Dispersing agent, carbon material dispersion liquid, preparation method of carbon material dispersion liquid, battery pole piece and battery

Abstract

The embodiment of the invention provides a dispersing agent, a carbon material dispersion liquid, a preparation method of the carbon material dispersion liquid, a battery pole piece and a battery, the dispersing agent comprises a compound shown in a formula (I) and a derivative of the compound, in the formula (I), R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted alkynyl, R2 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted alkynyl, and R3 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted alkynyl. R2 and R3 are independently selected from substituted or unsubstituted alkylene, substituted or unsubstituted alkenylene or substituted or unsubstituted alkynylene, and X1 and X2 are independently selected from halogen atoms. The dispersing agent has a stable molecular structure and is applied to the field of batteries, so that a carbon material can be efficiently and enduringly dispersed in electrode slurry, a battery pole piece prepared from the electrode slurry has lower volume resistivity, the direct-current resistance of a battery device in a normal-temperature environment or a low-temperature environment can be remarkably reduced, and the service life of the battery device is prolonged. Therefore, the starting performance and the discharging capability of the battery are enhanced.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application belongs to the technical field of batteries, and particularly relates to a dispersant, a carbon material dispersion liquid and a preparation method thereof, a battery pole piece and a battery. BACKGROUND

[0002] Lithium iron phosphate batteries have been widely used in the automotive field due to their low cost, high safety, long cycle life and fast charging capability. However, there are technical bottlenecks in the low-temperature starting performance and discharge capacity of the batteries, and carbon nanotubes (CNTs) with excellent electrical and thermal conductivity and mechanical properties are considered as a key material to break through the bottleneck. However, due to the large specific surface area and strong van der Waals force of carbon nanotubes, they are prone to agglomeration or entanglement, and it is difficult to achieve uniform dispersion in solvents or slurries, which is not conducive to maximizing the functional role of carbon nanotubes. For the dispersion problem of CNTs, the current mainstream dispersion technology often has to make a choice, which is difficult to fundamentally solve the intrinsic agglomeration problem of CNTs, and at the same time, it is difficult to avoid affecting the electron transfer by damaging the integrity of CNTs or over-modifying or coating CNTs. SUMMARY

[0003] In view of this, the embodiment of the present application provides a dispersant, a carbon material dispersion liquid and a preparation method thereof, a battery pole piece and a battery. The dispersant can make the carbon material efficiently dispersed in the solvent or the electrode slurry, and has better stability. The battery pole piece formed by the electrode slurry has a lower volume resistivity, thereby reducing the direct current resistance (DCR, Direct Curent Resistance) of the battery device in a normal temperature or low temperature environment. When applied in the field of new energy vehicles, the starting performance and discharge capacity of the vehicle in a low temperature environment can be effectively optimized.

[0004] In a first aspect, the embodiment of the present application provides a dispersant, which comprises a compound represented by formula (I) and derivatives thereof:

[0005] Formula (I) wherein R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, or substituted or unsubstituted alkynyl; R2 and R3 are independently selected from substituted or unsubstituted alkylene, substituted or unsubstituted alkenylene, or substituted or unsubstituted alkynylene; X1 and X2 are independently selected from halogen atoms.

[0006] In the present application, the number of carbon atoms a of R1 is 4-25, and / or; the number of carbon atoms b of R2 is 4-25, and / or; the number of carbon atoms c of R3 is 4-25; and / or, R2 and R3 are the same.

[0007] In the embodiments of the present application, R2 and R3 are the same, and a and b satisfy: b-2≤a≤b+2.

[0008] In a second aspect, the embodiments of the present application provide a carbon material dispersion liquid, which comprises a carbon material, a dispersant and a solvent, the dispersant has a structure shown in formula (I):

[0009] Formula (I) In formula (I), R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, or substituted or unsubstituted alkynyl; R2 and R3 are independently selected from substituted or unsubstituted alkylene, substituted or unsubstituted alkenylene, or substituted or unsubstituted alkynylene; X1 and X2 are independently selected from halogen atoms.

[0010] In the embodiments of the present application, in the carbon material dispersion liquid, the mass ratio of the carbon material to the dispersant is 1:(0.05-20); and / or, the mass content of the carbon material in the carbon material dispersion liquid is 1%-10%.

[0011] In the embodiments of the present application, the particle size D 50 of the carbon material is less than or equal to 200 μm; and / or, the fineness of the carbon material is less than or equal to 200 μm; and / or, the viscosity of the carbon material dispersion liquid is 800 mPa·s-10000 mPa·s.

[0012] In the embodiments of the present application, the carbon material comprises carbon nanotubes, the length of the carbon nanotubes is 30 nm-60 nm, and the diameter of the carbon nanotubes is 5 nm-10 nm.

[0013] In a third aspect, the embodiments of the present application provide a preparation method of the carbon material dispersion liquid provided in the second aspect, comprising mixing a carbon material, a dispersant and a solvent to obtain a carbon material dispersion liquid.

[0014] In a fourth aspect, the embodiments of the present application provide a battery pole piece, which comprises a carbon material and the dispersant provided in the first aspect.

[0015] In a fifth aspect, the embodiments of the present application further provide a battery, which comprises the battery pole piece provided in the fourth aspect. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0017] As new energy vehicles penetrate the cold-region market, the low-temperature performance bottleneck of lithium iron phosphate batteries is becoming increasingly apparent. For example, in environments below -10°C, the cold start power drops sharply, making it difficult to meet the instantaneous high power demand when starting a vehicle at low temperatures. At the same time, the sharp reduction in low-temperature discharge capacity also leads to a significant decrease in the vehicle's driving range. The key to overcoming this low-temperature power bottleneck lies in optimizing the low-temperature conduction efficiency of the battery's internal conductive network.

[0018] In response, carbon nanotubes (CNTs), with their extremely high axial conductivity, excellent mechanical strength, and good thermal conductivity, are considered core functional materials for addressing the low-temperature performance limitations of lithium iron phosphate batteries. However, due to their significantly larger specific surface area and strong van der Waals forces compared to traditional conductive agents, CNTs are prone to spontaneous aggregation during the electrode slurry preparation process, making it difficult to uniformly disperse them in the solvent or active material system. This aggregation not only disrupts the continuity of the conductive network but may also lead to localized current concentration, exacerbating electrode polarization and ultimately reducing the electrochemical performance and safety of the battery.

[0019] Therefore, solving the dispersion problem of CNTs is the core challenge in their practical applications. Current mainstream dispersion technologies can be broadly categorized into three types, each with significant limitations: First, physical stirring and shearing techniques, including ball milling, ultrasonic dispersion, centrifugal stirring, and high-speed shearing. While these techniques can temporarily deagglomerate aggregates, secondary entanglement still occurs after long-term storage, failing to fundamentally solve the intrinsic aggregation problem of CNTs and potentially shortening the tube length of CNTs. Second, covalent functionalization techniques, including introducing hydrophilic groups such as hydroxyl (-OH) or carboxyl (-COOH) groups onto the surface of CNTs using oxidants to improve their dispersibility in aqueous systems. However, this process disrupts the structural integrity of CNTs, increases surface defects, and consequently reduces conductivity. Third, non-covalent functionalization techniques, including using modifiers such as PVP and HNBR to achieve dispersion through physical adsorption and steric hindrance. While this method maintains the structural integrity of CNTs, the thick coating layer formed by the macromolecular modifier hinders electron transport. In summary, existing CNT dispersion technologies cannot simultaneously meet the three core requirements of uniform and stable dispersion, intact CNT structure, and retention of conductivity. Seeking new dispersion technologies or high-performance dispersants is a technological direction that urgently needs to be broken through in the current lithium iron phosphate battery field.

[0020] In view of this, embodiments of this application provide a dispersant comprising the compound represented by formula (I) and its derivatives:

[0021] Equation (I) Wherein, R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl; R2 and R3 are independently selected from substituted or unsubstituted alkylene, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl; X1 and X2 are independently selected from halogen atoms.

[0022] The dispersant provided in this application includes a m-aniline salt structure containing a carbon chain, which can construct a "bundle-adsorption-dispersion" dispersion mechanism. First, the carbon chain group R1 in its structure can exert a "tip crowbar effect" to make the dispersant more easily enter the substance to be dispersed, improving its unbundle efficiency. The hydrophobic carbon chain combines with the hydrophobic interface on the surface of the substance to be dispersed, allowing the dispersant to be adsorbed on the surface of the substance to be dispersed. Especially for carbon materials, the conjugated structure of the central benzene ring of the dispersant can also undergo π-π stacking with the electron cloud of the graphite lattice of the carbon material, further increasing the adsorption strength. Finally, after the dispersant is adsorbed on the surface of the substance to be dispersed, the hydrophilic haloamine group in the m-aniline salt structure faces the water or solvent, providing electrostatic repulsion and steric hindrance, enabling the substance to be effectively dispersed. The steric hindrance formed by R2 and R3 can further enhance its dispersibility in the system.

[0023] In this embodiment, R1 has a carbon atom number, R2 has a carbon atom number b carbon atom number, and R3 has a carbon atom number c carbon atom number. a and b are independently selected from 4 to 25, for example, but not limited to 4, 5, 8, 9, 10, 11, 12, 13, 20, 21, 22, and 25. This provides sufficient steric hindrance to the carbon chain to fully utilize its dispersibility, while avoiding excessively large substituents that could cause large steric hindrance and affect the original physicochemical properties of the substance to be dispersed. Specifically, a is the sum of the number of carbon atoms in R1, b is the sum of the number of carbon atoms in R2, and c is the sum of the number of carbon atoms in R3.

[0024] In some embodiments of this application, R1 is a substituted or unsubstituted alkyl group, where the alkyl group serves as the main carbon chain of R1. The main carbon chain of R1 is a straight-chain alkyl group with 4-20 carbon atoms, and its carbon number can be, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. The saturated structure of the alkyl group has stronger chemical stability. In some specific embodiments of this application, the main carbon chain in R1 is a straight-chain alkyl group with 8-12 carbon atoms. In other specific embodiments of this application, R1 is a straight-chain alkyl group with 8-12 carbon atoms, such as n-octyl, n-nonyl, n-decyl, n-undecyl, or n-dodecyl.

[0025] In some embodiments of this application, R1 is a substituted or unsubstituted alkenyl group, in which case the alkenyl group serves as the main carbon chain of R1. The main carbon chain of R1 is a straight-chain alkenyl group with 4-20 carbon atoms, and its carbon atom number can be, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 1, 18, 19, or 20. The main carbon chain may contain one or more carbon-carbon double bonds. In some specific embodiments of this application, the main carbon chain of R1 is a straight-chain alkenyl group with 8-12 carbon atoms. In other specific embodiments of this application, R1 is a straight-chain alkenyl group with 8-12 carbon atoms. The straight-chain alkenyl group with 8-12 carbon atoms can be, but is not limited to, 1-n-octenyl, 2-n-octenyl, 1-n-nonenyl, 2-n-nonenyl, 1,3-n-nonadienyl, 1-n-decenyl, 2-n-decenyl, 1,3-n-decadienyl, 1-n-undecenyl, 3-n-undecenyl, 3-n-dodecenyl, and 4-n-dodecenyl.

[0026] In some embodiments of this application, R1 is a substituted or unsubstituted alkynyl group, which serves as the main carbon chain of R1. The number of carbon atoms in R1 can be, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 1, 18, 19, or 20. The main carbon chain may contain one or more carbon-carbon triple bonds. In some specific embodiments of this application, the main carbon chain of R1 is a straight-chain alkynyl group with 8-12 carbon atoms. In other specific embodiments of this application, R1 is a straight-chain alkynyl group with 8-12 carbon atoms. The straight-chain alkynyl group with 8-12 carbon atoms can be, but is not limited to, 1-n-octyryl, 2-n-octyryl, 1,3-n-octadiyryl, 1-n-nonyryl, 2-n-nonyryl, 1-n-decynyl, 2-n-decynyl, 1,4-n-decadiyryl, 1-n-undecynyl, 3-n-undecynyl, 3-n-dodecynyl, and 4-n-dodecynyl.

[0027] In some embodiments of this application, the end group of R1 furthest from the benzene ring is an alkyl group. Because alkyl groups have less steric hindrance, the tail of R1, i.e., the "tip", is sharper, which can maximize the tip crowbar effect and enhance the unbundling ability of the dispersed material.

[0028] In some embodiments of this application, R2 and R3 are independently selected from substituted or unsubstituted alkylene groups. In this case, the alkylene group serves as the main carbon chain of R2 or R3. The main carbon chain of R2 or R3 is a straight-chain alkylene group with 4-20 carbon atoms, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms. Saturated alkylene groups exhibit stronger chemical stability. In some specific embodiments of this application, the main carbon chain of R2 or R3 is a straight-chain alkylene group with 8-12 carbon atoms. In other specific embodiments of this application, R2 or R3 is a straight-chain alkylene group with 8-12 carbon atoms, such as n-octylene, n-nonylene, n-decylene, n-undecylene, or n-dodecylene.

[0029] In some embodiments of this application, R2 and R3 are independently selected from substituted or unsubstituted alkenyl groups. An alkenyl group refers to a divalent group containing one or more carbon-carbon double bonds formed by removing one hydrogen atom from each of the two carbon atoms in an olefin molecule. In this case, the alkenyl group serves as the main carbon chain of R2 and R3. The main carbon chain of R2 and R3 is a straight-chain alkenyl group with 4-20 carbon atoms. For example, the number of carbon atoms can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 1, 18, 19, or 20. The main carbon chain of R2 and R3 may contain one or more carbon-carbon double bonds. In some specific embodiments of this application, the main carbon chain of R2 or R3 is a straight-chain alkenyl group with 8-12 carbon atoms. In other specific embodiments of this application, R2 or R3 is a straight-chain alkenyl group with 8-12 carbon atoms. For example, but not limited to, 1-octene-1,8-diyl, 1-nonene-1,9-diyl, 1-decene-1,10-diyl, and 1-undecene-1,11-diyl.

[0030] In some embodiments of this application, R2 and R3 are independently selected from substituted or unsubstituted alkynyl groups. An alkynyl group refers to a divalent group containing one or more carbon-carbon triple bonds formed by removing two hydrogen atoms from each of the two carbon atoms in an alkyne molecule. In this case, the alkynyl group serves as the main carbon chain of R2 and R3. The main carbon chain of R2 and R3 is a straight-chain alkynyl group with 4-20 carbon atoms. For example, the number of carbon atoms can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 1, 18, 19, or 20. The main carbon chain of R2 and R3 may contain one or more carbon-carbon triple bonds. In some specific embodiments of this application, the main carbon chain of R2 or R3 is a straight-chain ynylene group with 8-12 carbon atoms. In other specific embodiments of this application, R2 or R3 is a straight-chain ynylene group with 8-12 carbon atoms. For example, but not limited to, 1-octyne-1,8-diyl, 1-nonyne-1,9-diyl, 1-decyne-1,10-diyl, and 1-undecanyne-1,11-diyl.

[0031] In some embodiments of this application, the substituents in the substituted alkyl, substituted alkenyl, substituted alkynyl, substituted alkylene, substituted alkenylene, or substituted alkynylene are independently selected from one or more of alkoxy, halogen, hydroxyl, carboxyl, amino, mercapto, and aryl. In some embodiments of this application, R1 may be a methyl-substituted n-octyl or a methoxy-substituted n-decyl, R2 may be a halogen-substituted octylene, and R3 may be a hydroxyl-substituted pentylene or a carboxyl-substituted hexylene.

[0032] In some embodiments of this application, derivatives of the compound represented by formula (I) include, but are not limited to, acid addition salts formed by the compound represented by formula (I) and an acid, and base addition salts formed by the compound represented by formula (I) and a base. The anion in the acid addition salt or the cation in the base addition salt may replace R1, R2, and R3 in formula (I). In some embodiments of this application, the dispersant may be one or more of the following: hydrochloride salt of the compound represented by formula (I), phosphate salt of the compound represented by formula (I), sulfonate salt of the compound represented by formula (I), sodium salt of the compound represented by formula (I), potassium salt of the compound represented by formula (I), and ammonium salt of the compound represented by formula (I).

[0033] In some embodiments of this application, R2 and R3 are the same, which allows the dispersant to exhibit a spatially symmetrical structure. When R2 and R3 are the same alkyl group, the symmetrical structure can reduce the twist energy of the alkyl chain and improve the structural stability of the dispersant molecule. When R2 and R3 are the same alkenyl or alkyne, the symmetrical structure can reduce the local stress of double or triple bonds and reduce the probability of side reactions such as spontaneous polymerization and oxidation of the dispersant. In some specific embodiments of this application, R2 and R3 are the same (i.e., b=c), and a and b satisfy: b-2≤a≤b+2. This is beneficial for a more stable symmetrical structure and a more durable and effective dispersing effect. Furthermore, when R1, R2, and R3 are all unsubstituented, R2 and R3 are the same (i.e., b=c), and a=b+1. This is more conducive to balancing the charge density and steric hindrance of the dispersant and also avoids interference from complex substituents on the three functional groups on the benzene ring, thus improving the dispersing effect to a greater extent.

[0034] In some embodiments of this application, X1 and X2 are independently selected from halogen atoms. The formed NHX1 and NHX2 serve as the tails of the substituents R2 and R3 attached to the benzene ring by the halogenated amine group. They are hydrophilic. When the dispersant is adsorbed onto the surface of the substance to be dispersed, these hydrophilic tails can make the dispersant molecules and water molecules tightly bonded through hydrogen bonds or electrostatic interactions, thereby reducing the interfacial tension and making the substance to be dispersed easier to be wetted by the medium, thus achieving dispersion. At the same time, the charged groups at the dissociation sites of the halogenated amine tails in the dispersion medium cause the surface of the substance to be dispersed to be attached with the same charge, thereby forming an electrostatic repulsion force, which further promotes dispersion and prevents aggregation.

[0035] In some embodiments of this application, X1 and X2 are independently selected from fluorine (F), chlorine (Cl), bromine (Br), or iodine (I), and X1 and X2 may be the same or different. This is based on the difference in electronegativity of halogen atoms (F... - >Cl - >Br - >I - ) and ionic radius difference (F - <Cl - <Br - <I - In other words, the higher the electronegativity, the greater the charge density and the stronger the hydrophilicity. The halogenated amine tails formed by different halogen atoms have different charge densities and hydrophilic strengths. This difference provides adjustability to the dispersing ability of the dispersant for the substance to be dispersed in different media (e.g., water or organic solvents). In some specific embodiments of this application, X1 and X2 are independently selected from F or Cl.

[0036] In some specific embodiments of this application, the dispersant may be, for example, but is not limited to, the structure shown in formulas (I-1) to (I-10): Equation (Ⅰ-1) Equation (Ⅰ-2), Equation (Ⅰ-3) Equation (Ⅰ-4) Equation (Ⅰ-5) Equation (Ⅰ-6) Equation (Ⅰ-7) Equation (Ⅰ-8) Equation (Ⅰ-9) Equation (Ⅰ-10).

[0037] The dispersant provided in this application embodiment has a meta-substituted aniline salt structure. Firstly, the electronic and steric effects of the three meta-substituents (-R1, -R2-NHX1, -R3-NHX2) work together to maintain the stability of the benzene ring conjugated system. Specifically, the electron-withdrawing properties of -R2-NHX1 and -R3-NHX2 reduce the electron cloud density of the benzene ring, thereby reducing the probability of attack by electrophilic reagents and stabilizing the benzene ring structure. The long carbon chain hydrocarbon group of R1 can hinder the non-specific interaction between the benzene ring and other molecules, further protecting the benzene ring conjugated system. This makes the dispersant molecule have excellent structural stability in different systems, thereby ensuring a long-lasting and effective dispersion effect.

[0038] Secondly, the steric hindrance and charge repulsion of the three meta-substituents serve as the core of the dispersant's function. The long-chain structure forms a molecular barrier in the dispersion medium. When the substances to be dispersed approach each other, the chain segments squeeze each other to generate entropy reduction repulsion force to prevent them from directly contacting each other. On this basis, the three substituents and the benzene ring structure jointly construct a "bundle-adsorption-dispersion" dispersion mechanism. Furthermore, the length and symmetry of the substituents are specially designed to maximize the dispersing effect of the dispersant on the substances to be dispersed.

[0039] In summary, the dispersant provided in this application has good stability, which can not only completely preserve the original structure and physicochemical properties of the substance to be dispersed, but also play a strong and long-lasting dispersing role. The substance to be dispersed can be a carbon material or other substances other than carbon materials. This application provides a carbon material dispersion, which includes carbon material, a dispersant, and a solvent. The dispersant is any of the dispersants described in the above embodiments.

[0040] In some embodiments of this application, the mass content of carbon material in the carbon material dispersion is 1%-10%, for example, but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%. An appropriate content of carbon material can ensure basic conductivity while avoiding excessive concentration that could trigger large-scale aggregation.

[0041] In some embodiments of this application, the mass ratio of carbon material to dispersant in the carbon material dispersion is 1:(0.05-20), for example, but not limited to, 1:0.05, 1:0.1, 1:0.2, 1:0.5, 1:1, 1:2, 1:5, 1:8, 1:10, 1:12, 1:15, and 1:20. In some embodiments of this application, the mass ratio of carbon material to dispersant is 1:(0.1-10), which ensures that the contents of the two are matched to promote the full adsorption of the dispersant and carbon material, thereby achieving better dispersion. In some specific embodiments of this application, the mass ratio of carbon material to dispersant is 1:(0.1-1).

[0042] In some specific embodiments of this application, the mass content of carbon material in the carbon material dispersion is 1%-8%, and the mass ratio of carbon material to dispersant is (5-10):1. By controlling the mass content of carbon material and its mass ratio to dispersant within the above range, a better balance can be achieved in terms of conductivity and dispersion.

[0043] In this application, the carbon material can be selected from carbon materials known in the art, such as, but not limited to, carbon nanotubes, carbon black, graphite, activated carbon, carbon fibers, carbon nanofibers, fullerenes, porous carbon, etc. In some embodiments of this application, the carbon nanotubes can be one or more of oligowalled carbon nanotubes, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0044] In this application, the solvent can be selected from conventional solvents in the art, such as water or organic solvents. Organic solvents can be N-methylpyrrolidone (NMP), ethanol, acetone, diethyl ether, chloroform, dichloromethane, dimethyl sulfoxide, etc.

[0045] In some embodiments of this application, under conditions of 25℃±5℃, the viscosity of the carbon material dispersion is 800 mPa·s-10000 mPa·s, for example, but not limited to, 800 mPa·s, 1000 mPa·s, 1400 mPa·s, 2000 mPa·s, 3000 Pa·s, 4000 mPa·s, 5000 mPa·s, 7000 mPa·s, 9000 mPa·s, and 10000 mPa·s. In some embodiments of this application, the viscosity of the carbon material dispersion is 800 mPa·s-8000 mPa·s. In some embodiments of this application, the viscosity of the carbon material dispersion is 800 mPa·s-7000 mPa·s. In some embodiments of this application, the viscosity of the carbon material dispersion is 800 mPa·s-4000 mPa·s. In some embodiments of this application, the viscosity of the carbon material dispersion is 800 mPa·s-3000 mPa·s. In other embodiments, the viscosity of the carbon material dispersion is 800 mPa·s-1000 mPa·s. A lower viscosity in the carbon material dispersion is more conducive to the free diffusion of carbon materials in the medium, avoiding localized deviations in carbon content, and also reducing the settling rate of carbon materials under long-term static conditions, thus optimizing dispersion stability and service life. The viscosity can be measured using a rotational viscometer in this application.

[0046] In some embodiments of this application, under conditions of 25℃±5℃, the particle size D of the carbon material in the carbon material dispersion is... 50 The particle size is less than or equal to 200 μm, and can be, but is not limited to, 5 μm, 6 μm, 9 μm, 10 μm, 14 μm, 15 μm, 20 μm, 40 μm, 50 μm, 80 μm, 88 μm, 100 μm, and 200 μm. In some embodiments of this application, the particle size D of the carbon material in the carbon material dispersion is... 50 Less than or equal to 100 μm. In some embodiments of this application, the particle size D of the carbon material in the carbon material dispersion is... 50 Less than or equal to 50 μm. In some embodiments of this application, the particle size D of the carbon material in the carbon material dispersion is... 50 Less than or equal to 40 μm. In some embodiments of this application, the particle size D of the carbon material in the carbon material dispersion is... 50 Less than or equal to 20 μm. Particle size refers to the geometric size of a single carbon material particle or particle agglomeration, and its core description is the size distribution of the particle group. This application uses the median particle size D. 50This reflects the particle size of the carbon material in the dispersion, specifically, the cumulative particle size distribution where 50% of the particles are smaller than this value. Smaller carbon particles are more conducive to forming a dense conductive and thermally conductive network within the system, reducing resistance, shortening ion transport paths, and more easily filling electrode pores when applied to electrodes, thus reducing the contact resistance between the electrolyte and the electrode. This application utilizes a laser particle size analyzer to detect particle size.

[0047] In some embodiments of this application, under conditions of 25℃±5℃, the fineness of the carbon material in the carbon material dispersion is less than or equal to 200 μm, for example, but not limited to, 10 μm, 20 μm, 24 μm, 25 μm, 26 μm, 30 μm, 33 μm, 35 μm, 39 μm, 40 μm, 50 μm, 60 μm, 100 μm, 150 μm, and 200 μm. In some embodiments of this application, the fineness of the carbon material in the carbon material dispersion is less than or equal to 100 μm. In some embodiments of this application, the fineness of the carbon material in the carbon material dispersion is less than or equal to 60 μm. In some embodiments of this application, the fineness of the carbon material in the carbon material dispersion is less than or equal to 40 μm. In some embodiments of this application, the fineness of the carbon material in the carbon material dispersion is less than or equal to 30 μm. Fineness is a physical quantity characterizing the size of solid dispersed phase particles or agglomerates in a dispersion system. The core focus is on the maximum apparent particle size. In this application, the carbon material in the dispersion exhibits both a small particle size (D50) and a relatively small fineness, indicating that the size distribution of all carbon materials in the system is concentrated, generally small and uniform, avoiding problems such as agglomeration and uneven conductivity caused by large tailing particles. The fineness of this application can be detected using a scraper fineness meter.

[0048] The carbon material dispersion provided in this application contains the aforementioned dispersant. By further precisely controlling the content of carbon material and its ratio with the dispersant, the carbon material dispersion has suitable physical properties, such as conductivity and viscosity, and the dispersion degree of carbon material in the system is improved to a greater extent.

[0049] This application provides a method for preparing the aforementioned carbon material dispersion, which includes mixing carbon material, dispersant and solvent to obtain a carbon material dispersion.

[0050] In some embodiments of this application, the method for preparing the carbon material dispersion includes: S11: The carbon material, dispersant and solvent are mixed in the first mixture to obtain a first solution; S12: Add solvent to the first solution for a second mixing to obtain a carbon material dispersion.

[0051] The method for preparing carbon material dispersion provided in this application embodiment first uses a small amount of solvent for a first mixing, which greatly increases the contact probability between carbon material and dispersant in a high-concentration environment, allowing the dispersant to fully utilize its "unbinding-adsorption" mechanism and quickly adsorb onto the surface of carbon material; then, a second mixing is carried out by adding solvent to achieve uniform dilution, thereby obtaining a carbon material dispersion with suitable concentration and viscosity. The carbon material dispersion prepared in this way has better uniformity and long-term stability.

[0052] In step S11, the first mixing includes stirring the carbon material, dispersant, and solvent. During this process, the shear force is primarily concentrated on the carbon material, breaking down initial agglomerates and forming smaller units. In some embodiments of this application, the stirring speed is 300 rpm to 500 rpm, for example, but not limited to, 300 rpm, 350 rpm, 400 rpm, 460 rpm, 480 rpm, and 500 rpm; the stirring time is 30 min to 180 min, for example, but not limited to, 30 min, 60 min, 100 min, 120 min, 150 min, and 180 min.

[0053] In some embodiments of this application, the first mixing is carried out at a mass ratio of carbon material to dispersant of 1:(0.05-20), and the mass content of carbon material in the first solution is 20%-50%, for example, but not limited to 20%, 30%, 30%, 35%, 38%, 40%, 42%, 45%, 47%, and 50%. The first mixing forms a high-carbon-content system with small interparticle spacing, which is beneficial for achieving concentrated dispersion. A dispersant adsorption layer is formed on the surface of the carbon material, so that the introduction of solvent in subsequent dilution does not destroy the original dispersion structure, but only further widens the interparticle spacing, thereby improving the dispersion efficiency.

[0054] In some embodiments of this application, the size of the carbon material is 10nm-1000nm, for example, but not limited to 10nm, 30nm, 60nm, 10nm, 200nm, 500nm, 800nm, and 1000nm. Here, the size of the carbon material is defined as the maximum distance between any two points on the carbon material raw material before dispersion. In some specific embodiments of this application, the size of the carbon material is 20nm-200nm.

[0055] In some embodiments of this application, the carbon material can be array-grown carbon nanotubes, that is, carbon nanotubes grown in a directional, ordered, and high-density regular morphology on a specific substrate. In some specific embodiments of this application, the length of the carbon nanotubes is 30nm-60nm, for example, but not limited to 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, and 60nm; the diameter of the carbon nanotubes is 5nm-10nm, for example, but not limited to 5nm, 6nm, 7nm, 8nm, 9nm, and 10nm. The surface energy at the endpoints of carbon nanotubes of this size will not be excessively higher than that of the tube wall, avoiding the dispersant preferentially adsorbing at the endpoints and resulting in insufficient adsorption at the tube wall. This is more conducive to the long carbon chains in the dispersant penetrating or drilling into the aggregates to exert a dispersing effect.

[0056] In step S12, the second mixing includes sonicating and / or stirring the first solution and solvent. This process allows the added solvent to diffuse rapidly, avoids local concentration gradients, prevents the dispersion units from agglomerating due to sudden environmental changes, and the provided shear force can further disperse the tiny carbon agglomerates remaining in the first solution.

[0057] In some embodiments of this application, the frequency of ultrasound is 20kHz-40kHz, for example, but not limited to 20kHz, 25kHz, 30kHz, 35kHz, and 40kHz; the duration of ultrasound is 10min-15min, for example, but not limited to 10min, 13min, and 15min; the rotation speed of the second stirring is 500rpm-800rpm, for example, but not limited to 500rpm, 60rpm, 700rpm, and 800rpm; and the duration of the second stirring is 30min-60min, for example, but not limited to 30min, 40min, 50min, and 60min. In some specific embodiments of this application, the second mixing includes performing ultrasound first and then performing the second stirring.

[0058] In some embodiments of this application, the solvent added to the second mixture may be added all at once or in multiple portions.

[0059] In some embodiments of this application, the selection of solvents in steps S11 and S12 is as described above, and the two can be the same or different.

[0060] Both steps S11 and S12 can be performed at temperatures between 15℃ and 40℃, for example, but not limited to 15℃, 20℃, 25℃, 30℃, 35℃, and 40℃.

[0061] This application provides an electrode slurry, comprising an active material, a carbon material dispersion, a binder, and a solvent. The carbon material dispersion and the solvent are as described above, wherein the solvents in the carbon material dispersion and the electrode slurry may be the same or different.

[0062] In this embodiment of the application, the electrode slurry may also include a conductive agent, which can synergistically improve the conductivity and electrochemical performance of the electrode slurry with the carbon material.

[0063] In some embodiments of this application, the preparation of the electrode paste includes the following steps: S21: Premix the adhesive and solvent to obtain an adhesive premix solution; S22: The carbon material dispersion is added to the binder premix for the first dispersion to obtain the slurry base liquid; S23: Add the active material and conductive agent to the slurry base liquid for a second dispersion to obtain the electrode slurry.

[0064] In some embodiments of this application, the active material may be, but is not limited to, a positive electrode active material (such as lithium iron phosphate) or a negative electrode active material; the conductive agent may be, but is not limited to, super carbon black (SP); and the binder may be, but is not limited to, polyvinylidene fluoride (PVDF). In some specific embodiments of this application, the mass ratio of lithium iron phosphate, carbon material dispersion, SP, and PVDF in the electrode slurry may be 90:2:5:3.

[0065] In step S21, the mass ratio of adhesive to solvent in the adhesive premix is ​​1:(10-50); the premixing temperature can be room temperature, such as but not limited to 15℃, 20℃, 25℃, 30℃, 35℃, 40℃; the premixing time is 4h-10h, such as but not limited to 4h, 5h, 6h, 7h, 8h, 9h, 10h.

[0066] In step S22, the stirring speed of the first dispersion is 2000rpm-3000rpm, for example, but not limited to 2000rpm, 2300rpm, 2500rpm, 2800rpm, or 3000rpm; the stirring time of the first dispersion is 30min-180min, for example, but not limited to 30min.

[0067] In step S23, the second dispersion includes sequential low-speed stirring and high-speed stirring. The low-speed stirring speed is 500 rpm-800 rpm, for example, but not limited to 500 rpm, 550 rpm, 600 rpm, 650 rpm, and 700 rpm, and the low-speed stirring time is 60 min-240 min, for example, but not limited to 60 min, 100 min, 150 min, 200 min, and 240 min. The high-speed stirring speed is 1500 rpm-3000 rpm, for example, but not limited to 1500 rpm, 1700 rpm, 2000 rpm, 2300 rpm, 2500 rpm, and 3000 rpm, and the high-speed stirring time is 90 min-120 min, for example, but not limited to 90 min, 100 min, 110 min, and 120 min.

[0068] In some embodiments of this application, the electrode slurry is further screened using a 100-200 mesh sieve after the second dispersion to remove large particles.

[0069] This application also provides a battery electrode, comprising a carbon material and the dispersant described in any of the above embodiments.

[0070] This application also provides a method for preparing a battery electrode sheet, which is formed by coating and drying the electrode slurry in any of the above embodiments.

[0071] In some embodiments of this application, the battery electrode sheet may be prepared by coating an electrode slurry on the surface of a current collector, drying, and rolling to form the battery electrode sheet. In other embodiments of this application, the battery electrode sheet may be prepared by coating an electrode slurry on a substrate surface, drying, rolling, and peeling it off from the substrate to form the battery electrode sheet.

[0072] In some embodiments of this application, the coating method may be transfer coating; the coating speed is 10m / min-20m / min, the coating temperature is 80℃-120℃; the rolling speed is 5m / min-10m / min, and the linear pressure is 80kM / m-200kM / m.

[0073] This application also provides a battery, which includes the battery electrode sheets in any of the above embodiments.

[0074] In some embodiments of this application, the battery may be, for example, but is not limited to, a lithium-ion battery, and the battery electrode may be a positive electrode or a negative electrode.

[0075] In some embodiments of this application, the battery preparation includes: 1) coating electrode slurry; 2) rolling; 3) slitting and die-cutting according to the cell size to obtain battery electrode sheets; 4) assembling the battery electrode sheets into a cell, baking and injecting electrolyte, and performing capacity testing to obtain a battery.

[0076] The battery provided in this application embodiment includes battery electrodes made from the electrode slurry provided above. These electrodes have low DC resistance in both normal and low temperature environments. When applied to new energy vehicles, this battery can meet the instantaneous high power demand of vehicles during low-temperature startup, which helps to improve the starting performance and driving range of the vehicles.

[0077] The effects of the technical solution of this application will be further illustrated below with several specific examples. Unless otherwise specified, the raw materials used in the embodiments of this invention are all commercially available products.

[0078] Example 1 1) Provide a dispersant as shown in formula (Ⅰ-1):

[0079] Equation (Ⅰ-1) 2) Preparation of CNT dispersion: Take carbon nanotubes with a length of 40 nm and a diameter of 8 nm, add carbon nanotubes (CNTs) and dispersant in a mass ratio of 5:1 to NMP solvent, place in a stirrer, and stir at 400 rpm for 120 min to obtain the first solution, wherein the mass content of CNTs is 20%; Continue to add NMP solvent to the first solution to adjust the mass content of CNTs to 8% and the mass content of dispersant to 1.6%. Then, sonicate at 30 kHz for 10 min and stir at 800 rpm for 30 min to obtain CNTs dispersion. 3) Preparation of electrode slurry: At 25℃, PVDF powder was slowly added to NMP solvent at a mass ratio of PVDF:NMP = 1:10, and stirred for 4 hours until completely dissolved to obtain PVDF premixed solution; Then add the CNTs dispersion obtained in step 2) to the PVDF premix and stir at 2000 rpm for 30 min to obtain the slurry base liquid; Finally, lithium iron phosphate and SP were added to the slurry base liquid, stirred at 600 rpm for 60 min, then stirred at 1800 rpm for 90 min, and passed through a 150-mesh sieve to obtain the electrode slurry. The mass ratio of lithium iron phosphate, CNT dispersion, SP and PVDF in the electrode slurry was 90:2:5:3.

[0080] 4) Battery preparation: The electrode slurry obtained in step 3) is coated onto the substrate surface using a transfer coating method at a speed of 15 m / min and a coating temperature of 90°C. It is then placed in a two-roll hot press at a speed of 8 m / min and the linear pressure is controlled at 100 kM / m. The positive electrode sheet is obtained by slitting and die-cutting, and it is then cross-stacked with the graphite negative electrode sheet to assemble the battery cell. The cell is then baked, injected with electrolyte, and subjected to capacity testing to obtain the battery.

[0081] Example 2 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-2):

[0082] Equation (Ⅰ-2) Example 3 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-3):

[0083] Equation (Ⅰ-3) Example 4 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-4):

[0084] Equation (Ⅰ-4) Example 5 The only difference from Example 1 is that the structure of the dispersant is as shown in Formula (Ⅰ-5):

[0085] Equation (Ⅰ-5) Example 6 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-6):

[0086] Equation (Ⅰ-6) Example 7 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-7):

[0087] Equation (Ⅰ-7) Example 8 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (I-8):

[0088] Equation (Ⅰ-8) Example 9 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-9):

[0089] Equation (Ⅰ-9) Example 10 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-10):

[0090] Equation (Ⅰ-10) Example 11 The only difference from Example 1 is that in the CNTs dispersion obtained in step 2), the mass content of CNTs is 2% and the mass content of dispersant is 0.4%.

[0091] Example 12 The only difference from Example 1 is that in the CNTs dispersion obtained in step 2), the mass content of CNTs is 2% and the mass content of dispersant is 20%.

[0092] Example 13 The only difference from Example 1 is that in the CNTs dispersion obtained in step 2), the mass content of CNTs is 2% and the mass content of dispersant is 40%.

[0093] Example 14 The only difference from Example 1 is that in the CNTs dispersion obtained in step 2), the mass content of CNTs is 8% and the mass content of dispersant is 0.8%.

[0094] Example 15 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-11):

[0095] Equation (Ⅰ-11) Example 16 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (Ⅰ-12):

[0096] Equation (Ⅰ-12) Comparative Example 1 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (1):

[0097] Equation (1) Comparative Example 2 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (2):

[0098] Equation (2) Comparative Example 3 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (3):

[0099] Equation (3) Comparative Example 4 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (4):

[0100] Equation (4) Comparative Example 5 The only difference from Example 1 is that the structure of the dispersant is as shown in formula (5):

[0101] Equation (5) Comparative Example 6 The difference from Example 1 is that the CNTs dispersion in step 2) lacks step 1 and does not contain a dispersant.

[0102] Performance testing The CNT dispersions prepared in Examples 1-16 and Comparative Examples 1-6 were subjected to viscosity, fineness, and particle size tests, respectively. Viscosity testing: At 25℃, in accordance with GB / T 2794-2013 "Determination of viscosity of adhesives - Single cylinder rotation viscometer method", an NDJ-8S type viscometer and rotor No. 2 were used for testing, and the average value of 3 parallel experiments was taken.

[0103] Fineness test: Under 25℃ conditions, the fineness of coatings shall be tested using a scraper fineness meter with a range of 0μm-50μm, in accordance with GB / T 1724-1979 "Determination of Fineness of Coatings".

[0104] Particle size determination: Under 25℃ conditions, the particle size distribution (D) was determined using a laser particle size analyzer, referring to GB / T 19077-2016 "Particle Size Analysis - Laser Diffraction Method". 50 value.

[0105] The positive electrode sheets prepared in Examples 1-16 and Comparative Examples 1-6 were used to test the volume resistivity of the positive electrode sheets using the four-probe method, referring to SJ / T 11565-2016 "Test Method for Conductivity of Positive Electrode Materials for Lithium-ion Batteries". Batteries prepared in Examples 1-16 and Comparative Examples 1-6 were used. The DC resistance of the batteries was tested at 25°C and -25°C respectively, according to GB / T 31484-2015 "General Requirements for Lithium-ion Batteries".

[0106] The test results are shown in Table 1: Table 1

[0107] As can be seen from Table 1: Compared to Comparative Examples 1-6, the dispersants in Examples 1-16 resulted in lower viscosity CNT dispersions, with relatively smaller CNT fineness and particle size, reducing the likelihood of CNT aggregation and achieving effective dispersion. Therefore, the cathode sheets prepared in Examples 1-16 exhibited lower volume resistivity, thereby reducing the DC resistance of the battery in both ambient temperature (25°C) and low temperature (-25°C) environments.

[0108] As can be seen from Examples 1-8, 15 and 16, R1, R2 and R3 in the molecular structure of the dispersant of this application can play a strong dispersing role on carbon materials when they have suitable carbon chain lengths, especially the straight-chain hydrocarbon groups with 8-12 carbon atoms have better technical effects.

[0109] As can be seen from Examples 1, 3 and 7, the degree of symmetry of the dispersant molecular structure has a significant impact on the dispersion effect. The higher the symmetry, the more conducive it is to maintaining the stability of the dispersant itself, thereby exerting a long-lasting and effective dispersion effect.

[0110] As can be seen from Examples 1, 9 and 10, in the molecular structure of the dispersant, different halogenated amine groups at the tail of the carbon chain substituents on the benzene ring provide different charge densities and hydrophilicities. Halogen atoms with stronger electronegativity are more conducive to improving the dispersion of carbon materials in solvents.

[0111] As can be seen from Examples 1 and 11-14, under appropriate content combinations, it is more conducive to giving full play to the "unbundling-adsorption-dispersion" mechanism of the dispersant on carbon materials. In the dispersion, especially when the mass of the dispersant is 0.1 times to 10 times the mass of the carbon material, the dispersion effect is better.

[0112] As for Comparative Examples 1-5: The dispersant structures of Comparative Examples 1 and 2 do not contain halogenated amine tails or symmetrical halogenated amine tails, which makes it difficult to provide sufficient hydrophilic strength and steric hindrance to promote dispersion, and is also not conducive to maintaining the long-term stability of the dispersant structure itself; In the dispersant structures of Comparative Examples 3, 4 and 5, the number or distribution of the substituents responsible for dissociation or dispersion is unbalanced, making it difficult to exert the aforementioned dispersion mechanism of this application to achieve a better dispersion effect; while Comparative Example 6 does not contain a dispersant, and its various test data are the worst values.

[0113] In summary, the dispersant provided in this application has a durable and stable molecular structure. By specially designing the positional and quantitative distribution of each functional substituent group at the conjugated center, it synergistically achieves efficient dispersion of carbon materials. When applied to the battery field, it can effectively reduce the DC resistance of the battery at room temperature and low temperature, and has a positive impact on overcoming the low-temperature power bottleneck of battery devices.

[0114] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that implementing all or part of the processes of the above embodiments and making equivalent changes in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A dispersant, characterized in that, The dispersant includes compounds of formula (I) and their derivatives. Equation (I) Wherein, R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, or substituted or unsubstituted alkynyl; R2 and R3 are independently selected from substituted or unsubstituted alkylene groups, substituted or unsubstituted alkenyl groups, or substituted or unsubstituted ynylene groups; X1 and X2 are independently selected from halogen atoms.

2. The dispersant as described in claim 1, characterized in that, The number of carbon atoms a in R1 is 4-25; and / or the number of carbon atoms b in R2 is 4-25; and / or the number of carbon atoms c in R3 is 4-25; and / or R2 is the same as R3.

3. The dispersant as described in claim 2, characterized in that, R2 is the same as R3, and a and b satisfy: b-2≤a≤b+2.

4. A carbon material dispersion, characterized in that, It includes carbon materials, dispersants, and solvents, wherein the dispersants include compounds represented by formula (I) and their derivatives: Equation (I) Wherein, R1 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, or substituted and unsubstituted alkynyl; R2 and R3 are independently selected from substituted or unsubstituted alkylene groups, substituted or unsubstituted alkenyl groups, and substituted or unsubstituted ynylene groups; X1 and X2 are independently selected from halogen atoms.

5. The carbon material dispersion as described in claim 4, characterized in that, The mass ratio of the carbon material to the dispersant is 1:(0.05-20); and / or, the mass content of the carbon material in the carbon material dispersion is 1%-10%.

6. The carbon material dispersion as described in claim 4 or 5, characterized in that, Under conditions of 25℃±5℃, the particle size D of the carbon material 50 The particle size is less than or equal to 200 μm; and / or the fineness of the carbon material is less than or equal to 200 μm; and / or the viscosity of the carbon material dispersion is 800 mPa·s-10000 mPa·s.

7. The carbon material dispersion according to any one of claims 4-6, characterized in that, The carbon material includes carbon nanotubes, which have a length of 30nm-60nm and a diameter of 5nm-10nm.

8. A method for preparing a carbon material dispersion according to any one of claims 4-7, characterized in that, The process includes mixing the carbon material, the dispersant, and the solvent to obtain a dispersion of the carbon material.

9. A battery electrode, characterized in that, Includes carbon materials and the dispersant as described in any one of claims 1-3.

10. A battery, characterized in that, The battery includes the battery electrode as described in claim 9.

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