PEF / pbs composite film material and preparation method and application thereof

Abstract

This invention discloses a PEF / PBS composite membrane material, its preparation method, and its applications, belonging to the fields of bio-based polymer membrane materials and energy storage technology. The invention first mixes PEF, PBS, and a compatibilizer ADR-4468 and reacts them in a molten state to obtain a PEF / PBS composite material. The PEF / PBS composite material is then formed into sheets and subjected to biaxial stretching to prepare the PEF / PBS composite membrane material. Finally, the obtained PEF / PBS composite membrane material is dissolved and etched with chloroform, then compacted and dried to obtain a PEF / PBS composite battery separator. The PEF / PBS composite membrane material prepared by this invention exhibits excellent electrical and mechanical properties. Furthermore, it is based on bio-based raw materials, meeting green and environmentally friendly requirements, and is a good alternative to petroleum-based separator materials. In addition, the preparation method provided by this invention is simple and has minimal environmental impact.

Description

Technical Field

[0001] This invention belongs to the field of bio-based polymer membrane materials and energy storage science and technology, specifically relating to a PEF / PBS composite membrane material, its preparation method and application. Background Technology

[0002] Polyethylene 2,5-furandicarboxylate (PEF) is a bio-based material that has gained increasing attention over the past decade due to its excellent barrier properties and relatively good processability. However, its drawbacks are also quite significant: its tensile strength and modulus are too high, while its ductility is too low. Although it has a structure similar to polyethylene terephthalate (PET), its properties differ considerably. Because of this, it cannot meet the basic performance requirements of battery separators when used alone.

[0003] Commercial battery separators are made primarily of polyolefins, with a basic structure consisting of single-layer or multilayer composite membranes made of polypropylene and polyethylene. Due to their low cost, high strength, and stable electrochemical performance, they have dominated the market since their invention. However, existing commercial polyolefin separators have low porosity and poor electrolyte wettability, which limits their application in high-rate configurations.

[0004] In recent years, numerous novel battery separators have emerged, such as PET, polyimide, polyamide, poly(p-phenylenebenzodiazole), polyvinylidene fluoride, and polyetheretherketone (PEEK). Each separator has its own advantages and disadvantages in terms of development methods and properties. Based on pore-forming methods, they can be categorized as: dry stretching, wet phase transformation, electrospinning, inorganic particle filling / removal, and in-situ polymerization to form a conductive / porous network. Research indicates that electrospinning is currently the most commonly used preparation method in research. Compared to the dry stretching method used in commercial separators, while it offers superior porosity, wettability, and flexible structural design, its lower production efficiency and higher cost significantly limit its commercial development. Furthermore, polyolefin separators are derived from petroleum-based polymers and are non-renewable petroleum-based polymers.

[0005] To address the various drawbacks mentioned above, providing a battery separator that is simple to process, has excellent performance, and is bio-based is a major task for researchers in the field of energy storage science and technology. Summary of the Invention

[0006] The purpose of this invention is to provide a PEF / PBS composite membrane material, its preparation method, and its applications. The main matrix of the provided PEF / PBS composite membrane material, PEF and polybutylene succinate (PBS), are synthesized from plant seeds (starch / sugar), tubers (sucrose), straw (cellulose), sawdust (lignocellulose), and glycerol (a vegetable oil byproduct) through various chemical methods. According to known research, the synthesis routes of both have entered the industrial production stage. In the foreseeable future, both will achieve low cost, high yield, easy control, large-scale production, and high stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is to provide a method for preparing a PEF / PBS composite material, comprising the following steps: Poly(2,5-furandicarboxylate), polybutylene succinate, and compatibilizer ADR-4468 were mixed and reacted in the molten state to obtain a PEF / PBS composite material.

[0008] The epoxy groups of compatibilizer ADR-4468 undergo ring-opening reactions with the end groups of PEF and / or PBS molecular chains, thereby forming chain amplification / branching or grafting structures to improve the compatibility and toughness of the blend system.

[0009] Preferably, the mass ratio of the polyethylene 2,5-furandicarboxylate to the polybutylene succinate is (1~9):1.

[0010] More preferably, the mass ratio of the polyethylene 2,5-furandicarboxylate to the polybutylene succinate is 3:2.

[0011] Preferably, the amount of compatibilizer ADR-4468 added is 2.0% of the total mass of polyethylene 2,5-furandicarboxylate and polybutylene succinate.

[0012] Preferably, the reaction is carried out at a temperature of 230°C for 6.5 minutes.

[0013] The second technical solution of the present invention is to provide a PEF / PBS composite material prepared according to the above-mentioned preparation method of PEF / PBS composite material.

[0014] The third technical solution of the present invention provides a method for preparing a PEF / PBS composite membrane material, comprising the following steps: The above-mentioned PEF / PBS composite material is made into a sheet, and then the sheet is subjected to biaxial stretching treatment to obtain the PEF / PBS composite membrane material.

[0015] Alternatively, the process of forming the PEF / PBS composite into sheets may include casting or casting.

[0016] Preferably, the thickness of the sheet is 170~230μm.

[0017] Preferably, the biaxial stretching temperature is 125°C, the stretching rate is 1 mm / s, and the stretching ratio is 3.0~3.3.

[0018] In this invention, the stretching ratio of biaxial stretching is the biaxial (MD and TD) synchronous stretching ratio.

[0019] The fourth technical solution of the present invention provides a PEF / PBS composite membrane material prepared according to the above-mentioned preparation method of PEF / PBS composite membrane material.

[0020] Fifth technical solution of the present invention: A method for preparing a PEF / PBS composite battery separator, comprising the following steps: The above-mentioned PEF / PBS composite membrane material was immersed in a chloroform solution for dissolution and etching. After removal, it was compacted and dried to obtain the PEF / PBS composite battery separator.

[0021] The sixth technical solution of the present invention: provides a PEF / PBS composite battery separator prepared according to the above-mentioned preparation method of PEF / PBS composite battery separator.

[0022] The seventh technical solution of the present invention provides an application of the above-mentioned PEF / PBS composite battery separator in lithium-ion battery assembly.

[0023] This invention establishes a graft structure between PEF and PBS using ADR-4468, resulting in a blend with significantly higher mechanical properties than either PEF or PBS alone. Furthermore, a lithium-ion battery separator with superior electrical performance can be obtained through a simple biaxial stretching and chloroform dissolution etching process.

[0024] The beneficial technical effects of the present invention are as follows: The PEF / PBS composite membrane material prepared by this invention has excellent electrical and mechanical properties.

[0025] The PEF / PBS composite membrane material prepared by this invention, which is mainly based on bio-based materials, meets the requirements of green environmental protection and is a good alternative to petroleum-based membrane materials.

[0026] The raw materials used in this invention have a bio-based content of approximately 98%, which meets the requirements of green and environmentally friendly practices. Moreover, the process is simple and has little impact on the environment.

[0027] This invention leverages the excellent compatibility of PEF and PBS bio-based materials and employs a simple preparation method to achieve the goal of preparing battery separators. Furthermore, the bio-based battery separator prepared by this invention not only solves the problem of unsustainable development of commercial polyolefin separators but also reduces the carbon footprint and can gradually replace commercial polyolefin separators.

[0028] The PEF / PBS composite battery separator prepared by this invention is derived from biomass monomers, possessing green, environmentally friendly, and non-toxic characteristics, and is also a good alternative to modern commercial lithium-ion battery separators. It can be directly applied to the field of energy storage battery materials, and can also solve the problem of petroleum-based sourcing for commercial separators, which is of positive significance for broadening the application of PEF and commercial lithium batteries. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The structural formulas for ADR-4468, PEF, and PBS are given.

[0031] Figure 2 This is a schematic diagram showing the connection relationship between ADR-4468, PEF, and PBS in the PEF / PBS composite membrane material.

[0032] Figure 3 FTIR spectra of unetched PEF 64 (Post-BO), etched PEF 64 (Post-etch), PEF, and PBS prepared in Example 1.

[0033] Figure 4 This is a schematic diagram of the biaxial stretching process of PEF 64 prepared in Example 1.

[0034] Figure 5 This is a physical image of PEF 64 prepared in Example 1.

[0035] Figure 6 The DSC curves of the PEF / PBS composite membrane materials and raw materials prepared in Example 1 and Comparative Examples 1-4 are shown, where (a) is the first heating and (b) is the first cooling.

[0036] Figure 7 The images shown are SEM images of PEF 64 prepared in Example 1, where (a) is a cross-sectional SEM image, and (b) and (c) are surface SEM images at different magnifications.

[0037] Figure 8 The mechanical property test results of the PEF / PBS composite membrane materials and raw materials prepared in Examples 1 and Comparative Examples 1-4 are shown, where (a) is tensile strength, (b) is elongation at break, and (c) is tensile modulus.

[0038] Figure 9 TGA curves of the PEF / PBS composite membrane materials and raw materials prepared in Example 1 and Comparative Examples 1-4.

[0039] Figure 10 The images show the XRD patterns of PEF 64 before biaxial stretching (Pre-BO), after biaxial stretching (Post-BO), after etching (Post-etch), and PEF and PBS in Example 1.

[0040] Figure 11 The images shown are SEM images of the PEF 64 battery separator prepared in Example 2, where (a) is a cross-sectional SEM image, and (b) and (c) are surface SEM images at different magnifications.

[0041] Figure 12 The wettability test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator.

[0042] Figure 13 The water contact angle between the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator.

[0043] Figure 14 The porosity test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown.

[0044] Figure 15 Liquid absorption rate test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator.

[0045] Figure 16 DSC curves of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator.

[0046] Figure 17 The results of thermal dimensional stability tests on the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown.

[0047] Figure 18 The LSV curves are for lithium-ion batteries assembled with the PEF 64 battery separator prepared in Example 2 or the commercial Celgard 2400 separator.

[0048] Figure 19 The interfacial impedance spectrum (a) and the ionic conductivity curve (b) of the assembled symmetrical steel sheet lithium-ion battery are obtained by interfacial impedance testing of the symmetrical lithium-ion battery assembled with the PEF 64 battery separator prepared in Example 2 or the commercial Celgard 2400 separator.

[0049] Figure 20 The ion mobility number test results are for lithium-ion batteries assembled with commercial Celgard 2400 separator (a) or PEF 64 battery separator prepared in Example 2 (b). Detailed Implementation

[0050] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0051] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0052] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0053] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] The sources of the raw materials used in this invention are as follows: Polyethylene 2,5-furandicarboxylate (PEF, which is polymerized from 2,5-furandicarboxylicacid and ethylene glycol, with a content of diethylene glycol (<2%), viscosity of 0.875 dL / g, brand name 20240401) was purchased from Hubei Huiheyuan Chemical Co., Ltd., China. Polybutylene succinate (PBS, which is polymerized from succinic acid and 1,4-butanediol, Mw=88 kg / mol, brand name 1001MD) was purchased from Showa Denko Corporation, Japan. Joncryl ® ADR-4468 (which is polymerized from glycidyl methacrylate (GMA), styrene, methyl methacrylate (MMA), cyclohexyl acrylate (CHA), etc., with an epoxy equivalent of 310 g / mol, Mw=7.3 kg / mol, and the grade name is 4468) was purchased from Zhejiang Junke New Materials Co., Ltd., China. Chloroform (CHCl3, purity: 99.7%, density: 1.48 g / cm³) 3 Purchased from China Jingchun Reagent Co., Ltd.

[0056] The structural formulas for ADR-4468, PEF, and PBS are shown below. Figure 1 .

[0057] The characterization method used in this invention for the obtained product is as follows: (1) Fourier transform infrared spectroscopy (FTIR) was measured on a NICOLET iS50 instrument (Thermo Fisher Scientific, USA) with a resolution of 0.09 cm⁻¹. -1 The scanning frequency is 32, and the range is 400~2000 cm. -1 .

[0058] (2) Thermal stability was measured by thermogravimetric analysis (TGA) on STA 7200 (Hitachi, Japan). Specifically, under nitrogen purging conditions, the heating rate was 20 °C / min, the measurement temperature range was 30~600 °C, and the weight loss rate of the battery separator and its precursor film as the temperature increased was recorded.

[0059] (3) Differential scanning calorimetry (DSC) characteristics were measured using a DSC 7020 (Hitachi, Japan). Specifically, under nitrogen purging conditions, the first heating rate was 20 °C / min and the first cooling rate was 10 °C / min. These were used to record the DSC characteristics of the battery separator precursor and the battery separator.

[0060] (4) The microstructure was characterized by field emission scanning electron microscopy (SEM) (Zeiss, Germany) to measure its surface / section.

[0061] (5) The mechanical properties were obtained by testing the CMT 6104 microcomputer-controlled electronic universal testing machine (Mester Industries, USA).

[0062] (6) Battery separator liquid absorption rate test: First, cut and prepare a circular separator sample with a diameter of 16 mm and record the initial mass. Then, immerse the sample in sufficient electrolyte. Every 10 min, place the separator between two dry filter papers and place a 20 g weight on top to apply pressure so that it can fully absorb the remaining electrolyte on the surface. After 10 s, calculate the difference in mass before and after.

[0063] (7) The porosity of the battery separator with bio-based material as the main body was determined by weighing on an analytical balance. The 16 mm separator was soaked in n-butanol for 20 min, and 8 sets were measured to calculate the average value. After absorbing the solution on the surface of the separator with filter paper, it was weighed on the balance.

[0064] (8) The wettability of the battery separator was determined by filming the area of ​​electrolyte droplets on the separator 1 second after they were dropped into it using a video camera, and the sample was measured using ImageJ software. Its contact angle characteristics were measured using a contact angle measuring instrument.

[0065] Example 1 Preparation of PEF / PBS composite membrane material: PEF and PBS were mixed at a mass ratio of 6:4, and 2.0% (by mass) of ADR-4468 (based on the total mass of PEF and PBS) was added. The mixture was melt-blended at 230 °C for 6.5 min. The resulting blend was then cast into sheets using a press (temperature 220 °C, casting pressure 900 t / m). 2 The sheet was then subjected to biaxial stretching (stretching temperature 125 ℃, stretching rate 1 mm / s, stretching ratio 3.0) to obtain a PEF / PBS composite membrane material (named PEF 64).

[0066] Comparative Example 1 Compared with Example 1, the only difference is that the mass ratio of PEF and PBS is adjusted to 9:1, and the resulting PEF / PBS composite membrane material is named PEF 91.

[0067] Comparative Example 2 Compared with Example 1, the only difference is that the mass ratio of PEF and PBS is adjusted to 8:2, and the resulting PEF / PBS composite membrane material is named PEF 82.

[0068] Comparative Example 3 Compared with Example 1, the only difference is that the mass ratio of PEF and PBS is adjusted to 7:3, and the resulting PEF / PBS composite membrane material is named PEF 73.

[0069] Comparative Example 4 Compared with Example 1, the only difference is that the mass ratio of PEF and PBS is adjusted to 5:5, and the resulting PEF / PBS composite membrane material is named PEF 55.

[0070] A schematic diagram illustrating the connection relationship between ADR-4468, PEF, and PBS in the PEF / PBS composite membrane material is shown below. Figure 2 .

[0071] The FTIR spectra of unetched PEF 64 (Post-BO), etched PEF 64 (Post-etch), PEF, and PBS prepared in Example 1 are shown below. Figure 3 .

[0072] Depend on Figure 3 It can be seen that the terminal carboxyl groups of PEF and PBS undergo ring-opening reactions with the epoxy groups of ADR, forming ester bonds and hydrogen bonds. Compared with pure PEF and PBS, 954 cm⁻¹ was found in PEF 64 before and after etching. -1 875cm -1 All showed a furan ring vibration peak at 1263.23 cm⁻¹. -1 The -COC- stretching vibration signal peak of PBS appears; after the addition of PBS, the carbonyl C=O stretching vibration peak is formed, starting from 1713.0 cm⁻¹. -1 The redshift reached 1711.4 cm. -1 This can be considered as the formation of hydrogen bonds; PBS at 795 cm -1 It has a strong peak effect and is a fingerprint characteristic peak of the -CH out-of-plane bending vibration of PBS.

[0073] A schematic diagram of the biaxial stretching process of PEF 64 prepared in Example 1 is shown below. Figure 4 The actual image of the prepared PEF 64 is shown below. Figure 5 .

[0074] The DSC curves of the PEF / PBS composite membrane materials and raw materials prepared in Examples 1 and Comparative Examples 1-4 are shown below. Figure 6 (a) represents the first temperature increase, and (b) represents the first temperature decrease.

[0075] SEM image of PEF 64 prepared in Example 1 is shown below. Figure 7 Among them, (a) is a cross-sectional SEM image, and (b) and (c) are surface SEM images at different magnifications.

[0076] The mechanical property test results of the PEF / PBS composite membrane materials and raw materials prepared in Examples 1 and Comparative Examples 1-4 are shown in the figure. Figure 8 , where (a) is tensile strength, (b) is elongation at break, and (c) is tensile modulus.

[0077] from Figure 4 , 5 Observations showed that the blend and its biaxially stretched PEF 64 were generally light yellow, with PEF and PBS interwoven. According to... Figure 6 The DSC curve in (a) shows that with the first heating, the overall crystallinity of the blend gradually decreases with the increase of PBS, most notably in PEF 55 (melting peak at approximately 160-200℃). However, the addition of a small amount of PBS increases the crystallinity of PEF in the system, possibly because the small amount of PBS induces heterogeneous nucleation and crystallization. The increased crystallinity of PBS (PEF 55) in the system is likely due to the interaction between molecules through hydrogen bonds. Figure 6 In the first cooling DSC curve of (b), it can be seen that the low PBS content leads to two independent crystallization phases in the blend system, with PEF 82 and PEF 73 being the most prominent (crystallization peaks at approximately 120-140℃). The interaction between the PBS and PEF molecular chains, and the mutual compression and inhibition between PBS and other rigid furan rings, result in interlamellar crystallization, reducing the size of PBS spherulites and causing a significant decrease in the crystallinity of the composite material at low temperatures. Simultaneously, through... Figure 7 The SEM image results also show that PEF 64 has a smooth and flat surface and a tight cut surface; this is consistent with... Figure 8 Compared to pure PEF, the introduction of PBS results in a significant improvement in the overall mechanical properties of PEF 64 (approximately 300%).

[0078] The TGA curves of the PEF / PBS composite membrane materials and raw materials prepared in Examples 1 and Comparative Examples 1-4 are shown below. Figure 9 Each sample T 5% and T 90% See Table 1.

[0079] Table 1 Thermal decomposition temperatures of PEF / PBS composite membrane materials and raw materials As shown in Table 1 and Figure 9 According to thermogravimetric analysis, the entire mixture undergoes a one-step decomposition without any signs of secondary decomposition. The increased PBS content enhances the overall thermal stability of the blend. PEF 64 reaches 360.5℃ at a 5% weight loss, which lays the foundation for the preparation of the battery separator.

[0080] The XRD patterns of PEF 64 before biaxial stretching (Pre-BO), after biaxial stretching (Post-BO), and after etching (Post-etch) in Example 1, as well as those of PEF and PBS, are shown below. Figure 10 Meanwhile, the changes in the lattice peak positions before and after are summarized in Table 2.

[0081] Table 2. X-ray diffraction patterns of unetched PEF 64 before biaxial stretching (Pre-BO), unetched PEF 64 before and after biaxial stretching (Post-BO), etched PEF 64 (Post-etch), and PEF and PBS. according to Figure 10 A comprehensive analysis with Table 2 reveals that due to the slow crystallization of PEF, no crystallization peaks were detected. The three peaks (0, 2, 0), (0, 2, 1), and (1, 1, 0) in Table 1 all represent the α-crystal form of PBS. Specifically, from (0, 2, 0), we can deduce the stacking of molecular chains along the b-axis of the crystal. The fact that this crystal plane direction remains almost unchanged indicates that the stretching has minimal impact on this direction before and after etching, meaning the spacing remains essentially consistent. The (0, 2, 1) crystal plane of the unetched PEF 64 shifted from 23.40° to 22.64° (a shift of -0.76°), indicating that the stretching of the molecular chains caused orientation changes, i.e., elongation along the b-axis, which increased the spacing between the oblique crystal planes. After etching, the crystal plane is 23.46° (a recovery of 0.82°), which may be due to the solvent causing chain recovery. The (1,1,0) crystal plane is perpendicular to the crystal ab plane. This means that when the unetched PEF 64 is biaxially stretched, the film is stretched in the plane, compressing the intercrystalline spacing in the vertical direction. After etching, although there is some backtracking, the resulting change in the stretched crystal is only 10% (from 26.92° to 26.76°). This indicates that the overall structure is significantly compressed, and the etching process has little impact. In summary, the PBS structure within the polyester undergoes a significant shift, resulting in obvious dispersion. This directly proves that the system design for reducing polyester molecular aggregation has achieved its intended purpose.

[0082] Example 2 Preparation of PEF / PBS composite battery separator: The PEF 64 prepared in Example 1 was immersed in a chloroform bath with a stirrer for 40 min to precipitate unreacted PBS from the membrane, resulting in the formation of micropores of a certain size on the membrane surface and inside (the average micropore diameter on the surface is about 50~150 nm). After being compacted and dried with a heavy object (the weight of the compacted object was 15 kg; the drying temperature was 50 ℃ and the time was 48 h), a PEF / PBS composite battery separator (named PEF 64 battery separator) was obtained.

[0083] SEM image of the PEF 64 battery separator prepared in Example 2 is shown below. Figure 11 Among them, (a) is a cross-sectional SEM image, and (b) and (c) are surface SEM images at different magnifications.

[0084] pass Figure 11 It was found that PEF 64, through chloroform etching and filtration processes, creates micropores of a certain size (50~150nm) on the membrane surface and inside.

[0085] The wettability test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown in the figure. Figure 12 .

[0086] The water contact angles of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown in Figure 2. Figure 13 .

[0087] pass Figure 12 and 13 Physical performance tests of the separator revealed that the PEF 64 battery separator exhibits excellent electrolyte wettability, with an electrolyte spread area of ​​88.141 mm² on the PEF 64 battery separator. 2 It accounts for 43.86% of the total, and its area unfolded on the Celgard 2400 diaphragm is 12.371 mm². 2 The percentage of water contact angles was 6.16%, which is attributed to the unique porous structure formed by the etching process, resulting in a capillary adsorption effect. The contact angle test results showed that the water contact angle of the PEF 64 battery separator was 14.53°, and the water contact angle of the Celgard 2400 separator was 44.14°, which also indirectly confirms that the etching process of this invention forms a unique porous structure, thereby generating a capillary adsorption effect.

[0088] The porosity test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown in the figure. Figure 14 .

[0089] The liquid absorption rate test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown in the figure. Figure 15 .

[0090] from Figure 14 It can be seen that the porosity of the PEF 64 battery separator is 77.8%, which is much higher than the 46.7% porosity of the Celgard 2400 separator; through Figure 15 It can be observed that the PEF 64 battery separator has a liquid absorption rate that is more than 4 times higher than that of the Celgard 2400 separator, which creates favorable conditions for the ion transport performance of the subsequent lithium-ion battery.

[0091] The DSC curves of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown in the figure. Figure 16 .

[0092] The thermal dimensional stability test results of the PEF 64 battery separator prepared in Example 2 and the commercial Celgard 2400 separator are shown in the figure. Figure 17 .

[0093] pass Figure 16 It was found that the Celgard 2400 membrane exhibited a significant melting peak at 165.4℃, which is consistent with the apparent experimental results ( Figure 17 The results are consistent; however, due to the slow crystallization of PEF, the melting temperature of the PEF 64 battery separator could not be measured, but it can be seen that it remains stable at 140℃.

[0094] Example 3 Application of PEF 64 battery separator in lithium-ion batteries: The PEF 64 battery separator prepared in Example 2 or the commercial Celgard 2400 separator was cut into 16 mm round pieces, which were then sandwiched between different types of half-cells and full cells for assembly. The relevant performance was then tested as follows: Electrochemical stability window test: using steel sheet (anode) / diaphragm / lithium sheet (cathode) (pressure 50 kg / cm²) 2 A battery was constructed using an electrochemical workstation (CHI, USA) and an anodic linear voltammetric scan method was employed. The scan potential range was 1.5–6 V, and the scan rate was 0.002 V / s, in order to test the electrochemical stability window of the separator.

[0095] Interfacial impedance testing: using lithium sheet (anode) / diaphragm / lithium sheet (cathode) (pressure 50 kg / cm²). 2 A battery was constructed using an electrochemical workstation (CHI, USA) at a temperature of 0.1~10. 6 The interface impedance between the diaphragm and the electrode was tested within a scanning frequency range of Hz, with the sinusoidal amplitude set to 5 mV.

[0096] Ion conductivity test: using steel sheet (anode) / diaphragm / steel sheet (cathode) (pressure 50 kg / cm²) 2 A battery was assembled using an electrochemical workstation (CHI, USA), and the battery was tested at temperatures ranging from 0.1 to 10. 6 An AC impedance scan was performed within a frequency range of Hz, with a sinusoidal amplitude of 5 mV, and the resistance of the diaphragm was measured. R b .

[0097] Ion transport number test: using lithium sheet (anode) / diaphragm / lithium sheet (cathode) (pressure 50 kg / cm²) 2 To assemble a battery, test Li + migration number t Li + After assembling the lithium-symmetric battery, the initial impedance of the battery was measured using an electrochemical workstation (CHI, USA). R 0. After applying a constant voltage polarization of 0.01 V to the battery, the change in current over time is recorded. The initial polarization current is obtained. I 0, and record the current value after polarization. I s Subsequently, the impedance value after polarization was determined. R s Measurement.

[0098] The LSV curves of lithium-ion batteries assembled with the PEF 64 battery separator prepared in Example 2 or the commercial Celgard 2400 separator are shown in Figure 2. Figure 18 .

[0099] pass Figure 18 It can be seen that the PEF 64 battery separator exhibits stable current performance in the 3.0 V to 4.2 V range, indicating electrochemical stability within this range. Starting from 4.5 V, the current gradually increases, indicating that the material begins to undergo oxidation (decomposition or side reactions). At 6.0 V, the current reaches approximately 45 μA, indicating that the oxidation reaction intensifies. Compared to the Celgard 2400 separator, the oxidation and decomposition of the PEF 64 battery separator is gradual, without severe breakdown. This may be because the PEF 64 battery separator has certain passivation capabilities or interfacial stability, making it suitable for medium- to high-voltage systems and beneficial for further suppressing side reactions when combined with electrolyte additives or surface coatings.

[0100] The interfacial impedance spectra (a) of symmetrical lithium-ion batteries assembled using the PEF 64 battery separator prepared in Example 2 or the commercial Celgard 2400 separator, and the ionic conductivity curve (b) of the assembled symmetrical steel sheet lithium-ion batteries are shown in the figure. Figure 19 .

[0101] Depend on Figure 19As shown in (a), the interfacial charge transfer impedance of the PEF 64 battery separator is significantly lower than that of the Celgard 2400 separator. The interfacial impedance of PEF 64 is 219Ω, while that of Celgard 2400 is 348Ω. This indicates that PEF 64 has better interfacial compatibility between the electrode and the separator, resulting in better ion transport capability and lower interfacial resistance inside the battery. This is beneficial for improving the rate performance and cycle stability of the battery. Figure 19 Figure (b) shows that the bulk resistance (Rs) of Celgard 2400 and PEF 64 measured at 25°C are 5.79 Ω and 21.8 Ω, respectively; according to calculations, the conductivity of Celgard 2400 and PEF 64 are 1.72 × 10⁻⁶ Ω, respectively. -4 S·cm -1 and 2.74 × 10 -4 S·cm -1 This indicates that PEF 64, with its high porosity and electrolyte absorption rate, has a significantly higher ion transfer capacity than Celgard 2400, providing a good matrix for the high lithium-ion migration capability of PEF 64.

[0102] The ion mobility number test results of lithium-ion batteries assembled using either the commercial Celgard 2400 separator (a) or the PEF 64 battery separator prepared in Example 2 (b) are shown in the figure. Figure 20 .

[0103] from Figure 20 It can be seen that the Li of Celgard 2400 and PEF 64 membranes... + Number of migrations (t) Li + The values ​​were 0.34 and 0.47, respectively. The PEF64 membrane's (t) Li + The electronegativity is slightly higher than that of the PP membrane. This may be because the furan functional groups on PEF 64 have a higher electronegativity towards Li. + It has a strong adsorption capacity, which can promote the escape of Li from the solvent shell, leading to (t Li + It is higher than that of PP diaphragm.

[0104] In summary, this invention prepares a PEF 64 battery separator with bio-based materials using bio-based PEF and PBS as raw materials. The effectiveness of this separator was compared with that of the widely used commercial Celgard 2400 separator in the prior art. The results show that the PEF 64 battery separator, manufactured using a simple process, exhibits performance comparable to, and even surpasses, the commercial Celgard 2400 separator in most aspects. This provides a solid foundation for subsequent separator manufacturing, and the PEF 64 battery separator has significant development potential.

[0105] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a PEF / PBS composite battery separator, characterized in that, Includes the following steps: The PEF / PBS composite membrane material was immersed in a chloroform solution for dissolution and etching. After being removed, it was compacted and dried to obtain the PEF / PBS composite battery separator. The preparation steps of the PEF / PBS composite membrane material include: making the PEF / PBS composite material into a sheet, and then subjecting the sheet to biaxial stretching treatment to obtain the PEF / PBS composite membrane material; The thickness of the sheet is 170~230μm; the biaxial stretching temperature is 125℃, the stretching rate is 1mm / s, and the stretch ratio is 3.0~3.3; The preparation steps of the PEF / PBS composite material include: mixing polyethylene 2,5-furandicarboxylate, polybutylene succinate and compatibilizer ADR-4468 and reacting them in a molten state to obtain the PEF / PBS composite material; The mass ratio of the polyethylene 2,5-furandicarboxylate to the polybutylene succinate is (1~9):1; the amount of compatibilizer ADR-4468 added is 2.0% of the total mass of the polyethylene 2,5-furandicarboxylate and the polybutylene succinate; the reaction temperature is 230℃ and the time is 6.5min.

2. A PEF / PBS composite battery separator prepared by the method described in claim 1.

3. The application of the PEF / PBS composite battery separator as described in claim 2 in lithium-ion battery assembly.

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