Multi-layer sandwich structure zinc negative electrode, preparation method and aqueous zinc ion battery

Abstract

The method comprises the following steps: carrying out oil removal treatment on a metal net, tinning the metal net, then taking the metal net as a current collector, placing a zinc sheet on each of the upper side and the lower side of the current collector to integrally form a sandwich structure, and carrying out mechanical pressing to obtain a three-layer sandwich structure; and performing surface chemical treatment on the obtained three-layer sandwich structure, and performing metal doping modification to obtain the zinc negative electrode with the multi-layer sandwich structure. According to the zinc negative electrode structure, the uniform distribution of large-area electrode current can be remarkably improved; the uniformity of deposition and stripping of zinc ions on a large-area zinc electrode is improved; the cycling stability of the zinc negative electrode is improved under the conditions of long-time charging / discharging and large surface capacity; the growth of zinc dendrites and the occurrence of side reactions can be effectively slowed down.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc batteries, and relates to a multi-layer sandwich structure zinc anode and its preparation method, as well as an aqueous zinc-ion battery. Background Technology

[0002] Aqueous zinc-ion batteries have attracted widespread attention in recent years due to their advantages such as high safety, non-flammability and non-explosion, low material and manufacturing costs, and environmental friendliness, especially in the fields of small-powered two-wheeled vehicles, three-wheeled vehicles, and future large-scale energy storage. However, the maturity of the current technology and the performance of existing battery products are still far from commercialization. One of the main reasons is that during repeated charge and discharge processes, the negative electrode experiences problems such as zinc dendrite growth, severe hydrogen evolution side reactions, and surface corrosion, which greatly affect the cycle stability and electrochemical capacity utilization of zinc-ion batteries.

[0003] To overcome these technical challenges, researchers conducted extensive and in-depth studies and adopted various strategies, such as: a) modifying the surface structure of the zinc anode or artificially constructing a solid electrolyte interphase (SEl) membrane. For example, organic materials such as metal-organic frameworks (MOFs) and polymers, as well as inorganic materials such as carbon materials, metal oxides, and metal sulfides, are used to artificially construct SEl films (iScience 28, 111751, February 21, 2025); b) adding various functional additives such as ionic additives, organic additives, and other types of additives to the electrolyte (Energy Storage Materials, 2021, 34: 545-562) to regulate the zinc ion solvation structure and inhibit the hydrogen evolution side reaction of water molecules on the negative electrode surface; c) using high-concentration electrolytes (Nat. Mater., 2018, 17: 543-549; Energy Environ. Sci. 2021, 14: 4463) to reduce the water molecule concentration and reduce the hydrogen evolution side reaction; or d) using a three-dimensional porous zinc negative electrode (Energy Materials and Devices, 2024, 2(3): 9370040) and other technologies to improve the stability of the negative electrode interface and the uniformity of zinc deposition stripping, and extend the cycle stability of the battery.

[0004] However, in practical zinc-ion full cell applications, especially for zinc anodes in single cells with larger capacity (Ah level and above), there are still many challenges: 1) For larger zinc sheet electrodes (single-sided area)

[0005] ≥70cm 21) Due to the uneven current distribution on the zinc sheet, uneven zinc deposition and peeling occur during repeated charge and discharge cycles, leading to holes or gaps in the electrode. Deposits accumulate at favorable nucleation sites, forming protrusions and eventually dendrites, further exacerbating the uneven electric field distribution on the electrode surface. This uneven electric field distribution and disordered dendrite growth reduce the overall battery charge / discharge efficiency and cycle life. 2) With increasing battery cycling, especially in weakly acidic environments with pH < 4, the hydrogen evolution reaction (HER) side reaction at the zinc electrode remains severe. The HER side reaction not only consumes water molecules from the electrolyte but also causes a local pH increase, leading to the formation of insoluble zinc salts, reducing charge / discharge efficiency, increasing the impedance at the battery electrode interface, and causing battery swelling, thus reducing the battery's electrochemical performance and cycle life.

[0006] In existing solutions, regardless of whether an artificial organic coating, an inorganic coating, or an in-situ SEI film is formed on the zinc anode surface, the structural stability of the zinc electrode coating or SEI film (especially over large areas) is insufficient with increasing cycle count, resulting in poor mechanical properties. Under anode volume fluctuations, it is prone to fracture / breakage and detachment, leading to uneven zinc deposition / stripping on the anode surface and deterioration of battery performance. Furthermore, the organic frameworks used in organic coatings are often environmentally unfriendly and costly. Therefore, in the field of zinc anode construction based on zinc sheets, the design of existing zinc anode structures and the construction of surface solid interface films need improvement. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a multilayer sandwich structure zinc anode, its preparation method, and an aqueous zinc-ion battery. By employing a specific method to form a multilayer composite zinc anode, the uniformity of its large-area electrode current field distribution and the uniformity of zinc ion deposition and stripping are greatly improved, significantly enhancing the cycle stability of the zinc anode.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides a method for preparing a multilayer sandwich structure zinc anode, comprising the following steps:

[0010] The metal mesh has a copper surface and is degreased.

[0011] The obtained metal mesh is tin-plated to serve as a current collector. Then, a zinc sheet is placed on each of the upper and lower sides of the current collector to form a sandwich structure. The structure is then mechanically pressed to obtain a three-layer sandwich structure.

[0012] After surface chemical treatment, the obtained three-layer sandwich structure is modified with metal doping. The metal is a high hydrogen evolution overpotential metal. Considering the influence of the acidic environment of the electrolyte on the stability of the electrode, and combining industrialization cost and safety, the high hydrogen evolution overpotential metal is preferably one or more of lead or bismuth; thus, the multilayer sandwich structure zinc anode is obtained.

[0013] In the above technical solution, the metal mesh is further described as either a copper mesh or a non-copper metal mesh. When a non-copper metal mesh is used, it is usually a stainless steel mesh. Titanium mesh is expensive and not conducive to industrial application. Nickel mesh, iron mesh, and aluminum mesh are unstable in weakly acidic media and are prone to chemical reactions, so they are generally not used. In this invention, the non-copper metal mesh is a stainless steel mesh. However, the potential difference between stainless steel mesh and zinc itself will accelerate the hydrogen evolution reaction, and stainless steel mesh has poor zinc affinity. Therefore, pre-plating with copper is required. The pre-plating with copper is carried out by electroplating, physical deposition, or chemical deposition, and the copper should completely cover the surface of the metal mesh.

[0014] Furthermore, the tin plating process employs methods such as electroplating, electroless plating, physical sputtering, or vapor deposition to completely cover the surface of the metal mesh. Electroplating or electroless plating, which facilitates more uniform coverage, is preferred. Tin plating effectively ensures the bonding between the zinc sheet and the metal mesh after planar pressing, as well as the performance of the current collector, thereby guaranteeing the successful fabrication and long-term stability of the high-performance multilayer sandwich zinc anode. If the metal mesh is not tin-plated and directly pressed with the zinc sheet, a multilayer integrated structure cannot be formed. This necessitates significantly increasing the pressure and temperature during planar pressing, but high temperatures can cause copper oxidation on the metal mesh surface, affecting the conductivity of the current collector.

[0015] Furthermore, the mechanical pressing employs planar mechanical pressing with a pressure of 130-250 kg / cm². 2 The pressing temperature is 80-150℃, preferably 100-130℃, and the pressing time is 5-60 minutes. In this invention, a three-layer sandwich structure integrating the current collector and zinc sheet can be obtained through simple planar pressing. This structure serves as the main structure of the high-performance zinc anode. This method plays a crucial role in the preparation of large-area zinc anodes. If a rolling pressing method is used, the zinc thickness needs to be reduced through continuous rolling, increasing tension. Therefore, other methods must be combined to control the flatness of the large-area electrode.

[0016] Furthermore, the surface chemical treatment involves degreasing the three-layer sandwich structure, followed by acid washing, rinsing with deionized water until neutral, and then drying.

[0017] Furthermore, the surface chemical treatment includes: immersing the three-layer sandwich structure in a mixed aqueous solution of sodium phosphate and sodium carbonate, soaking and cleaning to remove surface oil stains, rinsing with deionized water until neutral, then acid washing with 1.0-2.0 mol / L dilute hydrochloric acid for 10-120 seconds, or acid washing with 2-10% dilute sulfuric acid for 10-60 seconds, or acid washing with 60-85% phosphoric acid for 60-300 seconds, rinsing with deionized water until neutral, and drying. In this process, acid washing of the resulting structure surface can remove the surface oxide film, which is beneficial to improving the electrochemical performance of the zinc anode and its charge-discharge cycle stability.

[0018] Furthermore, the metal doping modification is achieved by sputtering, electron beam evaporation or immersion, preferably by immersion.

[0019] Furthermore, when the metal is lead, the metal doping modification specifically involves immersing the surface-chemically treated three-layer sandwich structure in a 1.0-10 mmol / L basic lead acetate solution at 20-60°C for 2-30 seconds; when the metal is bismuth, before metal doping modification, the surface-chemically treated three-layer sandwich structure must first be immersed in a 0.5-3% ammonium fluoride solution for 30-60 seconds for surface activation treatment, and then immersed in a bismuth-doped metal solution for metal doping modification; the components of the bismuth-doped metal solution are: 15-25 g / L citric acid, 5-10 g / L potassium sodium tartrate, 5-10 g / L bismuth nitrate pentahydrate, 0.1-0.5 g / L sodium dodecyl sulfate, and 100-150 mg / L vanillin, adjusting the solution pH to 2.0-2.5, and immersing at 40-60°C for 2-30 seconds.

[0020] The present invention also provides a multi-layer sandwich structure zinc anode, comprising a metal mesh having a copper surface, both sides of the metal mesh being coated with a tin layer, and a zinc sheet being disposed outside the tin layer, forming a multi-layer sandwich structure and being mechanically pressed together, wherein the zinc sheet is doped with a metal with a high hydrogen evolution overpotential.

[0021] The present invention also provides an aqueous zinc-ion battery, which contains a zinc negative electrode prepared by the method described in any of the preceding claims or uses a zinc negative electrode as described above.

[0022] The beneficial effects of the present invention are at least as follows:

[0023] 1) This invention proposes a novel, industrially feasible solution for zinc anode fabrication based on zinc sheets. It utilizes a tin-coated metal mesh as the anode current collector and forms a sandwich structure with zinc sheets through mechanical planar pressing. Combined with metal doping, this yields a multilayer composite zinc anode with excellent performance. The tin plating layer overcomes the challenge of direct bonding between copper mesh and Zn sheets. Furthermore, the manufacturing process is simple, requiring neither artificial organic nor inorganic coatings. The technical route is simple, low-cost, and environmentally friendly, facilitating industrial production.

[0024] 2) This technical solution is particularly suitable for large-area negative electrodes (achieving a single-sided area ≥70cm²). 2 The method for manufacturing this zinc-ion battery involves designing a composite metal mesh with a tin-containing layer that exhibits excellent conductivity and structural stability as the negative electrode current collector. This mesh, along with a zinc sheet, is formed into a three-layer sandwich structure through simple mechanical planar pressing. By surface chemically treating the three-layer sandwich structure and doping it with trace amounts of other metals possessing high hydrogen evolution overpotential, the uniform distribution of current in large-area electrodes is significantly improved, enhancing the uniformity of zinc ion deposition and stripping on large-area zinc electrodes. In particular, it effectively improves the charge-discharge cycle stability of the zinc negative electrode under long-term charge / discharge and large areal capacity conditions, and effectively mitigates zinc dendrite growth and side reactions. The aqueous zinc-ion battery assembled with a manganese dioxide positive electrode exhibits high discharge specific capacity and charge-discharge efficiency. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the multilayer sandwich zinc anode structure in this invention;

[0026] Figure 2 The curve shows the polarization potential of the zinc anode as a function of cycling during 1380 hours of charge-discharge cycles.

[0027] Figure 3a The curve showing the polarization potential of the zinc anode as a function of cycling during a 1450-hour charge-discharge cycle in a 3Ah battery.

[0028] Figure 3b The surface morphology of the zinc anode after charge-discharge cycles of a 3Ah battery;

[0029] Figure 3c The discharge capacity of a 3Ah battery consisting of a zinc negative electrode and a manganese dioxide positive electrode varies with the number of cycles.

[0030] Figure 4a1 The surface morphology of the negative electrode before acid washing and doping with metallic bismuth;

[0031] Figure 4a2 The surface morphology of the negative electrode after doping with metallic bismuth;

[0032] Figure 4bThe results of EDAX elemental analysis of the negative electrode after bismuth doping;

[0033] Figure 4c The curve of polarization potential as a function of cycling for a bismuth-zinc doped anode during a 4Ah battery charge-discharge cycle.

[0034] Figure 4d The discharge capacity of the 4Ah battery composed of a multilayer sandwich structure zinc negative electrode and a manganese dioxide positive electrode of the present invention is shown as a function of cycling.

[0035] Figure 5a1 The SEM morphology of the zinc anode surface before lead doping after acid washing with dilute hydrochloric acid.

[0036] Figure 5a2 SEM morphology of zinc anode surface doped with metallic lead for 5 seconds;

[0037] Figure 5a3 SEM morphology of zinc anode surface after 10 seconds of lead doping;

[0038] Figure 5b Linear sweep polarization curve (LSV) of hydrogen evolution reaction at zinc anode;

[0039] Figure 5c The curve of polarization potential versus cycling in a 4Ah battery after zinc anode is doped with lead;

[0040] Figure 6 For zinc anode at 2mA / cm 2 Curve showing the change of zinc negative electrode polarization potential with cycling at current density;

[0041] Figure 7a The curve of polarization potential of zinc anode as a function of cycle during battery charge-discharge cycle;

[0042] Figure 7b The surface morphology of the zinc anode after charge-discharge cycles of a 1.8Ah battery;

[0043] Figure 7c The discharge capacity of a 1.8Ah battery consisting of a zinc sheet negative electrode without a metal mesh current collector and a MnO2 positive electrode is shown as a function of cycling.

[0044] Figure 8a This is to achieve the effect of planar pressing of stretched copper mesh and zinc sheet at 120℃;

[0045] Figure 8b This is the effect of using tin-plated copper mesh and zinc sheet to press flat at 120℃;

[0046] Figure 9 This demonstrates the effect of planar pressing of stretched copper mesh and zinc sheet at 180°C. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0048] This invention utilizes specific methods and structural design to fabricate a multilayer sandwich zinc anode with excellent electrochemical performance. A composite metal mesh with excellent conductivity and stability is used as the anode current collector. This mesh, along with zinc foil, is mechanically planar-pressed to form a three-layer sandwich structure. The middle layer is a tin-coated metal current collector, with zinc foil on both sides. This sandwich zinc electrode is then subjected to surface chemical treatment and doping with trace amounts of other metals with high hydrogen evolution overpotentials, ultimately forming a multilayer composite zinc anode, as shown in the schematic diagram below. Figure 1 As shown, this multilayer composite structure can significantly improve the uniform distribution of current in large-area electrodes; enhance the uniformity of zinc ion deposition and stripping on large-area zinc electrodes; improve the cycle stability of zinc anodes under longer charge / discharge times and larger areal capacities; and effectively slow down the growth of zinc dendrites and the occurrence of side reactions.

[0049] According to some embodiments of the present invention, the preparation method of the multilayer sandwich structure zinc anode of the present invention generally includes the following steps:

[0050] Step 1, Commercially available stretched copper mesh or 304 stainless steel mesh is selected as the metal mesh collecting body. The thickness of the copper mesh is typically 0.1-0.3 mm, preferably 0.15-0.2 mm, and the mesh size is typically (2-3) × (1-2) mm. The stainless steel mesh is woven mesh with a mesh count of 50-100.

[0051] The metal mesh current collector is cut to size as needed. It is first degreased. The preferred degreasing solution consists of a mixture of NaOH (30-50 g / L), Na3PO4 (20-30 g / L), and a surfactant (sodium dodecyl sulfate, 1-5 g / L), with the remainder being water. The degreasing temperature is 60-80°C. After ultrasonic cleaning for 10-20 minutes, it is rinsed with deionized water until neutral and then dried for later use. In the examples below, the degreasing solution used is an aqueous solution of NaOH 35 g / L, Na3PO4 20 g / L, and sodium dodecyl sulfate 3 g / L, at 80°C, with ultrasonic cleaning for 10 minutes.

[0052] Step 2 If 304 stainless steel mesh is used, it must be pre-plated with copper before tin plating. If copper mesh is used, it can be directly tin-plated after degreasing, cleaning, and drying. Copper plating and subsequent tin plating can be performed using deposition methods such as electroplating, physical deposition, or chemical plating, but care must be taken to ensure complete coverage of the mesh surface. Chemical plating is preferred.

[0053] The pre-plating copper treatment solution typically consists of the following components: copper sulfate pentahydrate (10-15 g / L), disodium EDTA (30-40 g / L), 37% formaldehyde (10-15 ml / L), potassium ferrocyanide (0.05 g / L), and polyethylene glycol with a molecular weight of 6000 (0.1 g / L), with the remainder being water. The pH of the plating solution is adjusted to 12-13 with sodium hydroxide, the plating temperature is 40°C, and the time is 30 minutes. In the following specific embodiments of the present invention, the specific formulation of the pre-plating copper treatment solution is as follows: the solution contains 15 g / L copper sulfate pentahydrate, 35 g / L disodium EDTA, 15 ml / L 37% formaldehyde, 0.05 g / L potassium ferrocyanide, and 0.1 g / L polyethylene glycol with a molecular weight of 6000, with a pH of 12.

[0054] The preferred composition of the tin plating solution is typically: 25-30 g stannous chloride per liter, 20-25 g citric acid per liter, 45-48 ml 37% concentrated hydrochloric acid per liter, 90-100 g thiourea per liter, 70-80 g sodium hypophosphite per liter, with the remainder being water. The pH of the plating solution is adjusted to approximately 2 with hydrochloric acid, the temperature is 60°C, and the chemical plating time is 1-10 minutes. After tin plating, the metal mesh is rinsed with deionized water until neutral and then dried for later use. In the following specific embodiments of the invention, the specific formulation of the tin plating solution is: 30 g stannous chloride per liter, 20 g citric acid per liter, 48 ml 37% concentrated hydrochloric acid per liter, 100 g thiourea per liter, 70 g sodium hypophosphite per liter, with the remainder being water, pH 2, and a plating time of 5 minutes.

[0055] Step 3 Take pure zinc sheets (purity ≥99.8%) with a thickness of 20-200 micrometers, preferably 50-80 micrometers. The width of the cut zinc sheets should be slightly wider than the tin-plated copper or stainless steel mesh obtained in step 2 by 1-2 millimeters. However, the length of the zinc sheets should be 10 millimeters shorter than the metal current collector mesh. Place zinc sheets on both the top and bottom sides of the metal current collector mesh to form a sandwich structure, and then transfer it to a hydraulic press for planar pressing. The pressing parameters are a pressure of 130-250 kg / cm². 2 Preferred density: 180-220 kg / cm² 2 The temperature is 80-150℃, preferably 100-130℃; the pressing time is 5-60 minutes, preferably 10-30 minutes.

[0056] Step 4The zinc anode with a three-layer sandwich structure obtained in step 3 is subjected to surface chemical treatment. 25 g / L of sodium phosphate and 15 g / L of sodium carbonate are weighed and mixed evenly. The mixture is then immersed and cleaned at 60°C to remove oil stains from the zinc anode surface. Afterward, it is rinsed with deionized water until neutral. Next, it is acid-washed with 1.0-2.0 mol / L dilute hydrochloric acid for 10-120 seconds, or with 2-10% dilute sulfuric acid for 10-60 seconds, or with 60-85% phosphoric acid for 60-300 seconds. Finally, it is rinsed with deionized water until neutral and dried for later use.

[0057] Step 5 The zinc anode surface obtained in step 4 is then modified with metal doping. Metal doping can be achieved by sputtering, electron beam evaporation, or immersion, with immersion being the preferred method. For the preparation of large-area zinc anodes, immersion is more advantageous in controlling the doping amount and ensuring doping uniformity.

[0058] (1) The lead-doped metal solution is a 1.0-10 mmol / L basic lead acetate aqueous solution, the temperature is 20-60℃, preferably 25-40℃, and the soaking time is 2-30 seconds.

[0059] (2) The bismuth-doped metal solution typically consists of the following components: 15-25 g / L citric acid, 5-10 g / L sodium potassium tartrate, 5-10 g / L bismuth nitrate pentahydrate, 0.1-0.5 g / L sodium dodecyl sulfate, and 100-150 mg / L vanillin. The pH of the solution is adjusted to 2.0-2.5 with 65% nitric acid and ammonia. The reaction temperature is 40-60°C, and the reaction time is 2-30 seconds. Before doping with bismuth, after surface chemical treatment (degreasing and pickling) as described in step 4, the zinc electrode needs to be immersed in a 0.5-3% ammonium fluoride solution for surface activation treatment for 30-60 seconds. In the following specific embodiments of the present invention, the specific formulation of the bismuth-doped metal solution is: 15 g / L citric acid, 10 g / L sodium potassium tartrate, 10 g / L bismuth nitrate pentahydrate, 0.5 g / L sodium dodecyl sulfate, 100 mg / L vanillin, pH 2, and temperature 50°C.

[0060] Battery assembly and performance testing: Battery performance was measured using the constant current charge-discharge (GCD) method. The symmetrical battery consists of two multilayer sandwich zinc electrodes and a separator; the separator is a composite membrane made of grafted polypropylene membrane and non-woven fabric. The zinc-manganese full cell consists of a manganese dioxide positive electrode, a multilayer sandwich zinc negative electrode, and a separator. The manganese dioxide positive electrode is prepared by a roll forming method, with an electrode thickness of 0.4-0.45 mm and a manganese dioxide loading of 40-45 mg / cm². 2 The dimensions are 115×65 mm. The negative electrode is a multilayer sandwich zinc electrode; the electrolyte is a mixed electrolyte consisting of 1.0M ZnSO4 and 0.5M MnSO4 and additives, with a pH value of 4.0-4.5.

[0061] Example 1

[0062] A stretched copper mesh with a thickness of 0.15 mm and a mesh size of 2.5 × 1.5 mm was selected as the negative current collector, with a length × width of 28 × 38 mm. After ultrasonic degreasing and rinsing with deionized water until neutral and then drying, it was tin-plated to obtain a tin-plated copper mesh for later use.

[0063] A Zn foil with a thickness of 0.08 mm and a size of 30 × 40 mm was used as the negative electrode active material. A 0.08 mm thick Zn foil was placed on both the top and bottom sides of a tin-plated copper mesh, and then transferred to a hydraulic press for planar pressing. The pressing parameters were a pressure of 220 kg / cm². 2 The temperature was 120℃, and the holding time was 10 minutes. After pressing, the negative electrode consists of a three-layer sandwich structure.

[0064] The pressed three-layer sandwich structure Zn electrode, after surface degreasing, serves as the negative electrode, while the positive electrode is a manganese dioxide electrode. It is prepared by wet rolling pressing with a manganese dioxide loading of 45 mg / cm³. 2 The diaphragm is a composite membrane made of grafted polypropylene membrane and nonwoven fabric. The electrolyte is a solution of 1.0M ZnSO4, 0.5M MnSO4 and additives.

[0065] The polarization potential of the zinc anode as a function of cycle time during battery charge-discharge cycles is shown in the following curve. Figure 2 As shown, after 1380 hours of charge-discharge cycles, the negative electrode polarization potential was not only low, but the zinc deposition / stripping potential remained stable. This indicates that the addition of a current collector to the negative electrode structure increases the uniformity of the electrode current distribution, compared to Comparative Example 1 (e.g., ...). Figure 7a Compared with using a single Zn sheet as the zinc anode, this significantly extends the charge-discharge cycle stability of the zinc anode.

[0066] Example 2

[0067] Compared to Example 1, this example enlarges the geometry of the zinc negative electrode, increasing the battery capacity to 4Ah. A Zn foil with a thickness of 0.08 mm and dimensions of 120 × 63 mm was used. The negative electrode current collector was a tin-plated copper mesh with dimensions of 130 × 61 mm. Its length was 10 mm longer than the zinc foil, serving as the electrode lug, and its width was slightly narrower than the zinc foil to avoid exposing the current collector after electrode forming. The electrode pressing parameters were a pressure of 200 kg / cm². 2 The temperature was 110℃, and the holding time was 10 minutes. A three-layer sandwich structure zinc negative electrode was fabricated; the positive electrode was a manganese dioxide electrode, with dimensions of 115×65 mm (length × width), formed by wet rolling, with a manganese dioxide loading of 45 mg / cm². 2 The diaphragm is a composite membrane made of grafted polypropylene membrane and non-woven fabric. The electrolyte is a solution of 1.0M ZnSO4, 0.5M MnSO4 and additives.

[0068] Figure 3a The curves showing the polarization potential of the zinc anode as a function of charge-discharge cycles during a 3Ah battery test are presented. The test results show that the charge-discharge potential of the anode is stable, and the zinc deposition / stripping polarization potential is low. After 1450 hours of charge-discharge cycles, the polarization potential remains basically stable, and the surface morphology of the anode is as follows: Figure 3b As shown, compared with Comparative Example 1 ( Figure 7b In comparison, the multi-layer sandwich zinc anode in this example did not show obvious fractures or perforations, while the zinc sheet in Comparative Example 1 showed obvious fractures and perforations. The discharge capacity of the 3Ah battery composed of the zinc anode and manganese dioxide cathode in this example as a function of cycle number is shown in the figure below. Figure 3c As shown, its cyclic stability is also significantly improved (compared to Comparative Example 1). Figure 7c )Compare).

[0069] Example 3

[0070] Based on the three-layer sandwich zinc anode obtained in Example 2, the zinc anode was further subjected to surface degreasing, cleaning, and acid washing with 5% sulfuric acid for 60 seconds to remove the surface oxide film, according to step 4 of the present invention. It was then rinsed with deionized water until neutral and dried. Finally, the surface of the above zinc anode was doped with metallic bismuth according to the formulation and conditions of step 5.

[0071] Figure 4a1 The surface morphology of the negative electrode before acid washing and doping with metallic bismuth; Figure 4a2 The surface morphology of the negative electrode after acid washing for 60 seconds, activation with 1% ammonium fluoride solution for 60 seconds, and doping with metallic bismuth for 5 seconds is as follows: After doping with bismuth, many small white dots appear on the electrode surface. Figure 4b The results of EDAX elemental analysis show that the average bismuth content is 4.9%. In addition to bismuth, the negative electrode surface also contains zinc and a small amount of aluminum, with the trace aluminum originating from the zinc substrate.

[0072] Figure 4c The polarization potential of the bismuth-doped zinc anode changes during a 4Ah battery charge-discharge cycle. Test results show that the charge / discharge polarization potential of the zinc anode ranges from -70 mV to +50 mV. After 1500 hours of charge-discharge cycles, the polarization potential remains stable, and no large-area fractures or perforations occur on the electrode. This demonstrates that bismuth doping further improves the cycle stability of the zinc anode. In this example, the current collector for the zinc anode is a tin-plated copper mesh, and the zinc sheet size is 120 × 63 mm. The manufacturing process is the same as in Example 2, and the zinc anode has a multi-layer sandwich structure. The positive electrode uses commercially available electrolytic manganese dioxide as the active material, with dimensions of 115 × 65 mm and a loading of 45 mg / cm². 2It is produced by wet rolling, and the diaphragm is a composite membrane made of grafted polypropylene membrane and non-woven fabric. The electrolyte is a solution of 1.0M ZnSO4 and 0.5M MnSO4 and additives. Figure 4d The discharge capacity curve of the 4Ah battery composed of a multilayer sandwich structure zinc negative electrode and manganese dioxide positive electrode of the present invention is shown to be a cycle curve, which shows that the battery discharge capacity has a good retention rate and the charge-discharge coulombic efficiency is also good.

[0073] Example 4

[0074] Based on the three-layer sandwich zinc anode prepared in Example 2, the zinc anode was further degreased and cleaned according to the formula and conditions in step 4 of this invention. Then, it was acid-washed with 2M dilute hydrochloric acid to remove the surface oxide film, followed by rinsing with deionized water until neutral and then drying. Next, the surface of the above zinc anode was doped with metallic lead according to the formula and conditions in step 5. The lead doping solution was 5 mmol / L basic lead acetate, and the temperature was 25°C. Four zinc anodes were immersed for 2, 5, 10, and 20 seconds respectively. The morphology of the zinc anode surface before and after lead doping is shown below. Figures 5a1-5a3 As shown. Figure 5a1 The morphology of the negative electrode surface after acid washing with dilute hydrochloric acid before lead doping; Figure 5a2 The surface morphology of the negative electrode after 5 seconds of lead doping; Figure 5a3 The image shows the surface morphology of the negative electrode after 10 seconds of lead doping. After 10 seconds, in addition to small particle morphology, the negative electrode surface is also covered with a thin layer of lead material, showing a significant difference in surface morphology compared to the electrode doped for 5 seconds. EDAX elemental analysis revealed that the average atomic percentage of lead on the electrode surface after 5 and 10 seconds of doping was 1.4% and 1.8%, respectively.

[0075] To investigate the hydrogen evolution reaction behavior of the zinc anode after lead doping, linear sweep (LSV) polarization curves of the hydrogen evolution reaction were measured on the zinc anode doped with metallic lead. The scan rate was 2 mV / s. The test results are as follows: Figure 5b As shown. From Figure 5b As can be seen, the initial hydrogen evolution potentials measured for the pure zinc anode (i.e., the three-layer sandwich zinc anode obtained in Example 2) and the zinc anode after removing surface zinc oxide with dilute hydrochloric acid (without lead doping) were between -1.68V and -1.70V. The initial hydrogen evolution potentials of the zinc anode after lead doping modification for 2-20 seconds were between -1.78V and -1.81V. Compared with the undoped zinc anode, the lead-doped zinc anode significantly increased the hydrogen evolution overpotential and effectively suppressed the occurrence of hydrogen evolution side reactions. The effect of suppressing hydrogen evolution side reactions was best after lead doping the zinc anode surface for 2-5 seconds.

[0076] Figure 5cThe graph shows the polarization potential of the zinc anode after 2 seconds of lead doping during a 4Ah battery charge-discharge cycle, increasing with cycle time. The test results show that although the charge / discharge polarization potential of the zinc anode is slightly higher than in Example 2, it remains below 100 mV. More importantly, its cycle stability is greatly improved; after 1880 hours of charge-discharge cycles, the polarization potential remains stable, and no large-area fracture or perforation occurs on the electrode. In this example, the current collector and electrode dimensions of the zinc anode are the same as in Example 2, and the zinc anode has a multi-layer sandwich structure. The positive electrode is a manganese dioxide electrode with dimensions of 115 × 65 mm and a loading of 45 mg / cm². 2 It is produced by wet rolling, and the diaphragm is a composite membrane made of grafted polypropylene membrane and non-woven fabric. The electrolyte is a solution of 1.0M ZnSO4 and 0.5M MnSO4 and additives.

[0077] Example 5

[0078] A 50-mesh 304 stainless steel woven mesh was selected as the negative electrode current collector, with a length × width of 130 × 61 mm. After ultrasonic degreasing and rinsing with deionized water until neutral and then drying, it underwent pre-plating with copper and tin, followed by rinsing with deionized water until neutral and then drying for later use. A 0.08 mm thick Zn foil with dimensions of 120 × 63 mm was used as the negative electrode active material. A 0.08 mm thick Zn foil was placed on both the top and bottom sides of the tin-plated stainless steel mesh, and then transferred to a hydraulic press for planar pressing at a pressure of 180 kg / cm². 2 The temperature was 110℃, and the holding time was 15 minutes. After pressing, the negative electrode consisted of a three-layer sandwich structure. Two pressed Zn negative electrodes were wiped with alcohol and used as the positive and negative electrodes of the soft-pack symmetrical battery. The separator between the positive and negative electrodes was a composite membrane made of grafted polypropylene film and non-woven fabric. The electrolyte was a solution of 1.0M ZnSO4 and 0.5M MnSO4 mixed with additives. Figure 6 For zinc anode at 2mA / cm 2 The curve of zinc anode polarization potential versus cycling at current density. Each cycle consists of 5 hours of charging and 5 hours of discharging (equivalent to an areal capacity of 10 mAh / cm²). 2 The results showed that the zinc anode had a large overpotential in the first 100 cycles, which decreased with increasing cycle count. Although the polarization overpotential fluctuated during cycling, it remained relatively stable compared to Comparative Example 1. Figure 7a Compared to (zinc anodes without metal mesh current collectors), this study extended the charge-discharge cycle stability of the zinc anode and reduced its polarization potential.

[0079] Comparative Example 1

[0080] A current collector without a metal mesh was constructed using Zn foil as the negative electrode. The Zn foil thickness was 0.2 mm (the length and width of the Zn foil in this comparative example are the same as those in Example 2). Manganese dioxide was used as the active material for the positive electrode, which was prepared by a roll forming method. The electrode thickness was 0.44 mm, and the manganese dioxide loading was 40 mg / cm². 2 The separator is a composite membrane made of grafted polypropylene membrane and non-woven fabric. The electrolyte is a mixed electrolyte consisting of 1.0M ZnSO4, 0.5M MnSO4, and additives, with a pH of 4.4. The battery consists of three positive and three negative electrodes placed alternately by the separator. The polarization potential of the zinc negative electrode during the battery charge-discharge cycle is shown in the curve. Figure 7a As shown, after 600 hours of charge-discharge cycles, the negative electrode zinc foil showed cracks and perforations. The surface morphology of the negative electrode after cycling is as follows. Figure 7b As shown, the electrode current distribution is uneven, and the negative electrode polarization potential also increases significantly. Due to the significant increase in the negative electrode polarization potential, the battery's discharge capacity also decreases rapidly. Figure 7c As shown.

[0081] Comparative Example 2

[0082] A stretched copper mesh with a thickness of 0.15 mm and a length × width of 130 × 61 mm, and a mesh size of 2.5 × 1.5 mm, and a tin-plated copper mesh were selected as negative electrode current collectors, respectively. After ultrasonic degreasing and rinsing with deionized water until neutral, they were dried and ready for use.

[0083] A Zn foil with a thickness of 0.08 mm and a size of 120 × 63 mm was used as the negative electrode active material. A Zn foil was placed on the top and bottom surfaces of both the stretched copper mesh and the tin-plated copper mesh, and then transferred to a hydraulic press for planar pressing. The pressing parameters were a pressure of 240 kg / cm². 2 The temperature was 120℃, and the holding time was 30 minutes. The results were as follows: Figure 8a , 8b As shown, pure stretched copper mesh, as a current collector, is difficult to integrate with zinc sheets into a three-layer sandwich structure. Figure 8a ), while tin-plated copper mesh and zinc sheets can form a three-layer sandwich structure with good bonding strength ( Figure 8b It can be seen that after the copper mesh is chemically tin-plated, the affinity between the copper mesh surface and the zinc sheet is effectively improved, and under certain pressure and temperature of planar pressing, they have a stronger bonding force.

[0084] Comparative Example 3

[0085] A stretched copper mesh with a thickness of 0.15 mm, a length × width of 130 × 61 mm, and a mesh size of 2.5 × 1.5 mm was selected as the negative current collector. After ultrasonic degreasing and rinsing with deionized water until neutral, it was dried for use.

[0086] A Zn foil with a thickness of 0.08 mm and a size of 120 × 63 mm was used as the negative electrode active material. One Zn foil was placed on each of the top and bottom surfaces of the stretched copper mesh, and then transferred to a hydraulic press for planar pressing. The pressing parameters were a pressure of 240 kg / cm². 2 The temperature was 180℃, and the holding time was 30 minutes. Although the pure copper mesh, acting as the current collector, forms a three-layer sandwich structure with the zinc sheet, the copper mesh oxidizes at higher temperatures, turning light black, as shown in the following figure. Figure 9 As shown, this will greatly affect the conductivity of the current collector.

[0087] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing a multilayer sandwich structure zinc anode, characterized in that, Includes the following steps: The metal mesh has a copper surface and is degreased. The obtained metal mesh is tin-plated to serve as a current collector. Then, a zinc sheet is placed on each of the upper and lower sides of the current collector to form a sandwich structure. The structure is then mechanically pressed to obtain an integrated three-layer sandwich structure. After surface chemical treatment, the obtained three-layer sandwich structure is modified with metal doping, wherein the metal is a high hydrogen evolution overpotential metal, to obtain the multilayer sandwich zinc anode.

2. The method for preparing a multilayer sandwich structure zinc anode according to claim 1, characterized in that, The metal mesh can be a copper mesh or a non-copper metal mesh. If a non-copper metal mesh is used, a pre-copper plating process is required. The pre-copper plating process uses electroplating, physical deposition, or chemical deposition methods to plate copper, which should completely cover the surface of the metal mesh.

3. The method for preparing a multilayer sandwich structure zinc anode according to claim 1, characterized in that, The tin plating process is carried out by electroplating, physical deposition, or chemical deposition, and the tin plating should completely cover the surface of the metal mesh.

4. The method for preparing a multilayer sandwich structure zinc anode according to claim 1, characterized in that, The mechanical pressing pressure is 130-250 kg / cm², the pressing temperature is 80-150℃, and the pressing time is 5-60 minutes.

5. The method for preparing a multilayer sandwich structure zinc anode according to claim 1, characterized in that, The surface chemical treatment involves degreasing the three-layer sandwich structure, followed by acid washing, rinsing with deionized water until neutral, and then drying.

6. The method for preparing a multilayer sandwich structure zinc anode according to claim 5, characterized in that, The surface chemical treatment includes: immersing the three-layer sandwich structure in a mixed aqueous solution of sodium phosphate and sodium carbonate, soaking and cleaning to remove surface oil stains, rinsing with deionized water until neutral, then acid washing with 1.0-2.0 mol / L dilute hydrochloric acid for 10-120 seconds, or acid washing with 2-10% dilute sulfuric acid for 10-60 seconds, or acid washing with 60-85% phosphoric acid for 60-300 seconds to remove the surface oxide film, rinsing with deionized water until neutral, and drying.

7. The method for preparing a multilayer sandwich structure zinc anode according to claim 1, characterized in that, The metal doping modification is achieved by sputtering, electron beam evaporation, or immersion methods.

8. The method for preparing a multilayer sandwich structure zinc anode according to claim 1, characterized in that, When the metal is lead, the metal doping modification specifically involves immersing the surface-chemically treated three-layer sandwich structure in a 1.0-10 mmol / L basic lead acetate solution at 20-60°C for 2-30 seconds. When the metal is bismuth, before metal doping modification, the three-layer sandwich structure after surface chemical treatment needs to be immersed in a 0.5-3% ammonium fluoride solution for 30-60 seconds for surface activation treatment, and then immersed in a bismuth-doped metal solution for metal doping modification. The composition of the bismuth-doped metal solution is: 15-25 g / L citric acid, 5-10 g / L potassium sodium tartrate, 5-10 g / L bismuth nitrate pentahydrate, 0.1-0.5 g / L sodium dodecyl sulfate, 100-150 mg / L vanillin. The pH of the solution is adjusted to 2.0-2.5, and the solution is immersed at 40-60℃ for 2-30 seconds.

9. A multi-layer sandwich zinc anode, characterized in that, The device includes a metal mesh with a copper surface, both sides of which are covered with a tin layer, and a zinc sheet is provided outside the tin layer. The whole device forms a multi-layer sandwich structure and is bonded together by mechanical pressing. The zinc sheet is doped with a metal with a high hydrogen evolution overpotential.

10. An aqueous zinc-ion battery, characterized in that, The battery contains a zinc negative electrode prepared by any one of claims 1-8 or uses a zinc negative electrode as described in claim 9.

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