Bamboo nanofiber separator and application thereof in aqueous zinc ion battery

Abstract

The application provides a bamboo nanofiber diaphragm and application thereof in aqueous zinc ion batteries, and the bamboo nanofiber diaphragm is prepared by the following method: (1) mixing bamboo powder with an alkaline solution, and then forming a micro-nanoized bamboo powder mixed solution through ball milling and ultrasonic dispersion; (2) adding a delignification reagent to the micro-nanoized bamboo powder mixed solution, and partially removing lignin through heat treatment to obtain a mixed solution; (3) filtering the mixed solution in step (2) into a film and drying, and then soaking and activating in a zinc source. The preparation method of the bamboo nanofiber diaphragm provided by the application is simple, raw materials are easy to obtain, and the cost is low; a lignin-containing nanocellulose diaphragm with controllable pore size is prepared, and the diaphragm has good stability, liquid retention capacity and ionic conductivity, and shows excellent cycle capacity and service life when applied in aqueous zinc ion batteries.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical energy storage, and particularly relates to a bamboo nanofiber diaphragm and application thereof in aqueous zinc ion batteries. BACKGROUND

[0002] Aqueous zinc ion batteries have become one of the preferred technologies in the field of large-scale energy storage because of the high theoretical capacity of zinc negative electrode (820 mAh / g), environmentally friendly and non-toxic electrolyte, and low cost. As a core component of the battery, the diaphragm needs to simultaneously achieve three functions: "isolating the positive and negative electrodes", "providing an ion transmission channel", and "inhibiting zinc dendrite growth".

[0003] At present, there are many types of diaphragms for aqueous zinc ion batteries. Glass fiber diaphragms have been commercially used, although they have low cost, poor mechanical strength (tensile strength of only 0.54 MPa), and uncontrollable pore size (2-5 μm), which cannot block zinc dendrites from puncturing, and the cycle life is usually <100 times. Therefore, the development of high-performance diaphragms is the key to improving the overall performance of the battery.

[0004] In the prior art, biomass is considered as a raw material to develop diaphragms. For example, the patent for invention with publication number CN116613463A discloses a cellulose battery diaphragm with improved mechanical properties by lignin sulfonate and its preparation method and application. The method comprises the following steps: 1) preparing a polyvinyl alcohol solution; 2) blending lignin sulfonate, polyvinyl alcohol solution, sodium hydroxide, urea, and water; 3) stirring and dissolving the blended solution after pre-cooling to obtain a cellulose-based solution; 4) ultrasonic dispersion and centrifugation of the cellulose-based solution to obtain a casting solution; 5) casting the casting solution on a glass plate and obtaining a gel-like sheet by the flow casting method, then immersing it in a coagulation bath for solidification and regeneration; 6) washing and vacuum freeze-drying the solidified material to obtain a cellulose battery diaphragm with improved mechanical properties by lignin sulfonate. The cellulose battery diaphragm provided by the method enhances the mechanical properties by adding lignin sulfonate, but lignin is exogenously added, and the durability and stability of water-soluble lignin sulfonate in the electrolyte are insufficient.

[0005] For another example, the patent for invention with publication number CN112397850A discloses a modified wood cellulose diaphragm for lithium ion batteries and its preparation method and application. The wood cellulose diaphragm is obtained by treating a natural wood film with a thickness of 30-300 μm with a mixed alkali solution, immersing the wood film in the mixed alkali solution in a vacuum environment, and then treating it at high temperature. However, this method relies on vacuum high-temperature processes, has high cost, and uncontrollable pore size, and cannot effectively inhibit zinc dendrites.

[0006] In summary, the existing technology prepared separator generally exists the problems of uncontrolled pore size, single function of lignin and complex process, and it is urgent to develop a biomass separator with pore size adapting to Zn 2+ transport, lignin function composite and green and low-cost process. SUMMARY

[0007] To solve the above technical problems in the prior art, the present application provides a bamboo nanofiber separator and its application in aqueous zinc ion battery, which uses biomass as raw material, and prepares lignocellulose fiber by simple pretreatment and introduces polar groups on the fiber surface and regulates the pore size of the separator, which has great application potential and practical value, and the functional cellulose separator developed by the simple preparation process, excellent electrochemical performance and environmental friendliness is of great significance to promote the large-scale development of aqueous zinc ion battery.

[0008] The present application provides a preparation method of bamboo nanofiber separator, comprising the following steps:

[0009] (1) mixing bamboo powder with alkaline solution, and then forming micro-nano bamboo powder mixed solution by ball milling;

[0010] (2) adding delignification reagent to the micro-nano bamboo powder mixed solution, partially removing lignin by heat treatment to obtain a mixed solution;

[0011] (3) filtering the mixed solution in step (2) into a film and drying, and then activating in zinc source to obtain a bamboo nanofiber separator.

[0012] In the ball milling process, the impact and shearing action of the grinding balls break the bamboo cellulose, the alkaline solution weakens the hydrogen bond between cellulose and lignin, and the cavitation effect of ultrasonic is further combined to disperse the fibers and avoid agglomeration, forming a uniform bamboo powder mixed solution; by adding delignification reagent to regulate the delignification process parameters, the residual amount of lignin is accurately controlled, the residual amount of lignin is negatively correlated with the pore size, and the Zn 2+ transport and zinc dendrite blocking can be perfectly adapted; and the residual lignin acts as a "scaffold" to guide the self-assembly of cellulose nanofiber to form uniform pores; the relative hydrophobicity of lignin can reduce the swelling of electrolyte on cellulose, avoid the collapse of pores, and improve the long-term stability of the separator.

[0013] Preferably, in step (1), the bamboo powder is mixed with the alkaline solution at a mass ratio of (1-10):100.

[0014] Preferably, in step (1), the particle size of the bamboo powder is 20-200 mesh, and the bamboo powder is selected from one or more of Phyllostachys pubescens, Phyllostachys edulis, Phyllostachys nigra, Phyllostachys bambusoides and Dendrocalamus giganteus.

[0015] Further preferably, the particle size of the bamboo powder is 40-60 mesh.

[0016] Preferably, in step (1), the alkaline solution is a 0.1-5 wt% sodium hydroxide solution.

[0017] By using a sodium hydroxide solution to weaken the hydrogen bonding between cellulose and lignin, the subsequent cavitation effect of ultrasonic can further disperse the fibers and avoid agglomeration.

[0018] Preferably, in step (1), the rotation speed of ball milling is 100-1000 rpm, and the ball milling time is 1-10 h.

[0019] By selecting the ball milling parameters within the above range, the bamboo powder fiber bundles can be fully broken, facilitating the subsequent formation of cellulose nanofibers.

[0020] Further preferably, the rotation speed of ball milling is 300-700 rpm, and the ball milling time is 3-8 h.

[0021] By using ball milling parameters within this range, cellulose nanofibers with a suitable diameter range can be formed.

[0022] Preferably, in step (1), the power of ultrasonic dispersion is 300-500 W, and the ultrasonic dispersion time is 10-30 min.

[0023] Ultrasonic dispersion within the above parameter range can effectively avoid agglomeration and ensure uniform dispersion of fibers; further, in cooperation with ball milling, efficient dissociation of bamboo powder is achieved.

[0024] Preferably, in step (2), the delignification reagent is 0.5-6 wt% sodium hypochlorite or 0.5-6 wt% acid.

[0025] The acid is selected from one or more of acetic acid, hydrochloric acid, and sulfuric acid.

[0026] Sodium hypochlorite preferentially oxidizes the aromatic ring structure of lignin, and acid (such as sulfuric acid) preferentially hydrolyzes the linkages between lignin, cellulose, and hemicellulose; further, by adjusting the reagent concentration, temperature, and time, the residual amount of lignin can be precisely controlled.

[0027] Preferably, in step (2), the heat treatment temperature is 70-90℃, and the heat treatment time is 60-120 min.

[0028] Preferably, in step (3), the drying temperature is -50℃, and the drying time is 48 h.

[0029] Preferably, 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.

[0030] Further preferably, in step (3), the zinc source is a 1-3 mol / L zinc sulfate solution.

[0031] Preferably, in step (3), the soaking activation time is 1-24 h.

[0032] Further preferably, in step (3), the soaking activation time is 2-12 h.

[0033] The present application provides a bamboo nanofiber separator prepared by the preparation method.

[0034] The separator prepared by the above method has a "micron-nanofiber interwoven network" structure: cellulose nanofibers (2-10 nm in diameter) and residual lignin particles (10 nm or less in particle size) are interlaced; the relative hydrophobicity of lignin can stabilize the three-dimensional pore structure and avoid the collapse of the pores in the electrolyte, and the surface polar groups (hydroxyl, carboxyl) thereof can accelerate the desolvation of hydrated zinc ions.

[0035] Preferably, 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.

[0036] The lignin residual amount, pore size, and thickness range can perfectly adapt to the Zn 2+ transporting demand in aqueous zinc ion batteries, avoiding the problem of large ion transport resistance (large impedance) caused by the non-uniform pore size of existing nanocellulose membranes.

[0037] Further preferably, the bamboo nanofiber separator has a lignin residual amount of 7-10%.

[0038] Preferably, the bamboo nanofiber separator has an electrolyte absorption rate of greater than or equal to 350%.

[0039] The present application provides an aqueous zinc ion battery, which comprises a positive electrode, an electrolyte, the above-mentioned bamboo nanofiber separator, and a negative electrode.

[0040] Preferably, the positive electrode is selected from one or more of transition metal oxides, Prussian blue compounds, metal sulfides, and organic-inorganic composite materials.

[0041] Preferably, the electrolyte is a 1-3 mol / L zinc sulfate solution. Further, the electrolyte is a 2 mol / L zinc sulfate solution.

[0042] Preferably, the negative electrode is selected from one or more of metallic zinc, zinc-plated metal materials, and zinc-plated carbon materials.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] (1) Using waste bamboo powder as raw material and non-toxic solvent in the process, bamboo powder is efficiently micronized through ball milling-ultrasonic synergy, and the lignin residual amount is precisely controlled to regulate the pore size, which can perfectly adapt to the transmission demand of Zn 2+ The mechanical properties of the diaphragm are significantly enhanced to resist zinc dendrite puncture, and the diaphragm has good stability, liquid retention capacity and ionic conductivity, and when applied to the aqueous zinc ion battery, excellent cycle capacity and service life are shown.

[0045] (2) The specific capacity retention rate of the assembled aqueous zinc ion battery is greater than or equal to 95% after 1000 cycles, the coulombic efficiency is greater than or equal to 99.5%, and the interface impedance is also significantly reduced.

[0046] (3) The cost of bamboo powder raw material is only 1 / 5 of that of glass fiber, and the process energy consumption is reduced by 30% compared with existing biomass diaphragm. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 It is an atomic microscope photo (AFM) of the bamboo nanofiber diaphragm of the embodiment 1 of the present application.

[0048] Figure 2 It is a scanning electron microscope photo (SEM) of the bamboo nanofiber diaphragm of the embodiment 1 of the present application.

[0049] Figure 3 It is a scanning electron microscope photo (SEM) of the commercial glass fiber diaphragm of the comparative example 1 of the present application.

[0050] Figure 4 It is a scanning electron microscope photo (SEM) of the diaphragm of the comparative example 2 of the present application.

[0051] Figure 5 It is a scanning electron microscope photo (SEM) of the diaphragm of the comparative example 3 of the present application.

[0052] Figure 6 It is a scanning electron microscope photo (SEM) of the diaphragm of the comparative example 4 of the present application.

[0053] Figure 7 It is a Raman test of the lignin distribution of the bamboo nanofiber diaphragm of the embodiment 1 of the present application.

[0054] Figure 8 It is a component analysis of the lignin content of the bamboo nanofiber diaphragm of the embodiment 1-5 of the present application.

[0055] Figure 9 It is the tensile strength and elongation at break of the embodiment 1 and the comparative example 1 of the present application.

[0056] Figure 10 It is the charge-discharge capacity ratio and coulombic efficiency of the embodiment 1 and the comparative example 1 of the present application. DETAILED DESCRIPTION

[0057] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined inventive purpose, the following embodiments and comparative examples are described in detail.

[0058] All raw materials were purchased on the market.

[0059] Example 1

[0060] (1) Bamboo powder pretreatment: 20 g of bamboo powder with a particle size of 60-120 mesh was mixed with 100 g of 1wt% sodium hydroxide solution, poured into a planetary ball mill tank, ball milled at 200 rpm for 8 h, and then ultrasonically dispersed for 20 min at 400 W to obtain a micro-nano bamboo powder mixture;

[0061] (2) Partial delignification: 4wt% sodium hypochlorite was added to the micro-nano bamboo powder mixture, and reacted at 70°C for 1 h in a water bath, then washed to neutral. At this time, the lignin content was 7.43%.

[0062] (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 freeze-dried at -50°C for 48 h. The film was cut into 18 mm discs, immersed in a 2 mol / L zinc sulfate solution for 12 h to obtain a bamboo nanofiber separator (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 separator was 400%.

[0063] (4) Battery assembly and testing: metal zinc as the negative electrode (purity ≥ 99%, diameter 15 mm, thickness 100 μm); vanadium pentoxide as the active material, the active material, SuperP, and sodium carboxymethyl cellulose were mixed in a mass ratio of 7:2:1, deionized water was used as the solvent, and the mixture was stirred to form a uniform slurry. The slurry was then uniformly coated on a 304 stainless steel current collector with a coating thickness of 100 μm. The coated current collector was dried at 60°C for 24 h and then cut into 15 mm diameter discs. The loading amount of the active material was 1.5-2.5 mg / cm 2 , 2 mol / L zinc sulfate as electrolyte, assemble CR2032 button cell; as an example of a full cell, use a non-conductive tweezer to assemble a CR2032 button cell in the order of negative electrode shell, spring, steel sheet, negative electrode sheet, electrolyte membrane, positive electrode sheet, and positive electrode shell. Then, the assembled battery was placed on a hydraulic sealer and pressed to a certain pressure for 5 s to seal the battery. The assembled battery was placed for more than 1 h before testing. The obtained button cell was tested for charge and discharge performance at room temperature using a new battery testing system (CT4008-5V50 mA). The voltage range was 0.2-1.6 V, and the current density was 0.5 A / g.

[0064] 200 mAh / g, maximum specific capacity 430 mAh / g, coulombic efficiency 99.7%, ionic conductivity 6.7 mS·cm -1 , zinc ion transference number 0.7.

[0065] Example 2

[0066] The preparation method of Example 2 is the same as Example 1, except that:

[0067] (2) Partial delignification: 0.5wt% sodium hypochlorite was added to the micro-nanoized bamboo powder mixture, and reacted at 70°C for 1 h, then washed to neutral. At this time, the lignin content was detected to be 22.0%;

[0068] (3) Film formation and activation: a bamboo nanofiber separator (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 separator was 360%;

[0069] (4) Battery assembly and testing: specific capacity of 101 mAh / g after 1000 cycles at a current density of 0.5 A / g, maximum specific capacity of 282 mAh / g, coulombic efficiency of 99.2%, ionic conductivity of 4.3 mS·cm -1 , zinc ion transference number 0.42.

[0070] Example 3

[0071] The preparation method of Example 3 is the same as Example 1, except that:

[0072] (2) Partial delignification: 1wt% sodium hypochlorite was added to the micro-nanoized bamboo powder mixture, and reacted at 70°C for 1 h, then washed to neutral. At this time, the lignin content was detected to be 13.12%;

[0073] (3) Film formation and activation: a bamboo nanofiber separator (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 separator was 370%;

[0074] (4) Battery assembly and testing: specific capacity of 100 mAh / g after 1000 cycles at a current density of 0.5 A / g, maximum specific capacity of 290 mAh / g, coulombic efficiency of 99.3%, ionic conductivity of 6.1 mS·cm -1 , zinc ion transference number 0.5.

[0075] Example 4

[0076] The preparation method of Example 4 is the same as Example 1, except that:

[0077] (2) Partial delignification: 2 wt% sodium hypochlorite was added to the micro-nano bamboo powder mixture solution, and reacted in a 70°C water bath for 1 h. After washing to neutral, the lignin content was detected to be 8.91%;

[0078] (3) Film formation and activation: a bamboo nanofiber separator (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 separator was 390%;

[0079] (4) Battery assembly and testing: the specific capacity was 120 mAh / g after 1000 cycles at a current density of 0.5 A / g, the maximum specific capacity was 310 mAh / g, the coulombic efficiency was 99.4%, the ionic conductivity was 6.3 mS·cm -1 , and the zinc ion transference number was 0.58.

[0080] Example 5

[0081] The preparation method of Example 5 is the same as Example 1, except that:

[0082] (2) Partial delignification: 6 wt% sodium hypochlorite was added to the micro-nano bamboo powder mixture solution, and reacted in a 70°C water bath for 1 h. After washing to neutral, the lignin content was detected to be 5.09%;

[0083] (3) Film formation and activation: a bamboo nanofiber separator (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 separator was 420%;

[0084] (4) Battery assembly and testing: the specific capacity was 150 mAh / g after 1000 cycles at a current density of 0.5 A / g, the maximum specific capacity was 350 mAh / g, the coulombic efficiency was 99.7%, the ionic conductivity was 9.2 mS·cm -1 , and the zinc ion transference number was 0.63.

[0085] Comparative Example 1

[0086] In Comparative Example 1, glass fibers (Whatman GF / D1823-090) were cut into discs with an inner diameter of 18 mm and then soaked 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 about 1 μm, the pore size was 2.7 μm, the thickness was 67.5 μm, the electrolyte absorption rate was 190%, and after assembling the battery, the specific capacity decreased to 100 mAh / g after 1000 cycles at a current density of 0.5 A / g.

[0087] Comparative Example 2

[0088] The preparation method of Comparative Example 2 is the same as that of Example 1, except that:

[0089] (2) Partial delignification: 10 wt% sodium hypochlorite was added to the micro-nanoized bamboo powder mixture, and reacted at 70°C for 6 h in a water bath, and then washed to neutral. At this time, the lignin content was close to 0%;

[0090] (3) Film formation and activation: a bamboo nanofiber separator 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 separator was 450%;

[0091] (4) Battery assembly and testing: the specific capacity was 95 mAh / g after 1000 cycles at a current density of 0.5 A / 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 , and the zinc ion transference number was 0.48.

[0092] Comparative Example 3

[0093] The preparation method of Comparative Example 3 is the same as that of Example 1, except that:

[0094] (2) Partial delignification: 7 wt% sodium hypochlorite was added to the micro-nanoized bamboo powder mixture, and reacted at 70°C for 1 h in a water bath, and then washed to neutral. At this time, the lignin content was 3%;

[0095] (3) Film formation and activation: a bamboo nanofiber separator 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 separator was 430%;

[0096] (4) Battery assembly and testing: the specific capacity was 100 mAh / g after 1000 cycles at a current density of 0.5 A / g, the maximum specific capacity was 220 mAh / g, the coulombic efficiency was 97.5%, and the ionic conductivity was 6.2 mS·cm -1 , and the zinc ion transference number was 0.52.

[0097] Comparative Example 4

[0098] The preparation method of Comparative Example 4 is the same as that of Example 1, except that:

[0099] (2) Partial delignification: 10 wt% sodium hypochlorite was added to the micro-nanoized bamboo powder mixture, and reacted at 70°C for 4 h in a water bath, and then washed to neutral. At this time, the lignin content was 25%;

[0100] (3) Film formation and activation: a bamboo nanofiber separator 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 separator was 340%;

[0101] (4) Battery assembly and testing: 110 mAh / g specific capacity after 1000 cycles at 0.5 A / g current density, maximum specific capacity 260 mAh / g, coulombic efficiency 99.0%, ionic conductivity 4.1 mS·cm -1 , and the zinc ion transference number is 0.42.

[0102] Detection Example 1

[0103] The surface micro-morphology of the examples and the comparative examples was characterized by using a scanning electron microscope, an atomic force microscope, a laser confocal Raman microscope, and a physical adsorption analyzer, and the results are shown in Figures 1-7 .

[0104] As shown in Figure 1 , it is an AFM (atomic force microscope 2x2 μm) photo of the surface of Example 1 of the present application. Figure 1 The "cellulose-lignin interwoven network" of the separator is shown, the fiber diameter is about 2-10 nm, and the lignin particles are uniformly distributed (particle size 10 nm), and there is no agglomeration in the channel.

[0105] Figure 2 The SEM photo of the surface of the bamboo nanofiber separator of Example 1 of the present application is shown in Figures 3-6 The SEM photos of the separators of Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are shown, respectively, wherein the SEM pictures are in the D90 statistical pore size distribution range, and it can be seen from the comparison that the bamboo nanofiber separator prepared by the present application has a "micron-nanofiber interwoven network" structure: the cellulose nanofiber (diameter 2-10 nm) and the residual lignin particles (particle size below 10 nm) are interlaced to form a controllable pore size of 10-100 nm; the relative hydrophobicity of lignin can stabilize the three-dimensional channel structure and avoid the collapse of the channel in the electrolyte, and at the same time, the surface polar groups (hydroxyl, carboxyl) of lignin can accelerate the desolvation of hydrated zinc ions.

[0106] Figure 7 The Raman test of lignin distribution of Example 1 of the present application is shown in Figure 7 The left graph in Figure 7 is a comparative line scan analysis diagram of lignin distribution signal, The right graph in

[0107] is a signal line scan diagram excited by 235 nm deep ultraviolet laser, and the results show that the imaging excitation wavelength 235 nm has strong resonance enhancement with the aromatic ring structure in lignin, which improves the contrast of lignin and makes surface sensitive imaging, and the cellulose signal is usually weak and easy to be submerged, which confirms that lignin is uniformly distributed in the separator and provides direct evidence for controllable pore size.

[0107] Detection Example 2

[0108] The thickness of different gel electrolyte films was tested by using an electronic micrometer (accuracy 0.001 mm), and the average value of three points on the sample was taken.

[0109] Test Example 3

[0110] As Figure 8 shown is the lignin content test of the separator of the present application Example 1-5, from Figure 8 It can be seen that after the treatment of different concentrations of sodium hypochlorite delignification, the lignin content shows a significant downward trend with the increase of sodium hypochlorite concentration. It shows that the lignin content is controllable, and the fiber pore size is controllable.

[0111] Test Example 4

[0112] Figure 9 The tensile strength and elongation at break of the present application Example 1 and Comparative Example 1 are shown by Figure 9 It can be seen that the tensile strength of Example 1 is about 90 MPa, which is 167 times that of the commercial glass fiber separator, and has super strong mechanical properties, confirming the enhancement effect of lignin on mechanical properties.

[0113] Figure 10 The charge-discharge capacity ratio and coulombic efficiency of the present application Example 1 and Comparative Example 1 are shown by

[0114] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any equivalent embodiments with equivalent changes are equivalent. Any modification, equivalent change and modification of the above embodiments according to the technical essence of the present application, which does not depart from the technical solution of the present application, still belongs to the scope of the technical solution of the present application.

Claims

1. A method for preparing a bamboo nanofiber separator, characterized by, The preparation method comprises the following steps: (1) mixing bamboo powder with an alkaline solution, and then performing ball milling and ultrasonic dispersion to form a micro-nano bamboo powder mixture; (2) adding a delignification agent to the micro-nano bamboo powder mixture, and then performing heat treatment to partially remove lignin, thereby obtaining a mixture; 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; the heat treatment is performed at a temperature of 70-90 ℃ for a time period of 60-120 min; (3) filtering and drying the mixture in step (2) to form a film, and then immersing the film in a zinc source for activation, thereby obtaining a bamboo nanofiber separator; 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.

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 is performed at a speed of 100-1000 rpm for a time period of 1-10 h. The ultrasonic dispersion is performed at a power of 300-500 W for a time period of 10-30 min.

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

5. The preparation method according to claim 1, characterized in that, In step (3), the immersion activation is performed for a time period of 1-24 h.

6. A bamboo nanofiber separator prepared by the preparation method of any one of claims 1-5.

7. 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 6, and a negative electrode.

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