A non-fluorinated large-particle binder for lithium-ion battery ceramic separators, a composite ceramic separator, and a preparation method thereof.

Abstract

This invention relates to the field of lithium-ion batteries, specifically disclosing a non-fluorinated large-particle binder for lithium-ion battery ceramic separators, a composite ceramic separator, and a preparation method thereof. The separator uses polyphthalamide as the core and a modified material as the shell. The modified material is formed by sequentially grafting and modifying propylene monomer, acrylamide monomer, and glycidyl acrylate. The glass transition temperature (Tg1) of the polyphthalamide is ≥220℃, and the glass transition temperature (Tg2) of the modified material is 35–70℃. The particle size range of the non-fluorinated large-particle binder for lithium-ion battery ceramic separators is 4–30 μm. This application uses a large-particle binder as the binding component of the ceramic separator, which fully binds the inorganic powder, resulting in excellent overall performance of the ceramic separator, possessing both excellent electrochemical performance and excellent thermal stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a non-fluorine large-particle binder for lithium-ion battery ceramic separators, a preparation method thereof, and a composite ceramic separator. Background Technology

[0002] Lithium-ion batteries have advantages such as good cycle performance, high energy density, and environmental friendliness, making them a key area of ​​research in energy storage power supplies. The separator, as one of the four key components of a lithium-ion battery, plays a crucial role in isolating the positive and negative electrodes and providing a channel for lithium-ion transport.

[0003] In related technologies, lithium-ion battery separators are generally made of polyolefin membranes, such as polyethylene membranes and polypropylene membranes. While these membranes exhibit stable chemical and mechanical properties, they have relatively low melting points (polypropylene membranes have a melting point of only 165°C). Polyolefin membranes are prone to shrinkage and melting at high temperatures, leading to short circuits at the positive and negative electrode contacts. Furthermore, non-polar polyolefin membranes are difficult to wet with polar electrolytes, and some micropores in the membrane are difficult to fill with electrolyte, resulting in increased membrane impedance and ultimately affecting the battery's cycle performance and rate capability.

[0004] To address the shortcomings of polyolefin membranes, researchers have used polymer binders to laminate a ceramic coating composed of inorganic particles onto the surface of the polyolefin membrane. Commonly used polymer binders include polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene copolymer (PVDF-HFP), polyvinyl alcohol, sodium carboxymethyl cellulose, and polyimide.

[0005] PVDF and PVDF-HFP copolymers have low melting points, ranging from 115 to 170°C. When the external temperature approaches their melting point, PVDF and PVDF-HFP melt, failing to effectively adhere to inorganic particles, causing ceramic coatings to peel off, and failing to prevent the shrinkage of the polyolefin matrix membrane. Furthermore, PVDF and PVDF-HFP contain fluorine, which readily undergoes exothermic reactions with metallic lithium or graphite conductive agents at high temperatures, producing lithium fluoride and unsaturated C=CF bonds, leading to thermal runaway and posing safety hazards.

[0006] While using high-melting-point polyvinyl alcohol, sodium carboxymethyl cellulose, and polyimide as polymer binders can improve the thermal stability of the separator at higher temperatures (>150°C), these high-melting-point binders do not swell in the electrolyte like PVDF and PVDF-HFP, thus failing to improve adhesion and ionic conductivity. Therefore, although the use of these high-melting-point binders can improve the thermal stability of ceramic-coated separators at higher temperatures, it often comes at the cost of reduced battery electrochemical performance.

[0007] To address the aforementioned issues, the industry urgently needs to develop a binder that enables the diaphragm to possess both excellent electrochemical performance and excellent thermal stability. Summary of the Invention

[0008] In order to enable the separator to have both excellent electrochemical performance and thermal stability, this application provides a non-fluorine large particle binder for lithium-ion battery ceramic separators, a preparation method and a composite ceramic separator.

[0009] In a first aspect, this application provides a non-fluorinated large-particle binder for lithium-ion battery ceramic separators, employing the following technical solution:

[0010] A non-fluorinated large-particle binder for lithium-ion battery ceramic separators, with polyphthalamide as the core and modified material as the shell, wherein the modified material is grafted and modified from propylene monomer, acrylamide monomer and glycidyl acrylate.

[0011] The glass transition temperature Tg1 of the polyphthalamide is ≥220℃, and the glass transition temperature Tg2 of the modified material is 35~70℃;

[0012] The particle size range of the non-fluorinated large-particle binder used in the lithium-ion battery ceramic separator is 4–30 μm.

[0013] By adopting the above technical solutions, polyphthalamides include, but are not limited to, poly(phthalamide), poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide). Polyphthalamides possess excellent electrical insulation and electrochemical stability, thus making them suitable for use in batteries. Polyphthalamides contain a large number of rigid segments, have a regular structure, high crystallinity, high glass transition temperature, and high hardness. Using polyphthalamide as a core, it exhibits high hardness and excellent heat resistance, making it resistant to melting and deformation at high temperatures. This application uses polyphthalamide as a core and sequentially grafts propylene monomer, acrylamide monomer, and glycidyl acrylate to modify it, allowing the modified material to coat the surface of the polyphthalamide during molding, resulting in a large-particle binder.

[0014] Large particle binders have the following advantages:

[0015] First, the large-particle binder has a soft-shell, hard-core structure. By adjusting the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate in the modified material, the glass transition temperature of the modified material can be adjusted. This results in the hardness and glass transition temperature (Tg1) of the inner core material being much higher than the glass transition temperature (Tg2) of the shell material, while the hot-pressing temperature is higher than the glass transition temperature (Tg2) of the shell material but lower than its melting point. The large-particle binder can wet inorganic particles under hot-pressing conditions, thereby bonding the inorganic particles, which can then form a film layer during the hot-pressing process.

[0016] Meanwhile, the modified material retains some epoxy groups on its surface. These epoxy groups can be chemically bonded to the hydroxyl groups on the surface of inorganic powders (such as ceramic particles) during the wetting process, thereby reducing the probability of powder shedding from the inorganic powder.

[0017] Because the binder particles are significantly larger than the inorganic particles currently used, after being prepared into a slurry and coated, the binder particles can protrude significantly above the inorganic particles. This facilitates the bonding of the ceramic composite diaphragm to the electrode sheets via hot pressing, allowing the large binder particles to fully exert their bonding effect. This ensures that the composite diaphragm can bond well with the positive and negative electrode sheets, guaranteeing the bonding effect of the binder. The composite ceramic diaphragm can be obtained in one coating process, simplifying the production process, significantly reducing coating costs, and improving the yield rate.

[0018] Large-particle binders do not have an adhesive effect at room temperature. They only exert their adhesive effect after being softened by hot pressing. They will not stick together when being wound up and stored, thus further improving coating efficiency and yield.

[0019] Secondly, the core material of the large-particle binder is rich in polar functional groups—amides—which can form hydrogen bonds with the amide groups in the modified shell material. This restricts the flowability of the shell, allowing it to fully bond inorganic particles after softening, while also preventing it from flowing easily in a high-temperature molten state, thus reducing the possibility of inorganic particles falling off. The large-particle binder exhibits good adhesive stability.

[0020] Meanwhile, the large-particle binder modified material and polyphthalamide are rich in polar functional groups, allowing the electrolyte to pass through the pores of the large-particle binder without affecting the flow of the electrolyte due to the size of the binder particles.

[0021] The shell of the large-particle binder is grafted with propylene monomer, acrylamide monomer, and glycidyl acrylate to achieve a balanced ratio of polar and non-polar structural units in the modified material. Acrylamide monomer is rich in amide bonds, which are highly hydrophilic and can improve the wettability of the electrolyte on the membrane surface through hydrogen bonding, causing the membrane to swell and thus absorbing and retaining liquid. Meanwhile, glycidyl acrylate, being an ester, has better compatibility with esters in the electrolyte, ensuring good wetting of the binder. Therefore, glycidyl acrylate and acrylamide monomer have a synergistic effect in improving the wettability of the modified material, resulting in excellent liquid absorption performance of the membrane.

[0022] The flexible long chains of propylene monomers endow the modified material with excellent toughness, compensating for the defect of reduced polymer toughness caused by strong hydrogen bonding between polar functional groups such as amide and ester bonds. This makes the modified material less prone to breakage during swelling, resulting in excellent mechanical properties of the separator. Simultaneously, the long alkyl chains of the modified material possess a certain degree of hydrophobicity, ensuring a moderate overall swelling degree of the separator, maintained between 100% and 150%. This allows the separator to maintain good stability at the interface with the electrode, reducing battery impedance, while also minimizing the risk of breakage.

[0023] Furthermore, the modified material can fully adsorb inorganic particles through hydrogen bonding, allowing them to disperse effectively during the bonding process. This reduces the amount of binder needed and increases the content of active materials such as inorganic particles, thereby improving battery capacity. Simultaneously, the separator has low porosity, allowing lithium ions to easily pass through, reducing internal resistance and increasing ionic conductivity.

[0024] Finally, the high hard core glass transition temperature of the large-particle binder enables it to maintain a stable shape during hot pressing and during battery charging and discharging, preventing the collapse of the entire particle and the resulting blockage. This results in excellent heat resistance of the separator and a long service life for the lithium battery.

[0025] In summary, the binder prepared in this application can fully bind inorganic powders, resulting in excellent overall performance of the ceramic diaphragm, which possesses both excellent electrochemical performance and excellent thermal stability.

[0026] Preferably, the preparation method of the non-fluorine large particle binder for the lithium-ion battery ceramic separator includes the following steps: polyphthalamide particles are mixed with emulsifier, water, ethanol and oil-soluble initiator to obtain a pre-emulsion;

[0027] Propylene monomer is introduced into the pre-emulsion, the temperature is raised to 50-60℃, and the reaction is maintained for 2-4 hours;

[0028] Then add acrylamide monomer, control the reaction temperature at 50-60℃, and keep the reaction at this temperature for 4-5 hours;

[0029] Finally, glycidyl acrylate was added, and the reaction temperature was controlled at 50-60℃. The reaction was maintained at this temperature for 4-6 hours, and the modified material was obtained after purification.

[0030] By employing the above technical solution, polyphthalamide particles serve as the core, dispersed in water to form a pre-emulsion; propylene monomer and acrylamide are polymerized sequentially under the action of corresponding initiators, coating the core. Glycidyl acrylate is then introduced onto the acrylamide for modification, resulting in a non-fluorinated large-particle binder with a core-shell structure and suitable particle size for lithium-ion battery ceramic separators.

[0031] Preferably, the modified material is prepared by modifying propylene monomer, acrylamide monomer and glycidyl acrylate in a weight ratio of (1.2-1.5):(3.1-4.4):(4.1-5.7).

[0032] By adopting the above technical solution, within this weight ratio range, the glass transition temperature (Tg2) of the modified material is moderate; the epoxy group content on the surface of the modified material is high, which helps to further improve the bonding stability of large particle binders. In addition, the swelling degree of the modified material is as close as possible to 150%, and the wettability is good without reducing its mechanical properties.

[0033] The acrylamide monomer may be any one or more of the following monomers:

[0034] Methacrylamide, dimethacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-isopropylacrylamide, N,N'-vinylbisacrylamide, N-hydroxymethylacrylamide, etc.

[0035] Preferably, the acrylamide monomer is N-hydroxymethylacrylamide.

[0036] By adopting the above technical solution, the acrylamide monomers also contain hydroxyl groups, which can further enhance the shell material's ability to absorb and retain electrolyte.

[0037] Preferably, the particle size range of the non-fluorinated large-particle binder used in the lithium-ion battery ceramic separator is 10–15 μm.

[0038] By adopting the above technical solution, the non-fluorinated large particle binder has a moderate particle size, which makes the capillary effect of the diaphragm significant and can effectively improve the liquid absorption and retention capacity of the diaphragm.

[0039] Secondly, this application provides a composite ceramic diaphragm, which adopts the following technical solution:

[0040] A composite ceramic diaphragm comprises the following raw materials in parts by weight:

[0041] 30-70 parts ceramic particles;

[0042] 3-12 parts of non-fluorinated large-particle binder for lithium-ion battery ceramic separators;

[0043] 4-8 parts of auxiliary adhesive;

[0044] 0-5 parts of dispersant;

[0045] Thickener 2-8 parts;

[0046] 30-150 parts deionized water;

[0047] The non-fluorinated large-particle binder for lithium-ion battery ceramic separators is the aforementioned non-fluorinated large-particle binder for lithium-ion battery ceramic separators.

[0048] By adopting the above technical solution, deionized water is used as a solvent to prepare composite ceramic diaphragms, eliminating the need for organic solvents such as NMP, acetone, and ethanol. The deionized water, binder, ceramic particles, and additives are mixed and milled to prepare a slurry. The composite ceramic diaphragm is then prepared using a one-time coating process, which simplifies the coating process, makes it safer and more environmentally friendly, and significantly reduces costs.

[0049] The presence of large-particle binders in the composite ceramic separator provides a buffer space for the expansion during battery charge and discharge cycles, effectively solving the problem of cell deformation. The hard core layer of the large-particle binder continues to maintain its spherical structure during hot pressing, preventing the collapse of the overall binder particles and not affecting the air permeability and ionic conductivity of the separator.

[0050] Meanwhile, the large-particle binder does not contain fluorine, making it safe and environmentally friendly. It will not produce gaseous fluorides, thus avoiding potential safety hazards to the battery.

[0051] The ceramic particles are at least one of aluminum oxide, boehmite, and silicon dioxide, and the particle size of the ceramic particles is 0.1 μm to 2 μm.

[0052] The auxiliary binder is one or more of the following: acrylate resin, waterborne epoxy resin, waterborne polyurethane, ethylene-vinyl acetate copolymer, copolymerized modified polyvinyl alcohol, waterborne silicone resin, polyvinylidene fluoride, nitrile-polyvinyl chloride blend, polypropylene, and ultra-high molecular weight polyethylene.

[0053] The dispersant is one or more of carboxylates, sulfates, sulfonates, polyethylene glycol, polyvinyl alcohol, and polyethylene oxide; the dispersant may or may not be added. The large-particle binder shell material gives it better dispersibility and can be well dispersed in the composite ceramic diaphragm slurry.

[0054] Sodium carboxymethyl cellulose is generally chosen as a thickener.

[0055] The ceramic particles and the non-fluorine large particle binder for lithium-ion battery ceramic separators are subjected to sand milling. In the sand milling process, the sand mill speed is 2000-4000 rpm and the sand milling time is 2-3 hours.

[0056] By adopting the above technical solution, ceramic particles and other physical components are sand-milled, and the sand-milling process conditions are controlled so that the particles can be made smooth and round, thereby improving the quality of the ceramic diaphragm; while avoiding excessive sand-milling, which would cause a sharp drop in the content of shell material on the surface of the binder and reduce the bonding effect of the binder.

[0057] Thirdly, this application provides a method for preparing a composite ceramic diaphragm, employing the following technical solution:

[0058] A method for preparing a composite ceramic diaphragm includes the following steps:

[0059] Step 1: Mix ceramic particles, dispersant, thickener and some deionized water to obtain ceramic particle dispersion.

[0060] Step 2: Add all the binder and the remaining deionized water to the ceramic particle dispersion, stir and mix to obtain a ceramic diaphragm slurry; Step 3: Coat the ceramic composite slurry onto the base membrane and dry to obtain a composite ceramic diaphragm.

[0061] By adopting the above technical solution, the ceramic diaphragm produced has better quality, better electrochemical performance and stability, excellent mechanical properties, and is not prone to cell deformation.

[0062] In summary, this application has the following beneficial effects:

[0063] 1. Because the particle size of the adhesive used in this application is significantly larger than that of the ceramic particles currently used, after the ceramic slurry is prepared and coated, the adhesive particles can protrude significantly above the ceramic particles. This facilitates the bonding of the ceramic separator to the electrode sheets via hot pressing, allowing the large-particle adhesive to fully exert its bonding effect. This ensures that the composite separator can bond well with the positive and negative electrode sheets, guaranteeing the adhesive's bonding performance. A composite ceramic separator can be obtained in a single coating process, simplifying the production process, significantly reducing coating costs, and improving yield. Simultaneously, the presence of large-particle adhesive also provides buffer space for expansion during battery charge-discharge cycles, effectively solving the problem of cell deformation.

[0064] 2. In this application, propylene monomer, acrylamide monomer and glycidyl acrylate are used for graft modification, so that the ratio of polar structural units and non-polar structural units in the modified material is moderate. The large particle binder gives the separator excellent mechanical properties, so that the overall swelling degree of the separator is moderate and can be maintained at 100-150%. This allows the separator to maintain good stability at the interface with the electrode, reduce battery impedance, and is not prone to breakage.

[0065] 3. The large-particle binder possesses a double-layer core-shell structure. Its hard core has a high glass transition temperature, maintaining a stable shape during hot pressing and the exothermic charging and discharging of the battery. This prevents the collapse of the entire particle, which could lead to pore blockage. The separator exhibits excellent heat resistance, resulting in a long lithium battery lifespan. The core material is rich in polar functional groups—amides—which, through hydrogen bonding with the amides in the shell, restrict the fluidity of the shell material. This allows the softened shell material to effectively bond inorganic particles while remaining resistant to flow in its molten state at high temperatures, reducing the possibility of inorganic particles falling off. The large-particle binder exhibits good adhesive stability.

[0066] 4. In this application, deionized water is preferably used as a solvent to prepare the composite ceramic diaphragm, eliminating the need for organic solvents such as NMP, acetone, and ethanol. The deionized water, binder, ceramic particles, and additives are mixed and milled to prepare a slurry. The composite ceramic diaphragm is then prepared using a one-time coating process, which makes the coating process simpler, safer, and more environmentally friendly, and can significantly reduce costs. Attached Figure Description

[0067] Figure 1 The image shows a scanning electron microscope (SEM) image of the composite ceramic diaphragm used in Application Example 1. Detailed Implementation

[0068] The present application will be further described in detail below with reference to embodiments, comparative examples, application examples and application comparative examples.

[0069] Example 1

[0070] A non-fluorinated large-particle binder for lithium-ion battery ceramic separators is prepared according to the following steps:

[0071] Polyphthalamide is a custom-made product, and the particle size range of polyphthalamide microparticles is 60-500 nm; among them, the polyphthalamide selected is poly(p-phenylene terephthalamide) (poly(p-phenylene terephthalamide) grade 4402);

[0072] Weigh 5 kg of poly(p-phenylene terephthalamide) microparticles, 0.2 kg of emulsifier Tween-80, 10 kg of water, 5 kg of ethanol and 12 g of oil-soluble initiator azobisisoheptanenitrile, add them to the reaction vessel and stir and mix at a speed of 2000 rpm to obtain a pre-emulsion.

[0073] Nitrogen gas was introduced into the vacuum environment, and propylene monomer was introduced under the control of the solenoid valve. The pressure inside the reactor was maintained at 1.8 MPa, and the total amount of propylene introduced was controlled at 1 kg. The temperature was raised to 60°C and held for polymerization for 2 hours.

[0074] Weigh 4 kg of acrylamide monomer, add acrylamide monomer to the pre-emulsion under oil bath temperature control at 10℃, stir for 10 min, then raise the temperature to 60℃ and maintain the temperature for polymerization for 4 h.

[0075] After polymerization, 5 kg of glycidyl acrylate was injected, and the temperature was further increased to 60°C. The polymerization was maintained at this temperature for 4 hours. Toluene was added to the reaction solution, and the mixture was stirred for more than 6 hours. After filtration, a non-fluorine large-particle binder for lithium-ion battery ceramic separators was obtained. The filter cake was vacuum dried at 60°C for 24 hours.

[0076] Non-fluorinated large-particle binders with a particle size of 4–30 μm for lithium-ion battery ceramic separators were screened out.

[0077] Among them, the acrylamide monomer is methacrylamide; the glycidyl acrylate is glycidyl methacrylate;

[0078] After testing, the glass transition temperature of the shell was found to be 60.5℃.

[0079] Examples 2-9

[0080] A non-fluorinated large-particle binder for lithium-ion battery ceramic separators differs from Example 1 in that the total weight of propylene monomer, acrylamide monomer, and glycidyl acrylate in the preparation steps of the modified material is 10 kg, while the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate is different, as detailed below:

[0081] In Example 2, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.2:4:5; after testing, the glass transition temperature of the shell was 51.2℃.

[0082] In Example 3, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.5:4:5; after testing, the glass transition temperature of the shell was 42.6℃.

[0083] In Example 4, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 2:4:5; after testing, the glass transition temperature of the shell was 37.7°C.

[0084] In Example 5, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.2:5.8:5; after testing, the glass transition temperature of the shell was 69.8°C.

[0085] In Example 6, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.2:3.1:5; after testing, the glass transition temperature of the shell was 46.9°C.

[0086] In Example 7, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.2:2:5; after testing, the glass transition temperature of the shell was 35.0°C.

[0087] In Example 8, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.2:4:6.2; after testing, the glass transition temperature of the shell was 56.3°C.

[0088] In Example 9, the weight ratio of propylene monomer, acrylamide monomer, and glycidyl acrylate was 1.2:4:4.1; after testing, the glass transition temperature of the shell was 42.7°C.

[0089] Example 10

[0090] A non-fluorinated large-particle binder for lithium-ion battery ceramic separators differs from Example 2 in that the process parameters in the preparation method of the modified material are different, as detailed below:

[0091] The polymerization temperature of propylene monomer was controlled at 50℃, and the reaction was maintained at this temperature for 4 hours.

[0092] The polymerization temperature of acrylamide monomer was controlled at 50℃, and the reaction was maintained at this temperature for 5 hours.

[0093] Then add glycidyl acrylate, control the reaction temperature at 50℃, and keep the reaction at this temperature for 6 hours.

[0094] Example 11

[0095] A non-fluorinated large-particle binder for lithium-ion battery ceramic separators differs from Example 10 in that it uses a different type of acrylamide monomer, as detailed below:

[0096] In Example 11, the acrylamide monomer was 2-acrylamido-2-methylpropanesulfonic acid;

[0097] In Example 12, the acrylamide monomer was N-hydroxymethylacrylamide.

[0098] Example 13

[0099] A non-fluorinated large-particle binder for lithium-ion battery ceramic separators differs from that in Example 12 in that the particle size of the non-fluorinated large-particle binder for lithium-ion battery ceramic separators is different, as detailed below:

[0100] The non-fluorinated large-particle binder for lithium-ion battery ceramic separators prepared in Example 11 has a particle size of 10-15 μm.

[0101] Comparative Example

[0102] Comparative Example 1

[0103] An adhesive, which differs from Example 1 in that it is a small-particle adhesive with a particle size of ≤0.5μm.

[0104] Comparative Example 2

[0105] An adhesive, which differs from Example 1 in that it uses polyvinyl alcohol (average molecular weight Mw 100,000) and other materials instead of the modified materials.

[0106] Comparative Example 3

[0107] An adhesive differs from Example 1 in that it has a different shell material, which is a grafted and modified propylene monomer and acrylamide monomer in a weight ratio of 1:4.

[0108] The specific preparation method is as follows:

[0109] Weigh 5 kg of poly(p-phenylene terephthalamide) microparticles, 0.2 kg of emulsifier Tween-80, 10 kg of water, 5 kg of ethanol and 12 g of oil-soluble initiator azobisisoheptanenitrile, add them to the reaction vessel and stir and mix at a speed of 2000 rpm to obtain a pre-emulsion.

[0110] Nitrogen gas was introduced into the vacuum environment, and propylene monomer was introduced under the control of the solenoid valve. The pressure inside the reactor was maintained at 1.8 MPa, and the total amount of propylene introduced was controlled at 1 kg. The temperature was raised to 60°C and held for polymerization for 2 hours.

[0111] Weigh 4 kg of acrylamide monomer, add acrylamide monomer to the pre-emulsion under oil bath temperature control of 10℃, stir for 10 min; then heat to 60℃ and maintain the temperature for 4 h; add toluene to the reaction solution, stir for more than 6 h, filter to obtain non-fluorine large particle binder for lithium-ion battery ceramic separator, and vacuum dry the filter cake at 60℃ for 24 h.

[0112] The acrylamide monomer is methacrylamide;

[0113] Non-fluorinated large-particle binders with a particle size of 4–30 μm for lithium-ion battery ceramic separators were screened out.

[0114] Comparative Example 4

[0115] An adhesive differs from Example 1 in that it has a different shell material, which is a grafted and modified propylene monomer and glycidyl acrylate in a weight ratio of 1:5.

[0116] The specific preparation method is as follows:

[0117] Weigh 5 kg of poly(p-phenylene terephthalamide) microparticles, 0.2 kg of emulsifier Tween-80, 10 kg of water, 5 kg of ethanol and 12 g of oil-soluble initiator azobisisoheptanenitrile, add them to the reaction vessel and stir and mix at a speed of 2000 rpm to obtain a pre-emulsion.

[0118] Nitrogen gas was introduced into the vacuum environment, and propylene monomer was introduced under the control of the solenoid valve. The pressure inside the reactor was maintained at 1.8 MPa, and the total amount of propylene introduced was controlled at 1 kg. The temperature was raised to 60°C and held for polymerization for 2 hours.

[0119] Weigh 5 kg of glycidyl acrylate, add glycidyl acrylate to the pre-emulsion under oil bath temperature control of 10℃, stir for 10 min; then heat to 60℃ and keep warm for 4 h; add toluene to the reaction solution, stir for more than 6 h, filter to obtain non-fluorine large particle binder for lithium-ion battery ceramic separator, and vacuum dry the filter cake at 60℃ for 24 h.

[0120] Non-fluorinated large-particle binders with a particle size of 4–30 μm for lithium-ion battery ceramic separators were screened out.

[0121] Among them, glycidyl acrylate is glycidyl methacrylate;

[0122] The shell material prepared above was used in place of the modified material prepared in Example 1 by the same weight.

[0123] Comparative Example 5

[0124] An adhesive, which differs from Example 1 in that the shell material is different, and the shell material is grafted and modified from acrylamide monomer and glycidyl acrylate in a weight ratio of 4:5.

[0125] The specific preparation method is as follows:

[0126] Weigh 5 kg of poly(p-phenylene terephthalamide) microparticles, 0.2 kg of emulsifier Tween-80, 10 kg of water, 5 kg of ethanol and 12 g of oil-soluble initiator azobisisoheptanenitrile, add them to the reaction vessel and stir and mix at a speed of 2000 rpm to obtain a pre-emulsion.

[0127] Weigh 4 kg of acrylamide monomer, add acrylamide monomer to the pre-emulsion under oil bath temperature control at 10℃, stir for 10 min, then raise the temperature to 60℃ and maintain the temperature for polymerization for 4 h.

[0128] After polymerization, 5 kg of glycidyl acrylate was injected, and the temperature was further increased to 60°C. The polymerization was maintained at this temperature for 4 hours. Toluene was added to the reaction solution, and the mixture was stirred for more than 6 hours. After filtration, a non-fluorine large-particle binder for lithium-ion battery ceramic separators was obtained. The filter cake was vacuum dried at 60°C for 24 hours.

[0129] Among them, the acrylamide monomer is methacrylamide, and the glycidyl acrylate is glycidyl methacrylate;

[0130] The shell material prepared above was used in place of the modified material prepared in Example 1 by the same weight.

[0131] Comparative Example 6

[0132] An adhesive, differing from Example 1 in that it uses polystyrene microparticles (glass transition temperature 105°C) instead of polyphthalamide. Comparative Example 7

[0133] An adhesive, which differs from Example 1 in that it uses modified materials for extrusion granulation to produce adhesive particles with a particle size of 4 to 30 μm.

[0134] Application examples

[0135] Application Example 1

[0136] A composite ceramic diaphragm, the raw materials of which are as follows:

[0137] 700g of ceramic granules;

[0138] 30g of non-fluorinated large-particle binder for lithium-ion battery ceramic separators;

[0139] 40g of auxiliary adhesive;

[0140] Thickener 20g;

[0141] 300g of deionized water;

[0142] The main components of the ceramic particles are silicon dioxide and boehmite, and the particle size of the ceramic particles is 0.1μm to 2μm.

[0143] The non-fluorinated large-particle binder for lithium-ion battery ceramic separators is derived from Example 1;

[0144] The auxiliary binder is a water-based epoxy resin, brand: 0947A-53W / 0947B-100W;

[0145] The thickener is sodium carboxymethyl cellulose;

[0146] Prepare according to the following steps:

[0147] Step 1: The ceramic particles and the lithium-ion battery ceramic separator are respectively put into a sand mill for sand milling with a non-fluorine large particle binder. The sand mill speed is 1000 rpm and the sand milling time is 6 hours.

[0148] Ceramic particles, dispersant, thickener and half of deionized water are mixed to prepare a ceramic particle dispersion.

[0149] Step 2: Add non-fluorinated large particle binder for lithium-ion battery ceramic separators and the remaining deionized water to the ceramic particle dispersion, stir and mix to obtain ceramic separator slurry;

[0150] Step 3: Coat the ceramic composite slurry onto the base membrane, which is a PE base membrane, with a coating thickness of 5μm, and dry to obtain a composite ceramic diaphragm.

[0151] Application Example 2-13

[0152] A composite ceramic separator differs from Application Example 1 in that the source of the non-fluorinated large-particle binder used in the lithium-ion battery ceramic separator is different, as detailed below:

[0153] The non-fluorinated large-particle binder in Application Example 2 is derived from Example 2;

[0154] The non-fluorinated large-particle binder in Application Example 3 is derived from Example 3;

[0155] The non-fluorinated large-particle binder in Application Example 4 is derived from Example 4;

[0156] The non-fluorinated large-particle binder in Application Example 5 is derived from Example 5;

[0157] The non-fluorinated large-particle binder used in Example 6 is derived from Example 6;

[0158] The non-fluorinated large-particle binder in Application Example 7 is derived from Example 7;

[0159] The non-fluorinated large-particle binder used in Example 8 is derived from Example 8;

[0160] The non-fluorinated large-particle binder in Application Example 9 is derived from Example 9; the non-fluorinated large-particle binder in Application Example 10 is derived from Example 10;

[0161] The non-fluorinated large-particle binder used in Example 11 is derived from Example 11;

[0162] The non-fluorinated large-particle binder used in Example 12 is derived from Example 12;

[0163] The non-fluorinated large-particle binder used in Example 13 is derived from Example 13.

[0164] Application Example 14

[0165] A composite ceramic diaphragm differs from application example 13 in that the composite ceramic diaphragm also contains polyethylene glycol PEG-200 as a dispersant, with an addition amount of 50g.

[0166] Application Examples 15-17

[0167] A composite ceramic separator differs from application example 14 in that the milling process parameters for the ceramic particles and the non-fluorinated large-particle binder used in the lithium-ion battery ceramic separator are different, as detailed below:

[0168] In Application Example 15, the sand mill speed is 2000 rpm, and the sand milling time is 3 hours;

[0169] In Application Example 16, the sand mill speed is 4000 rpm, and the sand milling time is 2 hours;

[0170] In Application Example 17, the sand mill speed is 6000 rpm, and the sand milling time is 2 hours.

[0171] Application of comparative examples

[0172] Application Comparative Examples 1-7

[0173] A composite ceramic separator differs from Application Example 1 in that the source of the non-fluorinated large-particle binder used in the lithium-ion battery ceramic separator is different, as detailed below:

[0174] The non-fluorinated large-particle binder used in Comparative Example 1 was derived from Comparative Example 1;

[0175] The non-fluorinated large-particle binder used in Comparative Example 2 was derived from Comparative Example 2;

[0176] The non-fluorinated large-particle binder used in Comparative Example 3 was derived from Comparative Example 3;

[0177] The non-fluorinated large-particle binder used in Comparative Example 4 was derived from Comparative Example 4;

[0178] The non-fluorinated large-particle binder used in Comparative Example 5 was derived from Comparative Example 5;

[0179] The non-fluorinated large-particle binder used in Comparative Example 6 was derived from Comparative Example 6;

[0180] The non-fluorinated large-particle binder used in Comparative Example 7 was derived from Comparative Example 7.

[0181] Performance testing

[0182] The performance of ceramic diaphragms prepared for various applications and comparative examples was measured, including:

[0183] A. Physical and chemical properties

[0184] ①Porosity (%), the porosity was tested according to GB / T 21650.2-2008 "Determination of pore size distribution and porosity of solid materials by mercury porosimetry and gas adsorption method - Part 2: Analysis of mesopores and macropores by gas adsorption method".

[0185] ② Gurley permeability (Sec / 100ml): This measures the time required for 100mL of air to pass through a 1 square inch membrane at a pressure of 1.22kPa. The Gurley value is negatively correlated with gas permeability. Permeability is an indicator of a membrane's gas permeability and indirectly reflects ion permeability; higher permeability indicates stronger ion permeability. Permeability also reflects the tortuosity of the membrane's internal pores to some extent. When the membrane's porosity and thickness are fixed, higher permeability indicates less tortuosity. A tortuous membrane pore structure lengthens the path of lithium ions within the membrane, reducing their rate of travel between the positive and negative electrode materials. This increases the battery's internal resistance and makes it easier for lithium ion dendrites to grow, potentially puncturing the membrane and causing safety hazards. (A smaller tortuosity indicates better electrical performance of the membrane.)

[0186] ③Stability: The diaphragm was immersed in an electrolyte solution at 50°C for 48 hours. The diaphragm was then removed, washed, dried, and weighed. The change rate of diaphragm mass before and after immersion was compared.

[0187] ④ Liquid absorption performance:

[0188] The diaphragm was cut into square samples of appropriate size, flatly adhered to the glass plate sample stage, and its static electrolyte contact angle was tested in an air atmosphere using a JC2000D contact angle tester.

[0189] Square samples with dimensions of 2cm×2cm were taken from the diaphragm, dried, and their mass was recorded. The cut samples were then soaked in liquid electrolyte for 24 hours. The samples were then removed with tweezers and excess electrolyte was wiped off the surface of the fiber membrane with filter paper. The samples were weighed again, and the mass change rate before and after liquid absorption was calculated.

[0190] Mechanical properties:

[0191] ① Puncture strength (gf) is tested according to ASTM D3763-10 "Standard Test Method for High Speed ​​Puncture Properties of Plastics Using Load and Displacement Sensors".

[0192] ② Heat shrinkage rate of 130℃ / 1h (%) and heat shrinkage rate of 90℃ / 1h (%) were tested according to the test method of shrinkage rate in GB / T 13519-2016 "Polyethylene heat shrink film for packaging". The constant temperature was adjusted to 130℃ or 90℃ respectively, and the soaking time was adjusted to 1h.

[0193] ③ Peel force (N) after bonding with electrode material: Select a flat part of the diaphragm, cut each test sample into 15mm×200mm samples, and hot press the diaphragm sample and the positive electrode (lithium iron phosphate) at 1Mpa and 80℃ for 1min. Test the peel force at 180° according to GB / T8808-1988 "Peel Test Method for Flexible Composite Plastic Materials".

[0194] The separator was assembled to form an LCO / separator / Li half-cell sample.

[0195] Electrochemical performance:

[0196] ① Ionic conductivity (mS / cm) -2 The ionic conductivity was tested using the AC impedance method.

[0197] ② Battery cycle and rate performance test: Cycle stability test is conducted under 0.5C conditions, with a voltage range of 1.8 to 2.8V. Charge and discharge tests are conducted at the same rate until the battery's rated capacity reaches 80%. The number of cycles, the first effective discharge capacity, and the remaining capacity are recorded.

[0198] The electrolytes described above all have a composition of EC:DMC = 1:1 and 1M LiPF6.

[0199] For detailed detection data of Application Examples 1-17 and Comparative Examples 1-7, please refer to Table 1-3.

[0200] Table 1. Physicochemical property testing of application examples 1-17 and comparative examples 1-7

[0201]

[0202]

[0203] Table 2. Mechanical property testing of application examples 1-17 and comparative examples 1-7

[0204]

[0205]

[0206] Table 3. Electrochemical performance testing of application examples 1-15 and comparative examples 1-7

[0207]

[0208]

[0209] Based on the test data in Table 1-3, we can conclude that:

[0210] Comparative Example 1 used a small-particle binder. The peel force of the membrane prepared in Comparative Example 1 was significantly lower than that in Application Example 1, indicating that the large-particle binder can fully exert its bonding effect, enabling the composite membrane to bond well with the positive and negative electrode sheets, thus ensuring the bonding effect of the binder. Simultaneously, the membrane prepared with the large-particle binder also has higher porosity and air permeability, which can improve the electrolyte flow rate and enhance the electrochemical performance of the membrane.

[0211] In Comparative Example 2, traditional polyvinyl alcohol (PVA) was used as the shell material instead of the modified material. Although PVA can enhance the wettability of the separator, its own toughness is poor. Therefore, the swelling rate of the separator in Comparative Example 2 was actually reduced, cracks appeared on the ceramic coating layer of the separator, and the electrolyte easily crystallized in the large pores of the separator, resulting in a decrease in the battery cycle life and a significant reduction in battery life.

[0212] In Comparative Example 3, the shell material was selected as a propylene-acrylamide grafted modified polymer. The resulting binder swelled excessively, which led to a significant reduction in the number of membrane cycles and a short service life.

[0213] In Comparative Example 4, the shell material was selected as a propylene-glycidyl acrylate grafted modified polymer. The wettability of the resulting binder was significantly reduced, which led to a decrease in the liquid absorption performance of the diaphragm and a weakening of the electrochemical performance of the diaphragm.

[0214] Compared with Application Example 1, Application Comparative Examples 3 and 4 clearly show that the simultaneous use of acrylamide and glycidyl acrylate to modify propylene in Application Example 1 can significantly improve the liquid absorption capacity of the diaphragm, demonstrating a synergistic effect in this regard.

[0215] In Comparative Example 5, the shell material was selected as an acrylamide-glycidyl acrylate grafted modified polymer. Although the polar groups in acrylamide and acrylate increased and the hydrogen bonding was strong, the liquid absorption swelling rate of the shell material was reduced. The reason is that the strong hydrogen bonding between the acrylamide-acrylate grafted modified polymer makes it difficult for the membrane to swell, resulting in poor mechanical properties, easy membrane damage, poor electrochemical performance, and a significant reduction in the number of battery cycles.

[0216] In Comparative Example 6, polystyrene was chosen as the core material. Polystyrene contains rigid benzene rings with long chains, high crystallinity, and a high glass transition temperature. However, compared to Application Example 1, the electrochemical performance and stability of the diaphragm in Comparative Example 6 were inferior because there was no hydrogen bonding between the polystyrene and the modified material. In contrast, the core material of the large-particle binder in Application Example 1 was rich in polar functional groups—amides. These amides could restrict the flowability of the shell material through hydrogen bonding with the shell material, allowing the softened shell material to effectively bond inorganic particles while remaining resistant to flow in a molten state at high temperatures, thus reducing the possibility of inorganic particles falling off. The large-particle binder exhibited better adhesive stability. Furthermore, the large-particle binder and the modified material, as well as the polyphthalamide, were rich in polar functional groups, allowing the electrolyte to pass through the pores of the large-particle binder without affecting the electrolyte flow due to the particle size.

[0217] In Comparative Example 7, only the modified material was used as a binder. The binder did not have a core-shell structure. Although the hyperbranched modified polyacrylic acid could improve the electrochemical performance of the separator in the short term, the number of cycles was very small. After only 15 cycles, it dropped to 80% of the rated capacity of the battery. This shows that the double core-shell structure is beneficial to increase the number of charge-discharge cycles of the battery and extend the battery's service life.

[0218] Therefore, in Application Example 1, the use of a specific structure and core-shell raw materials to prepare a large-particle binder can significantly improve the overall performance of the battery separator.

[0219] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A non-fluorine large particle binder for a lithium ion battery ceramic separator, characterized by: The polyphthalamide is used as a core, and a modified material is used as a shell, wherein the modified material is grafted and modified by propylene monomer, acrylamide monomer and glycidyl acrylate in a weight ratio of (1.2-1.5):(5.1-5.4):(3.5-4) in sequence; The glass transition temperature Tg1 of the polyphthalamide is greater than or equal to 220 ℃, and the glass transition temperature Tg2 of the modified material is 35-70 ℃. The particle size of the non-fluorine large-particle binder for the lithium ion battery ceramic separator is 4-30 μm.

2. The non-fluorine based large particle binder for lithium ion battery ceramic separator according to claim 1, characterized in that: The preparation method of the non-fluorine large-particle binder for the lithium ion battery ceramic separator comprises the following steps: The polyphthalamide particles are blended with an emulsifier, water, ethanol and an oil-soluble initiator to obtain a pre-emulsion; The propylene monomer is introduced into the pre-emulsion, and the temperature is increased to 50-60 ℃, and the reaction is maintained for 2-4 h; Then the acrylamide monomer is added, and the reaction temperature is controlled at 50-60 ℃, and the reaction is maintained for 4-5 h; Finally, the glycidyl acrylate is added, and the reaction temperature is controlled at 50-60 ℃, and the reaction is maintained for 4-6 h, and the modified material is obtained by purification.

3. The non-fluorine based large particle binder for lithium ion battery ceramic separator according to claim 1, characterized in that: The acrylamide monomer is N-hydroxymethyl acrylamide.

4. The non-fluorinated macro-particle binder for lithium-ion battery ceramic separator according to claim 1, characterized in that: The particle size of the non-fluorine large-particle binder for the lithium ion battery ceramic separator is 10-15 μm.

5. A composite ceramic separator, characterized by, The raw materials include the following components by weight: ceramic particles 30-70 parts; non-fluorine large-particle binder for the lithium ion battery ceramic separator 3-12 parts; auxiliary binder 4-8 parts; dispersant 0-5 parts; thickening agent 2-8 parts; deionized water 30-150 parts; The non-fluorine large-particle binder for the lithium ion battery ceramic separator is the non-fluorine large-particle binder for the lithium ion battery ceramic separator according to any one of claims 1-4.

6. A composite ceramic separator according to claim 5, wherein: The ceramic particles and the non-fluorine large-particle binder for the lithium ion battery ceramic separator are subjected to sand milling treatment, and the sand milling machine rotates at a speed of 2000-4000 rpm in the sand milling treatment step, and the sand milling is performed for 2-3 h.

7. The method for preparing the composite ceramic diaphragm according to claim 5, characterized in that: The following steps are included: Step 1: mixing the ceramic particles, the dispersant, the thickening agent and part of the deionized water to prepare a ceramic particle dispersion liquid; Step 2: adding the non-fluorine large-particle binder for the lithium ion battery ceramic separator and the remaining deionized water to the ceramic particle dispersion liquid, stirring and mixing to obtain a ceramic separator slurry; Step 3: coating the ceramic separator slurry on a base film, and drying to obtain a composite ceramic separator.

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