Water-based zinc ion battery modified diaphragm as well as preparation method and application thereof

Abstract

The invention discloses an aqueous zinc ion battery modified diaphragm and a preparation method and application thereof, and relates to the technical field of aqueous zinc ion batteries, the method comprises the following steps: thermally dissolving cellulose with the mass fraction of 0.5-1.5 wt% in an N-methylmorpholine-N-oxide aqueous solution to obtain a cellulose mixed solution; soaking a glass fiber diaphragm in the cellulose mixed solution, and standing for reaction to obtain a soaked glass fiber diaphragm; and carrying out phase separation on the soaked glass fiber through deionized water or absolute ethyl alcohol, and drying to obtain the aqueous zinc ion battery modified diaphragm. Through non-solvent induced phase separation, cellulose exposes more active hydroxyl groups (-OH), the migration path of zinc ions in the composite diaphragm is optimized, the migration number of the zinc ions is remarkably increased, and uniform deposition of the zinc ions on the surface of a negative electrode is promoted, so that growth of zinc dendrites is inhibited.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, and in particular to a modified separator for aqueous zinc-ion batteries, its preparation method, and its application. Background Technology

[0002] In recent years, to achieve efficient utilization and stable output of new energy sources, energy storage technology has become a core link connecting energy harvesting and end-use, and its importance is undeniable. Among various energy storage battery technologies, aqueous zinc-ion batteries, with their significant advantages such as non-toxicity, high raw material abundance, and low manufacturing cost, have shown great application potential and become one of the research hotspots in the field. As the core negative electrode material of aqueous zinc-ion batteries, zinc metal itself possesses a high theoretical capacity (5854 mAh cm⁻¹). -3 The high energy density and high output performance of zinc-ion batteries are based on their high energy density and low redox potential (-0.76 V vs. SHE). However, zinc metal anodes consistently face severe challenges in terms of cycle stability. During charge-discharge cycles, zinc anodes are prone to dendrite growth, hydrogen evolution reaction, and the generation of insulating byproducts. These problems directly lead to a significant reduction in battery coulombic efficiency and a significant shortening of cycle life, becoming a key bottleneck hindering the commercial application of aqueous zinc-ion batteries. To address these issues, existing interface modification strategies mainly fall into three categories: electrolyte engineering, anode surface coating modification, and separator modification.

[0003] As a crucial component of batteries, the separator not only prevents direct contact between the positive and negative electrodes to avoid short circuits, but also plays a vital role in regulating zinc ion transport efficiency and the interfacial chemical stability between the electrodes and the electrolyte. Its performance directly impacts the overall battery performance. Glass fiber separators are the most widely used separators in aqueous zinc-ion batteries, but they have significant drawbacks: poor mechanical properties and large pore structures, making them highly susceptible to being punctured by growing zinc dendrites during cycling, leading to internal short circuits and severely threatening battery safety and cycle stability. Therefore, modifying glass fiber separators has become one of the direct and efficient technical approaches to improve the performance of aqueous zinc-ion batteries.

[0004] Currently, the most common method for modifying separators is to construct a surface coating layer, which involves coating a slurry made of modified materials and binders onto the surface of a glass fiber separator and then drying it. Modified separators prepared using this method have the following problems: First, the introduction of binders increases the volume and weight of the battery, leading to a dilution of the overall energy density. Second, the coating layer is prone to detachment during long-term, repeated electrochemical cycling, affecting not only the sustainability of the modification effect but also resulting in poor reproducibility during experimental preparation, making it difficult to meet the needs of large-scale applications.

[0005] Therefore, it is of great significance to develop a modified diaphragm that is simple to process and can effectively improve the cycle stability of zinc anodes. Summary of the Invention

[0006] This invention provides a modified separator for aqueous zinc-ion batteries, its preparation method, and its application, to solve problems such as zinc dendrite growth piercing the separator and causing battery short circuits in the prior art. It aims to enhance the mechanical strength of the peeled fiber separator, induce uniform zinc ion deposition, and inhibit the generation of zinc dendrites and by-products, so as to achieve a long cycle life for aqueous zinc-ion batteries.

[0007] To achieve the above objectives, the technical solution of this invention is as follows:

[0008] The first aspect of the present invention provides a method for preparing a modified separator for an aqueous zinc-ion battery, comprising:

[0009] Cellulose with a mass fraction of 0.5-1.5 wt% was thermally dissolved in an aqueous solution of N-methylmorpholine-N-oxide to obtain a cellulose mixture;

[0010] The diaphragm is immersed in the cellulose mixture and allowed to stand to react, resulting in the immersed diaphragm.

[0011] The soaked membrane is placed in a non-solvent to induce phase separation, resulting in a phase-separated membrane. After drying, the modified membrane for aqueous zinc-ion batteries is obtained.

[0012] Preferably, in conjunction with the first aspect, the non-solvent is deionized water or anhydrous ethanol.

[0013] Preferably, in conjunction with the first aspect, the cellulose loading in the aqueous zinc-ion battery modified separator is 0.2-1.8 mg cm⁻¹. -2 .

[0014] A second aspect of the present invention provides the application of an aqueous zinc-ion battery modified separator prepared by any of the methods described in the first aspect in the assembly of zinc / / zinc symmetric batteries and zinc / / zinc vanadate full batteries.

[0015] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present invention include at least the following:

[0016] 1) Significantly inhibits zinc dendrite growth: By using non-solvent-induced phase separation to expose more active hydroxyl groups (-OH) in cellulose, the migration path of zinc ions in the composite membrane is optimized, significantly increasing the zinc ion migration number and promoting uniform deposition of zinc ions on the negative electrode surface, thereby inhibiting the growth of zinc dendrites.

[0017] 2) Enhanced mechanical properties: Regenerated cellulose exhibits a gradient distribution structure in glass fiber, mainly concentrated on both sides of the glass fiber separator, providing good mechanical properties and flexibility, ensuring that the battery maintains structural stability during operation, thereby improving the safety of aqueous zinc-ion batteries.

[0018] 3) Environmentally friendly: The raw material cellulose is green, environmentally friendly and renewable, with good biodegradability. The solvent used to dissolve cellulose can be recycled and reused. Furthermore, this method allows cellulose to be anchored in situ in glass fiber, avoiding the use of binders. The overall preparation process is environmentally friendly and sustainable, which is in line with the current trend of green development of energy storage technology and is easy to industrialize. Attached Figure Description

[0019] Figure 1 SEM comparison images of the diaphragms of Example 2 and Comparative Example 1 provided by the present invention;

[0020] Figure 2 A comparison diagram of the mechanical properties of the diaphragm in Example 2 and Comparative Example 1 provided by the present invention;

[0021] Figure 3 A comparison diagram of the ionic conductivity of the membranes in Example 2 and Comparative Example 1 provided by the present invention;

[0022] Figure 4 The Zn / / Zn symmetric cells assembled with the separators of Examples 1-3 and Comparative Example 1 provided by this invention were tested at 10 mAcm. -2 Current density and 10 mA cm -2 Comparison of cyclic test results under specific capacity;

[0023] Figure 5 The Zn / / Zn symmetric cells assembled with separators in Example 2 and Comparative Example 1 provided by the present invention were used at 1 mA cm⁻¹ -2 Current density and 1 mA cm -2 SEM comparison images of zinc anode after 100 h of cycling at specific capacity;

[0024] Figure 6 The Zn / / ZVO full cells assembled with the separators of Example 2 and Comparative Example 1 provided by the present invention were used at 1 mA g -1 Comparison of constant current charge-discharge cycle test results under current density. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on the present invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following description, references to "some embodiments" refer to a subset of all possible embodiments; however, it is understood that "some embodiments" may be the same or different subsets of all possible embodiments and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the invention have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the invention pertain. The terminology used in the embodiments of the invention is for the purpose of describing the embodiments of the invention only and is not intended to limit the invention.

[0027] In the following description of this embodiment, the terms "including", "comprising", "having", and "containing" are all open-ended terms, meaning that they include but are not limited to.

[0028] It should be noted that all raw materials / reagents in the embodiments of the present invention can be purchased on the market or prepared according to conventional methods known to those skilled in the art; the term "and / or" in the embodiments of the present invention is only used to describe the relationship between related objects, indicating that there can be three relationships. For example, A and / or B means three cases: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship.

[0029] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0030] Those skilled in the art should understand that, in the following description of the embodiments of the present invention, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0031] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0032] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value and an intermediate value within the stated range, as well as any other stated value or an intermediate value within the stated range, is also included within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, the technical / 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 are described herein, any methods and materials similar or equivalent to those described herein may be used in embodiments or test cases of the invention. All references to this specification are generally incorporated herein by reference to disclose and describe methods and / or materials associated with said references. In the event of any conflict with any incorporated reference, the contents of this specification shall prevail.

[0034] It should be noted that all raw materials and / or reagents in the embodiments of the present invention were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0035] In a first aspect, embodiments of the present invention provide a modified separator for aqueous zinc-ion batteries, the preparation method of which includes:

[0036] Cellulose with a mass fraction of 0.5-1.5 wt% was thermally dissolved in an aqueous solution of N-methylmorpholine-N-oxide to obtain a cellulose mixture;

[0037] The glass fiber membrane is immersed in the cellulose mixture and allowed to stand for reaction to obtain the immersed glass fiber membrane.

[0038] The water-based zinc-ion battery modified separator is obtained by separating the phases of the soaked glass fibers with deionized water or anhydrous ethanol and then drying them.

[0039] The modified separator for aqueous zinc-ion batteries provided by this invention: 1) Significantly inhibits zinc dendrite growth: By using non-solvent-induced phase separation to expose more active hydroxyl groups (-OH) in cellulose, the migration path of zinc ions in the composite separator is optimized, significantly increasing the zinc ion transference number and promoting uniform deposition of zinc ions on the negative electrode surface, thereby inhibiting the growth of zinc dendrites. 2) Enhances mechanical properties: Regenerated cellulose exhibits a gradient distribution structure in glass fibers, mainly concentrated on both sides of the glass fiber separator, providing good mechanical properties and flexibility, ensuring structural stability of the battery during operation, thereby improving the safety of aqueous zinc-ion batteries. 3) Environmentally friendly: The raw material cellulose is green, environmentally friendly, and renewable, with good biodegradability. The solvent used to dissolve cellulose can be recycled and reused. Furthermore, this method allows cellulose to be anchored in situ within the glass fibers, avoiding the use of binders. The overall preparation process is environmentally friendly and sustainable, conforming to the current trend of green development in energy storage technology, and is easy to industrialize.

[0040] In a specific embodiment, the non-solvent is preferably deionized water or anhydrous ethanol.

[0041] In a specific embodiment, the cellulose loading in the modified separator for aqueous zinc-ion batteries is preferably 0.2-1.8 mg / cm³. -2 .

[0042] Secondly, embodiments of the present invention provide the application of an aqueous zinc-ion battery modified separator prepared by any of the methods described in the first aspect in the assembly of zinc / / zinc symmetric batteries and zinc / / zinc vanadate full batteries.

[0043] The technical method of the present invention will be further described below with reference to specific embodiments.

[0044] This invention provides a method for preparing an aqueous zinc-ion battery modified separator. First, cellulose is added to an aqueous solution of N-methylmorpholine-N-oxide and heated and stirred at 70-90 °C for 1-3 h to obtain a cellulose solution. Next, a glass fiber separator is completely immersed in the mixed solution and allowed to stand until the cellulose solution fully saturates the separator. Subsequently, the separator, now saturated with the cellulose solution, is placed in a large amount of non-solvent, where solvent exchange induces phase separation. Finally, the composite separator is removed from the non-solvent and dried at 50-70 °C for 10-15 h to obtain the zinc-ion battery modified composite separator.

[0045] Example 1

[0046] S1: Add cellulose to an aqueous solution of N-methylmorpholine-N-oxide and stir at 70~90 ℃ for 1~3 h to obtain a mixed solution with a mass concentration of 0.5wt%;

[0047] S2: Add the commercially available glass fiber diaphragm (GF, 47 mm diameter circle) to the mixed solution in S1, soak it at room temperature for 10-30 minutes, and then remove it;

[0048] S3: Place the soaked diaphragm in a large amount of deionized water for solvent exchange, changing the deionized water every 2 hours, for 3-5 times;

[0049] S4: Take out the separator and dry it in an oven at 50~70 ℃ for 10~15 h to obtain the modified separator 1 for aqueous zinc-ion batteries.

[0050] In the aqueous zinc-ion battery modified separator 1 prepared in Example 1, the cellulose loading was 0.3~0.5 mg / cm³. -2 .

[0051] Example 2

[0052] The preparation method in this embodiment is the same as in Example 1, except that the concentration of the mixed solution in step S1 is different. The mass concentration of the mixed solution is 1 wt%, and the cellulose loading is 0.8~1 mg cm⁻¹. -2 All other implementation conditions remain unchanged.

[0053] Example 3

[0054] The preparation method in this embodiment is the same as in Example 1, except that the concentration of the mixed solution in step S1 is different. The mass concentration of the mixed solution is 1.5 wt%, and the cellulose loading is 1.3~1.5 mg / cm³. -2 All other implementation conditions remain unchanged.

[0055] Comparative Example 1

[0056] Comparative Example 1 uses an unmodified glass fiber membrane, denoted as GF membrane.

[0057] The separators from Examples 1-3 and the comparative example were used to assemble aqueous zinc-ion batteries, and the battery performance was tested. The specific steps are as follows:

[0058] Preparation of zinc vanadate (ZVO) cathode: 364 mg of vanadium pentoxide and 74.5 mg of zinc nitrate hexahydrate were accurately weighed and dissolved in 75 mL of deionized water. After dissolution, 2 mL of 30 wt% hydrogen peroxide solution was slowly added dropwise. After stirring for 30 min, the mixture was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and heated at 120 ℃ for 12 h. After the reaction was completed, the solid precipitate was collected by centrifugation and freeze-dried to obtain the final product.

[0059] Battery assembly and electrochemical performance testing: Assembly was carried out in an air environment. Symmetrical cells were assembled using zinc sheets as both positive and negative electrodes, while full cells were assembled using zinc vanadate as the positive electrode and zinc sheets as the negative electrode. In this embodiment, a 2M zinc sulfate solution was used as the electrolyte. Constant current charge-discharge tests were performed on the full cells using the Blue Battery testing system, with a voltage range of 0.3-1.6 V and 1000 cycle times. Simultaneously, at 1 mA cm⁻¹... -2 Current density and 1 mAh cm -2 Cyclic testing was performed on symmetrical cells to assess specific capacity.

[0060] The principle of this invention lies in using a solvent-inducing phase separation method to in-situ anchor cellulose in a glass fiber membrane to construct a modified composite membrane. The rearrangement of the cellulose molecular chains exposes more active hydroxyl groups, promoting the formation of Zn... 2+ Rapid diffusion and uniform Zn 2+ The interface distribution enables dendrite-free zinc deposition. Furthermore, the denser structure and abundant negatively charged surface of the modified diaphragm effectively shield against water molecules and anions, preventing hydrogen evolution and zinc corrosion. The modified diaphragm's good mechanical strength also allows it to withstand the volume changes of the zinc anode under harsh cycling conditions.

[0061] Effect verification:

[0062] 1) Characterizing the morphology and structure of the diaphragm

[0063] The membranes of Example 2 and Comparative Example 1 were characterized using SEM, as shown below. Figure 1 As shown, the membrane in Comparative Example 1 is made of glass fibers with smooth surfaces and varying pore sizes. In the membrane of Example 2, cellulose is mainly distributed on both sides of the glass fiber membrane, exhibiting a gradient distribution structure. This enhances the mechanical properties of the membrane, and the pores of the glass fiber membrane are filled with cellulose, reducing the pore size.

[0064] 2) Characterizing the mechanical properties of the diaphragm

[0065] The mechanical properties of the diaphragms in Example 2 and Comparative Example 1 were characterized using a universal testing machine. Figure 2 As shown in the tensile stress-strain curve, the tensile stress of the diaphragm in Example 2 is 95.53 kPa, which is much greater than the tensile stress of Comparative Example 1 (16.42 kPa). This indicates that Example 2 has better mechanical properties, making it difficult for zinc dendrites to pierce the diaphragm and enabling it to cope with volume deformation during cycling.

[0066] 3) Characterizing the ionic conductivity of the membrane

[0067] The ionic conductivity of the membranes in Example 2 and Comparative Example 1 was characterized using an electrochemical workstation. Figure 3As shown, the ionic conductivity of the modified membrane in Example 2 is 11.48 mS / cm. -1 The ionic conductivity is greater than that of the membrane in Comparative Study 1 (9.88 mS / cm). -1 This indicates that the modified membrane exposes more active hydroxyl groups to accelerate zinc ion migration.

[0068] 4) The battery testing system tests Zn / / Zn symmetric cells.

[0069] The Zn / / Zn symmetric cells assembled with separators in Examples 1-3 and the comparative example were tested using the Blue Battery testing system at 10 mA cm⁻¹. -2 Current density and 10 mAh cm -2 Constant current cycling test was performed at specific capacity. For example... Figure 4 As shown, the cycle life of the symmetrical cells assembled based on the separators of Examples 1-3 is longer than that of the symmetrical cells assembled based on the comparative separators. Among them, the cycle life of the symmetrical cell assembled based on the separator of Example 2 is close to 660 h, which is 7.4 times that of the symmetrical cell assembled based on the separator of Example 2 (89 h), demonstrating the effectiveness of the surface cellulose modified glass fiber separator method.

[0070] 5) Characterize the surface of the zinc anode using a diaphragm

[0071] SEM was used to study Zn / / Zn symmetric cells at 1 mA cm⁻¹. -2 Current density and 1mAh cm -2 The zinc anode was characterized after 100 h of cycling at specific capacity. For example... Figure 5 As shown, the zinc anode surface using the separator of Comparative Example 1 is uneven, with a large number of zinc dendrites and byproducts. As the cycle time increases, a large number of randomly accumulated zinc dendrites will pierce the separator and cause the battery to short circuit. In contrast, the zinc anode surface using the separator of Example 2 is smoother and no obvious zinc dendrites and byproducts are present.

[0072] 6) The battery testing system tests Zn / / ZVO full cells.

[0073] The Zn / / ZVO full cells assembled with separators in Example 2 and Comparative Example 1 were tested using the Blue Battery Testing System at 1 A g. -1 Constant current cycling tests were performed at current density. For example... Figure 6 As shown, the full cell assembled based on the ratio 1 separator exhibits a yield of 103.05 mAh g⁻¹ after 1000 cycles. -1 The specific capacity of the cell retained 48.87% of the initial capacity. In contrast, the full cell assembled based on the separator of Comparative Example 1 failed due to short circuit after about 460 cycles.

[0074] The symmetrical battery assembled using the modified separator in Example 2 above shows significantly better cycle performance and full-cell cycle life than the battery assembled using a commercial glass fiber separator in Comparative Example 1.

[0075] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a modified separator for an aqueous zinc-ion battery, characterized in that, include: Cellulose with a mass fraction of 0.5-1.5 wt% was thermally dissolved in an aqueous solution of N-methylmorpholine-N-oxide to obtain a cellulose mixture; The glass fiber membrane is immersed in the cellulose mixture and allowed to stand to react, thus obtaining the immersed glass fiber membrane. The water-based zinc-ion battery modified separator is obtained by separating the phases of the soaked glass fibers with deionized water or anhydrous ethanol and then drying them.

2. The method for preparing the modified separator for aqueous zinc-ion batteries according to claim 1, characterized in that, The non-solvent is deionized water or anhydrous ethanol.

3. The method for preparing the modified separator for aqueous zinc-ion batteries according to claim 1, characterized in that, The cellulose loading in the modified separator for aqueous zinc-ion batteries is 0.2-1.8 mg cm⁻¹. -2 .

4. The application of an aqueous zinc-ion battery modified separator prepared according to any one of claims 1-3 in the assembly of zinc / / zinc symmetric cells and zinc / / zinc vanadate full cells.

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