Conductive adhesive and method of making and using same

Abstract

This application discloses a conductive adhesive, its preparation method, and its application. The conductive adhesive comprises an organic polymer, modified carbon material, a high hydrogen evolution overpotential metal, and N-methylpyrrolidone; the modified carbon material is surface-modified with thiol, carboxyl, and methyl groups. In this conductive adhesive, the carbon material surface is modified to load a large number of thiol and carboxyl groups and a small amount of methyl groups. The thiol and carboxyl groups can effectively complex with lead, while the methyl groups act as electron-withdrawing groups to regulate the complexation strength to a suitable level. This adhesive, which has a strong complexation effect with lead, can form effective chemical bonds between the bipolar plate and lead paste, increasing the bonding strength. Furthermore, after being coated on the lead bipolar plate surface and dried, it does not crack or peel off. The carbon layer possesses certain expansion and contraction capabilities, increasing its contact area with the lead paste, effectively reducing the contact resistance between the lead paste and the bipolar plate, and improving the various performance characteristics of the bipolar battery.

Description

Technical Field

[0001] This application relates to a conductive adhesive, its preparation method, and its application, belonging to the field of bipolar lead-carbon batteries. Background Technology

[0002] With the advancement of science and technology, the problems of energy consumption and environmental pollution have gradually emerged. To address these issues, secondary battery energy storage technologies (such as lead-acid batteries, lithium-ion batteries, metal-air batteries, and fuel cells) have begun to develop rapidly. Among these energy storage systems, although lead-acid batteries have a history of over 100 years, they still hold a very high market share (>70%). The main reasons for lead-acid batteries' large market share in the energy storage technology field are their low production and recycling costs, mature technology, and high safety and reliability. However, compared to other energy storage technologies, traditional lead-acid batteries still cannot meet the technical requirements of new energy vehicles due to their low energy density, low power density, and short cycle life. Therefore, several new types of lead-acid batteries have emerged, providing new directions for the development of lead-acid batteries.

[0003] Lead-carbon batteries are a new type of lead-acid battery. They combine the capacitive characteristics of carbon materials with the battery characteristics of lead-acid batteries. These batteries are characterized by resistance to high current surges and long cycle life. Bipolar lead-carbon batteries are another type of lead-carbon battery, consisting of a series of stacked bipolar plates and a separator between the plates. A bipolar plate is an electrode with positive and negative active materials coated on both sides of the same substrate. Current can flow vertically through the active material. This structure reduces the battery's internal resistance, resulting in significantly improved current transmission efficiency and charge / discharge performance. Commonly used binders in coating the active material on both sides of the bipolar plates include polymer binders (such as vinyl ethylene alcohol resin and vinyl alcohol resin) and ceramic-based binders (such as calcium aluminate). While these binders can effectively fix the positive and negative active materials of the bipolar plates together and ensure stable battery operation, their disadvantages include high internal resistance, poor acid and alkali resistance, poor resistance to expansion and contraction, and the inability to form effective chemical bonds with the lead element in the lead paste or lead plate due to the physical or chemical properties of the binder itself. As a result, bipolar plates coated with conventional binders are prone to cracking and falling off after drying, making it impossible for the cured and dried lead paste active material to adhere stably to its surface. Summary of the Invention

[0004] This invention proposes a conductive binder for effectively bonding lead bipolar plates to cured and dried lead paste. The binder's key feature is that the conductive carbon material surface is modified with a large number of thiol and carboxyl groups, and a small amount of methyl groups. The thiol and carboxyl groups can effectively complex with lead, while the methyl groups act as electron-withdrawing groups to regulate the complexation strength to an optimal level. This binder, with its strong complexation effect with lead, can form effective chemical bonds between the bipolar plate and the lead paste, increasing the bonding strength. Furthermore, after being coated on the lead bipolar plate surface and dried, it does not crack or peel off. The carbon layer possesses certain expansion and contraction capabilities, increasing its contact area with the lead paste, effectively reducing the contact resistance between the lead paste and the bipolar plate, and improving the various performance characteristics of the bipolar battery.

[0005] According to one aspect of this application, a conductive adhesive is provided, comprising an organic polymer, a modified carbon material, a high hydrogen evolution overpotential metal, and N-methylpyrrolidone;

[0006] The modified carbon material has surface modifications including thiol, carboxyl, and methyl groups.

[0007] Optionally, the conductive adhesive comprises, by weight parts:

[0008] 1-50 parts of organic polymer;

[0009] 50-100 parts of modified carbon material;

[0010] 0.05–10 parts of high hydrogen evolution overpotential metal;

[0011] 500-2000 parts of N-methylpyrrolidone.

[0012] Optionally, the organic polymer is selected from at least one of polyvinylidene fluoride and polytetrafluoroethylene.

[0013] Optionally, the high hydrogen evolution overpotential metal is an element or a compound;

[0014] The metal element of the high hydrogen evolution overpotential metal is selected from at least one of lead, bismuth, zinc, gallium, indium, mercury, titanium, and tin.

[0015] Optionally, the modified carbon material is prepared by:

[0016] The modified carbon material is obtained by placing the compound containing thiol and carboxyl groups in a reducing atmosphere and reducing it.

[0017] The reducing atmosphere includes methyl compounds and reducing gases.

[0018] Optionally, the compound containing thiol and carboxyl groups is selected from at least one of mercaptosuccinic acid, dimercaptosuccinic acid, thiol polyethylene glycol carboxyl, and 1-1'-mercaptocarboxydiimidazole.

[0019] Optionally, the molecular weight of the methyl-containing compound is 16 to 500.

[0020] Optionally, the methyl-containing compound is selected from at least one of methane, ethane, and butane.

[0021] Optionally, the reducing gas is selected from at least one of hydrogen and ammonia.

[0022] Optionally, the mass ratio of the thiol and carboxyl compounds to the volume ratio of the reducing atmosphere is 1 g: 0.001 to 200 mL.

[0023] Optionally, the molar ratio of the methyl compound and the reducing gas in the reducing atmosphere is 0.01 to 100:1.

[0024] Optionally, the molar ratio of the methyl compound and the reducing gas in the reducing atmosphere is any value from 0.01:1, 0.1:1, 1:1, 10:1, 50:1, 100:1, or a range between two values.

[0025] Optionally, the reduction conditions are: temperature 200–1500℃, time 1–24h.

[0026] Optionally, the specific surface area of ​​the modified carbon material is 50–3000 m². 2 / g.

[0027] According to another aspect of this application, a method for preparing a conductive adhesive is provided, comprising the following steps:

[0028] The conductive adhesive is obtained by grinding an organic polymer, modified carbon material, high hydrogen evolution overpotential metal, and N-methylpyrrolidone for 0.5–48 h.

[0029] According to another aspect of this application, the application of the above-described conductive adhesive or the conductive adhesive obtained according to the above preparation method in a bipolar lead-carbon battery is provided.

[0030] The beneficial effects that this application can produce include:

[0031] 1) The conductive adhesive provided in this application modifies the surface of a carbon material by loading a large number of thiol and carboxyl groups and a small amount of methyl groups. The thiol and carboxyl groups can effectively complex with lead, while the methyl groups, as electron-withdrawing groups, are used to regulate the complexation strength to a suitable level. This adhesive, which has a strong complexation effect with lead, can form effective chemical bonds between the bipolar plate and the lead paste, increasing the bonding strength and effectively bonding the lead paste to the bipolar plate substrate. This avoids problems such as conductive adhesive cracking and lead paste peeling, effectively reducing the internal resistance between the active material and the bipolar plate, and improving battery performance.

[0032] 2) The preparation method of the conductive adhesive provided in this application is simple. Detailed Implementation

[0033] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0034] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0035] Example 1

[0036] Step 1: Prepare the bipolar plate conductive adhesive using the following method:

[0037] 1. Modified carbon materials with surface-loaded thiol, carboxyl, and methyl groups were prepared using the following method: 500 g of mercaptosuccinic acid was heated at 900 °C for 5 h in a hydrogen-methane mixture with a molar ratio of 1:1. The specific surface area of ​​the prepared modified carbon material was 1300 m². 2 / g.

[0038] 2. Preparation of conductive adhesive:

[0039] Mix 10g PVDF, 70g modified carbon material prepared in step 1, 5g high hydrogen evolution overpotential metallic elemental lead, and 1000g NMP thoroughly and grind for 12 hours.

[0040] Step 2: Preparation of Bipolar Lead-Carbon Batteries

[0041] The flow-type lead-carbon battery was prepared using the following steps:

[0042] 1. Preparation of the negative electrode:

[0043] (1) 600g lead powder, 9g carbon material, 8.4g barium sulfate and 0.3g polypropylene short fibers with a length of 5mm and a diameter of 0.5-1.5μm are premixed with a high-speed mixer. While stirring, 84g deionized water is added to the premixed powder and stirred for 10 minutes to obtain lead paste.

[0044] (2) Apply the high hydrogen evolution conductive adhesive prepared in step one to both sides of the bipolar plate, and apply the lead paste to the surface of the bipolar plate grid coated with the conductive adhesive. The grid size is 70mm long, 50mm wide, and 2mm thick.

[0045] 2. Preparation of positive electrode: The positive electrode of lead-acid battery is prepared according to the same process steps as the negative electrode preparation steps (1) and (2). The difference is that no carbon material is added during the preparation of the positive electrode, and it is scraped onto the other side of the bipolar plate coated with the conductive binder prepared in step one.

[0046] 3. Preparation of the end electrodes: The negative electrode lead paste prepared in step (1) and the positive electrode lead paste prepared in step (2) are scraped and applied to one side of the bipolar plate coated with the conductive adhesive prepared in step 1, while the other side is left uncoated with any active material. The bipolar plate coated with lead paste and the end plates on both sides are then subjected to curing and drying treatment. The curing temperature is 40℃, the humidity is 80%, and the curing time is 20 hours; the drying temperature is 80℃, and the drying time is 24 hours.

[0047] 4. Preparation of lead-carbon battery: Five bipolar plates and two end plates are arranged alternately with the positive and negative electrodes facing each other. A lead-acid battery AGM separator is placed between the plates. The plates and separator are pressed together and placed into a battery box using a tight assembly method. The battery box has through-hole channels for electrolyte flow at both ends. The battery box is 76mm long, 40mm wide, and 100mm high. 80.3g of sulfuric acid electrolyte with a density of 1.275g / ml is injected into the battery box.

[0048] The battery was subjected to a room temperature life test under the following conditions: at 25°C, it was discharged at a constant current of 4.2A for 59 seconds, discharged at 18A for 1 second, and charged at a constant current and constant voltage of 6.3A and 2.3V for 60 seconds. This charge and discharge condition was cycled 3600 times, followed by a 40-hour rest period. After 40 hours, the cycle was restarted. The life test was terminated when the battery voltage dropped below 1.2V.

[0049] The assembled lead-carbon battery has an initial voltage of 2.302V when fully charged at room temperature, and can run 45,010 cycles in the room temperature life test. Compared with the test results of the bipolar lead-carbon battery without added bipolar conductive binder (Comparative Example 1) under the same test conditions (7,211 cycles), the room temperature cycle life of the prepared lead-carbon battery can reach 6.24 times that of the traditional lead-acid battery.

[0050] Example 2

[0051] Following the conditions of Example 1, the amount of modified carbon material added in step 2 of step one was changed to 50g. The assembled bipolar lead-carbon battery had an initial voltage of 2.289V when fully charged and could run 46,506 cycles of life test. Compared with the test results of a lead-carbon battery without conductive binder under the same test conditions (7,211 cycles), the life of the bipolar lead-carbon battery can reach 6.45 times that of a traditional lead-acid battery.

[0052] Example 3

[0053] Following the conditions of Example 1, the amount of modified carbon material added in step 2 of step one was changed to 100g. The assembled bipolar lead-carbon battery had an initial voltage of 2.262V when fully charged and could run 46,160 cycles of life test. Compared with the test results of a lead-carbon battery without conductive binder under the same test conditions (7,211 cycles), the life of the bipolar lead-carbon battery can reach 6.40 times that of a traditional lead-acid battery.

[0054] Example 4

[0055] Following the conditions of Example 1, the amount of PVDF added in step 2 of step one was changed to 1g. The assembled bipolar lead-carbon battery had an initial voltage of 2.236V when fully charged and could run 42,084 cycles of life test. Compared with the test results of a lead-carbon battery without conductive binder under the same test conditions (7,211 cycles), the life of the bipolar lead-carbon battery can reach 5.84 times that of a conventional lead-acid battery.

[0056] Example 5

[0057] Following the conditions of Example 1, the amount of PVDF added in step 2 of step one was changed to 50g. The assembled bipolar lead-carbon battery had an initial voltage of 2.277V when fully charged and could run 41,436 cycles of life test. Compared with the test results of a lead-carbon battery without conductive binder under the same test conditions (7,211 cycles), the life of the bipolar lead-carbon battery can reach 5.75 times that of a conventional lead-acid battery.

[0058] Example 6

[0059] Following the conditions of Example 1, the molar ratio of the hydrogen-methane mixture in step 1 was changed to 10:1. The assembled bipolar lead-carbon battery had an initial voltage of 2.248V when fully charged and could run 36,024 cycles of life testing. Compared with the test results of a lead-carbon battery without conductive binder under the same test conditions (7,211 cycles), the lifespan of the bipolar lead-carbon battery can reach 5.00 times that of a conventional lead-acid battery.

[0060] Comparative Example 1

[0061] Bipolar lead-carbon battery without conductive binder: Following the requirements of Example 1, without changing other conditions or adding conductive binder, the bipolar lead-carbon battery was directly assembled. The assembled bipolar lead-carbon battery had an initial voltage of 2.109V when fully charged and could run 7211 cycles of life test.

[0062] Comparative Example 2

[0063] Following the conditions of Example 1, the mercaptosuccinic acid in step 1 was replaced with the same mass of mercaptoethanol. Because the precursor material lacks carboxyl groups, its complexing ability with the bipolar plate substrate and lead paste is weak. This leads to problems such as cracking and peeling of the lead paste after it is made into a conductive binder. Consequently, the assembled bipolar lead-carbon battery has an initial voltage of 2.107V under full charge and can only complete 3621 cycles of life testing.

[0064] Comparative Example 3

[0065] Following the conditions of Example 1, the mercaptosuccinic acid in step 1 was replaced with the same mass of succinic acid. Because the precursor material does not contain mercapto groups, its complexing ability with the bipolar plate substrate and lead paste is weak. This leads to problems such as cracking and peeling of the lead paste after it is made into a conductive binder. Consequently, the assembled bipolar lead-carbon battery has an initial voltage of 2.005V when fully charged and can only run 4293 cycles of life testing.

[0066] Comparative Example 4

[0067] Following the conditions of Example 1, the methane-hydrogen mixture in step 1 was replaced with a nitrogen-hydrogen mixture in the same molar ratio. Because the prepared modified carbon material does not contain methyl groups, its complexation ability with the bipolar plate substrate and lead paste is poor. This leads to problems such as cracking and peeling of the lead paste after it is made into a conductive binder. The assembled bipolar lead-carbon battery has an initial voltage of 2.246V under full charge and can run 6053 cycles of life testing.

[0068] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An electrically conductive adhesive, characterized by, Including organic polymers, modified carbon materials, high hydrogen evolution overpotential metals, and N-methylpyrrolidone; The modified carbon material has surface modifications including thiol, carboxyl, and methyl groups; The conductive adhesive comprises, by weight, the following: 1-50 parts of organic polymer; 50-100 parts of modified carbon material; 0.05-10 parts of high hydrogen evolution overpotential metal; 500-2000 parts of N-methylpyrrolidone; The preparation method of the modified carbon material is as follows: The modified carbon material is obtained by placing the compound containing thiol and carboxyl groups in a reducing atmosphere and reducing it. The reducing atmosphere includes methyl compounds and reducing gases; The mass ratio of the thiol and carboxyl compounds to the volume of the reducing atmosphere is 1 g: 0.001~200 mL; The molar ratio of methyl compounds and reducing gases in the reducing atmosphere is 0.01 to 100:

1.

2. The electrically conductive adhesive of claim 1, wherein The organic polymer is selected from at least one of polyvinylidene fluoride and polytetrafluoroethylene; The high hydrogen evolution overpotential metal is an element or a compound; The metal element of the high hydrogen evolution overpotential metal is selected from at least one of lead, bismuth, zinc, gallium, indium, mercury, titanium, and tin.

3. The electrically conductive adhesive of claim 2, wherein The compound containing thiol and carboxyl groups is selected from at least one of mercaptosuccinic acid, dimercaptosuccinic acid, thiol polyethylene glycol carboxyl, and 1-1'-thiol carboxyl diimidazole.

4. The electrically conductive adhesive of claim 2, wherein The molecular weight of the methyl-containing compound is 16-500; The methyl-containing compound is selected from at least one of methane, ethane, and butane; The reducing gas is selected from at least one of hydrogen and ammonia.

5. The electrically conductive adhesive of claim 2, wherein The reduction conditions are: temperature 200~1500℃, time 1~24h.

6. The electrically conductive adhesive of claim 2, wherein The specific surface area of the modified carbon material is 50-3000 m 2 / g.

7. A method for producing the electroconductive adhesive agent as claimed in any one of claims 1 to 6, characterized by, Includes the following steps: The conductive adhesive is obtained by grinding an organic polymer, modified carbon material, high hydrogen evolution overpotential metal, and N-methylpyrrolidone for 0.5 to 48 hours.

8. The application of a conductive adhesive according to any one of claims 1 to 6 or a conductive adhesive obtained by the preparation method according to claim 7 in a bipolar lead-carbon battery.