area of the prepared mesoporous carbon composite material and a change in the mass of lead ions supported per unit area, the test results of the assembled internal mixing type battery showed that the low-temperature capacity of the lead-carbon battery with modified activated carbon could reach 4231 mAh under this condition, and the ratio of low-temperature capacity to normal-temperature capacity was 74%. Compared with the test results of a common lead-carbon battery under the same test conditions (low-temperature capacity 3869 mAh, ratio of low-temperature capacity to normal-temperature capacity 72%), the low-temperature capacity of the lead-carbon battery with modified activated carbon was 9% higher than that of the common lead-carbon battery. A larger specific surface area was beneficial for storing a certain amount of sulfuric acid electrolyte inside the carbon material, which was beneficial for the charge and discharge cycle of the lead-carbon battery under low-temperature conditions, so the low-temperature capacity of the lead-carbon battery was improved.

[0028] Example 4

[0029] Under the conditions of Example 1, when the sputtering deposition time of lead element was changed to 1 min, since the sputtering deposition time of lead element was too short, resulting in a change in the mass of lead ions supported per unit area. After testing, the mass percentage of lead element in the carbon material was: 0.02%, the size of the lead atomic cluster was about 0.8 nm, and the number of lead atoms contained was about: 370. The test results of the assembled internal mixing type battery showed that the low-temperature capacity of the lead-carbon battery with modified activated carbon could reach 4145 mAh under this condition, and the ratio of low-temperature capacity to normal-temperature capacity was 74%. Compared with the test results of a common lead-carbon battery under the same test conditions (low-temperature capacity 3869 mAh, ratio of low-temperature capacity to normal-temperature capacity 72%), the low-temperature capacity of the lead-carbon battery with modified activated carbon was 7% higher than that of the common lead-carbon battery. Due to the reduction of the amount of lead element, the improvement of the internal resistance of the carbon material was not obvious, resulting in an not very significant improvement in the low-temperature capacity of the prepared lead-carbon battery.

[0030] Comparative Example 1

[0031] Under the conditions of Example 1, commercial activated carbon with a specific surface area of approximately 1300 m 2 / g and the same mass was used to replace the ordered mesoporous carbon. The test results of the assembled internal mixing type battery showed that the low-temperature capacity of the lead-carbon battery could reach 3869 mAh under these conditions, and the ratio of the low-temperature capacity to the normal-temperature capacity was 72%.

[0032] Comparative Example 2

[0033] Under the conditions of Example 1, a lead oxide substrate with the same mass was used as the lead source for sputtering, and the temperature in the sputtering chamber was increased to 120 °C. After testing, the atomic clusters supported on the surface of the carbon material were mainly composed of lead oxide. The low-temperature capacity of the assembled internal mixing type battery could reach 3673 mAh under these conditions, and the ratio of the low-temperature capacity to the normal-temperature capacity was 68%. The deposition of lead oxide on the surface of the carbon material increased the internal resistance of the battery and affected the performance of the battery's low-temperature capacity.

[0034] Comparative Example 3

[0035] Under the conditions of Example 1, the temperature in the sputtering chamber was increased to 600 °C. Since the crystallization growth process of the lead element deposited at high temperature was too fast, the particle size of the lead element was relatively large, increasing the internal resistance of the carbon material and being unfavorable for the performance of the lead-carbon battery at low temperature. The low-temperature capacity of the assembled internal mixing type battery could reach 3942 mAh under these conditions, and the ratio of the low-temperature capacity to the normal-temperature capacity was 70%.

[0036] Comparative Example 4

[0037] Under the conditions of Example 1, the working time of sputtering was extended to 600 min. Since too much lead element was sputtered out, the crystallization growth of the lead element was too fast, resulting in a relatively large particle size of the lead element and increasing the internal resistance of the carbon material, which was unfavorable for the performance of the lead-carbon battery at low temperature. The low-temperature capacity of the assembled internal mixing type battery could reach 3895 mAh under these conditions, and the ratio of the low-temperature capacity to the normal-temperature capacity was 70%.

Claims

1. A preparation method of Pb atomic cluster / ordered mesoporous carbon material, characterized in that, It is prepared by depositing Pb atoms on the outer surface and pores of ordered mesoporous carbon by PVD method using ordered mesoporous carbon as the carrier. The preparation process of the ordered mesoporous carbon is as follows. Weigh the carbon source and sulfuric acid solution, where the mass concentration of the H2SO4 solution is 94 - 98% and it is dissolved in water. The ratio of the sum of the mass of the carbon source and the sulfuric acid solution to the mass of water is (0.1 - 10):

3. Then weigh the template agent and add it to the solution. Among them, the mass fraction ratio of the carbon source, sulfuric acid solution, and template agent is: 1 - 200:0.1 - 20:1 - 150. The mixture is dried in the first stage, then the temperature is raised for the second stage of drying, and then the product is transferred to an atmosphere environment for carbonization and sintering. The obtained product is soaked in a dilute hydrofluoric acid solution to remove the template agent. The carbon source is one or more of sucrose, glucose, xylitol, and dopamine. The Pb atom cluster / ordered mesoporous carbon material is based on ordered mesoporous carbon as the carrier, and Pb is loaded on the ordered mesoporous carbon in the form of Pb atom clusters composed of 10 - 5000 Pb atoms. The mass content of Pb in the material is 0.005 - 1%.

2. The preparation method according to claim 1, characterized in that: In the Pb atom cluster / ordered mesoporous carbon material, Pb is loaded on the ordered mesoporous carbon in the form of Pb atom clusters composed of 20 - 2000 Pb atoms.

3. The preparation method according to claim 1, characterized in that: In the Pb atom cluster / ordered mesoporous carbon material, Pb is loaded on the ordered mesoporous carbon in the form of Pb atom clusters composed of 20 - 500 Pb atoms.

4. The preparation method according to claim 1, characterized in that: The mass content of Pb in the material is 0.01 - 0.5%.

5. According to the preparation method described in claim 1, it is characterized in that: The ratio of the sum of the mass of the carbon source and the sulfuric acid solution to the mass of water is (0.3 - 2):

3. The template agent is one or more of F127, P123, and SBA15, SBA - 15. The mass fraction ratio of the carbon source, sulfuric acid solution, and template agent is: 10 - 30:1 - 5:10 - 20.

6. According to the preparation method described in claim 1, it is characterized in that: The prepared ordered mesoporous carbon has a specific surface area of 800 m 2 / g - 2800 m 2 / g; the average pore diameter is 0.5 nm - 5 μm; The drying temperature in the first stage is 60 - 120 °C, the drying time is 0.5 - 24 hours, the second stage of drying is 200 - 300 °C, and the drying time is 0.5 - 24 hours.

7. The preparation method according to claim 1, characterized in that: The temperature of the carbonization and sintering process is 800 - 1200 °C, the carbonization time is 0.5 - 24 hours; the atmosphere environment used for sintering is one or more of nitrogen and / or inert atmosphere; the inert atmosphere is one of helium, neon, and argon. Among them, the ratio of the total mass of the template agent to the total mass of the hydrofluoric acid aqueous solution is: 20 - 80:100 - 500, and the concentration of the hydrofluoric acid aqueous solution is 0.1 - 20%.

8. The preparation method according to claim 7, characterized in that: During the carbonization and sintering process, the carbonization time is 4 - 6 hours, and the concentration of the hydrofluoric acid aqueous solution is 2 - 8%.

9. The preparation method according to claim 1, wherein: The PVD method, that is, the physical vapor deposition method process is, After cleaning the lead foil substrate with dilute nitric acid with a mass concentration of 0.1% - 15%, put the substrate into a magnetron sputtering coater with a mass ratio of the substrate to the carbon material of (0.1 - 10):1, and evacuate the chamber; when the vacuum degree of the coating chamber is lower than 1.0×10 -3 Pa, turn on the substrate heating power supply and heat up to 100 - 350 °C; turn on the ion source to perform ion cleaning on the surface of the substrate for 1 - 500 min; after the ion cleaning is completed, turn on the sputtering power supply and start depositing Pb elements on the prepared ordered mesoporous carbon for 1 - 500 min.

10. The preparation method according to claim 9, characterized in that: The PVD method process is, After cleaning the lead foil substrate with dilute nitric acid with a mass concentration of 0.1% - 15%, put the substrate into a magnetron sputtering coater with a mass ratio of substrate to carbon material of (0.1 - 5):1, and evacuate the chamber. When the vacuum degree of the coating chamber is lower than 1.0×10 -3 Pa, turn on the substrate heating power supply and heat it up to 180 - 240 °C. Turn on the ion source and perform ion cleaning on the substrate surface for 1 - 30 minutes. After the ion cleaning is completed, turn on the sputtering power supply and start depositing Pb elements on the prepared ordered mesoporous carbon for 1 - 60 minutes.

11. A Pb atom cluster / ordered mesoporous carbon material prepared by the preparation method described in claims 1 - 10.

12. An application of the Pb atom cluster / ordered mesoporous carbon material described in claim 11 as an electrode of a lead - carbon battery in a lead - carbon battery, and this electrode is applied to the negative electrode of the lead - carbon battery.

13. The application according to claim 12, wherein: The lead-carbon battery is an internally mixed lead-carbon battery, an internally parallel lead-carbon battery or a full-carbon negative electrode type lead-carbon battery.