Dispersing agent and preparation method thereof, electrode material and secondary battery

Abstract

The invention discloses a dispersing agent and a preparation method thereof, an electrode material and a secondary battery, the dispersing agent comprises a first component and a second component, the first component comprises a high-molecular polymer, the weight-average molecular weight of the first component is 8000-60000, the second component comprises an organic compound, the organic compound comprises any one functional group of hydroxyl, carboxyl and amido, and the organic compound comprises any one functional group of hydroxyl, carboxyl and amido. The weight-average molecular weight of the second component is smaller than or equal to that of the first component. The dispersant can improve the conductivity of the lithium ion battery, reduce the internal resistance of the battery, improve the cycle performance of the battery and improve the safety of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of electrode materials, and in particular to a dispersant and a preparation method thereof, an electrode material and a secondary battery. Background Art

[0002] The electrode sheets of lithium-ion batteries are usually composed of electrode active materials (positive electrode materials or negative electrode materials), conductive materials, and binders. When preparing positive electrode sheets, the prepared electrode slurry needs to be coated on the current collector to make electrode sheets. However, the electrode materials are prone to gelation and agglomeration of active materials during the slurrying process, so the state of the slurry is directly related to the quality of the coating. At present, in order to increase the capacity of lithium batteries, the usual solution is to increase the proportion of electrode active materials in the slurry, which will further lead to excessive solid content of the slurry, and the slurry will become more viscous, resulting in poor fluidity, affecting the coating effect of the electrode, and further affecting the efficiency of the lithium battery preparation process.

[0003] Therefore, in order to prevent problems such as slurry gelation, active material agglomeration, excessive slurry viscosity, rapid viscosity increase during storage, and difficulty in increasing slurry solid content during the preparation of electrode slurry, it is urgent to provide a dispersant with excellent dispersibility. Summary of the invention

[0004] The purpose of the present application is to provide a dispersant with excellent dispersibility to improve the viscosity stability, slurry gelation and rheological properties of electrode slurry.

[0005] To achieve the purpose of this application, this application provides the following technical solutions:

[0006] In a first aspect, the present application provides a dispersant, the dispersant comprising a first component and a second component, the first component comprising a high molecular weight polymer, the weight average molecular weight of the first component being 8000 to 60000, the second component comprising an organic compound, the organic compound comprising any one of the functional groups of hydroxyl, carboxyl, and amine, the weight average molecular weight of the second component being less than or equal to the weight average molecular weight of the first component.

[0007] In one embodiment, the high molecular polymer includes one or more of polyvinyl pyrrolidone, a vinyl pyrrolidone copolymer containing a polyether segment, and a nitro-containing polyvinyl pyrrolidone.

[0008] In one embodiment, the organic compound includes one or more of ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups, phenyl acrylate-ethylene oxide copolymer containing hydroxyl groups / amine groups, and nitrile polymers.

[0009] In one embodiment, the ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups is copolymerized by a phenolic hydroxyl group-containing monomer and ethylene-vinyl acetate in a molar ratio of 1: (0.5-1).

[0010] In one embodiment, the phenyl acrylate-ethylene oxide copolymer is copolymerized by phenyl acrylate containing hydroxyl groups and amine groups and ethylene oxide in a molar ratio of 1: (0.5-1).

[0011] In one embodiment, the weight average molecular weight of the first component is 12,000 to 40,000.

[0012] In one embodiment, the weight average molecular weight of the second component is 500-8000.

[0013] In one embodiment, the mass ratio of the first component to the second component is 1:(0.1-1).

[0014] In one embodiment, the dispersant further includes a third component, which includes an organic solvent and one or more of alcohol small molecules, amine small molecules, ester small molecules, and phenol substances containing hydroxyl groups and / or carboxyl groups dissolved in the organic solvent.

[0015] In one embodiment, the alcohol small molecule includes one or more of polyethylene glycol, 2-hydrazinoethanol, 2-mercaptoethanol, ethylene glycol, and propylene glycol.

[0016] In one embodiment, the alcoholamine small molecule includes one or more of succinamide, polyetheramine, polyethyleneimine, isopropanolamine, ethanolamine, diethanolamine, and triethanolamine.

[0017] In one embodiment, the ester small molecule includes one or more of butyl oxalate, ethyl oxalate, dimethyl carbonate, and diethyl carbonate.

[0018] In one embodiment, the phenolic substance containing hydroxyl and / or carboxyl groups includes one or more of salicylic acid, tannic acid, and caffeic acid.

[0019] In one embodiment, the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:(8-20).

[0020] In one embodiment, the viscosity of the dispersant is 30 mPa·s to 200 mPa·s.

[0021] In one embodiment, the water content of the dispersant is less than 3000 ppm.

[0022] In a second aspect, the present application provides a method for preparing a dispersant, which is used to prepare the dispersant as described in the first aspect, and the preparation method comprises the following steps: compounding a first component and a second component to obtain a compound; putting the compound into a reaction kettle, and uniformly mixing them in a protective atmosphere to obtain a dispersant; wherein the first component comprises a polymer, and the weight-average molecular weight of the polymer is 8000 to 60000, and the second component comprises an organic compound, and the organic compound includes any one of the functional groups of hydroxyl, carboxyl, and amine.

[0023] In a third aspect, the present application provides an electrode material, the electrode material comprising an electrode active material and the dispersant as described in the first aspect, wherein the electrode active material is a positive electrode active material or a negative electrode active material.

[0024] In a fourth aspect, the present application provides a secondary battery, wherein the secondary battery includes the electrode material described in the third aspect, or the secondary battery includes the dispersant described in the first aspect.

[0025] By adding the above-mentioned dispersant provided in the present application to the electrode slurry, the solid content of the electrode slurry can be increased and the viscosity can be reduced. In addition, the dispersant can also reduce the alkalinity of the electrode slurry system, thereby improving the anti-gelation characteristics of the electrode slurry, reducing the risk of electrode slurry gel, and thus improving the utilization rate of slurry coating. At the same time, the dispersant can make the prepared battery have the following effects: 1) Improve the conductivity of the lithium ion battery: The dispersant can effectively improve the dispersibility of the lithium salt in the electrolyte, thereby increasing the migration rate of lithium ions in the electrolyte, thereby increasing the conductivity of the battery; 2) Reduce the internal resistance of the battery: The dispersant can reduce the ohmic impedance inside the battery, reduce the polarization phenomenon, thereby reducing the internal resistance of the battery, and improve the rate performance and cycle life of the battery; 3) Improve the cycle performance of the battery: The dispersant can effectively inhibit the shedding of active substances in the battery during the cycle process, reduce the damage to the electrode structure, and thus improve the cycle performance of the battery; 4) Improve the safety of the battery: The dispersant has good thermal stability and chemical stability, which can reduce the safety hazards of the battery under high temperature or overcharge and overdischarge conditions, and improve the safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 is a flow chart of a method for preparing a dispersant in one embodiment;

[0028] Figure 2 is a flow chart of step S20 in one implementation. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0030] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more of the related listed items.

[0031] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0032] The following are explanations of the terms used in this article:

[0033] Solvation: It is the process of interaction between solute molecules and solvent molecules, which leads to the stability of the solute in the solution.

[0034] Weight average molecular weight: The full name is weight average molecular weight (Mass average molar mass), which is the statistical average molecular weight by mass, that is, the molecular weight averaged per unit weight.

[0035] Solid content: The solid content of electrode slurry refers to the mass percentage of the remaining part of the electrode slurry after drying under specified conditions, that is, the proportion of solid particles (excluding solvent) in the electrode slurry.

[0036] The present application provides a dispersant, which is applied to a battery and can be added to a slurry of an electrode material. The types of batteries include, but are not limited to, lithium-ion batteries, sodium-ion batteries, or potassium-ion batteries. The slurry of the electrode material includes a positive electrode active material, a positive electrode lithium supplement material, and a conductive agent. Of course, in other embodiments, the dispersant can also be added to the negative electrode material.

[0037] In one embodiment, the dispersant includes a first component and a second component, the first component includes a high molecular weight polymer, the weight average molecular weight of the first component is 8000 to 60000, the second component includes an organic compound, the organic compound includes any one of the functional groups of hydroxyl, carboxyl, and amine, and the weight average molecular weight of the second component is less than or equal to the weight average molecular weight of the first component.

[0038] Among them, the high molecular polymer in the first component is used to stabilize the viscosity of the electrode slurry to avoid the viscosity of the electrode slurry increasing or decreasing due to long-term storage. Optionally, the weight average molecular weight of the first component can be 8000, 10000, 20000, 30000, 40000, 50000, 60000. Optionally, the weight average molecular weight in the first component can be 12000-40000. It should be noted that the high molecular polymer in the first component is used to stabilize the viscosity of the slurry, so its molecular weight should not be too large or too small, because the molecular weight of the high molecular polymer is too large to cause the viscosity of the electrode slurry to be too large, and the molecular weight of the high molecular polymer is too small to cause the viscosity of the electrode slurry to be too small.

[0039] It should be noted that 12000-40000 is the preferred range of the weight average molecular weight of the first component, and the first component outside the above range provided in the present application can also achieve the effects of improving the viscosity stability, slurry gelation and rheological properties of the electrode slurry provided in the present application.

[0040] The organic compound in the second component can be an organic copolymer, and the molecular chain segments of the organic copolymer in the second component can contain any functional group of hydroxyl, carboxyl, and amine. The organic compound in the second component mainly plays the role of reducing the viscosity of the slurry and preventing the slurry from gelling.

[0041] By adding the above-mentioned dispersant provided in the present application to the electrode slurry, the solid content of the electrode slurry can be increased and the viscosity can be reduced. In addition, the dispersant can also reduce the alkalinity of the electrode slurry system, thereby improving the anti-gelation characteristics of the electrode slurry, reducing the risk of electrode slurry gel, and thus improving the utilization rate of slurry coating. At the same time, the dispersant can make the prepared battery have the following effects: 1) Improve the conductivity of the lithium ion battery: The dispersant can effectively improve the dispersibility of the lithium salt in the electrolyte, thereby increasing the migration rate of lithium ions in the electrolyte, thereby increasing the conductivity of the battery; 2) Reduce the internal resistance of the battery: The dispersant can reduce the ohmic impedance inside the battery, reduce the polarization phenomenon, thereby reducing the internal resistance of the battery, and improve the rate performance and cycle life of the battery; 3) Improve the cycle performance of the battery: The dispersant can effectively inhibit the shedding of active substances in the battery during the cycle process, reduce the damage to the electrode structure, and thus improve the cycle performance of the battery; 4) Improve the safety of the battery: The dispersant has good thermal stability and chemical stability, which can reduce the safety hazards of the battery under high temperature or overcharge and overdischarge conditions, and improve the safety of the battery.

[0042] It should be noted that the dispersant provided in the present application is different from the dispersant using the first component or the second component alone in the prior art, because there are certain defects in using the first component or the second component alone. If the dispersant only contains the first component, the viscosity reduction effect and anti-gel effect provided by the dispersant are deteriorated; if the dispersant only contains the second component, the effect of stabilizing the viscosity of the electrode slurry provided by the dispersant is deteriorated, resulting in poor preservation of the electrode slurry. Therefore, in order to solve the above technical problems, the present application needs to use the first component and the second component in combination, so that the two can play a synergistic and complementary role.

[0043] In one embodiment, the high molecular polymer includes one or more of polyvinyl pyrrolidone, a vinyl pyrrolidone copolymer containing a polyether segment, and a nitro-containing polyvinyl pyrrolidone.

[0044] Specifically, the high molecular polymer may include polyvinyl pyrrolidone (PVP), or the high molecular polymer may include a vinyl pyrrolidone copolymer containing a polyether segment. It should be noted that the vinyl pyrrolidone copolymer containing a polyether segment is obtained by copolymerizing a monomer of polyvinyl pyrrolidone (vinyl pyrrolidone, NVP) and at least another organic monomer as raw materials.

[0045] Optionally, the dispersant provided in the present application includes a vinyl pyrrolidone copolymer containing a polyether segment, that is, an ether bond (-RO-R'-) is block copolymerized in the molecular segment of polyvinyl pyrrolidone. The polyether structure in the modified vinyl pyrrolidone copolymer containing a polyether segment is a solvated segment, and the solvated polyether structure can have good affinity for most organic solvents (such as N-methylpyrrolidone), and the steric hindrance effect generated by the polyether structure can prevent the aggregation of electrode materials.

[0046] The carphilic main chain of polyvinyl pyrrolidone or polyvinyl pyrrolidone copolymer containing polyether chain segments in the high molecular polymer is connected with a cyclic hydrocarbon structure. The carphilic main chain has a strong mutual adsorption effect on conductive carbon black and other components in the electrode material through the cyclic hydrocarbon structure, so that the conductive carbon black can be adsorbed to the surface of the positive electrode active material.

[0047] In one embodiment, the organic compound includes one or more of ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups, phenyl acrylate-ethylene oxide copolymer containing hydroxyl groups / amine groups, and nitrile polymers, wherein the nitrile polymers may include polyvinyl nitrile, polyacrylonitrile, and the like.

[0048] Optionally, the organic compound may include an alkyl chain and an ester branched chain connected to the alkyl chain. Specifically, the organic compound includes one or more polymers, and any polymer includes an alkyl chain and an ester branched chain connected to the alkyl chain. It should be noted that the alkyl chain is a molecular segment formed by sequentially connecting carbon atoms, and the molecular structure of the polymer should include a segment consisting of -CCC-; preferably, in a specific embodiment, the alkyl chain serves as the main chain of the polymer, and the ester branched chain is connected to the alkyl chain.

[0049] In other embodiments, the organic compound includes one or more of modified chitosan, polyvinyl alcohol, polyacrylic acid, polyethylene oxide, polyacrylonitrile, polyvinyl chloride, polypropylene, polyurethane, polyimide, and polyetheretherketone. It should be explained that the above polymers can all be modified polymers, and the modified polymers include any functional group of hydroxyl, carboxyl, and amine.

[0050] In one embodiment, the dispersant provided in the present application includes ethylene-vinyl acetate copolymer (EVA) modified with phenolic hydroxyl groups, that is, phenolic hydroxyl groups are blocked in the main chain segment or in the side chain segment of the ethylene-vinyl acetate copolymer. In a specific embodiment, the high molecular polymer includes polyvinyl pyrrolidone, and the organic compound includes ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups.

[0051] In one embodiment, the main chain of the ethylene-vinyl acetate copolymer is an alkyl segment, and the phenolic hydroxyl block is copolymerized in the main chain or side chain of the ethylene-vinyl acetate copolymer, or the side chain of the ethylene-vinyl acetate copolymer may be a substituent having a phenolic hydroxyl group. It is understood that the phenolic hydroxyl group is mainly composed of a benzene ring and a hydroxyl group connected to the benzene ring, so the ethylene-vinyl acetate copolymer containing a phenolic hydroxyl group satisfies the above-mentioned condition that the organic compound includes a hydroxyl group.

[0052] In one embodiment, the ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups can be copolymerized by at least two monomers, such as monomer A and monomer B, wherein monomer A contains phenolic hydroxyl groups, and the molar amount of monomer A is greater than the molar amount of monomer B and other monomers. It can be understood that in the ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups, the phenolic hydroxyl groups contained therein are the main ones that play a role, thereby ensuring that the synthesized ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups has sufficient phenolic hydroxyl groups.

[0053] In one embodiment, the dispersant provided by the present application includes a phenyl acrylate-ethylene oxide copolymer containing a hydroxyl / amine group, which is obtained by copolymerization of phenyl acrylate and ethylene oxide, and a hydroxyl group and an amine group are connected to the chain segment of the copolymer. It is understood that there is an alkyl segment on the repeating unit of phenyl acrylate, and an ester group is also connected to the repeating unit of phenyl acrylate. Therefore, in a specific embodiment, the high molecular polymer includes a vinyl pyrrolidone copolymer containing a polyether segment, and the organic compound includes a phenyl acrylate-ethylene oxide copolymer containing a hydroxyl group and an amine group.

[0054] In one embodiment, the phenyl acrylate-ethylene oxide copolymer containing hydroxyl / amine groups can be copolymerized by at least two monomers, namely, monomer C and monomer D, wherein monomer C contains hydroxyl groups and amine groups, and the molar amount of monomer C is greater than the molar amount of monomer D and other monomers. It can be understood that in the phenyl acrylate-ethylene oxide copolymer containing hydroxyl / amine groups, the hydroxyl groups and amino groups contained therein are mainly effective, thereby ensuring that the synthesized phenyl acrylate-ethylene oxide copolymer containing hydroxyl / amine groups has sufficient hydroxyl groups and amino groups.

[0055] In other embodiments, the dispersant provided by the present application may also include an organic compound (polymer) containing a carboxyl group. Furthermore, the organic compound containing a carboxyl group may be copolymerized from a monomer E or at least two monomers, wherein the monomer E contains a carboxyl group. In the organic compound copolymerized from at least two monomers, the molar amount of the monomer E is greater than the molar amount of the other monomers.

[0056] The alkyl chains in the organic compounds in the above embodiments have good solvent compatibility, and the ester groups contained have good affinity for polyvinylidene fluoride, which can control the stretching morphology of polyvinylidene fluoride molecules in the solvent and avoid cross-linking inside the polyvinylidene fluoride molecules, so that the molecules of the polyvinylidene fluoride binder can be effectively dispersed on the surface of the positive electrode active material during the film formation process, thereby ultimately improving the flexibility of the dry film.

[0057] In one embodiment, the ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups is copolymerized by a phenolic hydroxyl group-containing monomer and ethylene-vinyl acetate in a molar ratio of 1:(0.5-1). Optionally, the copolymerization molar ratio of the phenolic hydroxyl group-containing monomer and ethylene-vinyl acetate is 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.

[0058] In one embodiment, the phenyl acrylate-ethylene oxide copolymer is copolymerized by phenyl acrylate containing hydroxyl and amine groups and ethylene oxide in a molar ratio of 1: (0.5-1). Optionally, the copolymerization molar ratio of phenyl acrylate containing hydroxyl and amine groups and ethylene oxide is 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.

[0059] In one embodiment, the weight average molecular weight of the second component is 500 to 8000, and the weight average molecular weight of the second component may be 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000. Optionally, the weight average molecular weight of the second component may be 1000 to 6000. It should be noted that 1000 to 6000 is a preferred range of the weight average molecular weight of the second component, and the second component outside the above range provided in the present application can also achieve the effects of improving the viscosity stability of the electrode slurry, slurry gelation and rheological properties provided in the present application.

[0060] In a specific embodiment, the weight average molecular weight of the first component and the second component may be the same, and the weight average molecular weight of the first component and the weight average molecular weight of the second component may both be 20000. In other embodiments, the weight average molecular weight of the first component and the second component may be different, and the weight average molecular weight of the first component may be 8000, and the weight average molecular weight of the second component may both be 60000. Alternatively, the weight average molecular weight of the first component may be 12000, and the weight average molecular weight of the second component may both be 40000.

[0061] In one embodiment, the mass ratio of the first component to the second component is 1:(0.1-1). Optionally, the mass ratio of the first component to the second component can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1. Meeting the above mass ratio allows the first component and the second component to fully exert their own functions, on the one hand providing an adsorption effect so that the conductive carbon black can be adsorbed to the surface of the positive electrode active material; on the other hand providing film forming properties.

[0062] In one embodiment, the dispersant further includes a third component, which includes an organic solvent and alcohol small molecules, amine small molecules, ester small molecules, and phenol substances containing hydroxyl groups and / or carboxyl groups dissolved in the organic solvent.

[0063] The organic solvent may include N-methylpyrrolidone (NMP).

[0064] Optionally, the alcohol small molecule includes one or more of polyethylene glycol, 2-hydrazinoethanol, 2-mercaptoethanol, ethylene glycol, and propylene glycol.

[0065] Optionally, the alcoholamine small molecules include one or more of succinamide, polyetheramine, polyethyleneimine, isopropanolamine, ethanolamine, diethanolamine, and triethanolamine.

[0066] Optionally, the ester small molecules include one or more of butyl oxalate, ethyl oxalate, dimethyl carbonate, and diethyl carbonate.

[0067] Optionally, the phenolic substances containing hydroxyl groups and / or carboxyl groups include one or more of salicylic acid, tannic acid, and caffeic acid.

[0068] In a specific embodiment, the organic solvent, the alcohol small molecules, the alcohol amine small molecules, and the ester small molecules can be compounded in a weight ratio of 1:0.01-0.1:0.01-0.1:0.01-0.1.

[0069] The present application adds alcohol amine small molecules to the dispersant, which can effectively reduce the viscosity of the electrode slurry and increase the solid content, thereby enhancing the uniform dispersion of the electrode material; and the alcohol amine small molecules can interact with the functional groups on the surface of the electrode material to form a stable interface layer, which is conducive to the rapid transmission of electrons and ions; the present application adds phenolic substances containing hydroxyl and / or carboxyl groups to the dispersant, which can provide a certain proportion of acidic groups for the dispersant, reduce the alkalinity of the system, and reduce the risk of slurry gel. In addition, the above small molecule additives can also stabilize the viscosity of the electrode slurry, avoiding the increase or decrease in viscosity of the electrode slurry during long-term storage.

[0070] In one embodiment, the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1: (8-20). It should be noted that the above ratio refers to the ratio of the mass sum G1 of the first component and the second component to the mass G2 of the third component. Optionally, the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20.

[0071] In one embodiment, the viscosity of the dispersant is 30mPa·s to 200mPa·s. Optionally, the viscosity of the dispersant can be 30mPa·s, 50mPa·s, 70mPa·s, 90mPa·s, 110mPa·s, 130mPa·s, 150mPa·s, 170mPa·s, 200mPa·s. Among them, the viscosity of the dispersant will affect the viscosity of the electrode slurry, and the viscosity of the electrode slurry is closely related to the stability of the slurry. The embodiment of the present application controls the viscosity of the dispersant within the above range: on the one hand, it avoids excessively high viscosity of the electrode slurry, improves the fluidity and coating effect of the slurry; on the other hand, it avoids problems such as poor slurry stability and particle agglomeration caused by too low viscosity of the electrode slurry. It should be noted that the viscosity of the dispersant refers to the corresponding viscosity after the solvent is added to the dispersant.

[0072] In one embodiment, the water content of the dispersant is less than 3000ppm. Optionally, the water content of the dispersant can be 3000ppm, 2000ppm, 1000ppm, 500ppm, 300ppm, 100ppm, 50ppm. Among them, controlling the water content of the dispersant within the above range is conducive to avoiding the decrease in the solid content of the slurry due to the addition of the dispersant to the electrode slurry. It should be noted that the water content of the dispersant refers to the water content corresponding to the addition of the solvent to the dispersant.

[0073] This application also provides a method for preparing a dispersant, please refer to Figure 1 The preparation method of the dispersant is used to prepare the dispersant provided in the above embodiment, and the specific steps include:

[0074] Step S10, compounding the first component and the second component to obtain a compound.

[0075] Step S20, putting the compound into a reaction kettle, and uniformly mixing them in a protective atmosphere to obtain a dispersant.

[0076] Specifically, in step S10, the weight average molecular weight of the first component is 8000-60000, and the second component includes an organic compound, and the organic compound includes any functional group of hydroxyl, carboxyl, and amine.

[0077] Optional, please refer to Figure 2 In step S20, the compound is put into a reaction kettle and uniformly mixed in a protective atmosphere to obtain a dispersant, which specifically includes the following steps:

[0078] Step S21, under the protection of nitrogen, inject the compounded organic solvent into a closed reactor; open the vent valve on the reactor, start stirring, and add the compounded compound.

[0079] Step S22, after the feeding is completed, the reactor cover is closed, the vent valve is opened, the mixture is stirred and mixed evenly under nitrogen protection and room temperature, and the product is demagnetized by circulation.

[0080] Step S23, after the product has passed the inspection, filling is carried out under nitrogen protection and constant temperature and humidity conditions.

[0081] Optionally, under nitrogen protection, the stirring and mixing time is 1 h to 3 h.

[0082] Optionally, the demagnetization processing time is 1h to 2h.

[0083] The preparation method of the dispersant provided in the present application is used to prepare the dispersant provided in the above-mentioned embodiment. The preparation method has a simple process, does not require complicated equipment and conditions, has low cost, is suitable for large-scale production and application, and can obtain a dispersant with excellent dispersing effect and compatibility.

[0084] In one embodiment, the present application further provides an electrode material, which includes an electrode active material and the dispersant provided in the above embodiment, and the electrode active material is a positive electrode active material or a negative electrode active material.

[0085] Among them, the positive electrode active material can reversibly deintercalate active lithium ions, and the active lithium ions migrate between the positive electrode and the negative electrode of the battery to realize battery charging and discharging. The positive electrode active material can be a phosphate positive electrode active material and a ternary positive electrode active material. Exemplarily, the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, fluorolithium vanadium phosphate, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. And lithium supplement materials can be added to the positive electrode active material. Exemplarily, the lithium supplement material can be lithium iron-rich lithium, lithium cobalt-rich lithium, lithium nickel-rich lithium, etc.

[0086] In one embodiment, the present application also provides a secondary battery. The secondary battery can be a composition system commonly used in the prior art, for example including a negative electrode plate, an electrolyte membrane and a positive electrode plate. The electrolyte can be a solid electrolyte or a liquid electrolyte. When a solid electrolyte is selected, the use of a diaphragm can be adaptively selected; the positive electrode plate includes a current collector and an electrode material layer arranged on the current collector, and the electrode material layer includes the dispersant provided above.

[0087] The secondary battery includes an electrode material and a dispersant as provided in the above embodiment. Specifically, the electrode material may include a positive electrode active material and a positive electrode lithium supplement material. Optionally, the positive electrode active material may be a phosphate positive electrode active material and a ternary positive electrode active material, and in a specific embodiment, includes one or more of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium vanadium phosphate fluoride, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0088] The technical solution of the present application is described in detail below through specific embodiments.

[0089] Example 1

[0090] This embodiment provides a dispersant, which includes a first component, a second component and a third component. The first component includes polyvinyl pyrrolidone, the second component includes phenolic hydroxyl group-containing ethylene-vinyl acetate copolymer; the third component includes N-methyl pyrrolidone, 2-hydrazinoethanol, isopropanolamine, and butyl oxalate.

[0091] Among them, the mass ratio of the first component to the second component is 1:1; the mass ratio of the sum of the masses of the first component and the second component to the third component is 1:10; the mass ratio of N-methylpyrrolidone, 2-hydrazinoethanol, isopropanolamine, and butyl oxamate is 1:0.05:0.05:0.05.

[0092] The ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups is prepared by copolymerizing a phenolic hydroxyl group-containing monomer and ethylene-vinyl acetate in a molar ratio of 1:1; the weight average molecular weight of the first component is 22000, and the weight average molecular weight of the second component is 1000.

[0093] The preparation method of the dispersant provided in this embodiment is as follows:

[0094] 1) Inject the organic solvent prepared in proportion into a closed reactor under nitrogen protection, slowly open the vent valve on the reactor, start stirring, and add the dispersed components prepared in proportion.

[0095] 2) After the feeding is completed, immediately close the reactor cover, open the vent valve, mix evenly under nitrogen protection and room temperature conditions, and demagnetize the product by circulating.

[0096] 3) After the product has passed the inspection, it is filled under nitrogen protection and constant temperature and humidity conditions.

[0097] Example 2

[0098] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 2 and that provided in Embodiment 1 is that the first component includes vinyl pyrrolidone containing a polyether segment.

[0099] The steps for preparing the dispersant provided in this embodiment are basically the same as those in Example 1.

[0100] Example 3

[0101] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 3 and that provided in Embodiment 1 is that the second component includes a phenyl acrylate-ethylene oxide copolymer containing hydroxyl / amine groups.

[0102] The steps for preparing the dispersant provided in this embodiment are basically the same as those in Example 1.

[0103] Example 4

[0104] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 4 and that provided in Embodiment 1 is that the mass ratio of the first component to the second component is 1:0.1.

[0105] The steps for preparing the dispersant provided in this embodiment are basically the same as those in Example 1.

[0106] Example 5

[0107] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 5 and that provided in Embodiment 1 is that the mass ratio of the first component to the second component is 1:0.5.

[0108] The steps for preparing the dispersant provided in this embodiment are the same as those in Example 1.

[0109] Example 6

[0110] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 6 and that in Embodiment 1 is that the phenolic hydroxyl-containing ethylene-vinyl acetate copolymer is prepared by copolymerizing a phenolic hydroxyl-containing monomer and ethylene-vinyl acetate in a molar ratio of 1:0.5.

[0111] The steps for preparing the dispersant provided in this embodiment are the same as those in Example 1.

[0112] Example 7

[0113] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 7 and that in Embodiment 1 is that the phenolic hydroxyl-containing ethylene-vinyl acetate copolymer is prepared by copolymerizing a phenolic hydroxyl-containing monomer and ethylene-vinyl acetate in a molar ratio of 1:0.7.

[0114] The steps for preparing the dispersant provided in this embodiment are the same as those in Example 1.

[0115] Example 8

[0116] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 9 and that in Embodiment 1 is that the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:8.

[0117] The steps for preparing the dispersant provided in this embodiment are the same as those in Example 1.

[0118] Example 9

[0119] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 9 and that in Embodiment 1 is that the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:20.

[0120] The steps for preparing the dispersant provided in this embodiment are the same as those in Example 1.

[0121] Example 10

[0122] The present embodiment provides a dispersant, which includes a first component, a second component and a third component. The first component includes a vinyl pyrrolidone copolymer containing a polyether segment, the second component includes a hydroxyl / amine-containing phenyl acrylate and ethylene oxide copolymer, and the third component includes N-methylpyrrolidone, isopropanolamine and salicylic acid.

[0123] Among them, the mass ratio of the first component to the second component is 1:1; the mass ratio of the sum of the masses of the first component and the second component to the third component is 1:10; the mass ratio of N-methylpyrrolidone, 2-hydrazinoethanol, isopropanolamine, and butyl oxamate is 1:0.05:0.05:0.05.

[0124] The phenyl acrylate-ethylene oxide copolymer is prepared by copolymerizing phenyl acrylate containing hydroxyl and amine groups and ethylene oxide in a molar ratio of 1:1. The weight average molecular weight of the first component is 28,000, and the weight average molecular weight of the second component is 600.

[0125] The preparation method of the dispersant provided in this embodiment is as follows:

[0126] 1) The organic solvent and the dispersing components are compounded in proportion, and injected into a closed reactor under nitrogen protection, the vent valve on the reactor is slowly opened, stirring is started, and the dispersing components compounded in proportion are added.

[0127] 2) After the feeding is completed, immediately close the reactor cover, open the vent valve, mix evenly under nitrogen protection and room temperature conditions, and demagnetize the product by circulating.

[0128] 3) After the product has passed the inspection, it is filled under nitrogen protection and constant temperature and humidity conditions.

[0129] Embodiment 11

[0130] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 11 and that provided in Embodiment 10 is that the weight average molecular weight of the second component is 2000.

[0131] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0132] Example 12

[0133] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 12 and that provided in Embodiment 10 is that the weight average molecular weight of the first component is 8,000.

[0134] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0135] Embodiment 13

[0136] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 13 and that provided in Embodiment 10 is that the mass ratio of the first component to the second component is 1:0.1.

[0137] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0138] Embodiment 14

[0139] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 14 and that provided in Embodiment 10 is that the mass ratio of the first component to the second component is 1:0.5.

[0140] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0141] Embodiment 15

[0142] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 15 and that in Embodiment 10 is that the phenyl acrylate-ethylene oxide copolymer is copolymerized by phenyl acrylate containing hydroxyl and amine groups and ethylene oxide in a molar ratio of 1:0.5.

[0143] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0144] Example 16

[0145] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 16 and Embodiment 10 is that the phenyl acrylate-ethylene oxide copolymer is copolymerized by phenyl acrylate containing hydroxyl and amine groups and ethylene oxide in a molar ratio of 1:0.7.

[0146] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0147] Embodiment 17

[0148] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 17 and that provided in Embodiment 10 is that the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:8.

[0149] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0150] Embodiment 18

[0151] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 18 and that provided in Embodiment 10 is that the mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:20.

[0152] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 10.

[0153] Embodiment 19

[0154] This embodiment provides a dispersant. The difference between the dispersant provided in Embodiment 19 and that in Embodiment 1 is that the third component includes only N-methylpyrrolidone.

[0155] The preparation steps of the dispersant provided in this embodiment are the same as those in Example 1.

[0156] Comparative Example 1

[0157] This comparative example provides a dispersant, which includes a third component, and the third component includes N-methylpyrrolidone, 2-hydrazinoethanol, isopropanolamine, and butyl oxamate. The mass ratio of N-methylpyrrolidone, 2-hydrazinoethanol: isopropanolamine, and butyl oxamate is 1:0.05:0.05:0.05.

[0158] Comparative Example 2

[0159] This comparative example provides a dispersant, which includes a second component and a third component, wherein the second component includes an ethylene-vinyl acetate copolymer containing a phenolic hydroxyl group; and the third component includes N-methylpyrrolidone, 2-hydrazinoethanol, isopropanolamine, and butyl oxamate. The mass ratio of N-methylpyrrolidone, 2-hydrazinoethanol: isopropanolamine, and butyl oxamate is 1:0.05:0.05:0.05. The mass ratio of the second component to the third component is 1:10. The ethylene-vinyl acetate copolymer containing a phenolic hydroxyl group is copolymerized by a phenolic hydroxyl group-containing monomer and ethylene-vinyl acetate in a molar ratio of 1:1. The weight average molecular weight of the second component is 1000.

[0160] Comparative Example 3

[0161] This comparative example provides a dispersant, which includes a first component and a third component, wherein the first component includes a vinyl pyrrolidone copolymer containing a polyether segment; and the third component includes N-methyl pyrrolidone, isopropanolamine and salicylic acid. The mass ratio of N-methyl pyrrolidone, isopropanolamine and salicylic acid is 2.25.5:4.5:2.25:0.1. The mass ratio of the first component to the third component is 1:10. The weight average molecular weight of the first component is 12000.

[0162] Comparative Example 4

[0163] This comparative example provides a dispersant, which includes a second component and a third component, wherein the second component includes a copolymer of phenyl acrylate and ethylene oxide containing a hydroxyl group / amine group; and the third component includes N-methylpyrrolidone, isopropanolamine and salicylic acid. The mass ratio of N-methylpyrrolidone, isopropanolamine and salicylic acid is 2.25.5:4.5:2.25:0.1. The mass ratio of the second component to the third component is 1:10. The weight average molecular weight of the second component is 600.

[0164] The dispersant parameters provided by Examples 1 to 19 and Comparative Examples 1 to 4 are shown in Table 1:

[0165] Table 1 Dispersant parameters provided in Examples and Comparative Examples

[0166]

[0167]

[0168] The dispersants provided in the above-mentioned Examples 1 to 19 and the dispersants provided in Comparative Examples 1 to 4 were respectively prepared into positive electrode slurries, positive electrode sheets and lithium-ion batteries according to the following methods:

[0169] Positive electrode slurry: lithium iron phosphate (Yuneng YN7), conductive agent SP (conductive carbon black), binder PVDF (polyvinylidene fluoride), and dispersant are added into a ball mill at a mass ratio of 96.5:1.3:2.2:0.386, and according to the set slurry solid content value, the corresponding solvent NMP is added, and the mixture is mixed and ball-milled to obtain the positive electrode slurry;

[0170] Positive electrode sheet: The positive electrode slurry is coated on the surface of the aluminum foil, rolled, and vacuum dried at 110°C overnight to obtain a positive electrode sheet;

[0171] Negative electrode sheet: Graphite, binder CMC (carboxymethyl cellulose), binder SBR (styrene-butadiene rubber) and conductive agent SP are mixed and ball-milled in a mass ratio of 95.8:1.2:2:1 to obtain a negative electrode slurry, the negative electrode slurry is coated on the surface of copper foil, and vacuum dried at 110°C overnight to obtain a negative electrode sheet;

[0172] Electrolyte: Ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3:7, and LiPF6 was added to form an electrolyte, and the concentration of LiPF6 was 1 mol / L;

[0173] Diaphragm: polypropylene microporous diaphragm;

[0174] Lithium-ion battery assembly: Assemble button-type lithium-ion full batteries in an inert atmosphere glove box in the order of graphite negative electrode sheet - separator - electrolyte - positive electrode sheet.

[0175] Related performance tests

[0176] Viscosity reduction test:

[0177] After preparing the positive electrode slurry with a solid content of 54%, a viscometer was used to test the viscosity of the positive electrode slurry at a speed of 30 rpm after being left for 0.5 h.

[0178] Slurry solid content test:

[0179] A blank group positive electrode slurry is provided, the blank group positive electrode slurry includes lithium iron phosphate, a conductive agent SP and a binder PVDF, and its solid content is measured to be 48% when the viscosity value of the blank group positive electrode slurry is 8000 mPa·s; then, the solid contents of the positive electrode slurries corresponding to the embodiments and the comparative examples are respectively measured when the viscosity value is 8000 mPa·s, and the increase in the solid content of each embodiment and the comparative example relative to the blank group is calculated.

[0180] Electrochemical performance test:

[0181] The first-cycle charge specific capacity and the first-cycle discharge specific capacity of the lithium-ion batteries corresponding to the test examples and comparative examples were tested, and the first-cycle efficiency (first-cycle discharge specific capacity / first-cycle charge specific capacity) was calculated. The test conditions were as follows: constant current and constant voltage charging, the first-cycle charge and discharge voltage was 2.0-3.75V, the current was 0.1C, and the cut-off current was 0.01C.

[0182] The test results are shown in Table 2.

[0183] Table 2 Test results of embodiments and comparative examples

[0184]

[0185]

[0186] From the test results of Examples 1 to 19 and Comparative Examples 1 to 3 in Table 1, it can be seen that the slurry solid content of the dispersant prepared in the examples is higher than the slurry solid content in the comparative examples; and the electronic resistivity of the positive electrode sheets in the examples is lower than that of the positive electrode sheets in the comparative examples; the buckling charge and discharge capacity in the examples is also higher than that of the comparative examples, indicating that the dispersant provided in this application has the excellent performance of uniformly dispersing the slurry and reducing viscosity and increasing solidity. The single organic substance in the comparative example cannot play a good dispersing effect, because its molecular weight is large and the organic matter is not conductive, resulting in an increase in the resistivity of the electrode sheet and a decrease in the buckling capacity.

[0187] From the test results of Examples 1 to 3 and 10 to 12 in Table 1, it can be seen that in Examples 1 to 3, as the polyether segment is added to the chain of the first component and other functional groups are added to the chain of the second component, the solid content of the slurry can be further improved, the 24-hour slurry viscosity stabilization effect is significantly improved, the electrode resistivity is reduced, and the capacitive capacitance is basically the same as the blank group. This is because the modified PVP material forms a tight bond with the LFP-coated carbon layer, making the particles more evenly dispersed, thereby playing a role in increasing solid and reducing viscosity. In Examples 10 to 12, as the molecular weight of the first component or the second component is adjusted, the solid content of the slurry and the 24-hour slurry viscosity stabilization effect will be affected, especially when the molecular weight of the first component decreases, the electrode resistivity increases, which shows that the molecular weight of the first component and the second component has a particularly important effect on the performance of the dispersant.

[0188] From the test results of Example 1, Example 4, Example 5, Example 10, Example 13 and Example 14 in Table 1, it can be learned that as the quality of the first component and the second component increases, the effect of solidification and viscosity reduction of the slurry is also good, the resistivity of the electrode sheet increases accordingly, and the charge-discharge capacity increases. This is because the content of the second component is high, and it is easier for it to generate bonding force on the surface of the carbon coating layer of the positive electrode particles, further improving the viscosity reduction effect of the slurry.

[0189] From the test results of Example 1, Example 6, Example 7, Example 10, Example 15 and Example 16 in Table 1, it can be learned that as the molar ratio between the monomers of the second component increases, the effect of solidification and viscosity reduction of the slurry is also good, the resistivity of the electrode sheet increases accordingly, and the charge capacity increases. This is because the uniform polymerization of the second component makes the functional groups evenly distributed, which makes it easier to generate binding force on the surface of the carbon coating layer of the positive electrode particles, further improving the viscosity reduction effect of the slurry.

[0190] From the test results of Example 1, Example 8, Example 9, Example 10, Example 17 and Example 18 in Table 1, it can be learned that as the ratio of the sum of the masses of the first component and the second component to the mass of the third component decreases, the third component accounts for a larger proportion, the actual solid content of the dispersant will be greatly reduced, resulting in a reduction in the effective content of the dispersant, and the contact between the effective substance of the dispersant and the particulate carbon coating will be greatly reduced, the effect of the slurry in increasing solids and reducing viscosity will become worse, the resistivity of the electrode will increase accordingly, and the withholding capacitance will decrease.

[0191] From the test results of Example 1 and Example 19 in Table 1, it can be seen that the small molecule additives in the third component can also stabilize the viscosity of the electrode slurry, avoiding the increase or decrease in viscosity of the electrode slurry during long-term storage. Therefore, the 24h slurry viscosity stabilization effect of Example 1 with the addition of small molecule additives is significantly improved.

[0192] In summary, effectively formulated dispersants can effectively improve the processing properties of slurry, reduce viscosity and increase solids, evenly disperse particles, and prolong the processing stability of slurry.

[0193] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or positional relationship of the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0194] What is disclosed above is only a preferred embodiment of the present application, and it certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiment and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A dispersant, characterized in that: The invention comprises a first component and a second component, wherein the first component comprises a high molecular weight polymer, the weight average molecular weight of the first component is 8000 to 60000, the second component comprises an organic compound, the organic compound comprises any one of the functional groups of hydroxyl, carboxyl and amine, and the weight average molecular weight of the second component is less than or equal to the weight average molecular weight of the first component.

2. The dispersant according to claim 1, characterized in that The high molecular polymer includes one or more of polyvinyl pyrrolidone, polyvinyl pyrrolidone copolymer containing polyether segments, and polyvinyl pyrrolidone containing nitro groups; and / or the organic compound includes one or more of ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups, phenyl acrylate-ethylene oxide copolymer containing hydroxyl groups / amine groups, and nitrile polymers.

3. The dispersant according to claim 2, characterized in that The ethylene-vinyl acetate copolymer containing phenolic hydroxyl groups is copolymerized with ethylene-vinyl acetate in a molar ratio of 1: (0.5-1) by phenolic hydroxyl-containing monomers; and / or the phenyl acrylate-ethylene oxide copolymer is copolymerized with phenyl acrylate containing hydroxyl groups and amine groups and ethylene oxide in a molar ratio of 1: (0.5-1) by ...

4. The dispersant according to claim 1, characterized in that The weight average molecular weight of the first component is 12000-40000; and / or, the weight average molecular weight of the second component is 500-8000; and / or, the mass ratio of the first component to the second component is 1:(0.1-1).

5. The dispersant according to any one of claims 1 to 4, characterized in that The dispersant further comprises a third component, which comprises an organic solvent and one or more of alcohol small molecules, amine small molecules, ester small molecules, and phenol substances containing hydroxyl groups and / or carboxyl groups dissolved in the organic solvent.

6. The dispersant according to claim 5, characterized in that The alcohol small molecule includes one or more of polyethylene glycol, 2-hydrazinoethanol, 2-mercaptoethanol, ethylene glycol, and propylene glycol; and / or The alcoholamine small molecules include one or more of succinamide, polyetheramine, polyethyleneimine, isopropanolamine, ethanolamine, diethanolamine, and triethanolamine; and / or The ester small molecules include one or more of butyl oxalate, ethyl oxalate, dimethyl carbonate, and diethyl carbonate; and / or The phenolic substances containing hydroxyl groups and / or carboxyl groups include one or more of salicylic acid, tannic acid and caffeic acid.

7. The dispersant according to claim 5, characterized in that The mass ratio of the sum of the mass of the first component and the second component to the mass of the third component is 1:(8-20); and / or, The viscosity of the dispersant is 30 mPa·s to 200 mPa·s; and / or, The water content of the dispersant is less than 3000 ppm.

8. A method for preparing a dispersant, characterized in that: The preparation method comprises the following steps: Compounding the first component and the second component to obtain a compound; The compound is put into a reaction kettle and mixed evenly in a protective atmosphere to obtain a dispersant; Among them, the first component contains a high molecular weight polymer, the weight average molecular weight of the first component is 8000-60000, the second component contains an organic compound, the organic compound includes any one of the functional groups of hydroxyl, carboxyl and amine, and the weight average molecular weight of the second component is less than or equal to the weight average molecular weight of the first component.

9. An electrode material, characterized in that: The invention comprises an electrode active material and a dispersant as claimed in any one of claims 1 to 7, wherein the electrode active material is a positive electrode active material or a negative electrode active material.

10. A secondary battery, characterized in that: The electrode material as claimed in claim 9 or the secondary battery comprises the dispersant as claimed in any one of claims 1 to 7.

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