Preparation method of carbon black-based composite conductive agent for automobile lithium battery

Abstract

A preparation method of a carbon black-based composite conductive agent for an automobile lithium battery belongs to the technical field of new energy automobile lithium batteries, and comprises the following steps: depositing conductive carbon black on the surface and gaps of MOF-Ni3 (HITP) 2 by adopting a vapor deposition method to obtain MOF-Ni3 (HITP) 2 loaded carbon black, and then carrying out surface modification on the MOF-Ni3 (HITP) 2 loaded carbon black by adopting a spraying agent to obtain the carbon black-based composite conductive agent for the automobile lithium battery. The carbon black-based composite conductive agent is obtained. The spraying agent is prepared from water, polyvinyl alcohol, waterborne polyurethane, behenamidopropyl dimethylamine and fatty alcohol-polyoxyethylene ether. The carbon black-based composite conductive agent prepared by the invention can greatly improve the dispersibility of the conductive agent, improve the conductivity and the conductive stability in long-term use, has very good high-rate charge-discharge efficiency, and improves the rate capability of a lithium iron phosphate battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy automobile lithium batteries, and specifically relates to a method for preparing a carbon black-based composite conductive agent for automobile lithium batteries. Background Art

[0002] As the power source of electric vehicles, lithium batteries have many advantages: high energy density, long service life, and high charging and discharging efficiency. In recent years, lithium battery technology has continued to advance. On the one hand, the development of materials science has continuously improved the performance of key components such as positive and negative electrode materials, conductive materials, electrolytes, and separators of lithium batteries. For example, new ternary cathode materials and lithium iron phosphate cathode materials have higher specific capacity and better safety; the research and development of solid electrolytes is expected to further improve the safety and energy density of lithium batteries.

[0003] Among them, lithium iron phosphate batteries have been widely used in electric vehicles, energy storage systems and other fields. The positive and negative conductive agents play a vital role in lithium iron phosphate batteries. In the early research on lithium iron phosphate batteries, people gradually realized that the conductivity of lithium iron phosphate itself is low. This characteristic limits the charge and discharge performance and energy output of the battery, so it is necessary to add a conductive agent to improve the conductivity of the electrode. The conductive agents initially used were mainly traditional carbon black materials, such as acetylene black, conductive carbon black, etc. These granular conductive agents are relatively cheap, easy to use, and can improve the conductivity of the electrode to a certain extent. However, their conductive properties still have room for improvement, and their performance in high-rate charge and discharge conditions is not satisfactory, and carbon black with smaller particle size is easy to agglomerate in the slurry and difficult to disperse evenly.

[0004] With the continuous development of materials science, new conductive agents are gradually being developed and applied. Carbon nanotubes are an important representative of them. Carbon nanotubes have a high aspect ratio and excellent conductivity. They can form a good conductive network in the electrode and improve the transmission efficiency of electrons. However, the preparation process of carbon nanotubes is relatively complicated and difficult to be widely used. In addition, the dispersion of carbon nanotubes is poor. There are strong van der Waals forces between carbon nanotubes, which are easy to agglomerate in the positive electrode slurry, resulting in poor dispersion in the electrode material. If the dispersion is uneven, it will affect the formation of the conductive network of the conductive agent in the electrode, thereby reducing the performance of the battery. Graphene is also a new type of conductive agent that has attracted much attention in recent years. Graphene is a two-dimensional sheet structure material composed of carbon atoms, with extremely high specific surface area and excellent conductive properties. At the same time, graphene is expensive and difficult to disperse. Graphene is a sheet structure, and there are strong van der Waals forces and π-π interactions between the sheets, which makes graphene easy to agglomerate in the positive electrode slurry and difficult to disperse evenly; this will not only affect the performance of the graphene conductive agent in the electrode, but also increase the difficulty and cost of dispersion in the production process. In addition, graphene also has functional group problems. Graphene prepared by redox method or biomass catalysis method usually contains a large number of surface functional groups such as carboxyl, hydroxyl, and epoxy. The presence of these functional groups will increase the amount of electrolyte absorbed and reduce the energy density of the battery on the one hand; on the other hand, it will reduce the conductivity of graphene to a certain extent, affecting the performance of the battery.

[0005] In practical applications, the selection and use of positive and negative electrode conductive agents need to comprehensively consider multiple factors, such as battery application scenarios, performance requirements, etc. For application scenarios with high power performance requirements such as electric vehicles, it is necessary to select conductive agents with excellent conductivity. Therefore, it is necessary to continuously develop more efficient and practical conductive agents to support the performance of batteries and promote the continuous development of lithium iron phosphate battery technology. Summary of the invention

[0006] The acetylene black and conductive carbon black conductive agents used in existing lithium iron phosphate batteries have poor high-rate charge and discharge effects, high dispersion costs for carbon nanotubes and graphene, and high dispersion difficulty for conductive agents with smaller particle sizes, which affects the stability of conductive performance. The present invention provides a method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, wherein the conductive carbon black is deposited on MOF-Ni by a vapor deposition method. 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Load carbon black, and then use a special spray to spray MOF-Ni 3 (HITP) 2The surface of the loaded carbon black is modified to obtain a carbon black-based composite conductive agent, which can greatly improve the dispersibility of the conductive agent, improve the conductivity and long-term conductivity stability, and has a good high-rate charge and discharge efficiency. The specific technical solution is as follows: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries comprises the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder is dried and then irradiated with ultraviolet light to increase surface activity; S2, sample loading: the pretreated MOF-Ni 3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, wherein the gas contains a carrier gas and a carbon source gaseous precursor, and the volume ratio of the carrier gas to the carbon source gaseous precursor is 100:(3-10); S4, deposition of carbon black: the chemical vapor deposition furnace is heated to 600°C to 800°C, the gas flow rate is 800mL / min to 1500mL / min, and the deposition reaction is 1.5h to 3h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Loading carbon black; S5, surface modification: S5.1: Mix and prepare the following according to the mass ratio: water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether = (80-100): (1-2.5): (0.5-1.5): (0.5-1.5): (0.3-0.8) to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3 (HITP) 2 The carbon black is loaded for surface coating modification and dried to obtain a carbon black-based composite conductive agent for automotive lithium batteries.

[0007] In S1 of the above preparation method, the drying is vacuum drying, the drying temperature is 60° C. to 80° C., and the drying time is more than 20 minutes.

[0008] In S1 of the above preparation method, the ultraviolet irradiation time is 30 min to 50 min.

[0009] In S3 of the above preparation method, the carrier gas is nitrogen or argon, and the carbon source gaseous precursor is acetylene.

[0010] In S3 of the above preparation method, the flow rate of the gas is 500 mL / min to 1500 mL / min.

[0011] In S4 of the above preparation method, the heating rate is 5°C / min to 8°C / min.

[0012] In S5.1 of the above preparation method, the mixing temperature is 40°C to 60°C.

[0013] In S5.2 of the above preparation method, the parameters of the fluidized spray are: spray inlet temperature 30°C to 35°C, spray speed 0.25L / min to 0.35L / min, atomization pressure 0.5MPa to 0.6MPa, and discharge temperature 50°C to 60°C.

[0014] In S5.2 of the above preparation method, the drying temperature is 70°C to 80°C.

[0015] Compared with the prior art, the method for preparing a carbon black-based composite conductive agent for automotive lithium batteries of the present invention has the following beneficial effects: 1. MOF-Ni 3 (HITP) 2 It has a unique three-dimensional porous structure, which provides abundant channels and a large specific surface area for electron transmission, and can enhance the interaction with carbon black, making the transmission of electrons in the composite material more efficient. 3 (HITP) 2 Loading carbon black can form a more complete and continuous conductive network, thereby significantly improving the conductive performance. Carbon black itself has a certain conductivity, but there is agglomeration phenomenon, which limits its conductive performance. 3 (HITP) 2 Due to the dispersion effect of MOF, the carbon black on the surface is reduced, and the conductive performance of carbon black is better exerted. Carbon black reduces resistivity and realizes conductivity by forming a conductive network in the polymer matrix. 3 (HITP) 2 The presence of provides more attachment sites and conductive channels for carbon black. The synergistic effect of the two enables electrons to be transmitted more quickly in the composite material, thereby improving the overall conductive properties.

[0016] 2. During high current charging and discharging (i.e. rate performance test), MOF-Ni 3 (HITP) 2Loaded carbon black can better adapt to rapid electron transport and ion diffusion. The porous structure of MOF is conducive to the penetration of electrolyte and the transmission of ions, while carbon black provides good electron conductivity. The combination of the two enables the composite material to maintain good performance stability of the battery under high-rate charge and discharge. Pure carbon black is prone to local current concentration and electrode polarization during high-rate charge and discharge due to the relatively poor stability of its conductive network, resulting in a decrease in rate performance. MOF-Ni 3 (HITP) 2 The structural stability of loaded carbon black is higher, which can effectively alleviate these problems and improve the rate performance. The rate performance depends on the electron transmission speed and ion diffusion speed of the electrode material at high current density. 3 (HITP) 2 The three-dimensional structure provides a channel for rapid transmission of ions and electrons, and the high conductivity of carbon black ensures the rapid transfer of electrons. The combined effect of the two enables the composite material to maintain good performance during high-rate charge and discharge.

[0017] 3. MOF-Ni 3 (HITP) 2 It has high chemical stability and structural stability, and can maintain structural integrity during the charge and discharge process. The carbon black loaded on it can be protected by MOF, reducing the decrease in conductivity caused by volume change and structural damage of the electrode material. 3 (HITP) 2 Loaded carbon black has better cycle stability and can maintain high conductivity after multiple charge and discharge cycles. Pure carbon black is easily corroded by the electrolyte and affected by the volume change of the electrode material during long-term charge and discharge cycles, resulting in the destruction of the conductive network and relatively poor cycle performance. The quality of the cycle performance is closely related to the structural stability and conductivity stability of the electrode material during the charge and discharge process. MOF-Ni 3 (HITP) 2 The stable structure provides stable support and protection for carbon black, enabling the composite material to maintain good conductivity and structural stability during long-term charge and discharge cycles, thereby improving the cycle performance.

[0018] 4. The present invention uses a spray to treat MOF-Ni 3 (HITP) 2 Carbon black is loaded for surface modification. In the spray, polyvinyl alcohol has good film-forming and adhesion properties and can be used on MOF-Ni 3 (HITP) 2A uniform film is formed on the surface of the loaded carbon black, which improves the structural stability and mechanical strength of the composite material. At the same time, polyvinyl alcohol can also improve the adhesion between the electrode material and the current collector, reduce the shedding and damage of the electrode during the charge and discharge process, thereby improving the cycle performance and service life of the battery. Waterborne polyurethane has excellent flexibility and wear resistance, which can improve the flexibility and wear resistance of the conductive agent material, reduce the damage of the electrode during use, and provide good protection for the composite material. Behenamidopropyl dimethylamine has conductivity and dispersibility, which can improve MOF-Ni 3 (HITP) 2 The dispersion of carbon black in the electrode slurry can be improved, reducing agglomeration and improving the uniformity and consistency of the electrode. At the same time, behenamidopropyl dimethylamine can also reduce the surface resistance of the electrode material and improve the conductivity of the battery. Fatty alcohol polyoxyethylene ether can improve MOF-Ni 3 (HITP) 2 The fluidity and coating performance of the loaded carbon black in the slurry can be more evenly coated on the current collector, improving the quality and performance of the electrode. Fatty alcohol polyoxyethylene ether is also conducive to the penetration of electrolyte and the transmission of ions, thereby improving the rate performance and cycle performance of the battery. The use of fatty alcohol polyoxyethylene ether in combination with behenamidopropyl dimethylamine can improve the homogeneity of the coating agent.

[0019] 5. MOF-Ni 3 (HITP) 2 Drying and ultraviolet irradiation are performed. Drying is used to remove moisture and volatile impurities and improve surface activity. Ultraviolet irradiation changes the surface structure of the particles and improves their surface activity. It can improve the deposition and bonding of conductive carbon black and improve conductivity.

[0020] 6. The present invention is based on the deposition characteristics of conductive carbon black and MOF-Ni 3 (HITP) 2 The deposition parameters are designed based on the structural characteristics of the conductive carbon black. The heating rate is designed to be 5℃ / min~8℃ / min to avoid thermal shock and uneven deposition of the sample. The deposition temperature is between 600℃ and 800℃. If the temperature is too low, the carbon layer structure of carbon black will be unstable, and the carbon layer will be in a relatively messy stage, which will affect ion transport and the conductivity will be relatively poor. The gas flow rate is controlled at 500mL / min~1500mL / min. Too large a gas flow rate will affect the deposition stability of the conductive carbon black. Too small a flow rate will affect the deposition amount of the conductive carbon black, which will in turn affect the decrease in conductivity and the low charging and discharging efficiency of the battery. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0022] Embodiment 1: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, comprising the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder was dried at 70°C for 40 min and then irradiated with ultraviolet light for 40 min to increase the surface activity; S2, sample loading: the pretreated MOF-Ni 3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, the gas flow rate is 1000 mL / min, the gas contains carrier gas and carbon source gaseous precursor, the volume ratio of carrier gas to carbon source gaseous precursor is 100:6; the carrier gas is nitrogen, and the carbon source gaseous precursor is acetylene; S4, deposition of carbon black: the chemical vapor deposition furnace was heated to 700°C at a heating rate of 6°C / min, the gas flow rate was 1000mL / min, and the deposition reaction was carried out for 2h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Loading carbon black; S5, surface modification: S5.1: Mix and prepare water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether at a mass ratio of 90:1.8:1.0:1.0:0.5 at 50° C. to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3 (HITP) 2 The carbon black is loaded for surface coating modification, and dried at 75° C. to obtain a carbon black-based composite conductive agent for automotive lithium batteries; The parameters of fluidized spraying are: spray inlet temperature 32°C, spray speed 0.30L / min, atomization pressure 0.55MPa, and discharge temperature 55°C.

[0023] Embodiment 2: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, comprising the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder was dried at 60°C for 20 min and then irradiated with ultraviolet light for 30 min to increase the surface activity; S2, sample loading: the pretreated MOF-Ni3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, the gas flow rate is 500 mL / min, the gas contains carrier gas and carbon source gaseous precursor, the volume ratio of carrier gas to carbon source gaseous precursor is 100:3; the carrier gas is nitrogen, and the carbon source gaseous precursor is acetylene; S4, deposition of carbon black: the chemical vapor deposition furnace was heated to 600°C at a heating rate of 5°C / min, the gas flow rate was 800 mL / min, and the deposition reaction was performed for 1.5 h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Loading carbon black; S5, surface modification: S5.1: Mix and prepare water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether in a mass ratio of 80:1:0.5:0.5:0.3 at 40° C. to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3 (HITP) 2 The carbon black is loaded for surface coating modification, and dried at 70° C. to obtain a carbon black-based composite conductive agent for automotive lithium batteries; The parameters of fluidized spraying are: spray inlet temperature 30°C, spray speed 0.25L / min, atomization pressure 0.5MPa, and discharge temperature 50°C.

[0024] Embodiment 3: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, comprising the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder was dried at 65°C for 30 min and then irradiated with ultraviolet light for 35 min to increase the surface activity; S2, sample loading: the pretreated MOF-Ni 3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, the gas flow rate is 600 mL / min, the gas contains carrier gas and carbon source gaseous precursor, the volume ratio of carrier gas to carbon source gaseous precursor is 100:4.5; the carrier gas is nitrogen, and the carbon source gaseous precursor is acetylene; S4, deposition of carbon black: the chemical vapor deposition furnace was heated to 650°C at a heating rate of 6°C / min, the gas flow rate was 800 mL / min, and the deposition reaction was carried out for 2 h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Loading carbon black; S5, surface modification: S5.1: Mix and prepare water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether in a mass ratio of 85:1.4:0.6:0.7:0.4 at 45°C to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3 (HITP) 2 The carbon black is loaded for surface coating modification and dried at 72°C to obtain a carbon black-based composite conductive agent for automotive lithium batteries; The parameters of fluidized spraying are: spray inlet temperature 32°C, spray speed 0.25L / min, atomization pressure 0.52MPa, and discharge temperature 52°C.

[0025] Embodiment 4: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, comprising the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder was dried at 75°C for 50 min and then irradiated with ultraviolet light for 45 min to increase the surface activity; S2, sample loading: the pretreated MOF-Ni 3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, the gas flow rate is 1200 mL / min, the gas contains carrier gas and carbon source gaseous precursor, the volume ratio of carrier gas to carbon source gaseous precursor is 100:8.5; the carrier gas is nitrogen, and the carbon source gaseous precursor is acetylene; S4, deposition of carbon black: the chemical vapor deposition furnace was heated to 750°C at a heating rate of 7°C / min, the gas flow rate was 1200 mL / min, and the deposition reaction was performed for 2.5 h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2Loading carbon black; S5, surface modification: S5.1: Mix and prepare at 55° C. the mass ratio of water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether = 95:2.0:1.2:1.3:0.7 to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3 (HITP) 2 The carbon black is loaded for surface coating modification and dried at 78°C to obtain a carbon black-based composite conductive agent for automotive lithium batteries; The parameters of fluidized spraying are: spray inlet temperature 34°C, spray speed 0.32L / min, atomization pressure 0.58MPa, and discharge temperature 58°C.

[0026] Embodiment 5: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, comprising the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder was dried at 80°C for 60 min and then irradiated with ultraviolet light for 50 min to increase the surface activity; S2, sample loading: the pretreated MOF-Ni 3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, the gas flow rate is 1500 mL / min, the gas contains carrier gas and carbon source gaseous precursor, the volume ratio of carrier gas to carbon source gaseous precursor is 100:10; the carrier gas is nitrogen, and the carbon source gaseous precursor is acetylene; S4, deposition of carbon black: the chemical vapor deposition furnace was heated to 800°C at a heating rate of 8°C / min, the gas flow rate was 1500mL / min, and the deposition reaction was carried out for 3h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Loading carbon black; S5, surface modification: S5.1: Mix and prepare water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether in a mass ratio of 100:2.5:1.5:1.5:0.8 at 60° C. to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3(HITP) 2 The carbon black is loaded for surface coating modification, and dried at 80°C to obtain a carbon black-based composite conductive agent for automotive lithium batteries; The parameters of fluidized spraying are: spray inlet temperature 35°C, spray speed 0.35L / min, atomization pressure 0.6MPa, and discharge temperature 60°C.

[0027] Embodiment 6: A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, comprising the following steps: S1, sample pretreatment: MOF-Ni 3 (HITP) 2 The powder was dried at 80°C for 30 min and then irradiated with ultraviolet light for 30 min to increase the surface activity; S2, sample loading: the pretreated MOF-Ni 3 (HITP) 2 The powder is evenly spread in an open container and placed in a chemical vapor deposition furnace, where it is evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, the gas flow rate is 800 mL / min, the gas contains carrier gas and carbon source gaseous precursor, the volume ratio of carrier gas to carbon source gaseous precursor is 100:6.5; the carrier gas is argon gas, and the carbon source gaseous precursor is acetylene; S4, deposition of carbon black: the chemical vapor deposition furnace was heated to 800°C at a heating rate of 5°C / min, the gas flow rate was 1200 mL / min, and the deposition reaction was carried out for 2 h to make the conductive carbon black on the MOF-Ni 3 (HITP) 2 The MOF-Ni 3 (HITP) 2 Loading carbon black; S5, surface modification: S5.1: Mix and prepare water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether in a mass ratio of 100:2.0:1.0:1.2:0.5 at 50° C. to obtain a spray; S5.2: Fluidized spray method is used to spray the MOF-Ni 3 (HITP) 2 The carbon black is loaded for surface coating modification, and dried at 80°C to obtain a carbon black-based composite conductive agent for automotive lithium batteries; The parameters of fluidized spraying are: spray inlet temperature 35°C, spray speed 0.35L / min, atomization pressure 0.6MPa, and discharge temperature 50°C.

[0028] The MOF-Ni used in the above embodiments 3(HITP) 2 The particle length of the powder ranges from 400nm to 1μm, the diameter ranges from 19 to 26nm, the pore size is above 2nm, and the specific surface area is below 410m² / g. Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0029] Comparative Example 1 S1, MOF-Ni 3 (HITP) 2 The powder was not dried or irradiated with ultraviolet light; other methods and parameters were the same as in Example 1.

[0030] Comparative Example 2 In S4, the gas flow rate is 300 mL / min; other methods and parameters are the same as in Example 1.

[0031] Comparative Example 3 In S4, the gas flow rate is 2000 mL / min; other methods and parameters are the same as in Example 1.

[0032] Comparative Example 4 In S4, the temperature is raised to 500° C. to deposit carbon black; other methods and parameters are the same as in Example 1.

[0033] Comparative Example 5 S5 was omitted and no surface modification was performed; MOF-Ni was directly used. 3 (HITP) 2 Carbon black is loaded as a conductive agent; other methods and parameters are the same as in Example 1.

[0034] Comparative Example 6 In S5.1, no behenamidopropyl dimethylamine is added to the spray, and the content of behenamidopropyl dimethylamine is replaced by water; other methods and parameters are the same as in Example 1.

[0035] Comparative Example 7 In S5.1, fatty alcohol polyoxyethylene ether is not added to the spray, and the content of fatty alcohol polyoxyethylene ether is replaced by water; other methods and parameters are the same as in Example 1.

[0036] Comparative Example 8 In S5.1, the spray does not contain behenamidopropyl dimethylamine and fatty alcohol polyoxyethylene ether, and the contents of behenamidopropyl dimethylamine and fatty alcohol polyoxyethylene ether are replaced by water; other methods and parameters are the same as in Example 1.

[0037] Comparative Example 9 Commercially available conventional conductive carbon black is used as the conductive agent. The particle size of conventional conductive carbon black is below 200 nm.

[0038] The conductive agents of the above-mentioned embodiments and comparative examples were tested in a trial manner.

[0039] Positive electrode slurry formula: lithium iron phosphate 92wt%, conductive agent 3wt%, polyvinylidene fluoride (PVDF) 5wt%; solvent is N-methylpyrrolidone (NMP), slurry system solid content 58%. Positive electrode sheet (coated on aluminum sheet) compaction density 2.0g / cm 3 .

[0040] Negative electrode slurry formula: artificial graphite 92.4wt%, commercial Super P 3wt%, SBR 3%, CMC 1.6wt%; solvent is deionized water, slurry system solid content 60%. Negative electrode sheet (coated on copper sheet) compaction density 1.6g / cm 3 .

[0041] Diaphragm: Polypropylene porous membrane.

[0042] Electrolyte: EC:DMC:EMC=1:1:1 (volume ratio), LiPF 6 The concentration is 1mol / L.

[0043] The conductive agent of the positive electrode corresponds to the conductive agent of each embodiment and each comparative example.

[0044] Battery: 18650 battery samples were prepared according to the 18650 battery preparation method, and the amount of electrolyte added was 0.6g. Three parallel samples were made for each test. The performance test results are shown in Table 1 below.

[0045] Table 1 Electrical performance test results (average value) From the above results, it can be seen that the batteries of Examples 1 to 5 have low internal resistance, stable charge and discharge, high first discharge efficiency and 500-cycle efficiency, indicating that the conductive agent can play a good conductivity and has stable conductivity in long-term use. 3 (HITP) 2 The powder is not dried or irradiated with ultraviolet light, so its surface activity is low, and its deposition bonding with conductive carbon black is poor. It is easily affected by pulping and use, and its conductivity and stability are relatively reduced. From the results of Comparative Examples 2 and 3, it can be seen that too large a flow rate of the deposition gas will affect the deposition stability of the conductive carbon black, and too small a flow rate will affect the deposition amount of the conductive carbon black, which will in turn affect the decrease in conductivity and the low charging and discharging efficiency of the battery. From the results of Comparative Example 4, it can be seen that when deposited at 500°C, the temperature is relatively low, the carbon layer structure of carbon black is unstable, and the carbon layer is in a relatively disordered stage, which affects ion transport and has relatively poor conductivity. From the results of Comparative Example 5, it can be seen that MOF-Ni 3 (HITP) 2The loaded carbon black is not surface modified, which affects the dispersibility of the conductive agent, and the conductive performance is unstable. The loaded carbon black layer is easily affected by the mixing and battery charging and discharging, resulting in structural changes, and the carbon black layer falling off. The stability of the charge and discharge efficiency is seriously affected, and the charge and discharge efficiency is greatly reduced after long-term use. From the results of Comparative Examples 6 to 8, it can be seen that behenamide propyl dimethylamine and fatty alcohol polyoxyethylene ether can provide stability for the surface coating, the surface coating is more uniform, the coating modification quality is improved, the conductive agent structure is not easy to dissociate, and the use stability of the conductive agent is improved. Long-term use can ensure a higher charge and discharge efficiency. From the results of Comparative Example 9, it can be seen that the conductivity and conductive stability of the conductive agent used alone as the positive electrode conductive agent are far inferior to those of the conductive agent in the embodiment, indicating that the conductive agent in the embodiment has a good conductive effect.

Claims

1. A method for preparing a carbon black-based composite conductive agent for automotive lithium batteries, characterized in that: The preparation method comprises the following steps: S1, sample pretreatment: drying the MOF-Ni3(HITP)2 powder and then irradiating it with ultraviolet light to increase the surface activity; S2, sample loading: the pretreated MOF-Ni3(HITP)2 powder is evenly spread in an open container, placed in a chemical vapor deposition furnace, and evacuated to remove air and impurities; S3, introducing gas: introducing gas into the chemical vapor deposition furnace, wherein the gas contains a carrier gas and a carbon source gaseous precursor, and the volume ratio of the carrier gas to the carbon source gaseous precursor is 100:(3-10); S4, depositing carbon black: heating the chemical vapor deposition furnace to 600°C to 800°C, with a gas flow rate of 800mL / min to 1500mL / min, and performing a deposition reaction for 1.5h to 3h to deposit the conductive carbon black on the surface and in the pores of MOF-Ni3(HITP)2, cooling and taking out, and obtaining MOF-Ni3(HITP)2 loaded carbon black; S5, surface modification: S5.1: Mix and prepare the following according to the mass ratio: water: polyvinyl alcohol: water-based polyurethane: behenamidopropyl dimethylamine: fatty alcohol polyoxyethylene ether = (80-100): (1-2.5): (0.5-1.5): (0.5-1.5): (0.3-0.8) to obtain a spray; S5.2: The surface of MOF-Ni3(HITP)2 loaded with carbon black is modified by a fluidized spraying method, and then dried to obtain a carbon black-based composite conductive agent for automotive lithium batteries.

2. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S1, the drying is vacuum drying, the drying temperature is 60° C. to 80° C., and the drying time is more than 20 minutes.

3. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S1, the ultraviolet irradiation time is 30 minutes to 50 minutes.

4. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S3, the carrier gas is nitrogen or argon, and the carbon source gaseous precursor is acetylene.

5. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S3, the flow rate of the gas is 500 mL / min to 1500 mL / min.

6. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S4, the heating rate is 5°C / min to 8°C / min.

7. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S5.1, the mixing temperature is 40°C to 60°C.

8. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S5.2, the parameters of the fluidized spray are: spray inlet temperature 30°C to 35°C, spray speed 0.25L / min to 0.35L / min, atomization pressure 0.5MPa to 0.6MPa, and discharge temperature 50°C to 60°C.

9. The method for preparing a carbon black-based composite conductive agent for automotive lithium batteries according to claim 1, characterized in that: In S5.2, the drying temperature is 70°C to 80°C.

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