Positive dispersing agent, positive slurry containing positive dispersing agent, positive pole piece and secondary battery

Abstract

The invention discloses a positive dispersing agent, positive slurry containing the positive dispersing agent, a positive pole piece and a secondary battery. The positive electrode dispersant comprises a component A, a component B and a component C; the component A is an acrylate dispersing agent and / or a polyvinylpyrrolidone dispersing agent; the component B comprises a compound as shown in a formula I; and the component C is one or more of hydroximic acid and hydroximic acid ester. When the positive electrode dispersing agent provided by the invention is applied to preparation of positive electrode slurry, especially in the presence of carboxyl modified PVDF and / or a positive electrode lithium supplement agent, the viscosity of the slurry can be effectively reduced, and the stability of the slurry is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a positive electrode dispersant, a positive electrode slurry containing the same, a positive electrode sheet, and a secondary battery. BACKGROUND

[0002] The current lithium battery technology is continuously developing towards high performance and high energy density, and the current mainstream development direction includes two aspects. One is to use carboxyl modified polyvinylidene fluoride (PVDF) to replace the traditional PVDF. The carboxyl modified PVDF has higher adhesion, can use less additive amount, and can increase the proportion of the main material to improve the energy density. The other is to add a lithium supplement. By adding a positive electrode lithium supplement material, the energy density and cycle life of the battery are improved.

[0003] However, whether it is carboxyl modified PVDF or a positive electrode lithium supplement, it will cause the viscosity rebound to increase or even gel during the preparation of the slurry. The existing dispersants, such as acrylate dispersants, PVP or polyether phosphate, have little effect on improving the gel. There is a lack of positive electrode slurry dispersants that can adapt to the carboxyl modified PVDF and positive electrode lithium supplement system in the market, so that the viscosity is low and the stability is good during the preparation of the slurry. SUMMARY

[0004] The present application mainly aims to overcome the defects of slurry gel and viscosity rebound caused by the addition of carboxyl modified PVDF and / or positive electrode lithium supplement when improving the energy density of lithium batteries in the prior art, and provides a positive electrode dispersant, a positive electrode slurry containing the same, a positive electrode sheet and a secondary battery. The positive electrode dispersant provided by the present application can effectively reduce the viscosity of the slurry and improve the stability of the slurry when applied to the preparation of the electrode slurry in the presence of carboxyl modified PVDF and / or positive electrode lithium supplement.

[0005] In a first aspect, the present application provides a positive electrode dispersant comprising component A, component B and component C;

[0006] The component A is an acrylate dispersant and / or a polyvinylpyrrolidone dispersant;

[0007] The component B comprises a compound represented by Formula I:

[0008] Formula I;

[0009] In Formula I, R1, R2 and R3 are each independently selected from C2-C12 linear alkyl, C4-C12 branched alkyl, -OH, -OR4 and any one of the following groups:

[0010] Wherein, R1, R2 and R3 are not simultaneously -OH; R4 is any one of C2-C12 linear alkyl, C4-C12 branched alkyl and alkyl-substituted aromatic group; R5 is any one of C1-C12 linear alkyl, C4-C14 branched alkyl and alkyl-substituted aromatic group; n is any integer from 0 to 40, m is any integer from 0 to 40, and n+m≥3;

[0011] The component C is one or more of hydroxamic acid and hydroxamic acid ester.

[0012] In the present application, the mass ratio of the component A to the component B can be 1:(0.1-9), preferably 1:(0.5-9), more preferably 1:(1-9), for example 1:1, 1:1.5, 1:2, 1:2.33, 1:3, 1:4 or 1:9.

[0013] In the present application, the amount of the component C accounts for 4%-50% of the total mass of the component A and the component B, preferably 10%-50%, for example 10%, 20%, 40% or 50%.

[0014] In the present application, the pH of the positive electrode dispersant diluted with water at a volume ratio of 1:9 is 1-6.

[0015] In the present application, the acrylate dispersant refers to the solid component of the dispersant commonly used in the art without solvent.

[0016] In the present application, the polyvinylpyrrolidone dispersant refers to the solid component of the dispersant commonly used in the art without solvent.

[0017] In the present application, the acrylate dispersant can comprise polyacrylate, preferably the solid component of LIB-D300 of Shanghai Sanshuigao Polymer Material Co., Ltd.; the weight average molecular weight of the polyacrylate is preferably 20000-60000.

[0018] In the present application, the acrylate dispersant can comprise polyacrylate terpolymer, which is polymerized from monomer I, monomer II and monomer III; the monomer I is acrylic acid and / or methacrylic acid; the monomer II is acrylate, for example polyethylene glycol monomethyl ether methacrylate and / or alkyl methacrylate; the monomer III is vinylpyrrolidone.

[0019] Wherein, based on the total mass of the polyacrylate terpolymer as 100%, the mass percentage of the structural unit formed by monomer I is preferably 5%-15%; the mass percentage of the structural unit formed by monomer II is preferably 20%-40%; and the mass percentage of the structural unit formed by monomer III is preferably 45%-75%.

[0020] Preferably, the polyacrylate terpolymer is a terpolymer of acrylic acid, polyethylene glycol monomethyl ether methacrylate, and vinylpyrrolidone, wherein the mass percentage of the structural units formed by acrylic acid is 10%, the mass percentage of the structural units formed by polyethylene glycol monomethyl ether methacrylate is 20%, and the mass percentage of the structural units formed by vinylpyrrolidone is 70%.

[0021] Preferably, the molecular weight of the polyacrylate terpolymer is 20,000-80,000, for example 40,000.

[0022] In this invention, the K value of polyvinylpyrrolidone in the polyvinylpyrrolidone dispersant can be 12-90, for example, one or more of PVP K12, PVP K15, PVP K17, PVP 25, PVP K30, PVP K60, and PVP K90. The K value is a characteristic value related to the relative viscosity of the PVP aqueous solution and is used to characterize the average molecular weight of PVP.

[0023] In some specific embodiments, R1, R2 and R3 are each independently selected from C2-C8 straight-chain alkyl groups and / or C4-C8 branched alkyl groups.

[0024] In some specific embodiments, R1, R2 and R3 are each independently selected from -OH, C6-C12 straight-chain alkyl and C6-C12 branched alkyl, at least one of R1, R2 and R3 is selected from -OH, and R1, R2 and R3 are not all -OH at the same time.

[0025] In some specific embodiments, R1, R2 and R3 are each independently selected from -OH and C2-C8 alkoxy groups, and R1, R2 and R3 are not simultaneously -OH.

[0026] In some specific implementations, R1, R2, and R3 are each independently selected from -OH and / or Where m is 0, n is 5-20, R5 is a C8-C13 branched alkyl group; two of R1, R2 and R3 are selected from -OH.

[0027] In some specific implementations, R1, R2, and R3 are each independently selected from -OH and / or Where n is 0, m is 5-20, R5 is a C8-C13 branched alkyl group; two of R1, R2 and R3 are selected from -OH.

[0028] In some specific implementations, R1, R2, and R3 are each independently selected from -OH and / or Where m is 0, n is 5-20, R5 is a C6-C10 alkyl-substituted phenyl group; two of R1, R2 and R3 are selected from -OH.

[0029] In some specific embodiments, the compound represented by Formula I is one or more selected from trialkylphosphine oxide, alkyl phosphate, alkyl phosphate ester and polyether phosphate ester; each alkyl group in the trialkylphosphine oxide has 2-8 carbon atoms; each alkyl group in the alkyl phosphate has 2-12 carbon atoms; each alkyl group in the alkyl phosphate ester has 2-8 carbon atoms.

[0030] Preferably, the trialkylphosphine oxide includes one or more of triethylphosphine oxide, triisopropylphosphine oxide, tri-n-butylphosphine oxide, tri-n-octylphosphine oxide, and hexyldioctylphosphine oxide.

[0031] Preferably, the alkyl phosphate ester includes one or more of diethyl phosphate, triethyl phosphate, tripropyl phosphate, butyl phosphate, tributyl phosphate, di(2-ethylhexyl) phosphate, trioctyl phosphate, and 2-ethylhexylphosphonate mono-2-ethylhexyl ester.

[0032] Preferably, the alkyl phosphoric acid includes n-octyl phosphoric acid and / or dodecyl phosphoric acid.

[0033] Preferably, the polyether phosphate includes one or more of the following: methoxy polyethylene glycol phosphate, polyethylene glycol monomethyl ether phosphate, fatty alcohol polyoxyethylene ether phosphate, fatty alcohol polyoxypropylene ether phosphate, fatty alcohol polyoxyethylene polyoxypropylene ether phosphate, nonylphenol polyoxyethylene ether phosphate, octylphenol polyoxyethylene ether phosphate, and phenol polyoxyethylene ether phosphate.

[0034] The fatty alcohol polyoxypropylene ether phosphate may optionally be butanol polyoxypropylene ether phosphate;

[0035] The fatty alcohol polyoxyethylene ether phosphate may optionally be isomeric tridecyl alcohol polyoxypropylene ether phosphate.

[0036] In this invention, the hydroxamic acid may be one or more of acetyloxyxamic acid, octyloxyxamic acid, salicylic acid, octyl diisohydroxamic acid, benzooxyxamic acid, L-aspartic acid β-hydroxamic acid, D-aspartic acid β-hydroxamic acid, and 1-naphthohydroxyxamic acid.

[0037] In this invention, the hydroxamic ester may be ethyl acetyl hydroxamic acid and / or DL-serine isohydroxamic ester.

[0038] In this invention, the positive electrode dispersant may further include an organic solvent, which may be N-methylpyrrolidone (NMP).

[0039] In some specific embodiments, component A is an acrylate dispersant, component B is butanol polyoxypropylene ether phosphate, and component C is octanoyl oxyxamic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.33. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 40%.

[0040] In some specific embodiments, component A is an acrylate dispersant, component B is tri-n-octylphosphine oxide, and component C is acetoxyxamic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:1. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 10%.

[0041] In some specific embodiments, component A is a polyvinylpyrrolidone dispersant, component B is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, and component C is octanoyloxyoxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:1.5. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 20%.

[0042] In some specific embodiments, component A is a polyvinylpyrrolidone dispersant, component B is n-octylphosphate, and component C is ethyl acetylhydroxamic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.33. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 20%.

[0043] In some specific embodiments, component A is a polyvinylpyrrolidone dispersant, component B is polyethylene glycol monomethyl ether phosphate, and component C is salicylic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:4. Preferably, the mass of component C accounts for 20%-50% of the total mass of components A and component B, for example, 50%.

[0044] In some specific embodiments, component A is an acrylate dispersant, component B is isotridecyl polyoxyethylene ether phosphate, and component C is octanoyl oxyxamic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:4. Preferably, the mass of component C accounts for 20%-40% of the total mass of component A and component B, for example, 40%.

[0045] In some specific embodiments, component A is an acrylate dispersant, component B is butanol polyoxyethylene polyoxypropylene ether phosphate, and component C is octanoyl oxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:-2.33. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 40%.

[0046] In some specific embodiments, component A is an acrylate dispersant, component B is octylphenol polyoxyethylene ether phosphate, and component C is octyloxyoxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.33. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 40%.

[0047] In some specific embodiments, component A is an acrylate dispersant, component B is di(2-ethylhexyl) phosphate and tributyl phosphate, and component C is octanoyl oxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.33. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 50%.

[0048] Secondly, the present invention provides a positive electrode slurry comprising a positive electrode active material, a binder, and a positive electrode dispersant as described above.

[0049] In this invention, the positive electrode active material may be a lithium iron phosphate material, such as lithium iron phosphate and / or carbon-coated lithium iron phosphate.

[0050] In this invention, the binder in the positive electrode slurry is polyvinylidene fluoride (PVDF) and / or carboxyl-modified polyvinylidene fluoride.

[0051] In this invention, the positive electrode dispersant preferably accounts for 0.1%-0.5% of the total solid mass of the positive electrode slurry, for example, 0.2%.

[0052] In this invention, the positive electrode slurry contains, based on a total solid mass of 100%, a positive electrode active material that preferably accounts for 93%-98% of the total mass, for example, 95.8% or 97.4%.

[0053] In this invention, the binder accounts for 1%-3% of the total solid mass of the positive electrode slurry, for example, 1.7% or 1.8%.

[0054] In this invention, the positive electrode slurry further includes a conductive agent and / or a positive electrode lithium replenishing agent.

[0055] The conductive agent is preferably conductive carbon black and / or carbon nanotubes.

[0056] The conductive agent preferably accounts for 0.7%-4% of the total solid mass, for example, 0.7%, based on 100% of the total solid mass.

[0057] The positive electrode lithium replenishing agent is preferably lithium iron ferrite and / or lithium nickel ferrite, such as Li5FeO4;

[0058] Specifically, based on 100% of the total solid mass, the mass percentage of the positive electrode lithium replenishing agent is preferably 0%-3%, but not 0, for example, 1.5%;

[0059] When the binder is PVDF, the mass percentage of the positive electrode lithium replenishing agent is preferably 0.5%-3% based on 100% of the total solid mass.

[0060] In some specific embodiments, the positive electrode slurry includes positive electrode active material, conductive agent, binder and dispersant as described above, with the positive electrode active material accounting for 93%-98%, the conductive agent accounting for 0.7%-4%, the binder accounting for 1%-3%, the positive electrode lithium supplement agent accounting for 0%-3%, and the positive electrode dispersant as described above accounting for 0.1%-0.5% based on 100% solid content.

[0061] Thirdly, the present invention provides a positive electrode sheet, which is made using the aforementioned positive electrode slurry.

[0062] Fourthly, the present invention provides a secondary battery comprising the positive electrode sheet as described above.

[0063] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0064] The reagents and raw materials used in this invention are all commercially available.

[0065] The positive and progressive effects of this invention are as follows:

[0066] The positive electrode dispersant provided by this invention, when applied to positive electrode slurry, can effectively reduce slurry viscosity and improve slurry stability under high solid content conditions.

[0067] In some preferred embodiments where a positive electrode lithium supplementer is added, when the slurry solid content is 67%-68%, the slurry viscosity at discharge is less than 7500 mPa·s, and the slurry viscosity after standing for 24 hours is less than 21000 mPa·s.

[0068] In some preferred embodiments of PVDF with added carboxyl groups, when the slurry solid content is 65%, the slurry viscosity at discharge is less than 8000 mPa·s, and the slurry viscosity after standing for 24 hours is less than 21000 mPa·s. Detailed Implementation

[0069] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0070] The LIB-D300 used in the following examples and comparative examples is an acrylate dispersant solution purchased from Shanghai Sanrui Polymer Materials Co., Ltd., and its solid component is an acrylate dispersant with a solid content of 25%.

[0071] Acrylic ester dispersant solution D1 refers to a polyacrylate terpolymer solution consisting of acrylic acid (10% by mass), polyethylene glycol monomethyl ether methacrylate (20% by mass), and vinylpyrrolidone (70% by mass), with NMP as the solvent. The polyacrylate terpolymer has a weight-average molecular weight of 40,000 and a solid content of 50%.

[0072] PVP K17, K25 and K30 were purchased from Boai New Open Source Medical Technology Group Co., Ltd.

[0073] Butanol polyoxypropylene ether 500 phosphate is obtained by phosphating butanol polyoxypropylene ether with a molecular weight of about 500.

[0074] Polyethylene glycol monomethyl ether 600 phosphate refers to polyethylene glycol monomethyl ether with a molecular weight of approximately 600 obtained by phosphating.

[0075] Butanol polyoxyethylene polyoxypropylene ether 1000 phosphate refers to butanol polyoxyethylene polyoxypropylene ether with a molecular weight of approximately 1000 obtained by phosphating.

[0076] In isotridecyl alcohol polyoxyethylene 07 ether phosphate, 07 represents that the number of EO repeating units in the polyoxyethylene is 7.

[0077] In octylphenol polyoxyethylene 06 ether phosphate, 06 represents the number of repeating units of EO in the polyoxyethylene, which is 6.

[0078] Examples 1-9 and Comparative Examples 1-6

[0079] Preparation of dispersants

[0080] Mix the components according to the formula in Table 1 to prepare the dispersant, denoted as M1-M15. The solution mass in Table 1 refers to the total mass of the acrylate dispersant or polyvinylpyrrolidone dispersant and the solvent.

[0081] Examples 10-18 and Comparative Examples 7-14

[0082] Preparation of positive electrode slurry

[0083] The dispersants prepared in Examples 1-9 and Comparative Examples 1-6 were mixed with the positive electrode active material, binder, conductive agent and positive electrode lithium supplementer according to the formula in Table 2 (based on 100% of the total solid mass). The mixture was then homogenized using a dual planetary homogenizer to prepare a slurry. The solid content of the slurry was adjusted by adding NMP. The adjusted solid content of the slurry was recorded as the discharge solid content. The specific values ​​are recorded in Tables 3 and 4. The positive electrode slurry was thus prepared.

[0084] Table 1

[0085]

[0086] Table 2

[0087]

[0088] Effect Example

[0089] The cathode slurries prepared in Examples 10-18 and Comparative Examples 7-14 were tested for viscosity using a digital rotational viscometer. The viscosity of the freshly prepared cathode slurry was recorded as the discharge viscosity. The test environment temperature was 25°C and the ambient humidity was less than 80%. The cathode slurry was then placed in an environment at 25°C for 24 hours, and the viscosity was tested again and recorded as the 24-hour viscosity. The solid content, discharge viscosity, and 24-hour viscosity test results of each slurry are recorded in Tables 3 and 4.

[0090] Table 3

[0091]

[0092] As can be seen from the effect data in Table 3, for the slurry system with added positive electrode lithium supplement, the dispersant provided by the present invention can effectively improve the viscosity of the slurry under high solid content, significantly reduce the viscosity of the slurry, and significantly improve the viscosity rebound of the slurry after 24 hours, thus solving the problem of slurry gelation.

[0093] In Comparative Example 7, component A was used alone as a dispersant; in Comparative Example 8, component B was used alone as a dispersant; and in Comparative Example 9, component C was used alone as a dispersant. None of these methods could solve the gelation problem that occurred in the slurry with added positive electrode lithium supplement.

[0094] The dispersant used in Comparative Example 10, which only lacked component C, could not solve the gelation problem; the dispersant used in Comparative Example 11, which only lacked component B, could improve the viscosity rebound of the slurry, but could not completely solve the gelation problem; the dispersant used in Comparative Example 12, which only lacked component A, improved the viscosity rebound and increased the stability of the slurry, but the slurry's ability to increase solids content was insufficient.

[0095] This may be due to the synergistic effect of components A, B, and C. Component A mainly provides better solids content and acidity, and has the best dispersibility. Component B is the main acidic or neutral dispersant. Acidic dispersants can improve the gelation of carboxyl-modified PVDF and lithium supplementation systems. However, component B alone cannot completely solve the gelation problem. Component C alone has insufficient dispersibility and needs to be combined with A and B to solve the gelation problem. Component C is an additive with dispersing and stabilizing properties. In the carboxyl-modified PVDF system, its hydroxamic acid functional group can complex with the iron element of lithium iron phosphate to form a strong anchoring effect, which can reduce the aggregation of lithium iron phosphate and help improve viscosity rebound. In the positive electrode lithium supplementation system, hydroxamic acid is an acidic compound, which can neutralize part of the alkalinity and play a good stabilizing role. It is a key additive to improve stability.

[0096] Table 4

[0097]

[0098] As can be seen from the effect data in Table 4, for the slurry system with added carboxyl-modified PVDF, the dispersant provided by this invention can effectively improve the viscosity of the slurry under high solid content, significantly reduce the viscosity of the slurry, and significantly improve the viscosity rebound of the slurry after 24 hours, thus solving the problem of slurry gelation.

[0099] As can be seen from the results in Table 4, the dispersant provided by the present invention has better dispersing ability, higher slurry solid content, less viscosity rebound after 24 hours, and more stable slurry in the modified PVDF system compared with Comparative Examples 13 and 14. It can solve the slurry gelation problem and has obvious advantages.

[0100] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A positive electrode dispersant, characterized in that, It includes component A, component B, and component C; Component A is an acrylate dispersant and / or a polyvinylpyrrolidone dispersant; Component B includes the compound represented by Formula I: Equation I; In Formula I, R1, R2, and R3 are each independently selected from C2-C12 straight-chain alkyl groups, C4-C12 branched alkyl groups, -OH, -OR4, and... any one of them; Wherein, R1, R2, and R3 are not simultaneously -OH; R4 is any one of C2-C12 straight-chain alkyl, C4-C12 branched alkyl, and alkyl-substituted aromatic group; R5 is any one of C1-C12 straight-chain alkyl, C4-C14 branched alkyl, and alkyl-substituted aromatic group; n is any integer from 0 to 40, m is any integer from 0 to 40, and n+m≥3; Component C is one or more of hydroxamic acid and hydroxamic ester.

2. The positive electrode dispersant according to claim 1, characterized in that, The mass ratio of component A to component B is 1:(0.5-9), preferably 1:(1-9), for example 1:1, 1:1.5, 1:2.33, 1:3, 1:4 or 1:9; And / or, the mass percentage of component C to the total mass of components A and B is 4%-50%, preferably 10%-50%, for example 10%, 20%, 40% or 50%; And / or, the pH of the solution obtained by diluting the positive electrode dispersant with water at a volume ratio of 1:9 is 1-6.

3. The positive electrode dispersant according to claim 1, characterized in that, The compounds represented by Formula 1 satisfy one or more of the following conditions: a. R1, R2 and R3 are each independently selected from C2-C8 straight-chain alkyl groups and / or C4-C8 branched-chain alkyl groups; b. R1, R2 and R3 are each independently selected from -OH, C6-C12 straight-chain alkyl and C6-C12 branched alkyl, at least one of R1, R2 and R3 is selected from -OH, and R1, R2 and R3 are not simultaneously -OH; c. R1, R2, and R3 are each independently selected from -OH and C2-C8 alkoxy groups, and R1, R2, and R3 are not simultaneously -OH; d. R1, R2, and R3 are each independently selected from -OH and / or Where m is 0, n is 5-20, R5 is a C8-C13 branched alkyl group; two of R1, R2 and R3 are selected from -OH; e. R1, R2, and R3 are each independently selected from -OH and / or Where n is 0, m is 5-20, R5 is a C8-C13 branched alkyl group; two of R1, R2 and R3 are selected from -OH; f. R1, R2, and R3 are each independently selected from -OH and / or Where m is 0, n is 5-20, R5 is a C6-C10 alkyl-substituted phenyl; two of R1, R2 and R3 are selected from -OH; Preferably, the compound represented by Formula I is one or more selected from trialkylphosphine oxide, alkyl phosphate, alkyl phosphate ester and polyether phosphate ester; each alkyl group in the trialkylphosphine oxide has 2-8 carbon atoms; each alkyl group in the alkyl phosphate has 2-12 carbon atoms; each alkyl group in the alkyl phosphate ester has 2-8 carbon atoms. More preferably, the trialkylphosphine oxide comprises one or more of triethylphosphine oxide, triisopropylphosphine oxide, tri-n-butylphosphine oxide, tri-n-octylphosphine oxide, and hexyldioctylphosphine oxide; More preferably, the alkyl phosphate includes one or more of diethyl phosphate, triethyl phosphate, tripropyl phosphate, butyl phosphate, tributyl phosphate, di(2-ethylhexyl) phosphate, trioctyl phosphate, and 2-ethylhexylphosphonate mono-2-ethylhexyl ester. More preferably, the alkyl phosphoric acid includes n-octyl phosphoric acid and / or dodecyl phosphoric acid; More preferably, the polyether phosphate includes one or more of methoxy polyethylene glycol phosphate, polyethylene glycol monomethyl ether phosphate, fatty alcohol polyoxyethylene ether phosphate, fatty alcohol polyoxypropylene ether phosphate, fatty alcohol polyoxyethylene polyoxypropylene ether phosphate, nonylphenol polyoxyethylene ether phosphate, octylphenol polyoxyethylene ether phosphate, and phenol polyoxyethylene ether phosphate; the fatty alcohol polyoxypropylene ether phosphate may optionally be butanol polyoxypropylene ether phosphate; the fatty alcohol polyoxyethylene ether phosphate may optionally be isotridecyl alcohol polyoxypropylene ether phosphate.

4. The positive electrode dispersant according to claim 1, characterized in that, The hydroxamic acid is one or more of acetyloxyxamic acid, octyloxyxamic acid, salicylic acid, octyl diisohydroxamic acid, benzooxyxamic acid, L-aspartic acid β-hydroxamic acid, D-aspartic acid β-hydroxamic acid, and 1-naphthohydroxyxamic acid; And / or, the hydroxamic ester is ethyl acetyl hydroxamic acid and / or DL-serine isohydroxamic ester; And / or, the positive electrode dispersant further includes an organic solvent, wherein the organic solvent is N-methylpyrrolidone.

5. The positive electrode dispersant according to claim 1, characterized in that, The acrylate dispersant comprises polyacrylate, preferably the solid component of LIB-D300 from Shanghai Sanrui Polymer Materials Co., Ltd.; the weight-average molecular weight of the polyacrylate is preferably 20,000-60,000. And / or, the acrylate dispersant comprises a polyacrylate terpolymer, wherein the polyacrylate terpolymer is formed by polymerization of monomer I, monomer II and monomer III, wherein monomer I is acrylic acid and / or methacrylic acid; monomer II is an acrylate, such as polyethylene glycol monomethyl ether methacrylate and / or alkyl methacrylate; and monomer III is vinylpyrrolidone. Wherein, based on the total mass of the polyacrylate terpolymer as 100%, the mass percentage of the structural unit formed by monomer I is preferably 5%-15%; the mass percentage of the structural unit formed by monomer II is preferably 20%-40%; and the mass percentage of the structural unit formed by monomer III is preferably 45%-75%. Preferably, the polyacrylate terpolymer is a terpolymer of acrylic acid, polyethylene glycol monomethyl ether methacrylate, and vinylpyrrolidone, wherein the mass percentage of the structural units formed by acrylic acid is 10%, the mass percentage of the structural units formed by polyethylene glycol monomethyl ether methacrylate is 20%, and the mass percentage of the structural units formed by vinylpyrrolidone is 70%. Preferably, the molecular weight of the polyacrylate terpolymer is 20,000-80,000, for example 40,000; And / or, the polyvinylpyrrolidone dispersant has a K value of 12-90, such as one or more of PVP K12, PVP K15, PVP K17, PVP 25, PVP K30, PVP K60 and PVP K90.

6. The positive electrode dispersant according to claim 1, characterized in that, Component A is an acrylate dispersant, component B is butanol polyoxypropylene ether phosphate, and component C is octanoyl oxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.

33. Preferably, the mass of component C accounts for 10%-50% of the total mass of components A and B, for example, 40%. Alternatively, component A may be an acrylate dispersant, component B may be tri-n-octylphosphine oxide, and component C may be acetoxyxamic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:

1. Preferably, the mass of component C accounts for 10%-50% of the total mass of components A and B, for example, 10%. Alternatively, component A is a polyvinylpyrrolidone dispersant, component B is 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, and component C is octanoyloxyoxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:1.5; preferably, the mass of component C accounts for 10%-50% of the total mass of components A and component B, for example, 20%. Component B is n-octyl phosphate; component C is ethyl acetylhydroxamic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.33; preferably, the mass of component C accounts for 10%-50% of the total mass of components A and B, for example, 20%. Alternatively, component A may be a polyvinylpyrrolidone dispersant, component B may be polyethylene glycol monomethyl ether phosphate, and component C may be salicylic acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:4; preferably, the mass of component C accounts for 20%-50% of the total mass of components A and B, for example, 50%. Alternatively, component A may be an acrylate dispersant, component B may be isotridecyl polyoxyethylene ether phosphate, and component C may be octanoyl oxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:

4. Preferably, the mass of component C accounts for 20%-40% of the total mass of components A and B, for example, 40%. Alternatively, component A may be an acrylate dispersant, component B may be butanol polyoxyethylene polyoxypropylene ether phosphate, and component C may be octanoyl oxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:-2.33; preferably, the mass of component C accounts for 10%-50% of the total mass of components A and B, for example, 40%. Alternatively, component A may be an acrylate dispersant, component B may be octylphenol polyoxyethylene ether phosphate, and component C may be octyloxyoxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.33; preferably, the mass of component C accounts for 10%-50% of the total mass of components A and B, for example, 40%. Alternatively, component A is an acrylate dispersant, component B is di(2-ethylhexyl) phosphate and tributyl phosphate, and component C is octanoyl oxime acid. Preferably, the mass ratio of component A to component B is 1:(0.5-9), for example, 1:2.

33. Preferably, the mass of component C accounts for 10%-50% of the total mass of component A and component B, for example, 50%.

7. A positive electrode slurry, characterized in that, It includes a positive electrode active material, a binder, and a positive electrode dispersant as described in any one of claims 1-6.

8. The positive electrode slurry according to claim 7, characterized in that, The positive electrode active material is preferably lithium iron phosphate material, such as lithium iron phosphate and / or carbon-coated lithium iron phosphate; And / or, in the positive electrode slurry, the binder is polyvinylidene fluoride and / or carboxyl-modified polyvinylidene fluoride; And / or, in the positive electrode slurry, the binder accounts for 1%-3% of the total solid mass, for example, 1.7% or 1.8% by mass; And / or, in the positive electrode slurry, the mass percentage of the positive electrode dispersant is 0.1%-0.5%, for example, 0.2%, based on 100% of the total solid mass; And / or, in the positive electrode slurry, the mass percentage of the positive electrode active material is 93%-98% based on 100% of the total solid mass, for example, 95.8% or 97.4%; And / or, the positive electrode slurry further includes a conductive agent and / or a positive electrode lithium replenishing agent; The conductive agent is preferably conductive carbon black and / or carbon nanotubes; The positive electrode lithium replenishing agent is preferably lithium iron ferrite and / or lithium nickel ferrite, such as Li5FeO4; In the positive electrode slurry, the conductive agent preferably accounts for 0.5%-3% of the total solid mass, for example, 0.7%. In the aforementioned positive electrode slurry, the mass percentage of the positive electrode lithium supplement is preferably 0%-3%, for example, 1.5%, based on 100% of the total solid mass. When the binder is PVDF, the mass percentage of the positive electrode lithium replenishing agent is preferably 0.5%-3% based on 100% of the total solid mass.

9. A positive electrode sheet, characterized in that, It is prepared using the positive electrode slurry as described in claim 7 or 8.

10. A secondary battery, characterized in that, It includes the positive electrode sheet as described in claim 9.

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