Polymer electrolyte type styrene butadiene emulsion binder, one-step preparation method and application thereof

Abstract

The application discloses a polymer electrolyte type butyl benzene emulsion binder, a one-step preparation method and application, and relates to the technical field of binders.The raw materials of the binder include the following components: styrene, difunctional acrylate, polymerized monomer, thiol chain transfer agent, butadiene, initiator and ionized functional monomer.The binder emulsion is prepared by copolymerization of butadiene, styrene, polymerized monomer, ionized functional monomer, difunctional acrylate and thiol chain transfer agent, the emulsion particle size is small, the average particle size is 60-100 nm, the gel content of the dried binder emulsion film is above 90%, and the binder has extremely high dispersibility and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a polymer electrolyte type butylphenyl emulsion binder, a one-step preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in consumer electronics, electric vehicles, aerospace vehicles and energy storage power stations due to their high voltage, high specific energy, stable discharge voltage, superior cycle performance, safety and long service life. A typical lithium ion battery is composed of a positive electrode, a negative electrode, a separator, an electrolyte (usually composed of lithium salt and organic solvent) and a battery shell. Among them, the negative electrode as one of the core components of the battery, its performance directly affects the efficiency and service life of the battery.

[0003] The negative electrode structure of lithium ion battery mainly includes negative electrode active material, conductive agent, metal current collector and binder. Although the amount of binder is not large, it plays a crucial role in the preparation of negative electrode. The main function of the binder is to firmly bond the negative electrode active material and conductive agent particles on the surface of the metal current collector, forming a uniform and integrated structure, ensuring good electron and ion conduction between them, thereby reducing the internal resistance of the electrode and improving the performance and stability of the battery.

[0004] At present, butylphenyl emulsion is a commonly used negative electrode binder. Butylphenyl emulsion has good adhesion and chemical stability, and is often used with sodium carboxymethyl cellulose (CMC) in the preparation process of lithium battery to improve the adhesion effect and the structural stability of the electrode.

[0005] However, the existing technology prepared electrolyte type polymer butylphenyl emulsion has the problems of low gel content and large particle size. Therefore, it is urgent to develop a new type of butylphenyl emulsion binder to solve the above problems. SUMMARY

[0006] The purpose of the present application is to develop a lithium battery negative electrode binder with high gel content and small emulsion particle size.

[0007] The first aspect of the present application is:

[0008] A binder is provided.

[0009] The second aspect of the present application is:

[0010] A preparation method of the binder is provided.

[0011] The third aspect of the present application is:

[0012] The application of the binder.

[0013] The present application also provides a lithium ion battery.

[0014] Specifically, the technical scheme adopted according to the first aspect of the present application is:

[0015] A binder, raw materials of the binder include the following components:

[0016] styrene;

[0017] difunctional acrylate;

[0018] polymerization monomer;

[0019] thiol chain transfer agent;

[0020] butadiene;

[0021] initiator;

[0022] ionized functional monomer;

[0023] emulsifier.

[0024] According to the embodiments of the present application, one of the technical schemes has at least one of the following advantages or beneficial effects:

[0025] The present application uses butadiene, styrene, polymerization monomer, ionized functional monomer, difunctional acrylate and thiol chain transfer agent as active raw materials, and obtains a pre-emulsion in water medium through the dispersion of composite emulsifier and shearing force, and then obtains a binder emulsion through free radical emulsion copolymerization, which has a small emulsion particle size, an average particle size within 60-100 nm, and extremely high dispersibility and stability;

[0026] The addition of difunctional acrylate enables the dry film of the binder emulsion to have excellent crosslinking, and the dry film gel content is above 90%;

[0027] Most of the carboxyl groups in the raw materials can be converted into ionic -COOM and concentrated on the surface of the binder emulsion particles, so that the surface of the binder forms sufficient polarity and ionicity, and when the binder is used to assemble into a pole piece, it can form good compatibility with lithium salt and organic solvent in the electrolyte, and has good compatibility and excellent dispersion stability for negative active filler and conductive agent particles when used with carboxymethyl cellulose, wherein M is one of Li, Na and K, and contains a small amount or trace amount of H;

[0028] The binder emulsion of the present application has a glass transition temperature of the dried film in the range of -10℃-20℃, and is easy to be constructed and formed at normal temperature or slightly lower temperature, and has a wide application range.

[0029] In addition, the binder of the present application contains a phenyl sulfonate with a side chain, which has strong ionicity. The present application uses a proper amount of a difunctional acrylate, so that the polymer emulsion dry film has moderate cross-linking, the dry film gel content is above 90%, and has good skeleton stability, and is not easily damaged by the impact of organic electrolyte.

[0030] According to an embodiment of the present application, the raw material of the binder includes the following components by weight:

[0031] styrene, 100-120 parts;

[0032] difunctional acrylate, 1-4 parts;

[0033] polymerization monomer, 2-6 parts;

[0034] thiol chain transfer agent, 0.1-0.4 parts;

[0035] butadiene, 70-80 parts;

[0036] initiator, 2-4 parts;

[0037] ionized functional monomer, 10-20 parts;

[0038] emulsifier, 2-6 parts.

[0039] The present application uses a proper amount of a difunctional acrylate, so that the polymer emulsion dry film has moderate cross-linking, the dry film gel content is above 90%, and has good skeleton stability, and is not easily damaged by the impact of organic electrolyte.

[0040] According to an embodiment of the present application, the difunctional acrylate includes at least one of 1,2-ethanediol difunctional acrylate, 1,2-propanediol difunctional acrylate, 1,3-propanediol difunctional acrylate, 1,4-butanediol difunctional acrylate, 1,6-hexanediol difunctional acrylate, ethylene glycol difunctional acrylate, ethylene glycol dimethacrylate, propylene glycol difunctional acrylate, propylene glycol dimethacrylate, polyethylene glycol difunctional acrylate, polyethylene glycol dimethacrylate, polypropylene glycol difunctional acrylate, and polypropylene glycol dimethacrylate.

[0041] According to an embodiment of the present application, the polymerization monomer includes at least one of an unsaturated carboxylic acid ester and an unsaturated ene nitrile.

[0042] According to an embodiment of the present application, the unsaturated carboxylic acid ester includes at least one of an acrylate, a methacrylate, a maleic acid diester, and an itaconic acid diester.

[0043] According to an embodiment of the present application, the acrylate includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and C4-C8 alkyl acrylate.

[0044] According to an embodiment of the present application, the methacrylate includes at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, and C4-C8 alkyl methacrylate.

[0045] According to an embodiment of the present application, the maleic acid diester includes at least one of dimethyl maleate, diethyl maleate, dibutyl maleate, and diisooctyl maleate.

[0046] According to an embodiment of the present application, the itaconic acid diester includes at least one of dimethyl itaconate, diethyl itaconate, dibutyl itaconate, and diisooctyl itaconate.

[0047] According to an embodiment of the present application, the unsaturated enecarbonitrile includes at least one of 2-butenenitrile, 3-butenenitrile, and 2-methyl-2-butenenitrile.

[0048] According to an embodiment of the present application, the binder further includes units derived from copolymerization of the unsaturated carboxylic acid ester and the unsaturated enecarbonitrile.

[0049] According to an embodiment of the present application, the mercaptan chain transfer agent includes at least one of tert-dodecyl mercaptan and dodecyl mercaptan.

[0050] According to an embodiment of the present application, the ionized functional monomer includes the unsaturated carboxylic acid and the vinylbenzenesulfonate.

[0051] According to an embodiment of the present application, the unsaturated carboxylic acid includes at least one of maleic acid, fumaric acid, itaconic acid, and methacrylic acid. In the structural formula of the binder, the unit of formula (2) is derived from the unsaturated carboxylic acid, and is obtained by adjusting the pH value of the styrene-butadiene emulsion to be alkaline in step S3.

[0052] According to an embodiment of the present application, the initiator is a mixture containing persulfate and sodium bicarbonate.

[0053] According to an embodiment of the present application, the emulsifier includes at least one of dodecyl sulfate, dodecylbenzenesulfonate, and dodecyldiphenyloxide disulfonate, and at least includes dodecyl sulfate.

[0054] According to an embodiment of the present application, the dodecyl sulfate is used in an amount of 20-80 wt% of the total amount of the emulsifier.

[0055] According to an embodiment of the present application, the sulfate in the dodecyl sulfate is sodium or potassium.

[0056] According to an embodiment of the present application, the sulfonate in the dodecyl benzene sulfonate, dodecyl diphenyl ether disulfonate is sodium or potassium.

[0057] According to an embodiment of the present application, the binder of the present application contains repeating units produced by unsaturated olefin copolymerization, sulfonate ionic repeating units of formula (1), carboxylate ionic repeating units of formula (2) and difunctional acrylic ester micro-crosslinking units of formula (3).

[0058] In formula (1), the structure is at least one of (1)-a, (1)-b and (1)-c:

[0059]

[0060] In formula (2), the structure is at least one of (2)-a, (2)-b and (2)-c:

[0061]

[0062] In formula (3), the structure is:

[0063]

[0064] In formula (3), M1 is one of Li, Na and K;

[0065] In formula (3), M2, M3, M4, M5 and M6 are independently selected from one of Li, Na, K and H, and not all are H;

[0066] In formula (3), R is one of C2-C8 alkyl, ethylene oxide, propylene oxide, polyoxyethylene and polyoxypropylene;

[0067] In formula (3), R1 is CH3 or H.

[0068] According to an embodiment of the present application, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0069] In the binder of the present application, the structures of formula (1) and formula (2) mainly increase the stability, electrolyte properties and ion transport of the emulsion; the structure of formula (3) mainly increases the skeleton stability of the polymer, improves the gel content and increases the organic electrolyte resistance of the polymer.

[0070] Specifically, before neutralization, the ionic sulfonate in formula (1) and the carboxyl in the structural unit of formula (2) are mostly concentrated on the surface of the latex particles (M2, M3, M4, M5 and M6 are H, i.e. carboxyl, before neutralization), and after neutralization with a base, sufficient polarity and ionicity can be formed (most of M2, M3, M4, M5 and M6 are replaced by ions to form carboxylate after neutralization), good compatibility with the components of the electrolyte, lithium salt and organic solvent, and good compatibility and dispersion stability for the negative active filler and conductive agent particles when used with carboxymethyl cellulose. Among them, the unit of formula (1) is derived from the vinyl benzene sulfonate in the ionic functional monomer.

[0071] The structural unit of the binder of formula (3) in the present application is mainly derived from a difunctional acrylate. The structure of formula (3) can make the binder of the present application have a certain crosslinking degree, so that the gel content is increased to more than 90wt%, thereby greatly improving the skeleton stability of the negative material in the organic solvent electrolyte. If a difunctional acrylate is not used as a raw material, the gel content of the obtained emulsion will be lower, below 85wt% or even lower, because the conjugated diene monomer butadiene only partially produces crosslinking (formula (6)) during emulsion polymerization, and a large part still maintains the cis (formula (5) in (5)-a), trans (formula (5) in (5)-b) isomer or terminal double bond structure (formula (5) in (5)-c).

[0072] According to an embodiment of the present application, the repeating unit produced by the copolymerization of unsaturated olefins is a repeating unit of a copolymer produced by the copolymerization of butadiene and styrene initiated by an initiator.

[0073] According to an embodiment of the present application, the repeating unit produced by the copolymerization of unsaturated olefins is a repeating unit of a copolymer produced by the emulsion copolymerization of butadiene and styrene initiated by a persulfate initiator.

[0074] The present application takes butadiene and styrene as main materials, and an emulsion polymerization reaction occurs under the thermal initiation of persulfate initiator. In addition to generating styrene monomer units (formula (4)) and butadiene isomer units (formula (5)), a small amount of crosslinking monomer units (formula (6)) and initiator end groups with ionic properties (formula (7)), the persulfate not only decomposes to generate free radicals to initiate monomer polymerization, but also decomposes to generate a strong acid of bisulfate, thereby making the system particularly acidic. Not only does it cause greater corrosion to metals, but it also leads to the blockage of possible lithium ion channels caused by the introduction of high-priced metal ions into the emulsion, and it also leads to more residues generated by contact with the metal surface. Therefore, although the persulfate initiator can initiate the polymerization reaction of the present application, it also brings new problems, i.e. it can cause more residues to be generated. Based on this, the present application uses a buffer bicarbonate to neutralize the strong acid generated by the persulfate initiator, thereby avoiding the corrosion of the strong acid and solving the problems caused by the persulfate initiator.

[0075]

[0076] According to an embodiment of the present application, in the structural formula of formula (3) of the binder, the unit molecular weight of R is within 600.

[0077] According to an embodiment of the present application, the average particle size of the binder is 60-100 nm.

[0078] According to an embodiment of the present application, the glass transition temperature of the binder is -10℃ to +20℃.

[0079] According to an embodiment of the present application, in the structural formula of formula (3) of the binder, the unit molecular weight of R is within 600.

[0080] According to an embodiment of the present application, the repeating units generated by the copolymerization of unsaturated olefins include structures represented by formula (4), formula (5), formula (6) and formula (7);

[0081] wherein formula (4) is:

[0082]

[0083] wherein the structural formula of formula (5) is one of (5)-a, (5)-b and (5)-c:

[0084]

[0085] wherein the structural formula of formula (6) is one of (6)-a, (6)-b and (6)-c:

[0086]

[0087] wherein formula (7) is:

[0088]

[0089] According to an embodiment of the present application, the mass ratio of the sulfonate ionic repeating unit of formula (1) to the difunctional acrylate micro-crosslinking unit of formula (3) is 3-13:0.2-1.

[0090] According to an embodiment of the present application, the binder further comprises 0-10wt% of units obtained by copolymerization of unsaturated carboxylate.

[0091] Specifically, the technical solution adopted according to the second aspect of the present application is:

[0092] A method for preparing the binder, comprising the following steps:

[0093] S1 mixing styrene, difunctional acrylate, polymerization monomer, thiol chain transfer agent, emulsifier and water to obtain a pre-emulsion;

[0094] S2 mixing the pre-emulsion, butadiene, initiator and ionized functional monomer in a high-pressure reaction device, and performing heating reaction to obtain a butadiene-styrene emulsion with partial acidity;

[0095] S3 adjusting the pH value of the butadiene-styrene emulsion with partial acidity to be alkaline, and performing heating and pressure reduction treatment to obtain the binder.

[0096] According to an embodiment of the present application, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0097] The method of the present application simplifies the entire process flow and saves time and resources by directly using emulsion polymerization without the need to prepare a seed emulsion. Secondly, using a high-pressure reaction device for heating reaction can efficiently initiate the polymerization reaction of butadiene and other functional monomers, thereby improving the efficiency and yield of the reaction. Adjusting the pH value of the butadiene-styrene emulsion with partial acidity to be alkaline and performing heating and pressure reduction treatment helps to accurately control the properties and structure of the binder emulsion, exhibit ionicity, and ensure the stability and applicability of the product. In addition, the use of various functional monomers such as unsaturated carboxylate and difunctional acrylate enables the binder to have diversified chemical properties and physical properties, enhancing its application flexibility and effectiveness. Overall, this method not only improves production efficiency and product quality, but also helps to protect the environment, meeting the requirements of modern chemical production.

[0098] According to an embodiment of the present application, in step S2, the heating reaction is performed at a temperature of 70-85°C under a pressure of 9 kg or less.

[0099] According to an embodiment of the present application, in step S2, the heating reaction is a two-step heating reaction, the first step is at a temperature of 70-80°C, and the second step is at a temperature of 80-85°C.

[0100] According to an embodiment of the present application, the solid content of the butyl-styrene emulsion with a partial acidity obtained in step S2 is 35-45wt%, and the medium is deionized water.

[0101] According to an embodiment of the present application, in step S3, the pH of the butyl-styrene emulsion after being adjusted to be alkaline is 9-10.

[0102] According to an embodiment of the present application, in step S3, the method further comprises the following step: adjusting the pH of the butyl-styrene emulsion with a partial acidity to be alkaline by adding an alkali solution, wherein the alkali solution is LiOH·H2O, NaOH or KOH.

[0103] Another aspect of the present application also provides a lithium battery negative electrode comprising the binder as described in the above embodiment of the first aspect. Since the application adopts all the technical solutions of the above binder, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0104] Other features and advantages of the present application will be set forth in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. DETAILED DESCRIPTION

[0105] In the description of the present application, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0106] The words "preferably", "more preferably" and the like in the present application refer to embodiments of the present application that can provide certain beneficial effects in certain circumstances. However, other embodiments can also be preferred in the same or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not usable, nor is it intended to exclude other embodiments from the scope of the present application.

[0107] When a range of values is disclosed, the disclosure is to be construed to include each and every value and sub-range within the range. Further, where a range of values is provided, it is to be understood that each intervening value, to the minimum and maximum value of that range, is also contemplated, unless the context clearly indicates otherwise. Further, it shall be understood that every group of materials or compounds, and / or methods, described herein, is intended to be a genus of like materials or compounds, and / or methods, and that individual members of the genus can be specifically disclosed herein.

[0108] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0109] The reagents, methods and devices used in the present application are conventional reagents, methods and devices in the technical field, unless otherwise specified.

[0110] Example 1

[0111] The adhesive of Example 1 contains units of formula (1)-(3):

[0112]

[0113] The raw reagents were prepared according to the following method:

[0114] An initiator aqueous solution 5 was prepared by dissolving 2.0 g of potassium persulfate in 87.6 g of deionized water, and then adding 0.4 g of sodium bicarbonate for neutralization to obtain 90 g of an initiator composite aqueous solution 5, which was introduced into a water-phase initiator storage tank in a high-pressure reaction kettle treated by nitrogen purging, oxygen removal and pressure reduction, and was ready for use;

[0115] An ionic functional monomer aqueous solution 5 was prepared by dissolving 3.0 g of sodium 4-vinylbenzenesulfonate, 10.0 g of maleic acid and 5.0 g of methacrylic acid in 82.0 g of deionized water, which was introduced into the 4th storage tank in a high-pressure reaction kettle treated by nitrogen purging, oxygen removal and pressure reduction, and was ready for use;

[0116] 70.0 g of butadiene was introduced into a butadiene storage tank in a 1-liter stainless steel high-pressure reaction kettle treated by nitrogen purging, oxygen removal and pressure reduction, and was ready for use.

[0117] A method for preparing an adhesive, comprising the following steps:

[0118] S1Styrene 106.4 g was mixed with tripropyleneglycol dipropylene acrylate 1.8 g, hydroxyethyl methacrylate 1.8 g, dibutyl maleate 2.0 g and tert-dodecanethiol 0.2 g, and then the mixture was pre-emulsified by dropping the mixture into a mixture containing sodium dodecyl sulfate 1.0 g, sodium dodecylbenzenesulfonate 1.0 g, sodium dodecyl diphenyloxide disulfonate 1.0 g and deionized water 114.4 g at room temperature with high speed stirring at 800 rpm to obtain a monomer pre-emulsion 226.6 g without butadiene, which was introduced into a mixed monomer tank in a high-pressure reactor which had been treated with nitrogen, deoxygenation and reduced pressure, and the rotation speed was kept at 100 rpm;

[0119] S2The 10 wt% monomer pre-emulsion without butadiene was introduced into the high-pressure reactor, and then the high-pressure reactor was heated to 80°C, the stirring speed of the reactor was 200 rpm, and the butadiene, initiator complex aqueous solution 5, ionized functional monomer aqueous solution 5 and the remaining monomer pre-emulsion were added dropwise, the dropping and reaction were carried out under a pressure of less than 9 kg, the temperature of the reaction liquid was kept at 80°C, the dropping time was 1 h, after the dropping was completed, the reaction was kept at 80°C for 2 h, and then the reaction was kept at 85°C for 1 h, after cooling, the emulsion was filtered through a 200 mesh filter screen to obtain 486 g of butadiene-styrene emulsion with partial acidity, and the dry weight of the filter residue was 0.58 g. Sampling was performed, and the pH value of the emulsion was measured to be 2, and the solid content was 41.0 wt%.

[0120] S3The butadiene-styrene emulsion with partial acidity was neutralized by adding 10 wt% alkali (LiOH-H2O) solution dropwise for 10 minutes, the pH value was neutralized to 9, the total amount of alkali was 91.0 g, which was 93.9 wt% of the theoretical amount, and finally heated to 70°C for reduced pressure to remove unreacted volatile monomers, and after cooling, the emulsion was filtered through a 200 mesh filter screen to obtain 550 g of the above-mentioned adhesive.

[0121] The average particle size of the above-mentioned adhesive was 76 nm, the solid content was 36.4 wt%, and the dry film glass transition temperature was 8.1°C.

[0122] Example 2

[0123] The adhesive of Example 2 contains units of formula (1)-(3):

[0124]

[0125] The raw reagents were prepared as follows:

[0126] The initiator potassium persulfate 2.0 g was dissolved in 87.6 g of deionized water to prepare an initiator aqueous solution 5, and then sodium bicarbonate 0.4 g was added for neutralization to obtain 90 g of initiator complex aqueous solution 5, which was introduced into a water phase initiator tank in a high-pressure reactor which had been treated with nitrogen, deoxygenation and reduced pressure, and was ready for use;

[0127] Preparation of 100 g of an aqueous solution of ionized functional monomers 5 by dissolving 3.0 g of sodium 4-vinylbenzenesulfonate, 10.0 g of maleic acid, and 5.0 g of methacrylic acid in 82.0 g of deionized water, and introducing the solution into the fourth tank of the high-pressure reactor that has been treated with nitrogen, deoxygenated, and reduced in pressure, and kept ready for use;

[0128] Preparation of 70.0 g of butadiene by introducing butadiene into the butadiene tank of a 1-liter stainless steel high-pressure reactor that has been treated with nitrogen, deoxygenated, and reduced in pressure, and kept ready for use.

[0129] A method for preparing a binder, comprising the following steps:

[0130] The preparation method of Example 2 is different from the preparation method of Example 1 in that the emulsifier in step S1 is different. In Example 1, the emulsifier is a mixture containing 1.0 g of sodium dodecyl sulfate, 1.0 g of sodium dodecyl benzene sulfonate, 1.0 g of sodium dodecyl diphenyl ether disulfonate, and 114.4 g of deionized water; in Example 2, the emulsifier is a mixture containing 2.4 g of sodium dodecyl sulfate, 0.6 g of sodium dodecyl benzene sulfonate, and 114.4 g of deionized water.

[0131] S1: mixing styrene 106.4 g with tripropylene glycol diacrylate 1.8 g, hydroxyethyl methacrylate 1.8 g, dibutyl maleate 2.0 g, and tert-dodecanethiol 0.2 g, and then adding the mixture dropwise into a mixture of sodium dodecyl sulfate 2.4 g, sodium dodecyl benzene sulfonate 0.6 g, and deionized water 114.4 g at room temperature under high-speed stirring at 800 rpm to perform pre-emulsification, thereby obtaining 226.6 g of a monomer pre-emulsion solution without butadiene, which is introduced into the mixed monomer tank of the high-pressure reactor that has been treated with nitrogen, deoxygenated, and reduced in pressure, and kept at a rotation speed of 100 rpm;

[0132] S2: introducing 10 wt% of the monomer pre-emulsion solution without butadiene into the high-pressure reactor, and then heating the high-pressure reactor to 80°C, while the stirring speed of the reactor is 200 rpm, and dropwise adding butadiene, initiator complex aqueous solution 5, ionized functional monomer aqueous solution 5, and the remaining monomer pre-emulsion solution, and dropwise adding and reacting under a pressure of 9 kg or less, while keeping the temperature of the reaction solution at 80°C, and the dropwise adding time is 1 h, and after the dropwise adding is completed, the reaction is kept at 80°C for 2 hours, and then kept at 85°C for 1 hour, and after cooling, the reaction solution is filtered through a 200-mesh filter screen, thereby obtaining 485.5 g of a butadiene-styrene emulsion with a slight acidity, and the dry weight of the filter residue is 0.62 g. Sampling is performed, and the pH value of the emulsion is measured to be 2, and the solid content is 40.8 wt%;

[0133] S3: 10wt% alkali (LiOH-H2O) solution was added dropwise into the butyl-styrene emulsion with acidic bias for neutralization for 10 minutes, neutralized to pH 9, total alkali amount was 90.8g, 93.7wt% of the theoretical amount, finally heated to 70°C for vacuum, to remove unreacted volatile monomers, cooled, filtered through 200 mesh screen, to obtain 549.3g of the above binder.

[0134] The above binder has an average particle size of 98nm, solid content of 36.3wt%, and dry film glass transition temperature of 8.2°C.

[0135] Example 3

[0136] The binder of Example 3 contains units of formula (1)-(3):

[0137]

[0138] The raw reagents were prepared as follows:

[0139] The initiator potassium persulfate 2.0g was dissolved in 87.6g deionized water to prepare initiator aqueous solution 5, then 0.4g sodium bicarbonate was added for neutralization, to obtain 90g initiator composite aqueous solution 5, which was introduced into the water phase initiator storage tank in the high pressure reactor which was treated by nitrogen purging, oxygen removal and vacuum, for standby;

[0140] 3.0g of sodium 4-vinylbenzenesulfonate and 15.0g of itaconic acid were dissolved in 82.0g deionized water to prepare 100g of ionized functional monomer aqueous solution 5, which was introduced into the 4th storage tank in the high pressure reactor which was treated by nitrogen purging, oxygen removal and vacuum, for standby;

[0141] 70.0g of butadiene was introduced into the butadiene storage tank in the 1 liter stainless steel high pressure reactor which was treated by nitrogen purging, oxygen removal and vacuum, for standby.

[0142] A method for preparing a binder, comprising the following steps:

[0143] The preparation method of Example 3 is different from the preparation method of Example 1 in that in step S1, the emulsifier is different. In Example 1, the emulsifier is a mixture containing 1.0g of sodium dodecyl sulfate, 1.0g of sodium dodecyl benzene sulfonate, 1.0g of sodium dodecyl diphenyl ether disulfonate, and 114.4g of deionized water; in Example 3, the emulsifier is a mixture containing 0.5g of sodium dodecyl sulfate, 1.25g of sodium dodecyl benzene sulfonate, 1.25g of sodium dodecyl diphenyl ether disulfonate, and 114.4g of deionized water.

[0144] The preparation method of Example 3 is different from the preparation method of Example 1 in that the components of the ionized functional monomer aqueous solution are different. The ionized functional monomer aqueous solution of Example 1 includes 3.0 g of sodium 4-vinylbenzenesulfonate, 10.0 g of maleic acid, and 5.0 g of methacrylic acid, and the ionized functional monomer aqueous solution of Example 3 includes 3.0 g of sodium 4-vinylbenzenesulfonate, 15.0 g of itaconic acid.

[0145] S1Styrene 106.4 g was mixed with tripropyleneglycol diacrylate 1.8 g, hydroxyethyl methacrylate 1.8 g, maleic acid dibutyl ester 2.0 g and tert-dodecanethiol 0.2 g, and then the mixture was added dropwise into a mixture solution containing sodium dodecyl sulfate 0.5 g, sodium dodecylbenzenesulfonate 1.25 g, sodium dodecyl diphenyloxide disulfonate 1.25 g and deionized water 114.4 g at room temperature under high-speed stirring at 800 rpm to perform pre-emulsification, thereby obtaining 226.6 g of monomer pre-emulsion without butadiene. The monomer pre-emulsion was introduced into a mixed monomer storage tank in a high-pressure reactor which was treated by nitrogen purging, oxygen removal and pressure reduction, and the rotation speed was maintained at 100 rpm;

[0146] S2The 10 wt% monomer pre-emulsion without butadiene was introduced into the high-pressure reactor, and then the high-pressure reactor was heated to 80°C. The rotation speed of the reactor was 200 rpm, and butadiene, initiator compound aqueous solution 5, ionized functional monomer aqueous solution 5 and the remaining monomer pre-emulsion were added dropwise under a pressure of less than 9 kg. The temperature of the reaction solution was maintained at 80°C, the dropping time was 1 h, and after the dropping was completed, the reaction was maintained at 80°C for 2 h and then at 85°C for 1 h. After cooling, the reaction solution was filtered through a 200-mesh filter, thereby obtaining 487.5 g of butadiene-styrene emulsion with partial acidity, and the dry weight of the filter residue was 0.35 g. The pH value of the emulsion was measured to be 2, and the solid content was 41.3 wt%.

[0147] S3The butadiene-styrene emulsion with partial acidity was neutralized by adding 10 wt% alkali (LiOH·H2O) solution dropwise for 10 min, and the pH value was adjusted to 9. The total amount of alkali was 92.0 g, which was 94.9 wt% of the theoretical amount. Finally, the unreacted volatile monomers were removed by heating to 70°C under reduced pressure. After cooling, the reaction solution was filtered through a 200-mesh filter, thereby obtaining 555 g of the above-mentioned adhesive.

[0148] The average particle size of the above-mentioned adhesive was 69 nm, the solid content was 36.2 wt%, and the dry film glass transition temperature was 5.2°C.

[0149] Example 4

[0150] The adhesive of Example 4 contains units of formula (1)-(3):

[0151]

[0152] The raw reagent was prepared by the following method:

[0153] An initiator aqueous solution 5 was prepared by dissolving 2.0 g of potassium persulfate in 87.6 g of deionized water, and then adding 0.4 g of sodium bicarbonate for neutralization to obtain 90 g of the initiator composite aqueous solution 5, which was introduced into the aqueous phase initiator storage tank in the high-pressure reaction kettle treated by nitrogen purging, oxygen removal and reduced pressure, and was ready for use;

[0154] An ionized functional monomer aqueous solution 5 was prepared by dissolving 3.0 g of sodium 4-vinylbenzenesulfonate and 15.0 g of itaconic acid in 82.0 g of deionized water, which was introduced into the fourth storage tank in the high-pressure reaction kettle treated by nitrogen purging, oxygen removal and reduced pressure, and was ready for use;

[0155] 70.0 g of butadiene was introduced into the butadiene storage tank in the 1-liter stainless steel high-pressure reaction kettle treated by nitrogen purging, oxygen removal and reduced pressure, and was ready for use.

[0156] A method for preparing a binder, comprising the following steps:

[0157] Example 4 differs from Example 3 in that in step S1, the emulsifiers are different. The emulsifiers of Example 3 include 0.5 g of sodium dodecyl sulfate, 1.25 g of sodium dodecyl benzene sulfonate, and 1.25 g of sodium dodecyl diphenyl ether disulfonate. The emulsifiers of Example 4 include 1.0 g of sodium dodecyl sulfate, 2.5 g of sodium dodecyl benzene sulfonate, and 2.5 g of sodium dodecyl diphenyl ether disulfonate.

[0158] S1: 106.4 g of styrene was mixed with 1.8 g of tripropylene glycol diacrylate, 1.8 g of hydroxyethyl methacrylate, 2.0 g of dibutyl maleate, and 0.2 g of tert-dodecanethiol, and then the mixture was added dropwise into a mixture containing 1.0 g of sodium dodecyl sulfate, 2.5 g of sodium dodecyl benzene sulfonate, 2.5 g of sodium dodecyl diphenyl ether disulfonate, and 114.4 g of deionized water under high-speed stirring at room temperature at 800 rpm for pre-emulsification to obtain 229.6 g of a monomer pre-emulsion without butadiene, which was introduced into the mixed monomer storage tank in the high-pressure reaction kettle treated by nitrogen purging, oxygen removal and reduced pressure, and the rotation speed was maintained at 100 rpm;

[0159] S2 10 wt% of the monomer pre-emulsion without butadiene was introduced into the high-pressure reactor, which was then heated to 80°C at a stirring speed of 200 rpm. Butadiene, initiator complex aqueous solution 5, ionized functional monomer aqueous solution 5 and the remaining monomer pre-emulsion were added dropwise under a pressure of 9 kg. The reaction was carried out at a temperature of 80°C for 1 h. After the addition was completed, the reaction was carried out at 80°C for 2 h and at 85°C for 1 h. After cooling, the emulsion was filtered through a 200-mesh screen to obtain 489.5 g of butadiene-styrene emulsion with a pH of 2 and a solid content of 41.9 wt%.

[0160] S3 10 wt% of an alkali (LiOH-H2O) solution was added dropwise to the butadiene-styrene emulsion with a pH of 2 to neutralize it for 10 min. The total amount of alkali added was 91.6 g, which was 94.5 wt% of the theoretical amount. Finally, the mixture was heated to 70°C to remove unreacted volatile monomers under reduced pressure. After cooling, the mixture was filtered through a 200-mesh screen to obtain 556 g of the above-mentioned adhesive.

[0161] The average particle size of the above-mentioned adhesive was 62 nm, the solid content was 36.6 wt%, and the dry film glass transition temperature was 5.5°C.

[0162] Example 5

[0163] The adhesive of Example 5 contained units of formula (1)-(3):

[0164]

[0165] The raw reagents were prepared as follows:

[0166] The initiator aqueous solution 5 was prepared by dissolving 2.0 g of potassium persulfate in 87.6 g of deionized water. Then, 0.4 g of sodium bicarbonate was added to neutralize the solution, and 90 g of initiator complex aqueous solution 5 was obtained. The solution was introduced into the water-phase initiator storage tank of the high-pressure reactor, which had been treated with nitrogen, deoxygenation and reduced pressure, and was ready for use.

[0167] The ionized functional monomer aqueous solution 5 was prepared by dissolving 5.0 g of sodium 4-vinylbenzenesulfonate and 5.0 g of maleic acid in 90.0 g of deionized water to obtain 100 g of the solution. The solution was introduced into the fourth storage tank of the high-pressure reactor, which had been treated with nitrogen, deoxygenation and reduced pressure, and was ready for use.

[0168] The butadiene was introduced into the butadiene storage tank of the 1-liter stainless steel high-pressure reactor, which had been treated with nitrogen, deoxygenation and reduced pressure, and was ready for use.

[0169] A method for preparing an adhesive, comprising the following steps:

[0170] S1Styrene 106.4g was mixed with triethylene glycol dimethacrylate 1.8g, hydroxyethyl methacrylate 1.8g, dibutyl maleate 2.0g and tert-dodecanethiol 0.2g, and then the mixture was pre-emulsified by dropping into a mixture containing sodium dodecyl sulfate 0.5g, sodium dodecyl diphenyl ether disulfate 1.5g and deionized water 115.4g under high-speed stirring at room temperature and 800 rpm to obtain a monomer pre-emulsion 226.6g without butadiene, which was introduced into a mixed monomer tank in a high-pressure reactor treated by nitrogen, oxygen removal and reduced pressure, and the rotation speed was kept at 100 rpm;

[0171] S2The monomer pre-emulsion 10wt% without butadiene was introduced into the high-pressure reactor, and then the high-pressure reactor was heated to 75℃, the stirring speed of the reactor was 200 rpm, and butadiene, initiator complex aqueous solution 5, ionized functional monomer aqueous solution 5 and the remaining monomer pre-emulsion were added dropwise, the dropping and reaction were carried out under a pressure of 9 kg, the temperature of the reaction liquid was kept at 75℃, the dropping time was 1 h, after the dropping was completed, the reaction was kept at 80℃ for 2 hours, and then the reaction was kept at 85℃ for 1 hour, after cooling, the emulsion was filtered through a 200 mesh filter screen to obtain a butadiene-styrene emulsion 485g with partial acidity, and the dry weight of the filter residue was 0.72g. Sampling was performed, and the pH value of the emulsion was measured to be 3, and the solid content was 40.9wt%.

[0172] S3The butadiene-styrene emulsion with partial acidity was neutralized by adding 10wt% alkali (LiOH·H2O) solution dropwise for 10 minutes, the pH value was neutralized to 9, the total amount of alkali was 33.5g, which was 92.5wt% of the theoretical amount, and finally heated to 80℃ for reduced pressure to remove unreacted volatile monomers, and after cooling, the emulsion was filtered through a 200 mesh filter screen to obtain 503g of the above binder.

[0173] The average particle size of the above binder was 74nm, the solid content was 39.8wt%, and the dry film glass transition temperature was 1.3℃.

[0174] As can be seen from the embodiments of the present application, the butadiene-styrene emulsion with high dispersion and stability of 60-100nm can be obtained by using suitable emulsifiers and formulation processes.

[0175] Comparative Example 1

[0176] The raw reagents were prepared by the following method:

[0177] The initiator potassium persulfate 0.95g was dissolved in deionized water 48.89g to prepare an initiator aqueous solution 1, and then sodium bicarbonate 0.16g was added for neutralization to obtain 50g of initiator complex aqueous solution 1, which was ready for use;

[0178] Dissolve 0.5 g of ionized functional monomer sodium 4-vinylbenzenesulfonate, 2.0 g of methacrylic acid in 37.5 g of deionized water to obtain 40 g of ionized functional monomer aqueous solution 1;

[0179] Put 65.0 g of butadiene into one of the four pressure-resistant dropping reservoirs of a 1-liter stainless steel high-pressure reaction kettle treated with nitrogen, oxygen removal and reduced pressure, and reserve it;

[0180] In a normal pressure device, weigh 100.3 g of styrene, 2.0 g of triethylene glycol dimethacrylate, 1.8 g of hydroxyethyl methacrylate, 2.0 g of dibutyl itaconate, 6.9 g of methacrylic acid and 0.2 g of tert-dodecanethiol to obtain 113.2 g of monomer mixture, and place it in the monomer mixing reservoir of the high-pressure reaction kettle, and reserve it;

[0181] Dissolve 1.9 g of initiator potassium persulfate in 97.9 g of deionized water to prepare 100 g of initiator composite aqueous solution 2, and place it in the aqueous phase initiator reservoir of the high-pressure reaction kettle, and reserve it;

[0182] A method for preparing a binder, comprising the following steps:

[0183] S1: Mix 87.5 g of styrene with 10 g of dibutyl maleate uniformly, then add it dropwise into a mixture containing 1.0 g of emulsifier sodium dodecyl sulfate, 1.0 g of sodium dodecyl benzene sulfonate, 1.0 g of sodium dodecyl diphenyl ether disulfonate and 134.84 g of deionized water at room temperature under high-speed stirring at 660 rpm to perform pre-emulsification, and obtain 235.34 g of monomer pre-emulsion;

[0184] S2: Take 45 g of the monomer pre-emulsion as the base material into the reaction kettle, add 10 g of the prepared initiator composite aqueous solution 1, stir in the reaction kettle at 200 rpm, and raise the oil bath temperature to 80℃. When the reaction solution appears blue light, start dropping the remaining monomer pre-emulsion, the remaining initiator aqueous solution 1 and the ionized functional monomer aqueous solution 1, and keep the reaction solution temperature at 75-85℃. The dropping time is 0.8 h. After dropping, keep the oil bath temperature at 90℃ for 2 hours, cool, pass through a 200-mesh filter screen to obtain 324.0 g of poly-styrene seed emulsion with acidic properties, and the dry weight of the filter residue after filtration is 0.17 g;

[0185] S3 Take 66.6 g of poly-styrene seed emulsion, 0.8 g of sodium dodecyl sulfate, 0.8 g of sodium dodecyl benzene sulfonate, 0.8 g of sodium dodecyl diphenyl ether disulfonate and 138.0 g of deionized water, mix them uniformly to obtain a base mixture, put it into a high-pressure reaction kettle, then heat the high-pressure reaction kettle to 80℃, the stirring speed of the reaction kettle is 150 rpm, while adding dropwise butadiene, monomer mixture, initiator compound aqueous solution 2, add and react under a pressure of 9 kg or less, keep the temperature of the reaction liquid at 80℃, the dropwise adding time is 1 h, after the dropwise adding is completed, heat to 80℃ and keep for 3 hours, cool, pass through a filter screen with a mesh size of 200 to obtain 470 g of butadiene-styrene emulsion, the total dry weight of the filter residue after filtration is 2.5 g. Take a sample and measure the solid content of 40.8 wt%, the pH value is 1;

[0186] S4 Take 47 g of the obtained butadiene-styrene emulsion, neutralize it with 10 wt% alkali solution of LiOH·H2O for 10 minutes to pH = 9 to obtain an adhesive, 1.7 g of alkali solution is needed for neutralization, which is 50.4% of the theoretical amount of alkali solution needed for neutralizing all carboxyl groups.

[0187] As can be seen from the comparative example 1, in the process of using sodium bicarbonate as a buffer in the initiator and not using sodium bicarbonate, the former can obtain less residue (0.17 g) when preparing the polystyrene seed emulsion, while the latter can obtain more residue (2.5 g) when preparing the butadiene-styrene emulsion without using sodium bicarbonate as a buffer. In the examples 1-5 of the present application, the compound of sodium bicarbonate and persulfate is used as a buffer, which can obtain less residue when preparing the butadiene-styrene emulsion, and with the increase of the amount of emulsifier, the residue amount shows a decreasing trend, and the metal reaction kettle is not corroded in the high-temperature and high-pressure reaction kettle.

[0188] Performance test:

[0189] The gel content of the adhesive obtained in example 1 is tested, and the test method is as follows: pour 15 g of emulsion on a circular flat surface dish with a diameter of 10 cm, then put it into a 40℃ air drying oven with a relative humidity of 40% for drying for 48 hours, take out the dry film, cut it into a square film with a size of 1 cm*1 cm, accurately weigh about 1 g (recorded as m0), put it into a 500 ml flat bottom glass bottle containing 300 g of dry tetrahydrofuran solvent, seal, place, after 24 hours, filter, the filter residue is naturally dried at room temperature for 24 hours, then put it into a 40℃ air drying oven with a relative humidity of 40% for drying for 24 hours, accurately weigh, record as m1, calculate the gel content according to the following formula:

[0190] Gel content (wt%): (m0-m1) x 100 / m0.

[0191] The gelling contents of the dry films of the adhesives obtained in Examples 1-5 in tetrahydrofuran (THF) were 92.8, 93.5, 93.1, 93.9 and 91.2 wt%, respectively.

[0192] The properties of the adhesives obtained in Example 1 and Comparative Example 1 were tested, and the test results are shown in Table 1.

[0193] Table 1

[0194]

[0195]

[0196] As can be seen from Table 1, the emulsion prepared by the direct seedless copolymerization of butadiene, styrene, vinylbenzenesulfonate, a specific unsaturated carboxylic acid, difunctional acrylate and other monomers using a suitable process in the present application has certain acidity (pH value is 2-3, while the pH value of Comparative Example 1 is 1, which is more serious) before neutralization, but does not corrode metal during the reaction, has less slag (while there is much slag in the preparation of butadiene-styrene emulsion in Comparative Example 1), and most of the hydrophilic carboxyl groups are distributed on the surface of the latex particles and can be quickly neutralized to form ions. After neutralization, the emulsion has small particle size, the average particle size is within 60-100 nm, has good dispersion and stability, most of the carboxyl groups are converted into ionic -COOM, the neutralization degree is more than 90% of the theoretical amount, and the emulsion also contains side chain phenyl sulfonate, which has strong ionicity.

[0197] The present application uses an appropriate amount of difunctional acrylate, so that the polymer emulsion dry film has moderate crosslinking, the dry film gelling content is 92.8 wt%, and the dry film has good skeleton stability and is not easily damaged by organic electrolyte.

[0198] In addition, the glass transition temperature of the emulsion dry film of the present application is 1-10°C, the film is easy to be applied and formed at slightly low temperature, and has a wide application range.

[0199] The above are only examples of the present application, and do not limit the patent scope of the present application, and any equivalent transformation or direct or indirect application in related technical fields using the content of the present application are also included in the patent protection scope of the present application.

Claims

1. An adhesive, characterized in that: The raw materials of the adhesive include the following components in parts by weight: Styrene, 100-120 parts; Difunctional acrylate, 1-4 parts; Polymer monomer, 2-6 parts; Thiol chain transfer agent, 0.1-0.4 parts; Butadiene, 70-80 parts; Initiator, 2-4 parts; Ionized functional monomer, 10-20 parts; Emulsifier, 2-6 parts; The ionized functional monomers include unsaturated carboxylic acids and vinylbenzene sulfonates; The emulsifiers are dodecyl sulfate, dodecylbenzene sulfonate, and dodecyl diphenyl ether disulfonate; The amount of dodecyl sulfate used is 20-80 wt% of the total emulsifier. The unsaturated carboxylic acid is at least one of maleic acid, fumaric acid, itaconic acid, and methacrylic acid; The difunctional acrylates include at least one of 1,2-ethylene glycol diacrylate, 1,2-propanediol diacrylate, 1,3-propanediol dipropionate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, and polypropylene glycol dimethacrylate.

2. The adhesive according to claim 1, characterized in that: The polymer monomer includes at least one of unsaturated carboxylic acid esters and unsaturated olefinic acrylonitriles.

3. The adhesive according to claim 1, characterized in that: The initiator is a mixture of persulfate and sodium bicarbonate.

4. A method for preparing an adhesive as described in any one of claims 1 to 3, characterized in that: Includes the following steps: S1 mixes styrene, difunctional acrylate, polymeric monomer, thiol chain transfer agent, emulsifier and water to obtain a pre-emulsion; S2 The pre-emulsion, butadiene, initiator, and ionized functional monomer are mixed in a high-pressure reactor and heated to obtain a slightly acidic styrene-butadiene emulsion. S3 The pH of the slightly acidic styrene-butadiene emulsion is adjusted to alkaline, and then subjected to heating and depressurization treatment to obtain the binder.

5. The method according to claim 4, characterized in that: In step S2, the heating reaction is carried out at a pressure of less than 9 kg and a temperature of 70-85°C.

6. A lithium battery negative electrode, characterized in that: Includes an adhesive as described in any one of claims 1 to 3.

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