Lead monatomic / nanoparticle anchored carbon aerogel as well as preparation method and application thereof

Abstract

The invention discloses lead monatomic / nanoparticle anchored carbon aerogel as well as a preparation method and application thereof, and belongs to the field of battery materials and energy storage. The preparation method of the carbon aerogel comprises the following steps: S1, mixing lead salt and molten salt to form a lead salt-molten salt mixture, then adding crushed agricultural and forestry biomass, and uniformly mixing to obtain a precursor mixture; and S2, carrying out low-temperature pyrolysis on the precursor mixture, and then carrying out high-temperature pyrolysis. According to the invention, the lead-containing mixed molten salt and the biomass raw material are mixed according to an accurate proportion, and then heat treatment is carried out in a specific temperature range and in a controllable atmosphere, so that construction of the carbon aerogel and synchronous loading of lead monatomic / nanoparticles are realized, and the prepared material shows excellent electrochemical performance and is suitable for industrial production. Particularly, the excellent performance of inhibiting hydrogen evolution reaction and improving sulfation inhibition capability of the lead-carbon negative electrode effectively improves the cycling stability of the lead-carbon battery, and the excellent performance has a remarkable effect of prolonging the service life of the battery.

Description

Technical Field

[0001] The present invention relates to the fields of battery materials and energy storage, and particularly to a lead single-atom / nanoparticle-anchored carbon aerogel and its preparation method and application. Background Art

[0002] Due to the low cost, good recyclability, and extensive application background of lead-acid batteries, they occupy a crucial position in the global battery market. Especially in the field of renewable energy, lead-acid batteries show strong competitiveness in energy storage systems because they are not restricted by volume and mass energy density. However, with the widespread application of renewable energy, the performance requirements for lead-acid batteries are becoming increasingly stringent, especially in terms of the anti-sulfation ability of the negative electrode material and the improvement of cycle life, facing many challenges. The sulfation problem is one of the main reasons for the performance decline of the negative electrode of lead-acid batteries. Therefore, researchers have proposed introducing carbon materials into the negative electrode of lead-acid batteries to improve the cycle stability of the negative electrode. Carbon materials can not only improve the conductivity of the battery but also inhibit the occurrence of lead sulfation by providing more active sites. Commonly used carbon materials include carbon in one-dimensional, two-dimensional, and three-dimensional structures, such as carbon black, carbon fiber, activated carbon, and graphene-like materials. Especially three-dimensional carbon materials are generally considered to be able to effectively alleviate the sulfation problem of lead-acid batteries due to their large specific surface area and good structural stability.

[0003] Although the application of carbon materials has improved the performance of lead-acid batteries to a certain extent, the existing carbon materials still have the following important problems that need to be further optimized. (1) High cost: The production cost of high-purity activated carbon or special carbon nanomaterials is relatively high, which limits their application in large-scale lead-acid batteries; (2) Poor pore mass transfer performance: Although many carbon materials have a large specific surface area, their pore structures are not always suitable for the efficient transmission of lead ions; (3) Uneven lead loading: The lead loading of existing carbon materials usually shows uneven distribution, and this uneven loading distribution leads to a relatively high hydrogen evolution rate of carbon materials, thereby affecting the performance and service life of the battery; (4) Weak connection between lead loading and carbon: The binding force between traditional carbon materials and lead is weak, and this loose interface connection hinders the effective conduction of charge and is prone to carbon floating phenomenon during long-term use, thus affecting the stability of the battery.

[0004] Chinese invention patent CN118183683A provides a preparation method and application of a mesoporous fluorine-doped carbon material. This material inhibits the hydrogen evolution reaction through fluorine doping, and has certain advantages due to its mesoporous structure providing a higher mass transfer rate. However, the raw material cost of this technology is relatively high, and the preparation process is complex, making it difficult to be applied on a large scale.

[0005] Chinese invention patent CN105958076A relates to a modified carbon material, a preparation method thereof, a negative electrode lead paste, a plate and a lead-carbon battery. In this method, biomass treated with an inorganic strong acid and / or an inorganic strong base solution is placed in an aqueous solution containing a metal salt with a high hydrogen evolution overpotential, and finally a modified carbon material is obtained by calcination. Although this method can improve the binding force of the loaded species in the carbon material, it will also bring problems such as uneven aggregation of lead nanoparticles and poor pore mass transfer effect.

[0006] Chinese invention patent CN107742696A provides a preparation method for a carbon-based additive for a lead-carbon negative electrode. The carbon material is sensitized, activated, and electrolessly plated to achieve uniform lead loading, which can significantly reduce the hydrogen evolution reaction rate of the carbon material, thereby prolonging the cycle life of the lead-carbon battery. However, for the lead-carbon composite material obtained by the electroless plating method, the combination of the loaded lead and the carbon matrix is not tight enough, and the phenomenon of floating carbon is likely to occur. Summary of the Invention

[0007] Object of the Invention: The first object of the present invention is to provide a lead single atom / nanoparticle anchored carbon aerogel having uniform lead loading, high stability, strong electrical conductivity and a pore structure conducive to rapid ion diffusion, thereby being able to improve the electrochemical performance of the negative electrode material of the lead-carbon battery, extend its service life, and improve its cycle efficiency. The second object of the present invention is to provide a preparation method for the above-mentioned lead single atom / nanoparticle anchored carbon aerogel. The third object of the present invention is to provide the application of the above-mentioned lead single atom / nanoparticle anchored carbon aerogel.

[0008] Technical Solution: The preparation method for the lead single atom / nanoparticle anchored carbon aerogel provided by the present invention includes the following steps:

[0009] S1. Mix a lead salt and a molten salt to form a lead salt-molten salt mixture, and then add crushed agricultural and forestry biomass, and mix evenly to obtain a precursor mixture;

[0010] S2. First carry out low-temperature pyrolysis on the above-mentioned precursor mixture, then carry out high-temperature pyrolysis, and after cooling and washing, obtain a lead single atom / nanoparticle anchored carbon aerogel.

[0011] Further, in step (1), the lead salt is at least one of lead acetate, lead nitrate, and lead chloride, among which lead acetate and lead nitrate are more commonly used, having good solubility and low cost; the agricultural and forestry biomass is rice husk or corn straw, and the particle size range is 50 to 500 micrometers.

[0012] Further, in step (1), the molten salt includes: a metal salt for crosslinking and a metal salt for dissolving and dispersing, and the mass ratio is 3:7 - 7:3. Within this range, the effect of the pyrolysis reaction can be optimized, and the stability of the product can be improved.

[0013] Further, the metal salt for crosslinking includes zinc chloride, calcium chloride or magnesium chloride, and the metal salt for dissolution and dispersion includes potassium chloride or sodium chloride.

[0014] Further, in step (1), the mass ratio of the agricultural and forestry biomass to the molten salt is 1:1 to 1:5, and the molar ratio of the lead salt to the molten salt is 1:1 to 1:20.

[0015] Further, in step (2), the conditions for low-temperature pyrolysis are as follows: in air or dilute oxygen gas, in the range of 250 °C to 350 °C, and continuously pyrolyzed for 1 to 4 hours.

[0016] Further, in step (2), the conditions for high-temperature pyrolysis are as follows: in nitrogen or argon, in the range of 600 °C to 900 °C, and the continuous pyrolysis time is 1 to 4 hours.

[0017] Air or dilute oxygen gas is used in the low-temperature pyrolysis stage, while nitrogen or argon is used in the high-temperature pyrolysis stage to ensure a suitable redox environment and effective anchoring of lead single atoms / nanoparticles. The duration of the low-temperature and high-temperature pyrolysis stages is 1 to 4 hours respectively, which can ensure the good structural stability of the carbon aerogel and promote the uniform loading of lead, which can ensure the good structural stability of the carbon aerogel and promote the uniform loading of lead.

[0018] The present invention provides a carbon aerogel anchored with lead single atoms / nanoparticles prepared by the above preparation method.

[0019] The present invention provides an application of the above carbon aerogel anchored with lead single atoms / nanoparticles in the field of lead-carbon batteries.

[0020] Further, the negative electrode of the lead-carbon battery is coated with a negative electrode lead paste. The negative electrode lead paste includes, by mass: 100 to 120 parts of lead powder, 0.5 to 4 parts of a carbon additive, 10 to 13 parts of deionized water, and 8 to 10 parts of dilute sulfuric acid. The negative electrode lead paste can significantly improve the cycle number of the high-rate partial state of charge and the retention rate of the deep cycle capacity of the lead-carbon battery, and enhance the comprehensive performance of the battery; the carbon additive includes, by mass: 40 to 200 parts of a carbon aerogel anchored with lead single atoms / nanoparticles, 4 to 6 parts of carbon fiber, 8 to 12 parts of humic acid, 9 to 18 parts of barium sulfate, and 8 to 12 parts of sodium lignosulfonate. The carbon additive can effectively improve the electrochemical performance of the negative electrode of the lead-acid battery, inhibit the hydrogen evolution reaction, and improve the cycle life.

[0021] Principle of the invention: In the present invention, a lead salt, a molten salt and agricultural and forestry biomass are first mixed to prepare for the subsequent pyrolysis process, and then staged pyrolysis is carried out. In the low-temperature pyrolysis stage, the agricultural and forestry biomass begins to depolymerize and undergoes a cross-linking and reconstruction reaction with the molten salt (zinc chloride / calcium chloride / magnesium chloride) to form a preliminary carbon aerogel framework structure; in the high-temperature pyrolysis stage, nitrogen or argon is used as the atmosphere to ensure pyrolysis in an oxygen-free environment, further promoting the capture of lead single atoms and lead nanoparticles by carbon defects. Finally, unreacted residues are removed by washing. The prepared carbon aerogel anchored with lead single atoms / nanoparticles can be added to carbon additives and the negative electrode lead paste of lead-carbon batteries and applied to lead-carbon batteries, significantly improving the performance of the batteries, extending their service life, and enhancing their high-rate charge and discharge capabilities.

[0022] Advantageous effects: Compared with the prior art, the present invention has the following remarkable advantages: The preparation method adopted in the present invention can quickly and uniformly anchor lead single atoms / nanoparticles in the carbon aerogel material. By optimizing the uniformity of lead loading, improving the binding force between lead and carbon, and enhancing the conductivity and pore structure of the battery, the cycle number of the high-rate partial state of charge and the rate discharge capacity of the negative electrode of lead-acid batteries are significantly improved, having good application prospects and high commercial value. Description of the drawings

[0023] Figure 1 Scanning electron microscope image of the carbon aerogel anchored with lead single atoms / nanoparticles prepared in Example 1;

[0024] Figure 2 Transmission electron microscope image of the carbon aerogel anchored with lead single atoms / nanoparticles prepared in Example 1;

[0025] Figure 3 Aberration-corrected transmission electron microscope image of the carbon aerogel anchored with lead single atoms / nanoparticles prepared in Example 1. Detailed implementation manners

[0026] Next, the present invention will be further described in conjunction with specific embodiments and drawings.

[0027] Example 1: The preparation method of the carbon aerogel anchored with lead single atoms / nanoparticles provided in this example includes the following steps:

[0028] S1: Preparation of the precursor mixture

[0029] Lead acetate is selected as the lead salt and mixed with zinc chloride and sodium chloride in a molar ratio of 1:5 to form a lead salt-molten salt mixture. The molar ratio of zinc chloride to sodium chloride is 1:1. The crushed rice husks (particle size of 200 microns) are added to the lead salt-molten salt mixture, and the mass ratio of rice husks to the molten salt is 1:3. Under stirring, ensure uniform mixing to obtain a uniform precursor mixture.

[0030] S2: Stepwise pyrolysis treatment

[0031] Put the precursor mixture into the air, set the temperature to 300 °C, and the pyrolysis duration is 1.5 hours. Subsequently, raise the temperature to 600 °C, use nitrogen as the atmosphere, and the pyrolysis time is 2 hours. After pyrolysis is completed, naturally cool it to room temperature, and wash it with deionized water to remove the unreacted residual substances to obtain the final composite material.

[0032] Example 2: The preparation method of the lead single-atom / nanoparticle anchored carbon aerogel provided in this example includes the following steps:

[0033] S1: Preparation of the precursor mixture

[0034] Select lead nitrate as the lead salt, mix it with calcium chloride and potassium chloride in a molar ratio of 1:7 to form a lead salt-molten salt mixture. The molar ratio of calcium chloride to potassium chloride is 1:1. Add corn straw (particle size of 100 microns) to the lead salt-molten salt mixture, and the mass ratio of corn straw to the molten salt is 1:2. Under stirring, ensure uniform mixing to obtain the final composite material

[0035] S2: Stepwise pyrolysis treatment

[0036] Place the precursor mixture in a dilute oxygen atmosphere, set the temperature to 280 °C, and the pyrolysis time is 2 hours. Subsequently, raise the temperature to 750 °C under a nitrogen atmosphere, and the pyrolysis time is 1 hour. After pyrolysis is completed, naturally cool it to room temperature, and wash it with deionized water to remove the unreacted residual substances to obtain the final composite material.

[0037] Example 3: The preparation method of the lead single-atom / nanoparticle anchored carbon aerogel provided in this example includes the following steps:

[0038] S1: Preparation of the precursor mixture

[0039] Select lead chloride as the lead salt, mix it with magnesium chloride and sodium chloride in a molar ratio of 1:10 to form a lead salt-molten salt mixture. Add the crushed rice husk (particle size of 300 microns) to the lead salt-molten salt mixture, and the mass ratio of rice husk to the molten salt is 1:1. Under stirring, ensure uniform mixing to obtain the final composite material.

[0040] S2: Stepwise pyrolysis treatment

[0041] Place the precursor mixture in an air atmosphere, set the temperature to 320 °C, and the pyrolysis time is 1 hour. Subsequently, raise the temperature to 850 °C under a nitrogen atmosphere, and the pyrolysis time is 1.5 hours. After pyrolysis is completed, naturally cool it to room temperature, and wash it with deionized water to remove the unreacted residual substances to obtain the final composite material.

[0042] Example 4: The preparation method of the lead single-atom / nanoparticle-anchored carbon aerogel provided in this example includes the following steps:

[0043] S1: Preparation of the precursor mixture

[0044] Select lead acetate as the lead salt, mix it with zinc chloride and sodium chloride in a molar ratio of 1:1 to form a lead salt - molten salt mixture. Add the crushed corn straw (particle size of 400 microns) to the lead salt - molten salt mixture, and the mass ratio of corn straw to molten salt is 1:4. Under stirring, ensure uniform mixing to obtain the final composite material.

[0045] S2: Stepwise pyrolysis treatment

[0046] Place the precursor mixture in an air atmosphere, set the temperature to 350 °C, and the pyrolysis time to 1 hour. Subsequently, raise the temperature to 900 °C in an argon atmosphere, and the pyrolysis time is 2 hours. After pyrolysis is completed, naturally cool to room temperature and wash with deionized water to remove unreacted residues to obtain the final composite material.

[0047] Comparative Example 1: The difference from Example 1 is that no lead salt is added, and the preparation method is as follows:

[0048] S1: Preparation of the precursor mixture

[0049] Mix zinc chloride and sodium chloride in a molar ratio of 1:1 to form a lead salt - molten salt mixture. Add the crushed rice husk (particle size of 200 microns) to the lead salt - molten salt mixture, and the mass ratio of rice husk to molten salt is 1:3. Under stirring, ensure uniform mixing to obtain a uniform precursor mixture.

[0050] S2: Stepwise pyrolysis treatment

[0051] Place the precursor mixture in air, set the temperature to 300 °C, and the pyrolysis duration to 1.5 hours. Subsequently, raise the temperature to 600 °C, use nitrogen as the atmosphere, and the pyrolysis time is 2 hours. After pyrolysis is completed, naturally cool to room temperature and wash with deionized water to remove unreacted residues to obtain the final composite material.

[0052] Comparative Example 2: The difference from Example 1 is that no zinc chloride is added, and the preparation method is as follows:

[0053] S1: Preparation of the precursor mixture

[0054] Select lead acetate as the lead salt, mix it with sodium chloride in a molar ratio of 1:5 to form a lead salt - molten salt mixture. Add the crushed rice husk (particle size of 200 microns) to the lead salt - molten salt mixture, and the mass ratio is 1:3. Under stirring, ensure uniform mixing to obtain a uniform precursor mixture.

[0055] S2: Pyrolysis treatment in stages

[0056] Put the precursor mixture into the air, set the temperature to 300 °C, and the pyrolysis duration is 1.5 hours. Subsequently, raise the temperature to 600 °C, use nitrogen as the atmosphere, and the pyrolysis time is 2 hours. After pyrolysis is completed, cool it naturally to room temperature, and wash it with deionized water to remove unreacted residual substances to obtain the final composite material.

[0057] Comparative Example 3: The difference from Example 1 is that one-stage high-temperature pyrolysis is adopted, and the preparation method is as follows:

[0058] S1: Preparation of precursor mixture

[0059] Select lead acetate as the lead salt, mix it with zinc chloride and sodium chloride in a molar ratio of 1:5 to form a lead salt-molten salt mixture. The molar ratio of zinc chloride to sodium chloride is 5:5. Add the crushed rice husk (particle size of 200 microns) to the lead salt-molten salt mixture, and the mass ratio of rice husk to molten salt is 1:3. Under stirring, ensure uniform mixing to obtain a uniform precursor mixture.

[0060] S2: One-stage pyrolysis treatment

[0061] Pyrolyze the precursor in a nitrogen atmosphere at 600 °C for 2 hours. After pyrolysis is completed, cool it naturally to room temperature, and wash it with deionized water to remove unreacted residual substances to obtain the final composite material.

[0062] Application Example 1 - Application Example 4 and Application Comparative Example 1 - Application Comparative Example 3:

[0063] A preparation method of a lead-carbon battery, comprising the following steps:

[0064] S1: Preparation of the negative electrode lead paste of the lead-carbon battery: The raw materials include by mass: 100 parts of lead powder, 2 parts of carbon additive, 12 parts of deionized water, and 9 parts of dilute sulfuric acid. The carbon additive is the carbon additive according to claim 5, to obtain the negative electrode lead paste of the lead-carbon battery;

[0065] S2: Preparation of the negative electrode plate of the lead-carbon battery: Coat the negative electrode lead paste of the lead-carbon battery on the surface of the lead alloy grid, and cure it according to the following process: (1) 50 °C, 98 humidity, 24 hours; (2) 55 °C, 80 humidity, 15 hours; (3) 60 °C, 30 humidity, 3 hours; (4) 70 °C, 10 humidity, 3 hours, to obtain the negative electrode plate of the lead-carbon battery;

[0066] S3: Assemble a 4V4Ah lead-carbon battery using the negative electrode plate of the lead-carbon battery according to the standards of the battery factory, and then perform internal formation (three positive and three negative in a single cell, separator thickness 1.5 mm, single-pack positive plate). Add 56 ml of acid (1.278 g / ml, 25 °C) to each cell, containing 0.8% sodium sulfate. The acid addition is carried out using a vacuum pressure acid injection machine, evacuated to a vacuum pressure of 0.08 MPa in 7 s, then the atmosphere is introduced for 4 s, and this process is repeated 3 times. During the formation process, the acid pot is always inserted into the acid injection port, and a gas guide tube is placed at the same time. After formation, a vacuum acid extraction machine is used to extract the excess acid (it needs to be quickly extracted within 15 minutes after shutdown).

[0067] Effect evaluation

[0068] 1. High-rate cycle life test.

[0069] Discharge the above 4V4Ah lead-carbon battery to 50% state of charge at 1C current, charge at 2C rate for 60 s, rest for 20 s, and cycle in the way of discharging at 2C rate for 60 s until the discharge voltage is lower than 1.7V, and detect the number of cycle charge and discharge times. The technical effects of the charge and discharge times are shown in Table 1. It can be seen from Examples 1-4 and the blank control group in Table 1 that the addition of lead single atoms / nanoparticle-anchored carbon aerogel significantly improves the high-rate cycle life of the negative electrode, and different preparation parameters have an impact on the performance. Further combining Example 1 and Comparative Examples 1-3, it is found that: not adding lead salt reduces the cycle times to 11224 times (Comparative Example 1), which shows the importance of loading lead single atoms / nanoparticles; not adding zinc chloride reduces the cycle times to 9845 times (Comparative Example 2), which shows the importance of zinc chloride in the construction of the carbon aerogel structure; using one-stage high-temperature pyrolysis reduces the cycle times to 5321 times (Comparative Example 3), which shows the importance of pyrolysis in the low-temperature section for the construction of the carbon aerogel structure.

[0070] Table 1

[0071] Group Number of cycles (times) Group Number of cycles (times) Example 1 20342 Comparative Example 1 11224 Example 2 18672 Comparative Example 2 9845 Example 3 16578 Comparative Example 3 7689 Example 4 17654 Blank control group 5321

[0072] 2. 80% DoD deep cycle life test.

[0073] The 80% DoD deep cycle life test is used to analyze the cycle stability of the battery under high-current deep cycle conditions. After full charge, discharge at a current of 0.4C for 8 hours, let it stand for 2 hours, charge with constant voltage and current limiting (4.7V / 0.3C) to 3.36Ah, let it stand for 2 hours. After 150 cycles of the above process, discharge the battery at 0.2C to 1.75V, and calculate the capacity retention rate after 150 cycles. The test results are shown in Table 2. It can be seen from Table 2 that, compared with the blank control group, the addition of lead single atom / nanoparticle-anchored carbon aerogel significantly improves the 80% DoD deep cycle capacity retention rate of the negative electrode. Further combining Example 1 and Comparative Examples 1-3, it is found that the addition of lead salt and cross-linked molten salt, and the retention of the low-temperature pyrolysis process have a significant effect on the improvement of the performance of carbon aerogel.

[0074] Table 2

[0075]

Claims

1. A method for preparing a lead single atom / nanoparticle anchored carbon aerogel, characterized in that: The following steps are involved: S1. Mixing lead salt and molten salt to form a lead salt-molten salt mixture, and then adding crushed agricultural and forestry biomass, and mixing evenly to obtain a precursor mixture; S2. The precursor mixture is first subjected to low-temperature pyrolysis and then to high-temperature pyrolysis, and then cooled and washed to obtain a carbon aerogel anchored with lead single atoms / nanoparticles.

2. The preparation method according to claim 1, characterized in that: In step (1), the lead salt is at least one of lead acetate, lead nitrate and lead chloride; and the agricultural and forestry biomass is rice husk or corn stalk.

3. The preparation method according to claim 1, characterized in that: In step (1), the molten salt includes: a metal salt for cross-linking and a metal salt for dissolving and dispersing, with a mass ratio of 3:7 to 7:

3.

4. The preparation method according to claim 3, characterized in that: In step (1), the metal salt used for cross-linking includes zinc chloride, calcium chloride or magnesium chloride, and the metal salt used for dissolving and dispersing includes potassium chloride or sodium chloride.

5. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the agricultural and forestry biomass to the molten salt is 1:1 to 1:5, and the molar ratio of the lead salt to the molten salt is 1:1 to 1:

20.

6. The preparation method according to claim 1, characterized in that: In step (2), the low-temperature pyrolysis conditions are: in air or diluted oxygen gas, at a temperature in the range of 250° C. to 350° C., and continuously pyrolyzing for 1 to 4 hours.

7. The preparation method according to claim 1, characterized in that: In step (2), the high temperature pyrolysis conditions are: in nitrogen or argon, in the range of 600°C to 900°C, and the pyrolysis time is 1 to 4 hours.

8. A lead single atom / nanoparticle anchored carbon aerogel prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the lead single atom / nanoparticle anchored carbon aerogel according to claim 8 in the field of lead-carbon batteries.

10. The use according to claim 9, characterized in that: The negative electrode of the lead-carbon battery is coated with a negative electrode lead paste, which includes, by mass, 100 to 120 parts of lead powder, 0.5 to 4 parts of carbon additives, 10 to 13 parts of deionized water, and 8 to 10 parts of dilute sulfuric acid. The carbon additive includes, by mass, 40 to 200 parts of carbon aerogel anchored by lead single atoms / nanoparticles, 4 to 6 parts of carbon fibers, 8 to 12 parts of humic acid, 9 to 18 parts of barium sulfate, and 8 to 12 parts of sodium lignin sulfonate.

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