Preparation method of water-soluble bio-based aramid / ceramic coated battery separator

Abstract

The present invention belongs to the technical field of polymer compound compositions for battery separators and discloses a method for preparing a water-soluble bio-based aramid / ceramic coated battery separator. The method comprises a coating process in which a water-soluble bio-based aramid is mixed with a ceramic material, aluminum sol, and an additive to prepare an aqueous slurry, which is then coated on one or both sides of a base membrane to obtain the desired separator. The addition of a water-soluble bio-based aramid component to the coating slurry improves the separator's high-temperature tolerance, electrolyte wettability, and coating adhesion. The addition of an aluminum sol binder component in conjunction with the water-soluble bio-based aramid can mitigate coating pore blockage and improve separator air permeability. The separator of the present invention is suitable for lithium-ion batteries, sodium-ion batteries, semi-solid-state batteries, and the like, and has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer compound compositions for battery separators, and in particular to a method for preparing a water-soluble bio-based aramid / ceramic coated battery separator. Background Art

[0002] As lithium-ion batteries develop towards higher energy density, higher capacity, and higher reliability, traditional polyolefin separators are unable to meet these demands due to their poor heat resistance and insufficient affinity with the electrolyte. To this end, academia and industry have developed separator coating technologies. One common method is to apply an inorganic ceramic coating (such as Al2O3, SiO2, or boehmite) to the surface of a polyolefin base membrane. While this improves high-temperature resistance and liquid affinity, the ceramic particles suffer from poor bonding between the base membrane and easy detachment. While adding a binder can enhance bonding, it can easily clog the pores of the separator, resulting in decreased permeability. Another option is to apply an organic coating of polyvinylidene fluoride (PVDF), but its hydrophobicity relies on an oil-based coating process, which carries the problems of large amounts of organic solvents, high costs, and environmental pollution.

[0003] In recent years, petroleum-based aramid (such as para-aramid PPTA) has been introduced into the field of diaphragm coatings due to its high strength, high modulus, and excellent thermal stability (decomposition temperature >500°C). Studies have shown that aramid-coated diaphragms can maintain structural stability at high temperatures, significantly reduce thermal shrinkage (shrinkage <5% at 180°C), and modification with silane coupling agents can improve the interfacial bonding between the coating and the base membrane, avoiding the problem of powder shedding in the ceramic coating. However, the promotion of petroleum-based aramid is restricted by multiple factors: the synthesis of its production monomers (such as terephthaloyl chloride) relies on petroleum raw materials; aramid fibers are difficult to crush and disperse due to their high strength and high modulus properties, requiring special equipment (such as PFI refiners) for processing; aramid has a smooth surface and lacks active groups, so its interfacial bonding with the binder relies on physical interactions, making interfacial delamination prone to occur during long-term circulation.

[0004] To reduce dependence on petroleum resources, bio-based aramid (using biomass-derived monomers to replace petroleum-based raw materials) has been introduced into the diaphragm coating industry. For example, aramid using bio-based p-phenylenediamine or furandicarboxylic acid as monomers is green and biodegradable. Preliminary experiments have shown that bio-based aramid coatings are similar to petroleum-based aramid in terms of heat resistance (decomposition temperature >400°C) and mechanical strength. Furthermore, they have richer surface polar groups and better electrolyte compatibility, and coating can enhance chemical bonding with the base membrane. However, the water-based bio-based aramid currently used mainly consists of fibers and particles. Their dispersion in water is unstable and they fail to form a uniform slurry after standing. Summary of the Invention

[0005] In order to solve the problems existing in the existing aramid coated membrane technology, such as large air permeability increase of the coated membrane, poor adhesion between the composite coating and the base membrane, insufficient wettability, and incompatibility and easy agglomeration of existing bio-based aramid particles in the slurry, the present invention proposes a preparation method of a water-soluble bio-based aramid / ceramic coated battery membrane.

[0006] To achieve the purpose, the present invention adopts the following technical solutions:

[0007] The present invention first provides a method for preparing a water-soluble bio-based aramid / ceramic coated battery separator, which comprises: mixing water-soluble bio-based aramid with ceramic materials, aluminum sol and additives to prepare an aqueous slurry, and coating the aqueous slurry on one or both sides of a base film through a coating process to obtain a water-soluble bio-based aramid / ceramic coated battery separator.

[0008] Furthermore, based on dry weight, the mass percentages of the raw materials in the aqueous slurry are: 8-11 wt% of water-soluble bio-based aramid, 85-87 wt% of ceramic material, 0.1-0.5 wt% of dispersant, 1-4 wt% of aluminum sol, and 0.1-1.0 wt% of wetting agent.

[0009] Preferably, the water-soluble bio-based aramid is prepared with reference to patent CN118667151A: by introducing a polyamic acid segment into the bio-based aramid main chain containing a furan ring, and then salifying to form a strong hydrophilic segment, a water-soluble bio-based aramid is obtained, and a water-based coating of aramid is achieved. The prepared bio-based aramid material has good water solubility and coating adhesion, and can be compounded with aluminum sol to play a synergistic role and used as an adhesive in the battery separator formulation. In addition, the unique polar groups of the bio-based aramid material have similar polarity and structure to the main organic solvent molecules of the electrolyte, which will interact more strongly with the electrolyte and have a better wetting effect. Therefore, the water-soluble bio-based aramid / ceramic coated battery separator prepared by mixing with ceramic particles and the like exhibits excellent mechanical strength, thermal shrinkage stability and electrolyte wetting properties.

[0010] Preferably, the base film is at least one of a PP membrane, a PE membrane, a non-woven fabric and a fiber membrane.

[0011] Preferably, the ceramic material is at least one of boehmite, alumina, silicon oxide and titanium oxide, and most preferably boehmite; the particle size of the ceramic material is 100-1000 nm.

[0012] Preferably, the dispersant is at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, acrylate and polyurethane, and sodium carboxymethyl cellulose is most preferred.

[0013] Preferably, the wetting agent includes at least one of polyether-modified dimethylsiloxane, polyoxyethylene ether, sodium lauryl sulfonate, polyether-modified silicone and modified succinic acid, and most preferably polyoxyethylene ether.

[0014] The chemical formula of the aluminum sol binder is a(Al2O3·nH2O)·bHx·cH2O, wherein: Al2O3·nH2O is hydrated aluminum oxide, H x It is a peptizing agent, with coefficients of b<a, c, n. Water-soluble bio-based aramid contains abundant polar groups (such as hydroxyl, amino, carboxyl, etc.), which can react with aluminum ions (Al 3+ ) or hydroxyaluminum complexes (such as [Al(OH)2(H2O)4] + ) to form a dynamic cross-linked network. The Lewis acidity of aluminum ions binds to the carboxyl groups of aramid through chelation, enhancing interfacial bonding. Hydrogen bonds are formed between the hydroxyl groups of the aluminum sol and the aramid, further stabilizing the composite structure. Secondly, the aluminum sol can be embedded as a nanofiller within the three-dimensional network of bio-based aramid, forming an "organic-inorganic" bicontinuous structure. The aluminum sol's nanoparticles fill the pores of the aramid through in-situ cross-linking, forming a hierarchical pore structure that both enhances mechanical strength and maintains the material's liquid permeability.

[0015] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0016] The water-soluble bio-based aramid / ceramic coated battery separator prepared by this invention exhibits uniform pores, an air permeability of 100-200 s / 100 cc, an electrolyte (EC:PC:DEC = 1:1:1 + 1 M LiPF6) wetting rate of 80-100 mm / 60 s, a thermal shrinkage of <2% in the MD direction and <2% in the TD direction within 1 hour at 150°C, and a coating peel strength of 110-140 N / m. The addition of a water-soluble bio-based aramid component to the coating slurry improves the coated separator's high-temperature tolerance, electrolyte wettability, and coating adhesion. The addition of an aluminum sol binder component in conjunction with the water-soluble bio-based aramid reduces coating pore blockage and improves membrane air permeability. The separator of this invention is suitable for lithium-ion batteries, sodium-ion batteries, semi-solid-state batteries, and other applications, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is the SEM surface image of the water-soluble bio-based aramid / ceramic coated battery separator prepared in Example 1. DETAILED DESCRIPTION

[0019] To more clearly illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] Example 1

[0021] This embodiment provides a method for preparing a water-soluble bio-based aramid / ceramic coated battery separator, which specifically includes the following steps:

[0022] Step 1: Weigh 21.43 kg of boehmite aqueous slurry (solid content 43%, particle size D 50 =0.34 μm), 22.26 kg of water-soluble bio-aramid (5% solid content), 1.391 kg of aluminum sol (20% solid content), 1.21 kg of sodium carboxymethyl cellulose dispersant (1.7% solid content), and 0.05 kg of polyoxyethylene ether wetting agent (100% solid content) were added to a stirring tank (the dry weight ratio of aramid to aluminum sol was 4:1). Each addition was stirred for 20 minutes at an orbital speed of 25 rpm, an autorotational speed of 2000 rpm, and a temperature of 25°C to ensure thorough dispersion and form a milky white, impurity-free slurry.

[0023] Step 2: Coating was performed on a rod coater with a gap of 1-3 μm. The coating base film was a 7 μm commercial polyethylene separator. The film was then dried in a forced air oven at 60°C for 10 minutes to obtain a water-soluble bio-based aramid / ceramic coated battery separator.

[0024] Example 2

[0025] The preparation method and operating conditions of the coated diaphragm in this example are basically the same as those in Example 1, except that the mass of the added water-soluble bio-based aramid (solid content of 5%) is 20.87 kg, and the mass of the aluminum sol (solid content of 20%) is 1.74 kg (the dry weight ratio of aramid:aluminum sol is 3:1).

[0026] Example 3

[0027] The preparation method and operating conditions of the coated diaphragm in this example are basically the same as those in Example 1, with the only difference being that the mass of the added water-soluble bio-based aramid (solid content of 5%) is 23.18 kg, and the mass of the aluminum sol (solid content of 20%) is 1.16 kg (the dry weight ratio of aramid to aluminum sol is 5:1).

[0028] Example 4

[0029] The preparation method and operating conditions of the coated diaphragm in this example are basically the same as those in Example 1, except that the mass of the added water-soluble bio-based aramid (solid content of 5%) is 23.85 kg, and the mass of the aluminum sol (solid content of 20%) is 0.99 kg (the dry weight ratio of aramid:aluminum sol is 6:1).

[0030] Comparative Example 1

[0031] The preparation method and operating conditions of the coated diaphragm in this comparative example are basically the same as those in Example 1, with the only difference being that 1.391 kg of aluminum sol (solid content of 20%) is replaced by 1.391 kg of styrene-butadiene latex binder (solid content of 20%, dry weight ratio of aramid:styrene-butadiene latex of 4:1).

[0032] Comparative Example 2

[0033] The preparation method and operating conditions of the coated diaphragm in this comparative example are basically the same as those in Example 1, except that 1.391 kg of aluminum sol (solid content of 20%) is replaced by 1.391 kg of polyacrylate adhesive (solid content of 20%, dry weight ratio of aramid:polyacrylate is 4:1).

[0034] Comparative Example 3

[0035] The preparation method and operating conditions of the coated diaphragm in this comparative example are basically the same as those in Example 1, with the only difference being that 1.391 kg of aluminum sol (solid content of 20%) is replaced by 1.391 kg of polyacrylonitrile binder (solid content of 20%, dry weight ratio of aramid:polyacrylonitrile of 4:1).

[0036] Comparative Example 4

[0037] The preparation method and operating conditions of the coated diaphragm of this comparative example are basically the same as those of Example 1, with the only difference being that the addition amount of the aluminum sol component is 0.

[0038] Comparative Example 5

[0039] The preparation method and operating conditions of the coated diaphragm in this comparative example are basically the same as those in Example 1, with the only difference being that the mass of the added water-soluble bio-based aramid (solid content of 5%) is 18.54 kg, and the mass of the aluminum sol (solid content of 20%) is 2.32 kg (the dry weight ratio of aramid:aluminum sol is 2:1).

[0040] Comparative Example 6

[0041] The preparation method and operating conditions of the coated diaphragm in this comparative example are basically the same as those in Example 1, except that the mass of the added water-soluble bio-based aramid (solid content of 5%) is 9.27 kg, and the mass of the aluminum sol (solid content of 20%) is 4.64 kg (the dry weight ratio of aramid:aluminum sol is 1:2).

[0042] The membranes obtained in each embodiment and comparative example were tested. The specific testing instruments and methods are shown in Table 1:

[0043] Table 1

[0044]

[0045] The performance comparison of the membranes obtained in the examples and the comparative examples is shown in Table 2.

[0046] Table 2

[0047]

[0048] From the data in Table 2, we can see that:

[0049] Compared to Comparative Examples 1-3, which used other adhesives, the membranes of Examples 1-4 exhibited a lower increase in air permeability compared to the PE-based membrane, and showed less noticeable pore blocking. This indicates that the combination of aluminum sol and water-soluble bio-based aramid effectively reduces the increase in air permeability of the coated membrane compared to other adhesives. Furthermore, the membranes obtained in Examples 1-4 exhibited lower thermal shrinkage and superior heat resistance compared to other adhesives.

[0050] Compared with Comparative Example 6, the peeling strength between the diaphragm obtained in Examples 1-4 and the coating is high, and the coating is not easy to fall off, which indicates that too high a proportion of aluminum sol added will weaken the bonding force between the coating and the base film.

[0051] Comparing the 150°C / 1h thermal shrinkage of the separators obtained in Examples 1-4 with those in Comparative Examples 4-6 shows that the thermal shrinkage of the separators obtained in Examples 1-4 is less than 5%, which is beneficial for the safety of lithium-ion batteries at high temperatures. Combining Comparative Examples 4 and 6 shows that the water-soluble bio-based aramid inherently possesses a certain degree of adhesion to the base film.

[0052] All numerical specifications herein (e.g., temperatures, times, concentrations, and weights, including ranges for each thereof) are generally approximate values that may be modified (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about."

[0053] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative work falls within the scope of protection of the present invention.

Claims

1. A method for preparing a water-soluble bio-based aramid / ceramic coated battery separator, characterized in that: Water-soluble bio-based aramid is prepared by introducing polyamic acid segments into the main chain of bio-based aramid containing furan rings, followed by salt formation to form strongly hydrophilic segments; the water-soluble bio-based aramid is mixed with ceramic materials, aluminum sol and additives to prepare an aqueous slurry; the aqueous slurry is coated on one or both sides of a base film through a coating process to obtain a water-soluble bio-based aramid / ceramic coated battery separator; Calculated by dry weight, the mass percentages of the raw materials in the aqueous slurry are: 8-11 wt% of water-soluble bio-based aramid, 85-87 wt% of ceramic material, 0.1-0.5 wt% of dispersant, 1-4 wt% of aluminum sol, and 0.1-1.0 wt% of wetting agent; the dry weight ratio of the water-soluble bio-based aramid to the aluminum sol is 3-6:

1.

2. The method for preparing a water-soluble bio-based aramid / ceramic coated battery separator according to claim 1, characterized in that: The base film is at least one of a PP diaphragm, a PE diaphragm, a non-woven fabric and a fiber diaphragm.

3. The method for preparing a water-soluble bio-based aramid / ceramic coated battery separator according to claim 1, characterized in that: The ceramic material is at least one of boehmite, aluminum oxide, silicon oxide and titanium oxide; and the particle size of the ceramic material is 100-1000 nm.

4. The method for preparing a water-soluble bio-based aramid / ceramic coated battery separator according to claim 1, characterized in that: The dispersant is at least one of polyvinyl alcohol, sodium carboxymethyl cellulose, acrylate and polyurethane.

5. The method for preparing a water-soluble bio-based aramid / ceramic coated battery separator according to claim 1, characterized in that: The wetting agent includes at least one of polyether-modified dimethylsiloxane, polyoxyethylene ether, sodium lauryl sulfonate, polyether-modified silicone and modified succinic acid.

6. A water-soluble bio-based aramid / ceramic coated battery separator prepared by the preparation method according to any one of claims 1 to 5.

7. A battery, characterized in that: The battery comprising the separator according to claim 6 is a primary battery or a secondary battery.

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