Preparation method of self-assembled cellulose diaphragm, membrane prepared by self-assembled cellulose diaphragm and application of self-assembled cellulose diaphragm

Abstract

The invention discloses a preparation method of a self-assembled cellulose diaphragm, a membrane prepared by the self-assembled cellulose diaphragm and application of the self-assembled cellulose diaphragm. The preparation method comprises the following steps: mixing a solvent solution containing cellulose and zinc salt with a solvent solution containing a microporous material, ultrasonically crushing, and forming a membrane to obtain the self-assembled cellulose diaphragm, the cellulose is selected from cellulose nanofibers and / or cellulose nanowires; after the cellulose and the microporous material are uniformly dispersed in the solution, a film-forming base solution of the self-assembled diaphragm can be formed without adding any binder in the film-forming process, and the self-assembled diaphragm has a good film-forming effect. The composite diaphragm provides an effective channel, promotes the transmission of zinc ions in the battery, has smaller internal resistance than a traditional diaphragm, has high electrolyte preservation rate, is smaller than the traditional diaphragm in thickness, and can improve the energy density and cycle performance of the battery. The preparation process of the diaphragm is simple, the reaction condition is mild, the preparation period is short, and the diaphragm is suitable for large-scale industrial production and commercial application.

Description

Technical Field

[0001] The present application relates to a method for preparing a self-assembled cellulose membrane and the membrane prepared therefrom and its application, and belongs to the field of electrochemistry. Background Art

[0002] In recent years, the problems of energy shortage and lithium mineral resource scarcity have become increasingly prominent, and the problems of poor safety and high price of lithium-ion batteries have gradually become prominent, which has promoted the rapid development of non-lithium chemical power sources in large-scale energy storage fields such as electric vehicles and energy storage grids. Compared with lithium-ion batteries, non-lithium chemical power sources have the advantages of high safety, low price, and environmental friendliness. Therefore, they have also attracted much attention in the fields of large-scale energy storage equipment and new energy vehicles. Finding non-lithium chemical power sources has become an important research topic for researchers to meet the sustainable development of future energy needs.

[0003] Metallic zinc is a material with good electrochemical activity. It is abundant in reserves and low in cost. It is one of the most concerned energy storage materials for secondary batteries. Zinc-ion batteries are assembled with zinc metal as the negative electrode. They have the advantages of high discharge capacity, good cycle performance, fast charge and discharge, low cost, environmental friendliness, and high safety. They have good development prospects in portable electronic devices and large-scale energy storage. However, during the charge and discharge process of zinc-ion batteries, due to the repeated uneven deposition and extraction of zinc ions on the surface of the metal zinc electrode, dendritic deposits will be formed and eventually zinc dendrites will be formed. The zinc dendrites will pierce the diaphragm, resulting in direct contact between the positive and negative electrodes, causing the battery to short-circuit. Therefore, overcoming the growth of zinc dendrites has become one of the most important research topics in zinc-ion batteries. In summary, zinc-ion batteries have broad application prospects as a substitute for lithium-ion batteries, but further research is needed to solve the problems they have.

[0004] Diaphragms are crucial for aqueous zinc-ion batteries, but there are relatively few related studies at present. A qualified aqueous zinc-ion battery diaphragm must have a variety of excellent properties, such as good hydrophilicity, high porosity, uniform pore size distribution, good mechanical properties, high ionic conductivity and zinc ion migration number. Currently, the commonly used diaphragm materials are glass fiber and filter paper, but they have their own limitations. Although glass fiber has good hydrophilicity, its pore size is large and it is easily pierced by zinc dendrites at the negative electrode, causing battery short circuit. At the same time, its brittleness also limits its application in the field of flexible batteries. Filter paper has irregular pore structure and uneven distribution problems, resulting in different degrees of electrolyte wetting, thereby promoting the accumulation and growth of zinc dendrites. These two diaphragms only serve as skeleton support materials to block the positive and negative electrodes and prevent short circuits. Therefore, zinc salts need to be added when assembling the battery, but this will increase the cost, and the positive and negative ions of the zinc salt can move freely, resulting in a decrease in the zinc ion migration number of the entire battery system, thereby affecting the electrochemical performance of the zinc ion battery. Some researchers have tried to use Nafion membranes to replace traditional separators because they have abundant sulfonic acid groups, which can be replaced by zinc ions and used as single ion conductors to improve the electrochemical performance of aqueous zinc ion batteries. However, Nafion membranes are expensive and not environmentally friendly, making them unsuitable for large-scale applications. Summary of the invention

[0005] One of the purposes of the present invention is to solve the deficiencies of the prior art and provide a diaphragm for a zinc ion battery and a preparation method thereof, wherein the diaphragm has the advantages of high safety, puncture resistance, high liquid retention capacity and high porosity.

[0006] According to one aspect of the present application, a method for preparing a self-assembled cellulose membrane is provided, wherein a solvent solution containing cellulose and zinc salt is mixed with a solvent solution containing a microporous material, ultrasonically crushed, and formed into a membrane to obtain the self-assembled cellulose membrane;

[0007] The cellulose is selected from cellulose nanofibers and / or cellulose nanofilaments;

[0008] The film forming method is selected from vacuum filtration, phase inversion, calendering and casting.

[0009] The cellulose may be modified;

[0010] The modified cellulose contains at least one of COOH, COONa, SO3H, SO3Na, and quaternary ammonium cations.

[0011] The zinc salt is selected from at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc chloride, zinc perchlorate, zinc nitrate, zinc tetrafluoroborate and zinc acetate.

[0012] In the solvent solution containing cellulose and zinc salt, the content of cellulose is 0.5 mg / ml;

[0013] In the solvent solution containing cellulose and zinc salt, the content of the zinc salt is 0.01-10M.

[0014] The solvent is selected from at least one of deionized water, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), methanol, ethanol, and acetone.

[0015] The microporous material is selected from at least one of UiO-66, UiO-66-COOH, UiO-66-NO2, UiO-66-NH2, NaX zeolite, ZSM-5 zeolite, ZSM-11 zeolite, ZiF-7, ZiF-8, and MiL-88.

[0016] In the solvent solution containing the microporous material, the mass ratio of the microporous material to the cellulose in the solvent solution containing cellulose and zinc salt is 0.01 to 1:1.

[0017] Specifically,

[0018] (1) dispersing 100 mg of modified / unmodified cellulose nanofibers in 200 ml of a solvent containing zinc salt, and obtaining a uniform dispersion by ultrasonication;

[0019] (2) grinding the microporous material by hand or ball milling to obtain a fine-particle powder, and adding the powder to the uniform dispersion obtained in step 1) above, stirring while adding, to obtain a cellulose nanofiber / microporous material composite dispersion;

[0020] (3) The cellulose / microporous material composite dispersion is ultrasonically crushed at a certain temperature to obtain a uniform cellulose nanofiber / microporous material dispersion; the ultrasonic crushing temperature is 20 to 50° C., and the crushing time is 10 to 60 minutes.

[0021] (4) Film formation to obtain a separator for zinc ion batteries.

[0022] According to another aspect of the present application, a self-assembled cellulose membrane is provided, which is prepared by the above-mentioned preparation method.

[0023] According to another aspect of the present application, there is provided an application of the self-assembled cellulose membrane for use in aqueous zinc ion batteries.

[0024] The advantages of this application are:

[0025] After the cellulose and microporous material are uniformly dispersed in the solution, no binder needs to be added during the film-forming process to form a film-forming base liquid for the self-assembled membrane, and has a good film-forming effect. The composite membrane provides an effective channel to promote the transmission of zinc ions in the battery, has a smaller internal resistance than the traditional membrane, and has a high electrolyte preservation rate and a thickness less than the traditional membrane, which can improve the energy density and cycle performance of the battery. The preparation process of the membrane is simple, the reaction conditions are mild, the production cycle is short, and it is suitable for large-scale industrial production and commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a cycle curve of the separator prepared in Example 1 applied to a button-type Zn||Zn half-cell.

[0027] Figure 2 This is a cycle curve of the glass fiber separator used in Comparative Example 1 applied to a button-type Zn||Zn half-cell. DETAILED DESCRIPTION

[0028] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0029] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0030] Embodiment 1:

[0031] 100 mg of neutral cellulose nanofibers were dissolved in 200 ml of an aqueous solution containing 2M ZnSO4 zinc salt, and a uniform dispersion was obtained by ultrasonic disruption.

[0032] 1 mg of UiO-66-COOH material was manually ground to obtain a fine-grained powder, which was added to a uniform dispersion while being stirred to obtain an aramid cellulose nanofilament / UiO-66-COOH composite dispersion;

[0033] The neutral cellulose nanofiber / UiO-66-COOH composite dispersion was ultrasonically crushed at 50 degrees Celsius for 30 minutes to obtain a uniform neutral cellulose nanofiber / microporous material dispersion;

[0034] The obtained dispersion was vacuum filtered to obtain a neutral cellulose nanofiber / UiO-66-COOH multidimensional self-assembled membrane.

[0035] The multi-dimensional self-assembled membrane of Example 1 was used to assemble a symmetrical battery at 1 mA cm 2 The performance of current density cycling is shown in the attached Figure 1 shown.

[0036] Embodiment 2:

[0037] 100 mg of carboxylated cellulose nanofibers were dissolved in an aqueous solution containing 200 ml of 2M Zn(OTF)2 zinc salt, and a uniform dispersion was obtained by ultrasonication.

[0038] 100 mg of NaX zeolite material was manually ground for 30 minutes to obtain a fine-grained powder, which was added to the uniform dispersion while stirring to obtain a carboxylated cellulose nanofiber / NaX zeolite composite dispersion;

[0039] The cellulose / NaX zeolite composite dispersion was ultrasonically crushed at 25 degrees Celsius for 30 minutes to obtain a uniform cellulose / NaX zeolite dispersion;

[0040] The obtained product was vacuum filtered to obtain a carboxylated cellulose nanofiber / NaX zeolite multidimensional self-assembled membrane.

[0041] Embodiment 3:

[0042] 100 mg of sulfonated cellulose nanofibers were dissolved in 200 ml of DMAc solution containing 3 M Zn(OTF)2 zinc salt, and a uniform dispersion was obtained by ultrasonic disruption.

[0043] 100 mg of ZiF-8 material was manually ground for 30 min to obtain a fine-grained powder, which was added to the uniform dispersion while stirring to obtain a sulfonated cellulose nanofiber / ZiF-8 zeolite composite dispersion;

[0044] The sulfonated cellulose / ZiF-8 composite dispersion was ultrasonically crushed at 40 degrees Celsius for 30 minutes to obtain a uniform sulfonated cellulose nanofiber / ZiF-8 dispersion;

[0045] The obtained dispersion was adjusted to a thickness of 100 μm by using a scraper, and the dispersion was evenly scraped onto a glass plate, and then dried to obtain a sulfonated cellulose / ZiF-8 multidimensional self-assembled membrane.

[0046] Comparative Example 1:

[0047] A symmetrical cell was assembled using a commercially available glass fiber separator and the current was 1 mA cm 2 The performance of current density cycling is shown in the attached Figure 2 shown.

[0048] As shown in the figure, the multi-dimensional self-assembled membrane prepared in Example 1 as a membrane of an aqueous zinc ion battery can significantly improve the cycle performance of the symmetrical battery, and can make the battery run stably for more than 1100 hours, while the commercially available glass fiber membrane used in Comparative Example 1 fails after the battery runs for 300 hours. This shows that the multi-level membrane for zinc ion batteries prepared by the present invention enables zinc ion batteries to have more excellent electrochemical properties.

[0049] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a self-assembled cellulose membrane, characterized in that: Mixing a solvent solution containing cellulose and zinc salt with a solvent solution containing a microporous material, ultrasonically crushing, and forming a film to obtain the self-assembled cellulose membrane; The cellulose is selected from cellulose nanofibers and / or cellulose nanofilaments; The film forming method is selected from vacuum filtration, phase inversion, calendering and casting.

2. The preparation method according to claim 1, characterized in that: The cellulose is modified; The modified cellulose contains at least one of COOH, COONa, SO3H, SO3Na, and quaternary ammonium cations.

3. The preparation method according to claim 1, characterized in that: The zinc salt is selected from at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc chloride, zinc perchlorate, zinc nitrate, zinc tetrafluoroborate and zinc acetate.

4. The preparation method according to claim 1, characterized in that: In the solvent solution containing cellulose and zinc salt, the content of cellulose is 0.5 mg / ml; In the solvent solution containing cellulose and zinc salt, the content of the zinc salt is 0.01-10M.

5. The preparation method according to claim 1, characterized in that: The solvent is selected from at least one of water, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), methanol, ethanol, and acetone.

6. The preparation method according to claim 1, characterized in that: The microporous material is selected from at least one of UiO-66, UiO-66-COOH, UiO-66-NO2, UiO-66-NH2, NaX zeolite, ZSM-5 zeolite, ZSM-11 zeolite, ZiF-7, ZiF-8, and MiL-88.

7. The preparation method according to claim 1, characterized in that: In the solvent solution containing the microporous material, the mass ratio of the microporous material to the cellulose in the solvent solution containing cellulose and zinc salt is 0.01 to 1:

1.

8. A self-assembled cellulose membrane, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. An application of the self-assembled cellulose membrane according to claim 8, characterized in that: Used in aqueous zinc-ion batteries.

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