Preparation method of furan ring-containing bio-based aramid fiber / ceramic coated polyolefin diaphragm

Abstract

The invention discloses a preparation method of a furan ring-containing bio-based aramid fiber / ceramic coated polyolefin diaphragm, and belongs to the technical field of synthesis of bio-based high-molecular compounds, the method comprises the following steps: synthesizing bio-based bifurandiamine salt with ionic conductivity, neutralizing the bio-based bifurandiamine salt into a bio-based bifurandiamine monomer, and then adding the bio-based bifurandiamine monomer into the bio-based high-molecular compound to prepare the furan ring-containing bio-based aramid fiber / ceramic coated polyolefin diaphragm. And carrying out interfacial polycondensation on the furan ring-containing bio-based aramid fiber and a diacid monomer to obtain an aqueous furan ring-containing bio-based aramid fiber solution, preparing the aqueous furan ring-containing bio-based aramid fiber solution and ceramic into a mixed slurry, and coating the surface of a polyolefin diaphragm with the mixed slurry to obtain the required diaphragm. Through the cooperation of the furan ring-containing bio-based aramid fiber and the ceramic, the temperature resistance, the electrolyte infiltration performance and the ionic conductivity of the polyolefin-based membrane are improved, the electrochemical performance of the lithium / sodium battery is effectively improved, the cycle life of the lithium / sodium battery is effectively prolonged, the application field of the aramid fiber membrane in the lithium / sodium battery is widened, and the application prospect of the aramid fiber membrane in the lithium / sodium battery is widened.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of bio-based polymer compounds, and also to the technical field of lithium battery or sodium battery diaphragm, and in particular to a method for preparing a furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm. Background Art

[0002] As one of the key components of the battery, the separator plays an important role in preventing internal short circuits while maintaining ion transport between the anode and cathode. More importantly, the performance of the separator affects the key characteristics of lithium-ion batteries, such as electrochemical performance, service life and safety. At present, due to its chemical and electrochemical stability, ideal porosity and acceptable cost, microporous polyolefin-based membranes (PE, PP, PP / PE) have become the most commonly used lithium-ion battery (LIB) separators on the market. However, the melting point of polyolefin separators is low, usually 130-160°C. When the external temperature reaches or exceeds its melting point, the separator will shrink or melt over a large area, resulting in thermal runaway or short circuit inside the battery. In addition, the polarity of the polyolefin separator is greatly different from that of the organic electrolyte, resulting in poor wettability of the electrolyte to the separator. The separator has poor ability to retain the electrolyte during repeated charge and discharge, thereby affecting the cycle performance of the battery. The hybrid ceramic separator prepared from excellent high-temperature resistant inorganic materials (ceramics, hydroxyapatite, etc.) has good thermal stability and electrolyte wettability. However, this approach still has other problems, such as poor interfacial adhesion, low peel strength, and sacrificial porosity leading to reduced ionic conductivity.

[0003] Aramid nanofiber (ANF) based membranes have excellent electronic insulation, thin thickness, excellent mechanical strength, excellent thermal stability and heat resistance, and high electrochemical stability. They can meet the various performance requirements of lithium-ion battery separators and are expected to be used to further improve the mechanical properties and thermal stability of separators. However, this type of aramid material still belongs to petroleum-based benzene ring polymers, with limited improvement in wettability and ionic conductivity, and poor solubility. They do not have excellent performance at the moment when low-cost, environmentally friendly water-based materials are developing rapidly. Aromatic polyamides are limited in processing and application due to their poor solubility, but the introduction of aromatic heterocyclic structures into the main chain of the molecule can effectively improve the solubility and heat resistance of aromatic polyamides. Furandicarboxylic acid (FDCA) is one of the bio-based platform molecules promoted by the U.S. Department of Energy and is known as the "sleeping giant". Furandicarboxylic acid (FDCA) and its derivatives are ideal heterocyclic structures for replacing aromatic diacids or diamines to prepare polyamides. Compared with the pure non-polar benzene ring structure, the furan ring structure of bio-based aramid has higher polarity, structural similarity and stronger interaction with the main organic solvent molecules of the electrolyte, making the bio-based aramid better infiltrated, which helps to solve the high wettability requirements for the diaphragm under high energy density requirements.

[0004] In summary, the current polyolefin separators have the disadvantages of insufficient wettability and poor thermal dimensional stability. It is urgent to develop a battery separator with high wettability, thermal stability, and excellent ionic conductivity to improve the operating efficiency and cycle life of the battery. Summary of the invention

[0005] Based on the shortcomings of the above-mentioned prior art, the present invention provides a method for preparing a furan ring-containing bio-based aramid / ceramic coated polyolefin separator, aiming to solve the problems of poor wettability of existing battery separators in electrolyte, poor thermal dimensional stability and low ionic conductivity when the separator is used in primary batteries or secondary batteries.

[0006] In order to achieve the purpose, the present invention adopts the following technical solutions: The present invention first provides a method for preparing a furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm, comprising the following steps: Step 1, synthesizing a bio-based bisfuran diamine salt having ion conductivity; Step 2: After the bio-based bisfuran diamine salt is neutralized to obtain a bio-based bisfuran diamine monomer, the bio-based bisfuran diamine monomer is subjected to interfacial polycondensation with a diacid monomer to obtain an aqueous furan ring-containing bio-based aramid solution: Step 3: Mix the aqueous furan ring-containing bio-based aramid solution with ceramics to prepare a mixed slurry, and apply it on one or both sides of the polyolefin diaphragm to obtain a furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm.

[0007] Furthermore, the specific method of step 1 is: first, under low temperature conditions of -20~10°C, furfurylamine and levulinic acid are sequentially added dropwise to the acid solution, and then heated and stirred at 50-80°C for 2-4 hours; after the reaction is completed, the solution is cooled to room temperature, methanol is added and stirred to precipitate a precipitate; the precipitate is collected by suction filtration, and vacuum dried at 60-100°C to obtain a bio-based bisfuran diamine salt.

[0008] Furthermore: the furfurylamine and levulinic acid are both derived from biological raw materials, with a molar ratio of 2 to 8:1, preferably 2 to 4:1. The acid solution is one or more of hydrochloric acid, sulfuric acid, and acetic acid, and the mass concentration of the acid solution is 30 wt% to 60 wt%, preferably concentrated hydrochloric acid with a mass concentration of 37.5 wt%.

[0009] Furthermore, the specific method of step 2 is: dissolving the bio-based bisfuran diamine salt in water, adding a first base containing Li or Na to adjust the pH value to alkaline, and then stirring for 2 to 6 hours for neutralization reaction to obtain a bio-based bisfuran diamine solution; dissolving the diacid monomer in an organic solvent, and the organic solvent is immiscible with water to obtain a diacid monomer solution; adding the diacid monomer solution dropwise to the bio-based bisfuran diamine solution under high-speed stirring conditions, filtering, washing, and vacuum drying the precipitated solid to obtain a furan ring-containing bio-based aramid; dissolving the furan ring-containing bio-based aramid in deionized water at a mass concentration of 5 to 20%, and then adding a second base containing Li or Na to adjust the pH to 7 to 8 to obtain an aqueous furan ring-containing bio-based aramid solution.

[0010] Furthermore, the molar amount of the base containing Li or Na added for the first time is 2 to 4 times the molar amount of the bio-based bisfuran diamine salt. When the prepared diaphragm is used for a lithium battery, the base containing Li or Na is a base containing Li; when the prepared diaphragm is used for a sodium battery, the base containing Li or Na is a base containing Na.

[0011] Furthermore, the diacid monomer is one or more of 2,5-furandicarboxylic acid FDCA, 2,5-furandicarboxylic acid chloride FDCl, terephthaloyl chloride TPC, isophthaloyl chloride IPC, 4,4'-oxydiphthalic anhydride ODPA, preferably ODPA and FDCl. The molar ratio of the bio-based bisfuran diamine salt to the diacid monomer is 1-2:1.

[0012] Furthermore, the composition of the components in the mixed slurry in step 3 by mass percentage is as follows: Aqueous furan ring-containing bio-based aramid solution 5-25 wt%; Liquid alumina slurry (alumina dispersed in water) with a mass concentration of 50-75% 55-80 wt%; 0.1~5% sodium carboxymethyl cellulose dispersion (CMC-Na dispersed in water) 2-10 wt%; Polyacrylate adhesive 2-10 wt%; Polyoxyethylene ether wetting agent 0.1-0.5 wt%.

[0013] Furthermore, in step 3: the polyolefin-based membrane is one or more of a PP membrane, a PE membrane, and a PP / PE composite membrane. The coating is performed on a wire rod coater with a gap of 1-3 μm, and after coating, it is placed in a blast oven at 40-80° C. and dried for 20-60 minutes to obtain a furan ring-containing bio-based aramid / ceramic coated polyolefin membrane.

[0014] The present invention also provides a furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm prepared by the above preparation method, which has a thin thickness (5-10 μm), a porosity of 50%-60%, an electrolyte (LiPF6 / (EC, PC, DEC=1:1:1)) wetting rate of 50-60 mm / 60s, an electrolyte contact angle of 0°, a thermal shrinkage of <1% in the MD direction and <1% in the TD direction at 150°C for 1 h, and a room temperature ionic conductivity of 1-2 ms / cm.

[0015] The present invention further provides a battery (lithium battery or sodium battery), which uses the above-mentioned separator as a component for separating positive and negative electrodes, and the battery is a primary battery or a secondary battery.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The battery separator prepared by coating a mixed slurry of water-based furan ring-containing bio-based aramid and ceramic on a polyolefin-based film has a higher polarity and structural similarity with the main organic solvent molecules of the electrolyte due to the polar structures such as furan rings, ether bonds and polyamides, and a stronger interaction, so that the bio-based aramid has better wettability, which is conducive to the rapid diffusion of the electrolyte on the separator to achieve a complete wetting effect. This will greatly reduce the internal resistance of the separator and improve the electrochemical performance and cycle life of the battery.

[0017] 2. The furan ring-containing bio-based aramid synthesized by the present invention has a decomposition temperature far exceeding that of polyolefin-based membranes such as PE. Coupled with the excellent heat resistance of the inorganic ceramic particles, the prepared diaphragm has excellent thermal dimensional stability, and can achieve thermal shrinkage of <1% in the MD direction and <1% in the TD direction after 1 h at 150°C. The low thermal shrinkage capacity can reduce the safety risks of the battery when it is abnormally heated.

[0018] 3. The innovation of the present invention lies in the use of bio-based raw materials to synthesize bisfurandiamine monomers with ion conductivity. Specifically, furfurylamine and levulinic acid are used for electrophilic addition reaction to obtain ion exchange polyamide containing free cation exchange carboxylic acid (-COOH) groups, so that the prepared diaphragm has excellent ion transmission ability and improves battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0020] Figure 1 This is a SEM image of the furan ring-containing bio-based aramid fiber prepared in Example 2 of the present invention.

[0021] Figure 2 This is a SEM image of the furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm prepared in Example 2 of the present invention.

[0022] Figure 3 The figure is a comparison chart of the thermal shrinkage performance of battery separators prepared in various embodiments of the present invention and comparative examples at 150°C for 1 hour.

[0023] Figure 4 100 cycle graphs of lithium batteries assembled with battery separators prepared in various embodiments of the present invention and comparative examples. DETAILED DESCRIPTION

[0024] In order to explain the present invention more clearly, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1 In this example, the furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm is prepared according to the following steps: Step 1: Synthesis of bio-based bisfuran diamine salt with ion conductivity 2 mol of furfurylamine was added dropwise to 500 mL of concentrated HCL solution under nitrogen protection in an ice bath, followed by 1 mol of levulinic acid. After the addition was complete, the mixture was heated and stirred at 60 °C for 3 h. The reactants were cooled to room temperature, and sufficient methanol was added and stirred to precipitate. The precipitate was collected by suction filtration, and the product was dried in vacuo at 80 °C to obtain bio-based bisfuran diamine salt.

[0026] Step 2: Preparation of aqueous furan ring-containing bio-based aramid solution Dissolve the reaction monomers separately in mutually incompatible solvents: Dissolve 1 mol of bio-based bisfuran diamine salt in 400 mL of water, add 3 mol of LiOH to adjust the pH value to alkaline, and then stir for 2 h for neutralization reaction to obtain a bio-based bisfuran diamine solution. Dissolve the diacid monomer (1 mol of FDCl monomer) in 200 mL of CH2Cl2 to obtain a diacid monomer solution.

[0027] The diacid monomer solution was added dropwise to the bio-based bisfuran diamine solution under high-speed stirring. Solids were continuously precipitated during the addition process, and the addition was completed after 1 hour. The precipitated solids were filtered, washed with deionized water and methanol, and then vacuum dried at 100 °C to obtain the bio-based aramid containing furan rings; the obtained bio-based aramid containing furan rings was dissolved in deionized water at a mass concentration of 5%, and LiOH was added to adjust the pH to 7, and stirred for 2 hours to evenly disperse the aramid in the solution to obtain an aqueous bio-based aramid solution containing furan rings.

[0028] Step 3: Preparation of furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm First, weigh the raw materials according to the following mass percentages: Aqueous furan ring-containing bio-based aramid solution 15 wt%; Liquid alumina slurry with a mass concentration of 60% 75 wt%; 4.5 wt% sodium carboxymethyl cellulose dispersion with a mass concentration of 1%; Polyacrylate adhesive 5 wt%; Polyoxyethylene ether wetting agent 0.5 wt%.

[0029] The above raw materials were mixed in a beaker and stirred at 600 rpm for 4 h with a magnetic stirrer to obtain a uniform, milky white, impurity-free coating slurry with a solid content of about 30%. Then the coating was carried out on an inline rod coater with a gap of 2 μm, and a 7 μm commercial polyethylene diaphragm was used as the coating base film. After coating, it was placed in a 60°C forced air oven and dried for 30 min to obtain a furan ring-containing bio-based aramid / ceramic coated polyethylene diaphragm.

[0030] Example 2 In this example, a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator was prepared in the same manner as in Example 1, except that the diacid monomer in step 2 was replaced with 0.8 mol FDCl and 0.2 mol ODPA.

[0031] Example 3 In this example, a furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm was prepared in the same manner as in Example 1, except that the diacid monomer in step 2 was replaced with 0.6 mol FDCl and 0.4 mol ODPA.

[0032] Example 4 In this example, a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator was prepared in the same manner as in Example 1, except that the diacid monomer in step 2 was replaced with 1 mol of ODPA.

[0033] Example 5 In this example, a furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm is prepared in the same manner as in Example 1, except that the diacid monomers in step 2 are replaced by 0.2 mol FDCl, 0.2 mol FDCl, 0.2 mol IPC, 0.2 mol TPC, and 0.2 mol ODPA monomers.

[0034] Example 6 In this example, a furan ring-containing bio-based aramid / ceramic coated polyolefin separator is prepared by the same method as in Example 1, except that 2 mol of furfurylamine in step 1 is replaced by 4 mol of furfurylamine.

[0035] Comparative Example 1 This comparative example prepared a ceramic-coated polyolefin diaphragm according to the following steps: First, weigh each raw material according to the following mass percentage Liquid alumina slurry with a mass concentration of 60% 90 wt%; 4.5 wt% sodium carboxymethyl cellulose dispersion with a mass concentration of 1%; Polyacrylic acid adhesive 5 wt%; Polyoxyethylene ether wetting agent 0.5 wt%.

[0036] The above raw materials were mixed in a beaker and stirred at 600 rpm for 4 hours with a magnetic stirrer to obtain a uniform, milky white, impurity-free coating slurry with a solid content of about 30%. Then the coating was carried out on an inline rod coater with a gap of 2 μm, and a 7 μm commercial polyethylene diaphragm was used as the coating base film. After coating, it was placed in a 60°C blast oven and dried for 30 minutes to obtain a ceramic-coated polyethylene diaphragm.

[0037] Comparative Example 2 The diaphragm is a commercial polyethylene membrane with a thickness of 7 μm.

[0038] The coated diaphragms obtained in Examples 1 to 6 and the comparative examples were tested, and the specific test methods are as follows: 1. Thickness test: The thickness of the lithium battery separator was tested using a thickness gauge provided by Mahr according to the standard GB / T6672-2001.

[0039] 2. Wetting performance test: The wettability characterization of the coated membranes includes contact angle measurements of the surfaces and membrane wetting rate testing.

[0040] The contact angle was tested using Dongguan Shengding's optical contact angle meter with electrolyte (LiPF6 / (EC, PC, DEC=1:1:1), LiPF6 concentration 1 mol / L). The amount of liquid dropped each time was controlled at 3 μL. The dropper was pushed to make the test medium drop on the surface of the test diaphragm. The camera automatically recorded the whole process and calculated the contact angle.

[0041] The membrane wetting rate was measured by dropping 10 μL of electrolyte (LiPF6 / (EC, PC, DEC=1:1:1), LiPF6 concentration 1 mol / L) on a long strip of filter paper and observing the electrolyte wetting distance after 60 s.

[0042] 3. Porosity test: The coated diaphragm and PE base film were cut into rectangles of 5×5 cm, and the mass m0 of the diaphragm before the test was weighed. Then, the diaphragm was soaked in n-butanol, taken out after standing for 2 hours, and the residual n-butanol on the surface of the diaphragm was quickly wiped with a non-woven cloth, and the mass m1 was obtained after weighing. The porosity can be calculated according to the following formula:

[0043] In the formula ρ b =0.81 g / mL, V m is the volume of the coated membrane.

[0044] 4. Diaphragm thermal stability performance test: The coated diaphragm and PE base film were cut into 15 cm × 10 cm rectangles, and then a 10 cm × 5 cm rectangle was drawn on its surface with a marker. The length and width of the rectangle before the test were measured using a quadrature measuring instrument. Subsequently, the diaphragms were placed in a blast oven at 150 ° C for 1 hour. After that, the length and width of the rectangle were measured again. Based on the difference between the two measurement results, the thermal shrinkage of the diaphragm within 1 hour in the transverse direction (TD) and the longitudinal direction (MD) were calculated respectively: MD heat shrinkage rate = [(initial length - length after heat shrinkage) / initial length] × 100%; TD heat shrinkage rate = [(initial width - width after heat shrinkage) / initial width] × 100%.

[0045] 5. Diaphragm ion conductivity test: Use a punching machine to cut the dried coated diaphragm and PE base film with a diameter of 19 mm, and measure the thickness with a micrometer. In the glove box, CR2016 button cells were assembled in the following order: positive electrode shell, diaphragm, electrolyte (LiPF6 / (EC, PC, DEC=1:1:1), LiPF6 concentration 1 mol / L), stainless steel sheet, shrapnel and negative electrode shell. After the battery was assembled, it was allowed to stand at room temperature for 12 hours. Then, the AC impedance mode was selected in the electrochemical workstation, and the amplitude was set to 5 mV and the frequency range was 0.1 to 10 5 Hz, and the equilibrium time is 2 seconds. According to the EIS spectrum of the test results, the intrinsic resistance R of the diaphragm is obtained. b , and calculate its ionic conductivity according to the formula:

[0046] Where: σ is the ionic conductivity (S cm －1 ); L is the thickness of the diaphragm (cm); R b is the intrinsic resistance of the diaphragm (Ω); A is the effective area (cm 2 ).

[0047] 6. Diaphragm mechanical properties test: Each item was tested using a universal material testing machine from Shenzhen Sansi Zongheng Company, with a set speed of 100 mm / min. The membrane samples were cut into test strips with an aspect ratio of 200 mm × 15 mm for tensile testing; the membranes were cut into test strips with an aspect ratio of 80 mm × 30 mm for peel strength testing. The samples were prepared in the order of sample board, double-sided tape, sample, and transparent tape, and the coating was peeled off through the transparent tape.

[0048] The experimental results are shown in the following table:

[0049] Examples 1-6 are battery separators prepared by coating a mixture of furan ring-containing bio-based aramid and ceramic on a PE base film, Comparative Example 1 is a battery separator prepared by coating ceramic on a PE base film, and Comparative Example 2 is a pure PE separator. It can be clearly seen from the data in the table that the wetting rate and contact angle of the separator with the addition of furan ring-containing bio-based aramid are higher than those of the ceramic separator and the PE base film, which indicates that the wetting performance of the separator is effectively improved, thanks to the fact that the polar furan ring, ether bond, and amide bond structure of the furan ring-containing bio-based aramid have higher polarity and structural similarity with the main organic solvent molecules of the electrolyte, stronger interaction, better interfacial compatibility, greatly increased contact ability with the electrolyte, and effectively improved wetting performance. In addition, the thermal dimensional stability of the diaphragm with the addition of furan ring-containing bio-based aramid is also improved. The thermal shrinkage of the diaphragm in Examples 1-6 at 150 ° C for 1 h is MD<1%, TD<1%, while the thermal shrinkage in Comparative Examples 1-2 exceeds 50%, which shows that the excellent temperature resistance of the furan ring-containing bio-based aramid plays an important role in the addition of the diaphragm. The ionic conductivity mainly tests the rate at which ions shuttle in the diaphragm. The detection of ionic conductivity can test the efficiency of the diaphragm in shuttling lithium ions in the battery. As can be seen from the table, the ionic conductivity of the diaphragm with the addition of furan ring-containing bio-based aramid is significantly increased relative to the ceramic diaphragm and PE-based membrane. This is because the bisfuran diamine structure contains free cation exchange carboxylic acid (-COOH) groups, which gives the diaphragm excellent Li + The addition of furan ring-containing bio-based aramid increases the porosity of the diaphragm, which can increase the ion shuttle channel and thus increase the ion conductivity of the diaphragm. It is worth noting that the addition of furan ring-containing bio-based aramid greatly restrains the inorganic ceramic particles, thereby improving the overall mechanical strength (tensile strength, peel strength) of the diaphragm.

[0050] Figure 1 This is a SEM image of the bio-based aramid containing furan rings prepared in Example 2. It can be seen from the image that the product has a nanoparticle morphology.

[0051] Figure 2 This is a SEM image of the furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm prepared in Example 2. It can be seen from the figure that the furan ring-containing bio-based aramid and the ceramic are evenly distributed without aggregation, and the bio-based aramid wraps the ceramic particles.

[0052] Figure 3 This is a comparison chart of the thermal shrinkage performance of battery separators at 150 °C for 1 h. It can be seen from the figure that the furan ring-containing bio-based aramid / ceramic-coated polyolefin separator did not undergo obvious thermal shrinkage at 150 °C, while the ceramic separator and PE separator had obvious thermal shrinkage.

[0053] Figure 4The 100 cycle diagrams (0.5 C rate) of lithium batteries assembled with battery separators prepared in various embodiments of the present invention and comparative examples are shown. It can be seen from the figure that after 100 cycles, the batteries assembled with ceramic separators (Comparative Example 1) and PE separators (Comparative Example 2) showed obvious capacity decay. The discharge capacity of the PE separator battery dropped from 145 mAh / g to 97 mAh / g before and after 100 cycles, and the capacity retention rate was 66.9%. The discharge capacity of the ceramic separator battery dropped from 145 mAh / g to 126 mAh / g before and after 100 cycles, and the capacity retention rate was 86.9%. The battery assembled with furan ring-containing bio-based aramid / ceramic coated polyethylene separator (Example 2) showed better cycle stability. The initial and final discharge capacity of the battery were 147.8 mAh / g and 147.7 mAh / g, respectively, and the capacity retention rate was as high as 99.9%. The Coulombic efficiency of batteries using ceramic and PE separators also decayed significantly after 100 cycles, reaching 84.2% and 64.9%, respectively, while the Coulombic efficiency of batteries assembled with furan ring-containing bio-based aramid / ceramic-coated polyethylene separator reached 98.5%, showing excellent cycle stability.

[0054] In summary, the present invention adopts a polyolefin diaphragm as a substrate, and a furan ring-containing bio-based aramid / ceramic material is coated on the surface of the substrate. The carboxyl group with ion exchange capacity in the diamine monomer of the furan ring-containing bio-based aramid improves the ion conductivity of the diaphragm; the furan ring-containing bio-based aramid is a polyamide with polar structures such as furan rings, ether bonds, and amide bonds, which can enhance the interfacial compatibility between the diaphragm and the electrolyte, facilitate the diffusion of the electrolyte, and improve the wettability of the diaphragm. The furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm has the excellent heat resistance of both ceramic and polyamide structures. The prepared battery diaphragm improves the heat resistance and electrolyte wettability of the polyolefin-based membrane, effectively improves the electrochemical performance and cycle life of lithium / sodium batteries, and broadens the application field and application prospects of aramid diaphragms in lithium / sodium batteries.

[0055] All numerical values ​​specified in the examples of the present invention (such as temperature, time, concentration and weight, etc., including the range of each thereof) are generally approximate values ​​that can be appropriately changed by increments of 0.1 or 1.0 (+) or (-). All numerical values ​​specified can be understood as being preceded by the term "about".

[0056] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or equivalent replacement that can be made by other technicians in this field without inventive work falls within the protection scope of the present invention.

Claims

1. A method for preparing a furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm, characterized in that: The following steps are involved: Step 1, synthesizing a bio-based bisfuran diamine salt having ion conductivity; Step 2, neutralizing the bio-based bisfuran diamine salt to obtain a bio-based bisfuran diamine monomer, and then subjecting the monomer to interfacial polycondensation with a diacid monomer to obtain an aqueous furan ring-containing bio-based aramid solution; Step 3: Mix the aqueous furan ring-containing bio-based aramid solution with ceramics to prepare a mixed slurry, and apply it on one or both sides of the polyolefin diaphragm to obtain a furan ring-containing bio-based aramid / ceramic coated polyolefin diaphragm.

2. The preparation method according to claim 1, characterized in that: The specific method of step 1 is: first, under low temperature conditions of -20~10°C, furfurylamine and levulinic acid are sequentially added dropwise to the acid solution, and then heated and stirred at 50-80°C for 2-4h; after the reaction is completed, the solution is cooled to room temperature, methanol is added and stirred to precipitate a precipitate; the precipitate is collected by suction filtration, and vacuum dried at 60-100°C to obtain a bio-based bisfuran diamine salt.

3. The preparation method according to claim 2, characterized in that: The furfurylamine and levulinic acid are both derived from biological raw materials, and the molar ratio is 2-8:

1.

4. The preparation method according to claim 1, characterized in that: The specific method of step 2 is: dissolving the bio-based bisfuran diamine salt in water, adding a first base containing Li or Na to adjust the pH value to alkaline, and then stirring for 2 to 6 hours for neutralization reaction to obtain a bio-based bisfuran diamine solution; dissolving the diacid monomer in an organic solvent, wherein the organic solvent is immiscible with water, to obtain a diacid monomer solution; The diacid monomer solution is added dropwise to the bio-based bisfuran diamine solution under stirring, and the precipitated solid is filtered, washed, and vacuum-dried to obtain the furan ring-containing bio-based aramid; the furan ring-containing bio-based aramid is dissolved in deionized water at a mass concentration of 5-20%, and a second Li or Na-containing base is added to adjust the pH to 7-8 to obtain an aqueous furan ring-containing bio-based aramid solution.

5. The preparation method according to claim 4, characterized in that: The molar amount of the base containing Li or Na added for the first time is 2 to 4 times the molar amount of the bio-based bisfuran diamine salt.

6. The preparation method according to claim 1 or 4, characterized in that: The diacid monomer is one or more of 2,5-furandicarboxylic acid FDCA, 2,5-furandicarboxylic acid chloride FDCl, terephthaloyl chloride TPC, isophthaloyl chloride IPC, and 4,4'-oxydiphthalic anhydride ODPA, and the molar ratio of the bio-based bisfuran diamine salt to the diacid monomer is 1-2:

1.

7. The preparation method according to claim 1, characterized in that: The composition of the components in the mixed slurry in step 3 by mass percentage is: Aqueous furan ring-containing bio-based aramid solution 5-25 wt%; Liquid alumina slurry with a mass concentration of 50-75% 55-80 wt%; 2-10 wt% sodium carboxymethyl cellulose dispersion with a mass concentration of 0.1-5%; Polyacrylate adhesive 2-10 wt%; Polyoxyethylene ether wetting agent 0.1-0.5 wt%.

8. The preparation method according to claim 1, characterized in that: The polyolefin membrane described in step 3 is one or more of a PP membrane, a PE membrane, and a PP / PE composite membrane.

9. A furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm prepared by the preparation method according to any one of claims 1 to 8.

10. A battery, characterized in that: The battery comprising the separator according to claim 9 is a primary battery or a secondary battery.

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