A composite carbon material rich in N and K elements, its preparation and application

Abstract

The present invention provides a low-cost carbon material rich in N functional groups, a preparation method thereof that is easy to achieve large-scale production, and the application of the carbon material rich in N functional groups in the negative electrode of a lead-carbon battery. A preparation method of a composite carbon material rich in N and K elements uses activated carbon as a carrier, and under the combined action of an additive and an activator, a composite carbon material rich in N and K elements is prepared; the mass ratio of the additive to the activated carbon is (0.004 - 0.008):1; the mass ratio of the additive to the activator is (1 - 30):(30 - 1), preferably (1 - 10):(10 - 1). The C-N bonds on the surface of the carbon material prepared by sintering in an ammonia atmosphere are more stable, and can resist the loss of N elements caused by the potential change on the surface of the carbon material during the battery cycle life test, which is more conducive to preparing a carbon material with excellent performance.

Description

Technical Field

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

[0002] As a secondary battery, lead-acid batteries have the characteristics of mature technology, rich raw materials, low price, and good safety performance, and are widely used in fields such as hybrid electric vehicles (HEVs), SLI (starting, lighting, and ignition), and energy storage systems. However, when lead-acid batteries operate under conditions of high current density and insufficient charging (i.e., high-rate partial state of charge (HRPSoC)), PbSO4 will rapidly accumulate on the surface of the negative electrode plate, causing irreversible sulfation of the negative electrode plate. Therefore, the sulfation of the negative electrode plate in the HRPSoC mode greatly limits the application of lead-acid batteries in the fields of HEVs, solar street lamps, and large-scale energy storage. Lead-carbon batteries are a new type of energy storage battery developed on the basis of lead-acid batteries and supercapacitors. In the internal mixing type lead-carbon battery, the irreversible sulfation process of the negative electrode plate is effectively inhibited by adding a certain amount of carbon material to the negative electrode active material (NAM), thereby greatly extending its cycle life under the partial state of charge (PSoC) and HRPSoC conditions. A variety of carbon materials such as graphite, activated carbon, carbon black, graphene, and carbon nanotubes have been applied to the negative electrode of lead-carbon batteries. The main functions of carbon materials in the negative electrode of lead-carbon batteries include: enhancing the electronic conductivity of the negative electrode plate, inhibiting the growth of PbSO4 on the surface of the negative electrode plate, increasing the electroosmotic pump effect, and increasing the specific surface area and capacitance of NAM. However, adding carbon materials to NAM will increase the hydrogen evolution amount at the negative electrode, resulting in an increase in the water consumption of the battery, leading to premature drying of the battery and limiting the further improvement of the battery cycle life. In addition, the intensification of the hydrogen evolution reaction (HER) at the negative electrode will also pose certain safety hazards to large-scale energy storage systems.

[0003] In order to inhibit the HER reaction, researchers have done a lot of research work. Generally, the hydrogen evolution current of the electrode can be reduced by increasing the overpotential of the HER reaction. Hong et al. prepared AC (NAC) rich in N functional groups. The experimental results show that the hydrogen evolution current of the NAC electrode is much lower than that of the AC electrode. Since the electronegativity of N atoms is greater than that of C atoms, when N atoms are doped into AC, N atoms will adsorb the electrons around C atoms, reducing the electron density around C atoms and weakening the C atom and H +The strength of the hydrogen bonds formed therein is thus reduced, thereby inhibiting HER (Hong B, Yu X, Jiang L, Xue H, Liu F, Li J, Liu Y. Hydrogen evolution inhibition with diethylenetriamine modification of activated carbon for a lead-acid battery. RSC Adv, 2014, 4: 33574-33577). The preparation method adopted by Hong et al. is as follows: Commercial activated carbon, which serves as the base carbon material, is added to an ethanol solution of diethylenetriamine, and then refluxed at 80 °C for 4 h. Subsequently, it is filtered, washed, and dried to obtain NAC. This preparation method is rather cumbersome, resulting in a relatively high manufacturing cost of the material. Summary of the Invention

[0004] The technical problem (invention objective) to be solved by the present invention:

[0005] In view of the above problems, the present invention provides a low-cost N-functional group-rich carbon material, a preparation method thereof that is easy to achieve large-scale production, and the application of the N-functional group-rich carbon material in the negative electrode of a lead-carbon battery.

[0006] A preparation method of a composite carbon material rich in N and K elements, using activated carbon as a carrier, and realizing the preparation of the composite carbon material rich in N and K elements under the co-action of an additive and an activator;

[0007] The mass ratio of the additive to the activated carbon is (0.004 - 0.008):1; the additive is one or more of ethylenediaminetetraacetic acid, tetraammonium ethylenediaminetetraacetate, ethylenediaminetetraacetic acid (EDTA), sodium iminodisuccinate (IDS), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, ferric sodium ethylenediaminetetraacetate, potassium ethylenediaminetetraacetate, EDTA tripotassium salt dihydrate, and tetrasodium ethylenediaminetetraacetate dihydrate;

[0008] The activator is one or more of potassium hydroxide, potassium phosphate, potassium hydrogen phosphate, and potassium dihydrogen phosphate (preferably potassium hydroxide), and the mass ratio of the additive to the activator is (1 - 30):(30 - 1), preferably (1 - 10):(10 - 1).

[0009] The specific surface area of the carbon material is 40 - 3000 m 2 / g, preferably 100 - 2000 m 2 / g, more preferably 500 - 1500 m 2 / g.

[0010] The specific preparation steps are as follows:

[0011] 1) Prepare Solution A:

[0012] By weight, dissolve 0.036 - 0.072 parts by mass of the additive and the required parts by mass of the activator in 120 - 180 parts by mass of water to obtain Solution A;

[0013] 2) Prepare Slurry B:

[0014] Add Solution A to the activated carbon material in the required mass ratio and stir for 1 - 10 hours (preferably 4 - 6 hours) to allow the additive to be fully adsorbed by the activated carbon into the pores, obtaining Slurry B;

[0015] 3) Dry Slurry B at 60 - 120 °C for 1 - 24 hours to obtain an activated carbon composite material loaded with the additive and the activator;

[0016] 4) Transfer the dried product from step 3) to an environment of nitrogen or ammonia or a mixed atmosphere of both for the sintering and activation process. Preferably in an ammonia atmosphere, first sinter at 400 - 700 °C for 1 - 10 hours (preferably sinter at 450 - 650 °C for 4 - 6 hours) for the pyrolysis process, and then activate at a temperature greater than 700 - 1200 °C for 1 - 10 hours (preferably activate at 800 - 1000 °C for 4 - 6 hours) to complete the activation process, obtaining a composite carbon material rich in N and K elements.

[0017] The composite carbon material rich in N and K elements obtained by any of the above - mentioned preparation methods

[0018] Application of the composite carbon material rich in N and K elements in the lead - carbon battery electrode.

[0019] By weight, the material composition of the lead - carbon battery electrode is: 500 - 800 parts of lead powder, 1 - 20 parts of the composite carbon material rich in N and K elements, 6 - 10 parts of barium sulfate, and 0.1 - 0.5 parts of polypropylene short fibers with a length of 0.1 - 5 mm and a diameter of 100 nm - 5 μm.

[0020] The preparation process of the lead-carbon battery electrode is as follows: (1) By weight, 500 - 800 parts of lead powder, 1 - 20 parts of the composite carbon material rich in N and K elements, 6 - 10 parts of barium sulfate, and 0.1 - 0.5 parts of polypropylene short fibers with a length of 0.1 - 5 mm and a diameter of 100 nm - 5 μm are stirred and premixed. While stirring, 50 - 100 parts of deionized water are added to the premixed powder, and stirring is continued for 1 - 60 min to obtain a lead paste; (2) The lead paste is scrape-coated onto a metallic lead grid. The lead paste fills the through-holes on the metallic lead grid, and after curing and drying, a negative electrode of the lead-carbon battery is obtained. The curing temperature is 30 - 50 °C, the humidity is 70 - 95%, and the curing time is 10 - 30 hours; the drying temperature is 60 - 120 °C, and the time is 10 - 30 hours.

[0021] The size of the metallic lead grid is 50 - 1000 mm in length, 20 - 80 mm in width, and 0.5 - 4 mm in thickness.

[0022] The lead-carbon battery electrode is a negative electrode of the lead-carbon battery. After assembling the lead-carbon battery, the electrolyte added to the lead-carbon battery is a sulfuric acid solution, and its mass concentration is: 1.1 g / ml - 1.4 g / ml, preferably: 1.249 - 1.301 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active substances other than the metallic lead grid of the negative electrode is 60 - 120:50, preferably 60 - 100:50.

[0023] Advantages of the present invention:

[0024] The C-N bonds on the surface of the carbon material prepared by sintering in an ammonia atmosphere are more stable, which can resist the loss of N element caused by the potential change on the surface of the carbon material during the battery cycle life test, and is more conducive to preparing a carbon material with excellent performance.

[0025] The composite carbon material provided by the present invention is rich in N functional groups and K elements, and belongs to a special additive for the negative electrode of the lead-carbon battery. The presence of N-containing functional groups can inhibit the hydrogen evolution reaction at the negative electrode. In addition to acting as an activator during the preparation process of the composite material, K element can generate more active sites bonded with nitrogen elements on the surface of the carbon material, and can also improve the conductivity of the electrolyte, improve the rate performance and low-temperature capacity retention rate of the battery, and extend the cycle life of the battery. The preparation method of the provided composite carbon material has the characteristics of simple process and easy batch production.

[0026] By introducing an N-containing additive and a K-containing activator into the carbon material at the same time, and through two sinterings in an N-containing atmosphere, a composite carbon material rich in N and K elements is obtained.

[0027] The carbon material with additives and activators adsorbed in the pores is placed in a nitrogen-rich environment such as ammonia or nitrogen for sintering, which can promote the presence of strongly bonded nitrogen elements on the surface of the carbon material, significantly improving the hydrogen evolution problem of the carbon material and ultimately enhancing the battery cycle performance.

[0028] Among the carbon material samples prepared by sintering in an ammonia environment, the combination of carbon and nitrogen elements is more firm, which is more conducive to exerting the performance of the carbon material, and the lead-carbon battery has more excellent cycle stability. Specific implementation mode

[0029] Example 1

[0030] Step 1: Prepare a composite carbon material rich in N and K elements by the following method:

[0031] 1) Prepare solution A:

[0032] Dissolve 0.036 g of ethylenediaminetetraacetic acid and 0.036 g of potassium hydroxide in 150 ml of water to obtain solution A;

[0033] 2) Prepare slurry B:

[0034] Drop solution A into 9 g of activated carbon material and stir for 5 hours to form a slurry B state; the specific surface area of the activated carbon is 1300 m 2 / g; the surface area of the used activated carbon is approximately 11700 m 2 ;

[0035] 3) Dry at 80 °C for 12 hours to obtain an activated carbon composite material loaded with ethylenediaminetetraacetic acid and potassium hydroxide.

[0036] 4) Transfer the product composite material prepared in 3) to a sintering furnace in an ammonia atmosphere. First, sinter at 600 °C for 5 hours, and then raise the temperature to 800 °C for activation for 5 hours to obtain a composite carbon material rich in N and K elements.

[0037] Use the XPS test method to test the atomic number ratios of N and K elements in the composite carbon material sample prepared in Step 1. The test sample is a mixed sample randomly selected from ten non-adjacent sampling points of the carbon material product. The test results show that the atomic number percentage of N element is 0.0543%, and the atomic number percentage of K element is 0.0264%.

[0038] Step 2. Prepare a lead-carbon battery by the following steps: 1. Preparation of the negative electrode: (1) Premix 600 g of lead powder, 9.036 g of the composite carbon material rich in N and K elements prepared in Step 1, 8.4 g of barium sulfate, and 0.3 g of polypropylene short fibers with a length of 5 mm and a diameter of 0.5 - 1.5 μm using a high-speed mixer. While stirring, add 84 g of deionized water to the premixed powder and continue stirring for 10 min to obtain a lead paste; (2) Apply the lead paste onto a metallic lead grid plate with a grid size of 70 mm in length, 50 mm in width, and 2 mm in thickness, and obtain the negative electrode of the lead-carbon battery after curing and drying. 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; 2. Preparation of the positive electrode: Prepare the positive electrode of the lead-acid battery according to the same technological steps as in steps (1) and (2) for preparing the negative electrode, the difference being that no carbon material and additives (i.e., no composite carbon material rich in N and K elements) are added during the preparation of the positive electrode; 3. Preparation of the lead-carbon battery: Arrange three positive electrode plates and two negative electrode plates alternately and parallelly at intervals, and place a PE separator of a commercial lead-acid battery between the positive electrode plate and the negative electrode plate. Connect the two negative electrode plates in parallel by welding and connect the three positive electrode plates in parallel by welding. The total mass of the positive electrode active material (the total mass of the lead paste after drying on the three positive electrode plates) of the lead-acid battery is 20.0 g, and the total mass of the positive electrode active material refers to the total mass of the lead paste contained in the three positive electrode plates connected in parallel by welding. The total mass of the negative electrode active material (the total mass of the lead paste after drying on the two negative electrode plates) is 14.3 g, and the total mass of the negative electrode active material refers to the total mass of the lead paste contained in the two negative electrode plates connected in parallel by welding. The positive and negative electrode grid plates use conventional lead grid plates with a size of 70 mm in length, 50 mm in width, and 2 mm in thickness;

[0039] Prepare a small amount of negative electrode samples respectively by the aforementioned steps, randomly select 10 sampling points on the negative electrode plate for sampling, and dry the samples in an environment of 80 degrees Celsius. Subsequently, mix the samples at the 10 sampling points and conduct XPS tests, and test the atomic number percentages of N element and K element in the sampled samples. The test results show that the atomic number percentage of N element is 0.0026%, and the atomic number percentage of K element is 0.0011%.

[0040] Place the positive and negative electrodes into a tightly assembled battery box with a length of 76 mm, a width of 40 mm, and a height of 100 mm, and inject 83 g of sulfuric acid electrolyte with a density of 1.275 g / ml into the battery box;

[0041] The battery is subjected to a normal temperature life test. The test conditions are as follows: at 25°C, a constant current discharge of 4.2 A is carried out for 59 seconds, a discharge of 18 A for 1 second, and a constant current and constant voltage charge of 6.3 A current and 2.3 V voltage is carried out for 60 seconds. This charge-discharge condition is cycled 3,600 times, and then it is left standing for 40 hours. After 40 hours, the cycle starts again. The termination condition of the life test is that the battery voltage drops below 1.2 V.

[0042] The starting voltage of the assembled internal mixing type battery in the normal temperature full charge state is 2.1924 V. The internal mixing type battery can operate for 18,145 cycles in the normal temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the normal temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery.

[0043] After the cycle life test of the battery is completed, it is fully charged, and then the battery is dissected. 10 sampling points are randomly selected from the negative electrode plate for sampling, and the samples are placed in an 80°C environment for drying. Then, the samples of the 10 sampling points are mixed and subjected to XPS testing. The atomic number ratios of N element and K element in the sampled samples are tested. The test results show that the atomic number percentage of N element is 0.0023%, and the atomic number percentage of K element is 0.0009%.

[0044] Example 2

[0045] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, ethylenediaminetetraacetic acid is replaced with diethylenetriaminepentaacetic acid (DTPA) with the same dosage. The starting voltage of the assembled internal mixing type battery in the normal temperature full charge state is 2.1981 V. The assembled internal mixing type battery can operate for 18,122 cycles in the normal temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the normal temperature cycle life of the internal mixing lead-carbon battery can reach 2.5 times that of the traditional lead-acid battery.

[0046] Example 3

[0047] The process is the same as that of Example 1, except that according to the requirements of Example 1, without changing other conditions, the addition amount of potassium hydroxide is changed to 0.072 g, and correspondingly, the mass of the composite carbon material rich in N and K elements prepared in Step 1 added is changed to 9.072 g. The starting voltage of the assembled internal mixing type battery in the normal temperature full charge state is 2.1439 V. The assembled internal mixing type battery can operate for 14,415 cycles in the normal temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the normal temperature cycle life of the internal mixing lead-carbon battery can reach 2 times that of the traditional lead-acid battery.

[0048] Example 4

[0049] The process is the same as that of Example 1. The difference is that, in accordance with the requirements of Example 1, without changing other conditions, a low specific surface area activated carbon material with a specific surface area of about 500 m 2 / g is used, and the corresponding lead-carbon battery is prepared. The starting voltage of the assembled internal mixing type battery at room temperature under a fully charged state is 2.1636 V. The assembled internal mixing type battery can run for 14,487 cycles in the room temperature life test. Compared with the test results of a conventional lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach twice that of the traditional lead-acid battery life.

[0050] Example 5

[0051] The process is the same as that of Example 1. The difference is that, in accordance with the requirements of Example 1, without changing other conditions, an activated carbon material with a specific surface area of 3000 m 2 / g is used, and with the same mass, the corresponding lead-carbon battery is prepared. The starting voltage of the assembled internal mixing type battery at room temperature under a fully charged state is 2.1903 V. The assembled internal mixing type battery can run for 14,387 cycles in the room temperature life test. Compared with the test results of a conventional lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach twice that of the traditional lead-acid battery life.

[0052] Example 6

[0053] The process is the same as that of Example 1. The difference is that, in accordance with the requirements of Example 1, without changing other conditions, the addition amount of ethylenediaminetetraacetic acid is changed to 0.072 g, and correspondingly, the mass of the composite carbon material rich in N and K elements prepared in Step 1 added is changed to 9.072 g. The starting voltage of the assembled internal mixing type battery at room temperature under a fully charged state is 2.1119 V. The assembled internal mixing type battery can run for 14,433 cycles in the room temperature life test. Compared with the test results of a conventional lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach twice that of the traditional lead-acid battery life.

[0054] Example 7

[0055] The process is the same as that in Example 1, except that, in accordance with the requirements of Example 1, without changing other conditions, the sentence “4) Transfer the product composite material prepared in 3) to a sintering furnace in an ammonia atmosphere and sinter at 600 °C for 5 hours first, and then raise the temperature to 800 °C for activation for 5 hours to obtain a composite carbon material rich in N and K elements.” in step 1 is changed to “4) Transfer the product composite material prepared in 3) to a sintering furnace in a nitrogen atmosphere and sinter at 600 °C for 5 hours first, and then raise the temperature to 800 °C for activation for 5 hours to obtain a composite carbon material rich in N and K elements.” The initial voltage of the assembled internal mixing type battery at room temperature in a fully charged state is 2.1574 V. The assembled internal mixing type battery can operate for 15,897 cycles in the room temperature life test. Compared with the test results of a common lead-acid battery with the same lead element content under the same test conditions (7,223 cycles), the room temperature cycle life of the internal mixing lead-carbon battery can reach twice that of the traditional lead-acid battery life.

[0056] The XPS test method is used to test the atomic number ratios of N and K elements in the composite carbon material sample prepared in step 1. The test sample is a mixed sample randomly selected from ten non-adjacent sampling points of the carbon material product. The test results show that the atomic number percentage of N element is 0.0427%, and the atomic number percentage of K element is 0.0227%.

[0057] The XPS test method is used to sample 10 sampling points from the negative electrode plate prepared in step 2, and the samples are dried in an environment of 80 °C. Then the samples of the 10 sampling points are mixed and subjected to XPS test. The atomic number ratios of N and K elements in the sampled samples are tested. The test results show that the atomic number percentage of N element is 0.0019%, and the atomic number percentage of K element is 0.0012%.

[0058] The battery after the cycle life test is fully charged, and then the battery is dissected. 10 sampling points are randomly selected from the negative electrode plate for sampling, and the samples are dried in an environment of 80 °C. Then the samples of the 10 sampling points are mixed and subjected to XPS test. The atomic number ratios of N and K elements in the sampled samples are tested. The test results show that the atomic number percentage of N element is 0.0012%, and the atomic number percentage of K element is 0.0009%. Analyzing the test results, it can be seen that in the carbon material sample prepared by sintering in an ammonia environment, the combination of carbon element and nitrogen element is more firm, which is more conducive to exerting the performance of the carbon material, thereby improving the cycle stability of the lead-carbon battery.

[0059] Comparative Example 1

[0060] The process is the same as that of Example 1, except that for the lead-acid battery: according to the requirements of Example 1, without changing other conditions, the material preparation in Step 1 is not carried out, and no carbon material is added in the preparation process of the negative electrode in Step 2. The battery prepared under these conditions is a lead-acid battery. The starting voltage of the assembled internal-mixing battery in a fully charged state at room temperature is 2.1233 V, and the battery can be tested for 7223 cycles in terms of operating life under room temperature conditions.

[0061] Comparative Example 2

[0062] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, the material preparation in Step 1 is not carried out, and the composite carbon material rich in N and K elements in the negative electrode material of the lead-carbon battery is replaced with commercial activated carbon, and the specific surface area of the activated carbon is 1300 m 2 / g. The starting voltage of the assembled internal-mixing battery in a fully charged state at room temperature is 2.1273 V, and the battery can be tested for 11415 cycles in terms of operating life under room temperature conditions.

[0063] Comparative Example 3

[0064] The process is the same as that of Example 1, except that the material preparation in Step 1 is not carried out, and for the lead-carbon battery: according to the requirements of Example 1, in Step 2, “1. Preparation of the negative electrode: (1) Premix 600 g of lead powder, 9.036 g of the composite carbon material rich in N and K elements prepared in Step 1, 8.4 g of barium sulfate, and 0.3 g of polypropylene short fibers with a length of 5 mm and a diameter of 0.5 - 1.5 μm using a high-speed mixer. While stirring, add 84 g of deionized water to the premixed powder and continue stirring for 10 min to obtain lead paste” is changed to “1. Preparation of the negative electrode: (1) Premix 600 g of lead powder, 0.036 g of ethylenediaminetetraacetic acid, 0.036 g of potassium hydroxide, 9 g of commercial activated carbon material with a specific surface area of 1300 m 2 / g, 8.4 g of barium sulfate, and 0.3 g of polypropylene short fibers with a length of 5 mm and a diameter of 0.5 - 1.5 μm using a high-speed mixer. While stirring, add 84 g of deionized water to the premixed powder and continue stirring for 10 min to obtain lead paste”. The lead-carbon battery is prepared without changing other conditions. The starting voltage of the assembled internal-mixing battery in a fully charged state at room temperature is 2.1905 V, and the battery can be tested for 10857 cycles in terms of operating life under room temperature conditions. Since the step of pre-adsorbing ethylenediaminetetraacetic acid into its pores using activated carbon is missing, ethylenediaminetetraacetic acid cannot fully cover the active sites on the surface of the activated carbon during the mechanical mixing process, resulting in insufficient suppression of the hydrogen evolution situation in the prepared lead-carbon battery, and thus reducing the number of cycles in the cycle life test.

[0065] Comparative Example 4

[0066] The process is the same as that of Example 1. The difference is that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, change "Step 1. The following method is used to prepare a composite carbon material rich in N and K elements: 1) Prepare Solution A: Dissolve 0.036 g of ethylenediaminetetraacetic acid and 0.036 g of potassium hydroxide in 150 ml of water to obtain Solution A." to "Step 1. The following method is used to prepare a composite carbon material rich in N and K elements: 1) Prepare Solution A: Dissolve 0.9 g of ethylenediaminetetraacetic acid and 0.036 g of potassium hydroxide in 150 ml of water to obtain Solution A.". Since an excessive amount of additive was added in this example, the internal resistance of the battery increased significantly, resulting in an initial voltage of 2.1052 V under full charge at room temperature, and the battery could only run 4766 cycles in the life test under room temperature conditions.

[0067] Comparative Example 5

[0068] The process is the same as that of Example 1. The difference is that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, change "Step 1. The following method is used to prepare a composite carbon material rich in N and K elements: 4) Transfer the product composite material prepared in 3) to a sintering furnace in an ammonia atmosphere and sinter at 600 °C for 5 hours first, and then raise the temperature to 800 °C for activation for 5 hours to obtain a composite carbon material rich in N and K elements." to "Step 1. The following method is used to prepare a composite carbon material rich in N and K elements: 4) Transfer the product composite material prepared in 3) to a sintering furnace in an argon atmosphere and sinter at 600 °C for 5 hours first, and then raise the temperature to 800 °C for activation for 5 hours to obtain a composite carbon material rich in N and K elements.".

[0069] The XPS test method is used to test the atomic number ratios of N and K elements in the composite carbon material sample prepared in Step 1. The test sample is a mixed sample randomly selected from ten non-adjacent sampling points of the carbon material product. The test results show that the atomic number percentage of N element is 0.274%, and the atomic number percentage of K element is 0.0189%.

[0070] Random sampling of the newly prepared additional negative electrode active material in Step 2 is carried out by the same method, and the sample is tested by XPS. The test results show that the atomic number percentage of N element is 0.0012%, and the atomic number percentage of K element is 0.0008%.

[0071] The initial voltage of the battery at room temperature when fully charged is 2.1052V, and it can only run 3921 cycles of life test under room temperature conditions. The battery after the cycle test is dissected, dried, and randomly sampled at 10 points, and then the samples are tested by XPS. The test results show that the atomic percentage of N element is 0.0003%, and the atomic percentage of K element is 0.0006%. Since the carbon material was not sintered in a nitrogen-rich environment such as ammonia or nitrogen during the preparation process, there is a lack of strongly bonded nitrogen elements on the surface of the carbon material, resulting in serious hydrogen evolution of the carbon material and ultimately the decline of the battery cycle performance.

[0072] Comparative Example 6

[0073] The procedure is the same as in Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, change "Step 1. Prepare a composite carbon material rich in N and K elements by the following method: 1) Prepare Solution A: Dissolve 0.036 g of ethylenediaminetetraacetic acid and 0.036 g of potassium hydroxide in 150 ml of water to obtain Solution A;" to not add the activator potassium hydroxide: "Step 1. Prepare a composite carbon material containing N element by the following method: 1) Prepare Solution A: Dissolve 0.036 g of ethylenediaminetetraacetic acid in 150 ml of water to obtain Solution A;"

[0074] Use the XPS test method to test the atomic ratio of N and K elements in the composite carbon material sample prepared in Step 1. The test sample is a mixed sample randomly selected from ten non-adjacent sampling points of the carbon material product. The test results show that the atomic percentage of N element is 0.0113%, and the atomic percentage of K element is 0.0000%.

[0075] Randomly sample the newly prepared additional negative electrode active material in Step 2 in the same way, and test the sample by XPS. The test results show that the atomic percentage of N element is 0.0005%, and the atomic percentage of K element is 0.0000%.

[0076] The initial voltage of the battery at room temperature in a fully charged state is 2.1162V, and it can only run 3831 cycles in the life test under room temperature conditions. After the cycle life test of the battery is completed, it is fully charged, and then the battery is dissected. 10 sampling points are randomly selected from the negative electrode plate for sampling, and the samples are dried in an environment of 80 degrees Celsius. Then the samples at the 10 sampling points are mixed and subjected to XPS testing. The atomic number ratios of N element and K element in the sampled samples are tested. The test results show that the atomic percentage of N element is 0.0003%, and the atomic percentage of K element is 0.0000%. Since K ions are not introduced during the preparation process of the carbon material, the carbon material is not activated, and there are no active sites on the surface of the carbon material that can bond with nitrogen elements, resulting in serious hydrogen evolution of the carbon material and ultimately leading to a decline in the cycle performance of the battery.

[0077] Comparative Example 7

[0078] The process is the same as that of Example 1, except that for the lead-carbon battery: according to the requirements of Example 1, without changing other conditions, change "Step 1. Prepare a composite carbon material rich in N and K elements by the following method: 1) Prepare Solution A: Dissolve 0.036 g of ethylenediaminetetraacetic acid and 0.036 g of potassium hydroxide in 150 ml of water to obtain Solution A;" to not add ethylenediaminetetraacetic acid: "Step 1. Prepare a composite carbon material containing N and K elements by the following method: 1) Prepare Solution A: Dissolve 0.036 g of potassium hydroxide in 150 ml of water to obtain Solution A;".

[0079] The XPS test method is used to test the atomic number ratios of N element and K element in the composite carbon material sample prepared in Step 1. The test sample is a mixed sample randomly selected from ten non-adjacent sampling points of the carbon material product. The test results show that the atomic percentage of N element is 0.0008%, and the atomic percentage of K element is 0.0214%.

[0080] Random sampling of the newly prepared additional negative electrode active material in Step 2 is carried out by the same method, and the sample is subjected to XPS testing. The test results show that the atomic percentage of N element is 0.0002%, and the atomic percentage of K element is 0.0010%.

[0081] The initial voltage of the battery at room temperature in a fully charged state is 2.1162V. Under room temperature conditions, it can only run 3,831 cycles of life tests. After the cycle life test of the battery is completed, it is fully charged, and then the battery is dissected. 10 sampling points are randomly selected from the negative electrode plate for sampling, and the samples are dried in an environment of 80 degrees Celsius. Subsequently, the samples at the 10 sampling points are mixed and subjected to XPS testing. The atomic number ratios of N element and K element in the sampled samples are tested. The test results show that the atomic percentage of N element is 0.0001%, and the atomic percentage of K element is 0.0007%. Due to the lack of nitrogen element doping on the surface during the preparation process of the carbon material, the hydrogen evolution of the carbon material is serious, which ultimately leads to the decline of the battery cycle performance.

Claims

1. A preparation method of a composite carbon material rich in N and K elements, characterized in that, Using activated carbon as a carrier, under the combined action of an additive and an activator, a composite carbon material rich in N and K elements is prepared; The method includes the following steps: 1) Prepare solution A: By weight, dissolve 0.036 - 0.072 parts by mass of the additive and the required parts by mass of the activator in 120 - 180 parts by mass of water to obtain solution A; 2) Prepare slurry B: Add solution A to the activated carbon material in the required mass ratio, and stir for 1 - 10 hours to allow the additive to be fully adsorbed into the pores of the activated carbon to obtain slurry B; 3) Dry slurry B at 60 - 120 °C for 1 - 24 hours to obtain an activated carbon composite material loaded with the additive and the activator; 4) Transfer the dried product from step 3) to an ammonia atmosphere for the sintering and activation process. First, sinter at 400 - 700 °C for 1 - 10 hours for the pyrolysis process, and then activate at a temperature greater than 700 - 1200 °C for 1 - 10 hours to complete the activation process, obtaining a composite carbon material rich in N and K elements; The mass ratio of the additive to the activated carbon is (0.004 - 0.008):1; the additive is one or more of ethylenediaminetetraacetic acid, tetraammonium ethylenediaminetetraacetate, ethylenediaminetetraacetic acid, sodium iminodisuccinate, diethylenetriaminepentaacetic acid, aminotriacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, ferric sodium ethylenediaminetetraacetate, potassium ethylenediaminetetraacetate, EDTA tripotassium salt dihydrate, tetrasodium ethylenediaminetetraacetate dihydrate; The activator is one or more of potassium hydroxide, potassium phosphate, monopotassium phosphate, dipotassium phosphate, and the mass ratio of the additive to the activator is (1 - 30):(30 - 1).

2. The method for preparing the composite material according to claim 1, wherein: The activator is potassium hydroxide, and the mass ratio of the additive to the activator is (1 - 10):(10 - 1).

3. The method for preparing the composite material according to claim 1, wherein: The specific surface area of the carbon material is 40 - 3000 m 2 / g.

4. The method for preparing the composite material according to claim 1, wherein: The specific surface area of the carbon material is 100 - 2000 m 2 / g.

5. The method for preparing the composite material according to claim 1, wherein: The specific surface area of the carbon material is 500 - 1500 m 2 / g.

6. The preparation method of the composite material according to claim 1, characterized in that: In step 2), the stirring time is 4 - 6 hours.

7. The method for preparing the composite material according to claim 1, wherein: In step 4), the sintering conditions are sintering at 450 - 650 °C for 4 - 6 hours; the activation conditions are activation at 800 - 1000 °C for 4 - 6 hours.

8. A composite carbon material rich in N and K elements prepared by the method for preparing the composite material according to any one of claims 1 - 7.

9. Application of the composite carbon material rich in N and K elements according to claim 8 in the lead-carbon battery electrode.

10. The application according to claim 9, wherein: By weight, the material composition of the lead-carbon battery electrode is: 500 - 800 parts of lead powder, 1 - 20 parts of the composite carbon material rich in N and K elements, 6 - 10 parts of barium sulfate, 0.1 - 0.5 parts of polypropylene short fibers with a length of 0.1 - 5 mm and a diameter of 100 nm - 5 μm.

11. The application according to claim 9, wherein: The preparation process of the lead-carbon battery electrode is as follows: (1) By weight, 500-800 parts of lead powder, 1-20 parts of the composite carbon material rich in N and K elements, 6-10 parts of barium sulfate, and 0.1-0.5 parts of polypropylene short fibers with a length of 0.1-5 mm and a diameter of 100 nm-5 μm are stirred and premixed. While stirring, 50-100 parts of deionized water are added to the premixed powder, and stirring is continued for 1-60 min to obtain a lead paste; (2) The lead paste is scraped onto a metallic lead grid. The lead paste fills the through holes on the metallic lead grid, and after curing and drying, a negative electrode of the lead-carbon battery is obtained. The curing temperature is 30-50 °C, the humidity is 70-95%, and the curing time is 10-30 hours; the drying temperature is 60-120 °C, and the time is 10-30 hours.

12. The application according to claim 11, wherein: The size of the metallic lead grid is 50-1000 mm in length, 20-80 mm in width, and 0.5-4 mm in thickness.

13. The application according to any one of claims 9-12, characterized in that: The lead-carbon battery electrode is a negative electrode of the lead-carbon battery. After assembling the lead-carbon battery, the electrolyte added to the lead-carbon battery is a sulfuric acid solution with a mass concentration of 1.1 g / ml - 1.4 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active substances of the negative electrode except the metallic lead grid is 60-120:

50.

14. The application according to claim 13, wherein: The lead-carbon battery electrode is a negative electrode of the lead-carbon battery. After assembling the lead-carbon battery, the electrolyte added to the lead-carbon battery is a sulfuric acid solution with a mass concentration of 1.249-1.301 g / ml, and the mass ratio of the sulfuric acid electrolyte to the total mass of the active substances of the negative electrode except the metallic lead grid is 60-100:50.