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

Abstract

The present invention provides a positive electrode material dispersant composition, a preparation method and an application thereof. 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 phenyl alkyl acrylate and ethylene oxide; the second dispersant is a triblock copolymer of phenyl alkyl acrylate, acrylic acid and ethylene oxide; the third dispersant is an alkyl phthalate. The positive electrode material dispersant composition provided by the present invention can not only solve the technical problem of increased viscosity of the ternary positive electrode slurry due to excessive surface adsorption of the conductive agent material during the processing of the ternary positive electrode slurry, but also solve the problem of gelation of the polyvinylidene fluoride binder in the alkaline system of the ternary positive electrode slurry and poor flexibility of the pole piece during the coating and drying process of the slurry.

Description

Technical Field

[0001] The present invention belongs to the technical field of dispersant materials, and in particular relates to a positive electrode material dispersant composition and a preparation method and application thereof. Background Art

[0002] 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 because of their advantages such as high theoretical specific capacity (up to 274mAh / g), high reaction platform voltage (3.0-4.4V) and low cost.

[0003] During the processing of the battery cell 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 content of nickel to replace the previously common NCM111 and NCM523 positive electrode materials. This causes the viscosity of the positive electrode slurry to increase during the processing, and the slurry changes over time, resulting in gelation, 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.

[0004] In response to the above problems, technicians in this field have conducted extensive research. The commercial lithium iron phosphate dispersants previously used could not meet the application requirements of processing battery cell systems using ternary positive electrode materials due to their narrow voltage window or matching problems.

[0005] 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 sheet while ensuring that the ternary positive electrode material slurry has a high solid content. Summary of the invention

[0006] In view of the deficiencies of the prior art, the object of the present invention is to provide a cathode material dispersant composition and a preparation method and application thereof. The cathode material dispersant composition provided by the present invention can not only solve the technical problem that the viscosity of the ternary cathode slurry increases due to excessive surface adsorption of the conductive agent material during the processing of the ternary cathode slurry, but also solve the problem that the polyvinylidene fluoride binder is gelled in the alkaline system of the ternary cathode slurry and the electrode sheet has poor flexibility during the coating and drying process of the slurry.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] 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;

[0009] The first dispersant is a diblock copolymer of phenylalkyl acrylate and ethylene oxide;

[0010] The second dispersant is a triblock copolymer of phenylalkyl acrylate, acrylic acid and ethylene oxide;

[0011] The third dispersant is an alkyl phthalate.

[0012] The present invention uses a first dispersant that is beneficial to the dispersion of the conductive agent, a second dispersant that assists in the dispersion, and a third dispersant that increases flexibility to prepare a positive electrode material dispersant composition. Among them, 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, so that it is adsorbed to the surface of the material. The solvated polyether segment can have a good affinity for the N-methylpyrrolidone solvent, and the steric hindrance effect it produces can prevent material aggregation;

[0013] 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 the function of dispersing the conductive material, and the working principle is the same as that of the first dispersant;

[0014] 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 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, ultimately improving the flexibility of the dry film.

[0015] In addition, the first dispersant acts as the surface adsorption 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 pH. If used alone, it cannot solve the gel problem and affects the effect of reducing the viscosity of the system.

[0016] 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.

[0017] Preferably, the structural formula of the first dispersant is as shown in Formula I:

[0018]

[0019] Among them, R 1 A hydrocarbon group selected from C1-5, R 2 The hydrocarbon group is selected from C1-20, and the value range of n and p is independently 1-500.

[0020] In the present invention, R 1 A hydrocarbon group selected from C1-5, such as R 1 It may be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0021] Furthermore, R 1 At least one selected from methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0022] In the present invention, R 2 A hydrocarbon group selected from C1-20, such as R 1 It may be at least one of a C1-20 alkyl group, a C2-20 alkenyl group, or a C2-20 alkynyl group.

[0023] Furthermore, R 2 At least one selected from methyl, ethyl, propyl, butyl, pentyl, decyl, vinyl, propenyl, butenyl, pentenyl, dodecenyl, octadecenyl, ethynyl, propynyl, butynyl, pentynyl, dodecynyl or octadecynyl.

[0024] 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.

[0025] In the present invention, by adjusting the value range of n and p, the dispersant molecule has a sufficient ratio of ester groups and benzene rings, which can form a good coordination adsorption effect with the surface of the granular material (especially conductive carbon black) in the ternary positive electrode slurry, and achieve the best adsorption effect. At the same time, the polyether molecular chain part has good NMP solvent affinity, which can make the surface of the granular material have good solution wettability and improve its dispersibility in the slurry.

[0026] Preferably, the structural formula of the first dispersant is as shown in Formula I:

[0027]

[0028] Among them, R 1 Selected from methyl, R 2 The hydrocarbon group is selected from C1-5, and the value range of n and p is independently 10-100.

[0029] In the present invention, R 2 A hydrocarbon group selected from C1-5, such as R 2 It may be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0030] Furthermore, R 2 At least one selected from methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0031] In the present invention, by further preferably R 1 and R 2 The type of group allows for appropriate free space between the benzene ring structure and the ester functional group, making it easier for the ester functional group to adsorb onto the surface of the ternary main material particles, thereby allowing the carbon-based conductive agent material to approach the surface of the main material particles, thus avoiding a decrease in conductive performance.

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

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

[0034]

[0035] Among them, R 3 A hydrocarbon group selected from C1-5, R 4 The hydrocarbon group is selected from C1-20, and the value range of m, l and k is independently 1-500.

[0036] In the present invention, R 3 A hydrocarbon group selected from C1-5, such as R 3 It may be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0037] Furthermore, R 3At least one selected from methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0038] In the present invention, R 4 A hydrocarbon group selected from C1-20, such as R 4 It may be at least one of a C1-20 alkyl group, a C2-20 alkenyl group, or a C2-20 alkynyl group.

[0039] Furthermore, R 4 At least one selected from methyl, ethyl, propyl, butyl, pentyl, decyl, vinyl, propenyl, butenyl, pentenyl, dodecenyl, octadecenyl, ethynyl, propynyl, butynyl, pentynyl, dodecynyl or octadecynyl.

[0040] 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.

[0041] In the present invention, by adjusting the value range of m, l and k, a certain proportion of benzoic acid groups is contained in the dispersant molecule, which can reduce the alkalinity of the ternary positive electrode 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.

[0042] Preferably, the structural formula of the second dispersant is as shown in Formula II:

[0043]

[0044] Among them, R 3 Selected from methyl, R 4 The hydrocarbon group is selected from C1-5, and the value range of m, l and k is independently 10-100.

[0045] In the present invention, R 4 A hydrocarbon group selected from C1-5, such as R 4 It may be at least one of a C1-5 alkyl group, a C2-5 alkenyl group or a C2-5 alkynyl group.

[0046] Furthermore, R 4 At least one selected from methyl, ethyl, propyl, butyl, pentyl, vinyl, propenyl, butenyl, pentenyl, ethynyl, propynyl, butynyl or pentynyl.

[0047] In the present invention, by further preferably R 3 and R 4 The type of group allows for appropriate free space between the benzene ring structure and the ester functional group, making it easier for the ester functional group to adsorb onto the surface of the ternary main material particles, thereby allowing the carbon-based conductive agent material to approach the surface of the main material particles, thus avoiding a decrease in conductive performance.

[0048] 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.

[0049] Preferably, the third dispersant comprises alkyl phthalate and / or alkyl isophthalate.

[0050] 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.

[0051] In the present invention, by regulating the number of carbon atoms in the alkyl chain in the third dispersant, the alkyl chain forms sufficient space hindrance on the surface of polyvinylidene fluoride, thereby 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, thereby 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 resulting in breakage.

[0052] 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:

[0053] The first dispersant, the second dispersant and the third dispersant are mixed with an organic solvent to obtain the positive electrode material dispersant composition.

[0054] 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.

[0055] Preferably, taking 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.

[0056] 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, 5%, 8%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40% and the like.

[0057] In the present invention, by adjusting the mass ratio of the first dispersant, the second dispersant and the third dispersant, the dispersant has both the function of 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, otherwise it will affect the flexibility of the electrode.

[0058] Preferably, the organic solvent comprises N-methylpyrrolidone.

[0059] Preferably, the mixing further includes rotary evaporation.

[0060] 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.

[0061] 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.

[0062] Preferably, the positive electrode active material includes a ternary positive electrode material.

[0063] 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.

[0064] 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), 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.

[0065] Preferably, the present invention provides a method for preparing a positive electrode slurry, which comprises the following steps:

[0066] 1) Mixing and stirring the binder and the solvent to obtain glue solution A;

[0067] 2) adding the cathode material dispersant composition of the present invention to the above-mentioned glue solution A and stirring evenly to obtain glue solution B;

[0068] 3) Adding the conductive agent to the glue solution B to obtain a conductive agent slurry;

[0069] 4) Adding the positive electrode active material into the conductive agent slurry to obtain a positive electrode slurry.

[0070] 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.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] The present invention provides a cathode material dispersant composition, which can not only improve the dispersibility of the slurry, but also reduce the viscosity of the slurry to within the processable range of 7000-8000 mPa·s after using the dispersant provided by the present invention, compared with a slurry system with a solid content of more than 70% (the viscosity of the slurry is more than 18000 mPa·s);

[0073] 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 generating gel (the same slurry system without adding the positive electrode material dispersant composition has a gelation time of less than 3 hours);

[0074] 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

[0075] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0076] Example 1

[0077] 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 alkyl 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 alkyl 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).

[0078]

[0079] This embodiment also provides a method for preparing the above-mentioned positive electrode material dispersant composition, which comprises the following steps:

[0080] 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 positive electrode material dispersant composition was obtained after rotary evaporation at 80° C. and a vacuum degree of −0.06 MPa.

[0081] Example 3

[0082] 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 alkyl acrylate (purchased from Wuhan Kemik Company) and ethylene oxide (Merck Supelco standard product, CAS No. 75-21-8) as shown in Formula I; the second dispersant is a triblock copolymer of ethyl acrylate, acrylic acid (Merck Sigma-Aldrich, CAS No. 79-10-7) and ethylene oxide (Merck Supelco standard product, CAS No. 75-21-8) as shown in Formula II; the third dispersant is amyl phthalate (American Alfa, CAS No. 131-18-0).

[0083]

[0084]

[0085] This embodiment also provides a method for preparing the above-mentioned positive electrode material dispersant composition, which comprises the following steps:

[0086] 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 positive electrode material dispersant composition was obtained after rotary evaporation at 80° C. and a vacuum degree of −0.06 MPa.

[0087] Example 4

[0088] The difference between this embodiment and embodiment 1 is that the R 2 The other elements are the same as those in Example 1.

[0089] Example 5

[0090] The difference between this embodiment and embodiment 1 is that the R 2 is octyl, and the others are the same as in Example 1.

[0091] Example 6

[0092] The difference between this embodiment and embodiment 1 is that the value range of n and p in the first dispersant is 5, and the rest is the same as embodiment 1.

[0093] Example 7

[0094] The difference between this embodiment and embodiment 1 is that the value ranges of n and p in the first dispersant are both 110, and the rest are the same as embodiment 1.

[0095] Example 8

[0096] The difference between this embodiment and embodiment 1 is that the R 3 The other elements are the same as those in Example 1.

[0097] Example 9

[0098] The difference between this embodiment and embodiment 1 is that the R 4 is octyl, and the others are the same as in Example 1.

[0099] Example 10

[0100] 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.

[0101] Embodiment 11

[0102] 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 embodiment 1.

[0103] Example 12

[0104] 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.

[0105] Embodiment 13

[0106] 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.

[0107] Embodiment 14

[0108] 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.

[0109] Comparative Example 1

[0110] 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.

[0111] Comparative Example 2

[0112] 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.

[0113] Comparative Example 3

[0114] 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 is the same as Example 1.

[0115] Comparative Example 4

[0116] 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.

[0117] Comparative Example 5

[0118] The difference between this comparative example and Example 1 is that the first dispersant is replaced with poly(phenyl alkyl acrylate) in an equal content, and the rest is the same as Example 1.

[0119] Comparative Example 6

[0120] 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.

[0121] Application Examples 1 to 14 and Comparative Application Examples 1 to 6

[0122] The positive electrode material dispersant compositions provided in Examples 1 to 14 and Comparative Examples 1 to 6 are used to prepare positive electrode slurries, and then positive electrode sheets are prepared. The preparation method is as follows:

[0123] 1) Mix and stir polyvinylidene fluoride binder (model: Solvay 5130) and N-methylpyrrolidone solvent to obtain glue solution A;

[0124] 2) adding the cathode material dispersant composition of the present invention to the above-mentioned glue solution A and stirring evenly to obtain glue solution B;

[0125] 3) Adding conductive carbon black to glue solution B to obtain conductive agent slurry;

[0126] 4) adding the ternary positive electrode material NCM811 (purchased from Bamo Technology Co., Ltd.) into the conductive agent slurry to obtain a positive electrode slurry;

[0127] 5) Scrape the positive electrode slurry onto one side of the aluminum foil and dry it to obtain a positive electrode sheet.

[0128] Test conditions

[0129] The positive electrode slurries and positive electrode sheets provided in Application Examples 1 to 14 and Comparative Application Examples 1 to 6 were tested, and the test method was as follows:

[0130] (1) Viscosity of positive electrode slurry:

[0131] Reference standard: GB / T 10247-2008

[0132] Rotational viscometer, instrument model: Bolefei

[0133] No. 4 rotor, speed 15rpm~30rpm

[0134] Test temperature: 25℃

[0135] (2) The number of bending resistance of the positive electrode:

[0136] Hand-cut aluminum foil to a size of 12 cm × 30 cm, lay it flat on the glass plate and fix it on the four sides;

[0137] Take appropriate slurry and use 400um scraper to evenly scrape and form a film;

[0138] Dry at 100℃ for 30min;

[0139] Take it off, cut it into strips (12cm×2cm), fold it in half, flatten it, unfold it 180° on the flat surface, and observe whether there is cracking at the fold, which is counted as one time;

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

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

[0142] Table 1

[0143]

[0144]

[0145] 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 the viscosity. Application Examples 4-5 are cases where the substituents are not preferred, and 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 preferred, and 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 preferred, and 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 preferred, and the viscosity of the resulting slurry increases, and the flexibility of the prepared electrode deteriorates.

[0146] Application Examples 12-13 and Comparative Application Examples 1, 4, 5 and 6 show that the change in the mass ratio or the replacement of the types between 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.

[0147] 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.

[0148] 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.

[0149] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope 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; The structural formula of the first dispersant is shown in Formula I: Wherein, R1 is selected from methyl, R2 is selected from methylene, and the value range of n and p is independently 15-25; The structural formula of the second dispersant is shown in Formula II: Wherein, R3 is selected from methyl, R4 is selected from methylene, and the value ranges of m, l and k are each independently 15-20; The third dispersant includes alkyl phthalate and / or alkyl isophthalate, and the number of carbon atoms in the alkyl chain of the third dispersant is 5-8; 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); Taking 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%; Taking the total mass of the first dispersant, the second dispersant and the third dispersant as 100%, the mass percentage of the third dispersant is 10-30%.

2. A method for preparing the positive electrode material dispersant composition according to claim 1, 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.

3. The method according to claim 2, characterized in that The organic solvent includes N-methylpyrrolidone.

4. The method according to claim 2, characterized in that: The mixing further includes rotary evaporation.

5. The method according to claim 4, characterized in that The temperature of the rotary evaporation treatment is 80° C., and the vacuum degree is less than -0.09 MPa.

6. 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, and the dispersant is the positive electrode material dispersant composition according to claim 1.

7. The positive electrode slurry according to claim 6, characterized in that: The positive electrode active material includes a ternary positive electrode material.

8. The positive electrode slurry according to claim 6, characterized in that: 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).

9. 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 any one of claims 6 to 8.

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