Macromolecular binder and preparation method thereof, battery diaphragm and battery

Abstract

The invention relates to the technical field of batteries, in particular to a polymer binder and a preparation method thereof, a battery diaphragm and a battery. The high-molecular binder comprises the following components: an emulsifier, a heat-resistant monomer, a cross-linking monomer, a soft monomer and an initiator, and the mass ratio of the heat-resistant monomer to the cross-linking monomer to the soft monomer is (5-8): (1-5): 1. The polymer binder can improve the defects of a PVDF binder, and has the advantages of no environmental pollution, wide hot pressing temperature range and high cohesiveness after liquid injection.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to a polymer binder and its preparation method, a battery separator, and a battery. Background Technology

[0002] Double-sided adhesive-coated separators are an important component of battery cells. An adhesive coating is introduced onto the surface of the separator. After stacking, by selecting appropriate hot-pressing parameters, the adhesive coating can bond the positive electrode, separator, and negative electrode into a whole, thereby optimizing the battery cell's casing yield and reducing the risk of initial battery cell short circuits.

[0003] Currently, the main component of the adhesive-coated separator is PVDF (polyvinylidene fluoride) micro- and nano-particles. PVDF contains approximately 59% fluorine, resulting in poor environmental performance, strong corrosiveness, and potential harm to human health. Furthermore, after electrolyte injection, disassembly of the battery cell revealed that the adhesion between the separator and the electrode interface is reduced due to the electrolyte filling, leading to poor interfacial adhesion and lower electrochemical performance during long-cycle operation. Summary of the Invention

[0004] The present invention aims to improve the defects of PVDF adhesive-coated separators and develop a battery separator material that is environmentally friendly, has a wide hot-pressing temperature range, and still has strong adhesion after liquid injection.

[0005] To solve or partially solve the above problems, as a first aspect, the present invention provides a polymeric adhesive comprising the following components: an emulsifier, a heat-resistant monomer, a crosslinking monomer, a soft monomer, and an initiator, wherein the mass ratio of the heat-resistant monomer, the crosslinking monomer, and the soft monomer is (5 to 8):(1 to 5):1.

[0006] Optionally, the heat-resistant monomer is selected from one or more of N,N-dimethylacrylamide, N,N-diethylacrylamide, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, p-phenylenediamine, triphenyl diether diamine, benzimidazole diamine, pinacol isopropenylborate, N-phenylmaleimide, cyclohexyl methacrylate, and acrylonitrile; And / or, the crosslinking monomer is selected from one or more of ethylene glycol dimethacrylate, divinylbenzene, vinyl alcohol, trimethylolpropane triacrylate, N,N'-methylenebisacrylamide, vinyl acetate, styrene, ethylene glycol terephthalate, allyl alcohol glycidyl ether, glycidyl methacrylate, triallyl cyanurate, tetraethoxysilane, ethylene glycol diglycidyl ether, hydroxypropyl methacrylate, triethylene glycol diacrylate, and 3,4-epoxy-1-butene; And / or, the soft monomer is selected from one or more of methyl acrylate, ethyl acrylate and butyl acrylate.

[0007] Optionally, in the polymer binder, the emulsifier has a mass percentage of 0.2 wt% to 10 wt% based on the total mass of the heat-resistant monomer, the crosslinking monomer, and the soft monomer, and the initiator has a mass percentage of 0.1 wt% to 10 wt%.

[0008] Optionally, the polymeric binder may further include a molecular weight regulator, wherein the molecular weight regulator is 0.1 wt% to 10 wt% by mass based on the total mass of the heat-resistant monomer, the crosslinking monomer, and the soft monomer.

[0009] Optionally, the polymeric adhesive may further include a buffer, wherein the mass ratio of the buffer to the initiator is (0.5 to 3):1.

[0010] Optionally, the molecular weight regulator is selected from one or more of dodecyl mercaptan, p-tert-butylphenol, and dodecyl trithiopropionate; And / or, the buffer is selected from one or more of sodium dimethyl carbonate, ammonium bicarbonate, potassium bicarbonate, sodium bicarbonate, sodium dihydrogen phosphate / potassium dihydrogen phosphate composite buffer solution, sodium chloride / boric acid composite buffer solution, and ammonia / ammonium chloride composite buffer solution; And / or, the emulsifier is selected from one or more of hexadecyltrimethylammonium chloride, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, and OP-10; And / or, the initiator is selected from one or more of potassium persulfate, ammonium persulfate and sodium sulfite.

[0011] As a second aspect, the present invention also provides a method for preparing a polymeric adhesive, for preparing the polymeric adhesive as described in the first aspect, the method for preparing the polymeric adhesive comprising: Heat-resistant monomers are added to fully dissolved emulsifiers. After dissolution is complete, a portion of initiator is added to carry out the first stage reaction and obtain an intermediate reaction solution. A mixture of crosslinking monomers and soft monomers is added dropwise to the intermediate reaction solution, and the remaining initiator is added to carry out a second-stage reaction to obtain the polymer binder.

[0012] Optionally, the temperature of the first stage reaction is 40°C to 95°C, and the temperature of the second stage reaction is 50°C to 95°C. And / or, the addition of a heat-resistant monomer to a fully dissolved emulsifier, followed by the addition of a portion of an initiator after dissolution, to carry out a first-stage reaction to obtain an intermediate reaction solution, further includes: Heat-resistant monomers are added to fully dissolved emulsifiers. After dissolution, a portion of initiator and a portion of molecular weight regulator are added to carry out the first stage reaction and obtain an intermediate reaction solution. And / or, the addition of a mixture of crosslinking monomers and soft monomers to the intermediate reaction solution, followed by the addition of the remaining initiator, to carry out a second-stage reaction to obtain the polymeric adhesive, further includes: A mixture of crosslinking monomers and soft monomers is added dropwise to the intermediate reaction solution, along with the remaining initiator and molecular weight regulator, to carry out the second-stage reaction. Finally, a buffer is added to obtain the polymer binder.

[0013] As a third aspect, the present invention provides a battery separator comprising a polymeric binder as described in the first aspect, or a polymeric binder prepared by a method for preparing a polymeric binder as described in the second aspect.

[0014] As a fourth aspect, the present invention provides a battery comprising a battery separator as described in the third aspect.

[0015] The advantages of this invention compared to related technologies include: This invention synthesizes a polymer binder by selecting a combination of heat-resistant monomers, crosslinking monomers, and soft monomers, dispersing the monomers into an emulsion under the action of an emulsifier, and then initiating the polymerization of the monomers with an initiator. The heat-resistant monomers have high glass transition temperatures and excellent heat resistance after polymerization, thus significantly improving the thermal shrinkage performance of the separator and the safety performance of the battery cell. The crosslinking monomers have strong hydrophilic properties, enabling crosslinking to form a network polymer and providing a large number of hydrophilic groups, which improves the hydrophilicity of the material, allowing the electrolyte to enter the polymer network structure, reducing the electrolyte absorption time of the battery cell, and improving the adhesion between the separator and the electrode after electrolyte injection. The soft monomers have low glass transition temperatures, which helps to make the softening point of the polymer binder much lower than that of PVDF, thus allowing hot pressing under different hot pressing conditions, widening the hot pressing temperature range of the battery cell to room temperature, and reducing hot pressing energy consumption. In summary, when the polymer binder in the embodiments of the present invention is applied to the battery separator, it can significantly improve the hot pressing performance of the battery separator and the electrochemical cycle performance of the battery cell. It has the advantages of being environmentally friendly, having a wide hot pressing temperature range, low thermal shrinkage, high wettability to electrolyte, and strong adhesion after electrolyte injection. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of the polymeric adhesive in an exemplary embodiment of the present invention; Figure 2 The image shows the actual battery cell obtained after being injected with electrolyte and left to stand at room temperature for 24 hours in Example 1. Figure 3 The image shows the actual battery cell obtained after filling it with electrolyte and letting it stand at room temperature for 24 hours, as shown in Comparative Example 1. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0018] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit this application. The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments". Definitions of other terms will be given in the description below. It should be noted that the concepts of "first," "second," etc., mentioned in this invention are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] In related technologies, due to the inherent limitations of PVDF, PVDF (polyvinylidene fluoride)-containing separators and electrodes, after being stacked, require hot pressing under high temperature (generally above 100℃) and high pressure conditions. This increases energy consumption, and furthermore, after electrolyte injection, the separator absorbs electrolyte slowly, requiring a long settling time. Additionally, after the coating absorbs electrolyte, the adhesive strength of the adhesive layer decreases to almost zero, resulting in poor interfacial adhesion between the electrode and separator, high ion transport impedance, and ultimately, poor electrochemical performance of the battery cell.

[0020] To improve the defects of current battery separators, this invention provides a polymer binder comprising the following components: emulsifier, heat-resistant monomer, crosslinking monomer, soft monomer, and initiator, wherein the mass ratio of heat-resistant monomer, crosslinking monomer, and soft monomer is (5 to 8): (1 to 5): 1.

[0021] In some optional embodiments, the heat-resistant monomer is selected from one or more of N,N-dimethylacrylamide, N,N-diethylacrylamide, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, p-phenylenediamine, triphenyl diether diamine, benzimidazole diamine, pinacol isopropenylborate, N-phenylmaleimide, cyclohexyl methacrylate, and acrylonitrile.

[0022] The crosslinking monomer is selected from one or more of ethylene glycol dimethacrylate, divinylbenzene, vinyl alcohol, trimethylolpropane triacrylate, N,N'-methylenebisacrylamide, vinyl acetate, styrene, ethylene glycol terephthalate, allyl alcohol glycidyl ether, glycidyl methacrylate, triallyl cyanurate, tetraethoxysilane, ethylene glycol diglycidyl ether, hydroxypropyl methacrylate, triethylene glycol diacrylate, and 3,4-epoxy-1-butene.

[0023] The soft monomer is selected from one or more of methyl acrylate, ethyl acrylate and butyl acrylate.

[0024] This invention synthesizes a polymer binder through emulsion polymerization by selecting a combination of heat-resistant monomers, crosslinking monomers, and soft monomers. These monomers are dispersed and form an emulsion under the action of an emulsifier, and then polymerization is initiated by an initiator. The heat-resistant monomers have high glass transition temperatures and excellent heat resistance after polymerization, thus significantly improving the thermal shrinkage performance of the separator and the safety performance of the battery cell. The crosslinking monomers have strong hydrophilic properties, enabling them to crosslink and form a network polymer. They also provide a large number of hydrophilic groups, improving the hydrophilicity of the material and allowing the electrolyte to enter the polymer network structure, reducing the electrolyte absorption time of the battery cell and improving the adhesion between the separator and the electrode after electrolyte injection. The soft monomers have low glass transition temperatures, which helps to make the softening point (25-80℃) of the polymer binder much lower than that of PVDF. This allows for hot pressing under different conditions, broadening the hot pressing temperature range of the battery cell to room temperature and reducing hot pressing energy consumption. In summary, when the polymer binder in the embodiments of the present invention is applied to the battery separator, it can significantly improve the hot pressing performance of the battery separator and the electrochemical cycle performance of the battery cell. It has the advantages of a wide hot pressing temperature range, small thermal shrinkage, high wettability to electrolyte, and strong adhesion after electrolyte injection.

[0025] In some alternative embodiments, the polymer binder contains an emulsifier at a mass percentage of 0.2 wt% to 10 wt% and an initiator at a mass percentage of 0.1 wt% to 10 wt% based on the total mass of the heat-resistant monomer, crosslinking monomer, and soft monomer.

[0026] The role of the emulsifier is to emulsify the monomers, dispersing them into fine droplets to form a stable oil-in-water emulsion and preventing monomer droplet aggregation. It also reduces the surface tension of the system, facilitating the dispersion of monomers and initiators in the aqueous phase. Furthermore, it forms micelles in water, solubilizing the monomers and providing a primary site for monomer polymerization. The role of the initiator is to initiate monomer polymerization. Specifically, optionally, the emulsifier is selected from one or more of hexadecyltrimethylammonium chloride, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, and OP-10, and the initiator is selected from one or more of potassium persulfate, ammonium persulfate, and sodium sulfite.

[0027] In some optional embodiments, the polymeric binder also includes a molecular weight regulator, which is 0.1 wt% to 10 wt% by mass based on the total mass of the heat-resistant monomer, crosslinking monomer, and soft monomer.

[0028] Specifically, the molecular weight regulator can be selected from one or more of dodecyl mercaptan, p-tert-butylphenol, and dodecyl trithiopropionate. The addition of the molecular weight regulator helps to improve the problem of excessively large molecular weight of the synthesized polymer, which leads to high viscosity and poor dispersibility.

[0029] Furthermore, in some optional embodiments, the polymer binder components further include a buffer, with the mass ratio of buffer to initiator being (0.5 to 3):1. Specifically, the buffer may be selected from one or more of sodium dimethyl carbonate, ammonium bicarbonate, potassium bicarbonate, sodium bicarbonate, sodium dihydrogen phosphate / potassium dihydrogen phosphate composite buffer solution, sodium chloride / boric acid composite buffer solution, and ammonia / ammonium chloride composite buffer solution. The buffer is used to maintain the pH of the polymer binder system within a suitable range, specifically 7 to 9, to maintain the stability of the emulsion system, while allowing the functional monomers to participate in the reaction and distribution in the intended manner, thereby ensuring that the emulsion polymerization reaction proceeds at a smooth and rapid rate.

[0030] Another embodiment of the present invention also provides a method for preparing a polymeric adhesive, for preparing the above-mentioned polymeric adhesive, referring to... Figure 1 As shown, the preparation method of the polymer adhesive includes: Step (1): Add heat-resistant monomer to the fully dissolved emulsifier. After dissolution, add a portion of initiator to carry out the first stage reaction and obtain the intermediate reaction solution.

[0031] It should be noted that, in this step, when adding a portion of the initiator, a portion of the molecular weight regulator may also be added. The emulsion polymerization reaction in this embodiment can be carried out in a reactor equipped with a reflux condenser and a stirring device. Since the emulsion polymerization reaction includes two stages, the initiator and the molecular weight regulator can be added separately in the first and second stages of the reaction, respectively.

[0032] Specifically, in this step, deionized water and emulsifier are added to a 500ml three-necked flask, and the emulsifier is fully dissolved at room temperature with the stirrer turned on. Then, the temperature is gradually increased to the temperature of the first-stage reaction, and all the heat-resistant monomer is added under nitrogen protection. Stirring continues until the heat-resistant monomer is completely dissolved and dispersed. Finally, under stirring, the initiator and molecular weight regulator of the first-stage reaction are added, and after reacting for a period of time, an intermediate reaction solution is obtained. The temperature of the first-stage reaction can be from 40℃ to 95℃.

[0033] Step (2): Add a mixture of crosslinking monomers and soft monomers to the intermediate reaction solution, and add the remaining initiator to carry out the second stage reaction to obtain a polymer binder.

[0034] Specifically, a mixture of crosslinking monomers and soft monomers can be slowly added dropwise to the intermediate reaction solution, preferably over a period of 10 to 180 minutes. After the addition is complete, the reaction can proceed for a period of time, typically 10 to 240 minutes. Additionally, when adding the remaining initiator in this step, the remaining molecular weight regulator can also be added. After continuing the reaction for a period, the temperature is raised to the second-stage reaction temperature and held at that temperature for 10 to 180 minutes before stopping the reaction. The temperature of the second-stage reaction can be 50 to 95°C. Furthermore, after the second-stage reaction is completed, a buffer can be added to the reaction solution to adjust the pH to 7 to 9, thus obtaining the polymer binder.

[0035] In this embodiment of the invention, by controlling the temperatures of both the first-stage reaction and the second-stage reaction below 100°C, it is beneficial to obtain a controllable and suitable reaction rate, as well as the desired high molecular weight and narrow distribution, thereby further ensuring product performance and enabling the product to have a low glass transition temperature. In addition, the above temperature range can also ensure that the emulsion polymerization reaction is completed, avoid residual monomers, and help maintain the stability of the emulsion system and control the morphology and structure of polymer particles.

[0036] In some optional embodiments, the mass percentage of the initiator added in the first stage reaction is 20 wt% to 80 wt% based on the total mass of the initiator; at the same time, the mass percentage of the molecular weight regulator added in the first stage reaction is 30 wt% to 80 wt% based on the total mass of the molecular weight regulator.

[0037] Another embodiment of the present invention provides a battery separator, which includes the polymeric binder as described above, or the battery separator includes a polymeric binder prepared by the method described above. Specifically, the battery separator can be obtained by further preparing the polymeric binder into a slurry and coating it onto the surface of a base film. The base film can be selected from one or a combination of the following: a PE base film, a PE base film with a single-sided ceramic coating, a PE base film with a double-sided ceramic coating, and a PE base film with an LATP coating, etc.

[0038] Another embodiment of the present invention provides a battery comprising the battery separator as described above. Specifically, the battery of this embodiment is manufactured by stacking the battery separator, positive electrode, and negative electrode together, hot-pressing them into a casing, and then injecting electrolyte.

[0039] Specifically, in the battery of this embodiment, the positive electrode material may include at least one or more of lithium nickel manganese oxide, lithium manganese iron phosphate, and ternary materials (NCM111, NCM532, NCM622, NCM712, NCM811, NCA); the negative electrode material includes graphite, silicon-doped graphite, etc.; the hot-pressing temperature range is preferably 20 to 120°C, the hot-pressing time is preferably 15 to 300 s, and the pressure is preferably 100 to 2000 kg. In the electrolyte, the solvent is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate; the lithium salt is one or more of LiPF6, LiFSI, LiTFSI, LiBOB, and LiODFB; and the additive is one or more of ethylene carbonate, ethylene sulfate, 1,3-propane sulpholactone, fluoroethylene carbonate, and lithium difluorophosphate.

[0040] The present invention will be described in detail below through specific embodiments and comparative examples: Example 1 In this embodiment, the preparation steps of the polymer adhesive include: (1) Add 178.58 g of deionized water and 0.6 g of sodium dodecyl sulfate to a 500 ml three-necked flask equipped with a reflux condenser and a stirrer. Turn on the stirrer and set the speed to 800 rpm to allow the sodium dodecyl sulfate to dissolve completely at room temperature. Then gradually raise the temperature to 70 °C and add 13 g of N,N-diethylacrylamide to the three-necked flask under nitrogen protection. Continue stirring until the monomer is completely dissolved and dispersed. Under stirring conditions, add 0.06 g of potassium persulfate and 0.3 g of dodecyl trithiopropionate to the three-necked flask and react for 20 min to obtain an intermediate reaction solution.

[0041] (2) Slowly add 3g of triallyl cyanurate, 2g of 3,4-epoxy-1-butene and 2g of ethyl acrylate to the intermediate reaction solution. After the addition is complete, react for 60min. Then add the remaining 0.06g of potassium persulfate and 0.3g of dodecyl trithiopropionate and continue to react for 30min. Raise the reaction temperature to 80℃ and keep it at a constant temperature for 3h. Then stop the reaction. Add 0.1g of potassium bicarbonate and adjust the pH of the reaction solution to about 7 to obtain the polymer binder.

[0042] The polymer binder of this embodiment is mixed with polyacrylic acid and water in a mass ratio of 15:1:84 to form a slurry, which is then sprayed onto the surface of the base film to obtain the battery separator.

[0043] Furthermore, the battery separator and positive and negative electrode sheets in this embodiment are stacked and hot-pressed together, then assembled into a casing to prepare a dry battery cell. The positive electrode slurry, by mass percentage, is a ternary material (LiNi). 0.8 Co 0.1 Mn 0.1 O2):Conductive carbon black:Carbon nanotubes:Binder (PVDF-5130) = 96:1.2:1.6:1.2. The negative electrode slurry ratio is graphite:siloxane:carbon nanotubes:polyacrylic acid = 88:10:1:1. The positive electrode slurry is then coated onto aluminum foil, and after rolling and cutting, a positive electrode sheet is obtained. Similarly, the negative electrode slurry is coated onto copper foil, and after rolling and cutting, a negative electrode sheet is obtained.

[0044] After baking, the prepared dry cells were injected with electrolyte. The electrolyte composition was EC:EMC:DEC:LiPF6:FEC:DTD:LiPO2F2 = 15:40:22.5:15:5:2:0.5. After soaking at room temperature for 48 hours, the cells were formed at 25°C, aged at 45°C for 24 hours, degassed twice, and then capacity-tested at 0.33C. The cells were then subjected to subsequent tests.

[0045] Example 2 The difference between this embodiment and Embodiment 1 is that, in this embodiment, the preparation steps of the polymeric adhesive include: (1) Add 178.62 g of deionized water and 1 g of sodium dodecyl sulfate to a 500 ml three-necked flask equipped with a reflux condenser and a stirrer. Stir at 800 rpm to dissolve the monomer completely at room temperature. Then gradually heat to 70 °C and add 17 g of N,N-diethylacrylamide under nitrogen protection. Continue stirring until the monomer is completely dissolved and dispersed. Under stirring conditions, add 0.06 g of potassium persulfate and 0.1 g of dodecyl trithiopropionate. React for 10 min to obtain an intermediate reaction solution.

[0046] (2) Slowly add 3g of allyl alcohol glycidyl ether to the intermediate reaction solution. After the addition is complete, react for 60min. Then add the remaining 0.06g of potassium persulfate and 0.06g of dodecyl trithiopropionate and continue the reaction for 30min. Raise the reaction temperature to 95℃ and keep it at a constant temperature for 3h. Then stop the reaction and add 0.1g of potassium bicarbonate to adjust the pH to 7 to obtain the polymer binder.

[0047] Example 3 The difference between this embodiment and Example 1 is that, in this embodiment, the monomers 3g triallyl cyanurate, 13g N,N-diethylacrylamide, 2g ethyl acrylate, and 3,4-epoxy-1-butene are modified to 14g N-phenylmaleimide, 2g butyl acrylate, and 2g triethylene glycol diacrylate. Other process conditions remain unchanged.

[0048] Example 4 The difference between this embodiment and Example 1 is that, in this embodiment, the monomers 3g triallyl cyanurate, 13g N,N-diethylacrylamide, 2g ethyl acrylate, and 3,4-epoxy-1-butene are modified to 10g 4,4'-diaminodiphenyl ether, 6g ethylene terephthalate, and 2g butyl acrylate. Other process conditions remain unchanged.

[0049] Example 5 The difference between this embodiment and Embodiment 2 is that in this embodiment, allyl alcohol glycidyl ether is replaced with glycidyl methacrylate, while other process conditions remain unchanged.

[0050] Example 6 The difference between this embodiment and Embodiment 1 is that, in this embodiment, the monomers 3g triallyl cyanurate, 13g N,N-diethylacrylamide, 2g ethyl acrylate and 3,4-epoxy-1-butene are modified to 16g p-phenylenediamine, 10g styrene and 2g butyl acrylate.

[0051] Example 7 The difference between this embodiment and Embodiment 1 is that, in this embodiment, the monomers 3g triallyl cyanurate, 13g N,N-diethylacrylamide, 2g ethyl acrylate and 3,4-epoxy-1-butene are modified to 10g benzimidazole diamine, 2g tetraethoxysilane and 2g methyl acrylate.

[0052] Example 8 The difference between this embodiment and Embodiment 1 is that, in this embodiment, the monomers 3g triallyl cyanurate, 13g N,N-diethylacrylamide, 2g ethyl acrylate and 3,4-epoxy-1-butene are modified to 12g pyromellitic dianhydride, 2g trimethylolpropane triacrylate and 2g methyl acrylate.

[0053] Comparative Example 1 This comparative example follows the conventional lithium-ion battery manufacturing process, preparing a battery separator, positive electrode, and negative electrode. A slurry was prepared by mixing polyacrylic acid, PVDF, and water in a mass ratio of 1:15:84, and then sprayed onto the separator surface using the same method as in Example 1 to prepare a PVDF-coated separator. The battery was then assembled using the same method as in Example 1, and subsequent tests were performed.

[0054] The batteries from the above embodiments and comparative examples were subjected to cycle performance and thermal chamber tests, respectively. The cycle test method was a 25°C oven test, with a charge / discharge rate of 0.5C, and a constant current / constant voltage charging and discharging regime. The test voltage range was 2.8 to 4.2V. The test results are shown in Table 1. Table 1. Battery cycle performance test results for each embodiment and comparative example.

[0055] Furthermore, the batteries from each embodiment and comparative example were placed between two 8mm glass plates, and then the samples were placed in an oven heated to 130°C and stored for 1 hour before being removed. The shrinkage rate of each battery was calculated. The test results are shown in Table 2: Table 2. Battery shrinkage rate test results for each embodiment and comparative example.

[0056] After injecting electrolyte into the battery cells of Example 1 and Comparative Example 1, they were left to stand at room temperature for 24 hours and then disassembled. The corresponding physical images are shown below. Figure 2 and Figure 3 As shown. By Figure 2 and Figure 3 As can be seen from the comparison, compared with the phenomenon of cell delamination after disassembly in Comparative Example 1, the cell in Example 1 can still maintain a high degree of adhesion after liquid injection and no delamination phenomenon occurs.

[0057] According to Tables 1 and 2, a comparison between Examples 1 to 8 and Comparative Example 1 shows that by selecting appropriate monomer combinations and ratios, polymers with low glass transition temperatures can be synthesized, making the softening point of the polymer binder much lower than that of the PVDF coated separator, thereby widening the hot pressing temperature range of the battery cell (25-80°C) and achieving the effect of pressing at room temperature. Furthermore, the battery shrinkage rate of each example is significantly lower than that of Comparative Example 1.

[0058] Furthermore, a comparison of Examples 2 and 5 with Comparative Example 1 shows that although Examples 2 and 5 can reduce the hot-pressing temperature and improve the electrolyte wetting process compared to Comparative Example 1, their bonding performance and battery cycle performance are quite similar to Comparative Example 1 because no soft monomers were added to the polymer binder, and they failed the hot box test. In contrast, the batteries in the other examples showed significant improvements in bonding performance, cycle performance, and thermal stability.

[0059] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A polymeric adhesive, characterized in that, It comprises the following components: emulsifier, heat-resistant monomer, crosslinking monomer, soft monomer and initiator, wherein the mass ratio of the heat-resistant monomer, the crosslinking monomer and the soft monomer is (5 to 8): (1 to 5):

1.

2. The polymeric adhesive according to claim 1, characterized in that, The heat-resistant monomer is selected from one or more of N,N-dimethylacrylamide, N,N-diethylacrylamide, pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, p-phenylenediamine, triphenyl diether diamine, benzimidazole diamine, pinacol isopropenylborate, N-phenylmaleimide, cyclohexyl methacrylate, and acrylonitrile. And / or, the crosslinking monomer is selected from one or more of ethylene glycol dimethacrylate, divinylbenzene, vinyl alcohol, trimethylolpropane triacrylate, N,N'-methylenebisacrylamide, vinyl acetate, styrene, ethylene glycol terephthalate, allyl alcohol glycidyl ether, glycidyl methacrylate, triallyl cyanurate, tetraethoxysilane, ethylene glycol diglycidyl ether, hydroxypropyl methacrylate, triethylene glycol diacrylate, and 3,4-epoxy-1-butene; And / or, the soft monomer is selected from one or more of methyl acrylate, ethyl acrylate and butyl acrylate.

3. The polymeric adhesive according to claim 1, characterized in that, In the polymer binder, the emulsifier has a mass percentage of 0.2 wt% to 10 wt% based on the total mass of the heat-resistant monomer, the crosslinking monomer, and the soft monomer, and the initiator has a mass percentage of 0.1 wt% to 10 wt%.

4. The polymeric adhesive according to claim 1, characterized in that, The polymer binder also includes a molecular weight regulator, and the molecular weight regulator has a mass percentage of 0.1 wt% to 10 wt% based on the total mass of the heat-resistant monomer, the crosslinking monomer and the soft monomer.

5. The polymeric adhesive according to claim 4, characterized in that, The polymeric adhesive also includes a buffer, and the mass ratio of the buffer to the initiator is (0.5 to 3):

1.

6. The polymeric adhesive according to claim 5, characterized in that, The molecular weight regulator is selected from one or more of dodecyl mercaptan, p-tert-butylphenol and dodecyl trithiopropionate; And / or, the buffer is selected from one or more of sodium dimethyl carbonate, ammonium bicarbonate, potassium bicarbonate, sodium bicarbonate, sodium dihydrogen phosphate / potassium dihydrogen phosphate composite buffer solution, sodium chloride / boric acid composite buffer solution, and ammonia / ammonium chloride composite buffer solution; And / or, the emulsifier is selected from one or more of hexadecyltrimethylammonium chloride, sodium dodecylbenzenesulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, and OP-10; And / or, the initiator is selected from one or more of potassium persulfate, ammonium persulfate and sodium sulfite.

7. A method for preparing a polymeric adhesive, characterized in that, A method for preparing a polymeric adhesive as described in any one of claims 1 to 6, wherein the preparation method of the polymeric adhesive comprises: Heat-resistant monomers are added to fully dissolved emulsifiers. After dissolution is complete, a portion of initiator is added to carry out the first stage reaction and obtain an intermediate reaction solution. A mixture of crosslinking monomers and soft monomers is added dropwise to the intermediate reaction solution, and the remaining initiator is added to carry out a second-stage reaction to obtain the polymer binder.

8. The method for preparing the polymeric adhesive according to claim 7, characterized in that, The temperature of the first stage reaction is 40°C to 95°C, and the temperature of the second stage reaction is 50°C to 95°C. And / or, the addition of a heat-resistant monomer to a fully dissolved emulsifier, followed by the addition of a portion of an initiator after dissolution, to carry out a first-stage reaction to obtain an intermediate reaction solution, further includes: Heat-resistant monomers are added to fully dissolved emulsifiers. After dissolution, a portion of initiator and a portion of molecular weight regulator are added to carry out the first stage reaction and obtain an intermediate reaction solution. And / or, the addition of a mixture of crosslinking monomers and soft monomers to the intermediate reaction solution, followed by the addition of the remaining initiator, to carry out a second-stage reaction to obtain the polymeric adhesive, further includes: A mixture of crosslinking monomers and soft monomers is added dropwise to the intermediate reaction solution, along with the remaining initiator and molecular weight regulator, to carry out the second-stage reaction. Finally, a buffer is added to obtain the polymer binder.

9. A battery separator, characterized in that, The battery separator comprises a polymeric binder as described in any one of claims 1 to 6, or the battery separator comprises a polymeric binder prepared by the method for preparing the polymeric binder as described in claim 7 or 8.

10. A battery, characterized in that, The battery includes the battery separator as described in claim 9.

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