A preparation process of conductive paste

Abstract

The invention discloses a preparation process of a conductive slurry, comprising the following steps: a first step, weighing the following raw materials in parts by weight: 3-12 parts of a conductive sponge, 0.3-4.2 parts of a dispersant, and 90-100 parts of an organic solvent; a second step, uniformly mixing the conductive sponge, the dispersant, and the organic solvent to prepare a premix, then placing the premix in a grinder, and grinding the premix for 10-15 min at a linear speed of 10-50 m / s to prepare a conductive slurry; and preparing a conductive sponge by generating doped polyaniline in the structure and on the surface of the composite sponge to increase the access amount of the polyaniline and achieve hybridization of the polymer and the inorganic material, thereby imparting the conductive sponge with excellent conductive properties. In addition, the conductive sponge has a high specific surface area and a high electrolyte absorption capacity, and when doped in a battery positive electrode, the gram capacity of the battery cell is increased, the internal resistance is reduced, and the conductive properties are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive materials, and particularly relates to a preparation process of a conductive paste. Background Art

[0002] Lithium-ion batteries generally include a positive electrode sheet, a negative electrode sheet, and a separator between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive electrode membrane coated on the positive current collector, while the negative electrode sheet includes a negative current collector and a negative electrode membrane coated on the negative current collector. When preparing the electrode sheet, the active material, conductive agent, binder, and solvent are first made into an electrode slurry, which is then coated on the surface of the current collector as required and then dried to obtain the battery electrode sheet. The more evenly the components in the electrode slurry are dispersed, the better the processing performance of the electrode sheet will be. The impedance distribution at all parts of the electrode will be more uniform, the greater the role of the active material can play during charging and discharging, and its average gram capacity will be improved, thereby improving the performance of the entire battery. The performance of the conductive agent directly affects the performance of the electrode slurry. Most lithium-ion battery manufacturers will mix and match the conductive agents according to their morphology, particle size, specific surface area, and conductive properties. Currently, the most widely used conductive agents in electrode slurries are conductive carbon black, conductive graphite, carbon nanotubes (CNTs), and graphene, or a combination of several of them. During the preparation process, graphene undergoes ultrasound, high-speed stirring, and other activities, causing its flake diameter to break, resulting in a relatively small specific surface area and limited contact area with the active material. This limits the transfer of electrons between the active material and the conductive agent, thus affecting the conductivity of the battery. Summary of the Invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a preparation process of a conductive paste.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A process for preparing a conductive paste comprises the following steps:

[0006] Step 1: Weigh the following raw materials by weight: 3-12 parts of conductive sponge, 0.3-4.2 parts of dispersant, and 90-100 parts of organic solvent;

[0007] The second step is to mix the conductive sponge, dispersant and organic solvent to obtain a premix, and then place the premix in a grinder and grind it at a linear speed of 10-50 m / s for 10-15 minutes to obtain a conductive slurry;

[0008] The conductive sponge is made by the following steps:

[0009] Step S11, adding the composite sponge to deionized water, stirring at a constant speed for 3-45 minutes, then adding p-phenylenediamine, continuing stirring for 30 minutes, heating to 60°C, stirring at a constant speed for 4 hours, centrifuging at a speed of 8000-10000 r / min for 10 minutes after the reaction is completed, washing three times with anhydrous ethanol and deionized water respectively, and freeze-drying to obtain a modified composite sponge, wherein the weight ratio of the composite sponge, p-phenylenediamine and deionized water is controlled to be 0.1-0.2 g:8 mmol:500 mL;

[0010] In step S11, the composite sponge is dispersed in deionized water, and p-phenylenediamine is added. The p-phenylenediamine acts as a reducing agent and a stabilizer to react with the oxygen-containing functional groups on the composite sponge to obtain a modified composite sponge.

[0011] Step S12, adding the modified composite sponge, aniline and hydrochloric acid to deionized water, adding ammonium persulfate, magnetically stirring for 10 minutes, cooling to 0°C, and continuing stirring for 8 hours to obtain a crude product, washing it three times with dilute hydrochloric acid and deionized water with a concentration of 0.01 mol / L, respectively, and then vacuum filtering and freeze-drying to obtain a conductive sponge, controlling the weight ratio of the modified composite sponge, aniline and deionized water to be 1:2-2.5:200, and the molar ratio of aniline, hydrochloric acid and ammonium persulfate to be 1:2:0.3-0.5.

[0012] In step S12, aniline monomer is added, and ammonium persulfate is added as an initiator to initiate a polymerization reaction on the surface of the modified composite sponge, and polyaniline is generated on the surface of the modified sponge. By making a composite sponge, its own three-dimensional network structure has ultra-high specific area and thermal stability. In addition, by generating doped polyaniline in the structure and on the surface of the composite sponge, the access amount of polyaniline is increased, and hybridization of polymer and inorganic materials is achieved to prepare a conductive sponge, which has excellent conductive properties. In addition, its own high specific surface area and high electrolyte absorption capacity increase the battery cell capacity, reduce internal resistance, and improve conductive properties when doped in the positive electrode of the battery.

[0013] Furthermore: the composite sponge is prepared by the following steps:

[0014] Step S21, adding multi-walled carbon nanotubes to concentrated sulfuric acid, stirring at a constant speed for 2 hours at room temperature, then adding phosphoric acid, stirring at a constant speed for 20 minutes, adding potassium permanganate in four equal amounts within 1 minute, then heating to 50°C, keeping the temperature for reaction for 2 hours, cooling to room temperature after the reaction, adding 30% by mass aqueous hydrogen peroxide solution and ice water, standing for 10 hours, and then filtering, washing the filter cake three times with 10% by mass dilute hydrochloric acid, anhydrous ethanol and deionized water, respectively, to obtain graphene oxide nanoribbons, wherein the amount ratio of multi-walled carbon nanotubes, concentrated sulfuric acid and phosphoric acid is controlled to be 1-1.5 g: 200-220 mL: 15-20 mL, the weight ratio of potassium permanganate to multi-walled carbon nanotubes is 8:1, and the volume ratio of concentrated sulfuric acid, hydrogen peroxide solution and ice water is 20:1:50;

[0015] Step S22, adding graphene oxide and graphene oxide nanoribbons to deionized water, stirring at a constant speed for 1-2 hours, placing the mixed solution in a freeze dryer, freezing at -5-0°C for 36 hours, vacuuming and continuing freeze drying for 48 hours, taking it out, and standing it for 24 hours to obtain a composite sponge, wherein the weight ratio of graphene oxide, graphene oxide nanoribbons and deionized water is controlled to be 1:1-1.5:100;

[0016] In step S21, multi-walled carbon nanotubes are added to concentrated sulfuric acid, and the carbon nanotubes are intercalated with sulfuric acid to facilitate subsequent cutting and exfoliation reactions. The multi-walled carbon nanotubes are radially cut by potassium permanganate, concentrated sulfuric acid, and phosphoric acid oxidation to prepare graphene oxide nanoribbons. The graphene oxide nanoribbons are then mixed with graphene oxide by freeze drying, and the graphene oxide nanoribbons are adsorbed on the surface of the graphene oxide. Since the nanoribbons have the same planar structure composed of interconnected C=C double bonds, they can be tightly adsorbed on the surface of the graphene, thereby increasing the thickness of the graphene sheet and making it stronger than pure graphene sheets. The composite sponge is then freeze dried.

[0017] Furthermore, the dispersant is a mixture of one or more of polyvinyl pyrrolidone, polyvinyl alcohol and polyethylene glycol in any proportion.

[0018] Furthermore, the organic solvent is a mixture of one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide in any proportion.

[0019] Beneficial effects of the present invention:

[0020] The present invention discloses a conductive slurry, which uses a conductive sponge as a conductive agent. During the preparation process of the conductive sponge, graphene oxide nanoribbons are first prepared, then mixed with graphene oxide by a freeze-drying method, and adsorbed to form a composite sponge. Then, p-phenylenediamine is used as a reducing agent and stabilizer to react with oxygen-containing functional groups on the composite sponge to prepare a modified composite sponge. Polyaniline is generated on the surface of the modified sponge through a polymerization reaction. The three-dimensional network structure of the composite sponge itself has ultra-high specific area and thermal stability. In addition, by generating doped polyaniline in the structure and on the surface of the composite sponge, the access amount of polyaniline is increased, and hybridization of polymer and inorganic material is achieved to prepare the conductive sponge, which is endowed with excellent conductive performance. In addition, due to its high specific surface area and high electrolyte absorption capacity, when doped in a positive electrode of a battery, the gram capacity of the battery cell is increased, the internal resistance is reduced, and the conductive performance is improved. DETAILED DESCRIPTION

[0021] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] Example 1

[0023] The conductive sponge is made by the following steps:

[0024] The multi-walled carbon nanotubes were added to concentrated sulfuric acid and stirred at room temperature for 2 hours, and then phosphoric acid was added and stirred at a constant speed for 20 minutes. Potassium permanganate was added in four equal amounts within 1 minute, and then the temperature was raised to 50°C and kept for reaction for 2 hours. After the reaction, it was cooled to room temperature and a 30% by mass fraction hydrogen peroxide aqueous solution and ice water were added. The mixture was allowed to stand for 10 hours and then filtered. The filter cake was washed three times with 10% by mass fraction dilute hydrochloric acid, anhydrous ethanol and deionized water, respectively, to obtain graphene oxide nanoribbons. The amount ratio of multi-walled carbon nanotubes, concentrated sulfuric acid and phosphoric acid was controlled to be 1 g: 200 mL: 15 mL, the weight ratio of potassium permanganate and multi-walled carbon nanotubes was 8: 1, and the volume ratio of concentrated sulfuric acid, hydrogen peroxide aqueous solution and ice water was 20: 1: 50.

[0025] Graphene oxide and graphene oxide nanoribbons were added to deionized water and stirred at a constant speed for 1-2 hours. The mixture was placed in a freeze dryer and frozen at -5°C for 36 hours. The mixture was vacuum-dried and freeze-dried for 48 hours. The mixture was taken out and allowed to stand for 24 hours to prepare a composite sponge. The weight ratio of graphene oxide, graphene oxide nanoribbons and deionized water was controlled to be 1:1:100.

[0026] The composite sponge was added to deionized water and stirred at a constant speed for 3 minutes, after which p-phenylenediamine was added and stirred for 30 minutes. The temperature was raised to 60°C and stirred at a constant speed for 4 hours. After the reaction, the mixture was centrifuged at a speed of 8000 r / min for 10 minutes, washed three times with anhydrous ethanol and deionized water, respectively, and freeze-dried to obtain a modified composite sponge. The weight ratio of the composite sponge, p-phenylenediamine, and deionized water was controlled to be 0.1 g:8 mmol:500 mL.

[0027] The modified composite sponge, aniline and hydrochloric acid were added to deionized water, and ammonium persulfate was added. The mixture was magnetically stirred for 10 minutes, cooled to 0°C, and stirred for 8 hours to obtain a crude product. The crude product was washed three times with dilute hydrochloric acid and deionized water with a concentration of 0.01 mol / L, respectively. After that, the crude product was vacuum filtered and freeze-dried to obtain a conductive sponge. The weight ratio of the modified composite sponge, aniline and deionized water was controlled to be 1:2:200, and the molar ratio of aniline, hydrochloric acid and ammonium persulfate was controlled to be 1:2:0.3.

[0028] Example 2

[0029] The conductive sponge is made by the following steps:

[0030] The multi-walled carbon nanotubes were added to concentrated sulfuric acid and stirred at a constant speed for 2 hours at room temperature. Phosphoric acid was then added and stirred at a constant speed for 20 minutes. Potassium permanganate was added in four equal amounts within 1 minute. The temperature was then raised to 50°C and kept for reaction for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and a 30% by mass aqueous solution of hydrogen peroxide and ice water were added. The mixture was allowed to stand for 10 hours and then filtered. The filter cake was washed three times with 10% by mass dilute hydrochloric acid, anhydrous ethanol and deionized water, respectively, to obtain graphene oxide nanoribbons. The amount ratio of multi-walled carbon nanotubes, concentrated sulfuric acid and phosphoric acid was controlled to be 1.2 g: 210 mL: 18 mL, the weight ratio of potassium permanganate to multi-walled carbon nanotubes was 8:1, and the volume ratio of concentrated sulfuric acid, hydrogen peroxide and ice water was 20:1:50.

[0031] Graphene oxide and graphene oxide nanoribbons were added to deionized water and stirred at a constant speed for 1 hour. The mixture was placed in a freeze dryer and frozen at 0°C for 36 hours. The mixture was vacuum-dried and freeze-dried for 48 hours. The mixture was taken out and allowed to stand for 24 hours to prepare a composite sponge. The weight ratio of graphene oxide, graphene oxide nanoribbons and deionized water was controlled to be 1:1.2:100.

[0032] The composite sponge was added to deionized water and stirred at a constant speed for 30 minutes, after which p-phenylenediamine was added and stirred for another 30 minutes. The mixture was heated to 60°C and stirred at a constant speed for 4 hours. After the reaction, the mixture was centrifuged at a speed of 10,000 r / min for 10 minutes, washed three times with anhydrous ethanol and deionized water, respectively, and freeze-dried to obtain a modified composite sponge. The weight ratio of the composite sponge, p-phenylenediamine, and deionized water was controlled to be 0.2 g:8 mmol:500 mL.

[0033] The modified composite sponge, aniline and hydrochloric acid were added to deionized water, and ammonium persulfate was added. The mixture was magnetically stirred for 10 minutes, cooled to 0°C, and stirred for 8 hours to obtain a crude product. The crude product was washed three times with dilute hydrochloric acid and deionized water with a concentration of 0.01 mol / L, respectively. After that, the crude product was vacuum filtered and freeze-dried to obtain a conductive sponge. The weight ratio of the modified composite sponge, aniline and deionized water was controlled to be 1:2.3:200, and the molar ratio of aniline, hydrochloric acid and ammonium persulfate was controlled to be 1:2:0.4.

[0034] Example 3

[0035] The conductive sponge is made by the following steps:

[0036] The multi-walled carbon nanotubes were added to concentrated sulfuric acid and stirred at a constant speed for 2 hours at room temperature. Phosphoric acid was then added and stirred at a constant speed for 20 minutes. Potassium permanganate was added in four equal amounts within 1 minute. The temperature was then raised to 50°C and kept for reaction for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and a 30% by mass aqueous solution of hydrogen peroxide and ice water were added. The mixture was allowed to stand for 10 hours and then filtered. The filter cake was washed three times with 10% by mass dilute hydrochloric acid, anhydrous ethanol and deionized water, respectively, to obtain graphene oxide nanoribbons. The amount ratio of multi-walled carbon nanotubes, concentrated sulfuric acid and phosphoric acid was controlled to be 1.5 g: 220 mL: 20 mL, the weight ratio of potassium permanganate to multi-walled carbon nanotubes was 8:1, and the volume ratio of concentrated sulfuric acid, hydrogen peroxide and ice water was 20:1:50.

[0037] Graphene oxide and graphene oxide nanoribbons were added to deionized water and stirred at a constant speed for 1-2 hours. The mixture was placed in a freeze dryer and frozen at 0°C for 36 hours. The mixture was vacuum-dried and freeze-dried for 48 hours. The mixture was taken out and allowed to stand for 24 hours to prepare a composite sponge. The weight ratio of graphene oxide, graphene oxide nanoribbons and deionized water was controlled to be 1:1.5:100.

[0038] The composite sponge was added to deionized water and stirred at a constant speed for 45 minutes, after which p-phenylenediamine was added and stirred for 30 minutes. The temperature was raised to 60°C and stirred at a constant speed for 4 hours. After the reaction, the mixture was centrifuged at a speed of 10,000 r / min for 10 minutes, washed three times with anhydrous ethanol and deionized water, respectively, and freeze-dried to obtain a modified composite sponge. The weight ratio of the composite sponge, p-phenylenediamine, and deionized water was controlled to be 0.2 g: 8 mmol: 500 mL.

[0039] The modified composite sponge, aniline and hydrochloric acid were added to deionized water, and ammonium persulfate was added. The mixture was magnetically stirred for 10 minutes, cooled to 0°C, and stirred for 8 hours to obtain a crude product. The crude product was washed three times with dilute hydrochloric acid and deionized water with a concentration of 0.01 mol / L, respectively. After that, the crude product was vacuum filtered and freeze-dried to obtain a conductive sponge. The weight ratio of the modified composite sponge, aniline and deionized water was controlled to be 1:2.5:200, and the molar ratio of aniline, hydrochloric acid and ammonium persulfate was controlled to be 1:2:0.5.

[0040] Example 4

[0041] A process for preparing a conductive paste comprises the following steps:

[0042] Step 1: Weigh the following raw materials by weight: 3 parts of conductive sponge, 0.3 parts of polyvinyl pyrrolidone, and 90 parts of N,N-dimethylformamide;

[0043] In the second step, the conductive sponge, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed evenly to prepare a premix, and then the premix is ​​placed in a grinder and ground at a linear speed of 10 m / s for 10 minutes to prepare a conductive slurry.

[0044] Example 5

[0045] A process for preparing a conductive paste comprises the following steps:

[0046] Step 1: Weigh the following raw materials by weight: 10 parts of conductive sponge, 2.5 parts of polyvinyl alcohol, and 95 parts of N-methylpyrrolidone;

[0047] In the second step, the conductive sponge, polyvinyl alcohol and N-methylpyrrolidone are mixed evenly to prepare a premix, and then the premix is ​​placed in a grinder and ground at a linear speed of 30 m / s for 12 minutes to prepare a conductive slurry.

[0048] Example 6

[0049] A process for preparing a conductive paste comprises the following steps:

[0050] Step 1: Weigh the following raw materials by weight: 12 parts of conductive sponge, 4.2 parts of polyethylene glycol, and 100 parts of N,N-dimethylacetamide;

[0051] In the second step, the conductive sponge, polyethylene glycol and N,N-dimethylacetamide are mixed evenly to prepare a premix, and then the premix is ​​placed in a grinder and ground at a linear speed of 50 m / s for 15 minutes to prepare a conductive slurry.

[0052] Comparative Example 1

[0053] This comparative example is the graphene conductive slurry prepared by CN201810239161.4.

[0054] Comparative Example 2

[0055] This comparative example is the composite conductive paste prepared by CN201811156985.1.

[0056] The conductive pastes prepared in Examples 4-6 and Comparative Examples 1-2 were applied to power batteries, and the gram capacity and average internal resistance of the power battery cells were measured. The amount of conductive paste added was 1% of the mass of the battery positive electrode. The measurement conditions were: charging when the battery capacity reached 50%, the charge cut-off voltage was 4.2V, and discharging when the battery capacity was reached, the discharge cut-off voltage was 2.75V. The results are shown in the following table:

[0057]

[0058] It can be seen from the above table that the conductive pastes prepared in Examples 4-6 enable the battery cells to have higher gram capacity, lower internal resistance, and better conductive properties.

[0059] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A process for preparing a conductive paste, characterized in that: The steps include: Step 1: Weigh the following raw materials by weight: 3-12 parts of conductive sponge, 0.3-4.2 parts of dispersant, and 90-100 parts of organic solvent; The second step is to mix the conductive sponge, dispersant and organic solvent to obtain a premix, and then place the premix in a grinder and grind it at a linear speed of 10-50 m / s for 10-15 minutes to obtain a conductive slurry; The conductive sponge is made by the following steps: Step S11, adding the composite sponge to deionized water, stirring at a constant speed for 3-45 minutes, then adding p-phenylenediamine, continuing to stir for 30 minutes, heating to 60° C., stirring at a constant speed for 4 hours, centrifuging at a speed of 8000-10000 r / min for 10 minutes after the reaction is completed, washing three times with anhydrous ethanol and deionized water respectively, and freeze-drying to obtain a modified composite sponge; Step S12, adding the modified composite sponge, aniline and hydrochloric acid to deionized water, adding ammonium persulfate, magnetically stirring for 10 minutes, cooling to 0°C, and continuing stirring for 8 hours to obtain a crude product, washing it three times with 0.01 mol / L dilute hydrochloric acid and deionized water, respectively, followed by vacuum filtration and freeze-drying to obtain a conductive sponge; The composite sponge is prepared by the following steps: Step S21, adding multi-walled carbon nanotubes to concentrated sulfuric acid, stirring at a constant speed for 2 hours at room temperature, then adding phosphoric acid, stirring at a constant speed for 20 minutes, adding potassium permanganate in four equal amounts within 1 minute, then heating to 50° C., keeping the temperature for reaction for 2 hours, cooling to room temperature after the reaction, adding 30% by mass aqueous hydrogen peroxide solution and ice water, letting it stand for 10 hours, and then filtering, and washing the filter cake three times with 10% by mass dilute hydrochloric acid, anhydrous ethanol, and deionized water, respectively, to produce graphene oxide nanoribbons; Step S22: adding graphene oxide and graphene oxide nanoribbons to deionized water, stirring at a constant speed for 1-2 hours, placing the mixed solution in a freeze dryer, freezing at -5-0°C for 36 hours, vacuuming and freeze-drying for 48 hours, taking out, and standing for 24 hours to obtain a composite sponge.

2. The process for preparing a conductive paste according to claim 1, wherein: In step S11, the weight ratio of the composite sponge, p-phenylenediamine and deionized water is controlled to be 0.1-0.2 g: 8 mmol: 500 mL.

3. The process for preparing a conductive paste according to claim 1, wherein: In step S12, the weight ratio of the modified composite sponge, aniline and deionized water is controlled to be 1:2-2.5:200, and the molar ratio of aniline, hydrochloric acid and ammonium persulfate is controlled to be 1:2:0.3-0.

5.

4. The process for preparing a conductive paste according to claim 2, wherein: In step S21, the dosage ratio of multi-walled carbon nanotubes, concentrated sulfuric acid and phosphoric acid is controlled to be 1-1.5 g: 200-220 mL: 15-20 mL, the weight ratio of potassium permanganate to multi-walled carbon nanotubes is 8:1, and the volume ratio of concentrated sulfuric acid, aqueous hydrogen peroxide solution and ice water is 20:1:

50.

5. The process for preparing a conductive paste according to claim 2, wherein: In step S22, the weight ratio of graphene oxide, graphene oxide nanoribbons and deionized water is controlled to be 1:1-1.5:

100.

6. The process for preparing a conductive paste according to claim 1, wherein: The dispersant is a mixture of one or more of polyvinyl pyrrolidone, polyvinyl alcohol and polyethylene glycol in any proportion.

7. The process for preparing a conductive paste according to claim 1, wherein: The organic solvent is a mixture of one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide in any proportion.

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