Aqueous zinc ion battery electrode and preparation method and application thereof

Abstract

The invention discloses an aqueous zinc ion battery electrode. The aqueous zinc ion battery electrode comprises a substrate electrode and a halloysite nanotube coating coated on the surface of the zinc substrate electrode, the halloysite nanotube coating takes a halloysite nanotube as an active substance and takes cellulose as a water-based binder. The invention also discloses a preparation method of the aqueous zinc ion battery electrode and an aqueous zinc ion battery comprising the aqueous zinc ion battery electrode. The halloysite nanotube coating not only can effectively inhibit dendritic crystals generated during zinc ion electroplating stripping and effectively enhance the cycling stability of the negative electrode, but also can promote zinc ion desolvation and relieve agglomeration of active substances; in addition, electrolyte can be captured more easily by relying on the hydrophilicity of cellulose, so that the ion transmission rate is accelerated, and the cycling stability and the rate capability of the aqueous zinc ion battery are further improved.

Description

Technical Field

[0001] The present invention relates to the field of zinc ion batteries, and more specifically to an aqueous zinc ion battery electrode and a preparation method and application thereof. Background Art

[0002] As environmental awareness grows, the development of clean energy is attracting much attention. Due to the intermittent and discontinuous nature of clean energy such as solar energy and wind energy, the demand for mature large-scale energy storage equipment is imminent.

[0003] Currently, the widely used non-aqueous lithium-ion batteries use organic solvents as electrolytes, which can achieve a wider electrochemical stability window and higher energy density. Although lithium-ion batteries have high energy density, the environmental hazards and instability of organic electrolytes limit their large-scale application. Recently, zinc-ion batteries have become one of the most competitive green secondary batteries due to their inherent safety, high ionic conductivity, environmental friendliness, high theoretical capacity, and low reduction potential.

[0004] However, the industrialization of zinc-ion batteries still faces many obstacles. In aqueous zinc-ion batteries, zinc dendrites produced by the zinc negative electrode during the cycle process can easily pierce the diaphragm, causing battery short circuits. In addition, the reaction between the electrolyte and the zinc negative electrode metal may lead to hydrogen evolution and self-corrosion. The hydrogen produced by the hydrogen evolution reaction can also cause serious expansion of the battery. The above factors greatly shorten the cycle life of aqueous zinc-ion batteries and seriously reduce their coulombic efficiency. Therefore, the modification of zinc battery negative electrode materials is imminent.

[0005] To solve this problem, researchers have tried to improve the cycle performance of zinc batteries by adding electrolyte additives, improving the structure of nano zinc anodes, introducing artificial interface protective layers, and modifying new diaphragms. Since alloy metal coatings were used as artificial interface layers a few years ago, artificial interface layer materials have received great attention in the field of aqueous zinc ion battery modification due to their unique chemical, physical and mechanical properties.

[0006] At present, most of the related work on introducing artificial interface layers uses N-methylpyrrolidone solution of polyvinylidene fluoride as a binder. Although this type of organic binder can evenly and firmly adhere the active substance to the surface of the zinc electrode, N-methylpyrrolidone is extremely harmful to the environment. The processing of aqueous zinc-ion batteries and the recycling of waste batteries have seriously polluted the environment.

[0007] Silicate materials are abundant in reserves, low in price, and environmentally friendly, making them an excellent choice for artificial interface materials in aqueous zinc-ion batteries. However, as rigid materials, silicate materials cannot adapt to long-term battery cycles, resulting in cracks and irreversible consumption, which results in poor mechanical properties, thus affecting cycle stability and rate performance. Summary of the invention

[0008] The invention provides an aqueous zinc ion battery electrode and a preparation method thereof. The aqueous zinc ion battery electrode is environmentally friendly and can greatly improve the cycle stability and rate performance of the aqueous zinc ion battery.

[0009] The technical solution of the present invention is as follows:

[0010] An aqueous zinc ion battery electrode, comprising a base electrode and a halloysite nanotube coating coated on the surface of the zinc base electrode;

[0011] The halloysite nanotube coating uses halloysite nanotubes as active material and cellulose as water-based binder.

[0012] The coating in the aqueous zinc ion battery electrode of the present invention uses halloysite nanotube material as an active material, and the aqueous binder cellulose relies on hydrogen bonds to adhere the halloysite nanotubes to the surface of the zinc base electrode. The halloysite nanotubes can form hydrogen bonds with the aqueous binder cellulose to enhance the overall mechanical properties of the coating, and resist irreversible loss and deformation cracks of the coating through autonomous connection of hydrogen bonds during the long-term cycle of the zinc battery.

[0013] The halloysite nanotube coating can not only effectively inhibit the dendrites produced during zinc ion electroplating and stripping, effectively enhancing the cycle stability of the negative electrode, but also promote the dissolution of zinc ions and alleviate the agglomeration of active substances; in addition, relying on the hydrophilicity of cellulose, it can more easily capture electrolytes, thereby accelerating the ion transfer rate and further improving the cycle stability and rate performance of aqueous zinc ion batteries.

[0014] Preferably, in the halloysite nanotube coating, the molar ratio of halloysite nanotubes to cellulose is 1:(0.1-2).

[0015] In order to achieve better dispersion of halloysite nanotubes and control ionic conductivity, the proportion of cellulose needs to be strictly controlled. If the proportion of halloysite nanotubes is too high, it will affect the dispersibility of halloysite nanotubes in the coating solution, causing the halloysite nanotubes to agglomerate in the coating, affecting the uniformity of the coating, and causing uneven zinc ion deployment, which will lead to the formation of dendrites; if the proportion of cellulose is too high, the coating solution will be too dilute, and the bonding force with the zinc sheet will not be strong during the later coating process, causing the coating to fall off. In addition, a too dilute coating solution will affect the regulation of coating thickness, and the expected coating thickness will not be obtained during production.

[0016] More preferably, in the halloysite nanotube coating, the molar ratio of the halloysite nanotube to the cellulose is 1:(0.1-1.5).

[0017] The best effect is achieved when the molar ratio of halloysite nanotubes to cellulose is 1:(0.1-1.5).

[0018] More preferably, the inner diameter of the halloysite nanotubes is distributed in the range of 15 to 100 nm, the outer diameter is distributed in the range of 100 to 500 nm, and the length is 500 to 1000 nm.

[0019] Preferably, the halloysite nanotubes are acid activated; the acid activation process comprises: dispersing the halloysite nanotubes in water, adjusting the pH of the dispersion to be acidic with acid, stirring and ultrasonicating to completely disperse the halloysite nanotubes and activate the shell, and obtaining acid-activated halloysite nanotubes after separation and drying.

[0020] In an acidic environment, the outer surface of the halloysite nanotubes will stimulate negative charges, increasing the attraction to zinc ions, thereby accelerating the transmission of zinc ions; the inner surface of the halloysite nanotubes will be stimulated to be positively charged, attracting and storing anions such as sulfate, preventing them from contacting the zinc electrode, thereby inhibiting the occurrence of electrode side reactions from the source.

[0021] Preferably, the diameter of the cellulose is distributed in the range of 1 to 20 nm, and the length is distributed in the range of 1 to 50 μm.

[0022] In an aqueous solution environment, the cellulose will form hydrogen bonds with the halloysite nanotubes, and due to its zinc affinity, the active material halloysite nanotubes will be firmly attached to the base electrode, which can serve as a "bridge" to improve the overall mechanical properties of the halloysite nanotube coating.

[0023] Preferably, the cellulose is one or more of nanocellulose, cellulose acetate, bacterial cellulose and carboxymethyl cellulose.

[0024] Preferably, the thickness of the halloysite nanotube coating on the surface of the substrate electrode is 1 to 300 μm.

[0025] The binder used in the present invention is a water-based binder. If the coating thickness is too thin (<1 μm), the coating will be insufficiently stable in the electrolyte solution, and will fall off or crack during electroplating and zinc extraction, affecting the long-term cycle capacity of the battery. In addition, if the coating is too thin, the amount of halloysite nanotubes in the coating will be too small, the ability to inhibit side reactions will be relatively weak, and the battery will be over-polarized; if the coating thickness is too thick (>300 μm), the conductivity of the solution will be reduced, the capacity of the battery will be reduced, and the long-term cycle life of the battery will be affected.

[0026] The base electrode is a zinc electrode.

[0027] The present invention also provides a method for preparing the aqueous zinc ion battery electrode, comprising the following steps:

[0028] (1) dispersing halloysite nanotubes in water, adding dilute acid to make the dispersion acidic, stirring and ultrasonicating the halloysite nanotube particles to completely disperse and activate the shells to form a halloysite suspension; separating the halloysite nanotubes, washing and drying them to obtain activated halloysite nanotubes;

[0029] (2) mixing the activated halloysite nanotubes with the cellulose solution, ultrasonically dispersing and fully stirring to obtain a coating slurry;

[0030] (3) The coating slurry is coated on the surface of the base electrode, and after drying, an aqueous zinc ion battery electrode coated with a halloysite nanotube coating using cellulose as an aqueous binder is obtained.

[0031] Preferably, in step (1), the mass concentration of the halloysite nanotubes in the halloysite nanotube dispersion is 0.1-5%; and dilute acid is added dropwise to adjust the pH value of the dispersion to 2-7.

[0032] Preferably, in the cellulose solution of step (2), the mass concentration of cellulose is 0.1-5%.

[0033] When the cellulose concentration is too low, the adhesion between the slurry and the zinc sheet is poor during coating, resulting in local uneven coating; when the cellulose concentration is too high, the slurry has poor ductility and the coating thickness will be difficult to control.

[0034] Preferably, in step (3), the drying temperature is 10-150°C, the drying time is 1-720h, and the drying method is air drying, sun drying, air drying, oven drying or vacuum drying.

[0035] The present invention also provides an aqueous zinc ion battery, comprising the aqueous zinc ion battery electrode.

[0036] Compared with the prior art, the beneficial effects of the present invention include:

[0037] (1) The present invention selects halloysite nanotubes as active materials because: the tubular structure of halloysite nanotubes can reduce the barrier of ion transfer, thereby ensuring a small overpotential; in addition, the outer shell of the nanotubes is negatively charged, which accelerates the ion transfer rate and isolates the side reactions. The unique electrochemical properties of halloysite nanotubes and the abundant active sites on their surface make halloysite an ideal active material;

[0038] (2) Compared with the traditional halloysite coating, the present invention introduces cellulose as a binder, which can not only strengthen the connection between the halloysite nanotubes through hydrogen bonds and enhance the overall mechanical properties of the coating, but also effectively prevent the agglomeration of the halloysite nanotubes and homogenize the coating, thereby alleviating the short circuit problem caused by dendrite penetration;

[0039] (3) When the electrode of the present invention is used as the negative electrode of a zinc ion battery, the polar groups in the cellulose chain segments can enhance the ability to capture electrolytes, promote the desolvation of zinc ions, enable them to contact the surface of all active materials, accelerate the electroplating stripping rate, and its zinc affinity can strengthen the connection with the negative electrode, making the coating less likely to fall off;

[0040] (4) Batteries coated with halloysite nanotubes using a cellulose aqueous binder have a higher specific capacity. If PVDF or PTFE is used as a binder, the transport of zinc ions is hindered, thereby reducing the electroactive area, so the batteries with PVDF and PTFE anodes show poor cycling performance. In contrast, when a cellulose aqueous binder is used, it can absorb aqueous electrolytes and act as an electrolyte reservoir, accelerating the transport of zinc ions.

[0041] (5) Compared with the existing reported aqueous zinc-ion battery negative electrode coatings, the halloysite nanotube coating using cellulose as an aqueous binder proposed in the present invention has the advantages of low raw material cost, no need to use hazardous chemicals, simple operation steps, environmental friendliness, and controllable coating thickness, which plays a significant role in promoting the commercial application of aqueous zinc-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the X-ray diffraction pattern of the halloysite nanotube coating prepared in Example 1 using cellulose as an aqueous binder.

[0043] Figure 2 This is a Fourier transform infrared spectrum of the halloysite nanotube coating prepared in Example 1 using cellulose as an aqueous binder.

[0044] Figure 3 This is a scanning electron microscope image of the halloysite nanotube coating prepared in Example 1 using cellulose as an aqueous binder.

[0045] Figure 4 The symmetric cell assembled with the zinc anode coated with the halloysite nanotube coating with cellulose as aqueous binder prepared in Example 1 was -2 The current density and 1 mAh cm -2 Scanning electron microscope image of the negative electrode after cycling for 4000h at a deposition capacity of .

[0046] Figure 5 Symmetrical cells assembled from electrode discs prepared in Comparative Examples 1, 2, and 3 and Example 2 at 1 mA·cm -2 The current density and 1 mAh cm -2 Voltage-time diagram obtained at deposition capacity of .

[0047] Figure 6The symmetric cell assembled with the zinc anode coated with the halloysite nanotube coating using cellulose as an aqueous binder prepared in Example 1 was -2 The current density and 1 mAh cm -2 Voltage-time diagram obtained at deposition capacity of .

[0048] Figure 7 The cycling performance diagram of the full battery obtained by cycling the zinc negative electrode coated with the halloysite nanotube coating with cellulose as the aqueous binder prepared in Example 1 and the pure zinc foil obtained in Comparative Example 1 as the negative electrode material of the aqueous zinc ion battery and vanadium pentoxide as the positive electrode material at a current density of 5.0 A / g. DETAILED DESCRIPTION

[0049] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0050] Comparative Example 1

[0051] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0052] (2) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0053] Comparative Example 2 (without using water-based binder)

[0054] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0055] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0056] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0057] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0058] (5) mixing the activated halloysite material with a 5% mass concentration N-methylpyrrolidone solution of polyvinylidene fluoride, with the mass ratio of the composite material to the polyvinylidene fluoride being 9:1, and magnetically stirring for 12 hours to obtain a uniformly dispersed slurry;

[0059] (6) coating the slurry on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum drying at 70° C. for 12 h to obtain an in-situ polymerized polyaniline / halloysite nanotube zinc metal negative electrode;

[0060] (7) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0061] Comparative Example 3 (Unactivated Halloysite Nanotubes)

[0062] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0063] (2) mixing commercially available halloysite powder with an aqueous solution containing 1% mass concentration of nanocellulose, with a mass ratio of material to nanocellulose of 9:1, and magnetically stirring for 12 h to obtain a uniformly dispersed slurry;

[0064] (3) The slurry is coated on the surface of the zinc sheet treated in step (1), the coating layer thickness is 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0065] (4) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0066] Comparative Example 4 (Excessive Nanocellulose)

[0067] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0068] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0069] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0070] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0071] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of nanocellulose, with a mass ratio of the material to the nanocellulose of 1:5, and magnetically stirring for 12 h to obtain a uniformly dispersed slurry;

[0072] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0073] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0074] Comparative Example 5 (cellulose solution is too concentrated)

[0075] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0076] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0077] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0078] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0079] (6) mixing the activated halloysite material with an aqueous solution containing 10% by mass concentration of nanocellulose, with a mass ratio of the material to the nanocellulose of 9:1, and magnetically stirring for 12 h to obtain a uniformly dispersed slurry;

[0080] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0081] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0082] Example 1

[0083] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0084] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0085] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0086] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0087] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of nanocellulose, with a mass ratio of the material to the nanocellulose of 9:1, and magnetically stirring for 12 h to obtain a uniformly dispersed slurry;

[0088] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0089] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0090] Example 2

[0091] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0092] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0093] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0094] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0095] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of carboxymethyl cellulose, with the mass ratio of the material to the carboxymethyl cellulose being 9:1, and magnetically stirring for 12 hours to obtain a uniformly dispersed slurry;

[0096] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0097] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0098] Example 3

[0099] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0100] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0101] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0102] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0103] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of carboxymethyl cellulose, with the mass ratio of the material to the carboxymethyl cellulose being 9:1, and magnetically stirring for 12 hours to obtain a uniformly dispersed slurry;

[0104] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0105] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0106] Example 4

[0107] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0108] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0109] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0110] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0111] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of cellulose acetate, with the mass ratio of the material to the cellulose acetate being 9:1, and magnetically stirring for 12 hours to obtain a uniformly dispersed slurry;

[0112] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0113] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0114] Example 5

[0115] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0116] (2) 5 g of halloysite nanotubes with an inner diameter of 100 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0117] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0118] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0119] (6) mixing the activated halloysite material with an aqueous solution containing 1% mass concentration of bacterial cellulose, with a mass ratio of the material to the bacterial cellulose of 9:1, and magnetically stirring for 12 hours to obtain a uniformly dispersed slurry;

[0120] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 300 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0121] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0122] Example 6

[0123] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0124] (2) 5 g of halloysite nanotubes with an inner diameter of 20 nm, an outer diameter of 500 nm, and a length of 500 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0125] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0126] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0127] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of cellulose acetate, with the mass ratio of the material to the cellulose acetate being 9:1, and magnetically stirring for 12 hours to obtain a uniformly dispersed slurry;

[0128] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 10 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0129] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0130] Example 7

[0131] (1) A zinc sheet with a thickness of 0.05 mm was polished with SiC sandpaper with a particle size of 1000 mesh for 30 seconds, and then ultrasonically cleaned in anhydrous ethanol to remove impurities such as oil on the surface of the zinc sheet;

[0132] (2) 5 g of halloysite nanotubes with an inner diameter of 20 nm, an outer diameter of 500 nm, and a length of 1000 nm were added to 300 mL of deionized water and stirred for 24 h, followed by ultrasonication at a frequency of 75 kHz for 15 min at 25 ° C to completely disperse the halloysite nanotubes to obtain a milky white suspension;

[0133] (3) adding 5 mL of 10% dilute hydrochloric acid to the suspension obtained in step (2), adjusting the pH of the solution to 3, and stirring at 25° C. for 12 h to obtain an activated halloysite nanotube suspension;

[0134] (4) centrifuging the suspension obtained in step (3) at 8000 rpm, washing it alternately with deionized water and anhydrous ethanol three times, and vacuum drying it at 70° C. for 12 h to obtain an activated halloysite material;

[0135] (6) mixing the activated halloysite material with an aqueous solution containing 1% by mass concentration of nanocellulose, with the mass ratio of the material to the nanocellulose being 1:2, and magnetically stirring for 12 h to obtain a uniformly dispersed slurry;

[0136] (7) The slurry is coated on the surface of the zinc sheet treated in step (1) to a coating thickness of 150 μm, and vacuum dried at 70° C. for 12 h to obtain a zinc metal negative electrode having a halloysite nanotube coating with cellulose as an aqueous binder.

[0137] (8) Cut the above zinc metal negative electrode material into electrode discs with a diameter of 1.2 cm.

[0138] Performance Testing

[0139] The electrode discs obtained in Examples 1 to 7 and Comparative Examples 1 to 5 were used as positive and negative electrodes, glass fibers were used as separators, and 2.0 mol·L -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 of 25°C for 12 hours 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 .

[0140] Table 1

[0141] Polarization voltage(V) Cycle time (h) Comparative Example 1 0.4 200 Comparative Example 2 0.38 600 Comparative Example 3 0.35 1200 Comparative Example 4 0.34 300 Comparative Example 5 0.4 100 Example 1 0.12 4300 Example 2 0.15 2400 Example 3 0.16 2200 Example 4 0.2 1300 Example 5 0.16 2000 Example 6 0.19 1500 Example 7 0.18 1600

[0142] As can be seen from Table 1, compared with the halloysite coating using an organic binder in Comparative Example 2, the addition of cellulose plays a stronger protective role, has a longer cycle life and a smaller polarization voltage. The unactivated halloysite nanotubes in Comparative Example 3 and the changes in cellulose concentration and feed ratio in Comparative Examples 4 and 5 will affect the uniformity of the entire coating, thereby significantly affecting the cycle performance of the electrode material.

[0143] The final product materials obtained in Examples 1 to 7 and Comparative Examples 1 to 5 were punched into 1.2 cm diameter discs as electrodes for aqueous zinc ion batteries. -1 The electrolyte with zinc sulfate as the solute and deionized water as the solvent was assembled into a symmetrical battery. The assembled zinc ion half-cell was left to stand for 12 hours in a constant temperature environment of 25°C.

[0144] Figure 1 This is an X-ray diffraction pattern of the halloysite nanotube coating using cellulose as an aqueous binder prepared in Example 1. As can be seen from the figure, the XRD peaks of the aqueous binder coating with excellent mechanical properties all correspond to the halloysite nanotubes, indicating that the addition of cellulose has no effect on the structure of the halloysite nanotubes.

[0145] Figure 2 This is the Fourier transform infrared spectrum of the halloysite nanotube coating prepared in Example 1 using cellulose as an aqueous binder. It can be seen that at 3400 cm-1 A new peak appeared nearby, 1600cm -1 The characteristic peaks of nearby nanocellulose hydroxyl groups shifted, proving that hydrogen bonds were formed between the halloysite nanotubes and them.

[0146] Figure 3 This is a scanning electron microscope image of the halloysite nanotube coating prepared in Example 1 using cellulose as an aqueous binder. Figure 3 It can be seen that the water-based binder coating with excellent mechanical properties has an obvious tubular structure and is evenly distributed on the zinc sheet interface.

[0147] Figure 4 The symmetric cell assembled with the zinc anode coated with the halloysite nanotube coating with cellulose as aqueous binder prepared in Example 1 was -2 The current density and 1 mAh cm -2 Scanning electron microscope image of the negative electrode after cycling for 4000h at a deposition capacity of . Figure 4 It can be seen that due to the improvement of the stability and reversibility of the zinc negative electrode, the zinc negative electrode after cycling of the present invention exhibits a smooth and compact surface without the generation of zinc dendrites and by-products.

[0148] Figure 5 Symmetrical cells assembled from electrode discs prepared in Comparative Examples 1, 2, and 3 and Example 2 at 1 mA·cm -2 The current density and 1 mAh cm -2 The voltage-time graph obtained at the deposition capacity of . It can be seen from the figure that the symmetrical battery assembled with pure zinc foil in comparative example 1 has a cycle life of less than 300 hours under the action of dendrites and corrosion; the halloysite coating of pure halloysite nanotubes is gradually consumed after 200 hours of cycling, and the final cycle life is less than 600 hours; the ability of unactivated halloysite nanotubes to inhibit side reactions is weakened, and eventually the cycle stops due to excessive polarization.

[0149] Figure 6 The symmetric cell of the halloysite nanotube coating prepared in Example 1 with cellulose as aqueous binder was tested at 1 mA·cm -2 The current density and 1 mAh cm -2 The voltage-time diagram obtained under the deposition capacity of Figure 7 It can be seen that due to Zn 2+ Due to the improvement of the transport kinetics, the cycle stability of the zinc negative electrode of the present invention is greatly improved, and it can operate stably for 4000 hours. The overpotential of zinc deposition / stripping is reduced, showing a smaller electrode polarization phenomenon.

[0150] Figure 7The figure is the cycle performance diagram of the full battery of Example 1. The zinc / halloysite nanotube / cellulose prepared in this example is used as the negative electrode material of the aqueous zinc ion battery, and vanadium pentoxide is used as the positive electrode material. The discharge capacity is still as high as 292.6 mAh / g after 1500 cycles at a high current density of 5.0 A / g, and there is almost no attenuation compared with the initial capacity, showing excellent cycle stability. In addition, the capacity of the zinc sheet is only 62.5 mAh / g after 1500 cycles under the same test conditions, indicating that the halloysite nanotube coating prepared in Example 1 with cellulose as an aqueous binder has a significant improvement in the performance of the full battery.

[0151] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An aqueous zinc ion battery electrode, It is characterized in that It includes a base electrode and a halloysite nanotube coating coated on the surface of the zinc base electrode; The halloysite nanotube coating uses halloysite nanotubes as active material and cellulose as water-based binder.

2. The aqueous zinc ion battery electrode according to claim 1, It is characterized in that In the halloysite nanotube coating, the molar ratio of the halloysite nanotube to the cellulose is 1:(0.1-2).

3. The aqueous zinc ion battery electrode according to claim 1, It is characterized in that The inner diameter of the halloysite nanotubes is distributed between 15 and 100 nm, the outer diameter is distributed between 100 and 500 nm, and the length is 500 to 1000 nm.

4. The aqueous zinc ion battery electrode according to any one of claims 1 to 3, It is characterized in that The halloysite nanotubes are acid activated; The acid activation process includes: dispersing the halloysite nanotubes in water, adjusting the pH of the dispersion to be acidic with acid, stirring and ultrasonicating to completely disperse the halloysite nanotubes and activate the shell, and obtaining the acid-activated halloysite nanotubes after separation and drying.

5. The aqueous zinc ion battery electrode according to claim 1, It is characterized in that The diameter of the cellulose is distributed in the range of 1 to 20 nm, and the length is distributed in the range of 1 to 50 μm.

6. The aqueous zinc ion battery electrode according to claim 1 or 5, It is characterized in that The cellulose is one or more of nanocellulose, cellulose acetate, bacterial cellulose and carboxymethyl cellulose.

7. The aqueous zinc ion battery electrode according to claim 1, It is characterized in that The thickness of the halloysite nanotube coating on the surface of the substrate electrode is 1 to 300 μm.

8. A method for preparing an aqueous zinc ion battery electrode as claimed in any one of claims 1 to 7, It is characterized in that The following steps are involved: (1) dispersing halloysite nanotubes in water, adding dilute acid to make the dispersion acidic, stirring and ultrasonicating the halloysite nanotube particles to completely disperse and activate the shells to form a halloysite suspension; separating the halloysite nanotubes, washing and drying them to obtain activated halloysite nanotubes; (2) mixing the activated halloysite nanotubes with the cellulose solution, ultrasonically dispersing and fully stirring to obtain a coating slurry; (3) The coating slurry is coated on the surface of the base electrode, and after drying, an aqueous zinc ion battery electrode coated with a halloysite nanotube coating using cellulose as an aqueous binder is obtained.

9. The preparation method according to claim 8, It is characterized in that In the cellulose solution of step (2), the mass concentration of cellulose is 0.1-5%.

10. An aqueous zinc ion battery, It is characterized in that It comprises an aqueous zinc ion battery electrode as described in any one of claims 1 to 7.

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