Water-based adhesive, method for manufacturing the same, and applications

Abstract

This specification discloses an aqueous adhesive and its manufacturing method and application. The aqueous adhesive is a copolymer formed by reacting a polymer metal salt with a polymerizable monomer, the polymerizable monomer includes a combination of an acrylate monomer and an olefin monomer, and the polymer metal salt is any one or a combination of at least two selected from a metal phosphate polymer, a metal carboxylate polymer, a metal sulfonate polymer, or a metal bissulfonyl imide polymer. The present application includes a specific repeating structural unit in the copolymer segment formed by designing structural units such as a polymer metal salt and a polymerizable monomer and synergizing them, thereby providing the aqueous adhesive with suitable swelling properties, excellent adhesive performance, and lithium ion conductivity, and at the same time, providing excellent adhesive strength, adhesive stability, and electrochemical performance, and significantly improving the cycle performance and rate performance of a lithium ion battery containing the same.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of lithium-ion battery materials, such as aqueous adhesives and their manufacturing methods and applications.

Background Art

[0002] In recent years, in order to meet the demand for electrified equipment, especially to adapt to the further development of the mobile phone and electric vehicle industries, improving the performance of lithium-ion batteries has also faced a major challenge. Currently, the market's needs for the energy density of lithium-ion batteries are not only higher, but the functional requirements for rapid charging are also becoming increasingly important. The adhesive is one of the main components of the battery electrode sheet and is used to connect the active material, the conductive agent, and the electrode current collector to ensure the overall connection between them. In the charge and discharge process, the adhesive effectively maintains the integrity of the electrode structure, ensures that the electrode material repeatedly inserts and removes lithium, and also plays an important role in maintaining the cycle performance. The adhesive has an important impact on the electrical performance of the electrode sheet and the battery, and high-performance lithium-ion batteries require high-performance adhesives that match them.

[0003] Polyvinylidene fluoride (PVDF) is currently the most common oily adhesive in lithium-ion batteries. It has excellent redox ability and stability, but it is necessary to use N-methylpyrrolidone (NMP) as a solvent to achieve good dispersion. The evaporation temperature of NMP is high, it is expensive, it is harmful to human health, there is a risk of environmental pollution, and furthermore, PVDF is prone to hydrolysis, so in the manufacturing process of the electrode sheet, it is necessary to strictly control the environmental humidity, which increases the manufacturing cost of the battery, and PVDF swells in the electrolyte, affecting the reliability and safety in the use of the battery.

[0004] Replacing oil-based adhesives such as PVDF with water-based adhesives to make the lithium battery manufacturing process more environmentally friendly is currently one of the development trends in battery electrode materials. Existing water-based adhesives currently include polyacrylic acid (PAA), sodium carboxymethylcellulose / styrene-butadiene rubber (CMC / SBR), sodium alginate, and chitosan. Among these, SBR-type adhesives are widely applied to negative electrode systems because they require less addition to the system and have strong adhesion between the active material and the current collector. However, the low polarity of the components in SBR adhesives and their low affinity for highly polar electrolytes result in poor dynamic performance of lithium-ion batteries as an adhesive, making it difficult to achieve satisfactory rapid charging performance. Furthermore, SBR is generally used in combination with CMC, a thickening agent, and CMC has average adhesive performance, is highly brittle, and prone to cracking of the electrode material during charging and discharging. CN109802139A discloses an aqueous adhesive and battery comprising an adhesive component containing either styrene-butadiene latex or polyacrylic acid, and a thickening component containing either cyclodextrin or chitosan. While this aqueous adhesive can effectively reduce the shuttle effect of intermediate products, lower the risk of delamination, and improve the electrochemical performance of the battery, the glass transition temperature of polyacrylic acid is relatively high, making it relatively hard at room temperature and causing the electrodes to become hard and brittle. As a result, PAA aqueous adhesives are prone to cracking during the coating process, exhibit defects such as striped patterns after cold rolling, and cause powder scattering in the curved parts of the electrodes during the winding process, thus limiting their versatility in batteries. Furthermore, while natural polymer materials such as sodium alginate and chitosan are excellent as adhesives in terms of environmental friendliness and water solubility, they have many drawbacks in terms of electrochemical performance, mechanical performance, and adhesive performance, making it difficult to meet the application requirements of batteries.

[0005] Therefore, developing aqueous adhesive materials that simultaneously possess excellent bonding performance, rate performance, and cycle performance to meet the application requirements of high-performance battery electrodes and lithium-ion batteries is a problem that needs to be solved in this field. [Overview of the project]

[0006] The following is an overview of the topics described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] The embodiments of this application provide an aqueous adhesive, a method for producing the same, and its applications. By designing structural units such as polymer metal salts and polymerizable monomers, the aqueous adhesive can be given excellent adhesive performance, lithium ion conductivity, and appropriate swelling properties. When used in battery electrodes and lithium-ion batteries, the cycle performance and rate performance of the battery can be significantly improved.

[0008] According to the first embodiment, the embodiments of the present application provide an aqueous adhesive, the aqueous adhesive being a copolymer formed of a polymer metal salt and a polymerizable monomer, the polymerizable monomer including a combination of an acrylate monomer and an olefin monomer, and the polymer metal salt being one or at least two selected from a phosphate metal salt polymer, a carboxymetal salt polymer, a sulfonic acid metal salt polymer, or a bissulfonylimide metal salt polymer.

[0009] The aqueous adhesive provided by this application is a copolymer formed by the reaction of a polymer metal salt and a polymerizable monomer, wherein the polymerizable monomer includes a combination of acrylate monomers and olefin monomers having different solubility parameters, and by incorporating specific repeating structural units into copolymer segments formed by designing specific types of structural units such as polymer metal salts and polymerizable monomers, products with different solubility parameters can be obtained, thereby giving the aqueous adhesive appropriate swelling properties. At the same time, the structural fragments of the polymer metal salt can enhance the strength of the adhesive and the content of the metal salt, thereby giving the aqueous adhesive excellent adhesive performance and lithium ion conductivity. The aqueous adhesive provided by this application achieves a good balance effect between adhesive performance, lithium ion conductivity and swelling properties through the design of structural units in the copolymer, and simultaneously possesses excellent adhesive strength, adhesive stability and electrochemical performance, thereby significantly improving the cycle performance and rate performance of battery electrodes and lithium ion batteries containing it.

[0010] Preferably, the polymer metal salt comprises one or at least two of the following: polymer lithium salt, polymer sodium salt, polymer potassium salt, or polymer magnesium salt.

[0011] Preferably, the metal phosphate polymer is one or at least two selected from polymetal phosphate, 2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate metal salt polymer, bis(2-(methacryloyloxy)ethyl) phosphate metal salt polymer, 2-methacryloyloxyethyl phosphate metal salt polymer, or vinyl metal phosphate polymer; more preferably, it is one or at least two selected from lithium polyphosphate, 2-methyl-2-acrylic acid-2-hydroxyethyl ester lithium phosphate polymer, bis(2-(methacryloyloxy)ethyl) phosphate lithium polymer, 2-methacryloyloxyethyl phosphate lithium polymer, or vinyl lithium phosphate polymer.

[0012] Preferably, the carboxymetal salt polymer is one or at least two selected from methacrylate metal salt polymers, acrylic acid metal salt polymers, maleate metal salt polymers, itaconic acid metal salt polymers, citrate trialyl metal salt polymers, carboxymethylcellulose metal salt polymers, or alginate metal salt polymers, and more preferably one or at least two selected from lithium methacrylate polymers, lithium acrylate polymers, lithium maleate polymers, itaconic acid lithium polymers, citrate trialyl lithium polymers, carboxymethylcellulose lithium polymers, or alginate lithium polymers.

[0013] Preferably, the above sulfonic acid metal salt polymer is any one or at least two selected from styrene sulfonic acid metal salt polymer, vinyl sulfonic acid metal salt polymer, propenyl sulfonic acid metal salt polymer, methacrylic sulfonic acid metal salt polymer, 4-vinylbenzenesulfinate metal salt polymer, allyl vinyl sulfonic acid metal salt polymer, 3-sulfopropyl methacrylate metal salt polymer, 2-ethanesulfonate methacrylate metal salt polymer, 2-acrylamido-2-methyl-1-propanesulfonic acid metal salt polymer, 2-acrylamido-2-methylpropanesulfonic acid metal salt polymer, and 3-allyloxy-2-hydroxy-1-propanesulfonic acid metal salt polymer, and more preferably styrene sulfonic acid It is any one or at least two selected from lithium polymers, sodium styrene sulfonate polymers, potassium styrene sulfonate polymers, lithium vinyl sulfonate polymers, lithium propenyl sulfonate polymers, lithium methacrylate polymers, lithium 4-vinylbenzenesulfinate polymers, lithium allyl vinyl sulfonate polymers, lithium 3-sulfopropyl methacrylate polymers, lithium 2-ethanesulfonate methacrylate polymers, lithium 2-acrylamido-2-methyl-1-propanesulfonate polymers, lithium 2-acrylamido-2-methylpropanesulfonate polymers, and lithium 3-allyloxy-2-hydroxy-1-propanesulfonate polymers.

[0014] Preferably, the bissulfonylimide metal salt polymer is selected from vinyl bissulfonylimide metal salt polymers and / or styrene bissulfonylimide metal salt polymers, and more preferably from vinyl bissulfonylimide lithium polymers and / or styrene bissulfonylimide lithium polymers.

[0015] In this application, the term "polymer" in the above-mentioned polymer metal salt includes homopolymers and / or copolymers. Taking "methacrylate metal salt-based polymer" as an example, as long as the polymer contains structural units consisting of methacrylate metal salt, the polymer may be a homopolymer of methacrylate metal salt or a copolymer of methacrylate metal salt and other monomers. The other polymers have the same meaning, and for the sake of brevity, their explanation is omitted.

[0016] Preferably, the weight-average molecular weight of the polymer metal salt is 1,000 to 1,000,000, for example, 2,000, 5,000, 8,000, 10,000, 3,000, 5,000, 8,000, 1,000,000, 3,000,000, 5,000,000, 8,000,000, 1,000,000, 3,000,000, 5,000,000, 7,000,000 or 9,000,000, and may be specific point values ​​between the above point values, but for reasons of space and brevity, this application does not exhaustively list specific point values ​​included in the above range.

[0017] In this application, the above-mentioned polymer metal salt can be purchased from the market, or can be obtained by treating an acidic polymer with a metal salt formation treatment using a method known in the prior art.

[0018] Preferably, when the total mass of the polymer metal salt and polymerizable monomer is 100%, the mass of the polymer metal salt is 1 to 90%, and may be, for example, 2%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%, and specific point values ​​between the above point values, and is limited for reasons of space and brevity and the present application does not exhaustively list specific point values ​​that fall within the above range, but is more preferably 10 to 50%.

[0019] As a preferred technical solution of this invention, by setting the mass ratio of the polymer metal salt to 1 to 90%, more preferably 10 to 50%, the copolymer formed by the reaction contains structural fragments of the polymer metal salt in an appropriate proportion, thereby giving the aqueous adhesive excellent adhesive performance and lithium ion conductivity, while also exhibiting appropriate swelling characteristics, thereby giving the lithium-ion battery containing the aqueous adhesive even better cycle performance and rate performance. If the mass ratio of the polymer metal salt is too low, the strength of the aqueous adhesive decreases, and at the same time, the swelling rate in the electrolyte increases, causing the adhesive strength to deteriorate severely after long-term use, resulting in poor battery cycle performance. If the mass ratio of the polymer metal salt is too high, the flexibility of the aqueous adhesive is insufficient, affecting the processing performance of the electrode pieces.

[0020] Preferably, the acrylate monomer is an alkyl acrylate and / or an alkyl methacrylate. Preferably, the "alkyl group" in the alkyl acrylate and alkyl methacrylate is independently a C1-C10 linear or branched alkyl group, for example, a linear or branched alkyl group of C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10. For example, when the alkyl group is C1, it represents methyl acrylate or methyl methacrylate, and by analogy, for the sake of brevity, its explanation is omitted.

[0021] Preferably, the acrylate monomer includes one or at least two of the following: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, isooctyl acrylate, or octyl methacrylate.

[0022] Preferably, the olefin monomer comprises styrene and one or at least two combinations of C5-C10 (e.g., C5, C6, C7, C8, C9, or C10) linear or branched olefins. Preferably, the C5-C10 (e.g., C5, C6, C7, C8, C9, or C10) linear or branched olefins include, but are not limited to, pentene, hexene, heptene, octene, nonene, decene, and their respective isomers.

[0023] Preferably, the mass ratio of the acrylate monomer to the olefin monomer is (0.5 to 2):1, and may be, for example, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, or 1.9:1, and more preferably (0.8 to 1.5):1.

[0024] As a preferred technical solution of this invention, the mass ratio of the acrylate monomer to the olefin monomer is (0.5~2):1, more preferably (0.8~1.5):1, and the copolymer formed by the reaction contains structural fragments of polyacrylate and polyolefin in specific proportions, thereby giving the aqueous adhesive appropriate swelling properties, excellent adhesive performance, and lithium ion conductivity. By controlling the proportion of two polymerizable monomers having different solubility parameters, products with different solubility parameters can be obtained, allowing the swelling performance of the aqueous adhesive in the electrolyte to be adjusted, preventing loss of adhesive strength due to excessive swelling or loss of lithium ion conductivity due to insufficient swelling. If too much acrylate monomer is used, the swelling of the aqueous adhesive in the electrolyte becomes high, leading to decreased adhesive strength after prolonged use and poor battery cycle performance. If too much olefin monomer is used, the swelling of the aqueous adhesive becomes low, preventing good lithium ion conductivity and affecting the battery electrode and lithium-ion battery rate performance.

[0025] Preferably, the polymerizable monomer further comprises a functional monomer. Preferably, the functional monomer includes acrylic acid and / or methacrylic acid. Preferably, the mass percentage content of the functional monomer in the above polymerizable monomer is ≤ 10%, for example, it may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9% or 9.5%, etc.

[0026] As a preferred technical solution of the present application, the above polymerizable monomer further includes a functional monomer that contributes to the emulsion stability of the aqueous adhesive.

[0027] According to the second aspect, the embodiments of the present application provide a method for manufacturing the aqueous adhesive described in the first aspect. The above manufacturing method includes mixing a polymer metal salt, a polymerizable monomer, an initiator, and a solvent and then reacting them to obtain the above aqueous adhesive.

[0028] Preferably, the above initiator includes a persulfate, and more preferably ammonium persulfate. Preferably, when the mass of the above polymerizable monomer is 100%, the mass of the above initiator is 0.05 - 5%, for example, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, and specific point values between the above point values may also be acceptable. Limited by reasons of space and conciseness, the present application does not comprehensively list the specific point values included in the above range.

[0029] Preferably, the above solvent includes water.

[0030] Preferably, the temperature of the above reaction is 60 - 80°C, for example, 61°C, 63°C, 65°C, 68°C, 70°C, 71°C, 73°C, 75°C, 77°C or 79°C, and specific point values between the above point values may also be acceptable. Limited by reasons of space and conciseness, the present application does not comprehensively list the specific point values included in the above range.

[0031] Preferably, the reaction time is 1 to 12 hours, and may be, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, or 11 hours, and specific point values ​​between the above point values, but for reasons of space and brevity, this application does not exhaustively list specific point values ​​that fall within the above range.

[0032] Preferably, the reaction further includes a neutralization step after completion of the above reaction. Preferably, the neutralizing reagent is a lithium hydroxide solution.

[0033] According to a third aspect, the embodiments of the present application provide an application of the aqueous adhesive described in the first aspect to a battery material. Preferably, the battery material is a lithium-ion battery material.

[0034] According to a fourth aspect, an embodiment of the present application provides a battery electrode piece containing the aqueous adhesive described in the first aspect. Preferably, the battery electrode piece includes a current collector and a coating layer installed on the current collector, and the material of the coating layer includes the aqueous adhesive described in the first embodiment.

[0035] Preferably, the material of the coating layer includes an active material, a conductive agent, and the aqueous adhesive described in the first embodiment.

[0036] Preferably, the battery electrode piece is the negative electrode piece.

[0037] According to the fifth aspect, an embodiment of the present application provides a lithium-ion battery comprising at least one of the aqueous adhesive described in the first aspect and the battery electrode described in the fourth aspect.

[0038] The embodiments of this application have the following beneficial effects on related technologies. In the aqueous adhesive provided by the embodiments of this application, specific repeating structural units are incorporated into the formed copolymer segment through the design and synergy of structural units such as polymer metal salts and polymerizable monomers, thereby giving the aqueous adhesive appropriate swelling properties, excellent adhesive performance, and lithium ion conductivity. Its swelling rate in the electrolyte (85°C, 24h) can be adjusted within the range of 10-100%, and its peel stress is 15-30 N / m. It simultaneously possesses excellent adhesive strength, adhesive stability, and electrochemical performance, significantly improving the cycle performance and rate performance of lithium-ion batteries containing it. When the aqueous adhesive is used in the negative electrode piece, the lithium-ion battery achieves a capacity retention rate of ≥98% and a 3C capacity retention rate of ≥94% at room temperature after 100 cycles, demonstrating excellent cycle performance and rate performance, and meeting the application requirements for high-performance lithium-ion batteries.

[0039] Other aspects will become clear after reading and understanding the drawings and detailed descriptions. [Modes for carrying out the invention]

[0040] The technical solutions of this application will be further described below with reference to specific embodiments. Those skilled in the art should understand that the above embodiments are merely to aid in understanding this application and do not specifically limit it. The terms “include,” “contain,” “have,” and “contain,” as used herein, or any other variations thereof, are intended to cover non-exclusive inclusion. For example, a composition, step, method, product, or apparatus containing the enumerated elements is not necessarily limited to those elements and may further include other elements not expressly enumerated or elements specific to such composition, step, method, product, or apparatus.

[0041] "Optionally" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both cases where the event occurs and cases where it does not. The indefinite articles "one kind" and "one" preceding an element or component in this application do not limit the number requirement (i.e., the number of occurrences) of the element or component. Therefore, "one" or "one kind" should be interpreted as including one or at least one, and singular elements or components also include plural forms unless the number clearly means singular only.

[0042] The use of terms such as “one embodiment,” “several embodiments,” “exemplary examples,” “specific examples,” or “several examples” in this application means that the specific features, structures, materials, or properties described in accordance with the embodiment or example are included in at least one embodiment or example of this application. In this specification, exemplary descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0043] Furthermore, the technical features relating to each embodiment of this application can be combined with each other, as long as they do not contradict each other.

[0044] Example 1 A water-based adhesive and a method for producing the same, wherein the water-based adhesive is a copolymer formed by the reaction of lithium polyacrylate (weight-average molecular weight of 10,000, purchased from Macklin) with a polymerizable monomer, the mass ratio of lithium polyacrylate to polymerizable monomer is 1:2, and the polymerizable monomer is a mixed monomer of styrene (St), butyl acrylate (BA), and acrylic acid (AA), containing 50% styrene, 48% butyl acrylate, and 2% acrylic acid by mass percentage.

[0045] The method for producing the above aqueous adhesive was as follows: 550 parts by mass of deionized water was added to 50 parts by mass of lithium polyacrylate, the temperature was raised to 70°C and stirred, 100 parts by mass of polymerizable monomer (the above mixed monomer) was added, and 0.25 parts by mass of ammonium persulfate was further added, and the reaction was allowed to proceed for 6 hours. After the reaction was complete, the pH value was adjusted to 7.0 with a 10% lithium hydroxide solution to obtain the above aqueous adhesive.

[0046] Example 2 The present invention relates to an aqueous adhesive and a method for producing the same, the only difference from Example 1 being that lithium polyacrylate was replaced with an equal mass of potassium poly2-methyl-2-acrylic acid-2-hydroxyethyl ester phosphate (weight-average molecular weight of 10,000, purchased from Macklin), while all other components, mixing ratios, and manufacturing methods were the same as in Example 1.

[0047] Example 3 The present invention relates to an aqueous adhesive and a method for producing the same, the only difference from Example 1 being that lithium polyacrylate was replaced with an equal mass of sodium polystyrene sulfonate (with a weight-average molecular weight of 10,000, purchased from Macklin); all other components, mixing ratios, and manufacturing methods were the same as in Example 1.

[0048] Example 4 The present invention relates to an aqueous adhesive and a method for producing the same, the only difference from Example 1 being that lithium polyacrylate was replaced with an equal mass of lithium polyvinylbissulfonylimide (with a weight-average molecular weight of 10,000, purchased from Macklin); all other components, mixing ratios, and manufacturing methods were the same as in Example 1.

[0049] Example 5 The present invention relates to an aqueous adhesive and a method for producing the same. The only difference from Example 1 is that the mass ratio of lithium polyacrylate to polymerizable monomer is 1:49. All other components, mixing ratios, and manufacturing methods are the same as in Example 1.

[0050] Example 6 The present invention relates to an aqueous adhesive and a method for producing the same. The only difference from Example 1 is that the mass ratio of lithium polyacrylate to polymerizable monomer is 4:1; all other components, mixing ratios, and manufacturing methods are the same as in Example 1.

[0051] Example 7 The present invention relates to an aqueous adhesive and a method for producing the same. The only difference from Example 1 is that the molecular weight of lithium polyacrylate is 100,000; all other components, mixing ratios, and manufacturing methods are the same as in Example 1.

[0052] Example 8 The present invention relates to an aqueous adhesive and a method for producing the same. The only difference from Example 1 is that the molecular weight of lithium polyacrylate is 1,000,000; all other components, mixing ratios, and manufacturing methods are the same as in Example 1.

[0053] Example 9 The present invention relates to an aqueous adhesive and a method for producing the same, the difference from Example 1 being that the mass ratio of lithium polyacrylate to polymerizable monomer is 1:1, and the polymerizable monomer is a mixed monomer of styrene, butyl acrylate, and acrylic acid, containing 40% styrene, 52% butyl acrylate, and 8% acrylic acid by mass percentage, while the other components, mixing ratios, and manufacturing method are all the same as in Example 1.

[0054] Example 10 The present invention relates to an aqueous adhesive and a method for producing the same, the difference from Example 1 being that the mass ratio of lithium polyacrylate to polymerizable monomer is 1:9, and the polymerizable monomer is a mixed monomer of styrene, butyl acrylate, and acrylic acid, containing 52% styrene, 43% butyl acrylate, and 5% acrylic acid by mass percentage, while the other components, mixing ratios, and manufacturing method are the same as in Example 1.

[0055] Example 11 The present invention relates to an aqueous adhesive and a method for producing the same, the only difference from Example 1 being that the polymerizable monomer contains 35% styrene, 60% butyl acrylate, and 5% acrylic acid by mass percentage, while the other components, mixing ratios, and manufacturing method are the same as in Example 1.

[0056] Example 12 The present invention relates to an aqueous adhesive and a method for producing the same, the only difference from Example 1 being that the polymerizable monomer contains 60% styrene, 35% butyl acrylate, and 5% acrylic acid by mass percentage, while the other components, mixing ratios, and manufacturing method are the same as in Example 1.

[0057] Comparative Example 1 A water-based adhesive and a method for producing the same, wherein the water-based adhesive is a copolymer of polymerizable monomers (styrene, butyl acrylate, and acrylic acid), and the polymerizable monomers contain 50% styrene, 48% butyl acrylate, and 2% acrylic acid by mass percentage.

[0058] The method for producing the above aqueous adhesive was as follows: 200 parts by mass of deionized water was mixed with 50 parts by mass of polymerizable monomer, and 0.25 parts by mass of ammonium persulfate was further added. The mixture was reacted at 70°C for 6 hours, and after the reaction was complete, the pH was adjusted to 7.0 with a 10% lithium hydroxide solution to obtain the above aqueous adhesive.

[0059] Comparative Example 2 The present invention relates to an aqueous adhesive and a method for producing the same. The only difference from Example 1 is that the polymerizable monomer is a mixed monomer of styrene and acrylic acid, containing 98% styrene and 2% acrylic acid by mass percentage. All other components, mixing ratios, and manufacturing methods are the same as in Example 1.

[0060] Comparative Example 3 The present invention relates to an aqueous adhesive and a method for producing the same. The only difference from Example 1 is that the polymerizable monomer is a mixed monomer of butyl acrylate and acrylic acid, containing 98% butyl acrylate and 2% acrylic acid by mass percentage. All other components, mixing ratios, and manufacturing methods were the same as in Example 1.

[0061] Comparative Example 4 A water-based adhesive and a method for producing the same, wherein the water-based adhesive is a copolymer formed by the reaction of lithium acrylate (LiAA) and a polymerizable monomer, the mass ratio of lithium acrylate to polymerizable monomer is 1:2, and the polymerizable monomer is a mixed monomer of styrene, butyl acrylate and acrylic acid, containing 50% styrene, 48% butyl acrylate and 2% acrylic acid by mass percentage.

[0062] The method for producing the above aqueous adhesive was as follows: 550 parts by mass of deionized water was mixed with 50 parts by mass of lithium acrylate and 100 parts by mass of polymerizable monomer, and 0.75 parts by mass of ammonium persulfate was further added. The mixture was reacted at 70°C for 6 hours, and after the reaction was complete, the pH was adjusted to 7.0 with a 10% lithium hydroxide solution to obtain the above aqueous adhesive.

[0063] Comparative Example 5 A water-based adhesive and a method for producing the same, wherein the water-based adhesive is a mixture of lithium polyacrylate and a terpolymer of styrene-butyl acrylate-acrylic acid, the mass ratio of lithium polyacrylate to the terpolymer is 1:2, and the polymerizable monomers of the terpolymer contain 50% styrene, 48% butyl acrylate, and 2% acrylic acid by mass percentage.

[0064] The method for producing the above aqueous adhesive was as follows: 500 parts by mass of deionized water was added to 100 parts by mass of polymerizable monomer of a ternary copolymer, and 0.25 parts by mass of ammonium persulfate was further added. The mixture was reacted at 70°C for 6 hours. After the reaction was complete, the pH was adjusted to 7.0 with a 10% lithium hydroxide solution. Next, 50 parts by mass of lithium polyacrylate was added to the system, and the mixture was stirred at room temperature to obtain the above aqueous adhesive.

[0065] Comparative Example 6 A commercially available SBR adhesive, a water-based adhesive.

[0066] Comparative Example 7 LA132 adhesive is a commercially available water-based adhesive.

[0067] Application examples The battery electrode piece is a negative electrode piece comprising a current collector (Cu foil) and a coating layer installed on the current collector, wherein the material of the coating layer comprises a negative electrode active material (silicone material SiO-450, BTR New Energy Materials Inc., silicon content 10%), a conductive agent (carbon black SP), an adhesive and a thickener (carboxymethylcellulose sodium CMC), and the adhesive was an aqueous adhesive provided in Examples 1 to 12 and Comparative Examples 1 to 7, respectively.

[0068] The method for manufacturing the above-mentioned negative electrode pieces was as follows: The negative electrode active material, conductive agent, adhesive, and thickener were mixed in a mass ratio of 96.5:1.0:1.0:1.5, and this mixture was added to deionized water at a solid content of 40 wt% of the system. The mixture was thoroughly stirred and mixed to obtain a uniform negative electrode slurry. After passing the slurry through a 100-mesh screen, it was applied to a negative electrode current collector Cu foil, dried further, and roll-pressed with a roller at a unit length load of 10 × 10⁴ N / m to obtain the negative electrode pieces.

[0069] A lithium-ion battery comprising a positive electrode piece, a negative electrode piece, a separator, and an electrolyte, wherein the negative electrode piece is the negative electrode piece described above, and the manufacturing method was as follows:

[0070] (1) Manufacturing of positive electrode pieces: The positive electrode active material (lithium iron phosphate material), conductive carbon black, and adhesive (PVDF) are mixed in a solids-to-mass ratio of 96.5:2.0:2.5. This mixture is added to N-methylpyrrolidone (NMP) at a solids content of 50 wt%, and thoroughly stirred to form a uniform positive electrode slurry. After passing it through a 100-mesh screen, it is applied to the positive electrode current collector Al foil, dried, and then rolled out in 10 × 10 4 A roll press was performed with a unit length load of N / m to obtain a positive electrode piece;

[0071] (2) Negative pole piece: As described above;

[0072] (3) Separator: A porous PE polymer film (Shenzhen Xingyuan Material Technology Co., Ltd.) was used as the separator;

[0073] (4) Assembly of lithium-ion battery: The positive electrode piece, separator, and negative electrode piece are wound in order to obtain a cell, the cell is sealed with an aluminum plastic film, moisture is removed by firing, then the electrolyte is injected, and the lithium-ion battery is obtained through processes such as vacuum sealing, standing, chemical conversion, secondary sealing, and shaping.

[0074] Performance testing: (1) Swelling performance The aqueous adhesive to be measured was dropped into a clean mold, ensuring that the solid content was 4 g ± 0.1 g. The mold was then dried in a drying box at 70°C for 12 hours, a 1 cm × 1 cm section was taken out, and then dried at 120°C for 2 hours to prepare it for use. The prepared film was weighed and its mass M1 was recorded. Approximately 5 g of electrolyte was weighed and added to the glass bottle containing the film. The bottle was sealed so that the electrolyte was completely immersed in the film, and left in an 85°C water bath for 24 hours. The film was removed from the glass bottle, the electrolyte on the film was wiped off with clean airlaid paper and dried, and the mass of the swollen film was weighed and recorded as M2.

[0075] Swelling rate = 100% x (M2-M1) / M1.

[0076] (2) Adhesive performance The negative electrode piece is cut into a long strip measuring 20 cm x 2.5 cm, and attached to a 1 mm thick steel plate on the current collector side with double-sided tape. Cellophane tape is then attached to the coated layer side, and the coated layer is peeled off in a 180° direction at a speed of 100 mm / min using a tensile testing machine. The peel stress is measured, and the peel stress is used as the basis for determining the adhesive performance. A larger peel stress indicates better adhesive strength.

[0077] (3) Battery cycle performance and rate performance The lithium-ion battery manufactured as described above was charged to 4.2V with a constant current of 0.33C, then charged again at a constant voltage until the cutoff current reached 0.02C, discharged to 2.5V at 0.33C, left for 5 minutes, then charged again to 4.2V with a constant current of 0.33C, charged again at a constant voltage until the cutoff current reached 0.02C, and discharged to 2.5V at 0.33C for initial adjustment.

[0078] At 25°C, the lithium-ion battery, after initial adjustment, was charged to 4.2V with a constant current of 0.5C, then charged again with a constant voltage until the cutoff current reached 0.02C, left for 5 minutes, and then discharged to 2.5V with a constant current of 1C, left for 5 minutes, and the discharge capacity of the first cycle was measured. After 100 charge / discharge cycles in this manner, the discharge capacity at the 100th cycle was measured, and the capacity retention rate at the 100th cycle was calculated using the following formula.

[0079] Capacity retention rate after 100 cycles (%) = 100% × Discharge capacity at 100 cycles / Discharge capacity at the first cycle.

[0080] Rate performance: At 25°C, the lithium-ion battery, after initial adjustment, was charged to 4.2V with a constant current of 0.5C, then charged at a constant voltage until the cutoff current reached 0.02C, left for 5 minutes, then discharged to 2.5V with a constant current of 1C, left for 5 minutes, and the discharge capacity at 1C was measured. Next, it was charged to 4.2V with a constant current of 0.5C, then charged at a constant voltage until the cutoff current reached 0.02C, left for 5 minutes, then discharged to 2.5V with a constant current of 3C, left for 5 minutes, and the discharge capacity at the 3C rate was measured.

[0081] 3C capacity retention rate (%) = 100% x 3C discharge capacity / 1C discharge capacity.

[0082] The results of the performance tests are shown in Tables 1 and 2.

[0083] [Table 1]

[0084] In Table 1, "--" indicates that the component is not included and that the data does not exist.

[0085] [Table 2]

[0086] As can be seen by combining the performance test data in Tables 1 and 2, compared to commercially available SBR aqueous adhesives (Comparative Example 6) and LA132 adhesives (Comparative Example 7), the present invention, through the design of the structural units of polymer metal salts and polymerizable monomers and their synergy, provides appropriate swelling characteristics to the aqueous adhesive. The swelling rate after being left in the electrolyte at 85°C for 24 hours can be adjusted within the range of 10-100%, and it has good adhesive performance and lithium ion conductivity. The peel stress when used on the negative electrode piece is 15-30 N / m, and the adhesive strength is clearly improved compared to commercially available aqueous adhesives. It also has good lithium ion conductivity, rate performance and cycle performance. The capacity retention rate of lithium ion batteries containing it after 100 cycles at room temperature is 97.5-99%, and the 3C capacity retention rate is 94-96.3%, showing a clear improvement in cycle performance and rate performance. Simultaneously, by adjusting the ratio of polymer metal salts to polymerizable monomers and designing the blending ratio of acrylate-based monomers to olefin-based monomers in the polymerizable monomers, the performance of water-based adhesives can be adjusted and optimized.

[0087] The aqueous adhesive provided by this application is a copolymer formed by the reaction of a polymer metal salt and a polymerizable monomer. The polymerizable monomer includes acrylate monomers and olefin monomers. By designing the structural units in the copolymer, the aqueous adhesive achieves a good balance between adhesive performance, lithium ion conductivity, and swelling characteristics. The adhesive does not lose adhesive strength due to excessive swelling, nor does it lose lithium ion conductivity due to excessive swelling, and simultaneously possesses excellent adhesive strength, adhesive stability, and electrochemical performance. When the aqueous adhesive does not contain the structural units of a polymer metal salt (Comparative Example 1), the swelling rate in the electrolyte is too high, resulting in insufficient adhesive strength and lithium ion conductivity, and a significant decrease in the battery's cycle performance and rate performance. When the polymerizable monomer does not contain acrylate monomers (Comparative Example 2), the adhesive performance of the aqueous adhesive is low, and the battery's cycle performance and rate performance are reduced. When the polymerizable monomer does not contain olefin monomers (Comparative Example 3), the performance of the aqueous adhesive is reduced, decreasing the capacity retention rate of the lithium-ion battery, and the cycle performance is relatively low. Furthermore, when a polymer metal salt and a styrene-butyl acrylate-acrylic acid ternary copolymer were present in a blended form in the adhesive (Comparative Example 5), or when a metal salt containing a double bond was copolymerized with another polymerizable monomer (Comparative Example 4), it was not possible to form copolymers containing specific repeating units and segment structures, resulting in reduced adhesive strength of the aqueous adhesive and poor battery cycle performance.

[0088] The applicant declared that while the present application illustrates the aqueous adhesive, its manufacturing method, and applications using the above-described examples, the present application is not limited to the above-described examples, and that it does not mean that one must rely on the above-described examples to carry out the present application. It will be apparent to those skilled in the art that any improvements to the present application, equivalent substitutions and additions of auxiliary components to the raw materials of the present product, and selection of specific forms are all included within the claims and disclosures of the present application.

Claims

1. It is a water-based adhesive, A copolymer formed from a polymer metal salt and a polymerizable monomer, wherein the polymerizable monomer includes a combination of an acrylate monomer and an olefin monomer, the mass ratio of the acrylate monomer to the olefin monomer is (0.5 to 2):1, the olefin monomer includes one or at least two of styrene, C5 to C10 linear or branched olefins, and the polymer metal salt is one or at least two selected from a phosphate metal salt polymer, a carboxymetal salt polymer, a sulfonic acid metal salt polymer, or a bissulfonylimide metal salt polymer. Water-based adhesive.

2. The polymer metal salt comprises one or at least two of the following: polymer lithium salt, polymer sodium salt, polymer potassium salt, or polymer magnesium salt. The aqueous adhesive according to claim 1.

3. The metal phosphate polymer is one or at least two selected from polymetal phosphate, 2-methyl-2-acrylate-2-hydroxyethyl ester phosphate metal salt polymer, bis(2-(methacryloyloxy)ethyl) phosphate metal salt polymer, 2-methacryloyloxyethyl phosphate metal salt polymer, or vinyl metal phosphate polymer. The aqueous adhesive according to claim 1 or 2.

4. The carboxymetal salt polymer is one or at least two selected from methacrylate metal salt polymers, acrylic acid metal salt polymers, maleate metal salt polymers, itaconic acid metal salt polymers, trialyl citrate metal salt polymers, carboxymethylcellulose metal salt polymers, or alginate metal salt polymers. The aqueous adhesive according to claim 1 or 2.

5. The sulfonic acid metal salt polymer is one or at least two selected from styrene sulfonic acid metal salt polymer, vinyl sulfonic acid metal salt polymer, propenyl sulfonic acid metal salt polymer, methacrylic sulfonic acid metal salt polymer, 4-vinylbenzenesulfinate metal salt polymer, allyl vinyl sulfonic acid metal salt polymer, 3-sulfopropyl methacrylate metal salt polymer, 2-ethanesulfonate methacrylate metal salt polymer, 2-acrylamido-2-methyl-1-propanesulfonic acid metal salt polymer, 2-acrylamido-2-methylpropanesulfonic acid metal salt polymer, and 3-allyloxy-2-hydroxy-1-propanesulfonic acid metal salt polymer. The aqueous adhesive according to claim 1 or 2.

6. The bissulfonylimide metal salt polymer is selected from vinyl bissulfonylimide metal salt polymers and / or styrene bissulfonylimide metal salt polymers. The aqueous adhesive according to claim 1 or 2.

7. The weight-average molecular weight of the polymer metal salt is between 1,000 and 1,000,000. The aqueous adhesive according to claim 1 or 2.

8. When the total mass of the polymer metal salt and polymerizable monomer is 100%, the mass of the polymer metal salt is 1 to 90%. The aqueous adhesive according to claim 1 or 2.

9. When the total mass of the polymer metal salt and polymerizable monomer is 100%, the mass of the polymer metal salt is 10 to 50%. The aqueous adhesive according to claim 1 or 2.

10. The acrylate monomer is an alkyl acrylate and / or an alkyl methacrylate. The aqueous adhesive according to claim 1 or 2.

11. The acrylate monomer is one or at least two of the following: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, isooctyl acrylate, or octyl methacrylate. The aqueous adhesive according to claim 1 or 2.

12. The mass ratio of the acrylate monomer to the olefin monomer is (0.8 to 1.5):

1. The aqueous adhesive according to claim 1 or 2.

13. The polymerizable monomer further comprises a functional monomer, the functional monomer comprising acrylic acid and / or methacrylic acid. The aqueous adhesive according to claim 1 or 2.

14. The mass percentage content of the functional monomer in the polymerizable monomer is ≤ 10%. The aqueous adhesive according to claim 13.

15. A method for producing an aqueous adhesive according to claim 1 or 2, The process involves mixing a polymer metal salt, a polymerizable monomer, an initiator, and a solvent, and then reacting them to obtain the aqueous adhesive. Manufacturing method.

16. The initiator comprises ammonium persulfate, The manufacturing method according to claim 15.

17. When the mass of the polymerizable monomer is taken as 100%, the mass of the initiator is 0.05 to 5%. The manufacturing method according to claim 15.

18. The solvent comprises water, the reaction temperature is 60 to 80°C, and the reaction time is 1 to 12 hours. The manufacturing method according to claim 15.

19. The step further comprises neutralizing after the completion of the reaction. The manufacturing method according to claim 15.

20. A battery material comprising the aqueous adhesive described in claim 1 or 2.

21. A battery electrode piece, A battery electrode piece comprising the aqueous adhesive described in claim 1 or 2.

22. The battery electrode piece includes a current collector and a coating layer installed on the current collector, wherein the material of the coating layer includes the aqueous adhesive described in claim 1 or 2. The battery electrode piece according to claim 21.

23. The battery electrode piece is a negative electrode piece. The battery electrode piece according to claim 21.

24. It is a lithium-ion battery, A lithium-ion battery comprising at least one of the aqueous adhesives described in claim 1 or 2 and the battery electrode pieces described in claim 21.

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