Bamboo nanofiber diaphragm and application thereof in aqueous zinc ion battery

Abstract

The invention provides a bamboo nanofiber diaphragm and application thereof in an aqueous zinc ion battery, and the bamboo nanofiber diaphragm is prepared by the following method: (1) mixing bamboo powder with an alkaline solution, and then carrying out ball milling and ultrasonic dispersion to form a micro-nano bamboo powder mixed solution; (2) a delignification reagent is added into the micro-nano bamboo powder mixed solution, lignin is partially removed through heat treatment, and a mixed solution is obtained; and (3) carrying out suction filtration on the mixed solution in the step (2) to form a film, drying, and soaking and activating in a zinc source. The preparation method of the bamboo nanofiber diaphragm provided by the invention is simple, the raw materials are easy to obtain and low in cost, and the prepared lignin-containing aperture-controllable nanocellulose diaphragm has good stability, liquid retention capability and ionic conductivity, and shows excellent cycle capacity and service life when being applied to an aqueous zinc ion battery.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a bamboo nanofiber separator and its application in aqueous zinc-ion batteries. Background Technology

[0002] Aqueous zinc-ion batteries have become a preferred technology for large-scale energy storage due to their high theoretical capacity of the zinc anode (820 mAh / g), environmentally friendly and non-toxic electrolyte, and low cost. The separator, as a core component of the battery, must simultaneously fulfill three major functions: "isolating short circuits between the positive and negative electrodes," "providing ion transport channels," and "inhibiting zinc dendrite growth."

[0003] Currently, there are many types of separators for aqueous zinc-ion batteries. Glass fiber separators are already commercially available, but although they are low in cost, they have poor mechanical strength (tensile strength of only 0.54 MPa) and uncontrollable pore size (2-5 μm), making them unable to prevent zinc dendrite penetration. Their cycle life is typically <100 cycles; for example, Whatman GF / D separators fail after only 30 hours of cycling. Therefore, developing high-performance separators is key to comprehensively improving battery performance.

[0004] In existing technologies, biomass is considered as a raw material for developing separators. For example, invention patent CN116613463A discloses a cellulose battery separator with improved mechanical properties through lignin sulfonate, its preparation method, and its application. The method includes the following steps: 1) preparing a polyvinyl alcohol solution; 2) mixing lignin sulfonate, polyvinyl alcohol solution, sodium hydroxide, urea, and water; 3) adding cellulose to the pre-cooled mixture and stirring to dissolve, obtaining a cellulose-based solution; 4) ultrasonically dispersing and centrifuging the cellulose-based solution to obtain a casting solution; 5) casting the casting solution onto a glass plate and obtaining a gel-like sheet through a casting method, then immersing it in a coagulation bath for curing and regeneration; 6) washing and vacuum freeze-drying the cured material to obtain a cellulose battery separator with improved mechanical properties through lignin sulfonate. While this method enhances the mechanical properties of the cellulose battery separator by adding lignin sulfonate, lignin is an exogenous addition, and the water-soluble lignin sulfonate lacks durability and stability in the electrolyte.

[0005] For example, invention patent CN112397850A discloses a modified lignocellulose separator for lithium-ion batteries, its preparation method, and its application. This lignocellulose separator is obtained by treating a 30–300 μm thick natural wood film with a mixed alkaline solution, placing it in a vacuum environment to allow the mixed alkaline solution to fully penetrate the wood film, and then subjecting it to high-temperature treatment. However, this method relies on a vacuum high-temperature process, is costly, and has uncontrollable pore size, making it unable to effectively suppress zinc dendrites.

[0006] In summary, existing membranes generally suffer from problems such as uncontrollable pore size, limited lignin function, and complex processes. Therefore, there is an urgent need to develop a pore size-adaptive Zn membrane. 2+ A biomass membrane that combines transport and lignin functions, and features a green and low-cost manufacturing process. Summary of the Invention

[0007] To address the aforementioned technical problems in existing technologies, this invention provides a bamboo nanofiber separator and its application in aqueous zinc-ion batteries. Using biomass as raw material, lignocellulose fibers are prepared through simple pretreatment, and polar groups are introduced onto the fiber surface. The separator pore size is also controlled, which has great application potential and practical value. The resulting functional cellulose separator has a simple preparation process, excellent electrochemical performance, and is environmentally friendly, which is of great significance for promoting the large-scale development of aqueous zinc-ion batteries.

[0008] This invention provides a method for preparing a bamboo nanofiber membrane, comprising the following steps: (1) Bamboo powder is mixed with an alkaline solution and then ball-milled to form a micro-nano bamboo powder mixture; (2) Add a lignin-removing agent to the micro-nano bamboo powder mixture, and partially remove lignin by heat treatment to obtain the mixture; (3) The mixture in step (2) is filtered into a membrane and dried, and then placed in a zinc source for activation to obtain a bamboo nanofiber membrane.

[0009] This invention utilizes the impact and shearing action of grinding balls during ball milling to break down bamboo powder cellulose. An alkaline solution is used to weaken the hydrogen bonding between cellulose and lignin. Furthermore, the cavitation effect of ultrasound disperses the fibers, preventing agglomeration and forming a homogeneous bamboo powder mixture. By adding a delignification reagent to adjust the delignification process parameters, the amount of lignin residue is precisely controlled. The amount of lignin residue is negatively correlated with pore size, making it perfectly compatible with Zn. 2+ It can transport and block zinc dendrites; and the residual lignin acts as a "scaffold" to guide the self-assembly of cellulose nanofibers to form uniform channels; the relative hydrophobicity of lignin can reduce the swelling of cellulose by the electrolyte, avoid channel collapse, and improve the long-term stability of the membrane.

[0010] Preferably, in step (1), bamboo powder and alkaline solution are mixed at a mass ratio of (1~10):100.

[0011] Preferably, in step (1), the bamboo powder has a particle size of 20-200 mesh and is selected from one or more of the following: moso bamboo, cinnamon bamboo, phoenix tail bamboo, Xiangfei bamboo, and giant dragon bamboo.

[0012] More preferably, the bamboo powder has a particle size of 40-60 mesh.

[0013] Preferably, in step (1), the alkaline solution is a 0.1-5 wt% sodium hydroxide solution.

[0014] By using sodium hydroxide solution to weaken the hydrogen bonding between cellulose and lignin, the cavitation effect of subsequent ultrasound can further disperse the fibers and prevent aggregation.

[0015] Preferably, in step (1), the ball milling speed is 100-1000 rpm and the ball milling time is 1-10 h.

[0016] By selecting the ball milling parameters within the above range, the bamboo powder fiber bundles can be fully broken, which facilitates the subsequent formation of cellulose nanofibers.

[0017] More preferably, the ball mill rotation speed is 300-700 rpm, and the ball milling time is 3-8 h.

[0018] By using ball milling parameters within this range, cellulose nanofibers with a suitable diameter range can be formed.

[0019] Preferably, in step (1), the ultrasonic dispersion power is 300-500 W and the ultrasonic dispersion time is 10-30 min.

[0020] Ultrasonic dispersion within the above parameter range can effectively avoid agglomeration and ensure uniform fiber dispersion; further, it can be combined with ball milling to achieve efficient dissociation of bamboo powder.

[0021] Preferably, in step (2), the delignification agent is 0.5-6 wt% sodium hypochlorite or 0.5-6 wt% acid; The acid is selected from one or more of acetic acid, hydrochloric acid, and sulfuric acid.

[0022] Sodium hypochlorite preferentially oxidizes the aromatic ring structure of lignin, while acid solutions (such as sulfuric acid) preferentially hydrolyze the bonds connecting lignin to cellulose and hemicellulose. Furthermore, by adjusting the reagent concentration, temperature, and time, the amount of lignin residue can be precisely controlled.

[0023] Preferably, in step (2), the heat treatment temperature is 70-90℃ and the heat treatment time is 60-120 min.

[0024] Preferably, in step (3), the drying temperature is -50°C and the drying time is 48 h.

[0025] Preferably, in step (3), the zinc source is one or more of a 0.5-12 mol / L zinc sulfate solution, zinc chloride solution, and zinc trifluoromethanesulfonate solution.

[0026] More preferably, in step (3), the zinc source is a 1-3 mol / L zinc sulfate solution.

[0027] Preferably, in step (3), the soaking and activation time is 1-24 h.

[0028] More preferably, in step (3), the soaking and activation time is 2-12 h.

[0029] This invention provides a bamboo nanofiber membrane prepared by the preparation method described above.

[0030] The membrane prepared by the above method has a "micron-nanofiber interwoven network" structure: cellulose nanofibers (diameter 2-10 nm) overlap with residual lignin particles (particle size less than 10 nm); the relative hydrophobicity of lignin can stabilize the three-dimensional pore structure and prevent the pores from collapsing in the electrolyte, while its surface polar groups (hydroxyl, carboxyl groups) can accelerate the desolvation of hydrated zinc ions.

[0031] Preferably, the bamboo nanofiber membrane has a lignin residue of 5-25%, a pore size of 10-100 nm, and a thickness of 30-80 μm.

[0032] The lignin residue, pore size, and thickness range are perfectly suited for use in aqueous zinc-ion batteries. 2+ To meet transmission requirements and avoid the problem of high ion transport resistance (high impedance) caused by the uneven pore size of existing nanocellulose membranes.

[0033] More preferably, the bamboo nanofiber membrane has a lignin residue of 7-10%.

[0034] Preferably, the electrolyte absorption rate of the bamboo nanofiber membrane is greater than or equal to 350%.

[0035] The present invention provides an aqueous zinc-ion battery, comprising a positive electrode, an electrolyte, the aforementioned bamboo nanofiber separator, and a negative electrode.

[0036] Preferably, the positive electrode is selected from one or more of transition metal oxides, Prussian blue compounds, metal sulfides, and organic-inorganic composite materials.

[0037] Preferably, the electrolyte is a 1-3 mol / L zinc sulfate solution. More preferably, the electrolyte is a 2 mol / L zinc sulfate solution.

[0038] Preferably, the negative electrode is selected from one or more of metallic zinc, zinc-plated metal materials, and zinc-plated carbon materials.

[0039] Compared with the prior art, the present invention has the following beneficial effects: (1) Using waste bamboo powder as raw material, the process uses non-toxic solvents. Through ball milling and ultrasonic synergy, bamboo powder is efficiently micronized and nano-sized. The residual amount of lignin is precisely controlled to regulate the pore size, which can perfectly adapt to Zn. 2+ To meet transmission requirements, the mechanical properties of the separator are significantly enhanced to resist zinc dendrite puncture. It has good stability, liquid retention capacity and ionic conductivity, and shows excellent cycle capacity and life when applied to aqueous zinc-ion batteries.

[0040] (2) The assembled aqueous zinc-ion battery retains a specific capacity of ≥95% and a coulombic efficiency of ≥99.5% after 1000 cycles, and the interface impedance is also significantly reduced.

[0041] (3) The cost of bamboo powder raw materials is only 1 / 5 of that of glass fiber, and the energy consumption of the process is reduced by 30% compared with the existing biomass membrane. Attached Figure Description

[0042] Figure 1 An atomic micrograph (AFM) of the bamboo nanofiber membrane of Example 1 of the present invention.

[0043] Figure 2 This is a scanning electron microscope (SEM) image of the bamboo nanofiber membrane of Example 1 of the present invention.

[0044] Figure 3 This is a scanning electron microscope (SEM) image of a commercially available glass fiber diaphragm, which is Comparative Example 1 of this invention.

[0045] Figure 4 This is a scanning electron microscope (SEM) image of the diaphragm in Comparative Example 2 of this invention.

[0046] Figure 5 This is a scanning electron microscope (SEM) image of the diaphragm in Comparative Example 3 of this invention.

[0047] Figure 6 This is a scanning electron microscope (SEM) image of the diaphragm in Comparative Example 4 of this invention.

[0048] Figure 7 Raman spectroscopy was performed on the lignin distribution of the bamboo nanofiber membrane in Example 1 of this invention.

[0049] Figure 8 The compositional analysis of lignin content in the bamboo nanofiber membranes of Examples 1-5 of the present invention.

[0050] Figure 9 The tensile strength and elongation at break of Embodiment 1 and Comparative Example 1 of the present invention are shown.

[0051] Figure 10 The charge / discharge capacity ratio and coulombic efficiency of Embodiment 1 and Comparative Example 1 of the present invention are given. Detailed Implementation

[0052] To further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples.

[0053] All raw materials were purchased from the market.

[0054] Example 1 (1) Bamboo powder pretreatment: Take 20 g of moso bamboo powder with a particle size of 60-120 mesh, mix it with 100 g of sodium hydroxide solution with a concentration of 1wt%, pour it into a planetary ball mill jar, ball mill at 200 rpm for 8 h, and then ultrasonically disperse it at 400 W for 20 min to obtain micro-nano bamboo powder mixture. (2) Partial deligninization: Sodium hypochlorite with a concentration of 4wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70℃ for 1 h. After washing until neutral, the lignin content was measured to be 7.43%. (3) Film formation and activation: The mixture was adjusted to a solid content of 0.5wt%, 30 ml was filtered to form a film, and the film was freeze-dried at -50℃ for 48 h. The film was cut into 18 mm round pieces and soaked in 2 mol / L zinc sulfate solution for 12 h to obtain a bamboo nanofiber membrane (LF-4) with a thickness of 72 μm and a pore size of 30-80 nm. At this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 400%.

[0055] (4) Battery assembly and testing: Zinc metal was used as the negative electrode (purity ≥99%, diameter 15 mm, thickness 100 µm); vanadium pentoxide was used as the active material. The active material, SuperP, and sodium carboxymethyl cellulose were mixed in a mass ratio of 7:2:1, with deionized water as the solvent, and stirred to form a homogeneous slurry. The slurry was then uniformly coated onto a 304 stainless steel current collector with a coating thickness of 100 μm. After drying at 60℃ for 24 h, it was cut into discs with a diameter of 15 mm. The loading of the active material was 1.5-2.5 mg / cm³. 2 CR2032 coin cells were assembled using 2 mol / L zinc sulfate as the electrolyte. Taking a full cell as an example, non-conductive tweezers were used to assemble the CR2032 coin cells in the following order: negative electrode shell, spring contact, steel sheet, negative electrode plate, electrolyte membrane, positive electrode plate, and positive electrode shell. The assembled cells were then placed on a hydraulic sealing machine, pressurized to a certain pressure, and held for 5 seconds to seal the cells. All assembled cells were left to stand for at least 1 hour before testing. The obtained coin cells were tested for charge and discharge performance at room temperature using a Newway battery testing system (CT4008-5V50 mA), with a voltage range of 0.2-1.6 V and a current density of 0.5 A / g.

[0056] At a current density of 0.5 A / g, the specific capacity after 1000 cycles is 200 mAh / g, the maximum specific capacity is 430 mAh / g, the coulombic efficiency is 99.7%, and the ionic conductivity is 6.7 mS·cm. -1 The zinc ion transference number is 0.7.

[0057] Example 2 The preparation method of Example 2 is the same as that of Example 1, except that: (2) Partial deligninization: Sodium hypochlorite with a concentration of 0.5 wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70°C for 1 h. After washing until neutral, the lignin content was measured to be 22.0%. (3) Film formation and activation: A bamboo nanofiber membrane (LF-0.5) with a thickness of 71 μm and a pore size of 10-100 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 360%. (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity was 101 mAh / g, the maximum specific capacity was 282 mAh / g, the coulombic efficiency was 99.2%, and the ionic conductivity was 4.3 mS·cm. -1 The zinc ion transference number is 0.42.

[0058] Example 3 The preparation method of Example 3 is the same as that of Example 1, except that: (2) Partial deligninization: Sodium hypochlorite with a concentration of 1 wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70°C for 1 h. After washing until neutral, the lignin content was measured to be 13.12%. (3) Film formation and activation: A bamboo nanofiber membrane (LF-1) with a thickness of 70 μm and a pore size of 10-90 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 370%; (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity is 100 mAh / g, the maximum specific capacity is 290 mAh / g, the coulombic efficiency is 99.3%, and the ionic conductivity is 6.1 mS·cm. -1 The zinc ion transference number is 0.5.

[0059] Example 4 The preparation method of Example 4 is the same as that of Example 1, except that: (2) Partial deligninization: Sodium hypochlorite with a concentration of 2wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70℃ for 1 h. After washing until neutral, the lignin content was measured to be 8.91%. (3) Film formation and activation: A bamboo nanofiber membrane (LF-2) with a thickness of 69 μm and a pore size of 20-80 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 390%. (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity is 120 mAh / g, the maximum specific capacity is 310 mAh / g, the coulombic efficiency is 99.4%, and the ionic conductivity is 6.3 mS·cm. -1 The zinc ion transference number is 0.58.

[0060] Example 5 The preparation method of Example 5 is the same as that of Example 1, except that: (2) Partial deligninization: Sodium hypochlorite with a concentration of 6 wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70℃ for 1 h. After washing until neutral, the lignin content was measured to be 5.09%. (3) Film formation and activation: A bamboo nanofiber membrane (LF-6) with a thickness of 71 μm and a pore size of 20-60 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 420%. (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity is 150 mAh / g, the maximum specific capacity is 350 mAh / g, the coulombic efficiency is 99.7%, and the ionic conductivity is 9.2 mS·cm. -1 The zinc ion transference number is 0.63.

[0061] Comparative Example 1 Comparative Example 1: Glass fiber (Whatman GF / D1823-090) was cut into discs with an inner diameter of 18 mm and then immersed in a 2 mol / L zinc sulfate aqueous solution for 12 h to obtain a commonly used glass fiber separator (GF). The fiber diameter was approximately 1 µm, the pore size was 2.7 µm, the thickness was 67.5 µm, the electrolyte absorption rate was 190%, and after 1000 cycles at a current density of 0.5 A / g following battery assembly, the specific capacity decreased to 100 mAh / g.

[0062] Comparative Example 2 The preparation method of Comparative Example 2 is the same as that of Example 1, except that: (2) Partial deligninization: Sodium hypochlorite with a concentration of 10 wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70℃ for 6 h. After washing until neutral, the lignin content was found to be close to 0%. (3) Film formation and activation: A bamboo nanofiber membrane with a thickness of 71 μm and a pore size of 5-10 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 450%. (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity was 95 mAh / g, the maximum specific capacity was 270 mAh / g, the coulombic efficiency was 98.5%, and the ionic conductivity was 5.2 mS·cm. -1 The zinc ion transference number is 0.48.

[0063] Comparative Example 3 The preparation method of Comparative Example 3 is the same as that of Example 1, except that: (2) Partial deligninization: Add sodium hypochlorite at a concentration of 7 wt% to the micro-nano bamboo powder mixture, react in a water bath at 70℃ for 1 h, wash until neutral, and at this time the lignin content is measured to be 3%; (3) Film formation and activation: A bamboo nanofiber membrane with a thickness of 68 μm and a pore size of 10-30 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 430%. (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity is 100 mAh / g, the maximum specific capacity is 220 mAh / g, the coulombic efficiency is 97.5%, and the ionic conductivity is 6.2 mS·cm. -1 The zinc ion transference number is 0.52.

[0064] Comparative Example 4 The preparation method of Comparative Example 4 is the same as that of Example 1, except that: (2) Partial deligninization: Sodium hypochlorite with a concentration of 10 wt% was added to the micro-nano bamboo powder mixture, and the mixture was reacted in a water bath at 70℃ for 4 h. After washing until neutral, the lignin content was measured to be 25%. (3) Film formation and activation: A bamboo nanofiber membrane with a thickness of 71 μm and a pore size of 90-160 nm was obtained; at this time, the electrolyte absorption rate of the bamboo nanofiber membrane was 340%. (4) Battery assembly and testing: After 1000 cycles at a current density of 0.5 A / g, the specific capacity was 110 mAh / g, the maximum specific capacity was 260 mAh / g, the coulombic efficiency was 99.0%, and the ionic conductivity was 4.1 mS·cm. -1 The zinc ion transference number is 0.42.

[0065] Detection Example 1 The surface microstructure of the examples and comparative examples was characterized using scanning electron microscopy, atomic force microscopy, laser confocal Raman microscopy, and physical adsorption analysis. The results are shown in the figure. Figures 1-7 .

[0066] like Figure 1 The image shown is an AFM (atomic force microscope 2×2 μm) image of the surface of Embodiment 1 of the present invention. Figure 1The membrane exhibits a "cellulose-lignin interwoven network" with fiber diameters of approximately 2-10 nm, uniformly distributed lignin particles (particle size 10 nm), and no agglomeration in the pores.

[0067] Figure 2 This is a SEM image of the surface of the bamboo nanofiber membrane in Example 1 of the present invention. Figures 3-6 SEM images of the membranes from Comparative Examples 1, 2, 3, and 4 are shown, with the pore size distribution range statistically analyzed using D90. The comparison reveals that the bamboo nanofiber membrane prepared in this invention possesses a "micron-nanofiber interwoven network" structure: cellulose nanofibers (diameter 2-10 nm) overlap with residual lignin particles (particle size less than 10 nm), forming controllable pore sizes of 10-100 nm. The relative hydrophobicity of lignin stabilizes the three-dimensional pore structure, preventing pore collapse in the electrolyte, while its surface polar groups (hydroxyl, carboxyl groups) accelerate the desolvation of hydrated zinc ions.

[0068] Figure 7 For the Raman spectroscopy test of lignin distribution in Example 1 of this invention, the microscopic composition of lignin was analyzed by utilizing the 235 nm ultraviolet resonance enhancement effect. Figure 7 The left image in the image is a comparative line scan analysis of the lignin distribution signal. Figure 7 The right figure in the image is a line scan of the signal excited by a 235 nm deep ultraviolet laser. The results show that the imaging excitation wavelength of 235 nm has a strong resonance enhancement with the aromatic ring structure in lignin, which improves the contrast of lignin and enables surface-sensitive imaging. The cellulose signal is usually very weak and easily submerged, which confirms that lignin is uniformly distributed in the membrane and provides direct evidence for controllable pore size.

[0069] Detection Example 2 The thickness of different gel electrolyte membranes was measured using an electronic micrometer (accuracy 0.001 mm). Three points were randomly selected on the sample, and the average value was taken.

[0070] Detection Example 3 like Figure 8 The figure shows the lignin content test results of the diaphragms in Examples 1-5 of the present invention. Figure 8 It can be seen that after treatment with sodium hypochlorite at different concentrations for lignin removal, the lignin content shows a significant decreasing trend with increasing sodium hypochlorite concentration. This indicates that the lignin content and fiber pore size are controllable.

[0071] Detection Example 4 Figure 9 The tensile strength and elongation at break of Embodiment 1 and Comparative Example 1 of the present invention are obtained from... Figure 9 It can be seen that the tensile strength of Example 1 is about 90 MPa, which is 167 times that of commercial glass fiber membranes, demonstrating superior mechanical properties and confirming the enhancing effect of lignin on mechanical properties.

[0072] Figure 10 The charge / discharge capacity ratio and coulombic efficiency of Example 1 and Comparative Example 1 of the present invention are shown. Example 1, after 1000 cycles at a current density of 0.5 A / g, has a specific capacity of 430 mAh / g, which is 2.15 times that of the glass fiber membrane (200 mAh / g).

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a bamboo nanofiber separator, characterized by, The method comprises the following steps: (1) mixing bamboo powder with an alkaline solution, and then forming a micro-nano bamboo powder mixture by ball milling and ultrasonic dispersion; (2) adding a delignification agent to the micro-nano bamboo powder mixture, and partially removing lignin by heat treatment to obtain a mixture; (3) filtering the mixture in step (2) into a film and drying, and then soaking and activating in a zinc source to obtain a bamboo nanofiber separator.

2. The production method according to claim 1, characterized by, In step (1), the bamboo powder and the alkaline solution are mixed at a mass ratio of (1-10):100, wherein the alkaline solution is a 0.1-5 wt% sodium hydroxide solution.

3. The production method according to claim 1, characterized by, In step (1), the ball milling speed is 100-1000 rpm, and the ball milling time is 1-10 h. The ultrasonic dispersion power is 300-500 W, and the ultrasonic dispersion time is 10-30 min.

4. The method of claim 1, wherein, In step (2), the delignification agent is 0.5-6 wt% sodium hypochlorite or 0.5-6 wt% acid. The acid is selected from one or more of acetic acid, hydrochloric acid, and sulfuric acid.

5. The preparation method according to claim 1, characterized in that, In step (2), the heat treatment temperature is 70-90℃, and the heat treatment time is 60-120 min.

6. The method of claim 1, wherein, In step (3), the zinc source is one or more of 0.5-12 mol / L zinc sulfate solution, zinc chloride solution, and zinc triflate solution.

7. The preparation method according to claim 1, characterized in that, In step (3), the soaking and activating time is 1-24 h.

8. A bamboo nanofiber separator prepared by the preparation method of any one of claims 1-7.

9. The bamboo nanofiber separator of claim 8, wherein, The bamboo nanofiber separator has a lignin residual amount of 5-25%, a pore size of 10-100 nm, and a thickness of 30-80 μm.

10. Use of a bamboo nanofiber separator in a water-based zinc ion battery, characterized in that, The aqueous zinc ion battery comprises a positive electrode, an electrolyte, the bamboo nanofiber separator of claim 8 or 9, and a negative electrode.

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