Preparation method and application of degradable aqueous zinc ion battery paper-based diaphragm

Abstract

The invention relates to the technical field of water-based zinc ion batteries, and discloses a preparation method and application of a degradable water-based zinc ion battery paper-based diaphragm. The preparation method comprises the following steps: (1) adding halloysite nanotubes into water, and carrying out ultrasonic dispersion to obtain a halloysite nanotube suspension; (2) adding glacial acetic acid, polyethylene glycol and chitosan into the halloysite nanotube turbid liquid, uniformly stirring and compounding to obtain composite slurry; and (3) uniformly coating the surface of the paper-based diaphragm with the composite slurry, and drying to form a coating, thereby obtaining the degradable water-based zinc ion battery paper-based diaphragm. The halloysite nanotubes are uniformly adsorbed on a chitosan polymer chain network to form a composite material, the composite material is modified on the paper-based diaphragm, so that the transmission efficiency of zinc ions is improved, and meanwhile, the diaphragm has excellent mechanical strength, can bear the volume change of a zinc negative electrode in a battery cycle process, keeps the structural integrity of the diaphragm, and has a good application prospect. The cycle life of the battery is further prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of aqueous zinc ion batteries, and more specifically relates to a preparation method and application of a degradable paper-based diaphragm for aqueous zinc ion batteries. Background Art

[0002] In recent years, the energy industry has achieved remarkable results in the development process of building a clean, low-carbon, safe and efficient energy system. At the same time, the intermittent and discontinuous nature of clean energy such as wind and solar energy has strongly promoted the growth and development of large-scale energy storage technology and equipment. Although lithium-ion batteries have significant advantages such as high conversion efficiency and high energy density, the high cost of lithium and cobalt, the harm to the environment, and the harsh environment required for battery production have limited the large-scale application of lithium-ion batteries. In recent years, aqueous zinc-ion batteries (ZIBs) have relied on their own safety, non-toxicity, and high theoretical capacity (5854mAh·cm -3 ) and a low redox potential (-0.763 V compared to the standard hydrogen electrode (ShE)), it has become one of the most promising sustainable energy storage technologies.

[0003] Aqueous zinc-ion batteries are generally composed of an anode, a cathode, an electrolyte, and a diaphragm. As an indispensable component of the battery, the diaphragm is closely connected to the electrode and can separate the anode and cathode to prevent the battery from short-circuiting. The morphology, structure, composition, and physical and chemical properties of the diaphragm play an extremely critical role in the long-lasting and excellent electrochemical performance of the battery. The performance stability of aqueous zinc-ion batteries depends to a large extent on the combination of various parameters, which work together to play a role. Generally, glass fiber (GF), cellulose, polymers, etc. can be used as raw materials for diaphragms of aqueous zinc-ion batteries. Among them, the mechanical properties of commercial glass fiber diaphragms are poor, and they are easy to break or damage during the battery charge and discharge cycle, which is difficult to meet the needs of long-term use. At the same time, the ion transmission performance of commercial glass fiber diaphragms is insufficient, which limits the battery performance. In addition, there are environmental issues (such as non-degradability) in the process of its preparation and disposal, so it is necessary to explore more suitable alternative materials.

[0004] The preparation process and raw materials used for paper-based diaphragms (filter paper, weighing paper, and commercial printing paper, etc.) are relatively environmentally friendly, so they have the potential to replace glass fiber diaphragms. However, pure paper-based diaphragms still have some defects when used as battery diaphragms: weak mechanical strength, easy to break or damage during battery use, affecting the long-term stability of the battery; large pores and uneven distribution, so the ion transmission performance is relatively poor, which may limit the rapid charge and discharge characteristics of the battery, and needs to be improved through modification and other means; and paper-based diaphragms are difficult to maintain stability in harsh environments such as high temperature and high humidity, and need to be further modified to enhance their durability and adaptability. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a degradable paper-based diaphragm for aqueous zinc ion batteries that is simple to prepare, low in cost and has stable performance. The present invention uniformly adsorbs halloysite nanotubes on a chitosan polymer chain network to form a composite material, and the modification on the paper-based diaphragm helps to improve the zinc ion transmission efficiency. At the same time, the diaphragm has excellent mechanical strength, can withstand the volume change of the zinc negative electrode during the battery cycle, maintain its structural integrity, and further extend the battery cycle life.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] First, the present invention provides a method for preparing a degradable paper-based diaphragm for an aqueous zinc ion battery, which comprises the following steps:

[0008] (1) adding halloysite nanotubes into water and dispersing by ultrasonication to obtain a suspension of halloysite nanotubes;

[0009] (2) adding glacial acetic acid, polyethylene glycol and chitosan to the halloysite nanotube suspension, stirring evenly for compounding, and obtaining a composite slurry;

[0010] (3) The composite slurry is evenly coated on the surface of the paper-based diaphragm, dried, and a coating is formed to obtain a degradable aqueous zinc ion battery paper-based diaphragm.

[0011] In the above preparation method, the present invention firstly disperses the halloysite nanotubes in water through ultrasonic treatment, further enhances the surface activity of the halloysite nanotubes and alleviates agglomeration; then uses natural chitosan with rich functional groups to mix with the halloysite nanotubes to form a homogeneous composite slurry; finally, the composite slurry is coated on the surface of the paper-based diaphragm, so that the composite material formed by the chitosan and the halloysite nanotubes is fully fixed on the paper fibers through physical adsorption, and after drying, a degradable aqueous zinc ion battery paper-based diaphragm is obtained.

[0012] Preferably, in step (1), the concentration of the halloysite nanotube suspension is 0.1 to 0.3 g / mL.

[0013] Preferably, in step (2), the mass ratio of chitosan to halloysite nanotubes is 1:(0.2-0.5).

[0014] The present invention finds that the quality comparison of chitosan and halloysite nanotubes is critical. Too little chitosan may not be able to fully cover the surface of the filter paper fiber, resulting in an insignificant modification effect, and the ion transmission efficiency, mechanical strength or chemical stability of the diaphragm cannot be significantly improved; at the same time, too little chitosan may not be able to form an effective synergistic effect with the halloysite nanotubes, and the advantages of both in improving battery performance cannot be fully utilized; on the contrary, adding excessive chitosan will form a too thick coating on the surface of the filter paper, blocking the original pore structure of the paper-based material, making it difficult for the electrolyte to fully infiltrate the diaphragm, thereby reducing the ion transmission rate and conductivity. Therefore, in practical applications, it is necessary to strictly control the mass ratio of the two through optimization experiments to maximize battery performance. This ratio should ensure that chitosan can evenly cover the surface of the paper-based fibers and form a good synergistic effect with the halloysite nanotubes, while avoiding blocking the pore structure of the paper-based material and retaining sufficient liquid absorption capacity.

[0015] Preferably, in step (2), the stirring condition is 20-40° C. for 3-24 h.

[0016] Halloysite nanotubes, due to their high specific surface area and layered wall structure, tend to spontaneously aggregate in solution to form larger particles if not treated. This agglomeration phenomenon significantly reduces the effective specific surface area of ​​the nanotubes and reduces their dispersion uniformity in the composite material, thus affecting the overall performance of the composite material. After uniform dispersion, they are mixed with chitosan to promote the interfacial compatibility between the two through intermolecular forces.

[0017] Preferably, in step (3), the paper-based membrane is filter paper, weighing paper or commercial printing paper.

[0018] Preferably, in step (3), the coating method is immersion, suction filtration, drip coating or spin coating.

[0019] Preferably, in step (3), the thickness of the coating is 20 to 80 μm.

[0020] Secondly, the present invention provides a degradable aqueous zinc ion battery paper-based diaphragm obtained by the above preparation method.

[0021] Finally, the present invention provides an aqueous zinc ion battery, whose diaphragm is the above-mentioned degradable aqueous zinc ion battery paper-based diaphragm.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) Compared with traditional commercial glass fibers, the present invention uses a paper-based material made of natural cellulose as an aqueous zinc-ion battery separator, which exhibits excellent biodegradability and is more environmentally friendly. In addition, paper-based materials are ideal for flexible membrane materials due to their soft and flexible properties, surpassing the flexibility limitations of glass fibers. From an economic perspective, paper-based materials are cheaper as a material, and the preparation process is relatively economical and efficient. More importantly, the excellent processing properties of paper-based separators enable them to easily cope with a variety of process requirements such as cutting, folding, and molding, providing great convenience and flexibility for a variety of preparation processes.

[0024] (2) Compared with the modification of paper-based membranes with single components of chitosan or halloysite nanotubes, when the two are combined to form a composite material, the advantages are significant. Chitosan contains rich amino and hydroxyl groups, has good hydrophilicity and ion exchange capacity, and can improve the ion conductivity of the membrane. Halloysite nanotubes, as a layered silicate mineral, have high ion adsorption capacity and good ion transmission performance. When chitosan and halloysite nanotubes are combined to form a composite material, the synergistic effect of the two optimizes the chemical properties. Chitosan has good biocompatibility and adhesion, and can be tightly combined with paper fibers, while the high ion adsorption capacity and ion transmission performance of halloysite nanotubes can further improve the selective permeability and ion conductivity of the membrane surface. In addition, the combination of the two can also form a more uniform ion transmission channel, effectively blocking the growth and piercing of zinc dendrites, and improving the safety and cycle stability of the battery.

[0025] (3) Compared with ordinary disordered adsorption, the present invention strictly controls the ratio of chitosan to halloysite nanotubes and limits the mixing time of the two, so that the halloysite nanotubes can be fully and evenly combined with the network structure of chitosan and adhere to the paper fibers, thereby promoting the uniform diffusion of ions and optimizing the electric field distribution on the surface of the zinc negative electrode, achieving uniform deposition of zinc ions on the negative electrode, and effectively preventing the occurrence of the "dead zinc" phenomenon, thereby alleviating the capacity decay problem of aqueous zinc ion batteries during long-term cycling; in addition, chitosan is a natural polysaccharide obtained by deacetylation of chitin, has good biocompatibility and degradability, and helps to reduce the potential harm of batteries to the environment and human health.

[0026] (4) When the chitosan and halloysite nanotube composite material is used as a modified paper-based diaphragm of an aqueous zinc ion battery, the permeability of the diaphragm can be enhanced, the rapid and uniform diffusion of ions in the electrolyte can be promoted, the formation of zinc dendrites can be reduced, and the charge and discharge efficiency of the battery can be improved. At the same time, a protective film can be formed on the outside of the diaphragm to avoid short circuits and battery failures caused by zinc dendrites piercing the diaphragm. In addition, the composite material can also improve the overall mechanical properties of the diaphragm and enhance the stability and durability of the battery structure.

[0027] (5) Compared with the existing reported aqueous zinc-ion battery separator modification layer, the present invention innovatively introduces a natural, environmentally friendly and degradable separator material, which is characterized by low raw material cost, complete elimination of the use of hazardous chemicals in the production process, greatly simplified operation procedures, and the ability to accurately control the content of the modification. These advantages are of immeasurable significance for accelerating the process of aqueous zinc-ion battery technology towards commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 X-ray diffraction patterns of the diaphragms prepared in Comparative Example 1 and Example 1;

[0029] Figure 2 This is a scanning electron microscope image of the diaphragm prepared in Comparative Example 1;

[0030] Figure 3 This is a scanning electron microscope image of the diaphragm prepared in Example 1;

[0031] Figure 4 The AC impedance spectra of the diaphragms prepared in Comparative Example 1 and Example 1;

[0032] Figure 5 The Tafel curves of the diaphragms prepared in Comparative Example 1 and Example 1;

[0033] Figure 6 For a symmetrical battery assembled with the separator prepared in Comparative Example 1, at 1 mA·cm -2 The current density and 1 mAh cm -2 The negative electrode deposition state diagram after 120h of cycling at a deposition capacity of;

[0034] Figure 7 For a symmetrical battery assembled with the separator prepared in Example 1, at 1 mA·cm -2 The current density and 1 mAh cm -2 The negative electrode deposition state diagram after 120h of cycling at a deposition capacity of;

[0035] Figure 8 For symmetrical cells assembled with the separators prepared in Comparative Example 1, Comparative Example 2 and Example 1, at 1 mA·cm -2The current density and 1 mAh cm -2 The voltage-time diagram obtained at the deposition capacity; DETAILED DESCRIPTION

[0036] The technical content and effects of the present invention are further described in detail below in conjunction with the embodiments, but the present invention is not limited thereto.

[0037] Example 1

[0038] (1) A qualitative filter paper with a thickness of 0.180 mm was selected as the base material of the paper-based diaphragm.

[0039] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at a frequency of 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0040] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0041] (4) soaking the filter paper in the composite solution prepared in step (3) at 40° C. for 24 hours, and drying to obtain the filter paper having a composite material of chitosan and halloysite nanotubes;

[0042] (5) Cut the filter paper having the composite material of chitosan and halloysite nanotubes into diaphragm discs with a diameter of 1.6 cm.

[0043] Example 2

[0044] (1) A qualitative filter paper with a thickness of 0.180 mm was selected as the base material of the paper-based diaphragm.

[0045] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0046] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0047] (4) spin coating the composite solution obtained in step (3) on filter paper at 40° C., and drying to obtain filter paper having a composite material of chitosan and halloysite nanotubes;

[0048] (5) Cut the filter paper having the composite material of chitosan and halloysite nanotubes into diaphragm discs with a diameter of 1.6 cm.

[0049] Example 3

[0050] (1) A qualitative filter paper with a thickness of 0.180 mm was selected as the base material of the paper-based diaphragm.

[0051] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0052] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0053] (4) coating the composite solution obtained in step (3) on filter paper at 40° C., and drying to obtain filter paper having a composite material of chitosan and halloysite nanotubes;

[0054] (6) Cut the filter paper having the composite material of chitosan and halloysite nanotubes into diaphragm discs with a diameter of 1.6 cm.

[0055] Example 4

[0056] (1) Weighing paper with a thickness of 0.080 mm was selected as the base material of the paper-based diaphragm.

[0057] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at a frequency of 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0058] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0059] (4) soaking the weighing paper in the composite solution prepared in step (3) at 40° C. for 24 hours, and drying to obtain the weighing paper having a composite material of chitosan and halloysite nanotubes;

[0060] (5) Cut the weighing paper having the composite material of chitosan and halloysite nanotubes into diaphragm discs with a diameter of 1.6 cm.

[0061] Example 5

[0062] (1) Commercial printing paper with a thickness of 0.260 mm was selected as the base material of the paper-based diaphragm.

[0063] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at a frequency of 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0064] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0065] (4) soaking the commercial printing paper in the composite solution prepared in step (3) at 40° C. for 24 hours, and drying to obtain the commercial printing paper having a composite material of chitosan and halloysite nanotubes;

[0066] (5) The commercial printing paper having the composite material of chitosan and halloysite nanotubes was cut into diaphragm discs with a diameter of 1.6 cm.

[0067] Example 6

[0068] (1) Commercial printing paper with a thickness of 0.080 mm was selected as the base material of the paper-based diaphragm.

[0069] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at a frequency of 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0070] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0071] (4) coating the composite solution obtained in step (3) on a weighing paper at 40° C., and drying to obtain a weighing paper having a composite material of chitosan and halloysite nanotubes;

[0072] (5) The commercial printing paper having the composite material of chitosan and halloysite nanotubes was cut into diaphragm discs with a diameter of 1.6 cm.

[0073] Comparative Example 1 (Pure Paper-Based Separator)

[0074] (1) A qualitative filter paper with a thickness of 0.180 mm was selected as the base material of the paper-based diaphragm.

[0075] (2) Cut the filter paper membrane into membrane discs with a diameter of 1.6 cm.

[0076] Comparative Example 2 (Paper-based membrane modified with single component chitosan)

[0077] (1) A qualitative filter paper with a thickness of 0.180 mm was selected as the base material of the diaphragm.

[0078] (2) 0.1 mL of glacial acetic acid (HAc), 1.5 mL of polyethylene glycol (PEG), and 0.2 g of chitosan were added to 10 mL of deionized water and stirred at 40 °C for 12 h to obtain a chitosan solution;

[0079] (3) soaking the filter paper in the chitosan solution prepared in step (2) at 40° C. for 24 hours, and drying to obtain a chitosan filter paper having a single component;

[0080] (4) The chitosan filter paper having a single component is cut into diaphragm discs with a diameter of 1.6 cm.

[0081] Comparative Example 3 (Halloysite nanotube composite material with reduced chitosan ratio based on Example 1)

[0082] (1) A qualitative filter paper with a thickness of 0.180 mm was selected as the base material of the paper-based diaphragm.

[0083] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0084] (3) adding 0.05 mL of glacial acetic acid, 0.75 mL of polyethylene glycol and 0.1 g of chitosan to the suspension obtained in step (2), stirring and compounding at 40° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0085] (4) soaking the filter paper in the composite solution prepared in step (3) at 40° C. for 24 hours, and drying to obtain the filter paper having a composite material of chitosan and halloysite nanotubes;

[0086] (5) Cut the filter paper having the composite material of chitosan and halloysite nanotubes into diaphragm discs with a diameter of 1.6 cm.

[0087] Comparative Example 4 (Based on Example 1, the compounding temperature was changed)

[0088] (1) Select qualitative filter paper with a thickness of 0.180 mm and a slow filtration rate as the material of the paper-based diaphragm.

[0089] (2) adding 300 mg of halloysite nanotubes to 10 mL of deionized water and stirring for 24 h, and then ultrasonicating at a frequency of 75 kHz for 15 min at 25° C. to completely disperse the halloysite nanotubes to obtain a halloysite nanotube suspension;

[0090] (3) adding 0.1 mL of glacial acetic acid, 1.5 mL of polyethylene glycol and 0.2 g of chitosan to the suspension obtained in step (2), stirring and compounding at 25° C. for 12 h to obtain a composite solution of halloysite nanotubes and chitosan;

[0091] (4) soaking the filter paper in the composite solution prepared in step (3) at 25° C. for 24 hours, and drying to obtain the filter paper having a composite material of chitosan and halloysite nanotubes;

[0092] (5) Cut the filter paper having the composite material of chitosan and halloysite nanotubes into diaphragm discs with a diameter of 1.6 cm.

[0093] Performance Testing

[0094] The discs obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were used as battery separators, and zinc sheets were used as positive and negative electrodes of the battery. -1 Zinc sulfate solution was used as the electrolyte to assemble a symmetrical battery. The assembled zinc ion symmetrical battery was placed in a constant temperature environment at 25°C for 2 h and charged at 1 mA·cm -2 The current density and 1 mAh cm -2 The cycling performance test was carried out at a deposition capacity of .

[0095] Table 1

[0096] Case Polarization voltage(V) Maximum cycle time (h) Example 1 0.1 2000 Example 2 0.1 1500 Example 3 0.12 1800 Example 4 0.09 2000 Example 5 0.1 1800 Example 6 0.11 1600 Comparative Example 1 0.18 190 Comparative Example 2 0.12 1030 Comparative Example 3 0.15 860 Comparative Example 4 0.16 1000

[0097] As can be seen from Table 1, compared with the chitosan modification of a single component in Comparative Example 2, the filter paper membrane modified with halloysite nanotubes and chitosan in Example 1 improves the diffusion rate of ions in the membrane, has a longer cycle life and a lower polarization voltage. The addition of a small amount of chitosan in Comparative Example 3 and the change of the composite temperature in Comparative Example 4 affect the uniformity of the combination of the two, resulting in a decrease in the zinc ion transmission efficiency and a significant impact on the cycle performance of the battery.

[0098] Depend on Figure 1 It can be seen that a strong peak of dendrite by-products appeared in the X-ray diffraction peak of the pure filter paper after cycling (Comparative Example 1), while there was no peak in the filter paper diaphragm modified with halloysite nanotubes and chitosan (Example 1), indicating that the modified layer can inhibit the formation of dendrite by-products on the zinc negative electrode during the battery cycle and protect the diaphragm from being corroded or pierced by dendrites.

[0099] Depend on Figure 2It can be seen that the pure filter paper membrane (Comparative Example 1) is composed of many fibers of different sizes and thicknesses, and the pores on the surface are relatively large and very unevenly distributed.

[0100] Depend on Figure 3 It can be seen that the surface of the filter paper membrane modified with chitosan and halloysite nanotubes (Example 1) is very smooth, wherein chitosan evenly fixes the halloysite nanotubes on the surface of the filter paper fibers, improves the macroporous structure of the pure filter paper, and is conducive to guiding uniform zinc deposition.

[0101] Depend on Figure 4 It can be seen that the interfacial impedance of the pure filter paper membrane (Comparative Example 1) reaches more than 1200Ω, indicating that the electrolyte / electrode interface is very unstable at this time, which is related to the accumulation of by-products and the growth of zinc dendrites. The filter paper membrane modified with chitosan and halloysite nanotubes (Example 1) shows a smaller interfacial impedance, indicating that the filter paper modification layer weakens the interface effect.

[0102] Depend on Figure 5 It can be seen that in the three-electrode system test of the corrosion resistance of zinc sheets under different membranes, the corrosion potential of the Zn electrode measured in the filter paper membrane modified with chitosan and halloysite nanotubes (Example 1) is -0.01V, which is positively correlated with the -0.019V measured in the pure filter paper membrane (Comparative Example 1).

[0103] Depend on Figure 6 It can be seen that after 120 minutes of circulation, a large number of non-uniform flakes are formed on the surface of the pure zinc sheet (Comparative Example 1) under the pure filter paper diaphragm, and a large number of by-products are generated.

[0104] Depend on Figure 7 It can be seen that after 120 min of circulation, the filter paper membrane modified with chitosan and halloysite nanotubes (Example 1) exhibits a uniform and dense zinc deposition layer without dendrites.

[0105] Depend on Figure 8 It can be seen that when the filter paper modified with halloysite nanotubes and chitosan proposed in the present invention is used as a diaphragm of an aqueous zinc ion battery, the battery cycle stability is significantly improved, and it can operate stably for 2000 hours. The overpotential of zinc deposition / stripping is significantly reduced, showing a smaller electrode polarization phenomenon; the single-component chitosan-modified diaphragm has the above-mentioned problems such as uneven diffusion of ions and accumulation of by-products, resulting in increasing polarization and a short circuit at around 1030 hours; the unmodified filter paper diaphragm causes a short circuit after 190 hours of circulation due to zinc dendrites piercing the diaphragm.

[0106] The above embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a degradable paper-based diaphragm for aqueous zinc ion batteries, characterized in that: The steps include: (1) adding halloysite nanotubes into water and dispersing by ultrasonication to obtain a suspension of halloysite nanotubes; (2) adding glacial acetic acid, polyethylene glycol and chitosan to the halloysite nanotube suspension, stirring evenly for compounding, and obtaining a composite slurry; (3) The composite slurry is evenly coated on the surface of the paper-based diaphragm, dried, and a coating is formed to obtain a degradable aqueous zinc ion battery paper-based diaphragm.

2. The preparation method according to claim 1, characterized in that In step (1), the concentration of the halloysite nanotube suspension is 0.1 to 0.3 g / mL.

3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of chitosan to halloysite nanotubes is 1:(0.2-0.5).

4. The preparation method according to claim 1 or 3, characterized in that: In step (2), the stirring condition is 20-40° C. for 3-24 h.

5. The preparation method according to claim 1, characterized in that: In step (3), the paper-based membrane is filter paper, weighing paper or commercial printing paper.

6. The preparation method according to claim 1, characterized in that: In step (3), the coating method is immersion, filtration, drip coating or spin coating.

7. The preparation method according to claim 1, characterized in that: In step (3), the thickness of the coating is 20 to 80 μm.

8. A degradable aqueous zinc ion battery paper-based diaphragm obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the degradable aqueous zinc ion battery paper-based diaphragm as claimed in claim 8 in aqueous zinc ion batteries.

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