CN118841574A - Dispersing agent, conductive agent slurry, positive electrode homogenate slurry, positive electrode plate and battery - Google Patents

Abstract

The present invention provides a dispersant, a conductive agent slurry, a positive electrode homogenized slurry, a positive electrode sheet and a battery. The dispersant can be used for conductive agent slurry and lithium battery positive electrode homogenized slurry. The dispersant provided by the present invention can achieve the dispersion of carbon materials, reduce the viscosity of conductive agent slurries of nano-carbon materials such as carbon nanotubes and graphene, improve the viscosity stability of conductive agent slurries, and ensure that the conductive agent slurry still has a low viscosity and maintains viscosity stability under the condition of high solid content; the dispersant provided by the present invention can also achieve the dispersion of positive electrode active materials whose surfaces are fully or partially covered with carbon materials, reduce the viscosity of positive electrode homogenized slurry, improve the stability of positive electrode homogenized slurry, and ensure that the positive electrode homogenized slurry still has a low viscosity and maintains viscosity stability under the condition of high solid content.

Description

Dispersant, conductive agent slurry, positive electrode homogenate slurry, positive electrode sheet and battery

Technical Field

The invention belongs to the technical field of dispersion, and relates to a dispersant for dispersing carbonaceous materials, in particular to a dispersant, a conductive agent slurry, a positive electrode homogenate slurry, a positive electrode plate and a battery.

Background Art

The premise for conductive carbon materials to build an efficient conductive network in secondary batteries is to achieve effective dispersion in the positive and negative active materials. At present, battery manufacturers mostly use double planetary stirring kettles in the process of positive and negative electrode slurry mixing. The main stirring shaft performs low-speed mixing, and the high-speed dispersion disk performs high-speed dispersion. The high-speed rotation shear dispersion is achieved while the low-speed revolution is performed simultaneously, so as to achieve uniform mixing of different components including the conductive agent in the positive and negative electrode slurry overshoot.

However, since carbon nanotubes and graphene are usually nanometer-sized, their huge surface energy leads to strong van der Waals forces between carbon nanotubes and graphene sheets, making it impossible for materials such as carbon nanotubes and graphene to disperse under the conditions of double planetary stirring. The end result is that the conductive agent cannot form an effective conductive network in the positive and negative electrodes, and may even cause brittle electrode sheets or abnormal local battery voltage due to local concentration of the conductive agent.

Based on this, in order to ensure the effective dispersion of nanostructured conductive agents such as carbon nanotubes and graphene in the positive and negative electrodes, it is necessary to adopt certain methods in advance to overcome the van der Waals force and achieve near-molecular-level mixing between nanocarbon materials such as carbon nanotubes and graphene and the dispersion medium.

To achieve the above purpose, the mainstream of the industry currently uses sand mills for grinding and dispersion, and uses the mechanical collision or shearing between the grinding beads in the sand mill to achieve the peeling between carbon nanotubes, graphene and conductive carbon black, and at the same time, with the help of the steric hindrance of the dispersant, the effective peeling between these nanostructured carbon materials is achieved and agglomeration is avoided, thereby preparing a conductive agent slurry. For example, patents CN108059151A, CN102695557A, CN105645377A, CN106517152A, CN108370037A and CN108883937A all propose dispersants of different structures, using the three-dimensional steric hindrance effect of the polymer to avoid the secondary agglomeration of nanocarbon materials. Patent CN205731098U proposes a method of dispersing conductive carbon materials using a high-speed dispersion disk, patents CN103700823A and CN104736475A use a sand milling dispersion method, CN105771762A proposes an ultrasonic method, and CN103189310A proposes a method using a high-pressure homogenizer.

The use of these methods and equipment has played a very good role in promoting the dispersion of nanocarbon materials and has achieved good dispersion effects. However, due to the huge forces between nanocarbon materials (including van der Waals forces, hydrogen bonds and physical entanglement), the viscosity of nanocarbon material slurry is still very high, especially the rapid increase in viscosity when placed, which causes great inconvenience to the client's use (such as positive electrode slurry dispersion). The high viscosity leads to low effective content and greatly increases transportation costs. Therefore, it is extremely urgent to reduce the viscosity of nanocarbon material slurries such as carbon nanotubes and graphene to facilitate the application of battery slurries, increase solid content and thus reduce transportation costs.

In addition, in the process of lithium battery homogenization, lithium iron phosphate or lithium iron manganese phosphate, etc., which are fully or partially covered with carbon materials on the surface, are used as the main positive electrode materials. They need to be mixed and homogenized with a binder such as PVDF (polyvinylidene fluoride) and a conductive agent (such as carbon black, the above-mentioned carbon nanotube slurry and graphene slurry, etc.) in NMP (N-methylpyrrolidone) according to a certain ratio and solid content requirements, and the slurry is further evenly coated on the aluminum foil current collector to prepare a pole piece. However, the size of lithium iron phosphate particles is small, and its primary particle structure is also nano-sized. The particle size of lithium iron manganese phosphate is even smaller. There is a huge van der Waals force between these nano-scale main material particles, which can easily cause the homogenization system to form a physical gel, resulting in abnormal coating in the next process. In particular, the pipeline used to transport the slurry, due to the rapid increase in the viscosity of the slurry due to standing, and then blocking the pipeline, causing great trouble for the continuous production of the battery production line. Therefore, it is extremely important to obtain a homogenized slurry with a stable viscosity for the stable and continuous production of the battery production line. In fact, after the positive electrode is coated, it needs to go through a drying process to volatilize the NMP on the electrode before entering the next process of battery manufacturing. However, the boiling point of NMP is as high as 205°C, and the energy consumption cost caused by the baking of NMP accounts for a large proportion of the entire battery manufacturing. Therefore, in recent years, various battery factories have chosen to increase the solid content of the slurry to reduce the proportion of NMP, so as to reduce energy consumption and thus reduce costs. However, increasing the solid content of the slurry means that the content of lithium iron phosphate or lithium iron manganese phosphate needs to be increased, which will inevitably cause the viscosity of the slurry to further increase. Therefore, reducing the viscosity of the slurry and increasing the solid content of the slurry are also extremely urgent to reduce the cost of battery manufacturing.

The currently disclosed carbon materials have poor dispersion effects, so there are problems such as high viscosity, poor stability of slurry viscosity and low solid content of slurry of nano-carbon materials such as carbon nanotubes and graphene; the currently disclosed positive electrode active materials with carbon materials fully or partially covered on the surface have poor dispersion effects, so there are problems such as high viscosity, poor stability of slurry viscosity and low solid content of positive electrode homogenized slurry. Therefore, it is very important to develop and design a new type of dispersant, conductive agent slurry and positive electrode homogenized slurry for dispersing carbon-containing materials.

Summary of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide a dispersant, a conductive agent slurry, a positive electrode homogenate slurry, a positive electrode plate and a battery. The dispersant provided by the present invention can achieve the dispersion of carbon materials, reduce the viscosity of the conductive agent slurry of nano-carbon materials such as carbon nanotubes and graphene, improve the viscosity stability of the conductive agent slurry, and ensure that the conductive agent slurry still has a low viscosity and maintains viscosity stability under a high solid content; the dispersant provided by the present invention can also achieve the dispersion of positive electrode active materials whose surfaces are fully or partially covered with carbon materials, reduce the viscosity of the positive electrode homogenate slurry, improve the stability of the positive electrode homogenate slurry, and ensure that the positive electrode homogenate slurry still has a low viscosity and maintains viscosity stability under a high solid content.

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

In a first aspect, the present invention provides a dispersant for dispersing carbonaceous materials, wherein the dispersant comprises ethylamine, diethylamine, ethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N-hydroxyethylethylenediamine, N,N'-bis(2-hydroxyethyl)ethylenediamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, butanediamine, hexanediamine, dicyclohexylamine, piperazine, N-methylpiperazine, N-ethylpiperazine, 1-amino-4-methylpiperazine, N-aminoethylpiperazine, piperidine, N-methylpiperidine, hexahydropyridazine, Hexahydrotrimethyl-S-triazine, ethanolamine, diethanolamine, 2-ethylaminoethanol, 2-methylaminoethanol, 3-amino-1,2-propylene glycol, tris(2-aminoethyl)amine, triethanolamine, n-propanolamine, isopropanolamine, diisopropanolamine, n-butanolamine, isobutanolamine, diisobutanolamine, tert-butanolamine, di-tert-butanolamine, hydrazine, cyanoethylhydrazine, methylhydrazine, hydroxymethylhydrazine, ethylhydrazine, hydroxyethylhydrazine, propylhydrazine, hydroxypropylhydrazine, butylhydrazine, phenylhydrazine, polyethylene glycol amine or any one of polyethylene glycol amine or a combination of at least two thereof.

Typical but non-limiting combinations of the dispersants in the present invention include a combination of ethylamine and diethylamine, a combination of ethylenediamine and N,N-dimethylethylenediamine, a combination of N,N-diethylethylenediamine and N-hydroxyethylethylenediamine, a combination of n-propylamine and isopropylamine, a combination of n-butylamine and isobutylamine, a combination of butanediamine and hexamethylenediamine, a combination of dicyclohexylamine and piperazine, a combination of N-methylpiperazine and N-ethylpiperazine, a combination of 1-amino-4-methylpiperazine and N-aminoethylpiperazine, a combination of 2-ethylaminoethanol and 2-methylaminoethanol, a combination of tert-butanolamine and di-tert-butanolamine, a combination of hydroxymethylhydrazine and ethylhydrazine, a combination of hydroxyethylhydrazine and propylhydrazine, a combination of propylhydrazine and hydroxypropylhydrazine, a combination of polyethylene glycol amine and dipolyethylene glycol amine, or a combination of phenylhydrazine, polyethylene glycol amine and dipolyethylene glycol amine.

In the preparation process of the conductive agent slurry containing carbon material, firstly, the dispersant provided by the present invention is used. The addition of the dispersant can adjust the surface tension of the conductive agent slurry, thereby improving the wettability of the carbon material in the dispersion medium; in addition, the hydrogen bonds generated between the dispersant and the surface of the carbon material are utilized so that the interaction between the dispersant and the carbon material can quickly overcome the van der Waals force between the carbon material itself, thereby promoting the improvement of the dispersion efficiency; secondly, the interaction between the dispersant and the carbon material also makes it impossible for the conductive agent slurry containing carbon material to reagglomerate either during preparation or in the subsequent placement process, which plays a great role in reducing the viscosity of the conductive agent slurry and stabilizing the viscosity of the slurry.

In the homogenization process of lithium batteries, firstly, the use of the dispersant provided by the present invention can not only reduce the viscosity of the homogenate and stabilize the viscosity of the homogenate, but also show an extremely efficient effect in improving the solid content of the homogenate; secondly, the interaction between the surface-rich groups of the positive electrode active material whose surface is fully or partially covered with carbon material and the additive enables the dispersant to be quickly adsorbed on the surface of the positive electrode active material, thereby improving the wettability of the positive electrode active material in the dispersion medium and reducing the interaction between the particles of the positive electrode active material, thereby reducing and stabilizing the viscosity of the homogenate, and avoiding the huge van der Waals force between the particles of the positive electrode active material after homogenization, which causes the viscosity of the homogenate system to rise rapidly, causing trouble for subsequent coating production.

The dispersant provided by the present invention can achieve the dispersion of carbon materials, reduce the viscosity of conductive agent slurries of nano-carbon materials such as carbon nanotubes and graphene, improve the viscosity stability of the conductive agent slurry, and ensure that the conductive agent slurry still has a low viscosity and maintains viscosity stability under the condition of a high solid content; the dispersant provided by the present invention can also achieve the dispersion of positive electrode active materials whose surfaces are fully or partially covered with carbon materials, reduce the viscosity of positive electrode homogenate slurry, improve the stability of positive electrode homogenate slurry, and ensure that the positive electrode homogenate slurry still has a low viscosity and maintains viscosity stability under the condition of a high solid content.

Preferably, the carbon-containing material includes a carbon material, and/or a positive electrode active material whose surface is fully or partially covered with a carbon material.

Preferably, the carbon material includes any one of carbon nanotubes, graphene, conductive carbon black or graphite whiskers, or a combination of at least two of them. Typical but non-limiting combinations include a combination of carbon nanotubes and graphene, a combination of conductive carbon black and graphite whiskers, or a combination of carbon nanotubes, graphene and conductive carbon black.

Preferably, the carbon nanotubes include any one of multi-walled carbon nanotubes, oligo-walled carbon nanotubes, single-walled carbon nanotubes or shaped carbon nanotubes, or a combination of at least two of them. Typical but non-limiting combinations include a combination of multi-walled carbon nanotubes and oligo-walled carbon nanotubes, a combination of single-walled carbon nanotubes and shaped carbon nanotubes, or a combination of multi-walled carbon nanotubes, oligo-walled carbon nanotubes and single-walled carbon nanotubes.

Preferably, the graphene includes any one or a combination of at least two of single-layer graphene, few-layer graphene or multi-layer graphene. Typical but non-limiting combinations include a combination of single-layer graphene and few-layer graphene, a combination of few-layer graphene and multi-layer graphene, or a combination of single-layer graphene, few-layer graphene and multi-layer graphene.

Preferably, the conductive carbon black comprises furnace black and/or acetylene black.

Preferably, the specific surface area of the conductive carbon black is 50 to 850 m ² /g, for example ^, it may be 50 m ² /g, 100 m ² /g, 150 m ² /g, 200 m ² /g, 250 m ² /g, 300 m ² /g, 350 m ² /g, 400 m ² /g, 450 m ² /g, 500 m ² /g, 550 m ² /g, 600 m ² /g, 650 m 2 /g, 700 m ² /g, 750 m ² /g, 800 m ² /g or 850 m ² /g, but is not limited to the listed values, and other values not listed within the numerical range are equally applicable.

Preferably, the positive electrode active material includes lithium iron phosphate and/or lithium iron manganese phosphate.

In a second aspect, the present invention provides a conductive agent slurry of a carbon material, wherein the conductive agent slurry comprises a carbon material and the dispersant described in the first aspect.

The conductive agent slurry provided by the present invention is dispersed by using currently commercialized dispersing equipment, such as a sand mill, a high-pressure homogenizer, and a ball mill.

Preferably, the mass fraction of the dispersant in the conductive agent slurry is 0.02-2wt%, for example, it can be 0.02wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, 1wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt% or 2wt%, but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the mass fraction of the dispersant in the conductive agent slurry is 0.05-1wt%, for example, it can be 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt% or 1wt%, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable, preferably 0.1-0.6wt%.

Preferably, the conductive agent slurry further includes a dispersion medium.

Preferably, the dispersion medium comprises any one of NMP, DMA, DMF or DMSO or a combination of at least two thereof, typical but non-limiting combinations include a combination of NMP and DMA, a combination of DMF and DMSO, or a combination of NMP, DMA and DMF, preferably NMP.

Preferably, the conductive agent slurry further comprises an auxiliary dispersant.

Preferably, the auxiliary dispersant includes any one of poly N-vinyl pyrrolidone, a modified polymer of poly N-vinyl pyrrolidone, polyvinyl alcohol, a modified polymer of polyvinyl alcohol, polyacrylate, a modified polymer of polyacrylate, polyvinylidene fluoride, a modified polymer of polyvinylidene fluoride, polyethylene glycol, a modified polymer of polyethylene glycol, hydrogenated nitrile rubber or a modified polymer of hydrogenated nitrile rubber, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of N-vinyl pyrrolidone and a modified polymer of poly N-vinyl pyrrolidone, a combination of polyvinyl alcohol and a modified polymer of polyvinyl alcohol, a combination of polyacrylate and a modified polymer of polyacrylate, a combination of a modified polymer of polyacrylate and polyvinylidene fluoride, a combination of polyethylene glycol and a modified polymer of polyethylene glycol, or a combination of a modified polymer of polyethylene glycol, hydrogenated nitrile rubber and a modified polymer of hydrogenated nitrile rubber.

In a third aspect, the present invention provides a positive electrode homogenate slurry, wherein the positive electrode homogenate slurry includes a positive electrode active material whose surface is fully or partially covered with a carbon material, and the dispersant described in the first aspect.

Preferably, the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.01 to 0.4 wt%, for example, it can be 0.01 wt%, 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.1 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt% or 0.4 wt%, but it is not limited to the listed values, and other values not listed within the numerical range are also applicable.

Preferably, the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.02-0.3wt%, for example, it can be 0.02wt%, 0.04wt%, 0.06wt%, 0.08wt%, 0.1wt%, 0.12wt%, 0.14wt%, 0.16wt%, 0.18wt%, 0.2wt%, 0.22wt%, 0.24wt%, 0.26wt%, 0.28wt% or 0.3wt%, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable, preferably 0.04-0.2wt%.

Preferably, the positive electrode homogenate slurry also includes a binder.

Preferably, the binder comprises any one of polyvinylidene fluoride, polyvinyl alcohol, hydrogenated nitrile rubber or polyacrylate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of polyvinylidene fluoride and polyvinyl alcohol, a combination of hydrogenated nitrile rubber and polyacrylate, a combination of polyvinylidene fluoride, polyvinyl alcohol and hydrogenated nitrile rubber, or a combination of polyvinyl alcohol, hydrogenated nitrile rubber and polyacrylate.

Preferably, the positive electrode homogenate slurry also includes a conductive agent.

Preferably, the conductive agent comprises carbon material and/or the conductive agent slurry described in the second aspect.

Preferably, the positive electrode homogenate slurry also includes a dispersion medium.

Preferably, the dispersion medium includes any one of NMP (N-methylpyrrolidone), methanol, ethanol, ethylene glycol, isopropanol, DMA (N,N-dimethylacetamide), DMF (N,N-dimethylformamide) or DMSO (dimethyl sulfoxide) or a combination of at least two thereof, and typical but non-limiting combinations include a combination of NMP and DMA, a combination of DMF and DMSO, or a combination of NMP, DMA and DMF, preferably NMP.

In a fourth aspect, the present invention provides a positive electrode plate, which is prepared by coating the positive electrode homogenate slurry described in the third aspect on a current collector.

In a fifth aspect, the present invention provides a battery, comprising the positive electrode plate described in the fourth aspect.

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

(1) In the preparation process of the conductive agent slurry containing carbon material, firstly, the dispersant provided by the present invention is used. The addition of the dispersant can adjust the surface tension of the conductive agent slurry, thereby improving the wettability of the carbon material in the dispersion medium; in addition, the hydrogen bonds generated between the dispersant and the surface of the carbon material are utilized so that the interaction between the dispersant and the carbon material can quickly overcome the van der Waals force between the carbon material itself, thereby promoting the improvement of the dispersion efficiency; secondly, the interaction between the dispersant and the carbon material also makes it impossible for the conductive agent slurry containing the carbon material to reagglomerate during the preparation or the subsequent placement process, which plays a great role in reducing the viscosity of the conductive agent slurry and stabilizing the viscosity of the slurry;

(2) In the homogenization process of lithium batteries, firstly, the use of the dispersant provided by the present invention can not only reduce the viscosity of the homogenate and stabilize the viscosity of the homogenate, but also show an extremely efficient effect in improving the solid content of the homogenate; secondly, the interaction between the surface-rich groups of the positive electrode active material whose surface is fully or partially covered with carbon material and the additive enables the dispersant to be quickly adsorbed on the surface of the positive electrode active material, thereby improving the wettability of the positive electrode active material in the dispersion medium and reducing the interaction between the particles of the positive electrode active material, thereby reducing and stabilizing the viscosity of the homogenate, and avoiding the huge van der Waals force between the particles of the positive electrode active material after homogenization, which causes the viscosity of the homogenate system to rise rapidly, causing trouble for the subsequent coating production.

DETAILED DESCRIPTION

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

Example 1

This embodiment provides a dispersant for dispersing a carbon-containing material, wherein the carbon-containing material is a carbon nanotube with a diameter of 7 to 15 nm; and the dispersant is ethylamine.

This embodiment also provides a conductive agent slurry of carbon material, wherein the conductive agent slurry includes the carbon nanotubes and the dispersant, wherein the mass fraction of the carbon material in the conductive agent slurry is 3.5wt%, and the mass fraction of the dispersant is 0.15wt%;

The conductive agent slurry also includes a dispersion medium NMP;

The conductive agent slurry further includes an auxiliary dispersant PVP with a mass fraction of 0.88 wt%.

The preparation method of the conductive agent slurry is: firstly, the auxiliary dispersant PVP is added to the dispersion medium NMP and stirred to dissolve, then the above-mentioned carbon nanotubes are added, and after stirring, the above-mentioned dispersant is added to obtain a mixed solution, and then the mixed solution is sent to a sand mill/high-pressure homogenizer/or ball mill for dispersion.

Example 2

This embodiment provides a dispersant for dispersing a carbon-containing material, wherein the carbon-containing material is a carbon nanotube with a diameter of 7 to 15 nm; and the dispersant is N,N-dimethylethylenediamine.

This embodiment further provides a conductive agent slurry of carbon material, wherein the conductive agent slurry includes the above-mentioned carbon nanotubes and the above-mentioned dispersant, wherein the mass fraction of the carbon material in the conductive agent slurry is 4.3wt%, and the mass fraction of the dispersant is 0.3wt%.

The conductive agent slurry also includes a dispersion medium NMP;

The conductive agent slurry further includes an auxiliary dispersant PVP with a mass fraction of 1.08 wt%.

The preparation method of the conductive agent slurry is: firstly, the auxiliary dispersant PVP is added to the dispersion medium NMP and stirred to dissolve, then the above-mentioned carbon nanotubes are added, and after stirring, the dispersant of the present invention is added to obtain a mixed solution, and then the mixed solution is sent to a sand mill/high-pressure homogenizer/or ball mill for dispersion.

Example 3

This embodiment provides a dispersant for dispersing a carbon-containing material, wherein the carbon material is graphene; and the dispersant is isopropanolamine.

This embodiment further provides a conductive agent slurry of carbon material, wherein the conductive agent slurry includes the above-mentioned carbon nanotubes and the above-mentioned dispersant, wherein the mass fraction of the carbon material in the conductive agent slurry is 3.5wt%, and the mass fraction of the dispersant is 0.3wt%.

The conductive agent slurry also includes a dispersion medium NMP;

The conductive agent slurry further includes an auxiliary dispersant PVP.

The preparation method of the conductive agent slurry is: firstly, the auxiliary dispersant PVP is added to the dispersion medium NMP and stirred to dissolve, then the above-mentioned graphene is added, and after stirring, the dispersant of the present invention is added to obtain a mixed solution, and then the mixed solution is sent to a sand mill/high-pressure homogenizer/or ball mill for dispersion.

Example 4

This embodiment provides a dispersant for dispersing a carbon-containing material, wherein the carbon-containing material includes lithium iron phosphate whose surface is partially covered with conductive carbon black; and the dispersant is hydroxyethyl hydrazine.

This embodiment also provides a positive electrode homogenate slurry, wherein the positive electrode homogenate slurry includes lithium iron phosphate whose surface is partially covered with conductive carbon black, and the above-mentioned dispersant;

The mass fraction of the dispersant in the positive electrode homogenate slurry is 0.05 wt %.

The positive electrode homogenate slurry also includes a binder PVDF 5130;

The positive electrode homogenate slurry also includes 1 wt% of conductive carbon black and 0.5 wt% of carbon nanotubes;

The positive electrode homogenate slurry also includes a dispersion medium, NMP.

The preparation method of the positive electrode homogenate slurry is:

After dissolving PVDF in NMP, add conductive agent conductive carbon black and carbon nanotubes, add lithium iron phosphate with the surface partially covered with conductive carbon black under stirring conditions for dispersion, the dispersant is added before the lithium iron phosphate with the surface partially covered with conductive carbon black is added, followed by stirring and dispersion.

Example 5

This embodiment provides a dispersant for dispersing a carbon-containing material, wherein the carbon-containing material includes lithium manganese iron phosphate whose surface is completely covered with graphene; and the dispersant is tert-butanolamine.

This embodiment also provides a positive electrode homogenate slurry, wherein the positive electrode homogenate slurry includes lithium manganese iron phosphate with the surface completely covered with graphene, and the above-mentioned dispersant;

The mass fraction of the dispersant in the positive electrode homogenate slurry is 0.3 wt %.

The positive electrode homogenate slurry also includes a binder PVDF 5130;

The positive electrode homogenate slurry also includes 1 wt% of conductive carbon black and 0.5 wt% of carbon nanotubes;

The positive electrode homogenate slurry also includes a dispersion medium, NMP.

After dissolving PVDF in NMP, add conductive agent conductive carbon black and carbon nanotubes, add lithium manganese iron phosphate with the surface completely covered with graphene under stirring conditions for dispersion, the dispersant is added after the lithium manganese iron phosphate with the surface completely covered with graphene is added, followed by stirring and dispersion.

Example 6

This embodiment provides a dispersant for dispersing a carbon-containing material, wherein the carbon-containing material includes lithium iron phosphate whose surface is partially covered with carbon nanotubes; and the dispersant is 2-ethylaminoethanol.

This embodiment also provides a positive electrode homogenate slurry, wherein the positive electrode homogenate slurry includes lithium iron phosphate whose surface is partially covered with carbon nanotubes, and the above-mentioned dispersant;

The mass fraction of the dispersant in the positive electrode homogenate slurry is 0.2 wt %.

The positive electrode homogenate slurry also includes a binder PVDF 5130;

The positive electrode homogenate slurry also includes 1 wt% of conductive carbon black and 0.5 wt% of carbon nanotubes;

The positive electrode homogenate slurry also includes a dispersion medium, NMP.

After PVDF is dissolved in NMP, conductive carbon black and carbon nanotubes are added, and lithium iron phosphate with a surface partially covered with carbon nanotubes is added under stirring to disperse, and the dispersant is added before the lithium iron phosphate with a surface partially covered with carbon nanotubes is added, followed by stirring and dispersion.

Example 7

This embodiment provides a dispersant for dispersing carbonaceous materials that is the same as that in embodiment 1;

This embodiment also provides a conductive agent slurry of carbon material, which is the same as that of embodiment 1 except that the mass fraction of the dispersant in the conductive agent slurry is 0.15wt% and the mass fraction of the dispersion medium NMP is reduced accordingly.

Example 8

This embodiment provides a dispersant for dispersing carbonaceous materials that is the same as that in embodiment 1;

This embodiment further provides a conductive agent slurry of carbon material, which is the same as that of embodiment 1 except that the mass fraction of the dispersant in the conductive agent slurry is 0.25wt% and the solid content of the conductive agent slurry is kept unchanged.

Example 9

This embodiment provides a dispersant for dispersing carbonaceous materials that is the same as that of embodiment 4;

This embodiment also provides a positive electrode homogenate slurry, which is the same as that of Embodiment 4 except that the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.05wt% and the mass fraction of the dispersion medium NMP is reduced accordingly.

Example 10

This embodiment provides a dispersant for dispersing carbonaceous materials that is the same as that of embodiment 4;

This embodiment further provides a positive electrode homogenate slurry, which is the same as that of Embodiment 4 except that the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.15wt% and the solid content of the positive electrode homogenate slurry is kept unchanged.

Embodiment 11

This embodiment provides a dispersant for dispersing carbonaceous materials that is the same as that in embodiment 1;

This embodiment also provides a conductive agent slurry of carbon material, which is the same as that of embodiment 1 except that the mass fraction of the dispersant in the conductive agent slurry is 0.01wt% and the solid content of the positive electrode slurry is kept unchanged.

Example 12

This embodiment provides a dispersant for dispersing carbonaceous materials that is the same as that of embodiment 4;

This embodiment further provides a positive electrode homogenate slurry, which is the same as that of Embodiment 4 except that the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.005wt% and the solid content of the positive electrode homogenate slurry is kept unchanged.

Comparative Example 1

This comparative example provides a conductive agent slurry of carbon material, which is the same as Example 1 except that the dispersant ethylamine in the conductive agent slurry is omitted.

Comparative Example 2

This comparative example provides a positive electrode homogenate slurry, which is the same as Example 4 except that the dispersant hydroxyethylhydrazine in the positive electrode homogenate slurry is omitted.

The viscosity of the conductive agent slurry of the carbon material provided in the above embodiment and the comparative example was tested, and the initial slurry viscosity was shown in Table 1; the conductive agent slurry provided in the above embodiment and the comparative example was placed for 7 days, and the viscosity obtained by testing was shown in Table 1;

The viscosity of the positive electrode homogenate slurry provided in the above embodiments and comparative examples was tested, and the initial viscosity after homogenization was obtained as shown in Table 2; the positive electrode homogenate slurry provided in the above embodiments and comparative examples was placed for 24 hours, and the viscosity obtained by testing was shown in Table 2.

Table 1

Table 2

From Table 1, we can get:

(1) The conductive agent slurry of the carbon material provided in Examples 1 to 3 of the present invention at the end of grinding and the positive electrode homogenate slurry provided in Examples 4 to 6 at the end of homogenization have low viscosities; in addition, the conductive agent slurry of the carbon material provided in Examples 1 to 3 and the positive electrode homogenate slurry provided in Examples 4 to 6 still have low viscosities after being placed for seven days and 24 hours respectively;

(2) By comparing Example 11 with Example 1, it can be seen that the dispersant content in the conductive agent slurry of the present invention affects the viscosity of the conductive agent slurry. When the dispersant content is low, its effect on the dispersion and viscosity reduction of the conductive agent slurry and the stability of the viscosity after placement is significantly weakened, and is even close to the result of no addition (Comparative Example 1); when the dispersant content is high, the dispersant's effect on promoting the dispersion of the conductive agent tends to be saturated, so continuing to increase the usage will not have much effect on reducing the viscosity. In addition, when the content is high, the interaction between the dispersant molecules and the action sites on the surface of the carbon material tends to be saturated, and excessive addition will not have much effect on reducing and stabilizing the viscosity. Therefore, from the perspective of actual cost, there is no need to continue to increase the addition amount. Similarly, by comparing Example 12 with Example 1, it can be seen that a similar phenomenon also occurs in the positive electrode homogenate slurry embodiment, that is, when the content of the dispersant is low, the viscosity of the positive electrode homogenate slurry (Example 12) is slightly lower than that without adding the dispersant (Comparative Example 2), but not significantly; and when the content of the dispersant is high, its dispersion and viscosity stabilization effect tends to be saturated, and it does not make much sense to continue to increase the usage;

(3) By comparing Example 1 with Comparative Example 1, the dispersant in the conductive agent slurry and the dispersant in the positive electrode homogenate slurry in the present invention will affect the viscosity; when the dispersant in the conductive agent slurry and the positive electrode homogenate slurry is omitted, the viscosity of the conductive agent slurry at the end of grinding and the viscosity after seven days will increase, and the viscosity of the positive electrode homogenate slurry will also increase after placement (24h). This is because the dispersant provided by the present invention can achieve the dispersion of carbon materials, reduce the viscosity of the conductive agent slurry of nano-carbon materials such as carbon nanotubes and graphene, improve the viscosity stability of the conductive agent slurry, and ensure that the conductive agent slurry still has a low viscosity and maintains viscosity stability under high solid content. By comparing Example 4 with Comparative Example 2, it can be seen that the dispersant provided by the present invention can also achieve the dispersion of the positive electrode active material whose surface is fully or partially covered with carbon materials, reduce the viscosity of the positive electrode homogenate slurry, improve the stability of the positive electrode homogenate slurry, and ensure that the positive electrode homogenate slurry still has a low viscosity and maintains viscosity stability under high solid content.

The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims (10)

1. A dispersant for dispersing carbonaceous materials, characterized in that the dispersant comprises ethylamine, diethylamine, ethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N-hydroxyethylethylenediamine, N,N'-bis(2-hydroxyethyl)ethylenediamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, butanediamine, hexanediamine, dicyclohexylamine, piperazine, N-methylpiperazine, N-ethylpiperazine, 1-amino-4-methylpiperazine, N-aminoethylpiperazine, piperidine, N-methylpiperidine, hexahydropyridazine, hexahydropyridazine, Any one or a combination of at least two of trimethyl-S-triazine, ethanolamine, diethanolamine, 2-ethylaminoethanol, 2-methylaminoethanol, 3-amino-1,2-propylene glycol, tris(2-aminoethyl)amine, triethanolamine, n-propanolamine, isopropanolamine, diisopropanolamine, n-butanolamine, isobutanolamine, diisobutanolamine, tert-butanolamine, di-tert-butanolamine, hydrazine, cyanoethylhydrazine, methylhydrazine, hydroxymethylhydrazine, ethylhydrazine, hydroxyethylhydrazine, propylhydrazine, hydroxypropylhydrazine, butylhydrazine, phenylhydrazine, polyethylene glycol amine or di-polyethylene glycol amine. 2. The dispersant according to claim 1, characterized in that the carbon-containing material comprises a carbon material, and/or a positive electrode active material whose surface is fully or partially covered with a carbon material; Preferably, the carbon material comprises any one of carbon nanotubes, graphene, conductive carbon black or graphite whiskers, or a combination of at least two thereof; Preferably, the positive electrode active material includes lithium iron phosphate and/or lithium iron manganese phosphate. 3. A conductive agent slurry of carbon material, characterized in that the conductive agent slurry comprises carbon material and the dispersant according to claim 1 or 2. 4. The conductive agent slurry according to claim 3, characterized in that the mass fraction of the dispersant in the conductive agent slurry is 0.02 to 2 wt%; Preferably, the mass fraction of the dispersant in the conductive agent slurry is 0.05-1 wt %, preferably 0.1-0.6 wt %. 5. The conductive agent slurry according to claim 3 or 4, characterized in that the conductive agent slurry further comprises a dispersion medium; Preferably, the conductive agent slurry further comprises an auxiliary dispersant. 6. A positive electrode homogenate slurry, characterized in that the positive electrode homogenate slurry comprises a positive electrode active material whose surface is fully or partially covered with a carbon material, and the dispersant according to claim 1 or 2. 7. The positive electrode homogenate slurry according to claim 6, characterized in that the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.01 to 0.4 wt%; Preferably, the mass fraction of the dispersant in the positive electrode homogenate slurry is 0.02-0.3 wt %, preferably 0.04-0.2 wt %. 8. The positive electrode homogenate slurry according to claim 6 or 7, characterized in that the positive electrode homogenate slurry further comprises a binder; Preferably, the positive electrode homogenate slurry further includes a conductive agent; Preferably, the positive electrode homogenate slurry also includes a dispersion medium. 9. A positive electrode sheet, characterized in that the positive electrode sheet is prepared by coating the positive electrode homogenous slurry according to any one of claims 6 to 8 on a current collector. 10. A battery, characterized in that the battery comprises the positive electrode sheet according to claim 9.