Carbon-coated barium sulfate / porous carbon composite material as well as preparation method and application thereof

Abstract

The invention discloses a carbon-coated barium sulfate / porous carbon composite material as well as a preparation method and application thereof, and belongs to the technical field of lead-acid storage batteries. The specific preparation method comprises the following steps: S1, carrying out a reaction on BaSO4 nanoparticles and dopamine hydrochloride to obtain BaSO4 (at) PDA; s2, dispersing GNP and c-CNT in an ethanol / water mixed solution to obtain a dispersion solution; adding BaSO4 (at) PDA into the dispersion liquid for reaction, then slowly dropwise adding a sucrose solution, and performing treatment after reaction to obtain composite precursor powder; s3, performing constant-temperature carbonization on the composite precursor powder in an N2 atmosphere; after the carbonization is finished, switching gas into CO2 for constant-temperature activation; then switching back to N2, and cooling to room temperature; the carbon-coated barium sulfate / porous carbon composite material is obtained. According to the composite material, through collaborative design of a gradient nitrogen-doped carbon shell, a GNP-c-CNT three-dimensional network and CO2 activated mesopores, the electrochemical performance of the negative electrode of the lead storage battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lead-acid batteries, and particularly relates to a carbon-coated barium sulfate / porous carbon composite material, a preparation method thereof and application thereof. BACKGROUND

[0002] Lead-acid batteries, as a mature and widely used energy storage technology, play an important role in automobile starting, backup power supply and renewable energy storage. However, its low energy density, limited cycle life and sulfation limit its further development. In recent years, research focuses on optimizing electrode materials, improving electrolyte formulations and developing new additives. Among them, carbon-based materials are widely used in negative electrode modification due to their excellent electrical conductivity and chemical stability, to inhibit the irreversible deposition of lead sulfate and improve battery performance.

[0003] In recent years, carbon-coated barium sulfate / porous carbon composite materials have attracted widespread attention due to their unique structure and performance. Patent application No. CN105576240A discloses a nano barium sulfate / carbon composite material, a preparation method and application thereof. The nano barium sulfate / carbon composite material is distributed on the surface of the carbon material and fully contacts the surface of the lead paste active material, which can provide a large number of crystal nuclei for the deposition of lead sulfate grains. At the same time, the carbon combined with the active sites of barium sulfate can play a role in transmitting electrons, and the electrical conductivity at the reaction site is enhanced. In battery tests, the negative electrode added with the composite material has a capacity retention rate of more than 90% after 2000 cycles under 1C charging / 0.3C discharging conditions, which is significantly better than traditional negative electrode materials. However, this technology also has obvious limitations: first, the carbon material only serves as a carrier and does not form a complete coating, and the barium sulfate particles are easy to directly contact with the electrolyte, leading to dissolution; second, the high surface energy of the nanoparticles leads to a tendency to agglomerate during the cycle process.

[0004] Therefore, designing a porous carbon composite material that can inhibit electrode sulfation, improve cycle life and improve low-temperature performance is an important research direction in the field of lead-acid battery negative electrode modification. SUMMARY

[0005] One of the purposes of the present application is to provide a carbon-coated barium sulfate / porous carbon composite material as a lead-acid battery negative electrode additive, which promotes the growth of smaller lead sulfate crystals, highly disperses in the negative electrode active material, increases the specific surface area of the negative electrode active material, enhances the electrical conductivity of the negative electrode active material, and prolongs the cycle life of the battery.

[0006] The second purpose of the present application is to provide a preparation method of a carbon-coated barium sulfate / porous carbon composite material, which is used for preparing the above-mentioned carbon-coated barium sulfate / porous carbon composite material.

[0007] The third object of the present application is to provide an application of the carbon-coated barium sulfate / porous carbon composite material in a lead-acid battery.

[0008] The object of the present application can be achieved by the following technical solutions.

[0009] A preparation method of a carbon-coated barium sulfate / porous carbon composite material, comprising the following steps:

[0010] S1, dispersing BaSO4 nanoparticles in Tris buffer, ultrasonic treatment to form a suspension; dissolving dopamine hydrochloride in Tris buffer, adding to the suspension, stirring for 3 hours; centrifugal washing, vacuum drying, obtaining BaSO4@PDA;

[0011] S2, dispersing GNP (graphene nanoplatelets) and c-CNT (carboxylated carbon nanotubes) in an ethanol / water mixture, ultrasonic treatment to obtain a dispersion; adding BaSO4@PDA to the dispersion, ultrasonic treatment; slowly adding a sucrose solution under continuous stirring; after the addition is completed, warming and stirring, drying, grinding, sieving, obtaining a BaSO4@PDA / G-CNT / sucrose composite precursor powder;

[0012] S3, carbonizing the composite precursor powder under N2 atmosphere protection at a constant temperature; after carbonization is completed, cooling to room temperature, switching the gas to CO2, constant temperature activation, then switching back to N2, cooling to room temperature; obtaining a carbon-coated barium sulfate / porous carbon composite material (G-BaSO4@NC / G-CNT composite material).

[0013] The PDA is carbonized to form a gradient nitrogen-doped carbon shell (BaSO4@NC); the sucrose is carbonized and decomposed, forming a bonding carbon between GNP and c-CNT, reinforcing the three-dimensional network (G-CNT); the carboxyl part of c-CNT is decomposed, retaining the overall structural integrity; the purpose of switching CO2 constant temperature activation is to slightly etch the carbon layer, increasing the number of mesopores.

[0014] Further, the weight ratio of the BaSO4 nanoparticles and dopamine hydrochloride is (45-55):(1.5-2.5).

[0015] Further, the particle size of the BaSO4 nanoparticles is 100-250 nm.

[0016] Further, the pH of the Tris buffer is 8.3-8.6.

[0017] Further, the washing is alternating washing with deionized water and anhydrous ethanol for 3 times each; the vacuum drying is drying in a 70-80℃ vacuum oven for 12-16 hours.

[0018] Further, the power of the ultrasonic treatment is 300-400 W; the time of the ultrasonic treatment is 30-60 minutes; and the rotating speed of the stirring is 300-500 rpm.

[0019] Further, the weight ratio of the GNP, the c-CNT, the ethanol / water mixture, the BaSO4@PDA and the sucrose is (12-18):(3-7):(450-600):(48-58):(8-12).

[0020] Further, the volume ratio of the ethanol and the water in the ethanol / water mixture is 1:1; and the weight ratio of the sucrose and the deionized water in the sucrose solution is 8-12:100.

[0021] Further, the temperature of the temperature-raising stirring is 55-60 DEG C, and the stirring lasts for 4-6 hours.

[0022] Further, the mesh size of the sieving is 80-120.

[0023] Further, the temperature of the constant-temperature carbonization is 780-800 DEG C; the temperature of the constant-temperature activation is 830-850 DEG C; and the temperature-raising rate is 3-5 DEG C / min.

[0024] Further, the time of the constant-temperature carbonization is 2-2.5 hours; and the time of the constant-temperature activation is 30-40 minutes.

[0025] A carbon-coated barium sulfate / porous carbon composite material is prepared by the above method.

[0026] The carbon-coated barium sulfate / porous carbon composite material is prepared by the above method.

[0027] The present application has the following advantages:

[0028] (1) The continuous nitrogen-doped carbon shell formed by in-situ polymerization and carbonization of PDA on the surface of BaSO4, slow control of the heating rate, step-by-step pyrolysis reaction of the inner layer and the outer layer, the inner layer completes the stabilization of pyridine nitrogen at a lower temperature range (500-700 DEG C) first, and the outer layer completes the conversion of graphite nitrogen at a higher temperature (700-800 DEG C), and finally forms a gradient nitrogen-doped carbon shell with an inner layer rich in pyridine nitrogen and an outer layer rich in graphite nitrogen. It not only provides a high-conductivity coating for barium sulfate, but also enhances the charge transfer of the inner layer rich in pyridine nitrogen and the stability of the outer layer rich in graphite nitrogen; the gradient distribution of nitrogen elements not only enhances the interfacial bonding force between the carbon shell and BaSO4, reduces the dissolution and loss of active components, but also provides efficient heterogeneous nucleation centers for lead sulfate crystals, effectively promotes the nucleation and growth of lead sulfate crystals, and fundamentally inhibits the negative sulfate.

[0029] (2) The three-dimensional hybrid network constructed by graphene nanosheets (GNP) and carboxylated carbon nanotubes (c-CNT) generates a through high-conductivity skeleton after being connected by sucrose carbonization. The large specific surface area and planar conductivity of GNP, combined with the conductivity of c-CNT and the interfacial affinity of residual carboxyl groups, improve the overall conductivity and mechanical stability of the negative active material.

[0030] (3) The CO2 activation of mesoporous regulation and component synergistic effect further optimizes the material performance. After nitrogen carbonization, CO2 is switched to short-time high-temperature activation, and a large number of mesopores are introduced into the carbon skeleton through controllable etching. These mesopores not only significantly increase the specific surface area of the material, promote the electrolyte infiltration and ion diffusion, but also provide more dispersed anchoring points for lead sulfate crystals, ensuring the high dispersion of the active material. BRIEF DESCRIPTION OF DRAWINGS

[0031] The application will be further described below with reference to the accompanying drawings.

[0032] Figure 1 is the SEM image of the composite material prepared in Example 1 of the application;

[0033] Figure 2 is the SEM image of the composite material prepared in Example 2 of the application;

[0034] Figure 3 is the SEM image of the composite material prepared in Example 3 of the application;

[0035] Figure 4 is the SEM image of the composite material prepared in Example 4 of the application;

[0036] Figure 5 is the SEM image of the composite material prepared in Example 5 of the application;

[0037] Figure 6 SEM image of the composite material prepared in Example 6 of the present application. DETAILED DESCRIPTION

[0038] The specific embodiments of the present application are described in detail below, but it should be understood that the scope of the present application is not limited by the specific embodiments.

[0039] Example 1

[0040] This example provides a carbon-coated barium sulfate / porous carbon composite material, which is prepared by the following steps:

[0041] S1, 50 g of dry BaSO4nanoparticles were dispersed in 800 mL of Tris buffer, and ultrasonic treatment was performed for 30 minutes (power 300 W) to form a suspension; 1.8 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer and added to the room temperature stirred suspension, and stirring reaction was performed for 3 hours; the product was collected by centrifugation, and washed with deionized water and anhydrous ethanol for 3 times alternately; drying was performed in a vacuum oven at 80°C for 12 hours to obtain BaSO4@PDA;

[0042] S2, 15 g of GNP (graphene nanoplatelets) and 5 g of c-CNT (carboxylated carbon nanotubes) were dispersed in 500 mL of ethanol / water mixture (Vethanol:Vwater = 1:1) and ultrasonic treatment was performed for 1 hour to obtain a dispersion; 51.5 g of BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, sucrose solution (sucrose:deionized water = 10:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was raised to 60°C, and continuous stirring was performed for 5 hours until a viscous paste was formed; drying was performed in a blast drying oven at 100°C for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain uniform BaSO4@PDA / G-CNT / sucrose composite precursor powder;

[0043] S3, the composite precursor powder was raised to 800°C at a temperature raising rate of 5°C / min under N2atmosphere protection; isothermal carbonization was performed for 2 hours; after the carbonization was completed, natural cooling was performed to room temperature under N2protection, the gas was switched to CO2, the temperature was raised to 850°C, and isothermal activation was performed for 30 minutes, then the gas was switched back to N2, and cooling was performed to room temperature; a carbon-coated barium sulfate / porous carbon composite material (G-BaSO4@NC / G-CNT composite material) was obtained.

[0044] The SEM image of the above composite material is shown in Figure 1 .

[0045] Example 2

[0046] The embodiment is different from example 1 in that the proportion of dopamine hydrochloride is increased, and the specific implementation steps of S1 are as follows:

[0047] S1, 50 g of dried BaSO4 nanoparticles were dispersed in 800 mL of Tris buffer, ultrasonic treatment for 30 minutes (power 300 W) to form a suspension; 2.4 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer, and was added to the stirring suspension at room temperature, and stirred for 3 hours; the product was collected by centrifugation, and was washed with deionized water and anhydrous ethanol for 3 times alternately; dried in a vacuum oven at 80°C for 12 hours to obtain BaSO4@PDA;

[0048] The remaining raw materials and preparation process are the same as those of example 1.

[0049] The SEM image of the composite material is shown in Figure 2 .

[0050] Example 3

[0051] The embodiment is different from example 1 in that the proportion of dopamine hydrochloride is reduced, and the specific implementation steps of S1 are as follows:

[0052] S1, 50 g of dried BaSO4 nanoparticles were dispersed in 800 mL of Tris buffer, ultrasonic treatment for 30 minutes (power 300 W) to form a suspension; 2.4 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer, and was added to the stirring suspension at room temperature, and stirred for 3 hours; the product was collected by centrifugation, and was washed with deionized water and anhydrous ethanol for 3 times alternately; dried in a vacuum oven at 80°C for 12 hours to obtain BaSO4@PDA;

[0053] The remaining raw materials and preparation process are the same as those of example 1.

[0054] The SEM image of the composite material is shown in Figure 3 .

[0055] Example 4

[0056] The embodiment is different from example 1 in that the proportion of GNP is increased, and the specific implementation steps of S2 are as follows:

[0057] S2, 18 g of GNP (graphene nanoplatelets) and 4 g of c-CNT (carboxylated carbon nanotubes) were dispersed in 500 mL of an ethanol / water mixture (Vethanol:Vwater = 1:1), and ultrasonic treatment was performed for 1 hour to obtain a dispersion liquid; 48.5 g of BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion liquid, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose: deionized water = 8:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was raised to 60°C, and continuous stirring was performed for 5 hours until a viscous paste was formed; drying was performed in a blast drying oven at 100°C for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4@PDA / G-CNT / sucrose composite precursor powder;

[0058] The remaining raw materials and preparation process were the same as in Example 1.

[0059] The SEM image of the above composite material is shown in Figure 4 .

[0060] Example 5

[0061] Compared with Example 1, the difference is that the proportion of c-CNT is increased, and the specific implementation steps of S2 are as follows:

[0062] S2, 13 g of GNP (graphene nanoplatelets) and 7 g of c-CNT (carboxylated carbon nanotubes) were dispersed in 500 mL of an ethanol / water mixture (Vethanol:Vwater = 1:1), and ultrasonic treatment was performed for 1 hour to obtain a dispersion liquid; 52 g of BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion liquid, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose: deionized water = 9:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was raised to 60°C, and continuous stirring was performed for 5 hours until a viscous paste was formed; drying was performed in a blast drying oven at 100°C for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4@PDA / G-CNT / sucrose composite precursor powder;

[0063] The remaining raw materials and preparation process were the same as in Example 1.

[0064] The SEM image of the above composite material is shown in Figure 5 .

[0065] Example 6

[0066] Compared with Example 1, the difference is that the proportion of sucrose is increased, and the specific implementation steps of S2 are as follows:

[0067] S2, 16 g of GNP (graphene nanoplatelets) and 4.5 g of c-CNT (carboxylated carbon nanotubes) were dispersed in 500 mL of an ethanol / water mixture (Vethanol:Vwater = 1:1) and ultrasonically treated for 1 hour to obtain a dispersion; 51.5 g of the BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion, and ultrasonically treated for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose: deionized water = 12:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was raised to 60°C, and continuous stirring was performed for 5 hours until a viscous paste was formed; drying was performed in a 100°C air-drying oven for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4@PDA / G-CNT / sucrose composite precursor powder;

[0068] The remaining raw materials and preparation process were the same as in Example 1.

[0069] The SEM image of the composite material is shown in FIG. 1. Figure 6

[0070] Comparative Example 1

[0071] This comparative example differs from Example 1 in that CO2 activation is not performed, and the specific implementation steps of S3 are as follows:

[0072] S3, the composite precursor powder was raised to 800°C at a temperature raising rate of 5°C / min under the protection of N2 atmosphere; carbonization was performed at constant temperature for 2 hours; cooling was performed to room temperature; a carbon-coated barium sulfate / porous carbon composite material (G-BaSO4@NC / G-CNT composite material) was obtained.

[0073] The remaining raw materials and preparation process were the same as in Example 1.

[0074] Comparative Example 2

[0075] This comparative example differs from Example 1 in that sucrose is not added, and the specific implementation steps are as follows:

[0076] S1, 50 g of dried BaSO4 nanoparticles were dispersed in 800 mL of Tris buffer and ultrasonically treated for 30 minutes (power 300 W) to form a suspension; 1.8 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer and added to the room-temperature stirred suspension, and stirring reaction was performed for 3 hours; the product was collected by centrifugation and washed with deionized water and anhydrous ethanol for 3 times alternately; drying was performed in a 80°C vacuum oven for 12 hours to obtain BaSO4@PDA;

[0077] ​S2, 15 g of GNP (graphene nanoplatelets) and 5 g of c-CNT (carboxylated carbon nanotubes) were dispersed in 500 mL of an ethanol / water mixture (Vethanol:Vwater = 1:1), and ultrasonic treatment was performed for 1 hour to obtain a dispersion liquid; 51.5 g of BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion liquid, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); drying was performed in a blast drying oven at 100°C for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4@PDA / G-CNT composite precursor powder;

[0078] S3, the composite precursor powder was heated to 800°C at a heating rate of 5°C / min under N2protection; carbonization was performed at constant temperature for 2 hours; after carbonization was completed, natural cooling was performed to room temperature under N2protection, the gas was switched to CO2, heating was performed to 850°C, and activation was performed at constant temperature for 30 minutes, then N2was switched back, and cooling was performed to room temperature; a carbon-coated barium sulfate / porous carbon composite material was obtained.

[0079] The remaining raw materials and preparation processes were the same as those of Example 1.

[0080] Comparative Example 3

[0081] This comparative example is different from Example 1 in that PDA is not added, and the specific implementation steps are as follows:

[0082] S1, 15 g of GNP (graphene nanoplatelets) and 5 g of c-CNT (carboxylated carbon nanotubes) were dispersed in 500 mL of an ethanol / water mixture (Vethanol:Vwater = 1:1), and ultrasonic treatment was performed for 1 hour to obtain a dispersion liquid; 51.5 g of BaSO4 nanoparticles was slowly added to the above dispersion liquid, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose: deionized water = 10:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was increased to 60°C, and stirring was continued for 5 hours until a viscous paste was formed; drying was performed in a blast drying oven at 100°C for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4 / G-CNT / sucrose composite precursor powder;

[0083] S2, the composite precursor powder was heated to 800°C at a heating rate of 5°C / min under N2protection; carbonization was performed at constant temperature for 2 hours; after carbonization was completed, natural cooling was performed to room temperature under N2protection, the gas was switched to CO2, heating was performed to 850°C, and activation was performed at constant temperature for 30 minutes, then N2was switched back, and cooling was performed to room temperature; a carbon-coated barium sulfate / porous carbon composite material was obtained.

[0084] The remaining raw materials and preparation processes were the same as those of Example 1.

[0085] Comparative Example 4

[0086] The comparative example is compared with Example 1, the difference is that c-CNT is not added, and the specific implementation steps are as follows:

[0087] S1, 50 g of dry BaSO4 nanoparticles were dispersed in 800 mL of Tris buffer, and ultrasonic treatment was performed for 30 minutes (power 300 W) to form a suspension; 1.8 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer and added to the room temperature stirred suspension, and stirring reaction was performed for 3 hours; the product was collected by centrifugation and washed with deionized water and anhydrous ethanol for 3 times alternately; drying was performed in a vacuum oven at 80°C for 12 hours to obtain BaSO4@PDA;

[0088] S2, 15 g of GNP (graphene nanoplatelets) were dispersed in 500 mL of ethanol / water mixture (Vethanol:Vwater = 1:1) and ultrasonic treatment was performed for 1 hour to obtain a dispersion; 51.5 g of BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose:deionized water = 10:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was increased to 60°C, and continuous stirring was performed for 5 hours until a viscous paste was formed; drying was performed in a blast drying oven at 100°C for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a composite precursor powder;

[0089] S3, the composite precursor powder was heated to 800°C at a heating rate of 5°C / min under N2 atmosphere; constant temperature carbonization was performed for 2 hours; after the carbonization was completed, natural cooling was performed to room temperature under N2 protection, the gas was switched to CO2, the temperature was increased to 850°C, and constant temperature activation was performed for 30 minutes, and then the gas was switched back to N2, and cooling was performed to room temperature; a carbon-coated barium sulfate / porous carbon composite material was obtained.

[0090] The remaining raw materials and preparation process were the same as those of Example 1.

[0091] Comparative Example 5

[0092] The comparative example is compared with Example 1, the difference is that GNP is not added, and the specific implementation steps are as follows:

[0093] S1, 50 g of dry BaSO4 nanoparticles were dispersed in 800 mL of Tris buffer, and ultrasonic treatment was performed for 30 minutes (power 300 W) to form a suspension; 1.8 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer, and was added to the stirring suspension at room temperature, and stirring reaction was performed for 3 hours; the product was collected by centrifugation, and was washed with deionized water and anhydrous ethanol alternately for 3 times each; drying was performed in a vacuum oven at 80°C for 12 hours to obtain BaSO4@PDA;

[0094] S2, 5 g of c-CNT (carboxylated carbon nanotube) was dispersed in 500 mL of ethanol / water mixture (Vethanol:Vwater = 1:1) to form a dispersion liquid by ultrasonic treatment for 1 hour; 51.5 g of BaSO4@PDA powder obtained in step S1 was slowly added to the above dispersion liquid, and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose:deionized water = 10:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was increased to 60°C, and stirring was continuously performed for 5 hours until a viscous paste was formed; drying was performed in a 100°C air-drying oven for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4@PDA / CNT / sucrose composite precursor powder;

[0095] S3, the composite precursor powder was heated to 800°C at a heating rate of 5°C / min under N2 atmosphere; carbonization was performed at constant temperature for 2 hours; after the carbonization was completed, the temperature was naturally cooled to room temperature under N2 protection, CO2 was switched as the gas, the temperature was increased to 850°C, and activation was performed at constant temperature for 30 minutes, and then N2 was switched back to cool to room temperature; a carbon-coated barium sulfate / porous carbon composite material (G-BaSO4@NC / CNT composite material) was obtained.

[0096] The remaining raw materials and preparation process were the same as those in Example 1.

[0097] Comparative Example 6

[0098] The present comparative example was different from Example 1 in that no GNPs and c-CNTs were added at the same time, and the specific implementation steps were as follows:

[0099] S1, 50 g of dry BaSO4 nanoparticles were dispersed in 800 mL of Tris buffer, and ultrasonic treatment was performed for 30 minutes (power 300 W) to form a suspension; 1.8 g of dopamine hydrochloride was dissolved in 200 mL of Tris buffer, and was added to the stirring suspension at room temperature, and stirring reaction was performed for 3 hours; the product was collected by centrifugation, and was washed with deionized water and anhydrous ethanol alternately for 3 times each; drying was performed in a vacuum oven at 80°C for 12 hours to obtain BaSO4@PDA;

[0100] S2, 51.5 g of BaSO4@PDA powder obtained in step S1 was slowly added into 500 mL of ethanol / water mixture (Vethanol:Vwater = 1:1), and ultrasonic treatment was performed for 30 minutes (power 300 W) with stirring (300 rpm); under continuous stirring, a sucrose solution (sucrose: deionized water = 10:100) was slowly added dropwise; after the dropwise addition was completed, the temperature was raised to 60°C, and continuous stirring was performed for 5 hours until a viscous paste was formed; drying was performed in a 100°C air-drying oven for 12 hours to obtain a block-shaped precursor; the dried block-shaped precursor was ground and passed through a 100-mesh sieve to obtain a uniform BaSO4@PDA / sucrose composite precursor powder;

[0101] S3, the composite precursor powder was heated to 800°C at a heating rate of 5°C / min under N2 atmosphere; carbonization was performed at constant temperature for 2 hours; after the carbonization was completed, natural cooling was performed to room temperature under N2 protection, the gas was switched to CO2, the temperature was raised to 850°C, and activation was performed at constant temperature for 30 minutes, and then the gas was switched back to N2, and cooling was performed to room temperature; a carbon-coated barium sulfate / porous carbon composite material was obtained.

[0102] The remaining raw materials and preparation process were the same as those of Example 1.

[0103] Performance test

[0104] The performance of the carbon-coated barium sulfate / porous carbon composite material obtained in Examples 1-6 and Comparative Examples 1-6 in the negative lead paste was tested, and the specific test items were as follows:

[0105] 1. Specific surface area (m 2 / g): The specific surface area of the composite material was tested according to GB / T 21650.2-2008 “Mercury intrusion porosimetry and gas adsorption method for determining pore size distribution and porosity of solid materials”;

[0106] 2. Electrical conductivity (S / cm): The electrical conductivity of the composite material was tested according to GB / T 40007-2021 “Nanotechnology-Nanomaterials-Contact method for measuring resistivity”;

[0107] 3. Cycle life (times): The cycle life was tested according to GB / T 22473.1-2021 “Storage batteries for energy storage-Part 1: Technical conditions for photovoltaic off-grid applications”;

[0108] 4. Charge-discharge efficiency (%): The charge-discharge efficiency was tested according to GB / T5008.1-2023 “Starting lead-acid batteries-Part 1: Technical conditions and test methods”;

[0109] The results are shown in Table 1:

[0110] Table 1

[0111] Table 1

[0112] As shown in Table 1, the PDA-derived gradient nitrogen-doped carbon shell (inner pyridinic nitrogen / outer graphitic nitrogen) in Example 1 achieved a conductivity of 18.5 S / cm and a cycle life of 650 times. In contrast, Comparative Example 3 (without PDA) had a conductivity of only 8.3 S / cm and a cycle life of only 430 times. This is due to the synergistic effect of the enhanced charge transfer ability of pyridinic nitrogen and the improved interface stability of graphitic nitrogen, which promotes uniform nucleation of small-size PbS04and significantly inhibits sulfation. Example 2 (high PDA amount) had a reduced cycle life due to the excessive thickness of the carbon shell, which hinders ion diffusion and reduces the specific surface area to 285 m2 / g. Example 3 (low PDA amount) had a low charge and discharge efficiency of only 89.5% due to incomplete coating, which reduces the interface stability.

[0113] Example 5 (high c-CNT ratio) achieved a conductivity of 22.3 S / cm and a cycle life of 690 times. The one-dimensional conductive pathways of c-CNT effectively bridge the GNP layers, reducing the interface resistance. In contrast, Comparative Example 4 (without c-CNT) had a conductivity of only 12.6 S / cm and a charge and discharge efficiency of only 81.5% due to the lack of axial conductive channels. Comparative Example 2 (without sucrose) had a conductivity of only 9.8 S / cm (47% lower than Example 1) and a cycle life of 480 times. The lack of adhesive carbon filling between GNP / c-CNT results in a loose network structure, which breaks the electron transport path and accelerates the shedding of negative active materials.

[0114] Example 1 had a specific surface area of 320 m 2 / g and a charge and discharge efficiency of 91.8% after CO2activation. In contrast, Comparative Example 1 (without CO2activation) had a specific surface area of only 240 m 2 / g and a charge and discharge efficiency of only 80.4% due to the insufficient number of mesopores. Example 4 (high GNP ratio) had a specific surface area of 350 m 2 / g, which provided more anchoring sites for lead sulfate crystals and improved the charge and discharge efficiency to 92.5%, confirming the positive effect of mesopore expansion on active material dispersion.

[0115] The above disclosure is only a few specific embodiments of the present application, but the embodiments of the present application are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the scope of the present application.

Claims

1. A method for preparing a carbon-coated barium sulfate / porous carbon composite material, characterized by, The method comprises the following steps: S1, dispersing BaSO4 nanoparticles in Tris buffer to form a suspension; dissolving dopamine hydrochloride in Tris buffer and adding to the suspension, stirring and reacting; centrifugal washing, vacuum drying, and obtaining BaSO4@PDA; S2, dispersing GNPs and c-CNTs in an ethanol / water mixture to obtain a dispersion; adding BaSO4@PDA to the dispersion and ultrasonic treatment; slowly adding a sucrose solution under continuous stirring; heating, stirring, drying, grinding, sieving, and obtaining a composite precursor powder; S3, carbonizing the composite precursor powder under a N2 atmosphere at a constant temperature; switching the gas to CO2 for constant temperature activation after carbonization; then switching back to N2 and cooling to room temperature; and obtaining a carbon-coated barium sulfate / porous carbon composite material.

2. The method for preparing a carbon-coated barium sulfate / porous carbon composite material according to claim 1, characterized in that, The weight ratio of the BaSO4 nanoparticles and dopamine hydrochloride is (45-55):(1.5-2.5); and the particle size of the BaSO4 nanoparticles is 100-250 nm.

3. The method for preparing a carbon-coated barium sulfate / porous carbon composite material according to claim 1, characterized in that, The pH of the Tris buffer is 8.3-8.6; the washing is alternating washing with deionized water and anhydrous ethanol for 3 times each; and the vacuum drying is drying in a vacuum oven at 70-80℃ for 12-16 hours.

4. The method for preparing a carbon-coated barium sulfate / porous carbon composite material according to claim 1, characterized in that, The weight ratio of the GNPs, c-CNTs, ethanol / water mixture, BaSO4@PDA, and sucrose is (12-18):(3-7):(450-600):(48-58):(8-12).

5. The method for preparing a carbon-coated barium sulfate / porous carbon composite material according to claim 1, characterized in that, The volume ratio of ethanol and water in the ethanol / water mixture is 1:1; and the weight ratio of sucrose and deionized water in the sucrose solution is 8-12:

100.

6. The method for preparing a carbon-coated barium sulfate / porous carbon composite material according to claim 1, characterized in that, The power of the ultrasonic treatment is 300-400 W; the time of the ultrasonic treatment is 30-60 minutes; and the stirring speed is 300-500 rpm.

7. The method for preparing a carbon-coated barium sulfate / porous carbon composite material according to claim 1, characterized in that, The heating and stirring is heating to 55-60℃, and continuously stirring for 4-6 hours; and the sieve aperture is 80-120 mesh. 8.The method of claim 1, wherein the carbon-coated barium sulfate / porous carbon composite is prepared by the steps of: (a) preparing a barium sulfate slurry; (b) mixing the barium sulfate slurry with a porous carbon material; (c) drying the mixture; (d) coating the mixture with carbon; and (e) calcining the mixture. The constant temperature carbonization temperature is 780-800℃; the constant temperature activation temperature is 830-850℃; the heating rate is 3-5℃ / min; the constant temperature carbonization time is 2-2.5 hours; and the constant temperature activation time is 30-40 minutes.

9. A carbon-coated barium sulfate / porous carbon composite material, characterized by, The composite material is prepared by the preparation method of the carbon-coated barium sulfate / porous carbon composite material in any one of claims 1-8.

10. The use of a carbon-coated barium sulfate / porous carbon composite material in negative lead paste, characterized in that, The composite material is prepared by the preparation method of the carbon-coated barium sulfate / porous carbon composite material in any one of claims 1-8.

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