A modified carbon material for lead-acid battery, preparation method thereof and negative electrode lead paste

Abstract

A modified carbon material for lead-acid batteries, the modified carbon material being a carbon material doped with Ba element and simultaneously doped and modified with N element on its surface, labeled as BN carbon material, having an average particle size of less than 10 μm and a specific surface area of 10-500 m2 / g. In the present invention, the modified carbon material is added to the additive of the negative electrode lead paste, effectively inhibiting the sulfation phenomenon of the negative electrode and prolonging the service time of the lead-acid battery.

Description

Technical Field

[0001] The invention relates to a modified carbon material for a lead-acid battery, a preparation method thereof and a negative electrode lead paste, and belongs to the technical field of lead-acid batteries. Background Art

[0002] The main components of lead-acid batteries include positive plates, negative plates, electrolyte, separators and battery cases. The plates made of lead paste coated on the grid are the key factors affecting the electrical performance of the battery. In the negative plate of a lead-acid battery, the main active material is spongy lead. When the battery is discharged, the negative electrode loses electrons as the anode, and the elemental lead is oxidized to Pb 2+ and SO in the electrolyte 4 2- The reaction generates PbSO with low solubility 4 , deposited in the negative plate. When the battery is charged, the negative electrode acts as a cathode, and the PbSO deposited in it 4 Gradually reduced to SO 4 2- In essence, the reaction of the negative electrode during the discharge of a lead-acid battery is a dissolution-deposition process. If there are too few lead sulfate nuclei in the negative plate of the battery, the generated PbSO 4 The crystals grow slowly to form larger particles. At the same time, if the battery is in a state of being fully charged or even undercharged for a long time, the PbSO in the negative plate 4 It will also continue to recrystallize to form crystals with complete crystal shape and larger size, resulting in a decrease in its electrochemical activity. This phenomenon is called "negative plate sulfation" in the industry.

[0003] Generally speaking, additives such as barium sulfate, carbon black, lignin, and humic acid are added to the negative plate of lead-acid batteries during the production process to reduce the generation of large lead sulfate crystals in the negative active material during use, and to improve the conductivity between the active materials and maintain a larger specific surface area to a certain extent. For example, in the formula of the negative lead paste of traditional starting lead-acid batteries, in addition to basic raw materials such as lead powder, pure water and dilute sulfuric acid, it also includes additives such as short fibers, barium sulfate, sodium lignin sulfonate, humic acid and carbon black, which to a certain extent delay the occurrence of sulfation of the negative plate. However, with the development of the domestic and foreign automobile industry and the increase in the number of cars, the operating conditions of lead-acid batteries have also changed to a certain extent, and the performance requirements have become more stringent. In particular, cars are frequently started in urban traffic, and starting lead-acid batteries for cars are in a light-load charge and discharge state for a long time, which requires a higher charging capacity of the negative plate active material. Traditional additives alone are difficult to meet the current working conditions of lead-acid batteries for charging recovery capacity and light-load state life requirements. Summary of the invention

[0004] The present invention overcomes the disadvantages of the prior art and provides a modified carbon material for lead-acid batteries and a method for preparing a negative electrode lead paste. The modified carbon material is added to the additive of the negative electrode lead paste to effectively inhibit the sulfation of the negative electrode and extend the service life of the lead-acid battery.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A modified carbon material for lead-acid batteries, wherein the modified carbon material is a carbon material doped with Ba element and doped and modified on the surface with N element, marked as BN carbon material, with an average particle size of less than 10 μm and a specific surface area of ​​10-500 m 2 / g.

[0007] A method for preparing a modified carbon material for a lead-acid battery, the method comprising the following steps:

[0008] a. Weigh a certain amount of Ba(OH) 2 , add to the solvent, stir thoroughly until completely dissolved, and obtain Ba(OH) 2 Solution, Ba(OH) 2 The concentration of the solution is 0.01-5wt%;

[0009] b. Weigh a certain amount of basic carbon material and add it to Ba(OH) 2 In the solution, a turbid liquid of a barium-doped carbon material precursor is obtained, the turbid liquid is fully stirred for 0.1-300 minutes, and then allowed to stand for 0.1-12 hours;

[0010] c. drying the barium-doped carbon material precursor turbid liquid at 40-120° C. for 1-24 h to obtain a barium-doped carbon material precursor;

[0011] d. heating the obtained barium-doped carbon material precursor powder to 150-300° C. and calcining the powder at the temperature for 0.5-6 h to obtain a barium-doped carbon material;

[0012] e. Grind and mix the obtained barium-doped carbon material and nitrogen source material evenly, and control the mass ratio of the barium-doped carbon material to the nitrogen source material to be 100:(0.1-20) to obtain a BN carbon material precursor powder, and pass it through a 200-mesh sieve;

[0013] f. heating the obtained BN carbon material precursor powder to 400-800° C. and calcining it at this temperature for 0.5-6 hours to obtain BN carbon material particles;

[0014] g. Grind the obtained BN carbon material particles to obtain BN carbon material for lead-acid batteries.

[0015] In the above-mentioned method for preparing the modified carbon material for lead-acid batteries, in step a, the solvent is one or more of methanol, ethanol and water.

[0016] The method for preparing the modified carbon material for lead-acid batteries, in step b, the basic carbon material is one or more of carbon black, graphite and activated carbon, and the basic carbon material is reacted with Ba(OH) 2 The mass ratio is controlled at 100:(0.1-10).

[0017] In the above-mentioned method for preparing the modified carbon material for lead-acid batteries, in the steps d and f, during the heat preservation and roasting, the barium-doped carbon material precursor or the BN carbon material precursor is placed in a crucible with a cover, or in a protective atmosphere, wherein the protective atmosphere is N 2 , He and Ar.

[0018] In the above-mentioned method for preparing the modified carbon material for lead-acid batteries, in the step e, the nitrogen source material is one or more of urea, cyanamide, dicyandiamide, thiourea and melamine.

[0019] A negative electrode lead paste for a lead-acid battery, wherein the above-mentioned modified carbon material is added to the negative electrode lead paste, and the negative electrode lead paste comprises components in the following mass addition ratio: lead powder: short fiber: lignin: humic acid: barium sulfate: BN carbon material: pure water: dilute sulfuric acid = 100: (0.05-0.5): (0-1.0): (0-1.0): (0-2.0): (0.1-1.0): (10-15): (6-10).

[0020] The negative electrode lead paste of the lead-acid battery has a density of 3.5-4.5 g / cm 3 .

[0021] The negative electrode lead paste of the lead-acid battery has an oxidation degree of 60-98%, wherein the mass ratio of PbO to Pb is (60-98):(40-2); the short fibers are one or more of acrylic fibers, polyester fibers and polyacrylonitrile fibers, and have a length of 1-15 mm.

[0022] The negative electrode lead paste of the lead-acid battery, the conductivity of the pure water is ≤0.33μs / cm, the dilute sulfuric acid is analytically pure, and its density is 1.1-1.6g / cm 3 .

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

[0024] After the modified carbon material prepared by the present invention is dispersed in the negative electrode active material, it can play a role in increasing the electron migration speed when there is too much lead sulfate, thereby improving the overall conductivity of the negative electrode. The battery added with the modified carbon material of the present invention has a higher light load life and static charge acceptance than the ordinary battery (no BN carbon material is added to the negative electrode lead paste). For example, without reducing the discharge capacity, the battery's 0°C charge acceptance is increased by more than 10%, and the light load life is increased by more than 20%.

[0025] The preparation method of the modified carbon material of the present invention uses only the existing commercially stable carbon material as the basic carbon material, uniformly distributes the Ba element by impregnation, effectively deposits the Ba element on the surface of the carbon material after drying and roasting, and modifies the functional groups on the surface of the carbon material by mixing and roasting at high temperature to generate gC by N element. 3 N 4 , avoid the introduction of Fe, Co, Ni and other elements and Cl that may have adverse effects on lead-acid batteries - 、NO 3 - Plasma. The preparation process eliminates the need for acid washing and alkali washing of materials, reduces energy consumption and water consumption, and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the XRD test result diagram of BN carbon material;

[0027] Figure 2 This is the element mapping diagram of SEM and EDS tests of BN carbon materials. DETAILED DESCRIPTION

[0028] According to the present invention, after Ba element is dispersed as the main doping element on the surface of the basic carbon material, it can be deposited in situ with sulfuric acid in the electrolyte to generate barium sulfate with a similar size to that of the lead sulfate unit cell, thereby guiding the lead sulfate to be deposited on the surface of the basic carbon material. Since the growth process of the lead sulfate crystal is affected by the surface energy of the carbon material, the crystal defects increase, and the lead sulfate is organically combined with the carbon material with higher conductivity, so that the reduction barrier of the lead sulfate is reduced during charging, and the lead sulfate is more easily reduced, thereby improving its reduction efficiency.

[0029] During the calcination of the nitrogen source material and the Ba-doped carbon material, the nitrogen element will modify the carbon-oxygen functional groups such as C-OH and C=O on the surface of the carbon material to form nitrogen-containing functional groups, thus preventing the carbon-oxygen groups from reacting with H in the electrolyte. + The hydrogen evolution effect caused by attraction reduces the water consumption of lead-acid batteries during use. At the same time, polycondensation occurs on the surface of the carbon material to form a portion of graphite phase carbon nitride (gC 3 N 4 ). 3 N4 The unique electronic structure and thermodynamic stability of the carbon material have a very suitable semiconductor band edge position, excellent high temperature resistance, acid and alkali resistance and good specific surface area, making it very suitable as a carrier for non-metallic catalysts and metal catalysts and nucleating agents. 3 N 4 When the cathode reduction reaction occurs on the negative plate of the lead-acid battery, it will reduce the local reduction reaction energy barrier and promote the free Pb 2+ Reduced to Pb, thereby slowing down the 4 The reaction difficulty caused by the reduced electrochemical activity of the grains themselves is conducive to avoiding "negative plate sulfation" and plays a role in extending the service life of lead-acid batteries.

[0030] The addition ratio of BN carbon material in the negative electrode lead paste of the present invention is controlled, and the mass addition ratio is: lead powder: short fiber: lignin: humic acid: barium sulfate: BN carbon material: pure water: dilute sulfuric acid = 100: (0.05-0.5): (0-1.0): (0-1.0): (0-2.0): (0.1-1.0): (10-15): (6-10). The main function of BN carbon material is nucleating agent and stabilizing catalyst. If the addition ratio is too small, BN carbon material cannot be evenly and effectively dispersed in the lead paste, and the effect of extending the service life of the battery cannot be achieved; if the addition amount is too large, because BN carbon material itself does not act as a substance for electrochemical reaction, it will cause the specific energy of the plate to be significantly reduced.

[0031] The present invention controls the average particle size of the BN carbon material to be less than 10 μm, and the specific surface area thereof is 10-500 m 2 / g. When the particle size of the BN carbon material is too large, it will cause serious uneven dispersion in the negative electrode active material, and the area where it can work is too low, and the desired effect cannot be achieved. When the particle size of the material is too small, on the one hand, the production cost of grinding and screening will increase, and at the same time it may be excessively surrounded by lead sulfate grains, resulting in reduced effect. In addition, the specific surface area of ​​the BN carbon material is too small, and the effective reaction area is too low, so the material cannot achieve the desired effect. A large specific surface area means a smaller pore size and a higher proportion of surface defects. The increased hydrogen evolution effect will increase water consumption and reduce the service life of the battery, and the production cost will also increase accordingly.

[0032] The present invention will be further described below in conjunction with the embodiments.

[0033] The present invention modifies the basic carbon material with Ba and N elements in sequence, and generates a certain amount of thermodynamically more stable 3-s-triazine ring (C 6 N 7 ) is the structural unit of gC 3 N 4, and obtain modified carbon material (BN carbon material). The specific preparation process is as follows:

[0034] ①Weigh a certain amount of Ba(OH) 2 , add to the solvent, stir thoroughly until completely dissolved, and obtain Ba(OH) 2 Solution, Ba(OH) 2 The concentration of the solution is 0.01-5wt%; the solvent is one or more of methanol, ethanol, and water;

[0035] ② Weigh a certain amount of basic carbon material and add it to Ba(OH) 2 In the solution, a turbid solution of a barium-doped carbon material precursor is obtained, and the basic carbon material and Ba(OH) 2 The mass ratio of is controlled at 100:(0.1-10), the turbid liquid is fully stirred for 0.1-300 minutes, and then allowed to stand for 0.1-12 hours; the basic carbon material is one or more of carbon black, graphite and activated carbon;

[0036] ③ Dry the stationary barium-doped carbon material precursor turbid liquid at 40-120° C. for 1-24 hours to obtain a barium-doped carbon material precursor;

[0037] ④ The obtained barium-doped carbon material precursor powder is heated to 150-300° C. and calcined for 0.5-6 h to obtain a barium-doped carbon material; during the calcination, the barium-doped carbon material precursor is placed in a crucible with a lid, or in a protective atmosphere, wherein the protective atmosphere is N 2 , He and Ar;

[0038] ⑤ Grinding and mixing the obtained barium-doped carbon material and the nitrogen source material, wherein the mass ratio of the barium-doped carbon material to the nitrogen source material is controlled at 100:(0.1-20), to obtain a BN carbon material precursor powder; wherein the nitrogen source material is one or more of urea, cyanamide, dicyandiamide, thiourea and melamine;

[0039] ⑥ The obtained BN carbon material precursor powder is heated to 400-800°C and calcined for 0.5-6h to obtain BN carbon material particles; during the calcination, the BN carbon material precursor powder is placed in a crucible with a lid, or in a protective atmosphere, wherein the protective atmosphere is N 2 , He and Ar;

[0040] ⑦ Grind the obtained BN carbon material particles to obtain BN carbon material for lead-acid batteries.

[0041] The prepared BN carbon material is added to the negative electrode lead paste as an additive material. The preparation method of the negative electrode plate includes the following steps:

[0042] ① The lead powder, short fiber, lignin, humic acid, barium sulfate and BN carbon material are stirred and mixed uniformly in a mass ratio of 100: (0.05-0.5): (0-1.0): (0-1.0): (0-2.0): (0.1-1.0);

[0043] ② Add water and aqueous sulfuric acid solution to the mixture obtained in step ① in sequence, and stir them for 1-60 minutes to obtain negative electrode lead paste for lead-acid batteries.

[0044] Example 1

[0045] Weigh 0.5g of Ba(OH) 2 , add to 100g pure water, stir thoroughly until completely dissolved, and obtain Ba(OH) 2 Weigh 100g of activated carbon and add it to Ba(OH) 2 The solution was stirred for 60 min and then allowed to stand for 1 h. The turbid solution was dried at 90 °C for 6 h to obtain a barium-doped carbon material precursor. The barium-doped carbon material precursor was ground and placed in a covered crucible and heated at N 2 The obtained barium-doped carbon material was calcined at 220°C for 2 h under protection to obtain a barium-doped carbon material. The obtained barium-doped carbon material was ground and mixed with 10.0 g of urea, and then placed in a covered crucible and heated under N 2 The mixture was calcined at 550°C for 1 hour under protection. The obtained particles were ground into powder with an average particle size of less than 10 μm to obtain BN carbon material for lead-acid batteries.

[0046] The obtained BN carbon material was subjected to XRD, SEM and EDS analysis, and the results were as follows: Figure 1 and Figure 2 shown. Figure 1 This is the XRD test result of BN carbon material. It can be seen from the figure that the material mainly shows the amorphous characteristics of carbon material, indicating that the introduction and modification of a small amount of Ba and N elements did not lead to changes in the crystalline characteristics of the basic carbon material itself. 3 N 4 The substances are distributed relatively evenly, so their characteristic peaks do not appear.

[0047] Figure 2 The SEM and EDS test element mapping diagrams of BN carbon materials, where A is the SEM morphology of the test area, and B, C, and D are the element mapping diagrams of C, N, and Ba, respectively. It can be seen that the C, N, and Ba elements are evenly distributed in the BN carbon material.

[0048] Example 2

[0049] 1000 kg of lead powder with an oxidation degree of 80%, 0.6 kg of polyester fiber with a length of 3 mm, 2.0 kg of sodium lignin sulfonate, 3.0 kg of humic acid, 5.0 kg of fine barium sulfate, 3.0 kg of BN carbon material (D50 particle size of 6.16 μm, specific surface area of ​​142 m 2 / g) were evenly mixed, and 110kg of pure water and 85kg of a density of 1.4g / cm 3 The required negative lead paste is obtained by stirring, and then the negative plate is made. The negative plate is welded with the positive plate and the PE separator. After formation, a 12V36Ah lead-acid test battery is obtained. The battery number is 2#, and the reserve capacity, 0℃ charge acceptance and light load life tests are carried out. The experimental results are shown in Table 1.

[0050] Example 3

[0051] 1000 kg of lead powder with an oxidation degree of 80%, 0.6 kg of polyester fiber with a length of 3 mm, 2.0 kg of sodium lignin sulfonate, 3.0 kg of humic acid, 5.0 kg of fine barium sulfate, 5.0 kg of BN carbon material (D50 particle size of 6.16 μm, specific surface area of ​​142 m 2 / g) were evenly mixed, and 110kg of pure water and 85kg of a density of 1.4g / cm 3 The required negative lead paste is obtained by stirring, and then the negative plate is made. The negative plate is welded with the positive plate and the PE separator. After formation, a 12V36Ah lead-acid test battery is obtained. The battery number is 3#, and the reserve capacity, 0℃ charge acceptance and light load life tests are carried out. The experimental results are shown in Table 1.

[0052] Comparative Example 1

[0053] 1000kg of lead powder with an oxidation degree of 80%, 0.6kg of polyester fiber with a length of 3mm, 2.0kg of sodium lignin sulfonate, 3.0kg of humic acid, 5.0kg of fine barium sulfate, and 3.0kg of basic carbon material were uniformly mixed, and 110kg of pure water and 85kg of 1.4g / cm density were added in sequence. 3 The required negative lead paste is obtained by stirring, and then the negative plate is made. The negative plate is welded with the positive plate and the PE separator. After formation, a 12V36Ah lead-acid test battery is obtained. The battery number is 1#, and the reserve capacity, 0℃ charging acceptance and light load life tests are carried out. The experimental results are shown in Table 1.

[0054] Table 1 Comparison of battery performance made in Example 1 and Example

[0055] Battery ID Reserve capacity (min) Charge acceptance (A) Light load life (times) 1# 61 10.63 1934 2# 62 11.77 2461 3# 61 12.63 2849

[0056] As shown in Table 1, the lead-acid battery manufactured by the negative electrode lead paste formula of the present invention has a 10% higher charge acceptance at 0°C and a 25% higher light load life while ensuring that the discharge capacity does not decrease.

Claims

1. A modified carbon material for lead-acid batteries, Features: The modified carbon material is a carbon material doped with Ba element and doped and modified on its surface with N element, marked as BN carbon material, with an average particle size of less than 10 μm and a specific surface area of ​​10-500 m 2 / g; The preparation method of the modified carbon material comprises the following steps: a. Weigh a certain amount of Ba(OH) 2 , add it to the solvent and stir it thoroughly until it is completely dissolved to obtain Ba(OH) 2 Solution, Ba(OH) 2 The concentration of the solution is 0.01-5 wt %; b. Weigh a certain amount of basic carbon material and add it to Ba(OH) 2 In the solution, a turbid liquid of a barium-doped carbon material precursor is obtained, the turbid liquid is fully stirred for 0.1-300 minutes, and then allowed to stand for 0.1-12 hours; c. drying the barium-doped carbon material precursor turbid liquid at 40-120° C. for 1-24 h to obtain a barium-doped carbon material precursor; d. heating the obtained barium-doped carbon material precursor powder to 150-300° C. and calcining the powder at the temperature for 0.5-6 h to obtain a barium-doped carbon material; e. Grind and mix the obtained barium-doped carbon material and nitrogen source material evenly, and control the mass ratio of the barium-doped carbon material to the nitrogen source material to be 100:(0.1-20) to obtain BN carbon material precursor powder, and pass it through a 200-mesh sieve; f. heating the obtained BN carbon material precursor powder to 400-800° C. and calcining it at this temperature for 0.5-6 hours to obtain BN carbon material particles; g. Grind the obtained BN carbon material particles to obtain BN carbon material for lead-acid batteries.

2. The modified carbon material for lead-acid batteries according to claim 1, Features: In step a, the solvent is one or more of methanol, ethanol and water.

3. The modified carbon material for lead-acid batteries according to claim 2, Features: In the step b, the basic carbon material is one or more of carbon black, graphite and activated carbon, and the basic carbon material and Ba(OH) 2 The mass ratio is controlled at 100:(0.1-10).

4. The modified carbon material for lead-acid batteries according to claim 3, Features: In the steps d and f, during the heat preservation and roasting, the barium-doped carbon material precursor or the BN carbon material precursor is placed in a crucible with a cover, or in a protective atmosphere, wherein the protective atmosphere is N 2 , He and Ar.

5. The modified carbon material for lead-acid batteries according to claim 4, Features: In the step e, the nitrogen source material is one or more of urea, cyanamide, dicyandiamide, thiourea and melamine.

6. A negative electrode lead paste for a lead-acid battery, Features: The negative electrode lead paste is added with the modified carbon material as claimed in claim 1, and the negative electrode lead paste includes components in the following mass addition ratio: lead powder: short fiber: lignin: humic acid: barium sulfate: BN carbon material: pure water: dilute sulfuric acid = 100: (0.05-0.5): (0-1.0): (0-1.0): (0-2.0): (0.1-1.0): (10-15): (6-10).

7. The negative electrode lead paste for the lead-acid battery according to claim 6, Features: The density of the negative electrode lead paste is 3.5-4.5 g / cm 3 .

8. The negative electrode lead paste for the lead-acid battery according to claim 7, Features: The oxidation degree of the lead powder is 60-98%, wherein the mass ratio of PbO to Pb is (60-98): (40-2); the short fiber is one or more of acrylic fiber, polyester fiber and polyacrylonitrile fiber, and the length is 1-15 mm.

9. The negative electrode lead paste for the lead-acid battery according to claim 8, Features: The conductivity of the pure water is ≤0.33μs / cm, the dilute sulfuric acid is analytically pure, and its density is 1.1-1.6g / cm 3 .

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