Carbon material for battery electrode and preparation method thereof

Abstract

According to the carbon material for the battery electrode and the preparation method of the carbon material, a uniform buffer layer is formed on the surface of a carbon-based material through dissolution, spray granulation and carbonization treatment of polyethyleneimine, and nitrogen-doped functional groups such as pyridine type nitrogen, pyrrole type nitrogen and graphite type nitrogen are introduced. The buffer layer effectively relieves the interface stress and improves the structural stability of the material, the nitrogen-doped functional group remarkably enhances the conductivity, and the interface performance is optimized through combination with the conductive polymer. The spray granulation technology ensures the uniformity of particles and the uniform distribution of a nitrogen source, so that a continuous conductive network is formed after carbonization, and the internal resistance is further reduced. According to the carbon material prepared by the method, the capacity retention rate is up to 81.4%, the internal resistance is as low as 8.5 m omega, and the carbon material shows excellent cycling stability and electrochemical performance under high-temperature charging and discharging conditions, is suitable for lithium ion batteries and other energy storage devices, and shows good practical value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon materials, and particularly relates to a carbon material for battery electrode and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid development of energy storage and conversion technology, batteries play a key role in energy storage as an important carrier in the fields of portable electronic devices, electric vehicles, and large-scale energy storage. In battery technology, the performance of electrode materials directly determines the capacity, cycle life, and rate performance of batteries. Carbon materials have been widely used as electrode materials in various types of batteries, including lithium-ion batteries and sodium-ion batteries, due to their excellent electrical conductivity, stable physical and chemical properties, and low cost. In addition, the diversified structure of carbon materials (such as carbon black, activated carbon, etc.) and the adjustable specific surface area make them have great development potential in the field of energy storage materials. However, traditional carbon materials have significant limitations in the interfacial compatibility with electrolyte or active materials. The surface chemical inertness often leads to low ion transport rate and increased interfacial side reactions, thereby affecting the energy density and cycle stability of the battery.

[0003] Chinese patent (CN117012959A) discloses a modified carbon material, its preparation method and application in electrochemical devices, which discloses grafting ion-conducting polymers on the surface of carbon-based materials in a covalent bonding manner, reducing the increase in interfacial resistance, and improving the interfacial compatibility of carbon materials with other components inside the electrode, improving the structural stability and electrochemical stability of the electrode. Although grafting ion-conducting polymers on the surface of carbon-based materials in a covalent bonding manner improves the interfacial compatibility of carbon materials with other components inside the electrode, during the operation of the battery, especially in high-temperature environments, the dynamic changes of the electrode may adversely affect the stability of the covalent bond between the carbon-based material and the grafted polymer. The thermal expansion coefficients of carbon-based materials (such as carbon black, etc.) and grafted polymers usually differ, meaning that their volume expansion rates differ at high temperatures. Carbon-based materials (such as carbon black, etc.) have a low thermal expansion coefficient, while many ion-conducting polymers, due to their flexible molecular structure, usually have a high thermal expansion coefficient. When the battery is in operation, the temperature rises, which causes thermal stress between the carbon-based material and the polymer. This stress accumulates at the interface between the two, especially when the interface between the two is strongly bonded, the increase in local stress can cause the covalent bond to break or the interface to peel off. Further, this interfacial stress not only can destroy the covalent bond, but also can affect the mechanical stability of the electrode, causing cracks, peeling, or shedding of the polymer layer, thereby reducing the cycle stability and electrochemical performance of the battery. In addition, long-term temperature fluctuations and thermal stress accumulation can cause the performance of the electrode material to degrade, especially during repeated charging and discharging processes, which can exacerbate this effect. SUMMARY

[0004] During the operation of prior art batteries, especially in high temperature environments, the dynamic changes of the electrode can adversely affect the stability of the covalent bond between the carbon-based material and the grafted polymer. There is usually a difference in the thermal expansion coefficients of the carbon-based material and the grafted polymer, meaning that the two will expand in volume to different extents at high temperatures. Carbon-based materials such as carbon black have a lower thermal expansion coefficient, while many ionically conductive polymers, due to the flexibility of their molecular structure, generally have a higher thermal expansion coefficient. When the battery is in operation, the temperature rises, causing thermal stress between the carbon-based material and the polymer. This stress will accumulate at the interface between the two, and especially when the interface between the two is strongly bonded, the increase in local stress can cause the covalent bond to break or the interface to peel off. Further, this interfacial stress can not only break the covalent bond, but also affect the mechanical stability of the electrode, causing the polymer layer to crack, peel or fall off, thereby reducing the cycle stability and electrochemical performance of the battery. In addition, long-term temperature fluctuations and thermal stress accumulation can cause the performance of the electrode material to degrade, especially during repeated charging and discharging processes, and this effect can be exacerbated.

[0005] The present application provides a preparation method of a carbon material for battery electrodes, comprising the following technical steps: step S1. Dissolve polyethyleneimine in ethanol and stir until the polyethyleneimine is completely dissolved, wherein the polyethyleneimine is prepared into a 5 to 10 wt% solution; step S2. Add a carbon-based material to the polyethyleneimine solution, spray granulate the mixture solution to form a polyethyleneimine@carbon-based material composite material, and then perform carbonization treatment on the composite material, wherein the carbonization process is performed in a nitrogen atmosphere; step S3. Dissolve a conductive polymer in ethanol, add an appropriate amount of catalyst, stir until it is uniformly dissolved, and then add the carbonized composite material to the reaction system to obtain a carbon material for battery electrodes.

[0006] It should be noted that in step S1, polyethyleneimine is a high molecular compound with abundant functional groups such as amino (-NH2) and imine (-NH). Under stirring, polyethyleneimine can completely dissolve in ethanol to form a transparent and uniform solution. The concentration range of the solution is usually set to 5-10wt%, which can ensure the role of PEI in the subsequent steps, including dispersing carbon-based materials and providing a structure suitable for carbonization. In step S2, during the spray granulation process, the polyethyleneimine solution is atomized into fine droplets under the action of the nozzle, which quickly forms a uniform coating on the surface of the carbon-based material. Due to the uniform coating in the spray granulation process, the distribution of nitrogen source on the surface of the carbon-based material also tends to be uniform, avoiding the aggregation of nitrogen elements at high temperatures, so that the nitrogen-doped layer is uniformly distributed; during the carbonization process, the nitrogen source generated by the decomposition of polyethyleneimine forms a nitrogen-doped buffer layer on the surface of the carbon-based material. The buffer layer not only plays a surface modification role, but also plays a "buffering" role in physics and mechanics, which can absorb and disperse the stress generated by thermal expansion or contraction. Due to the difference in thermal expansion between carbon-based materials and conductive polymers, temperature changes may cause stress at the interface between the two, which, if not effectively alleviated, may cause peeling, cracking or structural instability of the composite material. The nitrogen-doped structure in the buffer layer can alleviate this thermal stress to some extent. First, the introduction of nitrogen atoms makes the buffer layer have a certain elasticity and deformability, so it can adapt to the difference in thermal expansion between the carbon-based material and the conductive polymer. Second, the presence of nitrides or nitrogen groups can enhance the mechanical strength of the buffer layer, so that it can more effectively disperse and absorb these external forces when stressed, avoiding stress concentration and material fracture. In addition, the presence of the buffer layer can also reduce stress concentration by changing the interfacial bonding mode. Nitrogen atoms form stable interfacial structures with carbon-based materials and conductive polymers through hydrogen bonds, electrostatic adsorption or chemical bonding, enhancing the bonding force between materials. This enhanced interfacial bonding force allows the stress at the interface to be more evenly distributed and reduces the likelihood of interface damage. In step S3, after the action of the catalyst, a strong chemical bond is established between the carbonized carbon-based material and the conductive polymer, which not only improves the conductivity of the electrode material, but also enhances its cycle stability and long-term performance in energy storage devices such as batteries. This process can make the composite material exhibit higher energy density, excellent conductivity and better mechanical properties during battery operation.

[0007] As a preferred technical solution for the preparation method of a battery electrode carbon material, in step S1, the molecular weight of the polyethyleneimine is 1000-2000.

[0008] It should be noted that, on the one hand, the polyethyleneimine (PEI) has a molecular weight in the range of 1000 to 2000, has good solubility and dispersibility, and can be effectively dissolved in polar solvents such as ethanol; on the other hand, the moderate molecular weight enables the PEI to control the breaking and recombination process of the molecular chain during carbonization, thereby avoiding rapid gasification and ensuring that a stable nitrogen-doped layer can be formed on the surface of the carbon-based material.

[0009] As a preferred technical solution of the method for preparing the carbon material for battery electrodes, in step S2, the process parameters of the spray granulation are that the spray pressure is 0.5 to 2 MPa, the spray flow rate is 10-50 mL / min, and the nozzle aperture is 0.1-0.5 mm.

[0010] It should be noted that by reasonably adjusting these parameters, a particle morphology meeting the requirements can be obtained, thereby optimizing the material performance.

[0011] As a preferred technical solution of the method for preparing the carbon material for battery electrodes, in step S2, the carbonization temperature is 400-500℃.

[0012] It should be noted that, on the one hand, at the carbonization temperature of 400-500℃, the surface of the carbon-based material (such as carbon black) will undergo oxidation and reduction reactions to generate oxidizing functional groups such as carboxyl (-COOH) and hydroxyl (-OH), which significantly increase the surface activity of the carbon material; on the other hand, at the carbonization temperature, the molecular chain of the polyethyleneimine begins to gradually degrade, releasing nitrogen-containing gases such as ammonia (NH3) and nitrides. A suitable carbonization temperature (400-500℃) can ensure that the decomposition process of the polyethyleneimine is neither too violent nor too slow, and the nitrogen source is released at a relatively stable rate and reacts with the functional groups on the surface of the carbon-based material. These nitrogen atoms or nitrides can exist in the form of nitrogen heterocycles, pyridine rings, and pyrrole rings, and are embedded into the surface or lattice of the carbon-based material to form a nitrogen-doped layer.

[0013] As a preferred technical solution of the method for preparing the carbon material for battery electrodes, in step S3, the catalyst is ammonium persulfate.

[0014] It should be noted that ammonium persulfate as a catalyst, mainly through the production of strong oxidizing free radicals to promote the oxidative polymerization of conductive polymer, enhances the binding force of the polymer and the carbon-based material, and improves the conductivity of the composite material. The role of the catalyst is not only limited to the oxidative polymerization of the polymer, but also can optimize the polymerization state of the polymer, making its molecular chain more reactive. Through catalysis, the growth of the polymer chain can be effectively controlled, thereby forming a morphology that can better adapt to the surface structure of the carbon-based material. Specifically, the polymer chain may become more ordered under the action of the catalyst, or a relatively uniform coating is formed on the surface of the carbon-based material, thereby enhancing the binding force between the two.

[0015] As a preferred technical solution of the preparation method of the carbon material for battery electrode, in step S3, the conductive polymer is polyaniline.

[0016] It should be noted that when the catalyst (such as ammonium persulfate) decomposes, strong oxidizing free radicals are released, especially sulfate radicals (SO4· - ). These free radicals can effectively oxidize the aniline monomers of polyaniline, promote the oxidative polymerization reaction, and form polyaniline chains with high active reaction sites. The formation of polyaniline chains not only increases the conductivity of polyaniline, but also provides more reaction opportunities for the chemical bonding between polyaniline and the functional groups (such as carboxyl, hydroxyl, etc.) on the surface of the carbon-based material and the nitrogen-doped layer. Through these reaction sites, polyaniline can chemically react with the functional groups on the surface of the carbon-based material to form covalent bonds or hydrogen bonds, thereby enhancing the binding force between polyaniline and the carbon-based material.

[0017] As a preferred technical solution of the preparation method of the carbon material for battery electrode, in step S3, the mass ratio of the conductive polymer to the carbonized carbon material is (0.1 to 0.5):1;

[0018] And / or, the mass ratio of the catalyst to the conductive polymer is (0.01 to 0.05):1.

[0019] And / or, the control temperature of the reaction is 60 to 80°C, and the control time of the reaction is 2 to 3 hours.

[0020] It should be noted that by optimizing the mass ratio and reaction conditions of the conductive polymer, the carbonized carbon material, and the catalyst, a carbon material for battery electrode with good performance is prepared.

[0021] In addition, the present application provides a carbon material for battery electrode prepared by the above preparation method, which comprises a carbon-based material forming a buffer layer after carbonization treatment and a conductive polymer grafted on the surface of the carbon-based material forming a buffer layer.

[0022] It is worth noting that the buffer layer formed after carbonization of the carbon-based material has unique structure and chemical properties. This buffer layer not only improves the surface properties of the carbon-based material, but also effectively interacts with the conductive polymer. The formation of the buffer layer is achieved by controlling the carbonization temperature and time to adjust the surface state of the carbon-based material, making it more suitable for combination with the conductive polymer. The conductive polymer orderly branches on the surface of the buffer layer through oxidation polymerization and other reactions, forming a uniform coating, enhancing the conductivity and mechanical properties of the electrode. The role of the buffer layer is to adapt to the difference in thermal expansion between the carbon-based material and the conductive polymer, while improving the interfacial adhesion, ensuring the stability of the structure and high conductivity of the battery electrode during charging and discharging. Through this structural design, the overall performance of the battery electrode has been significantly improved, with better cycle stability and higher energy conversion efficiency.

[0023] As a preferred technical solution of the carbon material for battery electrodes, the carbon-based material includes carbon black.

[0024] It is worth noting that carbon black, as a commonly used carbon material, has a high specific surface area and conductivity. In the application of battery electrodes, carbon black is usually used as a conductive additive to effectively improve the conductivity of the electrode. The surface of carbon black contains a large number of micropores and carbon atoms, making it have good electrical conductivity and high chemical activity, and can form a strong and effective combination with the conductive polymer.

[0025] The present application provides a method for preparing a carbon material for battery electrodes. Through the dissolution, spray granulation and carbonization treatment of polyethyleneimine, a uniform buffer layer is formed on the surface of the carbon-based material, and nitrogen-doped functional groups are introduced. The buffer layer can effectively alleviate the interfacial stress problem caused by the difference in thermal expansion coefficient, significantly improving the structural stability and cycle life of the material; the introduction of nitrogen-doped functional groups (such as pyridine-type nitrogen, pyrrole-type nitrogen and graphite-type nitrogen) not only enhances the conductivity of the material, but also improves the interfacial adhesion through chemical combination with the conductive polymer, thereby optimizing the overall electrochemical performance. In addition, the spray granulation technology ensures the uniformity of the particles and the uniform distribution of the nitrogen source, forming a continuous conductive network during the carbonization process, further reducing the internal resistance. The material prepared by the preparation method of the present application exhibits excellent capacity retention rate and low internal resistance under high temperature charging and discharging conditions, has good cycle stability and electrochemical performance, is suitable for high-performance energy storage devices, and has significant technical and application advantages. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings are used to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0027] Figure 1Particle size distribution chart of the polyethyleneimine@carbon-based material composite prepared for step S2 of Example 1;

[0028] Figure 2 XRD chart of the carbonized carbon black material prepared for Example 1;

[0029] Figure 3 Infrared spectrum chart of the carbonized carbon black material prepared for Example 1. DETAILED DESCRIPTION

[0030] In order to make the above objectives, characteristics and advantages of the present application more apparent and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the description examples.

[0031] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, but the present application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present application, so the present application is not limited by the specific examples disclosed below.

[0032] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent of or mutually exclusive with other embodiments.

[0033] EMBODIMENT

[0034] EMBODIMENT 1

[0035] A preparation method of a carbon material for a battery electrode, characterized in that it comprises the following technical steps:

[0036] Step S1. Dissolve polyethyleneimine in ethanol to prepare a 5wt% solution, and stir until the polyethyleneimine is completely dissolved, wherein the molecular weight of the polyethyleneimine is 1000;

[0037] Step S2. Add carbon black material to the polyethyleneimine solution, with a mass ratio of polyethyleneimine to carbon black material of 0.1:1. Spray granulate the mixture solution to form a polyethyleneimine@carbon black material composite, and then carbonize the composite, with a carbonization temperature of 500°C, and the carbonization process being carried out in a nitrogen atmosphere; wherein the process parameters for spray granulation are a spray pressure of 2Mpa, a spray flow rate of 10mL / min, and a nozzle aperture of 0.1mm;

[0038] Step S3. Dissolve polyaniline in ethanol, add an appropriate amount of ammonium persulfate, stir until dissolved uniformly, add the carbonized carbon material to the reaction system, control the reaction temperature at 80℃, control the reaction time for 2 hours, to obtain a carbon material solution for battery electrodes, wherein the mass ratio of the polyaniline and the carbonized carbon material is 0.5:1, and the mass ratio of the catalyst and the polyaniline is 0.01:1.

[0039] The carbon material for battery electrodes prepared by the above preparation method comprises carbon black material forming a buffer layer after carbonization treatment and conductive polymer grafted on the surface of the carbon black material with the buffer layer.

[0040] Example 2

[0041] A preparation method of a carbon material for battery electrodes comprises the following technical steps:

[0042] Step S1. Dissolve polyethyleneimine in ethanol to prepare a 10wt% solution, and stir until the polyethyleneimine is completely dissolved, wherein the molecular weight of the polyethyleneimine is 1500;

[0043] Step S2. Add carbon black material to the polyethyleneimine solution, and the mass ratio of the polyethyleneimine to the carbon black material is 0.5:1. Spray granulate the mixture solution to form a polyethyleneimine@carbon black material composite material, and then carbonize the composite material, wherein the carbonization temperature is 400℃, and the carbonization process is carried out in a nitrogen atmosphere; the process parameters of the spray granulation are a spray pressure of 0.5Mpa, a spray flow rate of 20mL / min, and a nozzle aperture of 0.5mm;

[0044] Step S3. Dissolve polyaniline in ethanol, add an appropriate amount of ammonium persulfate, stir until dissolved uniformly, add the carbonized carbon material to the reaction system, control the reaction temperature at 60℃, control the reaction time for 3 hours, to obtain a carbon material solution for battery electrodes, wherein the mass ratio of the polyaniline and the carbonized carbon material is 0.1:1, and the mass ratio of the catalyst and the polyaniline is 0.02:1.

[0045] The carbon material for battery electrodes prepared by the above preparation method comprises carbon black material forming a buffer layer after carbonization treatment and conductive polymer grafted on the surface of the carbon black material with the buffer layer.

[0046] Example 3

[0047] A preparation method of a carbon material for battery electrodes comprises the following technical steps:

[0048] Step S1. Dissolve polyethyleneimine in ethanol to prepare a 8wt% solution, stir until the polyethyleneimine is completely dissolved, wherein the molecular weight of the polyethyleneimine is 2000;

[0049] Step S2. Add carbon black material to the polyethyleneimine solution, the mass ratio of polyethyleneimine to carbon black material is 0.3:1, spray granulation is performed on the mixture solution to form a polyethyleneimine@carbon black material composite material, and the composite material is then subjected to carbonization treatment, the temperature of the carbonization treatment is 450℃, and the carbonization process is carried out in a nitrogen atmosphere; the process parameters of the spray granulation are that the spray pressure is 1Mpa, the spray flow rate is 50mL / min, and the nozzle aperture is 0.3mm;

[0050] Step S3. Dissolve polyaniline in ethanol, add an appropriate amount of ammonium persulfate, stir until dissolved uniformly, add the carbonized carbon-based material to the reaction system, control the reaction temperature to be 70℃, and control the reaction time to be 2 hours to obtain a carbon material solution for battery electrodes, wherein the mass ratio of the polyaniline to the carbonized carbon-based material is 0.3:1, and the mass ratio of the catalyst to the polyaniline is 0.05:1.

[0051] The carbon material for battery electrodes prepared by the above preparation method includes carbon black material forming a buffer layer after carbonization treatment and conductive polymer dendrites on the surface of the carbon black material forming the buffer layer

[0052] Example 4

[0053] A preparation method of a carbon material for battery electrodes, comprising the following technical steps:

[0054] Step S1. Dissolve polyethyleneimine in ethanol to prepare a 7wt% solution, stir until the polyethyleneimine is completely dissolved, wherein the molecular weight of the polyethyleneimine is 1500;

[0055] Step S2. Add carbon black material to the polyethyleneimine solution, the mass ratio of polyethyleneimine to carbon black material is 0.2:1, spray granulation is performed on the mixture solution to form a polyethyleneimine@carbon black material composite material, and the composite material is then subjected to carbonization treatment, the temperature of the carbonization treatment is 500℃, and the carbonization process is carried out in a nitrogen atmosphere; wherein the process parameters of the spray granulation are that the spray pressure is 1.5Mpa, the spray flow rate is 40mL / min, and the nozzle aperture is 0.4mm;

[0056] Step S3. Dissolve polyaniline in ethanol, add an appropriate amount of ammonium persulfate, stir until dissolved uniformly, add the carbon-based material after carbonization to the reaction system, control the reaction temperature at 80°C, control the reaction time for 3 hours, to obtain a carbon material solution for battery electrodes, wherein the mass ratio of the polyaniline to the carbon-based material after carbonization is 0.4:1, and the mass ratio of the catalyst to the polyaniline is 0.05:1.

[0057] The carbon material for battery electrodes prepared by the preparation method described above comprises carbon black material forming a buffer layer after carbonization treatment and conductive polymer grafted on the surface of the carbon black material with the buffer layer.

[0058] Example 5

[0059] A preparation method of a carbon material for battery electrodes comprises the following technical steps:

[0060] Step S1. Dissolve polyethyleneimine in ethanol to prepare an 8wt% solution, and stir until the polyethyleneimine is completely dissolved, wherein the molecular weight of the polyethyleneimine is 1800;

[0061] Step S2. Add carbon black material to the polyethyleneimine solution, and the mass ratio of the polyethyleneimine to the carbon black material is 0.2:1. Spray granulate the mixture solution to form a polyethyleneimine@carbon black material composite material, and then perform carbonization treatment on the composite material, wherein the carbonization treatment temperature is 300°C, and the carbonization process is performed in a nitrogen atmosphere; wherein the process parameters of the spray granulation are a spray pressure of 2.0Mpa, a spray flow rate of 40mL / min, and a nozzle aperture of 0.4mm;

[0062] Step S3. Dissolve polyaniline in ethanol, add an appropriate amount of ammonium persulfate, stir until dissolved uniformly, add the carbon-based material after carbonization to the reaction system, control the reaction temperature at 80°C, control the reaction time for 3 hours, to obtain a carbon material solution for battery electrodes, wherein the mass ratio of the polyaniline to the carbon-based material after carbonization is 0.2:1, and the mass ratio of the catalyst to the polyaniline is 0.04:1.

[0063] The carbon material for battery electrodes prepared by the preparation method described above comprises carbon black material forming a buffer layer after carbonization treatment and conductive polymer grafted on the surface of the carbon black material with the buffer layer.

[0064] Examples 6 to 11

[0065] Examples 6 to 11 differ from Example 5 in that the carbonization treatment temperature is different, as shown in Table 1 below.

[0066] Table 1 Carbonization treatment temperature of Examples 5 to 11

[0067]

[0068]

[0069] Comparative Example

[0070] Comparative Example 1

[0071] The difference between the comparative example and Example 1 is that the carbon black material is not added to the polyethyleneimine solution, and the carbon black material is directly carbonized at 500°C.

[0072] Comparative Example 2

[0073] The difference between the comparative example and Example 2 is that the carbon black material is added to the polyethyleneimine solution, and no spray granulation treatment is performed, and the carbonization treatment is directly performed.

[0074] Table 2 is the process parameters of Examples 1 to 11 and Comparative Examples 1 to 2

[0075] Examples M1 M2 M3 M4 M5 M6 Example 1 5 wt% 1000 0.1:1 500℃ 0.5:1 0.01:1 Example 2 10 wt% 1500 0.5:1 400℃ 0.1:1 0.02:1 Example 3 8 wt% 2000 0.3:1 450℃ 0.3:1 0.05:1 Example 4 7 wt% 1500 0.2:1 500℃ 0.4:1 0.05:1 Example 5 8 wt% 1800 0.2:1 300℃ 0.2:1 0.04:1 Example 6 8 wt% 1800 0.2:1 350℃ 0.2:1 0.04:1 Example 7 8 wt% 1800 0.2:1 400℃ 0.2:1 0.04:1 Example 8 8 wt% 1800 0.2:1 450℃ 0.2:1 0.04:1 Example 9 8 wt% 1800 0.2:1 500℃ 0.2:1 0.04:1 Example 10 8 wt% 1800 0.2:1 550℃ 0.2:1 0.04:1 Example 11 8 wt% 1800 0.2:1 600℃ 0.2:1 0.04:1 Control Example 1 / / / 500℃ 0.5:1 0.01:1 Control Example 2 10 wt% 1500 0.5:1 400℃ 0.1:1 0.02:1

[0076] Note: M1 represents the concentration of the polyethyleneimine solution; M2 represents the molecular weight of the polyethyleneimine; M3 represents the mass ratio of the polyethyleneimine to the carbon black material; M4 represents the temperature of the carbonization treatment; M5 represents the mass ratio of the polyaniline to the carbon material after the carbonization; and M6 represents the mass ratio of the catalyst to the polyaniline.

[0077] Performance detection test

[0078] 1. Particle size distribution test: the particle size of the polyethyleneimine@carbon-based material composite prepared in step S2 of Example 1 is tested;

[0079] 2. XRD test: the carbonized carbon black material prepared in Example 1 is subjected to XRD test;

[0080] 3. Infrared spectrum test: the carbonized carbon black material prepared in Example 1 is subjected to infrared spectrum test;

[0081] 4. Electrochemical performance test:

[0082] Preparation of the negative electrode material: the carbon material solution prepared in the present application, the conductive agent, and the polyvinylidene fluoride are mixed and uniformly coated on a copper foil, and the coating thickness of the negative electrode material is generally between 50-150 μm. The coated electrode is placed in an oven for drying, and the dried electrode material needs to be compacted by a press. The compacted negative electrode material is cut according to the size of the battery design.

[0083] Preparation of positive electrode material: Lithium cobalt oxide LiCoO2 was selected and mixed with conductive agent and polyvinylidene fluoride to form a slurry, similar to the preparation process of the negative electrode. The slurry was coated on an aluminum foil as a positive electrode.

[0084] Battery assembly: The positive electrode, separator and negative electrode material were stacked in turn in a laminated manner. Then, after the battery shell was prepared, the electrolyte was injected, which was a solution of lithium salt (LiPF6) dissolved in an organic solvent.

[0085] High-temperature charge-discharge test: First, the battery was placed in a temperature-controlled environmental chamber to ensure a constant temperature of 80°C. Using the constant current charge-discharge method, a charge-discharge current of 1C was set, and multiple charge-discharge cycles were performed within the specified voltage range, with 200 charge-discharge cycles. The voltage, current, capacity change and temperature of the battery were recorded, and the capacity retention rate and internal resistance change were calculated.

[0086] Table 3 shows the electrical properties of Examples 1 to 11 and Comparative Examples 1 to 2

[0087]

[0088]

[0089] In combination with Example 1 and Figure 1 It can be seen that the particle size distribution of the polyethyleneimine@carbon-based material composite prepared in step S2 of Example 1 exhibits typical normal distribution characteristics, indicating that the particle size of the material is relatively concentrated within a certain range, mainly around the average value. This indicates that the particle size uniformity is high. The distribution curve is unimodal and smooth, with a rapid decline in the tail, and there is no double or multiple peak phenomenon, nor is there an obvious high tail in the large particle size region. This indicates that the dispersion of the particles during the preparation process is good, and no significant agglomeration phenomenon occurs. From the particle size range in the figure, the particles are mainly distributed in the range of 50 nm to 150 nm, and are concentrated between 85 nm and 115 nm, with a relatively narrow particle size distribution and good uniformity.

[0090] In combination with Example 1 and Figure 2It can be seen that after nitrogen doping, the diffraction peak position of the 002 plane of the carbon black XRD is shifted to the left from 2θ≈25° to a lower angle compared to the XRD of the carbon black, indicating that nitrogen doping causes the expansion of the carbon black lattice, which may be due to the electronic effect of nitrogen atoms and the stress introduced during the doping process; the intensity of the main peak decreases, and the peak width increases slightly, indicating that nitrogen doping introduces more lattice defects and disorder, reducing the crystallinity of the carbon black; the background noise increases slightly, which may reflect the increase in the proportion of amorphous carbon due to nitrogen doping; these changes indicate that nitrogen doping significantly affects the microstructure of the carbon black, not only changing the lattice spacing, but also reducing the order of the material, while giving the carbon black higher chemical activity and electrochemical performance.

[0091] In combination with Example 1 and Figure 3 It can be seen that after carbonization treatment, a series of new functional groups will be formed on the surface of the polyethyleneimine@carbon-based material composite due to high-temperature decomposition and chemical reaction. The nitrogen atoms in the polyethyleneimine are embedded in the carbon-based material through carbonization, forming pyridine-type nitrogen (C=N, absorption peak at 1550 cm -1 ), pyrrole-type nitrogen (C-N, absorption peak at 1350 cm -1 ) and graphite-type nitrogen (N embedded in graphite structure, absorption peak at 1200 cm -1 ) and other nitrogen functional groups, which are typical characteristics of nitrogen doping. In addition, high-temperature treatment may introduce a small amount of cyano group (C≡N), which is characterized by a characteristic peak near 2200 cm -1 in the infrared spectrum. At the same time, due to the surface oxidation during the carbonization process, the sample may have a small amount of oxidation functional groups, such as carbonyl (C=O, characteristic peak at about 1720 cm -1 ) and carboxyl (-COOH, characteristic peak at about 1200 cm -1 ). These oxygen-containing functional groups are usually derived from the action of oxygen or moisture in the environment during the carbonization process. In addition, the surface of the composite material may have a small amount of O-H and N-H stretching vibration characteristic peaks (about 3400 cm -1 ), corresponding to amino or hydroxyl groups. Overall, carbonization treatment gives the composite material the characteristics of nitrogen-containing and oxygen-containing functional groups, significantly enhancing its surface activity.

[0092] As can be seen from Examples 1 to 4 in combination with Table 3, the capacity retention of the material prepared in the present application ranges from 75.8% to 81.4%, and the internal resistance ranges from 8.5 mΩ to 12.4 mΩ. This performance is due to the preparation technology of the present application, including carbonization treatment, spray granulation and grafting of conductive polymer. The carbonization treatment forms a stable "buffer layer" on the surface of the carbon black material and introduces nitrogen-containing functional groups, which significantly improves the electrical conductivity and chemical stability of the material; the spray granulation technology ensures the uniformity of the particles and the uniform distribution of nitrogen elements, optimizing the conductive network; and the grafting of conductive polymer further enhances the electronic conduction ability of the material. The organic combination of these technologies makes the material exhibit excellent cycle stability and low internal resistance under high-temperature charge and discharge conditions, fully verifying the scientificity and practicality of the preparation method of the present application.

[0093] As can be seen from Examples 5 to 11 in combination with Table 3, as the temperature of carbonization treatment (300°C to 600°C) gradually increases, the capacity retention of the battery first gradually increases and then decreases, and the internal resistance of the battery first gradually decreases and then increases. When the temperature of carbonization treatment is 400°C to 500°C, the capacity retention of the battery and the internal resistance of the battery remain optimal, mainly because the appropriate carbonization temperature (400-500°C) can ensure that the decomposition process of polyethyleneimine is neither too violent nor too slow, and the nitrogen source is released at a relatively stable rate and reacts with the functional groups on the surface of the carbon-based material. These nitrogen atoms or nitrides can exist in the form of nitrogen heterocycle, pyridine ring, pyrrole ring, etc., and are embedded into the surface or lattice of the carbon-based material to form a nitrogen-doped layer.

[0094] As can be seen from Example 1, Comparative Example 1 and Table 3, the capacity retention of Example 1 is 81.4%, and the internal resistance is 8.5 mΩ, which is significantly better than the 75.8% capacity retention and 12.4 mΩ internal resistance of Comparative Example 1. The mechanism of this performance improvement mainly lies in the synergistic effect of the buffer layer and nitrogen-containing functional groups formed by carbonization of polyethyleneimine on the surface of carbon black. The buffer layer can effectively slow down the interface stress concentration caused by the difference in expansion coefficient during charge and discharge, enhancing the structural stability of the material and thus avoiding performance degradation; the introduction of nitrogen-containing functional groups (such as pyridine nitrogen, pyrrole nitrogen and graphite nitrogen) not only improves the electrical conductivity of the material, but also forms strong bonds with polyaniline through hydrogen bonds or chemical bonds, optimizing the interface stability. In addition, the generation of graphite nitrogen significantly improves the electron transfer efficiency of the material, further reducing the internal resistance. The above mechanisms make Example 1 exhibit excellent cycle stability and electrochemical performance under high-temperature charge and discharge conditions.

[0095] As can be seen from Example 2, Comparative Example 2 and Table 3, the capacity retention of Example 2 is 79.6% and the internal resistance is 9.2 mΩ, while the capacity retention of Comparative Example 2 is 74.3% and the internal resistance is 13.7 mΩ. The performance of Example 2 is significantly better than that of Comparative Example 2, mainly because the spray granulation technology is used. The spray granulation can make the polyethyleneimine and carbon black uniformly distributed, ensure the uniformity of the morphology of the particles and the uniform distribution of the nitrogen source, so as to form a uniform and continuous conductive network in the carbonization process. This uniformity not only reduces the conductive island phenomenon in the material, but also improves the interface bonding strength, thereby significantly reducing the internal resistance, while improving the structural stability and ion conduction ability of the electrode. These characteristics make Example 2 exhibit more excellent cycle stability and electrochemical performance under high-temperature charge and discharge conditions, further proving the key role of the spray granulation technology in optimizing the performance of the electrode material.

[0096] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a carbon material for a battery electrode, characterized in that, The technical steps include the following: Step S1. Dissolve polyethyleneimine in ethanol and stir until polyethyleneimine is completely dissolved, wherein the polyethyleneimine is prepared as a 5 to 10 wt% solution; Step S2. Add carbon-based material to polyethyleneimine solution, spray granulate the mixture solution to form a composite material of polyethyleneimine@carbon-based material, and then perform carbonization treatment on the composite material in a nitrogen atmosphere; Step S3. Dissolve the conductive polymer in ethanol, add an appropriate amount of catalyst, stir until the solution is uniform, add the carbonized composite material to the reaction system to obtain a carbon material solution for battery electrodes.

2. The method for preparing carbon material for battery electrodes according to claim 1, characterized in that, In step S1, the molecular weight of the polyethyleneimine is 1000 to 2000.

3. The method for preparing carbon material for battery electrodes according to claim 1, characterized in that, In step S2, the process parameters for spray granulation are: spray pressure of 0.5 to 2 MPa, spray flow rate of 10-50 mL / min, and nozzle orifice diameter of 0.1-0.5 mm.

4. The method for preparing carbon material for battery electrodes according to claim 1, characterized in that, In step S2, the carbonization temperature is 400-500℃.

5. The method for preparing carbon material for battery electrodes according to claim 1, characterized in that, In step S3, the catalyst is ammonium persulfate.

6. The method for preparing carbon material for battery electrodes according to claim 1, characterized in that, In step S3, the conductive polymer is polyaniline.

7. The method for preparing carbon material for battery electrodes according to claim 1, characterized in that, In step S3, the mass ratio of the conductive polymer to the carbonized carbon material is (0.1 to 0.5):1; The mass ratio of the catalyst to the conductive polymer is (0.01 to 0.05):

1. The reaction temperature is controlled at 60 to 80°C, and the reaction time is controlled at 2 to 3 hours.

8. A carbon material for battery electrodes prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The carbon material used for the battery electrode includes a carbon-based material that has undergone carbonization to form a buffer layer and a conductive polymer grafted onto the surface of the carbon-based material with the buffer layer.

9. The carbon material for battery electrodes according to claim 8, characterized in that, The carbon-based material includes carbon black.

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