Diaphragm based on towel gourd fiber, preparation method, electrochemical device and electronic device

Abstract

The invention belongs to the technical field of electrochemistry, and provides a loofah fiber-based diaphragm, a preparation method, an electrochemical device and an electronic device in order to solve the problems of poor thermal stability, poor electrolyte affinity, insufficient sustainability, high cost and the like of an existing diaphragm material. The method comprises the following steps: S1, selecting mature loofah with excellent texture, and removing skin and seeds to obtain loofah sponge fibers; s2, pretreating loofah sponge fibers to obtain loofah sponge fibers; s3, dispersing loofah fibers in water, and drying to obtain an unmodified loofah fiber diaphragm; and S4, adding a modifier into the unmodified loofah fiber diaphragm for modification to obtain the loofah fiber-based diaphragm. The loofah fiber-based diaphragm provided by the invention has good electrolyte affinity and mechanical strength, and the electrochemical device prepared from the loofah fiber-based diaphragm has excellent electrochemical performance.

Description

Technical Field

[0001] The invention belongs to the field of electrochemical technology, and in particular relates to a membrane based on loofah fibers, a preparation method, an electrochemical device and an electronic device. Background Art

[0002] In the field of battery separators, as a key component of batteries, their performance plays a decisive role in the overall performance of the battery. Currently, the most widely used battery separators in the market mainly include glass fiber separators, polyolefin separators, and some separators based on other natural or synthetic materials.

[0003] Currently, glass fiber (GF) separators are commonly used as separators due to their commercial availability and desirable high porosity, inertness, and hydrophilicity. These GF membranes consist of interconnected, randomly oriented borosilicate fibers that are held together by friction, adhesion, and cohesion. However, the randomly oriented fiber arrangement results in a complex pore structure and a relatively high pore size distribution, which reduces the uniformity of the electric field, leading to increased heterogeneous Zn deposition and dendrite formation. Furthermore, the mechanical strength of GF separators is low, making them susceptible to Zn deposition. 2+ Dendrite penetration caused by uneven transport and deposition.

[0004] Polyolefin separators, such as polyethylene (PE) and polypropylene (PP), have captured a significant market share thanks to their mature manufacturing processes. However, their poor thermal stability is a significant issue. During battery use, especially in high-temperature environments (e.g., exceeding 80°C) or when the battery experiences abnormal conditions such as thermal runaway, PE and PP separators are prone to thermal shrinkage. This thermal shrinkage can increase the separator's pore size, alter its porosity, and even reduce the distance between the positive and negative electrodes, easily leading to short circuits. This seriously threatens battery safety and limits its performance and safety in high-temperature or high-power applications. Furthermore, polyolefin separators have poor compatibility with common electrolytes, such as carbonates. Furthermore, the raw materials used in polyolefin separators are derived from petrochemicals, a non-renewable resource. As these resources gradually deplete, their supply faces challenges. Furthermore, the production process for polyolefin separators involves multiple complex chemical reactions, consumes significant amounts of energy, and generates significant amounts of industrial wastewater, exhaust gas, and solid waste, causing significant environmental pollution.

[0005] Some studies have attempted to use natural fibers, such as cotton fibers and hemp fibers, to prepare separators. These natural fibers usually undergo simple pretreatment, such as cleaning and degumming, and are then made into separators using papermaking processes or other molding methods. Although natural fibers such as cotton fibers and hemp fibers have the advantages of being renewable and environmentally friendly, their mechanical properties are insufficient. Moreover, the pore structure of these natural fiber separators is often less than ideal. The pore size is uneven and the distribution is unreasonable, which is not conducive to the efficient conduction of ions. In addition, the instability of the pore structure may also cause changes in the performance of the separator during the battery charging and discharging process, affecting the cycle stability of the battery. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a membrane based on loofah fiber, a preparation method, an electrochemical device and an electronic device.

[0007] A first object of the present invention is to provide a method for preparing a membrane based on loofah fiber, comprising the following steps: S1. Selecting mature and high-quality loofah, removing the skin and seeds to obtain loofah fiber; S2, pre-treating the loofah fiber to obtain the loofah fiber; S3, dispersing the loofah fiber in water to make it uniformly dispersed, and then drying to obtain an unmodified loofah fiber membrane; S4. Adding the modifier to the unmodified loofah fiber separator, modifying it at 60° C. for 20 min, and obtaining a loofah fiber-based separator.

[0008] Preferably, step S2 comprises the following steps: S21, soaking the loofah fiber in an aqueous solution of sodium hydroxide at 80° C. for 6 h, and obtaining a pretreated material after the soaking is completed; S22, soaking the pretreated material in a hydrogen peroxide solution at 110° C. for 4 hours. After soaking, filtering and washing to obtain loofah fibers.

[0009] Preferably, in step S4, the mass ratio of the modifier to the unmodified loofah fiber membrane is 1:2~6.

[0010] Preferably, in step S4, the modifier is sodium sulfamate or sodium dodecylsulfonate.

[0011] The second object of the present invention is to provide a membrane based on loofah fiber, which is prepared by the above-mentioned method for preparing a membrane based on loofah fiber.

[0012] Preferably, the thickness of the separator is 165 μm and the porosity is 1.3822%.

[0013] The third object of the present invention is to provide an electrochemical device comprising the above-mentioned loofah fiber-based separator.

[0014] A third object of the present invention is to provide an electronic device comprising the above-mentioned electrochemical device.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses loofah fiber as the basic raw material of the diaphragm, taking advantage of the natural advantages of loofah fiber, which is widely available, renewable and low-cost. This is different from traditional diaphragm materials (such as polyolefin diaphragms) that rely heavily on petrochemical raw materials. This fundamentally guarantees the sustainable supply of raw materials and the cost competitiveness of the product. In addition, the preparation process of the present invention is more environmentally friendly than the production process of traditional synthetic diaphragms, produces fewer pollutants, and the discarded diaphragms are more easily degraded in the natural environment, meeting the requirements of environmental protection and sustainable development. (2) The present invention modifies the loofah fiber by selecting a specific organic compound containing active functional groups such as amino groups and sulfonic acid groups as a modifier. This modification method cleverly enhances the surface activity of the fiber and can significantly improve the affinity between the diaphragm and the electrolyte, allowing the electrolyte to quickly and evenly infiltrate the diaphragm, creating good conditions for the conduction of ions in the diaphragm, and overcoming the problem of poor electrolyte infiltration in many existing diaphragm materials (whether natural fiber or synthetic material), thereby improving the charge and discharge efficiency and overall electrochemical performance of the battery; (3) The present invention rationally adjusts the concentration of loofah fibers in aqueous solution and precisely controls the process parameters of each link, such as fiber concentration, mold specifications, suction pressure, and pressing degree, in the preparation of fiber suspension, spreading on the filter mold, vacuum suction, and pressing. This successfully creates a diaphragm with ideal thickness, density, and uniform pore structure, ensuring that the diaphragm has sufficient mechanical strength to prevent short circuits between the positive and negative electrodes and can provide an efficient ion conduction channel. (4) The loofah fiber membrane provided by the present invention can still maintain good dimensional stability in a high temperature environment (up to 100°C), and its thermal shrinkage rate is significantly reduced compared to traditional polyolefin membranes. It can effectively avoid the problem of positive and negative electrode short circuit caused by high temperature, and greatly improve the safety of the electrochemical energy storage device using the membrane in a complex temperature environment; (5) The loofah fiber membrane provided by the present invention has good mechanical properties. The puncture strength of the membrane is doubled compared with the puncture strength of the GF membrane, which means that the loofah fiber membrane prepared by the present invention is more resistant to Zn 2+ The threat of dendrites is reduced, thereby reducing the risk of internal short circuit in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A scanning electron microscope image of a membrane based on loofah fiber provided in Example 2 of the present invention; Figure 2 Graph showing rate performance test results of aqueous zinc ion batteries prepared in Example 3, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 3 Graph showing the long cycle performance of aqueous zinc ion batteries prepared in Example 3, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 4 Graph showing contact angle test results of glass fiber, unmodified loofah fiber membrane, and the loofah fiber-based membrane prepared in Example 2 of the present invention; Figure 5 Graph showing the tensile strength of glass fiber and the membrane based on loofah fiber prepared in Example 2 of the present invention; Figure 6 The cyclic voltage diagram of a battery assembled with glass fiber and the loofah fiber-based separator prepared in Example 2 of the present invention; Figure 7 Graph showing the high temperature stability test results of a conventional polyolefin separator and a separator based on loofah fibers prepared in Example 2 of the present invention; Figure 8 This is a graph showing the puncture strength test results of the glass fiber diaphragm and the loofah fiber-based diaphragm prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0017] The following is a diagram of the embodiment of the present invention. Figures 1 to 8 The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Example 1

[0018] An embodiment of the present invention provides a method for preparing a membrane based on loofah fiber, comprising the following steps: S1. Selecting mature and high-quality loofah, removing the skin and seeds to obtain loofah fiber; S2, pre-treating the loofah fiber to obtain the loofah fiber, specifically comprising the following steps: S21, soaking the loofah fiber in 100 mL of sodium hydroxide aqueous solution at 80° C. for 6 h to obtain a pretreated material; the concentration of the sodium hydroxide aqueous solution in the embodiment of the present invention is 10 mol / L; S22, soaking the pretreated material in 100 mL of hydrogen peroxide solution at 110° C. for 4 h. After soaking, filtering and washing to obtain loofah fiber. The mass concentration of the hydrogen peroxide solution in the embodiment of the present invention is 8%; The embodiment of the present invention can remove impurities on the surface of the loofah fiber through processing, and refine the fiber to obtain fibers with uniform thickness; S3, dispersing the loofah fiber in water, adopting a vacuum filtration method, drying, slicing and cutting, to obtain an unmodified loofah fiber membrane; since the loofah fiber is thin after the hydrogen peroxide soaking treatment in step S2, it needs to be filtered and washed, and the fiber dispersion is not uniform after filtration, so this step requires the washed loofah fiber to be dispersed again in water, and ultrasonic or stirring is used to assist in making it uniformly dispersed.

[0019] S4. Adding the modifier to the unmodified loofah fiber separator, modifying it at 60° C. for 20 min, and obtaining a loofah fiber-based separator.

[0020] In the embodiment of the present invention, the modifier is sodium sulfamate, and the mass ratio of the modifier to the unmodified loofah fiber membrane is 1:6. Example 2

[0021] An embodiment of the present invention provides a membrane based on loofah fiber, which is prepared by the preparation method of the membrane based on loofah fiber of Example 1 above.

[0022] In the embodiment of the present invention, the thickness of the diaphragm is 165 μm and the porosity is 1.3822%. The scanning electron microscope image of the diaphragm is as follows: Figure 1 As shown, through Figure 1 It can be seen that the diameter of the loofah fibers is mostly 20 μm, the gap distribution is relatively uniform, and the surface area is 33.257 m 2 g -1 . Example 3

[0023] An embodiment of the present invention provides an electrochemical device, comprising the loofah fiber-based diaphragm provided in Example 2.

[0024] The electrochemical device of this embodiment is preferably an aqueous zinc ion battery, which is prepared by the following method: A slurry was prepared by uniformly mixing 70 wt.% of the active material (V2O3), 20 wt.% of acetylene black, and 10 wt.% of PVDF in a certain amount of solvent (N-methylpyrrolidone). The slurry was evenly coated on a titanium foil, dried in a vacuum oven at 60°C for 12 hours, and cut into electrode sheets. The mass loading of the active material on the electrode sheet was 1.5-2.0 mg cm −2Then, an aqueous zinc ion battery was assembled at room temperature and pressure using the prepared electrode sheet as the positive electrode, the zinc sheet as the negative electrode, the loofah fiber-based separator provided in Example 2 of the present invention (referred to as the loofah fiber separator) as the battery separator, and 3M zinc trifluoromethanesulfonate as the electrolyte. Example 4

[0025] An embodiment of the present invention provides an electronic device, including the electrochemical device provided in the above-mentioned embodiment 3. Example 5

[0026] The embodiment of the present invention provides a method for preparing a membrane based on loofah fiber. The specific preparation method is the same as that in Example 1, except that the mass ratio of the modifier to the unmodified loofah fiber membrane is 1:2. Example 6

[0027] The embodiment of the present invention provides a method for preparing a membrane based on loofah fiber. The specific preparation method is the same as that in Example 1, except that the mass ratio of the modifier to the unmodified loofah fiber membrane is 1:4. Example 7

[0028] The embodiment of the present invention provides a method for preparing a membrane based on loofah fiber. The specific preparation method is the same as that of Example 1, except that the modifier is sodium dodecyl sulfate.

[0029] Comparative Example 1 This comparative example provides an electrochemical device, which is an aqueous zinc ion battery. The aqueous zinc ion battery is prepared by the following method: A slurry was prepared by uniformly mixing 70 wt.% of the active material (V2O3), 20 wt.% of acetylene black, and 10 wt.% of PVDF in a certain amount of solvent (N-methylpyrrolidone). The slurry was evenly coated on a titanium foil, dried in a vacuum oven at 60°C for 12 hours, and cut into electrode sheets. The mass loading of the active material on the electrode sheet was 1.5-2.0 mg cm −2 Then, an aqueous zinc ion battery was assembled in a glove box using the prepared electrode sheet as the positive electrode, the zinc sheet as the negative electrode, the glass fiber separator as the battery separator, and 3M zinc trifluoromethanesulfonate as the electrolyte.

[0030] Comparative Example 2 This comparative example provides an electrochemical device, which is an aqueous zinc ion battery. The aqueous zinc ion battery is prepared by the following method: A slurry was prepared by uniformly mixing 70 wt.% of the active material (V2O3), 20 wt.% of acetylene black, and 10 wt.% of PVDF in a certain amount of solvent (N-methylpyrrolidone). The slurry was evenly coated on a titanium foil, dried in a vacuum oven at 60°C for 12 hours, and cut into electrode sheets. The mass loading of the active material on the electrode sheet was 1.5-2.0 mg cm −2 Then, an aqueous zinc ion battery was assembled in a glove box using the prepared electrode sheet as the positive electrode, the zinc sheet as the negative electrode, the unmodified loofah fiber membrane prepared in Example 1 of the present invention as the battery separator, and 3M zinc trifluoromethanesulfonate as the electrolyte.

[0031] The electrochemical performance of the aqueous zinc ion batteries prepared in Example 3, Comparative Example 1 and Comparative Example 2 of the present invention is studied below. The charge-discharge performance and rate performance of the aqueous zinc-ion batteries prepared in Example 3, Comparative Example 1, and Comparative Example 2 of the present invention were tested on a LAND CT8001A battery testing system in a voltage range of 0.2-1.8 V.

[0032] Using 0.3, 0.5, 1, 3, 5 and 10A g -1 The current density of the aqueous zinc ion battery prepared in Example 3, Comparative Example 1 and Comparative Example 2 was tested for rate performance. The test results are as follows: Figure 2 As shown, through Figure 2 It can be seen that at different current densities, the battery capacity assembled with the loofah fiber membrane is higher than that of the battery assembled with the glass fiber and unmodified loofah fiber membrane, indicating that the loofah fiber membrane prepared in the embodiment of the present invention has good rate performance.

[0033] In 3A g -1 The long cycle performance test of the aqueous zinc ion batteries prepared in Example 3, Comparative Example 1 and Comparative Example 2 was carried out at a current density of 1.5 %. The test results are as follows: Figure 3 As shown, through Figure 3 It can be seen that after 2000 cycles, the capacity of the battery with loofah fiber membrane is as high as 336.3 mAh g -1 , the capacity retention rate was 93.6%, while the capacity of the battery with glass fiber and unmodified loofah fiber separator was only 79.5 mAh g -1 and 199.9mAh g -1, the capacity retention rate is 21.5% and 62.9%. From the above data, it can be seen that the cycle capacity and electrochemical stability of the loofah fiber separator prepared in the embodiment of the present invention are both optimal. The reason why the loofah fiber separator prepared in the embodiment of the present invention has the above-mentioned excellent electrochemical properties is that the present invention uses sodium aminosulfonate to modify the unmodified loofah fiber separator, cleverly enhancing the surface activity of the fiber, which can significantly improve the affinity between the separator and the electrolyte, allowing the electrolyte to quickly and evenly infiltrate the separator, creating good conditions for ion conduction in the separator, thereby improving the charge and discharge efficiency of the battery and the overall electrochemical performance.

[0034] The contact angles of the glass fiber membrane, the unmodified loofah fiber membrane prepared in Example 1 of the present invention, and the loofah fiber membrane provided in Example 2 of the present invention were tested. The results are as follows: Figure 4 As shown, through Figure 4 It can be observed that the contact angle of the glass fiber membrane is greater than that of the unmodified loofah fiber membrane, and the contact angle of the unmodified loofah fiber membrane is greater than that of the loofah fiber membrane. This shows that the pretreatment process of the present invention and the modification process of adding sodium aminosulfonate increase the hydrophilicity of the membrane, and the good hydrophilicity enables the membrane to be quickly and evenly infiltrated by the electrolyte, and also provides favorable conditions for ion transport; therefore, the good hydrophilicity and mechanical properties of the loofah fiber membrane prepared in the embodiment of the present invention are the reasons for ensuring that the battery maintains good electrochemical performance during operation.

[0035] The tensile test results of the glass fiber membrane and the loofah fiber membrane provided in Example 2 of the present invention are as follows: Figure 5 As shown, through Figure 5 It can be seen that the mechanical properties of the loofah fiber membrane provided by the embodiment of the present invention are much higher than those of glass fiber. If the loofah fiber membrane is to be destroyed, the tensile force required to be applied must be more than 10 times the tensile force required to destroy the glass fiber membrane. During the charging and discharging process of the battery, the electrode material will undergo volume changes and generate internal pressure. A membrane with good mechanical properties can withstand this pressure, maintain structural integrity, and prevent short circuits caused by membrane rupture. It also helps the membrane maintain good interface contact with the electrode and electrolyte for a long time, effectively delaying the aging process of the battery and increasing the service life of the battery.

[0036] The battery assembled with the glass fiber separator and the loofah fiber separator provided in Example 2 of the present invention has a current density of 1 mA cm -2 The long-term cycle performance curve under Figure 6 As shown, through Figure 6 It can be seen that the battery assembled with glass fiber separator has a current density of 1 mA cm -2After 48 hours of circulation under the conditions of , the voltage dropped sharply and was irreversible. This phenomenon shows that due to the formation of zinc dendrites, the battery penetrated the separator, causing a short circuit in the battery. In contrast, the battery assembled using the loofah fiber membrane had a cycle life of 500 hours at the same current density. In a symmetrical battery system, a longer cycle life means that the zinc metal anode with the loofah fiber membrane has more stable performance during the stripping / electroplating process. Therefore, the battery assembled by the loofah fiber membrane provided in Example 2 of the present invention has excellent electrochemical properties.

[0037] The high temperature stability test results of the conventional polyolefin separator and the loofah fiber separator provided in Example 2 of the present invention are as follows: Figure 7 As shown, through Figure 7 It can be seen that the loofah fiber membrane provided in Example 2 of the present invention can still maintain good dimensional stability in a high temperature environment (up to 100°C), and its thermal shrinkage rate is significantly lower than that of traditional polyolefin membranes. It can effectively avoid the positive and negative electrode short circuit problem caused by high temperature, and greatly improve the safety of the electrochemical energy storage device using the membrane in a complex temperature environment.

[0038] The puncture strength test results of the glass fiber membrane and the loofah fiber membrane provided in Example 2 of the present invention are as follows: Figure 8 As shown, through Figure 8 It can be seen that the loofah fiber membrane provided in Example 2 of the present invention has good mechanical properties, and the puncture strength of the membrane is doubled than that of the GF membrane, which means that the loofah fiber membrane prepared by the present invention is more resistant to Zn 2+ The threat of dendrites is reduced, thereby reducing the risk of internal short circuit in the battery.

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a membrane based on loofah fiber, characterized in that, The following steps are involved: S1. Selecting mature and high-quality loofah, removing the skin and seeds to obtain loofah fiber; S2, pre-treating the loofah fiber to obtain the loofah fiber; S3, dispersing the loofah fiber in water to make it uniformly dispersed, and then drying to obtain an unmodified loofah fiber membrane; S4. Adding the modifier to the unmodified loofah fiber separator, modifying it at 60° C. for 20 min, and obtaining a loofah fiber-based separator.

2. The method for preparing a membrane based on loofah fiber according to claim 1, wherein Step S2 includes the following steps: S21, loofah fiber is soaked 6h in 80 DEG C in the aqueous solution of sodium hydroxide, after soaking complete, obtain pre-treated material; S22, soaking the pretreated material in a hydrogen peroxide solution at 110 ° C for 4 h. After soaking, filtering and washing to obtain loofah fiber.

3. The method for preparing a membrane based on loofah fiber according to claim 1, wherein In step S4, the mass ratio of the modifier to the unmodified loofah fiber membrane is 1:2-6.

4. The method for preparing a membrane based on loofah fiber according to claim 1, wherein In step S4, the modifier is sodium sulfamate or sodium dodecylsulfonate.

5. A membrane based on loofah fiber, characterized in that The membrane is prepared by the method for preparing the loofah fiber-based membrane according to any one of claims 1 to 4.

6. The membrane based on loofah fiber according to claim 5, characterized in that The thickness of the separator is 165 μm and the porosity is 1.3822%.

7. An electrochemical device, characterized in that The invention comprises the loofah fiber-based diaphragm according to claim 5 or 6.

8. An electronic device, characterized in that: An electrochemical device comprising the electrochemical device according to claim 7.

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