A battery separator containing pyridine-based heterocyclic aramid fibers, its preparation method and application

Abstract

This invention relates to the field of battery separator technology, specifically to a battery separator containing pyridine-based heterocyclic aramid, its preparation method, and its applications. The preparation method includes the following steps: S1, mixing a pyridine-based heterocyclic aramid polymer solution, nano-ceramic materials, and additives to obtain a coating slurry; S2, applying the coating slurry from S1 to at least one surface of a base film, followed by a coagulation bath and drying; the pyridine-based heterocyclic aramid has a specific logarithmic viscosity of 2.0~3.5 dL / g. This battery separator contains pyridine-based heterocyclic aramid and possesses good thermal properties and peel strength, improving the safety performance of lithium batteries and extending their service life. Furthermore, the preparation method of this battery separator is simple to operate, operates under mild conditions, is green and efficient, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a battery separator containing pyridine-based heterocyclic aramid, its preparation method, and its application. Background Technology

[0002] As one of the core components of lithium-ion batteries, the battery separator plays a crucial role in separating the positive and negative electrodes to prevent short circuits and allowing lithium ions to pass freely to ensure ion conduction. Its performance directly affects the battery's safety, cycle life, and rate performance. With the rapid development of the new energy industry, power batteries are placing higher demands on the comprehensive performance of separators, especially in terms of high-temperature stability, mechanical strength, resistance to electrolyte corrosion, and dimensional stability.

[0003] Currently, commercially available battery separators are mainly made of polyolefin materials (such as polyethylene PE and polypropylene PP). These materials have good ion permeability and mechanical processability, but they have obvious shortcomings: poor thermal stability. During battery charging and discharging, they are prone to thermal shrinkage due to local overheating, which may even lead to separator rupture and short circuit between the positive and negative electrodes, and in severe cases, thermal runaway. At the same time, polyolefin materials have limited chemical inertness, and long-term contact with electrolyte may cause swelling or aging, affecting the cycle stability of the battery.

[0004] To address these issues, researchers have improved performance through coating modifications (such as coating with ceramics or aramid fibers) or by developing novel polymer membrane materials. Among these, aramid fibers, due to their excellent thermal stability (decomposition temperature exceeding 500°C), high strength, and chemical resistance, have become ideal membrane substrates or coating materials. While traditional aramid fibers (such as poly(p-phenylene terephthalamide)) can significantly improve the high-temperature resistance and mechanical properties of membranes, their excessively rigid molecular chains and dense intermolecular hydrogen bonds result in extremely poor solubility, making it difficult to prepare thin films or coating solutions through solution processing, thus limiting their large-scale application in the membrane field.

[0005] To address the processing challenges of traditional aramid fibers, research on heterocyclic aramid fibers has gradually gained attention. By introducing heterocyclic structures into the molecular chain, intermolecular forces and chain segment flexibility can be adjusted, improving the solubility of the material. Among them, the pyridyl group, as a heterocyclic group with strong polarity and conjugated structure, can not only maintain the rigidity and thermal stability of the molecular chain through the conjugation effect, but also make its electron cloud susceptible to deformation due to solvent influence due to the large π-conjugated system of pyridyl. The polar nitrogen atom provides hydrogen bond acceptor sites, enhancing the interaction with the solvent, thereby improving the solubility and processability of the material while maintaining excellent thermodynamic properties.

[0006] However, existing heterocyclic aramids still face bottlenecks in battery separator applications: most materials have low molecular weights, resulting in insufficient mechanical strength in the manufactured separators, making it difficult to withstand the mechanical stress during battery assembly and charging / discharging; some highly soluble heterocyclic aramids, due to their excessively high heterocyclic ratio, sacrifice thermal stability and cannot meet the requirements of power batteries operating in high-temperature environments. Therefore, developing a pyridine-based heterocyclic aramid that combines high molecular weight, excellent thermal stability, high strength, and good solubility, and applying it to battery separators to improve their overall performance, has become an important research direction in the current lithium-ion battery field. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of difficult processing and low production efficiency of aramid-coated separators in the prior art, and to provide a battery separator containing pyridine-based heterocyclic aramid, its preparation method and application. This battery separator contains pyridine-based heterocyclic aramid and has good thermal properties and peel strength, which improves the safety performance of lithium batteries and extends their service life. At the same time, the preparation method of this battery separator is simple to operate, mild, green and efficient, and has broad application prospects.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a battery separator, the method comprising the following steps:

[0009] S1. A coating slurry is prepared by mixing pyridyl heterocyclic aramid polymer liquid, nano-ceramic material and additives;

[0010] S2. Apply the coating slurry described in S1 to at least one surface of the base film, then place it in a coagulation bath and dry.

[0011] In S1, the structural formula of the pyridyl heterocyclic aramid is shown in Formula I and Formula II.

[0012] ,

[0013] ;

[0014] Where m≥10, n≥10, and m and n are both integers;

[0015] The specific logarithmic viscosity of the pyridyl heterocyclic aramid is 2.0~3.5 dL / g.

[0016] Furthermore, in S1, the preparation method of the pyridyl heterocyclic aramid polymer liquid includes: in the presence of a solvent, in an inert atmosphere, first mixing Candida lipase and diformyl chloride monomer, second mixing with diamine monomer, and neutralization reaction with inorganic base to obtain pyridyl heterocyclic aramid polymer liquid.

[0017] Furthermore, the solvent is selected from one or more of N,N-dimethylacetamide, N-methylpyridinone, N-ethylpyridinone, N,N-dimethylformamide, and sulfolane.

[0018] Furthermore, the inert atmosphere is a nitrogen atmosphere and / or an argon atmosphere.

[0019] Furthermore, the dicarboxylic acid chloride monomer is a pyridine dicarboxylic acid chloride monomer or a comonomer composed of pyridine dicarboxylic acid chloride and aromatic dicarboxylic acid chloride.

[0020] Furthermore, the diamine monomer is an aromatic diamine.

[0021] Furthermore, the inorganic base is lithium hydroxide and / or sodium hydroxide.

[0022] Furthermore, the pyridine dicarboxylate chloride is 2,6-pyridine dicarboxylate chloride and / or 2,5-pyridine dicarboxylate chloride.

[0023] Furthermore, the aromatic dicarboxylic chloride is terephthaloyl chloride and / or isophthaloyl chloride.

[0024] Furthermore, the aromatic diamine is p-phenylenediamine and / or m-phenylenediamine.

[0025] Furthermore, the molar ratio of the diformyl chloride monomer to the diamine monomer is 0.8~1.3:1.

[0026] Furthermore, the mass fraction of the solvent in the pyridyl heterocyclic aramid polymerization solution is 50-80%.

[0027] Furthermore, the mass ratio of the diamine monomer to Candida lipase is 1:0.015~0.058.

[0028] Furthermore, the molar ratio of the inorganic base to the diamine monomer is 1.6 to 2.6:1.

[0029] Furthermore, in S1, the nano-ceramic material is selected from one or more of alumina, magnesium oxide, aluminum hydroxide, and silicon dioxide.

[0030] Furthermore, in S1, the particle size of the nano-ceramic material is 10~1000nm.

[0031] Furthermore, in S1, the auxiliary agent is selected from one or more of ethanol, dimethyl carbonate, and PVDF.

[0032] Furthermore, in S2, the material of the base film is selected from one of polyethylene terephthalate nonwoven fabric, nylon nonwoven fabric, polypropylene (PP), and polyethylene (PE).

[0033] Furthermore, in S1, the mass ratio of the pyridyl heterocyclic aramid polymer liquid to the nano-ceramic material is 1:0.015~0.25.

[0034] Furthermore, in S1, the mass ratio of the nano-ceramic material to the additive is 1:0.106~0.605.

[0035] Furthermore, in S1, the mixing conditions include: a stirring rate of 150~300 rpm, a temperature of 15~30℃, and a time of 1~3h.

[0036] Furthermore, in S2, the conditions of the coagulation bath include: a temperature of 20~30℃, a time of 1~10min, and a mass ratio of organic solvent to water of 1:0.5~1.

[0037] Furthermore, the organic solvent is selected from one or more of N,N-dimethylacetamide, N-methylpyridinone, N,N-dimethylformamide, trifluoroethanol, and tert-butanol.

[0038] Furthermore, the drying conditions include a temperature of 20~90℃ and a time of 1~2h.

[0039] In a second aspect, the present invention provides a battery separator, which is prepared according to the preparation method described in the first aspect.

[0040] Thirdly, the present invention provides a lithium battery, the lithium battery comprising: a positive electrode material, a negative electrode material, an electrolyte, and a battery separator, wherein,

[0041] The battery separator is the battery separator described in the second aspect.

[0042] In the above technical solution, the battery separator of the present invention creatively incorporates pyridine-based heterocyclic aramid. Due to the good solubility of pyridine-based heterocyclic aramid, less solvent is used in the coating process, resulting in a high product qualification rate and low process cost. Furthermore, the thermal performance of the battery separator is greatly improved; at 130°C, the thermal shrinkage is as low as 1.2%; at 150°C, the thermal shrinkage is as low as 3.1%. Simultaneously, the coating adheres well to the base film, the ceramic on the surface does not shed powder, and the peel strength is as high as 131 N / m. Lithium batteries made using the battery separator of the present invention possess excellent safety performance and a longer lifespan.

[0043] Furthermore, the pyridine-based heterocyclic aramid used in the battery separator of this invention is synthesized using Candida albicans lipase catalysis, resulting in high molecular weight, a green and environmentally friendly reaction process, no metal residue in the catalyst, and no impact on polymer performance. In addition, the catalytic reaction can be carried out at room temperature without consuming additional energy, resulting in low production costs. The obtained pyridine-based heterocyclic aramid has high stability and can be stored for a long time, improving the processability of the material and showing broad application prospects.

[0044] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0045] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0046] Figure 1 The NMR spectrum of the pyridyl heterocyclic aramid prepared in Example 1 is shown. Detailed Implementation

[0047] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0048] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0049] In a first aspect, the present invention provides a method for preparing a battery separator, the method comprising the following steps:

[0050] S1. A coating slurry is prepared by mixing pyridyl heterocyclic aramid polymer liquid, nano-ceramic material and additives;

[0051] S2. Apply the coating slurry described in S1 to at least one surface of the base film, then place it in a coagulation bath and dry.

[0052] In S1, the structural formula of the pyridyl heterocyclic aramid is shown in Formula I and Formula II.

[0053] ,

[0054] ;

[0055] Where m≥10, n≥10, and m and n are both integers;

[0056] The specific logarithmic viscosity of the pyridyl heterocyclic aramid is 2.0~3.5 dL / g.

[0057] The battery separator of this invention creatively incorporates pyridine-based heterocyclic aramid. Due to the good solubility of pyridine-based heterocyclic aramid, less solvent is used in the coating process, resulting in a high product qualification rate and low process cost. It also greatly improves the thermal performance of the battery separator. At a temperature of 130°C, the thermal shrinkage is as low as 1.2%; at a temperature of 150°C, the thermal shrinkage is as low as 3.1%. At the same time, the coating has good adhesion to the base film, the ceramic on the surface does not shed powder, and the peel strength is as high as 131 N / m.

[0058] In a preferred embodiment of the present invention, in S1, the preparation method of the pyridyl heterocyclic aramid polymer liquid includes: in the presence of a solvent, in an inert atmosphere, first mixing Candida lipase and diformyl chloride monomer, second mixing with diamine monomer, and neutralization reaction with inorganic base to obtain pyridyl heterocyclic aramid polymer liquid.

[0059] In a preferred embodiment of the present invention, the solvent is selected from one or more of N,N-dimethylacetamide, N-methylpyridinone, N-ethylpyridinone, N,N-dimethylformamide and sulfolane.

[0060] In a preferred embodiment of the present invention, the inert atmosphere is a nitrogen atmosphere and / or an argon atmosphere.

[0061] In a preferred embodiment of the present invention, the dicarboxylic chloride monomer is a pyridine dicarboxylic chloride monomer or a comonomer composed of pyridine dicarboxylic chloride and aromatic dicarboxylic chloride.

[0062] In a preferred embodiment of the present invention, the diamine monomer is an aromatic diamine.

[0063] In a preferred embodiment of the present invention, the inorganic base is lithium hydroxide and / or sodium hydroxide.

[0064] In a preferred embodiment of the present invention, the pyridine dicarboxylate chloride is 2,6-pyridine dicarboxylate chloride and / or 2,5-pyridine dicarboxylate chloride.

[0065] In a preferred embodiment of the present invention, the aromatic dicarboxylic chloride is terephthaloyl chloride and / or isophthaloyl chloride.

[0066] In a preferred embodiment of the present invention, the aromatic diamine is p-phenylenediamine and / or m-phenylenediamine.

[0067] In a preferred embodiment of the present invention, the molar ratio of the diformyl chloride monomer to the diamine monomer is 0.8 to 1.3:1, preferably 1:1.

[0068] In a preferred embodiment of the present invention, the mass fraction of the solvent in the pyridyl heterocyclic aramid polymerization solution is 50-80%.

[0069] In a preferred embodiment of the present invention, in order to ensure the degree of polymerization of the pyridyl heterocyclic aramid, the mass ratio of the diamine monomer to Candida lipase is 1:0.015~0.058, for example, it can be 1:0.015, 1:0.020, 1:0.025, 1:0.030, 1:0.035, 1:0.040, 1:0.045, 1:0.050 and 1:0.055.

[0070] In a preferred embodiment of the present invention, in order to adjust the pH of the polymerization solution, the molar ratio of the inorganic base to the diamine monomer is 1.6 to 2.6:1, for example, it can be 1.6:1, 1.8:1, 1.9:1, 2.0:1, 2.2:1, 2.5:1, 2.55:1 and 2.4:1.

[0071] In a preferred embodiment of the present invention, in S1, the nano-ceramic material is selected from one or more of alumina, magnesium oxide, aluminum hydroxide, and silicon dioxide.

[0072] In a preferred embodiment of the present invention, in order to ensure the mechanical properties and electrical conductivity of the battery separator, the particle size of the nano-ceramic material is 10~1000nm, for example, it can be 10nm, 100nm, 200nm, 300nm, 500nm, 700nm, or 850nm.

[0073] In a preferred embodiment of the present invention, in order to make the coating slurry bond more firmly to the base film and give the battery better mechanical properties, the additive is selected from one or more of ethanol, dimethyl carbonate and PVDF.

[0074] In a preferred embodiment of the present invention, in S2, the material of the base film is selected from one of polyethylene terephthalate nonwoven fabric, nylon nonwoven fabric, polypropylene (PP), and polyethylene (PE).

[0075] In a preferred embodiment of the present invention, in order to make the coating slurry have both good adhesion and uniformity, in S1, the mass ratio of the pyridyl heterocyclic aramid polymer liquid to the nano-ceramic material is 1:0.015~0.25, for example, it can be 1:0.015, 1:0.020, 1:0.030, 1:0.040, 1:0.050, 1:0.060, 1:0.070, 1:0.080, 1:0.090, 1:0.10, 1:0.15, 1:0.20 and 1:0.25.

[0076] In a preferred embodiment of the present invention, in S1, the mass ratio of the nano-ceramic material to the additive is 1:0.106~0.605, for example, it can be 1:0.106, 1:0.150, 1:0.200, 1:0.250, 1:0.300, 1:0.350, 1:0.400, 1:450, 1:0.500, 1:0.550 and 1:0.600.

[0077] In a preferred embodiment of the present invention, in S1, the mixing conditions include: a stirring rate of 150-300 rpm, a temperature of 15-30°C, and a time of 1-3 h. The membrane preparation conditions of the present invention are mild and the operation is simple.

[0078] In a preferred embodiment of the present invention, in step S2, the conditions of the coagulation bath include: a temperature of 20~30°C, a time of 1~10 min, and a mass ratio of organic solvent to water of 1:0.5~1.

[0079] In a preferred embodiment of the present invention, the organic solvent of the coagulation bath is selected from one or more of N,N-dimethylacetamide, N-methylpyridinone, N,N-dimethylformamide, trifluoroethanol and tert-butanol.

[0080] In a preferred embodiment of the present invention, the drying conditions include: a temperature of 20~90℃ and a time of 1~2h.

[0081] In a second aspect, the present invention provides a battery separator, which is prepared according to the preparation method described in the first aspect.

[0082] Thirdly, the present invention provides a lithium battery, the lithium battery comprising: a positive electrode material, a negative electrode material, an electrolyte, and a battery separator, wherein,

[0083] The battery separator is the battery separator described in the second aspect.

[0084] The lithium battery made using the battery separator of this invention has good safety performance and a longer lifespan.

[0085] In this invention, the room temperature is 15-30°C.

[0086] The present invention will be described in detail below through examples. In the following examples, the pharmaceuticals and agents are all conventional commercially available products.

[0087] Example 1

[0088] (1) Under room temperature conditions, nitrogen gas was introduced into the reactor for protection, and 900g of N-methylpyridinone, 2.16g of Candida lipase, 102g of pyridine dicarboxylate chloride, 101.5g of isophthaloyl chloride, and 108g of m-phenylenediamine were added. The mixture was stirred for 1 hour, and 80g of sodium hydroxide was added for neutralization to obtain pyridine-based heterocyclic aramid polymer liquid 1.

[0089] (2) Under stirring conditions, 85g of aluminum oxide with a particle size of 200nm was added to pyridyl heterocyclic aramid polymer liquid 1, and then 30g of dimethyl carbonate was added. After stirring for 2 hours, coating slurry 1 was prepared.

[0090] (3) Apply coating slurry 1 to one side of the polyethylene film, and then immerse it in a coagulation bath of N-methylpyridinyl ketone and water for 5 minutes. The weight ratio of N-methylpyridinyl ketone to water is 1:1. After taking it out, dry it at 50°C to obtain pyridinyl heterocyclic aramid coated lithium battery separator 1.

[0091] Among them, the NMR data of pyridyl heterocyclic aramid: 1 HNMR (400 MHz, DMSO) δ 11.11 (d, J =17.8 Hz, 2H), 10.46 (d, J = 26.3 Hz, 2H), 8.42 (s, 2H), 8.34 (m, 1H), 8.08(m, 5H), 8.03 (m, 2H),7.91 (m, 4H), 7.78 (d, J = 7.8 Hz, 1H).

[0092] The specific logarithmic viscosity of pyridyl heterocyclic aramid is 2.1 dL / g.

[0093] Example 2

[0094] (1) Under room temperature conditions, nitrogen gas was introduced into the reactor for protection, and 900g of N-methylpyridinone, 2.16g of Candida lipase, 102g of pyridine dicarboxylate chloride, 101.5g of terephthaloyl chloride, and 108g of p-phenylenediamine were added. The mixture was stirred for 1 hour, and 80g of sodium hydroxide was added to neutralize it, so as to obtain pyridine-based heterocyclic aramid polymer liquid 2.

[0095] (2) Under stirring conditions, 85g of aluminum oxide with a particle size of 200nm was added to pyridyl heterocyclic aramid polymer liquid 2, and then 30g of dimethyl carbonate was added and stirred for 2 hours to prepare coating slurry 2.

[0096] (3) Coating slurry 2 is applied to one side of the polyethylene base film, and then immersed in a coagulation bath of trifluoroethanol and water for 5 minutes. The weight ratio of trifluoroethanol to water is 1:1. After taking it out, it is dried at 50°C to obtain pyridine-based heterocyclic aramid coated lithium battery separator 2.

[0097] The specific logarithmic viscosity of pyridyl heterocyclic aramid is 2.6 dL / g.

[0098] Example 3

[0099] (1) Under room temperature conditions, nitrogen gas was introduced into the reactor for protection, and 900g of N-methylpyridinone, 2.16g of Candida lipase, 163g of pyridine dicarboxylate chloride, 40.6g of terephthaloyl chloride, and 108g of p-phenylenediamine were added. The mixture was stirred for 1 hour, and 80g of sodium hydroxide was added to neutralize it, so as to obtain pyridine-based heterocyclic aramid polymer liquid 3.

[0100] (2) Under stirring conditions, 85g of aluminum oxide with a particle size of 200nm was added to pyridyl heterocyclic aramid polymer liquid 3, and then 30g of dimethyl carbonate was added and stirred for 2 hours to prepare coating slurry 3.

[0101] (3) Apply coating slurry 3 to one side of polyethylene film, and then immerse it in a coagulation bath of N-methylpyridinyl ketone and water for 5 minutes. The weight ratio of N-methylpyridinyl ketone to water is 1:1. After taking it out, dry it at 50°C to obtain pyridinyl heterocyclic aramid coated lithium battery separator 3.

[0102] The specific logarithmic viscosity of pyridyl heterocyclic aramid is 3.1 dL / g.

[0103] Example 4

[0104] The method described in Example 3 was carried out, except that "85g of aluminum oxide with a particle size of 200nm" was replaced with "40g of aluminum oxide with a particle size of 200nm plus 40g of PVDF" to prepare pyridine-based heterocyclic aramid coated lithium battery separator 4.

[0105] Comparative Example 1

[0106] The lithium battery separator was prepared by implementing the method described in Example 1, except that Candida lipase was not added.

[0107] Comparative Example 2

[0108] The method described in Example 1 was carried out, except that "pyridine dicarboxylate chloride" was replaced with an equimolar amount of isophthaloyl chloride to prepare a conventional meta-aramid coated lithium battery separator.

[0109] Comparative Example 3

[0110] The method described in Example 2 was carried out, except that "pyridine dicarboxylate chloride" was replaced with an equimolar amount of terephthaloyl chloride to prepare a conventional para-aramid-coated lithium battery separator.

[0111] Test Example 1

[0112] The performance of the polymer solutions prepared in Examples 1-4 and Comparative Examples 1-3 with lithium battery separators was tested, and the results are shown in Table 1.

[0113] Table 1

[0114]

[0115] According to the specific logarithmic viscosity data of Comparative Example 1 and Comparative Example 1 in Table 1, it can be seen that the addition of Candida lipase as a catalyst can greatly increase the degree of polymerization of the polymer, and the specific logarithmic viscosity increases from 0.6 to 2.1, which proves that Candida lipase has extremely strong catalytic efficiency.

[0116] Based on the stability data of Examples 1-3, Comparative Examples 1 and 2-3, it can be seen that the pyridyl heterocyclic aramid polymer solution has strong stability and does not separate into phases, while aramid does separate into phases and the slurry stability is poor. Comparing the membrane thermal performance data of Examples 1-3, it can be seen that the thermal performance of the coated membrane prepared by copolymerization of terephthaloyl chloride, pyridine dicarboxylate chloride and p-phenylenediamine (Examples 2-3) is better than that of the coated membrane prepared by copolymerization of isophthaloyl chloride, pyridine dicarboxylate chloride and m-phenylenediamine (Example 1). This is because p-phenylenediamine and terephthaloyl chloride have stronger rigidity than m-phenylenediamine and isophthaloyl chloride.

[0117] Example 3 differs from Example 2 in that it uses a larger proportion of pyridine dicarboxylate chloride, resulting in the best thermal performance, with heat shrinkage of 1.2% and 3.1% at 130°C and 150°C, respectively.

[0118] Comparing the peel strength data of the membranes in Examples 1-4, it can also be found that the peel strength after adding the copolymer structure of p-phenylene (Examples 2-3) is lower than that of the copolymer structure of isophenylene (Example 1) because the isophenylene structure is more flexible. The peel strength of Example 4 is the highest because the addition of PVDF enhances the adhesion between the coating and the base film.

[0119] The data from Examples 1-3 and Comparative Examples 2-3 show that the apparent viscosity of pyridine-based heterocyclic aramids (Examples 1-3) is lower than that of Comparative Examples 2-3 when the degree of polymerization is higher, indicating that pyridine-based heterocyclic aramids have stronger solubility than traditional aramids.

[0120] In summary, the pyridine-based heterocyclic aramid used in the battery separator of this invention is the first heterocyclic aramid material synthesized by Candida albicans lipase catalysis. The catalyst has high activity, the prepared product has a high molecular weight, and compared with traditional aramid, it has high stability and can be stored for a long time, thus improving the processability of the material. In addition, the pyridine-based heterocyclic aramid prepared by this invention has good solubility, requires less solvent in the coating process, has a high product yield, and low process cost.

[0121] Meanwhile, the battery separator of this invention uses pyridine-based heterocyclic aramid coating, which greatly improves its thermal performance. At 130°C, the thermal shrinkage is as low as 1.2%, and at 150°C, the thermal shrinkage is as low as 3.1%. The coating has good adhesion to the base film, the ceramic on the surface does not shed powder, and the peel strength is as high as 131 N / m. While greatly improving the safety performance of the lithium battery separator, it can also extend the battery life and has a higher cost performance.

[0122] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0123] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0124] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a battery separator, characterized in that, The preparation method includes the following steps: S1. A coating slurry is prepared by mixing pyridyl heterocyclic aramid polymer liquid, nano-ceramic material and additives; S2. Apply the coating slurry described in S1 to at least one surface of the base film, then place it in a coagulation bath and dry. In S1, the structural formula of the pyridyl heterocyclic aramid is shown in Formula I and Formula II. ， ； Where m≥10, n≥10, and m and n are both integers; The specific logarithmic viscosity of the pyridyl heterocyclic aramid is 2.0~3.5 dL / g.

2. The preparation method according to claim 1, characterized in that, In S1, the preparation method of the pyridyl heterocyclic aramid polymer liquid includes: in the presence of a solvent, in an inert atmosphere, first mixing Candida lipase and diformyl chloride monomer, second mixing with diamine monomer, and neutralization reaction with inorganic base to obtain pyridyl heterocyclic aramid polymer liquid.

3. The preparation method according to claim 2, characterized in that, The solvent is selected from one or more of N,N-dimethylacetamide, N-methylpyridinone, N-ethylpyridinone, N,N-dimethylformamide and sulfolane; And / or, the inert atmosphere is a nitrogen atmosphere and / or an argon atmosphere; And / or, the dicarboxylic acid chloride monomer is a pyridine dicarboxylic acid chloride monomer or a comonomer composed of pyridine dicarboxylic acid chloride and aromatic dicarboxylic acid chloride; And / or, the diamine monomer is an aromatic diamine; And / or, the inorganic base is lithium hydroxide and / or sodium hydroxide.

4. The preparation method according to claim 3, characterized in that, The pyridine dicarboxylate chloride is 2,6-pyridine dicarboxylate chloride and / or 2,5-pyridine dicarboxylate chloride; The aromatic dicarboxylic chloride is terephthaloyl chloride and / or isophthaloyl chloride; The aromatic diamine is p-phenylenediamine and / or m-phenylenediamine.

5. The preparation method according to any one of claims 2-4, characterized in that, In S1, the molar ratio of the diformyl chloride monomer to the diamine monomer is 0.8~1.3:1; and / or, The solvent in the pyridyl heterocyclic aramid polymerization solution has a mass fraction of 50-80%; and / or, The mass ratio of the diamine monomer to Candida lipase is 1:0.015~0.058; and / or, The molar ratio of the inorganic base to the diamine monomer is 1.6 to 2.6:

1.

6. The preparation method according to claim 1, characterized in that, In S1, the nano-ceramic material is selected from one or more of alumina, magnesium oxide, aluminum hydroxide, and silicon dioxide; and / or, The particle size of the nano-ceramic material is 10~1000 nm; and / or, The additive is selected from one or more of ethanol, dimethyl carbonate, and PVDF; and / or, In S2, the material of the base film is selected from one of polyethylene terephthalate nonwoven fabric, nylon nonwoven fabric, polypropylene (PP), and polyethylene (PE).

7. The preparation method according to claim 1, characterized in that, In S1, the mass ratio of the pyridyl heterocyclic aramid polymer liquid to the nano-ceramic material is 1:0.015~0.25; and / or, The mass ratio of the nano-ceramic material to the additive is 1:0.106~0.

605.

8. The preparation method according to claim 1, characterized in that, In S1, the mixing conditions include: a stirring rate of 150-300 rpm, a temperature of 15-30°C, and a time of 1-3 hours; and / or, In S2, the conditions of the coagulation bath include: a temperature of 20~30℃, a time of 1~10 min, and a mass ratio of organic solvent to water of 1:0.5~1; and / or, The organic solvent is selected from one or more of N,N-dimethylacetamide, N-methylpyridinone, N,N-dimethylformamide, trifluoroethanol, and tert-butanol; and / or, The drying conditions include a temperature of 20~90℃ and a time of 1~2h.

9. A battery separator, characterized in that, The battery separator is prepared by the method according to any one of claims 1-8.

10. A lithium battery, characterized in that, The lithium battery includes: a positive electrode material, a negative electrode material, an electrolyte, and a battery separator, wherein, The battery separator is the battery separator as described in claim 9.

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