Lithium battery positive electrode slurry dispersing agent as well as preparation method and application thereof

Abstract

The invention provides a lithium battery positive electrode slurry dispersing agent as well as a preparation method and application thereof. The monomer components for preparing the lithium battery positive electrode slurry dispersant comprise 10%-15% of a polymeric monomer containing aromatic nucleus and / or organic amine, 5%-10% of a polymeric monomer containing phosphate and / or carboxylate and / or sulfonate, 65%-75% of an olefin polymeric monomer and 5%-15% of a polyether / polyester / phosphate polymeric monomer containing 2-10 carbon atoms and having a small and long chain structure. The dispersing agent disclosed by the invention has good dispersity on a conductive agent and a positive electrode material, has high stability and excellent viscosity reduction effect, has excellent impedance reduction effect, has advantages on pole piece resistance and four probes, can exert good dispersity by a small addition amount, is beneficial to exerting battery energy, and can be applied to the field of lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries and lithium ion batteries. The method can be widely applied to lithium battery positive electrode slurry.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a lithium battery positive electrode slurry dispersant, a preparation method and an application thereof. Background Art

[0002] Lithium-ion batteries are widely used in aerospace, national defense, automobile, 3C and other fields due to their advantages such as high specific energy, long cycle life, low self-discharge rate, no memory effect, and environmental friendliness. With the continuous development and progress of lithium-ion batteries, there are higher requirements for lithium-ion battery rate, cycle capacity retention rate, energy density, etc., which has a significant impact - the dispersion difficulty of the positive electrode slurry formula has increased. In order to ensure the good dispersion of the electrode material, a dispersant needs to be added to the electrode slurry. The dispersant can maintain the uniform dispersion and stability of the electrode material particles for a long time, thereby preparing an electrode with stable performance.

[0003] However, the current development of dispersants is either for positive electrode materials or for conductive materials, and rarely for both. For example, in the research on positive electrode materials: CN114843516A discloses a three-component dispersant for positive electrode materials of lithium ion batteries, which makes the positive electrode materials have a higher solid content, a lower viscosity, and can be evenly dispersed when using less solvent. CN115490866A discloses a polycarboxylate dispersant for lithium battery slurry, which increases the solid content and coating convenience of electrode active materials, and is conducive to the uniform dispersion of particles such as electrode active materials and conductive carbon. CN113540463B discloses a dispersant including polyacrylonitrile and polystyrene, or a copolymer formed by copolymerization of acrylonitrile monomer and styrene monomer, which can reduce the gel and agglomeration of materials during the homogenization of positive electrode materials, reduce the viscosity of the slurry, and improve the stability of the slurry; improve the dispersibility of positive electrode materials and reduce the viscosity of the slurry; and for the research on conductive agent materials: Patents US 6787600, US6599973, US5530070, etc. all propose dispersants of different structures for the dispersion of carbon nanotubes in the medium. Patent KR15-741676 proposes hydrogenated nitrile rubber (HNBR) as a dispersant. Patent CN108059151A discloses a dispersant based on modified polyethylene glycol (PEG), etc. This leads to the fact that some lithium battery positive electrode slurries that require high performance often contain two or more dispersants. Some of these dispersants are used to disperse the conductive material in the conductive slurry, and some are added to disperse the main material. The disadvantage of this application is that the dispersant accounts for a certain proportion and the two dispersants may be difficult to be compatible.

[0004] Therefore, the field is in urgent need of developing a positive electrode slurry dispersant to achieve a good dispersion effect on both the positive electrode main material and the conductive agent material, and thus obtain a dispersed and stable positive electrode slurry without the addition of additional dispersants, which has great advantages in viscosity reduction, solidification, coating, impedance reduction, etc. Summary of the invention

[0005] Based on the defects of the prior art, the first purpose of the present invention is to provide a lithium battery positive electrode slurry dispersant; the second purpose of the present invention is to provide a method for preparing the lithium battery positive electrode slurry dispersant; the third purpose of the present invention is to provide an application of the lithium battery positive electrode slurry dispersant in the preparation of lithium battery positive electrode slurry.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] In one aspect, the present invention provides a lithium battery positive electrode slurry dispersant, wherein the monomer components for preparing the dispersant include, by mass percentage, 100%:

[0008] Containing 10% to 15% of aromatic ring and / or organic amine polymer monomer;

[0009] Contains 5% to 10% of phosphate and / or carboxylate and / or sulfonate polymer monomers;

[0010] Olefin polymerization monomers 65% to 75%;

[0011] Contains a small long chain structure of 2 to 10 carbon atoms and 5% to 15% of polyether / polyester / phosphate ester polymerization monomers.

[0012] The configurations of the four monomers used to prepare the dispersant of the present invention may be fish bones, branches, etc. The molecular weight of the dispersant prepared by the present invention is 1 to 7w, and the configuration diagram is as follows: Figure 1 shown.

[0013] In the above-mentioned lithium battery positive electrode slurry dispersant, preferably, the aromatic ring and / or organic amine-containing polymer monomer is selected from one or more combinations of 1,3-benzenediol, benzoic acid, 2-ethylhexylamine, hexylamine and octylamine, but is not limited thereto.

[0014] The aromatic ring and / or organic amine-containing polymerizable monomer of the present invention is a polymerizable monomer containing an aromatic ring, amines, and the like.

[0015] In the above-mentioned lithium battery positive electrode slurry dispersant, preferably, the phosphate and / or carboxylate and / or sulfonate-containing polymerization monomer is selected from one or a combination of two or more of alkyl alcohol ether sulfosuccinate diester sodium salt, allyl polyether ammonium phosphate salt, alkyl sulfosuccinate sodium salt and allyl sodium sulfonate, but is not limited thereto.

[0016] The phosphate and / or carboxylate and / or sulfonate-containing polymer monomers of the present invention are polymer monomers containing salt substances such as phosphoric acid, carboxylic acid, and sulfonic acid.

[0017] In the above-mentioned lithium battery positive electrode slurry dispersant, preferably, the olefin polymerizable monomer is selected from one or more combinations of ethylene, styrene, allylbenzene and methylstyrene, but is not limited thereto.

[0018] The olefin polymer monomer of the present invention is a polymer monomer of an alkane or olefin chain having a long carbon chain structure.

[0019] In the above-mentioned lithium battery positive electrode slurry dispersant, preferably, the polyether / polyester / phosphate ester polymerization monomer containing a small long chain structure of 2 to 10 carbon atoms is selected from one or more combinations of allyl alcohol polyoxyalkyl ether, butyl acrylate and butyl methacrylate, but is not limited thereto.

[0020] The polyether / polyester / phosphate ester polymer monomer of the present invention having a small long chain structure of 2 to 10 carbon atoms is a polymer monomer containing functional groups such as polyether, polyester, and phosphate ester.

[0021] On the other hand, the present invention also provides a method for preparing the above-mentioned lithium battery positive electrode slurry dispersant, the method comprising the following steps:

[0022] Step 1, stirring and mixing an organic solvent, a polymer monomer containing an aromatic ring and / or an organic amine, and an olefin polymer monomer to obtain a mixed solution;

[0023] Step 2, heating the mixed solution under a nitrogen atmosphere, and adding an initiator to stir and react to obtain a reaction solution;

[0024] Step three, continue to add initiator, phosphate and / or carboxylate and / or sulfonate polymer monomers, and polyether / polyester / phosphate polymer monomers with a small long chain structure of 2 to 10 carbon atoms to the reaction solution, maintain the heating temperature and continue stirring the reaction to obtain a dispersant.

[0025] In the above preparation method, preferably, the organic solvent is selected from N-vinyl pyrrolidone, one or more combinations thereof, but is not limited thereto.

[0026] In the above preparation method, preferably, the amount of the organic solvent used is 2 to 5 times the total mass of the monomers.

[0027] In the above preparation method, preferably, the initiator is selected from azobisisobutyronitrile and / or benzoyl peroxide, but is not limited thereto.

[0028] In the above preparation method, preferably, the amount of the initiator used is 0.5% to 2.5% of the total weight of the monomers.

[0029] In the above preparation method, preferably, in step 2, the temperature of the heating and stirring reaction is 50-100° C., and the stirring reaction time is 3-9 h.

[0030] In the above preparation method, preferably, in step three, the temperature of the heating and stirring reaction is 50-100° C., and the stirring reaction time is 2-6 h.

[0031] In another aspect, the present invention also provides the use of the above-mentioned lithium battery positive electrode slurry dispersant or the lithium battery positive electrode slurry dispersant prepared by the above-mentioned preparation method in the preparation of lithium battery positive electrode slurry.

[0032] Beneficial effects of the present invention:

[0033] The lithium battery positive electrode slurry dispersant of the present invention:

[0034] (1) It has good dispersibility for both conductive agents and positive electrode materials; using it to prepare positive electrode slurry for lithium batteries can significantly improve preparation efficiency and reduce preparation costs, and has excellent effects during mixing and coating operations;

[0035] (2) It has high stability and excellent viscosity reduction effect. The prepared slurry has low viscosity rebound after 24 hours, 48 ​​hours or even one month;

[0036] (3) It has excellent impedance reduction effect, and has advantages over electrode resistance and four-probe;

[0037] (4) Even a small amount of addition can achieve good dispersibility, which is beneficial to the battery's energy performance.

[0038] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 Various possible configurations of the dispersants prepared according to the present invention. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The process, conditions, reagents, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are all common knowledge and common common sense in the art, and the present invention does not particularly limit the contents.

[0042] Embodiment 1:

[0043] This embodiment provides a lithium battery positive electrode slurry dispersant. The monomer components for preparing the dispersant include, by mass percentage, 100%:

[0044] Component A: hexylamine 12%;

[0045] Component B: allyl polyether ammonium phosphate 8%;

[0046] Component C: styrene 70%;

[0047] Component D: Butyl acrylate 10%.

[0048] This embodiment also provides a method for preparing a lithium battery positive electrode slurry dispersant, the preparation method further comprising adding 3 times the total mass of the above-mentioned monomers as an organic solvent N-vinyl pyrrolidone and 1% of the total mass of the monomers as an initiator azobisisobutyronitrile; the specific preparation method is as follows:

[0049] (1) Add hexylamine, styrene and N-vinyl pyrrolidone to a 2L five-necked round-bottom flask equipped with a nitrogen device, a stirring device, a reflux condenser and a thermometer, rotate at 60 r / min, stir for 5 min, and stir to obtain a mixed solution;

[0050] (2) passing nitrogen gas, heating to 70° C. in a nitrogen atmosphere, then adding an initiator, azobisisobutyronitrile (0.4%), maintaining the temperature at 70° C., stirring continuously at a speed of 60 r / min, reacting for 3 h, and obtaining a reaction solution;

[0051] (3) Then, the initiator azobisisobutyronitrile (0.6%) was added and the reaction was continued for 10 minutes. Then, allyl polyether ammonium phosphate and butyl acrylate were added and the reaction was continued with stirring at a speed of 60 r / min for 2 hours to stop the reaction and obtain a dispersant.

[0052] Embodiment 2:

[0053] This embodiment provides a lithium battery positive electrode slurry dispersant. The monomer components for preparing the dispersant include, by mass percentage, 100%:

[0054]

[0055] This embodiment also provides a method for preparing a lithium battery positive electrode slurry dispersant, the preparation method further comprising adding 3 times the total mass of the above-mentioned monomers as an organic solvent N-vinyl pyrrolidone and 1% of the total mass of the monomers as an initiator azobisisobutyronitrile; the specific preparation method is as follows:

[0056] (1) In a 2L five-necked round-bottom flask equipped with a nitrogen device, a stirring device, a reflux condenser and a thermometer, octylamine, ethylene and N-vinyl pyrrolidone were added, the speed was 60 r / min, and the mixture was stirred for 5 min to obtain a mixed solution;

[0057] (2) passing nitrogen gas, heating to 70° C. in a nitrogen atmosphere, then adding an initiator, azobisisobutyronitrile (0.4%), maintaining the temperature at 70° C., stirring continuously at a speed of 60 r / min, reacting for 4 h, and obtaining a reaction solution;

[0058] (3) Then, an initiator, azobisisobutyronitrile (0.6%), was added and the reaction was continued for 10 minutes. Then, sodium allyl sulfonate and allyl alcohol polyoxyalkyl ether were added and the reaction was continued with stirring at a speed of 60 r / min for 3 hours to stop the reaction and obtain a dispersant.

[0059] Embodiment 3:

[0060] This embodiment provides a method for preparing a thin film composite containing MWCNTs using a CNT conductive slurry. The specific preparation method includes:

[0061] CNT (non-purified MWCNT FT7000, with an outer diameter of 5 to 10 nm, prepared by CNano Inc. Co.) was dissolved in 380 g of NMP using 4 g of the dispersant obtained in the comparative group PVP K30, Examples 1 and 2, and 16 g of CNT was added. A vertical tank was used and 400 g of 0.3 mm zirconium beads were added. The mixture was subjected to mechanical grinding treatment for 4 h at room temperature (about 25 ° C) to obtain a black MWCNT-containing dispersion. Finally, the zirconium beads were filtered to obtain a CNT dispersion liquid, which was uniformly dispersed without precipitation. 3 g of the filtered CNT dispersion liquid was taken out, coated on PET using a 20 μm gap scraper, and baked at 120 ° C for 1 h to prepare a thin film composite containing MWCNT.

[0062] The conductivity test experiment was conducted on the prepared MWCNT-containing thin film composite, and the conductivity was specifically tested using a four-probe resistance meter. The results are shown in Table 1 below.

[0063] Table 1

[0064]

[0065] It can be seen from the experimental results in Table 1 that compared with the control group, the MWCNT film composite obtained by using the dispersants of Examples 1 and 2 of the present invention has high stability, low slurry viscosity, excellent viscosity reduction effect, low 24h and 48h viscosity rebound, and excellent impedance reduction effect.

[0066] Embodiment 4:

[0067] This embodiment provides a method for preparing a lithium battery positive electrode slurry and assembling a lithium ion battery using the CNT conductive slurry prepared in Example 3.

[0068] The preparation method of lithium battery positive electrode slurry is as follows:

[0069] First, 18 g of the binder PVDF was dissolved in 400 g of N-methylpyrrolidone solvent to prepare a solution, and 564 g of lithium iron phosphate and 18 g of the three CNT conductive slurries prepared in Example 3 were added in sequence at a rotation speed of 120 r / min and stirred for 30 min to allow the powder material to be fully and evenly mixed in the solvent to obtain lithium iron phosphate positive electrode slurry.

[0070] The method of assembling lithium-ion batteries is as follows:

[0071] The positive electrode slurry was mixed and coated on aluminum foil, and then dried overnight at 110°C in a vacuum to prepare the positive electrode. 95% graphite, 1.5% conductive carbon, 1.5% sodium carboxymethyl cellulose and 2% styrene butadiene rubber were mixed and coated on copper foil, and then dried overnight at 60°C in a vacuum to prepare the negative electrode. 1 mol of LiPF6 was used as the lithium salt, the solvent was a mixed solvent composed of EC / DC / EMC (volume ratio of 1:1:1) as the electrolyte, and porous glass fiber was used as the separator to assemble the lithium-ion battery.

[0072] In comparison groups 3 and 4, 0.2% of a commercially available positive electrode dispersant was added to the positive electrode slurry for stirring. The commercially available positive electrode dispersant 1 was triethyl phosphite; and the commercially available positive electrode dispersant 2 was Triton X.

[0073] The assembled lithium-ion battery was subjected to a membrane resistivity test experiment and a capacity retention rate test experiment. The experimental results are shown in Tables 2 and 3 below.

[0074] Table 2

[0075]

[0076] Table 3

[0077]

[0078]

[0079] It can be seen from the experimental results in Table 2 that compared with the control group, the positive electrode slurry obtained by using the dispersants of Examples 1 and 2 of the present invention has low viscosity, excellent viscosity reduction effect, low viscosity rebound after 24h and 48h, and has excellent dispersion, viscosity reduction and impedance reduction effects; and even at a small amount of addition and without the need to use other dispersants, the effect is obvious enough.

[0080] It can be seen from the experimental results in Table 3 that compared with the control group, the batteries prepared using the dispersants of Examples 1 and 2 of the present invention have high initial efficiency and high capacity retention rate; and the effect is obvious enough even at a small amount and without the need for use with other dispersants.

[0081] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A lithium battery positive electrode slurry dispersant, wherein the monomer components for preparing the dispersant include, by mass percentage, 100%: Containing 10% to 15% of aromatic ring and / or organic amine polymer monomer; Contains 5% to 10% of phosphate and / or carboxylate and / or sulfonate polymer monomers; Olefin polymerization monomers 65% to 75%; Contains a small long chain structure of 2 to 10 carbon atoms and 5% to 15% of polyether / polyester / phosphate ester polymerization monomers.

2. The lithium battery positive electrode slurry dispersant according to claim 1, characterized in that: The aromatic ring and / or organic amine-containing polymer monomer is selected from one or more combinations of 1,3-benzenediol, benzoic acid, 2-ethylhexylamine, hexylamine and octylamine.

3. The preparation method according to claim 1, characterized in that: The phosphate and / or carboxylate and / or sulfonate-containing polymer monomer is selected from one or a combination of two or more of alkyl alcohol ether sulfosuccinate sodium salt, allyl polyether ammonium phosphate salt, alkyl sulfosuccinate sodium salt and allyl sodium sulfonate.

4. The lithium battery positive electrode slurry dispersant according to claim 1, characterized in that: The olefin polymerizable monomer is selected from one or more combinations of ethylene, styrene, allylbenzene and methylstyrene.

5. The lithium battery positive electrode slurry dispersant according to claim 1, characterized in that: The polyether / polyester / phosphate ester polymer monomer containing a small long chain structure of 2 to 10 carbon atoms is selected from one or more combinations of allyl alcohol polyoxyalkyl ether, butyl acrylate and butyl methacrylate.

6. The method for preparing a lithium battery positive electrode slurry dispersant according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: Step 1, stirring and mixing an organic solvent, a polymer monomer containing an aromatic ring and / or an organic amine, and an olefin polymer monomer to obtain a mixed solution; Step 2, heating the mixed solution under a nitrogen atmosphere, and adding an initiator to stir and react to obtain a reaction solution; Step three, continue to add initiator, phosphate and / or carboxylate and / or sulfonate polymer monomers, and polyether / polyester / phosphate polymer monomers with a small long chain structure of 2 to 10 carbon atoms to the reaction solution, maintain the heating temperature and continue stirring the reaction to obtain a dispersant.

7. The preparation method according to claim 6, characterized in that: The organic solvent is selected from a combination of one or more of N-vinyl pyrrolidone, N-formyl dimethylamine and acetyl dimethylamine; Preferably, the amount of the organic solvent used is 2 to 5 times the total mass of the monomers.

8. The preparation method according to claim 6, characterized in that: The initiator is selected from azobisisobutyronitrile and / or benzoyl peroxide; Preferably, the amount of the initiator used is 0.5% to 2.5% of the total weight of the monomers.

9. The preparation method according to claim 6, characterized in that: In step 2, the temperature of the heating and stirring reaction is 50 to 100° C., and the stirring reaction time is 3 to 9 hours; Preferably, in step three, the temperature of the heating and stirring reaction is 50-100° C., and the stirring reaction time is 2-6 hours.

10. Use of the lithium battery positive electrode slurry dispersant according to any one of claims 1 to 5 or the lithium battery positive electrode slurry dispersant prepared by the preparation method according to any one of claims 6 to 9 in preparing lithium battery positive electrode slurry.

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