Conductive Adhesive for Supercapacitor and Its Preparation Method

Abstract

This application relates to the field of capacitor adhesives, and specifically discloses a conductive adhesive for supercapacitors and its preparation method. The conductive adhesive comprises 30% - 45% of a conductive adhesive matrix, 35% - 55% of a first solvent, 4.5% - 10.5% of a second solvent, 1.5% - 3.5% of a binder, 1.5% - 3.5% of a dispersant, 1.5% - 2.5% of an auxiliary agent, and 3% - 8% of a conductive enhancer. The conductive adhesive matrix is a conductive polymer material, the boiling point of the second solvent is 55 - 100 °C, and the boiling point of the first solvent is higher than that of the second solvent. The preparation method is as follows: the first solvent, the binder, and the auxiliary agent are stirred and mixed evenly, then the conductive adhesive matrix and the dispersant are added and ultrasonically dispersed evenly, and then the second solvent and the conductive enhancer are added and stirred and mixed evenly to obtain the conductive adhesive. The conductive adhesive prepared in this application has a uniform system, is not prone to precipitation and agglomeration, and has a simple preparation process.

Description

Technical Field

[0001] The present application relates to the field of capacitor adhesives, and more specifically, it relates to a conductive adhesive for supercapacitors and a preparation method thereof. Background Art

[0002] A supercapacitor refers to a new type of energy storage device between traditional capacitors and rechargeable batteries. It is a new type of component that stores energy through the formation of an interfacial double layer between the electrode and the electrolyte. It not only has the characteristics of rapid charge and discharge of a capacitor but also has the energy storage characteristics of a battery. Compared with traditional storage batteries and physical capacitors, supercapacitors have the characteristics of high power density, long cycle life, wide operating temperature range, and environmental friendliness. Even at a temperature of a few degrees below zero, its charge and discharge speed is only a few seconds, and the number of charge and discharge cycles can reach one million times. It is an efficient, practical, and environmentally friendly energy storage device and has been widely used in new energy fields such as solar power generation, new energy vehicles, smart grids, and urban public transportation.

[0003] In the manufacturing process of supercapacitors, the electrode plates of the supercapacitors are first cut into pieces according to the designed size, and then the cut plates are placed into the capacitor housing. During manufacturing, a conductive adhesive needs to be added between the inner wall of the capacitor housing and the plate. The conductive adhesive is an adhesive that can effectively bond various materials and has electrical conductivity. It can not only firmly attach the plate to the bottom surface of the capacitor metal shell but also greatly improve the electrical conductivity between the capacitor housing and the plate.

[0004] Currently, most conductive adhesives use adhesives as the matrix, and rely on adding conductive fillers to the adhesive to make the glue solution conductive. The conductive fillers added usually are conductive metals, graphite, and some conductive compounds, with conductive metals being the majority, such as powders of gold, silver, copper, aluminum, zinc, iron, nickel, etc.

[0005] However, during the use of the conductive adhesive, the solid particles of the conductive fillers in the conductive adhesive are prone to precipitation, resulting in easy stratification of the conductive adhesive. During coating, due to the uneven distribution of the conductive fillers in the conductive adhesive system, there will be differences in the electrical conductivity of different parts between the capacitor housing and the plate, affecting the performance of the supercapacitor. Summary of the Invention

[0006] In order to improve the problem that the uneven distribution of conductive fillers in the current conductive adhesive affects the electrical conductivity, the present application provides a conductive adhesive for supercapacitors and a preparation method thereof.

[0007] In a first aspect, the present application provides a conductive adhesive for supercapacitors, adopting the following technical solution:

[0008] A conductive adhesive for supercapacitors, comprising the following components in weight percentage:

[0009] Conductive adhesive matrix: 30% - 45%;

[0010] First solvent: 35% - 55%;

[0011] Second solvent: 4.5% - 10.5%;

[0012] Binder: 1.5% - 3.5%;

[0013] Auxiliary agent: 1.5% - 2.5%;

[0014] Dispersant: 1.5% - 3.5%;

[0015] Conductive enhancer: 3% - 8%;

[0016] Wherein, the conductive adhesive matrix is a conductive polymer material, the boiling point of the second solvent is 55 - 100 °C, and the boiling point of the first solvent is higher than that of the second solvent.

[0017] By adopting the above technical solution, a conductive polymer material is used as the conductive adhesive matrix, and a conductive enhancer is added to further improve the conductivity. The purpose of the binder is to enhance the adhesion of the conductive adhesive and prevent the aggregation or agglomeration of the conductive adhesive matrix; the combination of each component makes the prepared conductive adhesive have good fluidity, more excellent conductivity, good dispersion effect, and more uniform conductive adhesive system. Compared with the traditional filler-type conductive adhesive, it is not easy to produce precipitation and agglomeration, making the conductivity of each part between the capacitor shell and the electrode plate more balanced, and greatly improving the stability of the supercapacitor.

[0018] Since the binder is more easily and quickly dissolved at a higher temperature, the first solvent with a higher boiling point is used as the dissolution medium for the binder in this application. The second solvent with a lower boiling point is mainly used to increase the volatility of the solvent in the conductive adhesive, making the conductive adhesive easier to dry and cure in subsequent applications and saving production time.

[0019] Through experiments, using the weight percentage ratio of the first solvent and the second solvent in the conductive adhesive system in this application can not only ensure that the binder forms a conductive film with an ideal thickness and flexibility, but also is conducive to improving the film-forming speed of the conductive adhesive during the drying process, making the uniformity of the conductive adhesive film higher and the flexibility better.

[0020] Preferably, the conductive adhesive matrix is one or a combination of polypyrrole, polyphenylene sulfide, phthalocyanine-based compounds, polyacetylene, polythiophene, polysulfonic acid, polyaniline, polyphenylene, polyphenylene vinylene, polyene diyne.

[0021] Preferably, the conductive adhesive matrix is an aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS).

[0022] By adopting the above technical solution, the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) is an aqueous dispersion of polythiophene / polysulfonic acid, which has good conductivity and thermal stability, and has good conductivity as the matrix of the conductive adhesive. Moreover, the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) itself is a highly dispersed water-based dispersion system, which is beneficial to improving the dispersion uniformity of the conductive adhesive.

[0023] Preferably, the solid content of the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) is 2% - 5%, the particle size D90 of the conductive polymer particles in the aqueous dispersion is 100 nm, and the viscosity is 10 - 35 mPa·s.

[0024] By adopting the above technical solution, in this particle size range, the conductive adhesive system is more uniformly dispersed, and controlling the solid content within 2% - 5% can ensure that the conductive adhesive has good conductivity.

[0025] Preferably, the binder is one or a combination of several of polyacrylamide, polyvinyl alcohol, polyethylene glycol, polyethylene glycol carboxylate, polyvinyl acetate, and polyacrylate.

[0026] By adopting the above technical solution, these several high molecular polymers all have adhesive properties and can form a good film after being dissolved in an organic solvent and dried subsequently.

[0027] Preferably, the binder is polyvinyl alcohol, and the auxiliary agent is one or a combination of several of boric acid, ammonium pentaborate, and boron trioxide.

[0028] By adopting the above technical solution, polyvinyl alcohol not only has excellent film-forming function, but also can form a network structure with boric acid, ammonium pentaborate, and boron trioxide, which has a good supporting effect on the matrix material of the conductive adhesive, can suspend the conductive adhesive matrix particles well in the conductive adhesive system, and combined with the high dispersion performance of the dispersant, so that the conductive adhesive matrix particles are more stably dispersed without aggregation, agglomeration, and precipitation, which is beneficial to improving the stability of the system.

[0029] Preferably, the auxiliary agent is boric acid.

[0030] By adopting the above technical solution, boric acid is more stable at room temperature, easy to store, and boric acid has a low price and low cost.

[0031] The cross-linking reaction between polyvinyl alcohol and boric acid is as follows:

[0032]

[0033] Preferably, the boiling point of the first solvent is above 155 °C.

[0034] By adopting the above technical solution, the dissolution rate of polyvinyl alcohol at high temperature is faster. Through experiments, polyvinyl alcohol and boron compounds can be quickly dissolved and miscible at 125-155 °C. Therefore, controlling the boiling point of the first solvent above 155 °C can greatly reduce volatilization and loss.

[0035] Preferably, the first solvent is one or a combination of several of ethylene glycol, benzyl alcohol, cyclohexanone, dimethyl phthalate, and diethyl phthalate.

[0036] By adopting the above technical solution, the boiling points of these solvents are all above 155 °C, which can well adapt to the high temperature when heating the binder polyvinyl alcohol and the auxiliary boron compound, and the volatilization and loss of the solvent are very small.

[0037] Preferably, the first solvent is ethylene glycol.

[0038] By adopting the above technical solution, since the conductive adhesive matrix is a highly dispersed aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS), using hydrophilic ethylene glycol as the first solvent is more compatible with the aqueous dispersion characteristics of the conductive adhesive matrix, which is beneficial to making the system more uniform.

[0039] Preferably, the second solvent is one or a combination of several of acetone, ethanol, acetonitrile, isopropanol, n-propanol, and methyl ethyl ketone.

[0040] By adopting the above technical solution, choosing a hydrophilic solvent as the second solvent is more miscible with the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS), which is beneficial to improving the dispersibility of the system.

[0041] Preferably, the second solvent is acetone.

[0042] By adopting the above technical solution, acetone is a common and easily obtained organic solvent, which is extremely soluble in water, and its boiling point is low, only 56.53 °C. It is easy to take away the moisture in the conductive adhesive during the drying process of the conductive adhesive, which has a promoting effect on the rapid film formation of the conductive adhesive.

[0043] Preferably, the dispersant is a compound dispersant, and the compound dispersant includes the following components in parts by weight:

[0044] 2-acetamidothiazolyl decylammonium chloride 3 parts;

[0045] Dynol604 nonionic surfactant 1 part;

[0046] Glycerol 6 parts;

[0047] 90 parts of deionized water.

[0048] By adopting the above technical solution, the molecular structural formula of 2-acetamidothiazolyl decylammonium chloride is as follows:

[0049]

[0050] As a cationic surfactant, 2-acetamidothiazolyl decylammonium chloride contains an amide bond in its molecular structure. The amide bond is an electron-withdrawing group. Especially, the electronegativity of the sulfur atom and nitrogen atom on the heterocyclic ring makes the amide bond have stronger electron-withdrawing properties, thus improving the positive charge density of the head group of the cationic surfactant. This not only increases the adsorption ability of the cationic surfactant molecule but also enhances the conductive function of the conductive adhesive. Dynol60 nonionic surfactant is less likely to generate foam during the production process compared with traditional fluorocarbon surfactants and silicone surfactants. Glycerol has extremely strong hydrophilicity and is extremely easy to attach to the hydrophilic end of the surfactant, increasing the solubility of the two surfactants in water, facilitating the dissolution rate of the two surfactants, and also having the effect of softening the conductive adhesive and improving the flexibility of the conductive adhesive after drying and curing into a film.

[0051] By using this compound dispersant, the uniform dispersion degree of the conductive adhesive matrix in the conductive adhesive can be well promoted, and the adhesion ability of the conductive adhesive can be improved.

[0052] Preferably, the conductive enhancer is one or a combination of several of tetrahydrofuran, γ-butyrolactone, N-methylpyrrolidone, N-methylformamide, sulfolane, dimethyl sulfoxide.

[0053] By adopting the above technical solution, these several organic compounds all contain C-O, N-O or S-O chemical bonds, which are strong electron-withdrawing chemical bonds. They can change the electron cloud density distribution in the compound system, presenting a weak electrostatic system. When placed in an electric field, they will promote the movement of electrons or charged ions to enhance the electric property, which is beneficial to improving the conductive performance of the conductive adhesive.

[0054] Preferably, the conductive enhancer is sulfolane.

[0055] By adopting the above technical solution, sulfolane is an excellent aprotic polar organic compound, with the characteristics of low melting point, high boiling point, good stability, low process processing difficulty, and sulfolane is more easily soluble. Combining with the hydrophilicity of the conductive adhesive system, it has the effect of improving the dispersibility and uniformity of the system.

[0056] In the second aspect, the present application provides a preparation method of a conductive adhesive for a supercapacitor, adopting the following technical solution:

[0057] A preparation method of a conductive adhesive for a supercapacitor includes the following steps:

[0058] Dissolution: Stir and heat the first solvent to 60 - 80°C. Under stirring, first add the binder, and then add the auxiliary agent at a rate of 50 - 100 ml per minute. Then raise the temperature to 125 - 155°C. After the system is completely dissolved, cool it down to 35 - 50°C to obtain the adhesive solution;

[0059] Dispersion: Add the conductive adhesive matrix to the adhesive solution in 5 - 8 batches under stirring. Then control the stirring speed at 1350 - 1650 rpm and stir at a high speed at 35 - 50°C for 1 - 2 hours. Then add the dispersant to the mixed system, keep the temperature and speed unchanged, and stir at a constant temperature for 30 - 90 min. Then perform ultrasonic dispersion for 30 - 80 minutes, with the resonance frequency of 20 - 40 kHz. Then cool it down to 30 - 35°C to obtain the dispersed adhesive liquid system;

[0060] Mixing: Add the second solvent and the conductive enhancer to the dispersed adhesive liquid system respectively, and control the stirring speed at 450 - 850 rpm and stir for 3 - 5 hours to make the system fully mixed evenly to obtain the finished conductive adhesive.

[0061] By adopting the above preparation method, it is easier for the binder to dissolve at high temperature. The method of adding the conductive adhesive matrix to the system in multiple batches can improve the dispersion effect of the conductive adhesive matrix and reduce the agglomeration probability of the particles in the conductive adhesive matrix.

[0062] The process conditions of the preparation method of this application are simple, the operation difficulty is low, the obtained conductive adhesive system is more evenly dispersed, and it is not easy to appear agglomeration or precipitation phenomena. The obtained conductive adhesive is in a flowing state, which is convenient for subsequent use. When in use, the conductive adhesive of this application can be sprayed into the relevant components of the supercapacitor by means of jet dispensing. It can not only inject the glue accurately, and it is easy to control the amount of the injected conductive adhesive evenly, and the glue injection effect is good, which can keep the conductivity of each part between the capacitor shell and the electrode plate balanced, but also can realize automatic operation and improve the production efficiency.

[0063] In summary, this application includes at least one of the following beneficial technical effects:

[0064] 1. This application uses a conductive polymer material as the conductive adhesive matrix, adds a conductive enhancer to further improve the conductivity, and adds a binder to enhance the adhesion of the conductive adhesive. The combination of each component makes the prepared conductive adhesive have good fluidity, more excellent conductivity, good dispersion effect, more uniform conductive adhesive system. Compared with the traditional filler-type conductive adhesive, it is not easy to produce precipitation and agglomeration, making the conductivity of each part between the capacitor shell and the electrode plate more balanced, greatly improving the stability of the supercapacitor. In addition, this application uses a double-solvent system of a first solvent with a higher boiling point and a second solvent with a lower boiling point, which can not only ensure that the binder forms a conductive film with an ideal thickness and flexibility, but also is conducive to improving the film-forming speed of the conductive adhesive during the drying process, making the uniformity of the conductive adhesive film higher and the flexibility better.

[0065] 2. Polyvinyl alcohol is used as the binder and boron compound is used as the auxiliary agent. Polyvinyl alcohol not only has excellent film-forming function, but also can form a network structure with the boron compound, having a good supporting effect on the conductive adhesive matrix material, and can suspend the conductive adhesive matrix particles well in the conductive adhesive system. Combining with the high dispersion performance of the dispersant, the conductive adhesive matrix particles can be more stably dispersed without aggregation, agglomeration and precipitation, which is beneficial to improving the stability of the system.

[0066] 3. In the compound dispersant used in this application, 2-acetamidothiazolyl decyl ammonium chloride is used as a cationic surfactant. Its molecular structure contains an electron-withdrawing group amide bond. The electronegativity of the sulfur atom and nitrogen atom on its heterocyclic ring makes the amide bond have stronger electron-withdrawing properties, thus increasing the positive charge density of the cationic surfactant head group, not only increasing the adsorption ability of the cationic surfactant molecule, but also enhancing the conductive function of the conductive adhesive. Dynol60 non-ionic surfactant is not easy to generate foam during the production process compared with traditional fluorocarbon surfactants and silicone surfactants. Glycerol has extremely strong hydrophilicity and is easily attached to the hydrophilic end of the surfactant, increasing the solubility of the two surfactants in water, being conducive to accelerating the dissolution speed of the two surfactants, and also having the effect of softening the conductive adhesive and improving the flexibility of the conductive adhesive after drying and curing into a film. The combination of the three can well promote the uniform dispersion degree of the conductive adhesive matrix in the conductive adhesive and improve the adhesion ability of the conductive adhesive.

[0067] 4. The preparation process conditions of the conductive agent in this application are simple, with low operation difficulty. The prepared conductive adhesive system is more uniformly dispersed, not easy to appear agglomeration or precipitation phenomenon. The prepared conductive adhesive is in a flowing state, which is convenient for subsequent use and is easy to spray the conductive adhesive of this application into the supercapacitor by means of jet dispensing. The glue injection is accurate, and automated operation can be realized, improving production efficiency. Detailed implementation mode

[0068] When a supercapacitor is manufactured, a conductive adhesive needs to be added between the inner wall of the capacitor housing and the electrode plate to fix and bond the electrode plate to the bottom surface of the capacitor metal case, and at the same time, it also plays a role in improving the conductivity between the capacitor housing and the electrode plate. However, the currently used filler-type conductive adhesive, which uses an adhesive as the matrix and makes the adhesive liquid conductive by adding conductive fillers to the adhesive, has a thorny problem in use. The solid particles of the conductive fillers in the conductive adhesive are prone to precipitation, resulting in easy stratification of the conductive adhesive. When coating, due to the uneven distribution of the conductive fillers in the conductive adhesive system, there will be differences in the conductivity of each part between the capacitor housing and the electrode plate, affecting the performance of the supercapacitor.

[0069] For the above reasons, in order to achieve the purpose of making the conductive adhesive system more uniformly dispersed and improving the conductivity of each part between the supercapacitor housing and the electrode plate, after a large amount of research, this application has developed a conductive adhesive using a conductive polymer material as the conductive adhesive matrix, added a conductive enhancer to further improve the conductivity, added a dispersant to improve the uniformity of the system dispersion, and added a binder to enhance the adhesion of the conductive adhesive. In particular, polyvinyl alcohol is used as the binder, and a boron compound is used as an auxiliary agent. Polyvinyl alcohol and the boron compound can form a network structure, which can suspend the conductive adhesive matrix particles well in the conductive adhesive system. Combining with the high dispersion performance of the dispersant, the conductive adhesive matrix particles can be more stably dispersed and are not easy to aggregate, agglomerate or precipitate.

[0070] To more conveniently understand the technical solution of this application, the following further elaborates on this application in combination with tables and examples, but it does not serve as the limited protection scope of this application.

[0071] The following are the sources of some raw materials in the examples of this application:

[0072] Poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) aqueous dispersion, from Guangdong Huahong Technology Co., Ltd., model AL-16;

[0073] 2-Acetamidothiazolyl decylammonium chloride, from the synthetic sample of the applicant's laboratory;

[0074] Dynol604 non-ionic surfactant, from APCI, Air Products and Chemicals, Inc., USA;

[0075] The remaining raw materials are conventionally selected.

[0076] Preparation examples of raw materials and / or intermediates

[0077] Preparation Example 1

[0078] The preparation method of the compound dispersant is as follows: Add 3 parts of 2-acetamidothiazolyl decyl ammonium chloride, 1 part of Dynol604 nonionic surfactant, and 6 parts of glycerol auxiliary agent into a container, and then add 90 parts of deionized water to obtain a mixed solution. Use an intelligent numerical control ultrasonic homogenizing disperser to vibrate at a resonance frequency of 20 - 40 kHz at room temperature for 90 minutes until it is completely dissolved to obtain the compound dispersant.

[0079] Example

[0080] Example 1

[0081] Component ratio: By weight percentage, take 31.20% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion as the conductive adhesive matrix, take 54.30% of ethylene glycol as the first solvent, take 5.20% of acetone as the second solvent, take 1.85% of polyvinyl alcohol (PVA) as the binder, take 1.50% of boric acid as the auxiliary agent, take 1.50% of the compound dispersant, and take 4.45% of sulfolane as the conductive enhancer.

[0082] Preparation method:

[0083] Dissolution: First, pour ethylene glycol into a stainless steel container, stir and heat it to 80 °C, then add polyvinyl alcohol, then adjust the stirring speed to 30 rpm, add boric acid at a speed of 100 ml per minute, then raise the temperature to 145 °C, and after polyvinyl alcohol and boric acid are completely dissolved, cool it to 50 °C to obtain an adhesive solution;

[0084] Dispersion: Add the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion into the adhesive solution in 8 portions, keep it at a constant temperature of 50 °C and stir at a high speed of 1600 rpm for 1 hour, then add the compound dispersant into the mixed system, keep the temperature and stirring speed unchanged, continue to stir at a constant temperature for 1 hour, and then perform ultrasonic dispersion on the mixed system for 40 minutes, and then cool it to 35 °C to obtain a dispersed adhesive liquid system;

[0085] Mixing: Add acetone and sulfolane into the dispersed adhesive liquid system respectively, and stir at a speed of 650 rpm for 4 hours to fully mix the conductive adhesive mixed system to obtain a flowing conductive adhesive.

[0086] Example 2

[0087] The difference from Example 1 is that, by weight percentage, 40.22% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 35.30% of ethylene glycol is taken as the first solvent, 10.25% of acetone is taken as the second solvent, 2.23% of polyvinyl alcohol (PVA) is taken as the binder, 1.85% of boric acid is taken as the auxiliary agent, 2.50% of the compound dispersant is taken, and 7.65% of sulfolane is taken as the conductive enhancer.

[0088] Example 3

[0089] The difference from Example 1 is that, by weight percentage, 36.25% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 42.50% of ethylene glycol is taken as the first solvent, 8.00% of acetone is taken as the second solvent, 3.15% of polyvinyl alcohol (PVA) is taken as the binder, 2.35% of boric acid is taken as the auxiliary agent, 2.00% of the compound dispersant is taken, and 5.75% of sulfolane is taken as the conductive enhancer.

[0090] Example 4

[0091] The difference from Example 1 is that, by weight percentage, 42.40% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 36.32% of ethylene glycol is taken as the first solvent, 8.50% of acetone is taken as the second solvent, 2.15% of polyvinyl alcohol (PVA) is taken as the binder, 1.85% of boric acid is taken as the auxiliary agent, 2.80% of the compound dispersant is taken, and 5.98% of sulfolane is taken as the conductive enhancer.

[0092] Example 5

[0093] The difference from Example 1 is that, by weight percentage, 34.20% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 48.20% of ethylene glycol is taken as the first solvent, 7.10% of acetone is taken as the second solvent, 2.10% of polyvinyl alcohol (PVA) is taken as the binder, 1.75% of boric acid is taken as the auxiliary agent, 3.50% of the compound dispersant is taken, and 3.15% of sulfolane is taken as the conductive enhancer.

[0094] Example 6

[0095] The difference from Example 1 is that, by weight percentage, 30.00% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 55.00% of ethylene glycol is taken as the first solvent, 4.50% of acetone is taken as the second solvent, 1.50% of polyvinyl alcohol (PVA) is taken as the binder, 1.50% of boric acid is taken as the auxiliary agent, 1.50% of the compound dispersant is taken, and 6.00% of sulfolane is taken as the conductive enhancer.

[0096] Example 7

[0097] The difference from Example 1 is that, by weight percentage, 45.00% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 35.00% of ethylene glycol is taken as the first solvent, 7.50% of acetone is taken as the second solvent, 3.50% of polyvinyl alcohol (PVA) is taken as the binder, 2.50% of boric acid is taken as the auxiliary agent, 3.50% of the compound dispersant is taken, and 3.00% of sulfolane is taken as the conductive enhancer.

[0098] Example 8

[0099] The difference from Example 1 is that, by weight percentage, 34.50% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 40.00% of ethylene glycol is taken as the first solvent, 10.50% of acetone is taken as the second solvent, 2.50% of polyvinyl alcohol (PVA) is taken as the binder, 2.00% of boric acid is taken as the auxiliary agent, 2.50% of the compound dispersant is taken, and 8.00% of sulfolane is taken as the conductive enhancer.

[0100] Example 9

[0101] The difference from Example 1 is that the binder is polyacrylamide.

[0102] Example 10

[0103] The difference from Example 1 is that the binder is polyethylene glycol.

[0104] Example 11

[0105] The difference from Example 1 is that the second solvent is methyl ethyl ketone and the conductive enhancer is γ-butyrolactone.

[0106] Example 12

[0107] The difference from Example 1 is that the second solvent is isopropyl alcohol and the conductive enhancer is tetrahydrofuran.

[0108] Example 13

[0109] The difference from Example 1 is that the second solvent is acetonitrile and the conductive enhancer is N-methylformamide.

[0110] Comparative Example

[0111] In each comparative example, the proportion of the conductive adhesive matrix is the same as that in Example 8.

[0112] Comparative Example 1

[0113] Component ratio: By weight percentage, take 31.20% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion as the conductive adhesive matrix, take 54.30% of ethylene glycol as the first solvent, take 6.70% of acetone as the second solvent, take 1.85% of polyvinyl alcohol (PVA) as the binder, take 1.50% of the compound dispersant, and take 4.45% of sulfolane as the conductive enhancer.

[0114] Preparation method:

[0115] First, put ethylene glycol into a stainless steel container and stir and heat it to 80°C. Then add polyvinyl alcohol and raise the temperature to 145°C. After the polyvinyl alcohol is completely dissolved, cool it down to 50°C. Then add the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion into the mixed system in 8 portions, keep it at a constant temperature of 50°C and stir at a high speed of 1600 rpm for 1 hour. Then add the compound dispersant into the mixed system, keep the temperature and stirring speed unchanged, continue to stir at a constant temperature for 1 hour, then perform ultrasonic dispersion on the mixed system for 40 minutes, cool it down to 35°C, and then add acetone and sulfolane into the dispersed glue liquid system respectively, and stir at a speed of 650 rpm for 4 hours to fully mix the conductive adhesive mixed system to obtain a flowing conductive adhesive.

[0116] Comparative Example 2

[0117] Component ratio: By weight percentage, take 31.20% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion as the conductive adhesive matrix, take 54.30% of ethylene glycol as the first solvent, take 6.70% of acetone as the second solvent, take 1.85% of polyvinyl alcohol (PVA) as the binder, take 1.50% of boric acid as the auxiliary agent, and take 4.45% of sulfolane as the conductive enhancer.

[0118] Preparation method:

[0119] First, put ethylene glycol into a stainless-steel container, stir and heat it to 80 °C, then add polyvinyl alcohol. Next, adjust the stirring speed to 30 rpm, add boric acid at a speed of 100 ml per minute, then raise the temperature to 145 °C. After the polyvinyl alcohol and boric acid are completely dissolved, cool it down to 50 °C. Then, add the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) to the adhesive solution in 8 portions, keep it at a constant temperature of 50 °C and stir at a high speed of 1600 rpm for 1 hour. Then, ultrasonically disperse the mixed system for 40 minutes, and then cool it down to 35 °C. Add acetone and sulfolane to the dispersed adhesive solution system respectively, and stir at a speed of 650 rpm for 4 hours to fully mix the conductive adhesive mixed system, obtaining a flowing conductive adhesive.

[0120] Comparative Example 3

[0121] Component ratio: By weight percentage, take 31.20% of the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) as the conductive adhesive matrix, take 54.30% of ethylene glycol as the first solvent, take 9.65% of acetone as the second solvent, take 1.85% of polyvinyl alcohol (PVA) as the binder, take 1.50% of boric acid as the auxiliary agent, and take 1.50% of the compound dispersant.

[0122] Preparation method:

[0123] First, put ethylene glycol into a stainless-steel container, stir and heat it to 80 °C, then add polyvinyl alcohol. Next, adjust the stirring speed to 30 rpm, add boric acid at a speed of 100 ml per minute, then raise the temperature to 145 °C. After the polyvinyl alcohol and boric acid are completely dissolved, cool it down to 50 °C. Then, add the aqueous dispersion of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) to the mixed system in 8 portions, keep it at a constant temperature of 50 °C and stir at a high speed of 1600 rpm for 1 hour. Then, add the compound dispersant to the mixed system, keep the temperature and stirring speed unchanged, and continue to stir at a constant temperature for 1 hour. Then, ultrasonically disperse the mixed system for 40 minutes, cool it down to 35 °C, and then add acetone to the dispersed adhesive solution system, and stir at a speed of 650 rpm for 4 hours to fully mix the conductive adhesive mixed system, obtaining a flowing conductive adhesive.

[0124] Comparative Example 4

[0125] The difference from Example 1 is that, by weight percentage, 30.00% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 60.00% of ethylene glycol is taken as the first solvent, 2.50% of acetone is taken as the second solvent, 1.50% of polyvinyl alcohol (PVA) is taken as the binder, 1.50% of boric acid is taken as the auxiliary agent, 1.50% of the compound dispersant is taken, and 3.00% of sulfolane is taken as the conductive enhancer.

[0126] Comparative Example 5

[0127] The difference from Example 1 is that, by weight percentage, 37.50% of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) aqueous dispersion is taken as the conductive adhesive matrix, 30.00% of ethylene glycol is taken as the first solvent, 15.00% of acetone is taken as the second solvent, 3.50% of polyvinyl alcohol (PVA) is taken as the binder, 2.50% of boric acid is taken as the auxiliary agent, 3.50% of the compound dispersant is taken, and 8.00% of sulfolane is taken as the conductive enhancer.

[0128] Performance detection test

[0129] Detection items: discharge capacity, leakage current, ESR (equivalent series resistance).

[0130] Detection standard: IEC 62391-1.

[0131] Test method:

[0132] The conductive adhesives prepared in Examples 1-13 and Comparative Examples 1-5 are respectively filled into the syringe liquid storage box in the electrode attachment device. Then, the cleaned metal shell of the supercapacitor is placed on the production line conveyor belt. Through the injection dispensing process, a certain amount of conductive adhesive is injected into the metal shell of the supercapacitor at one time. The electrode attachment device automatically places the electrode plate into the metal shell of the supercapacitor. After compaction and attaching the separator paper, processes such as drying, cleaning, and leak detection are carried out. Then, operations such as injecting the supercapacitor electrolyte, adding the shell cover, and sealing are performed to make a supercapacitor monomer. Then, operations such as aging, testing, assembling the sleeve, welding the connection seat, and welding the pins are carried out on the supercapacitor monomer. Finally, button-type supercapacitor samples with a specification of 5.5V / 0.22F are prepared. Ten supercapacitors prepared with the conductive adhesives of Examples 1-13 and Comparative Examples 1-5 are taken for the following tests, and the average value of the test results is taken.

[0133] Capacity Test: Using the constant current discharge method, the capacitance deviation should be not less than 80% and not more than 180% of the rated capacitance, that is, the discharge capacity should be between 0.176 and 0.396 F. The larger the discharge capacity within this range, the better the electrical performance of the supercapacitor. Connect the supercapacitor to a DC circuit with a constant current / constant voltage source. After the constant current / constant voltage source reaches the rated voltage U R perform constant voltage charging for 30 minutes, then connect the supercapacitor to a circuit with a constant current discharge device and discharge it at a constant current I, measure the voltage across the supercapacitor, start timing at t1 when U1 = 0.8U R and stop timing at t2 when U2 = 0.4U R Calculate the discharge capacity value using the formula C = I(t2 - t1) / (U1 - U2).

[0134] Leakage Current Test: Using DC current test, the leakage current should be ≤ 0.22 mA (30 minutes). The smaller the leakage current, the better the electrical performance of the supercapacitor. Discharge the supercapacitor for 1 h, then charge it to 95% of the charging voltage. Connect the DC current range of the digital multimeter in series with the supercapacitor and then connect it to a circuit with a linear DC regulated power supply. The output voltage of the regulated power supply is lower than the rated voltage of the supercapacitor. After 10 time constants, the reading shown on the digital multimeter is the leakage current of the capacitor.

[0135] ESR Test: Using AC current test, the ESR should be ≤ 50 Ω. Measure it with an internal resistance tester. The smaller the ESR, the better the electrical performance of the supercapacitor.

[0136] Table 1: Mixing ratio table of each component of the conductive adhesive in Examples 1 - 8 and Comparative Examples 1 - 5

[0137]

[0138] Table 2: Average values of performance parameters of 5.5V / 0.22F button-type supercapacitors in Examples 1 - 13 and Comparative Examples 1 - 3

[0139]

[0140]

[0141] It can be seen from the data in Table 2 that the button-type supercapacitors made of the conductive adhesive of the present application can all meet the requirements of its electrical performance test, indicating that the conductive adhesive of the present application has excellent conductivity, and the conductivity of each part between the shell and the electrode plate of the supercapacitor made by the present application is balanced and has good stability.

[0142] Combined with the data of Examples 1-8 and Table 2, it can be seen that among them, the average value of the ESR of the button-type supercapacitor in Example 4 is the lowest, and the average value of its discharge capacity is the highest. Therefore, the component ratio of the conductive adhesive in Example 4 is a better solution.

[0143] Combined with the data of Example 1, Examples 9-10 and Table 2, it can be seen that when the conductive adhesives prepared by using polyacrylamide and polyethylene glycol as binders are applied to supercapacitors, the average value of the discharge capacity of the supercapacitors becomes smaller, the average value of the leakage current becomes larger, and the average value of the ESR becomes larger. Although the electrical performance of the supercapacitors can meet the qualified standards, the electrical performance of the supercapacitors is better when using polyvinyl alcohol as the binder.

[0144] In addition, combined with the data of Comparative Example 1 and Comparative Example 1, it can be seen that when only polyvinyl alcohol is added, the electrical performance data of the supercapacitors are worse than those of Example 9 and Example 10. Therefore, it can be known that only when polyvinyl alcohol and boric acid cooperate with each other can the electrical conductivity of the conductive adhesive be improved better. It is detected that a network structure can be formed by the combination of polyvinyl alcohol and boron compounds, which can support the matrix material of the conductive adhesive and suspend the matrix particles of the conductive adhesive well in the conductive adhesive system, and the system is stable and uniform.

[0145] Moreover, it is found during the experiment that the film-forming effect of the conductive adhesive in Comparative Example 1 is poor after the supercapacitor is dried, and the thickness of the formed film layer is uneven, which affects the electrical performance of the supercapacitor. It can be seen that the cooperation of polyvinyl alcohol and boric acid is also beneficial to the film-forming quality after the conductive adhesive is dried.

[0146] Combined with the data of Example 1, Examples 11-13 and Table 2, it can be known that when the second solvent is acetone and the conductivity enhancer is sulfolane, the prepared conductive adhesive has better electrical conductivity, which is beneficial to improving the electrical performance of the supercapacitor.

[0147] Combined with the data of Example 1, Comparative Example 2 and Table 2, it can be seen that the average value of the discharge capacity of the supercapacitor prepared with the conductive adhesive without adding a dispersant fails to meet the qualified standard. Although the average value of the ESR can meet the qualified standard, its electrical performance is much worse than that of Example 1. It can be inferred that the dispersant is beneficial to making the conductive adhesive system more uniform, thereby improving the electrical conductivity of the conductive adhesive.

[0148] In addition, it is found during the experiment that the flexibility of the conductive adhesive in Comparative Example 2 is poor after drying. It can be seen that the dispersant is also beneficial to improving the flexibility of the conductive adhesive film after film formation.

[0149] It can be seen from the data of Example 1, Comparative Example 3 and Table 2 that the average discharge capacity and the average ESR of the supercapacitor prepared with the conductive adhesive without adding the conductive enhancer cannot reach the qualified standard. It can be seen that the conductive adhesive added with the conductive enhancer has a good effect on improving the discharge capacity of the supercapacitor and reducing the ESR of the supercapacitor, indicating that the conductive enhancer can greatly improve the conductive performance of the conductive adhesive.

[0150] After testing, when the conductive adhesive in Comparative Example 4 is applied to the supercapacitor, it is difficult to dry at a temperature of 130 °C and it is difficult to form a glue film. When the conductive adhesive in Comparative Example 5 is applied to the supercapacitor, the flexibility of the glue film formed after drying is very poor, cracking occurs, and it is difficult to form a complete glue film.

[0151] This specific embodiment is only an interpretation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A conductive adhesive for supercapacitors, characterized in that, Comprising components in the following weight percentages: Conductive adhesive matrix 30% - 45%; wherein, the conductive adhesive matrix is a conductive polymer material, specifically a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) aqueous dispersion; the solid content of the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT / PSS) aqueous dispersion is 2% - 5%, the particle size D90 of the conductive polymer particles in the aqueous dispersion is 100 nm, and the viscosity is 10 - 35 mPa·s; First solvent 35% - 55%, the boiling point of the first solvent is above 155°C, and the first solvent is ethylene glycol, serving as a dissolution medium for the binder; Second solvent 4.5% - 10.5%, the boiling point of the second solvent is 55 - 100°C, the boiling point of the first solvent is higher than that of the second solvent, and the second solvent is acetone, which is used to increase the volatility of the solvent in the conductive adhesive, making the conductive adhesive easier to dry and cure in subsequent applications; Binder 1.5% - 3.5%, the binder is polyvinyl alcohol, which is used for film formation; Auxiliary agent 1.5% - 2.5%, the auxiliary agent is boric acid, and a network structure is formed by the polyvinyl alcohol of the binder and the boron compound of the auxiliary agent to suspend the particles of the conductive adhesive matrix in the conductive adhesive system; Dispersant 1.5% - 3.5%, the dispersant is a compound dispersant, and the compound dispersant comprises components in the following weight ratio: 2-acetamidothiazolyl decyl ammonium chloride 3 parts; Dynol604 non-ionic surfactant 1 part; glycerol 6 parts; deionized water 90 parts; the compound dispersant can promote the uniform dispersion degree of the conductive adhesive matrix in the conductive adhesive and improve the adhesion ability of the conductive adhesive; Conductive enhancer 3% - 8%, the conductive enhancer is sulfolane, which is used to further improve the conductivity of the conductive adhesive.

2. A preparation method of the conductive adhesive for supercapacitors as described in claim 1, characterized in that, Including the following steps: Dissolution: Stir and heat the first solvent to 60 - 80°C, first add the binder under stirring, then add the auxiliary agent at a speed of 50 - 100 ml per minute, then raise the temperature to 125 - 155°C, and after the system is completely dissolved, cool it to 35 - 50°C to obtain an adhesive solution; Dispersion: Add the conductive adhesive matrix to the adhesive solution in 5 - 8 portions under stirring, then control the stirring speed at 1350 - 1650 rpm and stir at a high speed at 35 - 50°C for 1 - 2 hours, then add the dispersant to the mixed system, keep the temperature and speed unchanged, stir at a constant temperature for 30 - 90 min, then perform ultrasonic dispersion for 30 - 80 minutes, with a resonance frequency of 20 - 40 kHz, and then cool it to 30 - 35°C to obtain a dispersed adhesive liquid system; Mixing: Add the second solvent and the conductive enhancer to the dispersed adhesive liquid system respectively, control the stirring speed at 450 - 850 rpm and stir for 3 - 5 hours to make the system fully mixed and uniform to obtain the finished conductive adhesive.

Images