Membrane for aqueous zinc ion battery as well as preparation method and application of membrane

Abstract

The invention discloses a membrane for an aqueous zinc ion battery as well as a preparation method and application of the membrane. The membrane comprises a supporting layer and a functional layer, the supporting layer is made of cellulose nanofibers; the functional layer is made of modified cellulose nanofibers, and the surface of the functional layer is provided with cationic groups and / or anionic groups. The diaphragm is prepared by adopting a method of combining vacuum filtration with phase inversion, a rolling method, a tape casting method and the like, anions and cations in an electrolyte can be balanced, the conductivity of zinc ions is greatly improved, and the property that the diaphragm is rich in modified functional groups can remarkably inhibit dendritic crystal growth of a zinc negative electrode caused by non-uniform concentration of the zinc ions. The aqueous zinc ion battery assembled by the diaphragm has high zinc ion transference number, growth of zinc dendrites can be effectively inhibited, the electrochemical stability of the battery is improved, and the cycle life of the battery is prolonged. The preparation method disclosed by the invention is simple, diversified, low in equipment requirement degree and environment-friendly, and is expected to be applied to large-scale and low-cost production.

Description

Technical Field

[0001] The present application relates to a membrane for aqueous zinc ion batteries and a preparation method and application thereof, belonging to the field of electrochemistry. Background Art

[0002] The high efficiency and convenience of global tool use in the 21st century are inseparable from electronic products, but most electronic products still rely on the use of non-renewable resources such as fossil energy, which has triggered people's demand for new renewable energy. Lithium-ion batteries are currently mainly used in portable mobile electronic devices, electric vehicles and other fields, but they have problems such as scarce lithium resources and the use of toxic and flammable organic electrolytes, which have affected their sustainable application in the future.

[0003] In contrast, aqueous zinc-ion batteries with metallic zinc as the negative electrode, as a potential alternative to lithium-ion batteries, have many advantages, such as high discharge capacity, good cycle performance, fast charge and discharge, low cost, environmental protection, and high safety. In addition, zinc, the main raw material of aqueous zinc-ion batteries, has abundant reserves and is easy to recycle. However, zinc-ion batteries will produce dendritic deposits during the charging and discharging process, and eventually form zinc dendrites, which is one of the great challenges facing zinc-ion batteries. This problem seriously affects the cycle life and safety of zinc-ion batteries. Therefore, to solve the problem of zinc dendrite growth, researchers need to start from improving and optimizing the electrolyte composition, optimizing the electrode structure and materials, and preparing a diaphragm with better performance.

[0004] The diaphragm is an important component of zinc-ion batteries. Its function is to prevent direct contact between the positive and negative electrodes of the battery, thereby avoiding the occurrence of thermal explosion of the battery. The various parameters of the diaphragm have an important influence on the performance of the entire battery. Parameters such as mechanical strength, porosity, pore size, surface roughness, insulation, thickness, ionic conductivity and electrolyte wettability are all key factors affecting battery performance. In addition, the diaphragm plays the role of electronic insulation and provides microporous channels for ion migration in the battery. It also plays a vital role in the battery's rate performance, cycle life and basic electrochemical performance.

[0005] In aqueous zinc-ion batteries, qualified diaphragms must have 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 both have some problems. The pore size of glass fiber is large, which is easily pierced by zinc dendrites growing at the negative electrode, causing the battery to short-circuit, while the filter paper has an irregular pore structure, resulting in different degrees of electrolyte wetting, making it easy for zinc dendrites to accumulate and grow. These problems will reduce the performance of zinc-ion batteries.

[0006] Therefore, designing and regulating the structure and performance of the separator is expected to solve the problem of zinc dendrites in zinc-ion batteries. Suitable separator materials should have appropriate porosity and pore size distribution, as well as good mechanical properties and ionic conductivity. In this way, the contact between the positive and negative electrodes can be effectively blocked without using additional zinc salts, and the zinc ion migration number and electrochemical performance of the entire battery system can be improved, providing a better choice for the application of zinc-ion batteries. Summary of the invention

[0007] The purpose of the present invention is to provide a multi-layered diaphragm for zinc ion batteries and a preparation method and application thereof, so as to solve the problems of uneven ion transmission, poor mechanical properties of the diaphragm, short service life, etc. in zinc ion batteries.

[0008] According to one aspect of the present application, there is provided a membrane, the membrane comprising a support layer and a functional layer;

[0009] The material of the support layer is cellulose nanofiber;

[0010] The material of the functional layer is modified cellulose nanofiber;

[0011] The surface of the modified cellulose nanofibers has cationic groups and / or anionic groups.

[0012] The cationic group is selected from quaternized cations;

[0013] The anionic group is selected from at least one of -COOH, -COONa, -SO3H, and -SO3Na.

[0014] According to one aspect of the present application, a method for preparing the above-mentioned film is provided, comprising the following steps:

[0015] (1) preparing the support layer by a film-forming method using a solvent solution containing cellulose nanofibers;

[0016] (2) forming the functional layer on the surface of the support layer by a film-forming method using a solvent solution containing modified cellulose nanofibers to obtain the membrane;

[0017] The film forming method is selected from vacuum filtration, phase inversion, calendering and casting.

[0018] The mass content of cellulose nanofibers in the solvent solution containing cellulose nanofibers is 10-1000 mg / ml;

[0019] The mass content of the modified cellulose nanofibers in the solvent solution containing the modified cellulose nanofibers is 1-1000 mg / ml.

[0020] The mass ratio of the cellulose nanofibers in the solvent solution containing the cellulose nanofibers to the modified cellulose nanofibers in the solvent solution containing the modified cellulose nanofibers is 10 to 1:1.

[0021] The cellulose nanofibers in the solvent solution containing the cellulose nanofibers are subjected to a grinding treatment;

[0022] The cellulose nanofibers in the solvent solution containing the cellulose nanofibers have a length of 5 to 20 μm and a diameter of 10 to 50 nm.

[0023] The solvent is selected from at least one of water, ethanol, isopropanol, acetone and N,N-dimethylacetamide.

[0024] Specifically, including

[0025] (1) The cellulose nanofibers prepared by mechanical grinding are uniformly dispersed in 200 ml of deionized water by using an ultrasonic cell disruptor; a single layer of neutral cellulose nanofiber support layer is prepared by a membrane making method; and the ultrasonic disruption time is 10-60 minutes.

[0026] (2) Disperse the functionalized cellulose nanofibers in 200 ml of solvent, and use an ultrasonic cell disruptor to evenly disperse the cellulose nanofibers in 200 ml of deionized water.

[0027] (3) The dispersion in step (2) is used to form a second functional layer on the neutral cellulose nanofiber support layer formed in the above step (1) to obtain a multi-level diaphragm.

[0028] According to one aspect of the present application, there is provided an application of the above-mentioned film, characterized in that:

[0029] Used in aqueous zinc-ion batteries.

[0030] Beneficial effects of the present invention:

[0031] The present invention adopts a method combining vacuum filtration with phase conversion, calendering, tape casting and the like to prepare a multi-level zinc ion battery separator. The separator prepared by the method can balance the anions and cations in the electrolyte, greatly improving the zinc ion conductivity. The property rich in modified functional groups can significantly inhibit the growth of zinc negative electrode dendrites caused by uneven zinc ion concentration. The aqueous zinc ion battery assembled with the separator of the present invention has a high zinc ion migration number, can effectively inhibit the growth of zinc dendrites, and improve the electrochemical stability and cycle life of the battery. The preparation method of the present invention is simple and diverse, has low equipment requirements, is environmentally friendly, and is expected to be applied to large-scale, low-cost production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is a cycle curve of the separator prepared in Example 1 applied to a button-type Zn||Zn half-cell.

[0033] Figure 2 This is a cycle curve of the separator prepared in Comparative Example 1 applied to button-type Zn||Zn half-cell. DETAILED DESCRIPTION

[0034] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0036] Embodiment 1:

[0037] 100 mg of natural cellulose nanofibers were dissolved in 200 ml of deionized water, and ultrasonically broken for 10 minutes to obtain a uniform dispersion. The membrane was formed under vacuum filtration to obtain a single-layer cellulose nanofiber support membrane.

[0038] 100 mg of sulfonated cellulose nanofibers with sulfonate groups were dissolved in 200 ml of isopropanol and ultrasonically disrupted for 10 minutes to obtain a uniform dispersion.

[0039] Sulfonated cellulose nanofibers with sulfonate groups were purchased from Tianjin Mujingling Biotechnology Co., Ltd.

[0040] The sulfonated cellulose nanofiber dispersion is cast and coated on the surface of a single-layer cellulose nanofiber support membrane to form a multi-level diaphragm.

[0041] The multi-layered separator of Example 1 was used to assemble a symmetrical battery. 2 The performance of current density cycling is as follows Figure 1 shown.

[0042] Comparative Example 1:

[0043] 100 mg of natural cellulose nanofibers were dissolved in 200 ml of deionized water, and then ultrasonically broken for 10 minutes to obtain a uniform dispersion. The membrane was formed under vacuum filtration to obtain a single-layer cellulose support membrane.

[0044] The multi-layered separator of Comparative Example 1 was used to assemble a symmetrical battery at 0.5 mA cm 2 The performance of current density cycling is as follows Figure 2 shown.

[0045] As shown in the figure, the multi-layer diaphragm prepared in Example 1 as a diaphragm of an aqueous zinc ion battery can significantly improve the cycle performance of the symmetrical battery and enable the battery to operate stably for more than 1000 hours, while the single-layer diaphragm prepared in Comparative Example 1 fails after the battery operates for 300 hours. This shows that the multi-layer diaphragm for zinc ion batteries prepared by the present invention enables zinc ion batteries to have more excellent electrochemical properties.

[0046] Embodiment 2:

[0047] 100 mg of natural cellulose nanofibers were dissolved in 200 ml of deionized water, and ultrasonically broken for 30 minutes to obtain a uniform dispersion. The membrane was formed under vacuum filtration conditions to obtain a single-layer cellulose nanofiber support membrane.

[0048] 100 mg of quaternary ammonium-modified cellulose nanofibers with quaternary ammonium groups were dissolved in 200 ml of acetone and ultrasonically crushed for 30 minutes to obtain a uniform dispersion. The quaternary ammonium-modified cellulose nanofibers with quaternary ammonium groups were purchased from Tianjin Wood Elf Biotechnology Co., Ltd.

[0049] The quaternary ammonium modified cellulose dispersion is vacuum filtered on the surface of a single-layer cellulose nanofiber support membrane to form a multi-level diaphragm.

[0050] Embodiment 3:

[0051] 100 mg of cellulose nanofibers were dissolved in 200 ml of deionized water, and ultrasonically disrupted for 60 minutes to obtain a uniform dispersion, and then formed into a membrane under vacuum filtration conditions to obtain a single-layer cellulose nanofiber support membrane.

[0052] 100 mg of carboxylate-modified cellulose nanofibers with sodium carboxylate groups were dissolved in 200 mL of N,N-dimethylacetamide and ultrasonically disrupted for 60 minutes to obtain a uniform dispersion. The carboxylate-modified cellulose nanofibers with sodium carboxylate groups were purchased from Tianjin Wood Elf Biotechnology Co., Ltd.

[0053] The carboxylate modified fiber nanofibers are formed into a film on the surface of a single-layer cellulose nanofiber support membrane by a phase inversion method to form a multi-level diaphragm.

[0054] 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 film, characterized in that The membrane comprises a support layer and a functional layer; The material of the support layer is cellulose nanofiber; The material of the functional layer is modified cellulose nanofiber; The surface of the modified cellulose nanofibers has cationic groups and / or anionic groups.

2. The film according to claim 1, characterized in that The cationic group is selected from quaternized cations; The anionic group is selected from at least one of -COOH, -COONa, -SO3H, and -SO3Na.

3. A method for preparing a film according to any one of claims 1 or 2, characterized in that: The following steps are involved: (1) preparing the support layer by a film-forming method using a solvent solution containing cellulose nanofibers; (2) forming the functional layer on the surface of the support layer by a film-forming method using a solvent solution containing modified cellulose nanofibers to obtain the membrane; The film forming method is selected from vacuum filtration, phase inversion, calendering and casting.

4. The preparation method according to claim 3, characterized in that: The mass content of cellulose nanofibers in the solvent solution containing cellulose nanofibers is 10 to 1000 mg / ml; The mass content of the modified cellulose nanofibers in the solvent solution containing the modified cellulose nanofibers is 1 to 1000 mg / ml.

5. The preparation method according to claim 3, characterized in that: The mass ratio of the cellulose nanofibers in the solvent solution containing the cellulose nanofibers to the modified cellulose nanofibers in the solvent solution containing the modified cellulose nanofibers is 10 to 1:

1.

6. The preparation method according to claim 3, characterized in that: The cellulose nanofibers in the solvent solution containing the cellulose nanofibers are subjected to a grinding treatment; The cellulose nanofibers in the solvent solution containing the cellulose nanofibers have a length of 5 to 20 μm and a diameter of 10 to 50 nm.

7. The preparation method according to claim 3, characterized in that: The solvent is selected from at least one of water, ethanol, isopropanol, acetone and N,N-dimethylacetamide.

8. Use of the film according to any one of claims 1 or 2, characterized in that: Used in aqueous zinc-ion batteries.

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