Suspension stabilizer as well as preparation method and application thereof

Abstract

The invention provides a suspension stabilizer and a preparation method and application thereof, the suspension stabilizer comprises an organic salt compound, and the organic salt compound comprises substituted or unsubstituted bipyridine and anions. According to the invention, the stability and dispersity of the negative electrode slurry can be improved.

Description

Technical Field

[0001] This invention relates to the field of materials, specifically to a suspension stabilizer, its preparation method, and its application. Background Technology

[0002] Lithium-ion rechargeable batteries possess advantages such as high single-cell voltage, high energy density, long cycle life, low self-discharge rate, no memory effect, and no pollution. They are currently widely used in portable consumer electronics, new energy electric vehicles, and energy storage. In recent years, the market demand for batteries for electric vehicles and energy storage has been continuously increasing, placing higher demands on the performance of lithium-ion rechargeable batteries.

[0003] To further improve the performance of lithium-ion secondary batteries, the manufacturing process can be optimized. The slurry preparation process is the first and most crucial step in lithium-ion secondary battery manufacturing. The slurry (such as the negative electrode slurry) prepared in the slurry preparation process directly affects the performance of the lithium-ion secondary battery. For example, the dispersibility and stability of the slurry (such as the negative electrode slurry) affect the performance of the coating in the electrode, and thus the electrochemical performance of the lithium-ion secondary battery. The dispersibility and stability of existing negative electrode slurries still need further improvement.

[0004] Therefore, how to further improve the dispersibility and stability of slurries (such as negative electrode slurries) is a research hotspot in the field. Summary of the Invention

[0005] This invention provides a suspension stabilizer, its preparation method, and its application, which helps to further improve the dispersibility and stability of slurries (such as negative electrode slurries).

[0006] The present invention provides a suspension stabilizer comprising an organic salt compound, wherein the organic salt compound comprises substituted or unsubstituted bipyridine and anion.

[0007] Optionally, the anion includes one or more of halide ions and carboxyl groups; preferably, the halide ion includes one or more of fluoride ions, chloride ions, bromide ions, and iodide ions; preferably, the structural formula of the organic salt compound is shown in Formula 1.

[0008]

[0009] In Formula 1, P and Q each independently include one or more of halide ions and carboxyl groups; R1 and R2 each independently include one or more of hydrogen, substituted or unsubstituted aryl groups, halogens, and carboxyl groups; R3 to R... 10 Each of the above-mentioned compounds independently includes one or more of hydrogen and alkanes having 1 to 3 carbon atoms; preferably, the substituted or unsubstituted aryl group includes one or more of phenyl, nitro-substituted phenyl, and amino-substituted phenyl.

[0010] Optionally, the organic salt compound includes one or more of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride and 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride.

[0011] The present invention provides a method for preparing the suspension stabilizer as described above, comprising: providing a first raw material comprising the substituted or unsubstituted bipyridine, and providing a second raw material comprising the anion; reacting the first raw material system comprising the first raw material and the second raw material to obtain the organic salt compound; and mixing the second raw material system comprising the organic salt compound to obtain the suspension stabilizer.

[0012] Optionally, the bipyridine comprises 4,4'-bipyridine; and / or, the second raw material comprises 2,4-dinitrochlorobenzene and / or 4-aminobenzene.

[0013] The present invention provides a negative electrode slurry, the negative electrode slurry comprising a negative electrode active material, a suspension stabilizer as described above, or the suspension stabilizer obtained according to the preparation method described above.

[0014] Optionally, the negative electrode slurry comprises dry matter, and the suspending stabilizer comprises 0.5% to 1.5% by mass in the dry matter; and / or, the negative electrode active material comprises one or more of natural graphite, artificial graphite, mesophase carbon microspheres, silicon / carbon composite material, tin / carbon composite material, hard carbon, and lithium carbonate.

[0015] The present invention provides a method for preparing the negative electrode slurry as described above, comprising: uniformly mixing a third raw material system including a negative electrode active material and a suspension stabilizer to obtain the negative electrode slurry, wherein the suspension stabilizer includes the suspension stabilizer as described above or the suspension stabilizer obtained according to the preparation method described above.

[0016] Optionally, the third raw material system further includes a conductive agent, a dispersant, a binder, and a solvent; preferably, the preparation method of the negative electrode slurry specifically includes: (1) mixing the negative electrode active material, the conductive agent, the dispersant, and the suspension stabilizer, and then performing a first stirring at a speed of 500-1000 rpm and a second stirring at a speed of 20-80 rpm to obtain a first process material; (2) adding a portion of the solvent to the first process material and performing a third stirring at a speed of 20-80 rpm to obtain a second process material; (3) adding a portion of the binder to the second process material and performing a fourth stirring at a speed of 20-80 rpm, and then kneading to obtain a kneaded third process material; (4) adding the remaining solvent to the third process material, and then performing a fifth stirring at a speed of 500-1000 rpm and a sixth stirring at a speed of 20-80 rpm to obtain a fourth process material; (5) adding the remaining binder to the fourth process material and performing a seventh stirring at a speed of 20-80 rpm to obtain a negative electrode slurry.

[0017] The present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active material layer located on at least one functional surface of the negative current collector, the negative active material layer comprising a suspension stabilizer as described above or the suspension stabilizer obtained according to the preparation method described above.

[0018] This invention provides a suspension stabilizer, its preparation method, and its application. The suspension stabilizer has a charged conjugated system, which can improve the stability of the slurry system through π-π stacking interaction, and can effectively disperse the components (such as negative electrode active materials) in the slurry through electrostatic repulsion interaction, thereby improving the slurry dispersion performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine provided in the embodiments of the present invention 1 H NMR spectrum. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To improve the dispersibility and stability of slurries (such as negative electrode slurries), existing technologies add a large amount of sodium carboxymethyl cellulose (CMC) to the slurry system, such as wet homogenizing sodium carboxymethyl cellulose (CMC) with styrene-butadiene rubber (SBR). However, a large amount of CMC can cause the electrode to become hard and brittle, which limits the processing window of the electrode.

[0023] To overcome the deficiencies in the prior art, embodiments of the present invention provide a suspension stabilizer, which includes an organic salt compound, comprising substituted or unsubstituted bipyridine and anions.

[0024] According to research and analysis, there is an interaction between the nitrogen atom and the anion in substituted or unsubstituted bipyridine, which makes the nitrogen atom in the substituted or unsubstituted bipyridine positively charged. This gives the organic salt compound (or suspension stabilizer) a certain electrostatic effect, which can improve the dispersibility of the slurry through electrostatic repulsion. At the same time, the substituted or unsubstituted bipyridine has a conjugated system, which can improve the stability of the slurry through π-π stacking. Therefore, the suspension stabilizer of the present invention helps to improve the dispersibility and stability of slurries (such as negative electrode slurries).

[0025] In this embodiment of the invention, the negative electrode slurry exhibits excellent dispersibility, specifically manifested in its small fineness and short sieving time; the negative electrode slurry also exhibits excellent stability, manifested in its excellent kinetic stability and low viscosity rebound.

[0026] Because the aforementioned suspension stabilizers (dispersing stabilizers) can improve the dispersibility of slurries (such as negative electrode slurries), the slurries (such as negative electrode slurries) have smaller fineness and shorter sieving time. They can also improve the stability of slurries (such as negative electrode slurries), resulting in excellent kinetic stability and low viscosity rebound. Therefore, the amount of sodium carboxymethyl cellulose (CMC) can be reduced, thereby avoiding problems such as hard and brittle electrodes and narrow processing windows caused by excessive use of sodium carboxymethyl cellulose (CMC).

[0027] Understandably, the aforementioned suspension stabilizer can improve the dispersibility and stability of the slurry. The slurry (such as the negative electrode slurry) has advantages such as small fineness, short sieving time, excellent kinetic stability, and low viscosity rebound. The aforementioned slurry may include negative electrode slurry for lithium-ion secondary batteries or negative electrode slurry for sodium-ion secondary batteries. The suspension stabilizer improves the stability of the aforementioned negative electrode slurry through π-π stacking effect, and at the same time effectively disperses the negative electrode active material through electrostatic repulsion interaction, thereby improving the dispersibility of the negative electrode slurry.

[0028] Substituted or unsubstituted bipyridines possess a large benzene ring conjugated system, which enhances the stability of the slurry through π-π stacking.

[0029] The aforementioned anions may include one or more of halide ions and carboxyl groups.

[0030] The aforementioned anions approach the nitrogen atoms in substituted or unsubstituted bipyridine, attracting electrons from the nitrogen atoms and giving them a positive charge. This imparts a certain electrostatic effect to the organic salt compound (or suspension stabilizer), thereby improving the dispersibility of the slurry through electrostatic repulsion.

[0031] It is understood that the halide ions mentioned above include one or more of fluoride ions, chloride ions, bromide ions, and iodide ions, with chloride ions being preferred.

[0032] Furthermore, the structural formula of the organic salt compound can be as shown in Formula 1.

[0033]

[0034] In Formula 1, P and Q each independently include one or more of halide ions and carboxyl groups; R1 and R2 each independently include one or more of hydrogen, substituted or unsubstituted aryl groups, halogens, and carboxyl groups; R3 to R... 10 Each independently includes one or more of hydrogen and alkanes having 1 to 3 carbon atoms.

[0035] As mentioned above, the halide ions may include one or more of fluoride ions, chloride ions, bromide ions, and iodide ions, with fluoride ions being preferred.

[0036] The substituted or unsubstituted aryl group may include one or more of phenyl, nitro-substituted phenyl, and amino-substituted phenyl.

[0037] Preferably, the substituted or unsubstituted aryl group includes an amino-substituted phenyl group. The amino-substituted phenyl group has a strong electron-donating effect, which can enhance the π-π stacking of organic salt compounds, contributing to further improvement in the stability and dispersibility of the slurry. The slurry (such as a negative electrode slurry) has advantages such as smaller fineness, shorter sieving time, excellent kinetic stability, and low viscosity rebound.

[0038] In some embodiments, the organic salt compound includes one or more of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride and 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride.

[0039] The present invention also provides a method for preparing the above-mentioned suspension stabilizer, comprising: providing a first raw material including substituted or unsubstituted bipyridine, and providing a second raw material including an anion; reacting the first raw material system including the first raw material and the second raw material to obtain an organic salt compound; and mixing the second raw material system including the organic salt compound to obtain the suspension stabilizer.

[0040] The above preparation method is simple to operate and can be used to prepare the above suspension stabilizer. The suspension stabilizer helps to improve the dispersibility and stability of slurry (such as negative electrode slurry). The slurry (such as negative electrode slurry) has advantages such as small fineness, short sieving time, excellent kinetic stability and low viscosity rebound.

[0041] In some embodiments, bipyridine includes 4,4'-bipyridine. 4,4'-bipyridine can form a conjugated matrix of organic salt compounds, giving the organic salt compounds a strong π-π stacking effect, which helps to further improve the stability of the slurry.

[0042] In some embodiments, the second raw material includes 2,4-dinitrochlorobenzene and / or 4-aminobenzene.

[0043] Specifically, bipyridine includes 4,4'-bipyridine, and the second raw material includes 2,4-dinitrochlorobenzene. Therefore, 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine can be prepared by the above preparation method.

[0044] Furthermore, 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine can be prepared using 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride.

[0045] In some embodiments, the process of reacting a first raw material system comprising a first raw material and a second raw material to obtain an organic salt compound may include: reacting a first raw material system comprising 4,4'-bipyridine and 2,4-dinitrochlorobenzene to obtain 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride, and then reacting 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride with p-phenylenediamine to obtain 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride.

[0046] For example, the above-described process for preparing 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine includes at least the following steps: mixing 4,4'-bipyridine, 2,4-dinitrochlorobenzene, and a solvent (such as ethanol), reacting at 80°C ± 5°C for 1 day ± 0.2 days, then cooling to room temperature (such as 20–25°C), filtering to obtain a crude product, and then washing the crude product (such as with ethanol and acetone) to obtain a pale yellow powdery intermediate compound, i.e., 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine. - bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride; the intermediate compound was dissolved in a solvent (such as ethanol), and then p-phenylenediamine was added. The mixture was then reacted (refluxed) at 70℃±5℃ for 2 days±0.2 days, and then cooled to room temperature (such as 20~25℃). The crude product was filtered and washed (such as with tetrahydrofuran), and then dried under vacuum to obtain a brownish-red powder, which is 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride.

[0047] This invention also provides a negative electrode slurry, which includes a negative electrode active material, the above-mentioned suspension stabilizer, or a suspension stabilizer obtained according to the above preparation method.

[0048] Based on this suspension stabilizer, the above-mentioned negative electrode slurry has high stability and dispersibility, small fineness, short sieving time, and excellent kinetic stability and low viscosity rebound.

[0049] The negative electrode active material may include one or more of the following: natural graphite, artificial graphite, mesophase carbon microspheres, silicon / carbon composite material, tin / carbon composite material, hard carbon, and lithium carbonate.

[0050] It is understood that the aforementioned negative electrode slurry may also include one or more of the following: conductive agent, binder, solvent, and dispersant.

[0051] Conductive agents may include one or more of the following: conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene.

[0052] The adhesive may include one or more of polyacrylic acid (PAA) and styrene-butadiene rubber (SBR).

[0053] Solvents may include water.

[0054] Dispersants may include sodium carboxymethyl cellulose (CMC).

[0055] Understandably, negative electrode slurry includes dry matter. Dry matter refers to the components in the negative electrode slurry other than the solvent. The negative electrode slurry can be dried to remove the solvent, and the remaining components are the dry matter.

[0056] In some embodiments, the mass percentage of the suspension stabilizer in the dry matter is 0.5% to 1.5%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or any combination thereof.

[0057] Preferably, the negative electrode slurry includes a negative electrode active material, a conductive agent, sodium carboxymethyl cellulose, PAA, SBR, a suspension stabilizer, and a solvent, wherein the mass ratio of the negative electrode active material, the conductive agent, sodium carboxymethyl cellulose, PAA, and SBR can be (95-97.0):(0.5-1.5):(0.4-1.5):(1.0-3.0):(0.5-1.5).

[0058] Based on the total mass of the negative electrode active material, conductive agent, sodium carboxymethyl cellulose, PAA, and SBR as 100%, the mass ratio of the suspension stabilizer is 0.5%-1.5%.

[0059] Furthermore, the solid content of the negative electrode slurry can be 45%-60%, for example, 45%, 50%, 55%, 60%, or any combination thereof. Here, the solid content of the negative electrode slurry refers to the mass percentage of non-volatile components (solid components) in the negative electrode slurry.

[0060] The preparation process (slurry homogenization process) of negative electrode slurry can directly (intuitively) affect the dispersibility and stability of negative electrode slurry, the manufacturing process of negative electrode sheet and the performance of negative electrode sheet, and thus affect the electrochemical performance of battery. Specifically, negative electrode slurry with poor dispersibility and stability will lead to uneven distribution of various components in the negative electrode slurry and delamination after long-term standing. This will in turn affect the coating of the electrode sheet, resulting in defects, uneven thickness and other poor process consistency, further affecting the short-term performance of battery and greatly reducing the cycle life of battery.

[0061] This invention also provides a method for preparing a negative electrode slurry, comprising: uniformly mixing a third raw material system including a negative electrode active material and a suspension stabilizer to obtain a negative electrode slurry, wherein the suspension stabilizer includes the aforementioned suspension stabilizer or a suspension stabilizer obtained according to the aforementioned suspension stabilizer preparation method.

[0062] This suspension stabilizer enhances the stability of the negative electrode slurry through π-π stacking and effectively disperses the active material of the negative electrode through electrostatic repulsion, thereby improving the dispersibility of the negative electrode slurry.

[0063] The above-mentioned method for preparing negative electrode slurry is simple to operate and can effectively improve the stability and dispersibility of negative electrode slurry.

[0064] In some embodiments, the third raw material system described above further includes one or more of a conductive agent, a binder, a solvent, and a dispersant.

[0065] Preferably, the preparation method of the above-mentioned negative electrode slurry specifically includes the following steps:

[0066] (1) After mixing the negative electrode active material, conductive agent, dispersant and suspension stabilizer, the mixture is stirred for the first time at a speed of 500-1000 rpm and then stirred for the second time at a speed of 20-80 rpm to obtain the first process material;

[0067] (2) Add some solvent to the material of the first process and stir for the third time at a speed of 20-80 rpm to obtain the material of the second process;

[0068] (3) Add some binder to the material of the second process and stir it for the fourth time at a speed of 20-80 rpm, and then knead it to obtain the material of the third process after kneading.

[0069] (4) Add the remaining solvent to the material of the third process, and then stir for the fifth time at a speed of 500-1000 rpm and for the sixth time at a speed of 20-80 rpm to obtain the material of the fourth process;

[0070] (5) Add the remaining binder to the material in the fourth process and stir it for the seventh time at a speed of 20-80 rpm to obtain the negative electrode slurry.

[0071] In the prior art, the negative electrode active material, conductive agent, and dispersant (such as sodium carboxymethyl cellulose) are dry-mixed, then a large amount of water and binder are added and kneaded, and then water is added to disperse and slurry to obtain the negative electrode slurry. Compared with the above-mentioned prior art, the preparation method of the present invention adds a suspension stabilizer in step (1). The suspension stabilizer improves the stability of the above negative electrode slurry through π-π stacking effect, and effectively disperses the negative electrode active material (negative electrode active material) through electrostatic repulsion interaction. This helps to reduce the amount of dispersant (such as sodium carboxymethyl cellulose), and can effectively improve the dispersibility and stability of the negative electrode slurry. The negative electrode slurry has advantages such as small fineness, short sieving time, excellent kinetic stability and low viscosity rebound.

[0072] Specifically, in step (1), the stirring time can be 5 to 20 minutes to ensure that the materials are mixed evenly.

[0073] In addition, in practical applications, the main stirring paddle of the homogenizer can be used for secondary stirring (or low-speed stirring), while the auxiliary stirring paddle of the homogenizer can be used for primary stirring (or high-speed stirring).

[0074] In step (2), the third stirring time is 5 to 20 minutes.

[0075] The percentage of the mass of the solvent in step (2) to the sum of the masses of the solvents in steps (2) and (4) can be 15% to 40%.

[0076] In step (3), the fourth stirring time can be 40 to 90 minutes to make the material and binder mix evenly, so that the material reaches a suitable kneading state.

[0077] After step (3) above is completed, scraping can be performed to ensure that all materials are fully mixed and processed.

[0078] In step (4), the stirring time can be 40 to 90 minutes.

[0079] The percentage of the mass of the solvent in step (4) relative to the sum of the masses of the solvents in steps (2) and (4) can be 60% to 85%.

[0080] In step (5), the seventh stirring time is 10 to 50 minutes.

[0081] In step (5), after the seventh stirring, the material can be vacuumed and sieved to obtain the negative electrode slurry.

[0082] In practice, since stirring generates heat, the material needs to be cooled after stirring is completed.

[0083] This invention also provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the functional surface of the negative electrode current collector. The negative electrode active material layer includes the above-mentioned suspension stabilizer or a suspension stabilizer obtained according to the above preparation method.

[0084] Specifically, the above-mentioned negative electrode sheet can be prepared by a method including at least the following process: after the negative electrode slurry is treated with water to adjust its viscosity, it is uniformly coated on the current collector (such as copper foil) to form a coating, and then dried and rolled to obtain the negative electrode sheet.

[0085] The above-mentioned negative electrode slurry is treated by adding water to adjust its viscosity so that it meets the normal coating requirements, such as ensuring that the coating on the negative electrode sheet has no obvious appearance defects (such as black spots, scratches, etc.).

[0086] This invention also provides a secondary battery, including the aforementioned negative electrode sheet.

[0087] As can be imagined, the secondary battery of this invention, in addition to the aforementioned negative electrode, also includes a positive electrode, an electrolyte, and a separator.

[0088] The embodiments of the present invention are not strictly limited to the positive electrode active material in the positive electrode sheet, and can be the positive electrode active material commonly used in lithium-ion batteries.

[0089] The embodiments of the present invention do not strictly limit the selection of electrolyte, and may include one or more of the solvents commonly used in lithium-ion battery electrolytes, as well as the electrolyte sodium salts commonly used in sodium-ion electrolytes. For example, the solvent may be ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, methyl ethyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc.; the electrolyte may be one or more of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium bis(fluorosulfonyl)imide, and sodium fluorotrifluoromethanesulfonylimide.

[0090] The embodiments of the present invention do not strictly limit the choice of separator material. It can be one of the separator materials commonly used in lithium-ion batteries, such as polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun separator (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven separator, and separator with ceramic coating.

[0091] In the preparation of secondary batteries (lithium-ion batteries), the positive electrode sheet, separator, and negative electrode sheet are wound or stacked to obtain a bare cell, which is then packaged into a pre-stamped aluminum-plastic film bag. After the packaged battery is dried, the electrolyte is injected into the dried battery. The battery is then left to stand, formed, and resealed to complete the preparation of the secondary battery.

[0092] This invention also provides an electrical device, including the aforementioned secondary battery.

[0093] The present invention will be further described below through specific embodiments and comparative examples. Unless otherwise specified, the reagents, materials and instruments used below are all conventional reagents, materials and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthetic methods.

[0094] Preparation Examples 1 to 2

[0095] Preparation Example 1

[0096] Synthesis of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride

[0097] 4,4'-Bipyridine (5.62 g, 36 mmol) and 2,4-dinitrochlorobenzene (17 g, 84 mmol) were added to a round-bottom flask equipped with a magnetic stirrer, and then 70 mL of ethanol was added and mixed. The mixture was reacted at 80 °C (reflux) for 1 day. After cooling to room temperature, the crude product was obtained by filtration. The crude product was then washed with ethanol and acetone to obtain a pale yellow powder, namely 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride.

[0098] Preparation Example 2

[0099] Synthesis of 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride

[0100] The 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride (1.2 g, 2.13 mmol) obtained in Preparation Example 1 was dissolved in 70 mL of ethanol, and then p-phenylenediamine (462 mg, 4.27 mmol) was added. The mixture was then refluxed at 70 °C for 2 days, cooled to room temperature, filtered, washed with tetrahydrofuran, and then dried under vacuum to obtain a brownish-red powder, namely 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride.

[0101] The product obtained in Preparation Example 2 was subjected to... 1H NMR spectroscopy was performed on a Bruker DRX spectrometer (600 MHz). The sample was dissolved in deuterated reagent D2O, and tetramethylsilane (TMS) was used as an internal standard. The results are shown in [Figure number missing]. Figure 1 .

[0102] Examples 1 to 4

[0103] Example 1

[0104] The preparation of the negative electrode slurry includes:

[0105] (1) Graphite QC-8, conductive carbon black SP, sodium carboxymethyl cellulose and 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine from Preparation Example 2 were added to a homogenizer for mixing. At the same time, the main stirring paddle was slowly stirred at 50 rpm and the auxiliary stirring paddle was quickly stirred at 800 rpm for 10 min to make the materials evenly mixed and obtain the first process material.

[0106] (2) Add some water to the material in the first process and stir at 50 rpm for 10 min to initially wet the material and obtain the material in the second process.

[0107] (3) Add polyacrylic acid (PAA) to the material of the second process and stir at 50 rpm for 60 min to keep the material in a good moist state. Knead the mixture to obtain the material of the third process after kneading.

[0108] (4) After adding the remaining water to the material of the third process, the main stirring paddle is slowly stirred at a speed of 50 rpm and the auxiliary stirring paddle is quickly stirred at a speed of 2500 rpm for 60 minutes to obtain the material of the fourth process.

[0109] (5) Add styrene-butadiene rubber (SBR) to the material in the fourth process and stir at 50 rpm for 30 min. Cool the material and then vacuum and sieve it to obtain the negative electrode slurry.

[0110] In this process, the mass percentage of the water in step (2) is 40% of the total mass of the water in step (2) and the remaining water in step (4). The negative electrode slurry includes 95.0 parts by mass of graphite QC-8, 1.5 parts by mass of conductive carbon black SP, 0.5 parts by mass of sodium carboxymethyl cellulose, 1.5 parts by mass of PAA, 1.5 parts by mass of SBR, 1.5 parts by mass of 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine from Preparation Example 2, with the balance being water, and the solid content of the negative electrode slurry is 50.39%.

[0111] Example 2

[0112] The preparation of the negative electrode slurry includes:

[0113] (1) Graphite QCG-X, conductive carbon black SP, sodium carboxymethyl cellulose and 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine from Preparation Example 2 were added to a homogenizer for mixing. At the same time, the main stirring paddle was slowly stirred at a speed of 20 rpm and the auxiliary stirring paddle was quickly stirred at a speed of 1000 rpm for 20 min to make the materials evenly mixed and obtain the first process material.

[0114] (2) Add some water to the material in the first process and stir at 20 rpm for 20 min to initially wet the material and obtain the material in the second process.

[0115] (3) Add polyacrylic acid (PAA) to the material of the second process and stir at 20 rpm for 90 min to keep the material in a good moist state. Knead the mixture to obtain the material of the third process after kneading.

[0116] (4) After adding the remaining water to the material of the third process, the main stirring paddle is slowly stirred at a speed of 20 rpm and the auxiliary stirring paddle is quickly stirred at a speed of 4000 rpm for 90 minutes to obtain the material of the fourth process.

[0117] (5) Add styrene-butadiene rubber (SBR) to the material in the fourth process and stir at 20 rpm for 50 min. Cool the material and then vacuum and sieve it to obtain the negative electrode slurry.

[0118] In this process, the mass percentage of the water in step (2) is 25% of the total mass of the water in step (2) and the remaining water in step (4). The negative electrode slurry includes 96.5 parts by mass of graphite QC-X, 0.5 parts by mass of conductive carbon black SP, 1 part by mass of sodium carboxymethyl cellulose, 1.5 parts by mass of PAA, 0.5 parts by mass of SBR, 1.0 parts by mass of 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine from Preparation Example 2, with the balance being water, and the solid content of the negative electrode slurry is 52.49%.

[0119] Example 3

[0120] The preparation of the negative electrode slurry includes:

[0121] (1) Graphite FSN-1, conductive carbon black SP, sodium carboxymethyl cellulose and 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine from Preparation Example 2 were added to a homogenizer for mixing. At the same time, the main stirring paddle was slowly stirred at 80 rpm and the auxiliary stirring paddle was quickly stirred at 500 rpm for 5 minutes to make the materials evenly mixed and obtain the first process material.

[0122] (2) Add some water to the material in the first process and stir at 80 rpm for 5 minutes to initially wet the material and obtain the material in the second process.

[0123] (3) Add polyacrylic acid (PAA) to the material of the second process and stir at 80 rpm for 40 min to keep the material in a good moist state. Knead the material to obtain the kneaded material of the third process.

[0124] (4) After adding the remaining water to the material of the third process, the main stirring paddle is slowly stirred at a speed of 80 rpm and the auxiliary stirring paddle is quickly stirred at a speed of 2000 rpm for 40 minutes to obtain the material of the fourth process.

[0125] (5) Add styrene-butadiene rubber (SBR) to the material in the fourth process and stir at 80 rpm for 10 min. Cool the material and then vacuum and sieve it to obtain the negative electrode slurry.

[0126] In this process, the mass percentage of the water in step (2) is 15% of the total mass of the water in step (2) and the remaining water in step (4). The negative electrode slurry includes 97.0 parts by mass of graphite FSN-1, 0.5 parts by mass of conductive carbon black SP, 1.5 parts by mass of sodium carboxymethyl cellulose, 0.5 parts by mass of PAA, 0.5 parts by mass of SBR, 0.5 parts by mass of 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine from Preparation Example 2, with the balance being water, and the solid content of the negative electrode slurry is 50.80%.

[0127] Example 4

[0128] This comparative example is basically the same as Example 1, except that:

[0129] The 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride of Preparation Example 2 was replaced with 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride of Preparation Example 1; all other conditions remained unchanged.

[0130] Comparative Examples 1 to 3

[0131] Comparative Example 1

[0132] This comparative example is basically the same as Example 1, except that:

[0133] The 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine in Preparation Example 2 was replaced with polyacrylamide; all other conditions remained unchanged.

[0134] The solid content of the negative electrode slurry in Comparative Example 1 was 50.57%.

[0135] Comparative Example 2

[0136] This comparative example is basically the same as Example 1, except that:

[0137] The 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine in Preparation Example 2 was replaced with 4,4'-bipyridine; all other conditions remained unchanged.

[0138] Comparative Example 3

[0139] This comparative example is basically the same as Example 1, except that:

[0140] The 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-dichlorinated bipyridine in Preparation Example 2 was replaced with ammonium chloride; all other conditions remained unchanged.

[0141] Test case

[0142] The following parameters of the negative electrode slurry in each embodiment and comparative example were tested:

[0143] Solid content of negative electrode slurry: The negative electrode slurry is placed in an oven for drying to obtain solid components. The mass percentage of solid components in the negative electrode slurry is calculated, which is the solid content of the negative electrode slurry. The drying temperature is 150℃ and the drying time is greater than 1 hour to remove solvents and other liquid components from the negative electrode slurry.

[0144] Viscosity of negative electrode slurry: The viscosity of negative electrode slurry was tested using a viscometer at a temperature of 25°C, using a 64# rotor, and the viscometer rotated at 12 r.

[0145] Fineness of negative electrode slurry: The fineness of the negative electrode slurry is tested using a scraper fineness meter.

[0146] Screening time of negative electrode slurry: Filter the negative electrode slurry using a 150-mesh sieve and record the time required for the negative electrode slurry to completely pass through the sieve. This is the screening time of the negative electrode slurry.

[0147] Kinetic instability of negative electrode slurry: The negative electrode slurry was tested using a multiple light scattering instrument to obtain a first baseline (the horizontal axis is time and the vertical axis is backscattered light intensity). Then, the negative electrode slurry was tested every 30 minutes until the negative electrode slurry that had been placed for 24 hours (i.e., the 48th 30-minute interval) was tested to obtain a second baseline (the horizontal axis is time and the vertical axis is backscattered light intensity). The difference between the second baseline and the first baseline was summed, and the calculated sum value was used to characterize the kinetic instability of the negative electrode slurry. The smaller the value, the more stable the kinetics of the negative electrode slurry.

[0148] The adhesion of the negative electrode sheet: After the negative electrode slurry is treated with water to adjust the viscosity, it is evenly coated on the copper foil current collector to form a negative electrode active coating. After drying and rolling, the negative electrode sheet is obtained. Then, the adhesion of the negative electrode sheet can be obtained by using a tensile test to test the force required to separate the negative electrode active coating from the copper foil current collector.

[0149] The test results are shown in Table 1.

[0150] Table 1

[0151]

[0152] Data Analysis:

[0153] As can be seen from the test results in Table 1, the fineness of the negative electrode slurry in Example 1 of the present invention is smaller than that in Comparative Example 1, and the sieving time of the negative electrode slurry in Example 1 is significantly shorter than that in Comparative Example 1, indicating that the dispersibility of the negative electrode slurry in Example 1 is better than that in Comparative Example 1; and the value of the kinetic instability of the negative electrode slurry in Example 1 is smaller than that in Comparative Example 1, indicating that the kinetic stability of the negative electrode slurry in Example 1 is better.

[0154] In summary, the negative electrode homogenization process of this invention, by introducing the dispersant and stabilizer 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride, reduces the proportion of sodium carboxymethyl cellulose, resulting in a slurry with both good dispersibility and stability. The negative electrode slurry has advantages such as small fineness, short sieving time, excellent kinetic stability, and low viscosity rebound. There are no visible defects in subsequent processes, and the electrode adhesion has certain advantages.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A suspension stabilizer, characterized in that, The suspension stabilizer comprises organic salt compounds, including substituted or unsubstituted bipyridines and anions.

2. The suspension stabilizer according to claim 1, characterized in that, The anion includes one or more of halide ions and carboxyl groups; Preferably, the halide ion includes one or more of fluoride ions, chloride ions, bromide ions, and iodide ions; Preferably, the structural formula of the organic salt compound is shown in Formula 1. In Formula 1, P and Q each independently include one or more of halide ions and carboxyl groups; R1 and R2 each independently include one or more of hydrogen, substituted or unsubstituted aryl groups, halogens, and carboxyl groups; R3 to R... 10 Each independently includes one or more of hydrogen and alkanes having 1 to 3 carbon atoms; Preferably, the substituted or unsubstituted aryl group includes one or more of phenyl, nitro-substituted phenyl, and amino-substituted phenyl.

3. The suspension stabilizer according to claim 2, characterized in that, The organic salt compounds include one or more of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride and 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-bipyridine dichloride.

4. A method for preparing the suspension stabilizer according to any one of claims 1-3, characterized in that, include: A first raw material comprising the substituted or unsubstituted bipyridine is provided, and a second raw material comprising the anion is provided; The first raw material system, comprising the first raw material and the second raw material, is reacted to obtain the organic salt compound; The suspension stabilizer is obtained by mixing a second raw material system including the organic salt compound.

5. The method for preparing the suspension stabilizer according to claim 4, characterized in that, The bipyridine includes 4,4'-bipyridine; And / or, the second raw material includes 2,4-dinitrochlorobenzene and / or 4-aminobenzene.

6. A negative electrode slurry, characterized in that, The negative electrode slurry includes a negative electrode active material, a suspension stabilizer as described in any one of claims 1-3, or a suspension stabilizer obtained according to the preparation method described in claim 4 or 5.

7. The negative electrode slurry according to claim 6, characterized in that, The negative electrode slurry comprises dry matter, and the suspending stabilizer has a mass percentage content of 0.5% to 1.5% in the dry matter; And / or, the negative electrode active material includes one or more of the following: natural graphite, artificial graphite, mesophase carbon microspheres, silicon / carbon composite material, tin / carbon composite material, hard carbon, and lithium carbonate.

8. A method for preparing the negative electrode slurry according to claim 6 or 7, characterized in that, include: The third raw material system, comprising the negative electrode active material and the suspension stabilizer, is mixed uniformly to obtain the negative electrode slurry, wherein the suspension stabilizer comprises the suspension stabilizer according to any one of claims 1-3 or the suspension stabilizer obtained according to the preparation method of claim 4 or 5.

9. The method for preparing the negative electrode slurry according to claim 8, characterized in that, The third raw material system also includes one or more of the following: conductive agent, dispersant, binder, and solvent; Preferably, the method for preparing the negative electrode slurry specifically includes: (1) The negative electrode active material, the conductive agent, the dispersant and the suspension stabilizer are mixed and stirred for the first time at a speed of 500-1000 rpm and for the second time at a speed of 20-80 rpm to obtain the first process material; (2) Add a portion of solvent to the material in the first process and stir for the third time at a speed of 20-80 rpm to obtain the material in the second process; (3) Add some binder to the material in the second process and stir it for the fourth time at a speed of 20-80 rpm, and then knead it to obtain the kneaded material in the third process. (4) Add the remaining solvent to the material of the third process, and then stir for the fifth time at a speed of 500-1000 rpm and for the sixth time at a speed of 20-80 rpm to obtain the material of the fourth process; (5) Add the remaining binder to the material in the fourth process and stir it for the seventh time at a speed of 20-80 rpm to obtain the negative electrode slurry.

10. A negative electrode sheet, characterized in that, The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one side of the functional surface of the negative current collector. The negative active material layer includes the suspension stabilizer according to any one of claims 1-3 or the suspension stabilizer obtained according to the preparation method of claim 4 or 5.

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