Dispersant composition for positive electrode material, and preparation method therefor and use thereof

Abstract

Provided are a dispersant composition for a positive electrode material, and a preparation method therefor and the use thereof. The dispersant composition for a positive electrode material comprises a combination of a first dispersant, a second dispersant and a third dispersant, wherein the first dispersant is a diblock copolymer of phenylalkyl acrylate and ethylene oxide; the second dispersant is a triblock copolymer of phenylalkyl acrylate, acrylic acid and ethylene oxide; and the third dispersant is alkyl phthalate. The dispersant composition for a positive electrode material can not only solve the technical problem of increased viscosity of a ternary positive electrode slurry due to the overly large surface adsorbability of a conductive agent material during a processing process of the slurry, but can also solve the problems of gelatinization of a polyvinylidene fluoride binder in a slightly alkaline system of the ternary positive electrode slurry and poor flexibility of an electrode sheet during coating and drying processes of the slurry.

Description

A positive electrode material dispersant composition and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 1, 2023, with application number 202310959297.3 and application name “A positive electrode material dispersant composition, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of dispersant materials, and in particular relates to a positive electrode material dispersant composition, a preparation method and an application thereof. Background Art

[0003] With the rapid development of 3C electronic products, new energy vehicles and wearable electronic products, the development of lithium-ion batteries has received widespread attention. Ternary positive electrode materials have become one of the research hotspots due to their advantages such as high theoretical specific capacity (up to 274mAh / g), high reaction platform voltage (3.0-4.4V) and low cost.

[0004] During the processing of battery cells using ternary positive electrode materials, it is necessary to mix the ternary positive electrode material powder, conductive carbon black, binder and N-methylpyrrolidone to prepare a slurry, which is then coated on the surface of the aluminum foil current collector and finally dried to prepare the positive electrode sheet. In order to further improve the specific capacity of the battery, the prior art discloses the use of NCM811 with a high nickel content to replace the previously common NCM111 and NCM523 positive electrode materials. This results in an increase in the viscosity of the positive electrode slurry during processing, and as the slurry changes over time, gelation occurs, which seriously affects the coating effect of the slurry. In addition, in order to improve processing efficiency, most researchers use a preparation process that increases the solid content of the positive electrode slurry, but the above process can cause problems such as cracking of the positive electrode sheet during the drying process.

[0005] In response to the above problems, technicians in this field have conducted extensive research. The commercial lithium iron phosphate dispersants previously used cannot meet the application requirements of battery cell system processing using ternary positive electrode materials due to their narrow voltage window or matching problems.

[0006] Therefore, there is an urgent need to develop a dispersant that can effectively reduce the viscosity of the positive electrode slurry and improve the flexibility of the electrode while ensuring that the ternary positive electrode material slurry has a high solid content.

[0007] Summary of the Invention

[0008] In response to the shortcomings of the prior art, the present invention aims to provide a cathode material dispersant composition, its preparation method, and its application. The cathode material dispersant composition provided by the present invention not only solves the technical problem of increased slurry viscosity during the processing of ternary cathode slurries due to excessive surface adsorption of the conductive material, but also addresses the problems of gelation of the polyvinylidene fluoride binder in the alkaline system of the ternary cathode slurry and the poor flexibility of the electrode sheets during the coating and drying process of the slurry.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a positive electrode material dispersant composition, the positive electrode material dispersant composition comprising a combination of a first dispersant, a second dispersant, and a third dispersant;

[0011] The first dispersant is a diblock copolymer of phenylalkyl acrylate and ethylene oxide;

[0012] The second dispersant is a triblock copolymer of phenylalkyl acrylate, acrylic acid and ethylene oxide;

[0013] The third dispersant is an alkyl phthalate.

[0014] The present invention uses a first dispersant that facilitates the dispersion of the conductive agent, a second dispersant that assists in dispersion, and a third dispersant that increases flexibility to prepare a positive electrode material dispersant composition. The carbon-philic main chain in the first dispersant structure contains a benzene ring structure, and the solvated main chain is a polyether structure. The carbon-philic main chain has a strong mutual adsorption effect on conductive carbon black and other components through the benzene ring structure, causing them to adsorb to the surface of the material. The solvated polyether segment has a good affinity for the N-methylpyrrolidone solvent, and the resulting steric hindrance effect can prevent material aggregation.

[0015] The second dispersant adds acrylic acid groups to its structure, which can provide a certain proportion of acidic groups and reduce the alkalinity of the system. At the same time, the second dispersant also has a dispersing effect on the conductive material, and the working principle is the same as the first dispersant.

[0016] The alkyl chain in the third dispersant structure has good solvent compatibility, and the ester group it contains has good affinity for polyvinylidene fluoride, which can control the stretching morphology of polyvinylidene fluoride molecules in the solvent and avoid cross-linking within the polyvinylidene fluoride molecules. In this way, 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.

[0017] In addition, the first dispersant acts by adsorbing on the surface of the ternary main material and the conductive carbon material, thereby reducing the viscosity of the slurry. It is the main dispersant component for reducing the viscosity of the system and has no ability to adjust the pH. If used alone, it cannot solve the gel problem and affects the effect of reducing the viscosity of the system.

[0018] The second dispersant is mainly designed to contain an acidic component, which can adjust the pH value of the high-alkaline slurry and reduce the gel risk of the adhesive (polyvinylidene fluoride). Although this structure has the acrylate functional group of the first dispersant, using this component to replace the first dispersant will make the pH value unable to be adjusted, affecting the performance of the product.

[0019] Preferably, the structural formula of the first dispersant is as shown in Formula I:

[0020] Wherein, R1 is selected from a C1-5 hydrocarbon group, R2 is selected from a C1-20 hydrocarbon group, and the value ranges of n and p are independently 1-500.

[0021] In the present invention, R1 is selected from a C1-5 hydrocarbon group, for example, R1 can be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0022] Furthermore, R1 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0023] In the present invention, R2 is selected from a C1-20 hydrocarbon group, for example, R1 can be at least one of a C1-20 alkyl group, a C2-20 alkenyl group or a C2-20 alkynyl group.

[0024] Furthermore, R2 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, decyl, vinyl, propenyl, butenyl, pentenyl, dodecenyl, octadecenyl, ethynyl, propynyl, butynyl, pentynyl, dodecynyl or octadecynyl.

[0025] In the present invention, the value range of n and p is independently 1-500, for example, it can be 1, 2, 5, 8, 10, 15, 20, 25, 30, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500, etc.

[0026] In the present invention, by regulating the range of n and p values, the dispersant molecules have a sufficient ratio of ester groups to benzene rings, which can form a good coordination adsorption effect with the surface of the particulate material (especially conductive carbon black) in the ternary positive electrode slurry, achieving optimal adsorption effect. At the same time, the polyether molecular chain has good affinity for the NMP solvent, which can make the surface of the particulate material have good solution wettability, improving its dispersion performance in the slurry.

[0027] Preferably, the structural formula of the first dispersant is as shown in Formula I:

[0028] Wherein, R1 is selected from methyl, R2 is selected from C1-5 hydrocarbon group, and the value range of n and p is independently 10-100.

[0029] In the present invention, R2 is selected from a C1-5 hydrocarbon group, for example, R2 can be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0030] Furthermore, R2 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0031] In the present invention, by further optimizing the types of R1 and R2 groups, there is an appropriate free space between the benzene ring structure and the ester functional group, and the ester functional group is more easily adsorbed onto the surface of the ternary main material particles, thereby allowing the conductive agent material mainly composed of carbon elements to approach the surface of the main material particles, avoiding a decrease in conductive performance.

[0032] In the present invention, the values ​​of n and p are independently in the range of 10-100, for example, 10, 15, 20, 25, 30, 50, 80, 100, etc. By further optimizing the value ranges of n and p, the molecular weight of the dispersant is controlled. Under this condition, the number of moles of active ingredient molecules contained in the same added mass of dispersant can be controlled, which is conducive to matching solid particulate matter of different sizes and specific surface areas in the positive electrode slurry, thereby achieving the best dispersion effect.

[0033] Preferably, the structural formula of the second dispersant is as shown in Formula II:

[0034] Wherein, R3 is selected from a C1-5 hydrocarbon group, R4 is selected from a C1-20 hydrocarbon group, and the value ranges of m, l and k are each independently 1-500.

[0035] In the present invention, R3 is selected from a C1-5 hydrocarbon group, for example, R3 can be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0036] Furthermore, R3 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0037] In the present invention, R4 is selected from a C1-20 hydrocarbon group, for example, R4 can be at least one of a C1-20 alkyl group, a C2-20 alkenyl group or a C2-20 alkynyl group.

[0038] Further, R4 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, decyl, vinyl, propenyl, butenyl, pentenyl, dodecenyl, octadecenyl, ethynyl, propynyl, butynyl, pentynyl, dodecynyl or octadecynyl.

[0039] In the present invention, the value range of m, l and k is independently 1-500, for example, it can be 1, 2, 5, 8, 10, 15, 20, 25, 30, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500, etc.

[0040] In the present invention, by regulating the values ​​of m, l, and k, a certain proportion of benzoic acid groups is included in the dispersant molecules, which can reduce the alkalinity of the ternary cathode slurry and hinder the gel aggregation of polyvinylidene fluoride. At the same time, sufficient polyether molecular chain length is ensured, ensuring the dispersibility of each solid component in the slurry.

[0041] Preferably, the structural formula of the second dispersant is as shown in Formula II:

[0042] Wherein, R3 is selected from methyl, R4 is selected from C1-5 hydrocarbon group, and the value range of m, l and k is independently 10-100.

[0043] In the present invention, R4 is selected from a C1-5 hydrocarbon group, for example, R4 can be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0044] Furthermore, R4 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0045] In the present invention, by further optimizing the types of R3 and R4 groups, there is an appropriate free space between the benzene ring structure and the ester functional group, and the ester functional group is more easily adsorbed onto the surface of the ternary main material particles, thereby allowing the conductive agent material mainly composed of carbon elements to approach the surface of the main material particles, avoiding a decrease in conductive performance.

[0046] In the present invention, the value ranges of m, l and k are independently 10-100, for example, 10, 15, 20, 25, 30, 50, 80, 100, etc. By further optimizing the value ranges of m, l and k, the molecular weight of the dispersant is controlled, the molar ratio of the dispersant molecules in the positive electrode slurry is effectively controlled, and the best dispersion effect is provided.

[0047] Preferably, the third dispersant comprises alkyl phthalate and / or alkyl isophthalate.

[0048] Preferably, the number of carbon atoms in the alkyl chain of the third dispersant is 4-20, preferably 5-8, for example, 4, 5, 6, 7, 8, 10, 12, 14, 16, 18, 20, etc.

[0049] In the present invention, by regulating the number of carbon atoms in the alkyl chain in the third dispersant, the alkyl chain forms sufficient spatial hindrance on the surface of polyvinylidene fluoride, accelerating the swelling and molecular stretching of polyvinylidene fluoride, so that polyvinylidene fluoride can be effectively coated on the surface of the ternary main material particles, improving the utilization rate of the adhesive molecules, thereby ensuring that the solid particles can be stably bonded together during the drying process of the electrode, preventing the formation of gaps between the particles, resulting in reduced flexibility of the dry film and breakage.

[0050] In a second aspect, the present invention provides a method for preparing the positive electrode material dispersant composition according to the first aspect, the method comprising the following steps:

[0051] The first dispersant, the second dispersant and the third dispersant are mixed with an organic solvent to obtain the positive electrode material dispersant composition.

[0052] Preferably, based on the total mass of the first dispersant and the second dispersant as 100%, the mass ratio of the first dispersant to the second dispersant is (20-80):(80-20), for example, it can be 20:80, 22:78, 25:75, 28:72, 30:70, 32:68, 35:65, 38:62, 40:60, 42:58, 45:55, 48:52, 50:50, 52:48, 55:45, 58:42, 60:40, 62:38, 65:35, 68:32, 70:30, 72:28, 75:25, 78:22, 80:20, etc.

[0053] Preferably, based on the total mass of the first dispersant, the second dispersant and the third dispersant as 100%, the total mass percentage of the first dispersant and the second dispersant is not less than 60%, for example, it can be 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, 95%, etc.

[0054] Preferably, based on the total mass of the first dispersant, the second dispersant and the third dispersant as 100%, the mass percentage of the third dispersant is not more than 40%, preferably 5-30%, for example, it can be 5%, 8%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0055] In the present invention, by regulating the mass ratio of the first dispersant, the second dispersant and the third dispersant, the dispersant has the functions of both dispersing ability and increasing the flexibility of the slurry. If the total mass percentage of the first dispersant and the second dispersant is too low, it will lead to poor dispersion effect, and vice versa, it will affect the flexibility of the electrode.

[0056] Preferably, the organic solvent comprises N-methylpyrrolidone.

[0057] Preferably, the mixing further includes rotary evaporation.

[0058] Preferably, the temperature of the rotary evaporation treatment is 80° C., and the vacuum degree is less than -0.09 MPa, for example, it can be -0.05 MPa, -0.06 MPa, -0.07 MPa, -0.08 MPa, -0.09 MPa, etc.

[0059] In a third aspect, the present invention provides a positive electrode slurry, comprising a positive electrode active material, a conductive agent, a binder, a dispersant and a solvent, wherein the dispersant is the positive electrode material dispersant composition according to the first aspect.

[0060] Preferably, the positive electrode active material includes a ternary positive electrode material.

[0061] In the present invention, the conductive agent includes but is not limited to conductive carbon black; the binder includes but is not limited to polyvinylidene fluoride; and the solvent includes but is not limited to N-methylpyrrolidone.

[0062] Preferably, the mass ratio of the positive electrode active material, conductive agent, binder, dispersant and NMP solvent is (55-58):(1-3):(1-3):(0.1-0.8):(20-50), for example, it can be 55:3:3:0.8:38.2, 57.6:1.2:1.08:0.12:40, 58:1:1:0.1:39.9, etc.

[0063] Preferably, the present invention provides a method for preparing a positive electrode slurry, which comprises the following steps:

[0064] 1) Mixing and stirring the binder and the solvent to obtain glue solution A;

[0065] 2) adding the cathode material dispersant composition of the present invention to the above-mentioned glue solution A and stirring uniformly to obtain glue solution B;

[0066] 3) Adding the conductive agent to the glue solution B to obtain a conductive agent slurry;

[0067] 4) Adding the positive electrode active material to the conductive agent slurry to obtain a positive electrode slurry.

[0068] In a fourth aspect, the present invention provides a secondary battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein the positive electrode sheet is prepared from the positive electrode slurry according to the third aspect.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] The present invention provides a cathode material dispersant composition that not only improves the dispersibility of the slurry, but also reduces the viscosity of the slurry to within a processable range of 7000-8000 mPa·s, compared to a slurry system with a solid content of 70% or more (the slurry viscosity is 18000 mPa·s or more).

[0071] At the same time, the slurry prepared using the positive electrode material dispersant composition can significantly reduce the gelation phenomenon, and the slurry is kept for more than 18 hours without producing gel (the same slurry system without the addition of the positive electrode material dispersant composition has a gelation time of less than 3 hours);

[0072] The positive electrode material dispersant composition provided by the present invention can improve the flexibility of the electrode. The electrode prepared by a common slurry system with a solid content of 70% has a bending resistance of less than 20 times. After using the positive electrode material dispersant composition provided by the present invention, the bending resistance of the electrode is improved to more than 150 times. DETAILED DESCRIPTION

[0073] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0074] Example 1

[0075] This embodiment provides a positive electrode material dispersant composition, which includes a combination of a first dispersant, a second dispersant, and a third dispersant; the first dispersant is a diblock copolymer of phenylalkyl acrylate (brand: Aladdin, CAS No. 2495-35-4) and ethylene oxide (Merck Supelco standard, CAS No. 75-21-8) as shown in Formula I; the second dispersant is a triblock copolymer of phenylalkyl acrylate, acrylic acid (Merck Sigma-Aldrich, CAS No. 79-10-7) and ethylene oxide (Merck Supelco standard, CAS No. 75-21-8) as shown in Formula II; the third dispersant is amyl phthalate (US Alfa, CAS No. 131-18-0).

[0076] This embodiment also provides a method for preparing the above-mentioned positive electrode material dispersant composition, which comprises the following steps:

[0077] The first dispersant, the second dispersant and the third dispersant in a mass ratio of 50:40:10 were mixed with N-methylpyrrolidone solvent, and the mixture was rotary evaporated at 80° C. and a vacuum degree of −0.06 MPa to obtain the positive electrode material dispersant composition.

[0078] Example 2

[0079] This embodiment provides a positive electrode material dispersant composition, which includes a combination of a first dispersant, a second dispersant and a third dispersant; the first dispersant is a diblock copolymer of 3-phenylpropyl methacrylate (purchased from Shanghai Mairui Biochemical Technology Co., Ltd., CAS No. 3683-14-5) and ethylene oxide (Merck Supelco standard, CAS No. 75-21-8) as shown in Formula I; the second dispersant is a triblock copolymer of 3-phenylpropyl methacrylate (purchased from Shanghai Mairui Biochemical Technology Co., Ltd., CAS No. 3683-14-5), acrylic acid (Merck Sigma-Aldrich, CAS No. 79-10-7-) and ethylene oxide (Merck Supelco standard, CAS No. 75-21-8) as shown in Formula II; the third dispersant is amyl phthalate (American Alfa, CAS No. 131-18-0).

[0080] This embodiment also provides a method for preparing the above-mentioned positive electrode material dispersant composition, which comprises the following steps:

[0081] The first dispersant, the second dispersant and the third dispersant in a mass ratio of 60:25:15 were mixed with N-methylpyrrolidone solvent, and the mixture was rotary evaporated at 80° C. and a vacuum degree of −0.06 MPa to obtain the positive electrode material dispersant composition.

[0082] Example 3

[0083] This embodiment provides a positive electrode material dispersant composition, which includes a combination of a first dispersant, a second dispersant and a third dispersant; the first dispersant is a diblock copolymer of 3-benzoylethyl acrylate (purchased from Wuhan Kemik Company, CAS No. 17450-56-5) and ethylene oxide (Merck Supelco standard, CAS No. 75-21-8) as shown in Formula I; the second dispersant is a triblock copolymer of phenylethyl acrylate, acrylic acid (Merck Sigma-Aldrich, CAS No. 79-10-7) and ethylene oxide (Merck Supelco standard, CAS No. 75-21-8) as shown in Formula II; the third dispersant is amyl phthalate (American Alfa, CAS No. 131-18-0).

[0084] This embodiment also provides a method for preparing the above-mentioned positive electrode material dispersant composition, which comprises the following steps:

[0085] The first dispersant, the second dispersant and the third dispersant in a mass ratio of 30:55:15 were mixed with N-methylpyrrolidone solvent, and the mixture was rotary evaporated at 80° C. and a vacuum degree of −0.06 MPa to obtain the positive electrode material dispersant composition.

[0086] Example 4

[0087] The difference between this embodiment and embodiment 1 is that R1 of the phenylalkyl acrylate structural unit in the first dispersant is ethyl, and the rest is the same as in embodiment 1.

[0088] Example 5

[0089] The difference between this embodiment and embodiment 1 is that R2 of the phenylalkyl acrylate structural unit in the first dispersant is an octyl group, and the rest is the same as in embodiment 1.

[0090] Example 6

[0091] The difference between this embodiment and embodiment 1 is that the value range of n and p in the first dispersant is both 5, and the rest is the same as embodiment 1.

[0092] Example 7

[0093] The difference between this embodiment and embodiment 1 is that the value range of n and p in the first dispersant is both 110, and the rest is the same as embodiment 1.

[0094] Example 8

[0095] The difference between this embodiment and embodiment 1 is that R3 of the phenylalkyl acrylate structural unit in the second dispersant is ethyl, and the rest is the same as in embodiment 1.

[0096] Example 9

[0097] The difference between this embodiment and embodiment 1 is that R4 of the phenylalkyl acrylate structural unit in the second dispersant is an octyl group, and the rest is the same as in embodiment 1.

[0098] Example 10

[0099] The difference between this embodiment and embodiment 1 is that the value ranges of m, l and k in the second dispersant are all 5, and the rest are the same as embodiment 1.

[0100] Example 11

[0101] The difference between this embodiment and embodiment 1 is that the value ranges of m, l and k in the second dispersant are all 110, and the rest are the same as in embodiment 1.

[0102] Example 12

[0103] The difference between this embodiment and embodiment 1 is that the mass ratio of the first dispersant, the second dispersant and the third dispersant is 15:15:70, and the rest is the same as embodiment 1.

[0104] Example 13

[0105] The difference between this embodiment and embodiment 1 is that the mass ratio of the first dispersant, the second dispersant and the third dispersant is 80:15:5, and the rest is the same as embodiment 1.

[0106] Example 14

[0107] The difference between this embodiment and embodiment 1 is that the third dispersant is replaced with methyl phthalate of the same content, and the rest is the same as embodiment 1.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that the second dispersant is replaced by the first dispersant of the same content, and the rest is the same as Example 1.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that the third dispersant is replaced by the first dispersant of the same content, and the rest is the same as Example 1.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 1 is that the third dispersant is replaced by the second dispersant of the same content, and the rest are the same as Example 1.

[0114] Comparative Example 4

[0115] The difference between this comparative example and Example 1 is that the first dispersant is replaced with polyethylene oxide of the same content, and the rest is the same as Example 1.

[0116] Comparative Example 5

[0117] The difference between this comparative example and Example 1 is that the first dispersant is replaced with poly(phenyl alkyl acrylate) in an equal amount, and the rest is the same as Example 1.

[0118] Comparative Example 6

[0119] The difference between this comparative example and Example 1 is that the second dispersant is replaced by a diblock copolymer of acrylic acid and ethylene oxide in equal amounts, and the rest is the same as Example 1.

[0120] Application Examples 1 to 14 and Comparative Application Examples 1 to 6

[0121] The positive electrode material dispersant compositions provided in Examples 1 to 14 and Comparative Examples 1 to 6 were used to prepare positive electrode slurries, and then positive electrode sheets were prepared. The preparation method is as follows:

[0122] 1) Mixing polyvinylidene fluoride binder (model: Solvay 5130) and N-methylpyrrolidone solvent and stirring uniformly to obtain glue solution A;

[0123] 2) adding the cathode material dispersant composition of the present invention to the above-mentioned glue solution A and stirring uniformly to obtain glue solution B;

[0124] 3) Adding conductive carbon black to glue B to obtain conductive agent slurry;

[0125] 4) adding the ternary positive electrode material NCM811 (purchased from Bamo Technology Co., Ltd.) to the conductive agent slurry to obtain a positive electrode slurry;

[0126] 5) Scrape the positive electrode slurry onto one side of the aluminum foil and dry it to obtain a positive electrode sheet.

[0127] Test conditions

[0128] The positive electrode slurries and positive electrode sheets provided in Application Examples 1 to 14 and Comparative Application Examples 1 to 6 were tested. The test method is as follows:

[0129] (1) Viscosity of positive electrode slurry:

[0130] Reference standard: GB / T 10247-2008

[0131] Rotational viscometer, instrument model: Brookfield

[0132] No. 4 rotor, speed 15rpm~30rpm

[0133] Test temperature: 25℃

[0134] (2) The number of bending resistance of the positive electrode:

[0135] Hand-cut aluminum foil to a size of 12 cm × 30 cm, lay it flat on the glass plate, and fix it on all four sides;

[0136] Take appropriate slurry and use 400um scraper to evenly scrape and form a film;

[0137] Dry at 100℃ for 30min;

[0138] Remove, cut into strips (12cm x 2cm), fold in half, flatten, unfold 180° on a flat surface, and observe

[0139] Check whether there is cracking at the crease, and record it as one time;

[0140] Repeat the rolling and unfolding actions until cracks are observed and count them.

[0141] The test results are shown in Table 1:

[0142] Table 1

[0143] As can be seen from Table 1, the first dispersant and the second dispersant mainly play the role of reducing viscosity. Due to their different structures, they have a dispersing effect on the active main material, conductive material, etc. in the slurry, thereby reducing viscosity. Application Examples 4-5 are cases where the substituents are not optimized. The viscosity of the resulting slurry increases, and the flexibility of the prepared electrode deteriorates. Application Examples 6-7 are cases where the value ranges of n and p are not optimized. The viscosity of the resulting slurry increases, and the flexibility of the prepared electrode deteriorates. Application Examples 8-9 are cases where the substituents are not optimized. The viscosity of the resulting slurry increases, and the flexibility of the prepared electrode deteriorates. Application Examples 10-11 are cases where the value ranges of m, l, and k are not optimized. The viscosity of the resulting slurry increases, and the flexibility of the prepared electrode deteriorates.

[0144] Application Examples 12-13 and Comparative Application Examples 1, 4, 5 and 6 show that changes in the mass ratio or replacement of the types of the first dispersant and the second dispersant will affect the ability to control the viscosity of the slurry to a certain extent. Replacing the first dispersant or the second dispersant with a structure other than that of the present invention will reduce the dispersion performance of the slurry and increase the viscosity.

[0145] Comparative application examples 2-3 show that the third dispersant mainly plays a role in increasing flexibility, and its absence or unreasonable structure will affect the flexibility of the dry film.

[0146] In summary, the present invention reduces the viscosity of the slurry and increases the flexibility of the dry film by regulating the structure and mass ratio of the three dispersants.

[0147] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A cathode material dispersant composition, characterized in that: The positive electrode material dispersant composition comprises a combination of a first dispersant, a second dispersant and a third dispersant; The first dispersant is a diblock copolymer of phenylalkyl acrylate and ethylene oxide; The second dispersant is a triblock copolymer of phenylalkyl acrylate, acrylic acid and ethylene oxide; The third dispersant is an alkyl phthalate.

2. The cathode material dispersant composition according to claim 1, characterized in that The structural formula of the first dispersant is shown in Formula I: Wherein, R1 is selected from a C1-5 hydrocarbon group, R2 is selected from a C1-20 hydrocarbon group, and the value ranges of n and p are independently 1-500.

3. The cathode material dispersant composition according to claim 2, characterized in that: The structural formula of the first dispersant is shown in Formula I: Wherein, R1 is selected from methyl, R2 is selected from C1-5 hydrocarbon group, and the value range of n and p is independently 10-100.

4. The cathode material dispersant composition according to claim 1, characterized in that The structural formula of the second dispersant is shown in Formula II: Wherein, R3 is selected from a C1-5 hydrocarbon group, R4 is selected from a C1-20 hydrocarbon group, and the value ranges of m, l and k are each independently 1-500.

5. The cathode material dispersant composition according to claim 4, characterized in that: The structural formula of the second dispersant is shown in Formula II: Wherein, R3 is selected from methyl, R4 is selected from C1-5 hydrocarbon group, and the value ranges of m, l and k are independently 10-100.

6. The cathode material dispersant composition according to claim 1, characterized in that: The third dispersant includes alkyl phthalate and / or alkyl isophthalate; Preferably, the number of carbon atoms in the alkyl chain of the third dispersant is 4-20, preferably 5-8.

7. A method for preparing a cathode material dispersant composition according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: The first dispersant, the second dispersant and the third dispersant are mixed with an organic solvent to obtain the positive electrode material dispersant composition.

8. The method according to claim 7, characterized in that Taking the total mass of the first dispersant and the second dispersant as 100%, the mass ratio of the first dispersant to the second dispersant is (20-80):(80-20); Preferably, based on the total mass of the first dispersant, the second dispersant and the third dispersant being 100%, the total mass percentage of the first dispersant and the second dispersant is not less than 60%; Preferably, based on the total mass of the first dispersant, the second dispersant and the third dispersant being 100%, the mass percentage of the third dispersant is no more than 40%, preferably 5-30%; Preferably, the organic solvent comprises N-methylpyrrolidone; Preferably, the mixing further comprises rotary evaporation; Preferably, the temperature of the rotary evaporation treatment is 80° C. and the vacuum degree is less than -0.09 MPa.

9. A positive electrode slurry, characterized in that: The positive electrode slurry comprises a positive electrode active material, a conductive agent, a binder, a dispersant and a solvent, wherein the dispersant is a positive electrode material dispersant composition according to any one of claims 1 to 6; Preferably, the positive electrode active material comprises a ternary positive electrode material; Preferably, the mass ratio of the positive electrode active material, the conductive agent, the binder, the dispersant and the NMP solvent is (55-58):(1-3):(1-3):(0.1-0.8):(20-50).

10. A secondary battery, characterized in that: The secondary battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, and the positive electrode sheet is prepared from the positive electrode slurry according to claim 9.

Images