Preparation Method of Furan Ring-Containing Bio-Based Aramid / Ceramic Coated Polyolefin Separator

Abstract

The invention discloses a preparation method of a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator, belonging to the technical field of the synthesis of bio-based high molecular compounds. The method comprises the following steps: synthesizing a bio-based difuran diamine salt with ionic conductivity, neutralizing it to a bio-based difuran diamine monomer, and then obtaining an aqueous furan ring-containing bio-based aramid solution through interfacial polycondensation with a diacid monomer. The solution is mixed with ceramics to form a mixed slurry and coated on the surface of the polyolefin separator, thereby obtaining the required separator. Through the synergy of the furan ring-containing bio-based aramid and ceramics, the invention improves the temperature resistance performance, electrolyte infiltration performance and ionic conductivity of the polyolefin-based membrane, effectively improves the electrochemical performance and cycle life of lithium / sodium batteries, and broadens the application field and application prospect of aramid separators in lithium / sodium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of the synthesis of bio-based polymer compounds, and also relates to the technical field of diaphragms for lithium batteries or sodium batteries. Specifically, it relates to a preparation method of a furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm. Background Art

[0002] As one of the key components of a battery, the diaphragm plays an important role in preventing internal short circuits and at the same time maintaining ion transport between the anode and the cathode. More importantly, the performance of the diaphragm affects key characteristics such as the electrochemical performance, service life, and safety of lithium-ion batteries. Currently, 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) diaphragms in the market. However, polyolefin diaphragms have a low melting point, usually between 130-160 °C. When the external temperature reaches or exceeds its melting point, the diaphragm will undergo large-area shrinkage or melting, resulting in internal thermal runaway or short circuits in the battery. In addition, the polarity of polyolefin diaphragms differs greatly from that of organic electrolytes, resulting in poor wettability of the electrolyte on the diaphragm. During repeated charge and discharge processes of the battery, the diaphragm has poor electrolyte retention ability, thus affecting the cycle performance of the battery. Mixed ceramic diaphragms prepared from excellent high-temperature inorganic materials (such as ceramics, hydroxyapatite, etc.) have good thermal stability and electrolyte wettability. However, this method still has other problems, such as poor interfacial adhesion, low peel strength, and reduced ionic conductivity due to sacrificed porosity.

[0003] Aramid nanofiber (ANF)-based membranes have excellent electrical insulation, thin thickness, excellent mechanical strength, excellent thermal stability and heat resistance, and high electrochemical stability, which can meet the various performance requirements of lithium-ion battery diaphragms and are expected to be used for further research on improving the mechanical properties and thermal stability of diaphragms. However, such aramid materials still belong to petroleum-based benzene ring polymers, with limited improvement in wettability and ionic conductivity, and poor solubility, which is not excellent in the current rapid development of low-cost environmentally friendly water-based materials. Aromatic polyamides are limited in processing and application due to their poor solubility, but introducing an aromatic heterocyclic structure into the molecular main chain can effectively improve the solubility and heat resistance of aromatic polyamides. Furan dicarboxylic acid (FDCA) is one of the bio-based platform molecules strongly promoted by the US Department of Energy and is known as the "sleeping giant". Furan dicarboxylic 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 have better wettability, which helps to meet the high wettability requirements for diaphragms under high energy density demands.

[0004] In summary, the current polyolefin separators have the disadvantages of insufficient wettability and poor thermal dimensional stability. There is an urgent need to develop a battery separator with excellent properties such as high infiltration, thermal stability, and ionic conductivity to improve the operating efficiency and cycle life of the battery. Summary of the Invention

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

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

[0007] The present invention first provides a preparation method of a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator, comprising the following steps:

[0008] Step 1: Synthesize a bio-based difuran diamine salt with ionic conductivity ability;

[0009] Step 2: After neutralizing the bio-based difuran diamine salt to a bio-based difuran diamine monomer, carry out interfacial polycondensation with a diacid monomer to obtain an aqueous furan ring-containing bio-based aramid solution:

[0010] Step 3: Mix the aqueous furan ring-containing bio-based aramid solution with ceramics to form a mixed slurry, and coat one or both sides of the polyolefin separator to obtain a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator.

[0011] Further, the specific method of Step 1 is as follows: First, under low-temperature conditions of -20 to 10 °C, dropwise add furfurylamine and levulinic acid to an acid solution in sequence, and then heat and stir at 50 - 80 °C for 2 - 4 h; after the reaction ends, cool to room temperature, add methanol and stir to precipitate a solid; filter to collect the solid, and vacuum dry at 60 - 100 °C to obtain the bio-based difuran diamine salt.

[0012] Furthermore: Both the furfurylamine and the levulinic acid are derived from biological raw materials, and the molar ratio is 2 - 8:1, preferably 2 - 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% - 60 wt%, preferably concentrated hydrochloric acid with a mass concentration of 37.5 wt%.

[0013] Further, the specific method of step 2 is as follows: Dissolve the bio-based bifuran diamine salt in water, add an alkali containing Li or Na for the first time to adjust the pH value to alkaline, and then stir for 2 to 6 h for a neutralization reaction to obtain a bio-based bifuran diamine solution; dissolve the diacid monomer in an organic solvent that is immiscible with water to obtain a diacid monomer solution; under the condition of high-speed stirring, dropwise add the diacid monomer solution to the bio-based bifuran diamine solution, filter, wash, and vacuum dry the precipitated solid to obtain a bio-based aramid containing a furan ring; dissolve the bio-based aramid containing a furan ring in deionized water at a mass concentration of 5 to 20%, and then add an alkali containing Li or Na for the second time to adjust the pH to 7 to 8 to obtain an aqueous bio-based aramid solution containing a furan ring.

[0014] Furthermore: The molar amount of the alkali containing Li or Na added for the first time is 2 to 4 times the molar amount of the bio-based bifuran diamine salt. When the prepared separator is used in a lithium battery, the alkali containing Li or Na described above uses an alkali containing Li; when the prepared separator is used in a sodium battery, the alkali containing Li or Na described above uses an alkali containing Na.

[0015] Furthermore, the diacid monomer is one or more of 2,5-furandicarboxylic acid FDCA, 2,5-furandicarbonyl chloride FDCl, terephthaloyl chloride TPC, isophthaloyl chloride IPC, 4,4'-oxybisphthalic anhydride ODPA, preferably ODPA and FDCl. The molar ratio of the bio-based bifuran diamine salt to the diacid monomer is 1 to 2:1.

[0016] Further, the composition of each component in the mixed slurry described in step 3 by mass percentage is as follows:

[0017] Aqueous bio-based aramid solution containing a furan ring 5-25 wt%;

[0018] Liquid alumina slurry with a mass concentration of 50 to 75% (alumina is dispersed in water) 55-80 wt%;

[0019] Sodium carboxymethyl cellulose dispersion with a mass concentration of 0.1 to 5% (CMC-Na is dispersed in water) 2-10 wt%;

[0020] Polyacrylate adhesive 2-10 wt%;

[0021] Polyoxyethylene ether wetting agent 0.1-0.5 wt%.

[0022] Furthermore, in step 3: the polyolefin-based film is one or more of a PP separator, a PE separator, and a PP / PE composite separator. The coating is carried out on a wire bar coater with a gap of 1-3 μm, and after coating, it is placed in a blast drying oven at 40-80 °C for 20-60 min to obtain a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator.

[0023] The present invention also provides a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator 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 / 60 s, an electrolyte contact angle of 0°, a thermal shrinkage in the MD direction of <1% and in the TD direction of <1% at 150 °C for 1 h, and an ionic conductivity at room temperature of 1-2 mS / cm.

[0024] The present invention further provides a battery (lithium battery or sodium battery), which uses the above separator as an element for separating the positive and negative electrodes, and the battery is a primary battery or a secondary battery.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The battery separator prepared by the present invention by coating a mixed slurry of water-based furan ring-containing bio-based aramid and ceramic on a polyolefin-based film, due to the higher polarity, structural similarity, and stronger interaction between the polar structures such as furan rings, ether bonds, and polyamides and the main organic solvent molecules of the electrolyte, makes the bio-based aramid have better wettability, which is beneficial 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.

[0027] 2. The furan ring-containing bio-based aramid synthesized by the present invention has a decomposition temperature far exceeding that of polyolefin-based films such as PE, and coupled with the excellent heat resistance of inorganic ceramic particles, the prepared separator has excellent thermal dimensional stability, and can achieve a thermal shrinkage in the MD direction of <1% and in the TD direction of <1% at 150 °C for 1 h. The low thermal shrinkage ability can reduce the safety risk of the battery during abnormal heating.

[0028] 3. The innovation of the present invention lies in the selection of bio-based raw materials to synthesize a bifuran diamine monomer with ionic conductivity ability. Specifically, furfurylamine and levulinic acid are selected for an electrophilic addition reaction to obtain an ion-exchange polyamide containing free cation-exchange carboxylic acid (-COOH) groups, so that the prepared separator has excellent ion transport ability and improves the battery efficiency. Description of the Drawings

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 SEM image of the furan-ring-containing bio-based aramid prepared in Example 2 of the present invention.

[0031] Figure 2 SEM image of the furan-ring-containing bio-based aramid / ceramic-coated polyolefin separator prepared in Example 2 of the present invention.

[0032] Figure 3 Comparison chart of the thermal shrinkage performance of the battery separators prepared in each embodiment and comparative example of the present invention at 150 °C for 1 h.

[0033] Figure 4 100-cycle chart of the lithium battery assembled with the battery separators prepared in each embodiment and comparative example of the present invention. Detailed implementation manners

[0034] To more clearly illustrate the present invention, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] Example 1

[0036] In this example, the furan-ring-containing bio-based aramid / ceramic-coated polyolefin separator was prepared according to the following steps:

[0037] Step 1: Synthesize a bio-based bifuran diamine salt with ionic conductivity

[0038] Under ice bath and nitrogen protection conditions, 2 mol of furfurylamine was dropped into 500 mL of concentrated HCL solution, and then 1 mol of levulinic acid was dropped. After the dropping was completed, the reaction was stirred at 60 °C for 3 h. The reactant was cooled to room temperature, and sufficient methanol was added and stirred to precipitate a solid. The precipitate was collected by suction filtration, and the product was dried under vacuum at 80 °C to obtain the bio-based bifuran diamine salt.

[0039] Step 2: Prepare an aqueous furan-ring-containing bio-based aramid solution

[0040] Dissolve the reaction monomers in immiscible solvents respectively: Dissolve 1 mol of bio-based difuran 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 the neutralization reaction to obtain a bio-based difuran diamine solution. Dissolve the diacid monomer (1 mol of FDCl monomer) in 200 mL of CH2Cl2 to obtain a diacid monomer solution.

[0041] Dropwise add the diacid monomer solution to the bio-based difuran diamine solution under high-speed stirring. Solids precipitate continuously during the dropping process, and the dropping is completed after 1 h. Filter the precipitated solids, wash them with deionized water and methanol, and then dry them in vacuo at 100 °C to obtain bio-based aramid containing furan rings; dissolve the obtained bio-based aramid containing furan rings in deionized water at a mass concentration of 5%, add LiOH to adjust the pH = 7, and stir for 2 h to make the aramid in the solution disperse evenly to obtain an aqueous bio-based aramid solution containing furan rings.

[0042] Step 3: Prepare a bio-based aramid / ceramic-coated polyolefin separator containing furan rings

[0043] First, weigh each raw material according to the following mass percentages:

[0044] 15 wt% of the aqueous bio-based aramid solution containing furan rings;

[0045] 75 wt% of a liquid alumina slurry with a mass concentration of 60%;

[0046] 4.5 wt% of a sodium carboxymethyl cellulose dispersion with a mass concentration of 1%;

[0047] 5 wt% of a polyacrylate adhesive;

[0048] 0.5 wt% of a polyethylene oxide ether wetting agent.

[0049] Mix the above raw materials in a beaker and stir with a magnetic stirrer at a speed of 600 rpm for 4 h to obtain a coating slurry with a solid content of about 30%, which is uniform, milky white, and free of impurities. Then coat it on a wire bar coater with a gap of 2 μm, and use a 7-μm commercial polyethylene separator as the coating base film. After coating, dry it in a forced-air oven at 60 °C for 30 min to obtain a bio-based aramid / ceramic-coated polyethylene separator containing furan rings.

[0050] Example 2

[0051] This example prepares a bio-based aramid / ceramic-coated polyolefin separator containing furan rings by the same method as in Example 1, except that: replace the diacid monomer in Step 2 with 0.8 mol of FDCl and 0.2 mol of ODPA.

[0052] Example 3

[0053] This example prepares a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator by the same method as in Example 1, except that: the diacid monomer in Step 2 is replaced with 0.6 mol of FDCl and 0.4 mol of ODPA.

[0054] Example 4

[0055] This example prepares a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator by the same method as in Example 1, except that: the diacid monomer in Step 2 is replaced with 1 mol of ODPA.

[0056] Example 5

[0057] This example prepares a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator by the same method as in Example 1, except that: the diacid monomer in Step 2 is replaced with 0.2 mol of FDCl, 0.2 mol of FDCl, 0.2 mol of IPC, 0.2 mol of TPC, and 0.2 mol of ODPA monomers.

[0058] Example 6

[0059] This example prepares a furan ring-containing bio-based aramid / ceramic-coated polyolefin separator by the same method as in Example 1, except that: 2 mol of furfurylamine in Step 1 is changed to 4 mol of furfurylamine.

[0060] Comparative Example 1

[0061] This comparative example prepares a ceramic-coated polyolefin separator according to the following steps:

[0062] First, weigh each raw material according to the following mass percentages

[0063] 90 wt% of a liquid alumina slurry with a mass concentration of 60%;

[0064] 4.5 wt% of a sodium carboxymethyl cellulose dispersion with a mass concentration of 1%;

[0065] 5 wt% of a polyacrylic acid adhesive;

[0066] 0.5 wt% of a polyoxyethylene ether wetting agent.

[0067] Mix the above raw materials in a beaker and stir with a magnetic stirrer at a speed of 600 rpm for 4 hours to obtain a coating slurry with a solid content of about 30%, which is uniform, milky white, and free of impurities. Then, coat it with a gap of 2 μm on a wire bar coater, and use a 7-μm commercial polyethylene separator as the coating substrate film. After coating, place it in a forced-air oven at 60 °C and dry for 30 min to obtain a ceramic-coated polyethylene separator.

[0068] Comparative Example 2

[0069] A commercial polyethylene separator with a thickness of 7 μm.

[0070] The coated separators obtained in Examples 1 to 6 and the comparative examples were tested. The specific test methods are as follows:

[0071] 1. Thickness test:

[0072] The thickness of the lithium battery separator was tested using a thickness gauge provided by Mahr Company according to the standard of GB / T6672-2001.

[0073] 2. Wettability test:

[0074] The wettability characterization of the coated separator includes the measurement of the contact angle on the surface and the test of the separator wetting rate.

[0075] The contact angle was tested using an optical contact angle meter from Dongguan Shengding with an electrolyte (LiPF6 / (EC, PC, DEC = 1:1:1), the concentration of LiPF6 is 1 mol / L). The volume of each drop was controlled at 3 μL. The dropper was pushed to make the test medium drop on the surface of the test separator, and the camera automatically recorded the whole process and calculated the contact angle.

[0076] The separator wetting rate was measured by dropping 10 μL of electrolyte (LiPF6 / (EC, PC, DEC = 1:1:1), the concentration of LiPF6 is 1 mol / L) on a long strip of filter paper and observing the infiltration distance of the electrolyte after 60 s.

[0077] 3. Porosity test:

[0078] The coated separator and the PE base film were cut into rectangles with a size of 5×5 cm, and the mass m0 of the separator before the test was weighed. Then, the separator was immersed in n-butanol, taken out after standing for 2 h, and the residual n-butanol on the surface of the separator was quickly wiped with non-woven fabric. After weighing, the mass m1 was obtained. The porosity can be calculated according to the following formula:

[0079] In the formula ρ b = 0.81 g / mL, V m is the volume of the coated separator.

[0080] 4. Separator thermal stability test:

[0081] Cut the coated separator and the PE-based film into rectangles with dimensions of 15 cm × 10 cm, and then draw a rectangle with dimensions of 10 cm × 5 cm on their surfaces using a marker pen. Next, use a two-dimensional measuring instrument to measure the length and width of the rectangle before the test. Subsequently, place these separators in a forced-air oven at 150 °C for 1 hour. After that, measure the length and width of the rectangle again. Based on the differences between the two measurement results, calculate the thermal shrinkage rates of the separator in the transverse direction (TD) and the longitudinal direction (MD) within 1 hour respectively:

[0082] MD thermal shrinkage rate = [(initial length - length after thermal shrinkage) / initial length] × 100%;

[0083] TD thermal shrinkage rate = [(initial width - width after thermal shrinkage) / initial width] × 100%.

[0084] 5. Separator ionic conductivity test:

[0085] Use a punching machine to cut the dried coated separator and the PE-based film into discs with a diameter of 19 mm, and measure the thickness using a micrometer. In a glove box, assemble a CR2016 coin cell in the following order: positive electrode case, separator, electrolyte (LiPF6 / (EC, PC, DEC = 1:1:1), concentration of LiPF6 is 1 mol / L), stainless steel sheet, spring piece, and negative electrode case. After the cell is assembled, let it stand at room temperature for 12 hours. Then, select the alternating current impedance mode on an electrochemical workstation, set the amplitude to 5 mV, the frequency range to 0.1 to 10 5 Hz, and the equilibration time to 2 seconds. Based on the EIS spectrum of the test results, obtain the intrinsic resistance R b of the separator, and calculate its ionic conductivity according to the formula:

[0086]

[0087] where: σ is the ionic conductivity (S cm －1 ); L is the thickness of the separator (cm); R b is the intrinsic resistance of the separator (Ω); A is the effective area (cm 2 ).

[0088] 6. Separator mechanical property test:

[0089] Use the universal material testing machine of Shenzhen Sansi Zongheng Company to test each project, and set the speed at 100 mm / min during the test. Cut the diaphragm sample into test strips with a length-width ratio of 200 mm × 15 mm for tensile testing; cut the diaphragm into test strips with a length-width ratio of 80 mm × 30 mm for peel strength testing, and prepare the sample in the order of the sample preparation template, double-sided tape, sample, and transparent tape, and peel the coating through the transparent tape.

[0090] The experimental results are shown in the following table:

[0091]

[0092] Examples 1-6 are battery diaphragms prepared by mixing furan ring-containing bio-based aramid and ceramics and coating them on a PE-based membrane. Comparative Example 1 is a battery diaphragm prepared by coating ceramics on a PE-based membrane, and Comparative Example 2 is a pure PE diaphragm. It can be clearly seen from the data in the table that the wetting rate and contact angle with the electrolyte of the diaphragm added with furan ring-containing bio-based aramid are higher than those of the ceramic diaphragm and the PE-based membrane. This indicates that the infiltration performance of the diaphragm has been effectively improved. Thanks to the polar furan ring, ether bond, and amide bond structures of the furan ring-containing bio-based aramid, which have higher polarity and structural similarity with the main organic solvent molecules of the electrolyte, stronger interactions, and better interfacial compatibility, greatly increasing the contact ability with the electrolyte and effectively improving the wetting performance. In addition, the thermal dimensional stability of the diaphragm added with furan ring-containing bio-based aramid has also been improved. In Examples 1-6, the thermal shrinkage MD < 1% and TD < 1% of the diaphragm at 150 °C for 1 h, while the thermal shrinkage in Comparative Examples 1-2 exceeded 50%. This shows that the excellent heat resistance of the furan ring-containing bio-based aramid plays an important role when added to the diaphragm. Ionic conductivity mainly measures the rate at which ions shuttle through the diaphragm. The detection of ionic conductivity can test the efficiency of the diaphragm in enabling lithium ions to shuttle in the battery. It can be seen from the table that the ionic conductivity of the diaphragm added with furan ring-containing bio-based aramid is significantly increased compared with the ceramic diaphragm and the PE-based membrane. This is because the bifuran diamine structure contains free cation exchange carboxylic acid (-COOH) groups, enabling the diaphragm to have excellent Li + transport ability and effectively improving the battery efficiency. In addition, the addition of furan ring-containing bio-based aramid increases the porosity of the diaphragm, which can increase the ion shuttle channels and thus increase the ionic conductivity of the diaphragm. It should be noted that after the addition of furan ring-containing bio-based aramid, the inorganic ceramic particles are greatly restricted, improving the overall mechanical strength (tensile strength, peel strength) of the diaphragm.

[0093] Figure 1 Figure 15 is the SEM image of the furan ring-containing bio-based aramid prepared in Example 2. It can be seen from the figure that the product has a nanoparticle morphology.

[0094] Figure 2SEM image of the furan - ring - containing bio - based aramid / ceramic - coated polyolefin separator 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.

[0095] Figure 3 Figure for comparing the thermal shrinkage performance of the battery separator 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 does not show obvious thermal shrinkage at 150 °C, while the ceramic separator and the PE separator show obvious thermal shrinkage.

[0096] Figure 4 Figure of 100 - cycle performance (at a rate of 0.5 C) of the lithium batteries assembled with the battery separators prepared in each example and comparative example of the present invention. It can be seen from the figure that after 100 cycles, the batteries assembled with the ceramic separator (Comparative Example 1) and the PE separator (Comparative Example 2) show obvious capacity decay. The discharge specific capacity of the PE - separator battery before and after 100 cycles drops from 145 mAh / g to 97 mAh / g, and the capacity retention rate is 66.9%. The discharge specific capacity of the ceramic - separator battery before and after 100 cycles drops from 145 mAh / g to 126 mAh / g, and the capacity retention rate is 86.9%. While the battery assembled with the furan - ring - containing bio - based aramid / ceramic - coated polyethylene separator (Example 2) shows better cycle stability. The initial and final discharge specific capacities of the battery are 147.8 mAh / g and 147.7 mAh / g respectively, and the capacity retention rate is as high as 99.9%. The coulombic efficiencies of the batteries using the ceramic and PE separators also decay significantly after 100 cycles, being 84.2% and 64.9% respectively, while the coulombic efficiency of the battery assembled with the furan - ring - containing bio - based aramid / ceramic - coated polyethylene separator reaches 98.5%, showing excellent cycle stability.

[0097] In summary, in the present invention, a polyolefin separator is used as the substrate, and a furan - ring - containing bio - based aramid / ceramic material is coated on the surface of the substrate. The carboxyl groups with ion - exchange ability in the diamine monomer of the furan - ring - containing bio - based aramid improve the ionic conductivity of the separator; 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 separator and the electrolyte, facilitate the diffusion of the electrolyte, and improve the wettability of the separator. The furan - ring - containing bio - based aramid / ceramic - coated polyolefin separator combines the excellent heat - resistant properties of the ceramic and polyamide structures. The prepared battery separator improves the heat - resistant property and electrolyte wettability of the polyolefin - based membrane, effectively improves the electrochemical performance and cycle life ability of lithium / sodium batteries, and broadens the application field and application prospect of aramid separators in lithium / sodium batteries.

[0098] In the embodiments of the present invention, all numerical specifications (such as temperature, time, concentration, weight, etc., including the ranges of each of them) can generally be approximate values that can be appropriately changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications can be understood as being preceded by the term "about".

[0099] The above provides 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 equivalent substitution that can be made by those skilled in the art without creative efforts 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: Synthesis of bio-based bisfuran diamine salt with ion conductivity: 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; 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: The bio-based bisfuran diamine salt is dissolved in water, a base containing Li or Na is added for the first time to adjust the pH value to be alkaline, and then stirred for 2 to 6 hours for neutralization reaction to obtain a bio-based bisfuran diamine solution; the diacid monomer is dissolved in an organic solvent, and the organic solvent is immiscible with water to obtain a diacid monomer solution; Under stirring conditions, a diacid monomer solution is added dropwise to a bio-based bisfuran diamine solution, and the precipitated solid is filtered, washed, and vacuum dried to obtain a furan ring-containing bio-based aramid fiber; the furan ring-containing bio-based aramid fiber is dissolved in deionized water at a mass concentration of 5-20%, and a base containing Li or Na is added for a second time to adjust the pH to 7-8 to obtain an aqueous furan ring-containing bio-based aramid fiber 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: In step 1, the furfurylamine and levulinic acid are both derived from biological raw materials, and the molar ratio is 2-8:

1.

3. The preparation method according to claim 1, characterized in that: In step 2, 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.

4. The preparation method according to claim 1, 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.

5. 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%.

6. 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.

7. A furan ring-containing bio-based aramid / ceramic-coated polyolefin diaphragm prepared by the preparation method described in any one of claims 1 to 6.

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

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