Ternary positive electrode slurry and preparation method therefor and use thereof

Abstract

A ternary positive electrode slurry and a preparation method therefor and a use thereof. The ternary positive electrode slurry comprises a positive electrode material and an organic solvent, the positive electrode material comprises a ternary positive electrode active substance, a dispersing auxiliary agent, and a conductive agent, and the dispersing auxiliary agent comprises any one or a combination of at least two of compounds having a structure represented by formula I. By selecting the described compounds having the structure represented by formula I to be the dispersing auxiliary agent, the dispersity of the ternary positive electrode active substance and conductive agent in the organic solvent is effectively improved, so that the obtained ternary positive electrode slurry can have both excellent storage stability and excellent conductivity, also has high solid content and low viscosity, and is suitable for being used in lithium ion batteries.

Description

A ternary positive electrode slurry and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 30, 2023, with application number 202311106538.6 and application name “A ternary positive electrode slurry, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a ternary positive electrode slurry and a preparation method and application thereof. Background Art

[0003] With the rapid development of consumer electronics, new energy vehicles, and wearable electronics, the development of lithium-ion batteries has garnered widespread attention. Cathode materials are key components of lithium-ion batteries, and their performance directly impacts battery performance. Ternary cathode materials have become a hot research topic for researchers due to their high theoretical specific capacity (up to 274 mAh / g), high reaction platform voltage (approximately 3.0 to 4.4 V), and relatively low cost.

[0004] During the processing of ternary lithium-ion battery cells, a slurry of ternary cathode material powder, conductive carbon black, adhesive, and organic solvent (such as NMP) needs to be coated on aluminum foil to increase the battery capacity. CN113258036A discloses a ternary cathode slurry and a preparation method thereof. The method comprises: first mixing and stirring the ternary cathode material and the binder for 5 to 60 minutes, then adding the solvent and continuing to stir, and finally adding the conductive agent and continuing to stir for 30 to 240 minutes to obtain the ternary cathode slurry. The ternary cathode slurry prepared by this invention has good dispersion effect, short time, and low cost, solving the technical problems of the current ternary slurry, such as long dispersion time, easy agglomeration, high energy consumption, and high overall cost.

[0005] However, the industry is gradually adopting NCM811 with high nickel content to replace the previously common NCM111 or NCM523. This leads to an increase in the viscosity of the positive electrode slurry during the processing, and the slurry will gel as it changes over time, seriously affecting the coating effect; at the same time, in order to improve processing efficiency, a process method of increasing the solid content of the positive electrode slurry is chosen, which will also lead to problems such as cracking during the coating and drying process.

[0006] Because developing a ternary positive electrode slurry with low viscosity, high solid content and excellent conductive properties is a technical problem that urgently needs to be solved in this field.

[0007] Summary of the Invention

[0008] In view of the deficiencies in the prior art, the object of the present invention is to provide a ternary positive electrode slurry and a preparation method and application thereof, wherein the ternary positive electrode slurry comprises a positive electrode material and an organic solvent, wherein the positive electrode material comprises a ternary positive electrode active substance, a dispersing aid and a conductive agent. By limiting the above-mentioned dispersing aid to include a compound having a structure shown in Formula I, the dispersibility of the ternary positive electrode active substance and the conductive agent in the organic solvent is effectively improved, so that the obtained ternary positive electrode slurry can have both high solid content and low viscosity, as well as excellent storage stability and conductive properties, and further has excellent flexibility after being made into a positive electrode sheet.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a ternary positive electrode slurry, wherein the ternary positive electrode slurry comprises a positive electrode material and an organic solvent;

[0011] The positive electrode material includes a ternary positive electrode active material, a dispersing aid and a conductive agent;

[0012] The dispersing aid comprises any one or a combination of at least two of the compounds having the structure shown in Formula I:

[0013] Wherein, R is selected from an alkyl group, m is selected from an integer between 1 and 500, and n is selected from an integer between 1 and 10.

[0014] The m can be 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400 or 450, etc.

[0015] The n can be 2, 4, 6, 8 or 10, etc.

[0016] The ternary positive electrode slurry provided by the present invention includes a positive electrode material and an organic solvent, wherein the positive electrode material includes a ternary positive electrode active substance, a dispersing aid and a conductive agent, and the dispersing aid is limited to any one or a combination of at least two of the compounds having the structure shown in Formula I; the above-mentioned compound having the structure shown in Formula I contains both a polyester segment and a polyaniline segment, wherein the polyaniline segment has a strong adsorption effect on the conductive agent and can be adsorbed to the surface of the conductive agent, and the polyester segment, as a solvated long chain, has good affinity for the organic solvent, thereby preventing the conductive agent from aggregating in the organic solvent. At the same time, the ester group in the polyester segment also has a strong adsorption effect on the ternary positive electrode active substance and can be further adsorbed on the surface of the ternary positive electrode active substance, thereby further connecting the conductive agent to the surface of the ternary positive electrode active substance, effectively improving the conductive performance of the ternary positive electrode slurry, and also utilizing the steric effect of the short long chain to avoid aggregation between the ternary positive electrode active substances, ultimately obtaining a ternary positive electrode slurry with excellent conductive performance, excellent storage stability, high solid content and low viscosity.

[0017] It should be noted that the present invention does not impose any particular limitation on the preparation method of the compound having the structure shown in Formula I. Exemplarily, the compound can be prepared according to the following method:

[0018] (1) reacting terephthalic acid and ethylene glycol in the presence of a catalyst, and adding R-OH dropwise for end-capping to obtain a polyester; wherein R is selected from an alkyl group;

[0019] N-phenyl-1,4-p-phenylenediamine is oxidized by ferric ions to form aniline oligomers;

[0020] (2) reacting the polyester obtained in step (1) with the aniline oligomer to obtain the compound having the structure shown in formula I.

[0021] Preferably, the molar ratio of terephthalic acid to ethylene glycol in step (1) is 1:(1.002-1.05), for example, 1:1.005, 1:1.007, 1:1.01, 1:1.02, 1:1.03 or 1:1.04.

[0022] Preferably, the catalyst in step (1) comprises p-toluenesulfonic acid.

[0023] Preferably, based on the amount of terephthalic acid in step (1) being 100%, the amount of the catalyst in step (1) is 0.1-2%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6% or 1.8%.

[0024] Preferably, the amount of R-OH used in step (1) is the difference in the number of moles of terephthalic acid compared to ethylene glycol.

[0025] Preferably, the above step (1) specifically comprises: adding terephthalic acid and ethylene glycol into a reactor, adding a catalyst, heating to 120-140° C. (e.g., 122° C., 124° C., 126° C., 128° C., 130° C., 132° C., 134° C., 136° C., or 138° C., etc.) using a steam bath, reacting for 1-4 hours (e.g., 1.5 hours, 2 hours, 2.5 hours, 3 hours, or 3.5 hours, etc.), collecting the effluent liquid under nitrogen protection, heating to 160-195° C. (e.g., 165° C., 170° C., 175° C., 180° C., 185° C., or 190° C., etc.), and slowly adding R-OH dropwise for end-capping to obtain the polyester.

[0026] Preferably, the above step (2) specifically comprises: dissolving N-phenyl-1,4-p-phenylenediamine in diethyl ether, then slowly adding dropwise to hydrochloric acid having a concentration of 0.5 to 3 mol / L (e.g., 1 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L), mechanically stirring for 1 to 5 hours (e.g., 2 hours, 3 hours, or 4 hours, etc.) to obtain a reaction solution, then adding dropwise a hydrochloric acid solution containing ferric chloride to the above reaction solution, continuing to stir for 1 to 5 hours (e.g., 2 hours, 3 hours, or 4 hours, etc.), washing the precipitated solid three times with hydrochloric acid, then washing once with ammonia water, and finally reducing with hydrazine hydrate, and filtering to obtain the aniline oligomer.

[0027] Preferably, the above step (3) specifically comprises: dissolving the polyester in dimethyl sulfoxide (DMSO), adding thionyl chloride and refluxing, reacting at 60-80°C (e.g., 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C or 78°C, etc.) for 1-3h (e.g., 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h or 2.8h, etc.), then distilling off the thionyl chloride under reduced pressure, and finally adding petroleum ether to precipitate the product, separating and drying it for later use. Obtaining the treated polyester; dissolving the treated polyester and aniline oligomer in DMSO, heating to 170-190°C (e.g., 172°C, 174°C, 176°C, 178°C, 180°C, 182°C, 184°C, 186°C or 188°C, etc.) and reacting for 2-4 hours (e.g., 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h or 3.8h, etc.), discharging the product into distilled water, and washing it multiple times to obtain a compound having the structure shown in Formula I.

[0028] Preferably, the solid content of the ternary positive electrode slurry is not less than 70%, for example, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88% or 90%.

[0029] Preferably, the viscosity of the ternary positive electrode slurry is 7000-8000 mPa·s, for example, 7100 mPa·s, 7200 mPa·s, 7300 mPa·s, 7400 mPa·s, 7500 mPa·s, 7600 mPa·s, 7700 mPa·s, 7800 mPa·s or 7900 mPa·s, etc., and the test conditions for the above viscosity are 25°C, using rotor No. 4 for testing, and the speed is 15-30 rpm. The specific speed needs to be selected according to the viscosity of the slurry.

[0030] Preferably, the organic solvent comprises N-methylpyrrolidone (NMP).

[0031] Preferably, the ternary positive electrode active material includes lithium nickel cobalt manganate material and / or lithium nickel cobalt aluminum oxide material, for example, the lithium nickel cobalt manganate material and / or lithium nickel cobalt aluminum oxide material provided by Ningbo Rongbai Technology Co., Ltd. and Bamo Technology Co., Ltd.

[0032] Preferably, the lithium nickel cobalt manganese oxide material includes NCM811.

[0033] Preferably, the mass percentage of the ternary positive electrode active substance in the positive electrode material is 90-975%, for example, 90.5%, 91%, 91.5%, 92%, 92.5%, 93%, 93.5%, 94%, 94.5%, 95% or 96%, etc.

[0034] Preferably, the mass percentage of the conductive agent in the positive electrode material is 1-3%, for example, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6% or 2.8%.

[0035] Preferably, the conductive agent includes any one of carbon black, carbon nanotubes or graphene, or a combination of at least two of them.

[0036] Preferably, the mass percentage of the dispersing aid in the positive electrode material is 0.1-0.5%, for example, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or 0.45%.

[0037] As a preferred technical solution of the present invention, the mass percentage of the dispersing aid in the positive electrode material is further limited to 0.1-0.5%. If the mass percentage of the added dispersing aid is lower than 0.1%, the positive electrode slurry will have poor dispersibility, the viscosity will be higher than the process requirement range, the processability will be poor, and the resistance of the dry film electrode will be high and the conductivity will be poor. If the mass percentage of the added dispersing aid is higher than 0.5%, the dispersing aid will have a very limited effect on improving the dispersion effect of the positive electrode slurry, and will lead to material waste. It will also occupy the proportion of solid content in the positive electrode, resulting in a decrease in the energy density of the final battery.

[0038] Preferably, the R is selected from C1 to C20 alkyl, more preferably C1 to C5 alkyl.

[0039] Preferably, m is selected from an integer between 10 and 100.

[0040] Preferably, n is selected from an integer between 5 and 10.

[0041] Preferably, the positive electrode material further includes a binder.

[0042] Preferably, the mass percentage of the binder in the positive electrode material is 1-2%, for example, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or 1.9%.

[0043] Preferably, the binder comprises polyvinylidene fluoride (PVDF).

[0044] In a second aspect, the present invention provides a method for preparing the ternary positive electrode slurry as described in the first aspect, the preparation method comprising: uniformly mixing a ternary positive electrode active material, an organic solvent, a dispersing aid, a conductive agent and optionally a binder to obtain the ternary positive electrode slurry.

[0045] Preferably, the mixing specifically comprises the following steps:

[0046] (1) uniformly mixing the binder and the organic solvent to obtain glue solution A;

[0047] (2) uniformly mixing the dispersing aid and the glue A obtained in step (1) to obtain glue B;

[0048] (3) mixing the conductive agent and the glue B obtained in step (2) to obtain glue C;

[0049] (4) The ternary positive electrode active material and the glue C obtained in step (3) are mixed evenly to obtain the ternary positive electrode slurry.

[0050] In a third aspect, the present invention provides a positive electrode plate, which is obtained by coating the ternary positive electrode slurry as described in the first aspect on a current collector and then drying it.

[0051] In a fourth aspect, the present invention provides a lithium-ion battery, comprising the positive electrode sheet as described in the third aspect.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The ternary positive electrode slurry provided by the present invention includes a positive electrode material and an organic solvent, wherein the positive electrode material includes a ternary positive electrode active substance, a dispersing aid and a conductive agent, and the dispersing aid includes any one or a combination of at least two of the compounds having the structure shown in Formula I; by selecting the above-mentioned compound having the structure shown in Formula I as the dispersing aid, the dispersibility of the ternary positive electrode active substance and the conductive agent in the organic solvent is effectively improved, so that the obtained ternary positive electrode slurry can have both excellent storage stability and conductive performance, high solid content and low viscosity, and after being further made into a positive electrode sheet, it also has excellent properties and is suitable for use in lithium-ion batteries. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] Preparation Example 1

[0056] A dispersing aid A1, whose specific structural formula is as follows:

[0057] The preparation method of the dispersing aid A1 provided in this preparation example comprises the following steps:

[0058] (1) Add 6.207 g of ethylene glycol and 17.444 g of terephthalic acid to a reactor, then add 0.1744 g of p-toluenesulfonic acid, heat to 130°C on a steam bath, react for 90 min, collect the effluent liquid under nitrogen protection, then raise the temperature to 180°C, slowly add 0.160 g of methanol dropwise for end-capping, and obtain polyester;

[0059] 9.2 g of N-phenyl-1,4-p-phenylenediamine monomer was dissolved in 100 mL of anhydrous ether, and the mixture was slowly added dropwise to 1000 mL of 1 mol / L hydrochloric acid, and mechanically stirred for 4 hours to obtain a reaction solution; 14 g of ferric chloride hexahydrate was dissolved in 150 mL of 1 mol / L hydrochloric acid, and the obtained hydrochloric acid solution containing ferric chloride was slowly added dropwise to the above reaction solution, and stirring was continued for 4 hours. A solid was obtained by filtration, and the obtained solid was washed three times with 1 mol / L hydrochloric acid, and then washed once with 1 mol / L ammonia water, and finally reduced with hydrazine hydrate, and filtered to obtain a crude product, which was vacuum dried for 72 hours to obtain an aniline oligomer;

[0060] (2) 22 g of the polyester obtained in step (1) was dissolved in 120 mL of DMSO, 6 mL of thionyl chloride was added, and the mixture was heated to 70° C. and reacted for 2 h. The thionyl chloride was then distilled off under reduced pressure, and the solution was added to petroleum ether. The precipitate was filtered and dried to obtain the treated polyester;

[0061] (3) 9.558 g of the treated polyester obtained in step (2) and 1.458 g of the aniline oligomer obtained in step (1) were added to 40 mL of DMSO for dissolution, heated to 180° C. for reaction for 3 h, and the product was discharged into distilled water and washed 5 times to obtain the dispersing aid A1.

[0062] Characterization data:

[0063] The dispersing agent A1 provided in this preparation example was tested using a nuclear magnetic resonance spectrometer (Varian-300). In the H-NMR spectrum obtained by the test, a single peak appeared at 8.4 ppm, proving the formation of an amide bond. The dispersing agent A1 provided in this preparation example was tested using a Fourier transform infrared spectrometer. In the infrared spectrum obtained by the test, a single peak appeared at 1400 cm -1 A new peak appeared at , which is the carbon-nitrogen stretching peak of the amide bond. The above results all prove that Preparation Example 1 successfully synthesized the dispersing aid A1 with the above specific structure.

[0064] Preparation Example 2

[0065] A dispersing aid A2, whose specific structural formula is as follows:

[0066] The preparation method of the dispersing aid A2 provided in this embodiment comprises the following steps:

[0067] (1) Add 6.207 g of ethylene glycol and 18.274 g of terephthalic acid to a reactor, then add 0.1827 g of p-toluenesulfonic acid, heat to 130°C on a steam bath, react for 90 min, collect the effluent liquid under nitrogen protection, then raise the temperature to 180°C, and slowly add 0.32 g of methanol dropwise for end-capping to obtain a polyester;

[0068] 9.2 g of N-phenyl-1,4-p-phenylenediamine monomer was dissolved in 100 mL of anhydrous ether, and the mixture was slowly added dropwise to 1000 mL of 1 mol / L hydrochloric acid, and mechanically stirred for 4 hours to obtain a reaction solution; 14 g of ferric chloride hexahydrate was dissolved in 150 mL of 1 mol / L hydrochloric acid, and the obtained hydrochloric acid solution containing ferric chloride was slowly added dropwise to the above reaction solution, and stirring was continued for 4 hours. A solid was obtained by filtration, and the obtained solid was washed three times with 1 mol / L hydrochloric acid, and then washed once with 1 mol / L ammonia water, and finally reduced with hydrazine hydrate, and filtered to obtain a crude product, which was vacuum dried for 72 hours to obtain an aniline oligomer;

[0069] (2) 22 g of the polyester obtained in step (1) was dissolved in 120 mL of DMSO, 6 mL of thionyl chloride was added, and the mixture was heated to 70° C. and reacted for 2 h. The thionyl chloride was then distilled off under reduced pressure, and the solution was added to petroleum ether. The precipitate was filtered and dried to obtain the treated polyester;

[0070] (3) 5.806 g of the treated polyester obtained in step (2) and 3.6416 g of the aniline oligomer obtained in step (1) were added to 32 mL of DMSO for dissolution, heated to 180° C. for reaction for 3 h, and the product was discharged into distilled water and washed 5 times to obtain the dispersing aid A2.

[0071] Characterization data:

[0072] The dispersing agent A2 provided in this embodiment was tested using a nuclear magnetic resonance spectrometer (Varian-300). In the H-NMR spectrum obtained by the test, a single peak appeared at 8.4 ppm, proving the formation of an amide bond. The dispersing agent A2 provided in this embodiment was tested using a Fourier transform infrared spectrometer. In the infrared spectrum obtained by the test, a single peak appeared at 1400 cm -1 A new peak appeared at , which is the carbon-nitrogen stretching peak of the amide bond. The above results all prove that Example 2 successfully synthesized the dispersing aid A2 with the above specific structure.

[0073] Preparation Example 3

[0074] A dispersing aid A3, whose specific structural formula is as follows:

[0075] The preparation method of the dispersing aid A3 provided in this embodiment comprises the following steps:

[0076] (1) Add 6.207 g of ethylene glycol and 16.779 g of terephthalic acid to a reactor, then add 0.1678 g of p-toluenesulfonic acid, heat to 130°C on a steam bath, react for 90 min, collect the effluent liquid under nitrogen protection, then raise the temperature to 180°C, and slowly add 0.32 g of methanol dropwise for end-capping to obtain polyester;

[0077] 9.2 g of N-phenyl-1,4-p-phenylenediamine monomer was dissolved in 100 mL of anhydrous ether, and the mixture was slowly added dropwise to 1000 mL of 1 mol / L hydrochloric acid, and mechanically stirred for 4 hours to obtain a reaction solution; 14 g of ferric chloride hexahydrate was dissolved in 150 mL of 1 mol / L hydrochloric acid, and the obtained hydrochloric acid solution containing ferric chloride was slowly added dropwise to the above reaction solution, and stirring was continued for 4 hours. A solid was obtained by filtration, and the obtained solid was washed three times with 1 mol / L hydrochloric acid, and then washed once with 1 mol / L ammonia water, and finally reduced with hydrazine hydrate, and filtered to obtain a crude product, which was vacuum dried for 72 hours to obtain an aniline oligomer;

[0078] (2) 22 g of the polyester obtained in step (1) was dissolved in 120 mL of DMSO, 6 mL of thionyl chloride was added, and the mixture was heated to 70° C. and reacted for 2 h. The thionyl chloride was then distilled off under reduced pressure, and the solution was added to petroleum ether. The precipitate was filtered and dried to obtain the treated polyester;

[0079] (3) 19.204 g of the treated polyester obtained in step (2) and 0.728 g of the aniline oligomer obtained in step (1) were added to 32 mL of DMSO for dissolution, heated to 180° C. for reaction for 2 h, and the product was discharged into distilled water and washed 5 times to obtain the dispersing aid A3.

[0080] Characterization data:

[0081] The dispersing agent A3 provided in this embodiment was tested using a nuclear magnetic resonance spectrometer (Varian-300). In the H-NMR spectrum obtained by the test, a single peak appeared at 8.4 ppm, proving the formation of an amide bond. The dispersing agent A3 provided in this embodiment was tested using a Fourier transform infrared spectrometer. In the infrared spectrum obtained by the test, a single peak appeared at 1400 cm -1 A new peak appeared at , which is the carbon-nitrogen stretching peak of the amide bond. The above results all prove that Example 3 successfully synthesized the dispersing aid A3 with the above specific structure.

[0082] Example 1

[0083] A ternary cathode slurry having a solid content of 75% and comprising a cathode material and NMP;

[0084] The positive electrode material is composed of NCM811, carbon nanotubes, the dispersing agent A1 provided in Preparation Example 1, and PVDF (Solvay, 5130) in a mass ratio of 96:2:0.2:1.8;

[0085] The preparation method of the ternary positive electrode slurry provided in this embodiment includes the following steps:

[0086] (1) PVDF and NMP were mixed and stirred to obtain glue A;

[0087] (2) adding the dispersing aid A1 provided in Preparation Example 1 to the glue solution A obtained in step (1) and stirring the mixture to obtain glue solution B;

[0088] (3) adding carbon nanotubes to the glue solution B obtained in step (2) and stirring uniformly to obtain glue solution C;

[0089] (4) Add NCM811 to the glue C obtained in step (3) and stir evenly to obtain the ternary positive electrode slurry.

[0090] Example 2

[0091] A ternary cathode slurry having a solid content of 78% and comprising a ternary cathode material and NMP;

[0092] The ternary cathode material is composed of NCM811, carbon nanotubes, the dispersing aid A2 provided in Preparation Example 2, and PVDF (Solvay, 5130) in a mass ratio of 95:3:0.5:1.5;

[0093] The preparation method of the ternary positive electrode slurry provided in this embodiment includes the following steps:

[0094] (1) PVDF and NMP were mixed and stirred to obtain glue A;

[0095] (2) adding the dispersing aid A2 provided in Preparation Example 2 to the glue solution A obtained in step (1) and stirring the mixture to obtain glue solution B;

[0096] (3) adding carbon nanotubes to the glue solution B obtained in step (2) and stirring uniformly to obtain glue solution C;

[0097] (4) Add NCM811 to the glue C obtained in step (3) and stir evenly to obtain the ternary positive electrode slurry.

[0098] Example 3

[0099] A ternary positive electrode slurry having a solid content of 80% and comprising a ternary positive electrode material and NMP;

[0100] The ternary cathode material is composed of NCM811, carbon nanotubes, the dispersing aid A3 provided in Preparation Example 3, and PVDF (Solvay, 5130) in a mass ratio of 96:2.7:0.3:1;

[0101] The preparation method of the ternary positive electrode slurry provided in this embodiment includes the following steps:

[0102] (1) PVDF and NMP were mixed and stirred to obtain glue A;

[0103] (2) adding the dispersing aid A3 provided in Preparation Example 3 to the glue solution A obtained in step (1) and stirring the mixture to obtain glue solution B;

[0104] (3) adding carbon nanotubes to the glue solution B obtained in step (2) and stirring uniformly to obtain glue solution C;

[0105] (4) Add NCM811 to the glue C obtained in step (3) and stir evenly to obtain the ternary positive electrode slurry.

[0106] Example 4

[0107] A ternary positive electrode slurry, which differs from Example 1 only in that the ternary positive electrode material consists of NCM811, carbon nanotubes, the dispersing aid A1 provided in Preparation Example 1, and PVDF (Solvay, 5130) in a mass ratio of 96.15:2:0.05:1.8, and other substances and preparation methods are the same as in Example 1.

[0108] Example 5

[0109] A ternary positive electrode slurry, which differs from Example 1 only in that the ternary positive electrode material consists of NCM811, carbon nanotubes, the dispersing aid A1 provided in Preparation Example 1, and PVDF (Solvay, 5130) in a mass ratio of 95.2:2:1:1.8, and other substances and preparation methods are the same as in Example 1.

[0110] Comparative Example 1

[0111] A ternary positive electrode slurry, which differs from Example 1 only in that polyvinyl pyrrolidone (number average molecular weight is (40000) is used to replace the dispersing aid A1 provided in Preparation Example 1, and other substances, amounts and preparation methods are the same as those in Example 1.

[0112] Comparative Example 2

[0113] A ternary positive electrode slurry is different from Example 1 only in that the ternary positive electrode material is composed of NCM811, carbon nanotubes and PVDF (Solvay, 5130) in a mass ratio of 96.2:2:1.8, and other substances, amounts and preparation methods are the same as those in Example 1.

[0114] Performance testing:

[0115] (1) Viscosity: Tested according to the test method provided in GB / T10247-2008, using a Brookfield rotary viscometer at a temperature of 25°C, using a No. 4 rotor, and a speed of 15-30 rpm;

[0116] (2) Resistivity: On the horizontal aluminum foil surface, a 400μm thick wet film was coated on the aluminum foil using a 400μm scraper, and then dried in a 170℃ oven for 45min to obtain a dry film electrode; the dry film electrode was cut into 5×5cm pieces for resistivity testing. The specific resistivity test was carried out in accordance with ISO16750 and IPCTM-650. The electrode resistance meter (Yuanneng Technology, IEST-BER2500) was used for testing. The pressure was 15MPa, the pressure holding time was 20s, and the test temperature was 25℃.

[0117] The ternary positive electrode slurries provided in Examples 1 to 5 and Comparative Examples 1 to 2 were tested according to the above test method. The test results are shown in Table 1:

[0118] Table 1

[0119] According to the data in Table 1, we can see that:

[0120] The ternary positive electrode slurry provided by the present invention, comprising a dispersing aid having a structure represented by Formula I, has a low viscosity and thus excellent processing performance. Furthermore, the resistivity of the prepared dry film electrode is low, indicating excellent conductive performance. Specifically:

[0121] The viscosity of the ternary positive electrode slurry provided in Examples 1 to 3 is 7011 to 7934 mPa·s, and the resistivity of the dry film electrode is 7.86 to 13.08 Ω·cm, which has excellent processing performance and conductivity.

[0122] Comparing the data of Example 1 and Comparative Example 1, it can be seen that when the contents of the ternary active material and the conductive agent are the same, the viscosity of the ternary positive electrode slurry obtained by using conventional PVP as a dispersing aid is as high as 17650 mPa·s, which is relatively high in viscosity and difficult to process. In addition, the resistivity of the dry film electrode further prepared is as high as 28.77 Ω·cm, and the conductive performance is poor.

[0123] Comparing the data of Example 1 and Comparative Example 2, it can be seen that the viscosity of the ternary positive electrode slurry obtained without adding a dispersing aid is as high as 28897 mPa·s, making it very difficult to disperse. In addition, the resistivity of the dry film electrode further prepared is also high, and the conductivity is poor.

[0124] Further comparison of the data of Example 1 and Example 4 also shows that a lower amount of dispersant added will also lead to an increase in the viscosity of the obtained ternary positive electrode slurry and poor dispersibility, and will also lead to a decrease in the conductive performance of the dry film electrode.

[0125] Finally, by comparing the data of Example 1 and Example 5, it can be found that although the addition amount of the dispersing aid is too high, the viscosity of the obtained ternary positive electrode slurry will be lower and the resistivity of the dry film electrode will be lower, but the reduction effect is not very obvious. In addition, since the dispersant will also occupy the proportion of the solid content in the positive electrode, the energy density of the final battery will be reduced.

[0126] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate a ternary positive electrode slurry, its preparation method, and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials of the present invention, addition of auxiliary components, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A ternary positive electrode slurry, characterized in that: The ternary positive electrode slurry comprises a positive electrode material and an organic solvent; The positive electrode material includes a ternary positive electrode active material, a dispersing aid and a conductive agent; The dispersing aid comprises any one or a combination of at least two of the compounds having the structure shown in Formula I: Wherein, R is selected from an alkyl group, m is selected from an integer between 1 and 500, and n is selected from an integer between 1 and 10.

2. The ternary positive electrode slurry according to claim 1, characterized in that: The solid content of the ternary positive electrode slurry is not less than 70%; Preferably, the viscosity of the ternary positive electrode slurry is 7000-8000 mPa·s.

3. The ternary positive electrode slurry according to claim 1 or 2, characterized in that: The organic solvent includes N-methylpyrrolidone.

4. The ternary positive electrode slurry according to any one of claims 1 to 3, characterized in that: The ternary positive electrode active material includes a nickel cobalt lithium manganese oxide material and / or a nickel cobalt aluminum oxide material; Preferably, the nickel cobalt lithium manganese oxide material includes NCM811; Preferably, the mass percentage of the ternary positive electrode active substance in the positive electrode material is 90-97%; Preferably, the mass percentage of the conductive agent in the positive electrode material is 1 to 3%; Preferably, the conductive agent includes any one of carbon black, carbon nanotubes or graphene, or a combination of at least two of them.

5. The ternary positive electrode slurry according to any one of claims 1 to 4, characterized in that: The mass percentage of the dispersing aid in the positive electrode material is 0.1-0.5%; Preferably, the R is selected from C1 to C20 alkyl, more preferably C1 to C5 alkyl; Preferably, m is selected from an integer between 10 and 100; Preferably, n is selected from an integer between 4 and 10.

6. The ternary positive electrode slurry according to any one of claims 1 to 5, characterized in that: The positive electrode material also includes a binder; Preferably, the mass percentage of the binder in the positive electrode material is 1-2%; Preferably, the binder comprises polyvinylidene fluoride.

7. A method for preparing the ternary positive electrode slurry according to any one of claims 1 to 6, characterized in that: The preparation method comprises: mixing a ternary positive electrode active material, a dispersing aid, a conductive agent, an organic solvent and an optional binder to obtain the ternary positive electrode slurry.

8. The preparation method according to claim 7, characterized in that: The mixing specifically comprises the following steps: (1) mixing a binder and an organic solvent uniformly to obtain a glue solution A; (2) mixing the dispersing aid and the glue solution A obtained in step (1) to obtain glue solution B; (3) mixing the conductive agent and the glue B obtained in step (2) to obtain glue C; (4) The ternary positive electrode active material and the glue C obtained in step (3) are mixed evenly to obtain the ternary positive electrode slurry.

9. A positive electrode sheet, characterized in that: The positive electrode sheet is obtained by coating the ternary positive electrode slurry as claimed in any one of claims 1 to 6 on a current collector and then drying it.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the positive electrode sheet as claimed in claim 9.

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