Electrically-conductive composite water-based binder as well as preparation method therefor and use thereof

Abstract

The present invention provides an electrically-conductive composite water-based binder as well as a preparation method therefor and the use thereof. The electrically-conductive composite water-based binder comprises in parts by weight: 90-100 parts of a polyacrylic acid or polyacrylate water-based binder and 0.1-10 parts of an electrically-conductive filler. By means of introducing the electrically-conductive filler into the binder, the electrically-conductive composite water-based binder for lithium ion batteries which has flexibility, low swelling, good binding force and high conductivity is prepared, so that the binder plays a better role in lithium ion batteries.

Description

A conductive composite water-based adhesive and its preparation method and application

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on August 30, 2023, with application number 202311106535.2 and application name “A conductive composite water-based adhesive, its preparation method and application”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention belongs to the technical field of water-based adhesives, and in particular relates to a conductive composite water-based adhesive and a preparation method and application thereof. Background Art

[0003] Lithium-ion batteries, as secondary batteries, are widely used in a variety of fields due to their advantages, including high energy conversion rate, high energy density, high charge and discharge rate, no memory effect, and environmental friendliness. Polymer binders, with their excellent bonding properties, can bind various particles together and tightly bond them to the current collector, making them an indispensable component of lithium-ion batteries. In addition to high adhesion, high-performance binders also require the following properties: good flexibility, electrolyte resistance, compactness, chemical and electrochemical stability, low cost, and environmental friendliness.

[0004] Currently, the binders used in lithium-ion batteries fall into three main categories: polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex and carboxymethyl cellulose (SBR / CMC), and polyacrylic acid (PAA). PVDF offers advantages such as good adhesion to aluminum foil and strong resistance to electrochemical corrosion, but poor adhesion to copper foil. PVDF also has a large molecular weight and lacks hydrophilic groups, making it commonly dispersed and dissolved in N-methylpyrrolidone (NMP). However, NMP solvent is sensitive to moisture, toxic, and its volatilization can pollute the environment. SBR / CMC binders have poor process performance and demanding processing conditions, significantly affected by factors such as stirring, pH, and electrode material ratio. Both PVDF and SBR / CMC are relatively expensive. PAA binders, with their strong adhesion, excellent stability, low price, and environmental friendliness, are currently a hot topic in negative electrode binder research.

[0005] Although the binder can tightly bond the slurry, its low electrical conductivity can hinder lithium ion migration, leading to reduced charge and discharge efficiency in lithium-ion batteries. Therefore, by compounding the PAA binder, the conductivity is further improved while simultaneously meeting the requirements of high bonding strength, low swelling rate, and flexibility.

[0006] Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention aims to provide a conductive composite water-based adhesive and a preparation method and application thereof.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides a conductive composite water-based adhesive, which comprises, by weight, 90-100 parts of a polyacrylic acid or polyacrylate water-based adhesive and 0.1-10 parts of a conductive filler.

[0010] In the present invention, a conductive composite water-based binder for lithium-ion batteries is prepared by introducing a conductive filler into the binder, which has the characteristics of flexibility, low swelling, good bonding strength and high conductivity, so that the binder plays a stronger role in the lithium-ion battery.

[0011] Preferably, the polyacrylic acid or polyacrylate aqueous binder is a polymer obtained by polymerizing monomers, and the polymerized monomers include hard monomers, soft monomers and functional monomers;

[0012] The hard monomer is selected from one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate or styrene;

[0013] The soft monomer is selected from one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, tert-butyl carbonate, tetrahydrofurfuryl acrylate, lauric acrylate, lauryl methacrylate, isodecyl acrylate or ethoxyethoxyethoxy acrylate;

[0014] The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate or a silane coupling agent.

[0015] In the present invention, the hard monomers provide hardness to the binder, the soft monomers provide flexibility and promote film formation, and the functional monomers introduce functional groups or crosslinking points into the binder to improve adhesion. The combination of the hard monomers, soft monomers, and functional monomers results in a polyacrylic acid or polyacrylate water-based binder with high adhesion, good flexibility, and electrochemical stability.

[0016] Preferably, the amount of the hard monomer in the polymerizable monomer is 30 to 70 parts by weight (for example, 30 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 60 parts by weight or 70 parts by weight), the amount of the soft monomer is 30 to 70 parts by weight (for example, 30 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 60 parts by weight or 70 parts by weight), and the amount of the functional monomer is 0.5 to 15 parts by weight (for example, 0.5 parts by weight, 1 part by weight, 3 parts by weight, 5 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight or 15 parts by weight).

[0017] In the present invention, by selecting the amounts of the hard monomer, soft monomer, and functional monomer used in the polymerization, the resulting polyacrylic acid or polyacrylate water-based adhesive can be made to have good flexibility and high adhesion. In the present invention, if the amount of hard monomer used is too much, the adhesive film after the solvent evaporates will be hard, resulting in poor flexibility and loss of adhesion. If the amount of hard monomer used is too little, the adhesive film obtained after the solvent evaporates will be soft, with poor cohesion and reduced tear resistance, and easily broken by external forces.

[0018] In the present invention, if the amount of the functional monomer is too much, the pre-emulsion is easily demulsified and the preparation process performance is poor. If the amount of the functional monomer is too little, the overall bonding performance is reduced and the swelling is high.

[0019] The polyacrylic acid or polyacrylate water-based binder of the present invention is obtained by emulsion polymerization. The preparation method of the polyacrylic acid or polyacrylate water-based binder of the present invention comprises the following steps:

[0020] (1) preparing pre-emulsion, seed emulsion, bottom reaction liquid and initiator solution;

[0021] (2) adding seed emulsion to the reaction liquid at the bottom of the kettle, heating, adding part of the initiator solution, and reacting;

[0022] (3) adding the pre-emulsion and the remaining initiator solution to the reaction solution obtained in step (2), reacting to obtain the polyacrylic acid or polyacrylate aqueous binder.

[0023] Preferably, the pre-emulsion is prepared from hard monomers, soft monomers, functional monomers, emulsifiers and deionized water.

[0024] Preferably, the pre-emulsion comprises 30 to 70 parts by weight of a hard monomer, 30 to 70 parts by weight of a soft monomer, and 0.5 to 15 parts by weight of a functional monomer.

[0025] Preferably, the total weight percentage of the hard monomer, soft monomer and functional monomer in the pre-emulsion is 30-500% of deionized water, for example 30%, 60%, 100%, 150%, 200%, 250%, 300%, 350%, 400%, 450% or 500%.

[0026] Preferably, the amount of emulsifier in the pre-emulsion is 0.25-5% of the total weight of the hard monomer, soft monomer and functional monomer, such as 0.25%, 0.3%, 0.5%, 1%, 2%, 3%, 4% or 5%.

[0027] Preferably, the seed emulsion is a portion of the pre-emulsion taken out from the pre-emulsion.

[0028] Preferably, the bottom reaction liquid is prepared from an emulsifier, deionized water and a buffer.

[0029] Preferably, the reaction liquid at the bottom of the kettle includes the following components in parts by weight: 0.1-5 parts (for example, 0.1 parts, 0.5 parts, 1 parts, 2 parts, 3 parts, 4 parts or 5 parts) of emulsifier, 66-900 parts (for example, 66 parts, 80 parts, 100 parts, 200 parts, 300 parts, 500 parts, 800 parts or 900 parts) of deionized water, and 0.25-1 part (for example, 0.25 parts, 0.5 parts, 0.8 parts or 1 parts) of buffer.

[0030] Preferably, the emulsifiers in the pre-emulsion and the bottom reaction liquid are independently selected from one or a combination of at least two of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene octylphenol ether-10, sodium allyl hydroxypropyl sulfonate, allyloxy fatty alcohol oxyethylene ether ammonium sulfate, disodium succinate nonylphenol polyoxyethylene ether monoester sulfonate, lauryl alcohol ethoxylate, isomeric tridecyl alcohol ethoxylate or fatty acid methyl ester ethoxylate.

[0031] Preferably, the buffer is one or a combination of at least two of sodium bicarbonate, ammonia water, ammonium bicarbonate or sodium hydroxide.

[0032] Preferably, the initiator solution comprises an initiator and deionized water.

[0033] Preferably, the amount of deionized water in the initiator solution is 1 to 20 parts relative to 1 part by weight of the initiator, for example, 1 part, 3 parts, 5 parts, 8 parts, 10 parts, 13 parts, 15 parts, 18 parts or 20 parts.

[0034] Preferably, the initiator is selected from inorganic peroxide initiators.

[0035] Preferably, the initiator is selected from any one of potassium persulfate, ammonium persulfate or sodium persulfate, or a combination of at least two thereof.

[0036] Preferably, the amount of the initiator in the initiator solution is 0.2-0.6% of the total weight percentage of the hard monomer, the soft monomer and the functional monomer, such as 0.2%, 0.3%, 0.4%, 0.5% or 0.6%.

[0037] Preferably, the reaction in step (2) and step (3) is carried out under stirring, and the stirring speed is 100-500r / min (for example, 100r / min, 150r / min, 200r / min, 250r / min, 300r / min, 350r / min, 400r / min, 450r / min, 500r / min).

[0038] Preferably, the bottom reaction liquid is added to a reactor at 40-80°C (e.g., 40°C, 45°C, 48°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C) before the seed emulsion in step (2).

[0039] Preferably, the heating in step (2) is to 75-85°C, such as 75°C, 78°C, 80°C, 83°C or 85°C.

[0040] Preferably, the mass of the reaction liquid at the bottom of the kettle in step (2) is 12-40 times that of the seed emulsion, for example, 12 times, 15 times, 20 times, 25 times, 30 times, 35 times or 40 times.

[0041] Preferably, the portion of the initiator solution in step (2) is 5-45% of the total weight of the initiator solution, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%.

[0042] Preferably, the reaction time of step (2) is 10-60 min, for example, 10 min, 13 min, 15 min, 18 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0043] Preferably, the weight ratio of the pre-emulsion in step (3) to the bottom reaction liquid in step (2) is 0.15-2.12:1, for example, 0.15:1, 0.3:1, 0.5:1, 1:1, 1.3:1, 1.5:1, 1.8:1, 2:1 or 2.12:1, etc.

[0044] Preferably, the reaction temperature in step (3) is 80-90°C, such as 80°C, 83°C, 85°C, 88°C or 90°C.

[0045] Preferably, the reaction time of step (3) is 0.5-2.5 h, for example, 0.5 h, 0.8 h, 1 h, 1.5 h, 1.8 h, 2 h or 2.5 h.

[0046] Preferably, the preparation method further comprises cooling the temperature to 55-70°C (e.g., 55°C, 60°C, 65°C, 68°C or 70°C) after the reaction in step (3) is completed, adding a residual monomer scavenger, then cooling the temperature to below 50°C (e.g., 50°C, 45°C, 40°C, 35°C, 30°C, 25°C, 20°C or 10°C, etc.), adjusting the pH to 7-8 (e.g., 7, 7.3, 7.5, 7.8 or 8), and filtering the material.

[0047] Preferably, the residual monomer eliminator is bleaching powder and tert-butyl peroxide.

[0048] Preferably, the pH is adjusted using one or a combination of at least two of ammonia water, sodium hydroxide, lithium hydroxide, potassium hydroxide or sodium bicarbonate.

[0049] In the present invention, by designing the mass ratio of soft and hard components and functional monomer types in the pre-emulsion, a flexible and low-swelling polyacrylic acid or polyacrylate aqueous binder is obtained. By introducing carboxylic acid, carboxylate, and ester groups into the binder, the prepared polyacrylic acid or polyacrylate aqueous binder has good flexibility, electrochemical stability, and good bonding strength, and has good application prospects in lithium-ion battery negative electrode plates.

[0050] Preferably, the conductive filler is selected from any one of conductive carbon black, graphite, carbon nanotubes, graphene, polythiophene, polyacetylene, polydiyne, polyfluorene, polyparaphenylene, polyparaphenylene vinylene, polyparaphenylene vinylene, polypyrrole or polyaniline, or a combination of at least two thereof.

[0051] Preferably, the solid content of the polyacrylic acid or polyacrylate aqueous binder is 10-60%, for example, 10%, 15%, 20%, 25%, 30%, 40%, 50% or 60%.

[0052] In the present invention, the amount of the polyacrylic acid or polyacrylate aqueous binder in the conductive composite aqueous binder can be 90 parts by weight, 93 parts by weight, 95 parts by weight, 98 parts by weight, or 100 parts by weight, and the amount of the conductive filler can be 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 3 parts by weight, 5 parts by weight, 8 parts by weight, or 10 parts by weight. In the present invention, if the amount of the conductive filler is too high, it is easy to cause a decrease in bonding and swelling properties; if it is too low, the conductive effect is not obvious.

[0053] In the present invention, a conductive composite aqueous binder for lithium-ion batteries is prepared by designing the proportion of conductive fillers in the aqueous binder. By introducing conductive fillers into the binder, a conductive composite aqueous binder for lithium-ion batteries with flexibility, low swelling, good bonding strength and high conductivity is prepared, so that the binder plays a stronger role in the lithium-ion battery.

[0054] In another aspect, the present invention provides a lithium-ion battery pole piece, comprising the conductive composite aqueous binder as described above.

[0055] In another aspect, the present invention provides a lithium-ion battery, comprising the lithium-ion battery pole piece described above.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The conductive composite water-based binder of the present invention has good flexibility, low swelling, good bonding strength and high conductivity, solving the problems of low bonding, poor flexibility and low conductivity of the current binders used for negative electrodes of lithium-ion batteries. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0059] Preparation Example 1

[0060] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder is prepared, and the preparation method includes the following steps:

[0061] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0062] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 43.75 parts of methyl methacrylate, 37 parts of butyl acrylate, 9.25 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0063] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0064] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0065] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of seed emulsion were taken out from the pre-emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of initiator solution were added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.93 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain the polyacrylic acid or polyacrylate water-based binder.

[0066] Preparation Example 2

[0067] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder is prepared, and the preparation method includes the following steps:

[0068] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0069] Pre-emulsion: Dissolve 1.06 parts of disodium nonylphenol polyoxyethylene ether succinate sulfonate and 0.54 parts of isotridecyl alcohol ethoxylate in 40 parts of deionized water. Then, add 42.25 parts of methyl methacrylate, 37 parts of butyl acrylate, 9.25 parts of isooctyl acrylate, 0.5 parts of acrylamide, 8 parts of acrylic acid, and 3 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0070] A bottom reaction solution was prepared by dissolving 0.27 parts of disodium nonylphenol polyoxyethylene ether succinate sulfonate and 0.13 parts of isomeric tridecyl alcohol ethoxylate in 70 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0071] Initiator solution: Add 0.6 parts of sodium persulfate to 8 parts of deionized water to obtain an initiator aqueous solution.

[0072] (2) Add the reaction liquid at the bottom of the kettle to a reactor at 50°C at a speed of 120 rpm. Take out 8.23 ​​parts of seed emulsion from the pre-emulsion and add it to the reactor, heat it to 80°C, add 0.6 parts of initiator solution, react for 30 minutes, and then drop the remaining pre-emulsion and initiator solution at the same time. After the addition is complete, keep it warm at 87°C for 1 hour. After the insulation is completed, cool it to 65°C, add 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide, and then cool it to below 50°C. Use 1.5 parts of sodium hydroxide to adjust the pH to 7.45, filter the material, and obtain the polyacrylic acid or polyacrylate water-based binder. Preparation Example 3

[0073] In this embodiment, a polyacrylic acid or polyacrylate aqueous binder is prepared, and the preparation method includes the following steps:

[0074] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0075] Pre-emulsion: Dissolve 1.06 parts of allyloxy fatty alcohol oxyethylene ether ammonium sulfate and 0.54 parts of fatty acid methyl ester ethoxylate in 40 parts of deionized water, then add 35 parts of isopropyl methacrylate, 51.25 parts of isooctyl acrylate, 0.5 parts of methacrylamide, 6 parts of methacrylic acid, 4 parts of hydroxyethyl methacrylate, and 3.25 parts of N-hydroxymethyl acrylamide in this order for emulsification;

[0076] A bottom reaction solution was prepared by dissolving 0.27 parts of allyloxy fatty alcohol oxyethylene ether ammonium sulfate and 0.13 parts of fatty acid methyl ester ethoxylate in 80 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0077] Initiator solution: Add 0.6 parts of potassium persulfate to 10 parts of deionized water to obtain an initiator aqueous solution.

[0078] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 60°C at a speed of 120 rpm. 8.26 parts of seed emulsion were taken out from the pre-emulsion and added to the reactor. The temperature was raised to 82°C, 0.6 parts of initiator solution were added, and the reaction was continued for 45 minutes. The remaining pre-emulsion and initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.45 using 1.5 parts of lithium hydroxide. The material was filtered to obtain the polyacrylic acid or polyacrylate aqueous binder.

[0079] Example 1

[0080] At a temperature of 25° C., 100 parts of the polyacrylic acid or polyacrylate aqueous binder prepared in Preparation Example 1 were added to a container, followed by 1 part of conductive carbon black. The mixture was stirred evenly for 30 minutes to obtain a composite aqueous binder.

[0081] Example 2

[0082] At a temperature of 10° C., 100 parts of the polyacrylic acid or polyacrylate aqueous binder prepared in Preparation Example 1 were added to a container, followed by 3 parts of conductive carbon black. The mixture was stirred evenly for 30 minutes to obtain a composite aqueous binder.

[0083] Example 3

[0084] At a temperature of 20° C., 100 parts of the polyacrylic acid or polyacrylate aqueous binder prepared in Preparation Example 2 were added to a container, followed by 5 parts of conductive carbon black. The mixture was stirred evenly for 30 minutes to obtain a composite aqueous binder.

[0085] Example 4

[0086] At a temperature of 15° C., 95 parts of the polyacrylic acid or polyacrylate aqueous binder prepared in Preparation Example 2 were added to a container, followed by 3 parts of carbon nanotubes. The mixture was stirred evenly for 1 hour to obtain a composite aqueous binder.

[0087] Example 5

[0088] At a temperature of 25° C., 92 parts of the polyacrylic acid or polyacrylate aqueous binder prepared in Preparation Example 3 were added to a container, followed by 7 parts of carbon nanotubes. The mixture was stirred evenly for 45 minutes to obtain a composite aqueous binder.

[0089] Example 6

[0090] At a temperature of 30° C., 100 parts of the polyacrylic acid or polyacrylate aqueous binder prepared in Preparation Example 3 were added to a container, followed by 9 parts of graphite. The mixture was stirred evenly for 1.5 hours to obtain a composite aqueous binder.

[0091] Comparative Example 1

[0092] The polyacrylic acid or polyacrylate aqueous binder obtained in Preparation Example 1 was used as a comparative example without compounding any conductive filler.

[0093] Comparative Example 2

[0094] The polyacrylic acid or polyacrylate aqueous binder obtained in Preparation Example 2 was used as a comparative example without compounding any conductive filler.

[0095] Comparative Example 3

[0096] The polyacrylic acid or polyacrylate aqueous binder obtained in Preparation Example 3 was used as a comparative example without compounding any conductive filler.

[0097] Comparative Example 4

[0098] In this comparative example, the difference from Example 1 is that the raw materials for preparing the polyacrylic acid or polyacrylate aqueous binder used in this comparative example do not include a hard monomer.

[0099] The preparation of the polyacrylic acid or polyacrylate aqueous binder comprises the following steps:

[0100] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0101] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 43.75 parts of lauryl acrylate, 37 parts of n-butyl acrylate, 9.25 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0102] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0103] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0104] (2) Add the reaction liquid at the bottom of the kettle to a reactor at 40°C at a speed of 120 rpm. Take out 7 parts of the pre-emulsion as the seed emulsion and add it to the reactor. Heat it to 75°C, add 0.6 parts of the initiator solution, react for 15 minutes, and then drop the remaining pre-emulsion and initiator solution simultaneously. After the addition is complete, keep it at 87°C for 1 hour. After the end of the heat preservation, cool it to 65°C, add 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide, then cool it to below 50°C, adjust the pH to 7.23 with 1.5 parts of 25% aqueous ammonia, and filter the material to obtain a polyacrylic acid or polyacrylate water-based binder.

[0105] Comparative Example 5

[0106] In this comparative example, the difference from Example 1 is that the raw materials for preparing the polyacrylic acid or polyacrylate aqueous binder used in this comparative example do not include a soft monomer.

[0107] The preparation of the polyacrylic acid or polyacrylate aqueous binder comprises the following steps:

[0108] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0109] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then, add 43.75 parts of methyl methacrylate, 37 parts of styrene, 9.25 parts of isobornyl methacrylate, 2 parts of versatate, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0110] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0111] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0112] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.07 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0113] Comparative Example 6

[0114] In this comparative example, the difference from Example 1 is that the raw materials for preparing the polyacrylic acid or polyacrylate aqueous binder used in this comparative example do not include functional monomers.

[0115] The preparation of the polyacrylic acid or polyacrylate aqueous binder comprises the following steps:

[0116] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0117] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water, then add 43.75 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 9.75 parts of isooctyl acrylate, 2 parts of acrylonitrile, 3 parts of lauryl acrylate, and 3.5 parts of lauryl methacrylate in this order until emulsified uniformly;

[0118] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0119] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0120] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.22 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0121] Comparative Example 7

[0122] In this comparative example, the difference from Example 1 is that the amount of hard monomer used in this comparative example is lower, namely 15 parts by weight.

[0123] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0124] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 13 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 41 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0125] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0126] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0127] (2) Add the reaction liquid at the bottom of the kettle to a reactor at 40°C at a speed of 120 rpm. Take out 7 parts of the pre-emulsion as the seed emulsion and add it to the reactor, heat it to 75°C, add 0.6 parts of the initiator solution, react for 15 minutes, and then drop the remaining pre-emulsion and initiator solution at the same time. After the addition is complete, keep it at 87°C for 1 hour. After the insulation is completed, cool it to 65°C, add 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide, then cool it to below 50°C, use 1.5 parts of 25% ammonia water to adjust the pH to 7.38, filter the material, and obtain a polyacrylic acid or polyacrylate water-based binder.

[0128] Comparative Example 8

[0129] In this comparative example, the difference from Example 1 is that the amount of hard monomer used in this comparative example is higher, 80 parts by weight.

[0130] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0131] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water. Then add 78 parts of methyl methacrylate, 3.75 parts of n-butyl acrylate, 9.25 parts of isooctyl acrylate, 2 parts of acrylonitrile, 0.5 parts of acrylamide, 3 parts of acrylic acid, 1 part of methacrylic acid, and 2.5 parts of hydroxyethyl methacrylate in this order and emulsify evenly.

[0132] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0133] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0134] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and initiator solution were then added dropwise. After the addition was complete, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.10 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a polyacrylic acid or polyacrylate water-based binder.

[0135] Comparative Example 9

[0136] In this comparative example, the difference from Example 1 is that the functional dosage in this comparative example is relatively small, namely 0.1 parts by weight.

[0137] (1) Preparation of pre-emulsion, bottom reaction liquid and initiator solution.

[0138] Pre-emulsion: Dissolve 1.06 parts of sodium lauryl sulfate and 0.54 parts of polyoxyethylene octylphenol ether-10 in 40 parts of deionized water, then add 43.75 parts of methyl methacrylate, 37 parts of n-butyl acrylate, 17.15 parts of isooctyl acrylate, 2 parts of acrylonitrile, and 0.1 part of acrylic acid in this order until emulsified uniformly;

[0139] A bottom reaction solution was prepared by dissolving 0.27 parts of sodium lauryl sulfate and 0.13 parts of polyoxyethylene octylphenol ether-10 in 60 parts of deionized water, followed by adding 0.5 parts of sodium bicarbonate to obtain a bottom reaction solution.

[0140] Initiator solution: Add 0.6 parts of ammonium persulfate to 6 parts of deionized water to obtain an initiator aqueous solution.

[0141] (2) The reaction liquid at the bottom of the kettle was added to a reactor at 40°C at a speed of 120 rpm. 7 parts of the pre-emulsion were taken out as seed emulsion and added to the reactor. The temperature was raised to 75°C, 0.6 parts of the initiator solution was added, and the reaction was continued for 15 minutes. The remaining pre-emulsion and the initiator solution were then added dropwise. After the addition was completed, the temperature was kept at 87°C for 1 hour. After the temperature was kept at 65°C, 0.05 parts of bleaching powder and 0.048 parts of tert-butyl peroxide were added, and the temperature was then lowered to below 50°C. The pH was adjusted to 7.93 with 1.5 parts of 25% aqueous ammonia, and the material was filtered to obtain a flexible low-swelling polyacrylic acid or polyacrylate water-based binder.

[0142] Comparative Example 10

[0143] In this comparative example, the difference from Example 1 is that the amount of conductive carbon black added in this comparative example is 15 parts.

[0144] Comparative Example 11

[0145] In this comparative example, the difference from Example 1 is that the added amount of conductive carbon black in this comparative example is 0.05 parts.

[0146] The adhesives obtained in the examples and comparative examples were subjected to performance tests, and the test methods were as follows:

[0147] (1) Take graphite slurry without adding binder, then add binder in an amount of 2% of the solid component of graphite slurry to the solid component of binder, stir evenly to obtain a mixed slurry. Take 30g of the mixed slurry, apply it evenly on copper foil with a coater, bake it at 65℃ for 200s to obtain a pole piece with a thickness of 85μm. Cut the pole piece into 30mm wide strips, stick the strips to the plywood with 3M tape, use a 2kg standard rolling wheel to roll the strips back and forth 3 times to compact them, and then stretch the strips at a stretching speed of 50mm / min to obtain the peel strength;

[0148] (2) The aqueous adhesive prepared in the above examples and comparative examples was dried at 65°C to form a film. 1.5 g of the film sample was cut and immersed in an electrolyte at 65°C for 3 days. The film sample was weighed and the swelling ratio was calculated: swelling ratio = (weight after swelling - weight before swelling) / weight before swelling × 100%;

[0149] (3) Use a plate resistance instrument to test, and each result is the average value of 30 samples;

[0150] The performance test results are shown in Table 1.

[0151] Table 1

[0152] As can be seen from the data in Table 1, the conductive composite water-based adhesive of the present invention has better bonding force and more stable bonding, with a peel strength of 14-16.5 N / m, a swelling rate below 39.64%, and a conductivity above 13.15 S / cm.

[0153] The applicant declares that the present invention uses the above-described embodiments to illustrate the conductive composite water-based adhesive, its preparation method, and its application. However, the present invention is not limited to the above-described embodiments, nor does it necessarily rely on the above-described embodiments for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the present invention, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A conductive composite water-based adhesive, characterized in that: The conductive composite water-based adhesive comprises 90-100 parts of polyacrylic acid or polyacrylate water-based adhesive and 0.1-10 parts of conductive filler in parts by weight.

2. The conductive composite water-based adhesive according to claim 1, characterized in that: The polyacrylic acid or polyacrylate aqueous binder is a polymer obtained by polymerizing a polymerized monomer, wherein the polymerized monomer includes a hard monomer, a soft monomer and a functional monomer; The hard monomer is selected from one or a combination of at least two of methyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl acrylate, isobornyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, acrylonitrile, vinyl acetate or styrene; The soft monomer is selected from one or a combination of at least two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, hexyl methacrylate, tert-butyl carbonate, tetrahydrofurfuryl acrylate, lauric acrylate, lauryl methacrylate, isodecyl acrylate or ethoxyethoxyethoxy acrylate; The functional monomer is selected from one or a combination of at least two of acrylic acid, methacrylic acid, itaconic acid, 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide, ethyl acetoacetate methacrylate, divinylbenzene, aziridine, ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate or a silane coupling agent.

3. The conductive composite water-based adhesive according to claim 1 or 2, characterized in that: The amount of the hard monomer in the polymerizable monomer is 30-70 parts by weight, the amount of the soft monomer is 30-70 parts by weight, and the amount of the functional monomer is 0.5-15 parts by weight; Preferably, the method for preparing the polyacrylic acid or polyacrylate aqueous binder comprises the following steps: (1) preparing a pre-emulsion, a seed emulsion, a kettle bottom reaction liquid and an initiator solution; (2) adding seed emulsion to the reaction liquid at the bottom of the kettle, raising the temperature, adding part of the initiator solution, and reacting; (3) adding the pre-emulsion and the remaining initiator solution to the reaction solution obtained in step (2), reacting to obtain the polyacrylic acid or polyacrylate aqueous binder.

4. The conductive composite water-based adhesive according to claim 3, characterized in that: The pre-emulsion is prepared from hard monomers, soft monomers, functional monomers, emulsifiers and deionized water; Preferably, the pre-emulsion includes 30 to 70 parts by weight of hard monomer, 30 to 70 parts by weight of soft monomer and 0.5 to 15 parts by weight of functional monomer; Preferably, the total weight percentage of the hard monomer, soft monomer and functional monomer in the pre-emulsion is 30-500% of deionized water; Preferably, the amount of the emulsifier in the pre-emulsion is 0.25-5% of the total weight of the hard monomer, the soft monomer and the functional monomer; Preferably, the seed emulsion is a portion of the pre-emulsion taken out from the pre-emulsion; Preferably, the reaction liquid at the bottom of the kettle is prepared by emulsifier, deionized water and buffer; Preferably, the reaction liquid at the bottom of the kettle comprises the following components in parts by weight: 0.1-5 parts of emulsifier, 66-900 parts of deionized water, and 0.25-1 part of buffer.

5. The conductive composite water-based adhesive according to claim 3 or 4, characterized in that: The emulsifiers in the pre-emulsion and the bottom reaction liquid are independently selected from one or a combination of at least two of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene octylphenol ether-10, sodium allyl hydroxypropyl sulfonate, ammonium allyloxy fatty alcohol oxyethylene ether sulfate, disodium nonylphenol succinate polyoxyethylene ether monoester sulfonate, lauryl alcohol ethoxylate, isomeric tridecanol ethoxylate or fatty acid methyl ester ethoxylate; Preferably, the buffer is one or a combination of at least two of sodium bicarbonate, ammonia water, ammonium bicarbonate or sodium hydroxide.

6. The conductive composite water-based adhesive according to any one of claims 3 to 5, characterized in that: The initiator solution comprises an initiator and deionized water; Preferably, the amount of deionized water in the initiator solution is 1 to 20 parts relative to 1 part by weight of the initiator; Preferably, the initiator is selected from inorganic peroxide initiators; Preferably, the initiator is selected from any one or a combination of at least two of potassium persulfate, ammonium persulfate or sodium persulfate; Preferably, the amount of the initiator in the initiator solution is 0.2-0.6% of the total weight percentage of the hard monomer, the soft monomer and the functional monomer.

7. The conductive composite water-based adhesive according to any one of claims 3 to 6, characterized in that: The reaction in step (2) and step (3) is carried out under stirring, and the stirring speed is 100-500r / min; Preferably, before the seed emulsion in step (2), the reaction liquid at the bottom of the kettle is added to a 40-80°C reaction mixture. Should be in the cauldron; Preferably, the temperature in step (2) is increased to 75-85°C; Preferably, the mass of the reaction liquid at the bottom of the kettle in step (2) is 12-40 times that of the seed emulsion; Preferably, the portion of the initiator solution in step (2) is 5-45% of the total weight of the initiator solution; Preferably, the reaction time in step (2) is 10-60 min; Preferably, the weight ratio of the pre-emulsion in step (3) to the bottom reaction liquid in step (2) is 0.15-2.12:1; Preferably, the reaction temperature in step (3) is 80-90°C; Preferably, the reaction time in step (3) is 0.5-2.5h; Preferably, the preparation method further comprises cooling the temperature to 55-70° C. after the reaction in step (3) is completed, adding a residual monomer eliminator, then cooling the temperature to below 50° C., adjusting the pH to 7-8, and filtering the material; Preferably, the residual monomer eliminator is bleaching powder and tert-butyl peroxide; Preferably, the pH is adjusted using one or a combination of at least two of aqueous ammonia, sodium hydroxide, lithium hydroxide, potassium hydroxide or sodium bicarbonate; Preferably, the solid content of the polyacrylic acid or polyacrylate aqueous binder is 10-60%.

8. The conductive composite water-based adhesive according to any one of claims 1 to 7, characterized in that: The conductive filler is selected from any one of conductive carbon black, graphite, carbon nanotubes, graphene, polythiophene, polyacetylene, polydiacetylene, polyfluorene, polyparaphenylene, polyparaphenylene vinylene, polyparaphenylene vinylene, polypyrrole or polyaniline, or a combination of at least two thereof.

9. A lithium-ion battery pole piece, characterized in that: The lithium-ion battery pole piece includes the conductive composite aqueous binder according to any one of claims 1 to 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises a lithium-ion battery pole piece as claimed in any one of claims 1 to 8.

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