Composite Zinc Foil with ZnSiO3 Protective Layer, Its Preparation and Application

Abstract

The present invention relates to a composite zinc foil with a ZnSiO3 protective layer, its preparation and application. The composite material can be directly used as the negative electrode of an aqueous zinc-ion battery. The ZnSiO3 protective layer is composed of a ZnSiO3 nanosheet array, having a structure with coexistence of amorphous and crystalline states. The thickness of the ZnSiO3 protective layer is about 300 nm, the thickness of a single ZnSiO3 nanosheet is about 15 nm, and abundant pores are distributed in the ZnSiO3 nanosheets. The process of the present invention is simple, can achieve large-scale production, has strong operability and meets the requirements of green chemistry. When the composite zinc foil with a ZnSiO3 protective layer is used as the negative electrode of an aqueous zinc-ion battery, the protective layer can reduce the overpotential of zinc nucleation and growth, realize the uniform distribution of zinc ions at the interface between the zinc negative electrode and the electrolyte, thereby inducing uniform deposition of zinc and improving the cycle stability of zinc deposition-dissolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy materials, and particularly relates to a composite zinc foil with a ZnSiO3 protective layer and its preparation. Based on a one-step hydrothermal method, it can be used as the negative electrode of an aqueous zinc-ion battery and applied to electrochemical energy storage. Background Art

[0002] Aqueous batteries have the advantages of low cost, high safety, environmental friendliness, etc., and have great application prospects in future large-scale energy storage devices. Among various current metal aqueous batteries, there are lithium, sodium, potassium, magnesium, calcium ion batteries, etc. Due to having a suitable standard reduction potential (Zn 2+ / Zn, -0.76V vs. standard hydrogen electrode), zinc metal can be directly used as the negative electrode of an aqueous zinc-ion battery. The zinc negative electrode has a high theoretical specific capacity of 820 mAh g -1 , but it currently faces three key problems: 1) The uneven nucleation of zinc during the electrodeposition process induces the growth of zinc dendrites, which pierce the separator and will cause battery short circuit and failure; 2) The electrochemical corrosion problem on the surface of zinc metal leads to irreversible loss and reduces the zinc deposition-dissolution efficiency; 3) There is a hydrogen evolution reaction in a commonly used weakly acidic electrolyte (such as 2 mol L -1 zinc sulfate solution, pH is about 4.1), which will cause the battery to bulge and expand, damaging the battery system. The above problems occur at the interface between zinc metal and the electrolyte, so interface optimization is of great significance for extending the working life of aqueous zinc-ion batteries.

[0003] Constructing a protective layer on the zinc foil surface is an important part of interface optimization. A suitable protective layer needs to have excellent zinc ion conductivity, stability in the electrolyte, and close contact with the zinc foil. Recently, various materials such as zinc-containing compounds, montmorillonite, titanium dioxide, etc. can be made into zinc foil protective layers through methods such as coating, atomic layer deposition, and vacuum high-temperature heat treatment. However, these methods face limitations in actual production: The coating method requires the use of additional binders, and the coating thickness is often up to dozens of micrometers, which will significantly increase the mass of the zinc foil, resulting in a decrease in energy density. The atomic layer deposition method can prepare ultrathin coatings with nanoscale and controllable thickness, but its cost is relatively expensive and it cannot be prepared in large quantities. In fact, most materials can only be compounded with the zinc foil by the coating process, and zinc-containing compounds can be in-situ grown on the zinc foil surface through the reaction of raw materials with the zinc foil in principle, and their connection with the zinc foil is also closer. Therefore, using a low-cost and scalable synthesis method to in-situ prepare a uniform and thin zinc-containing compound protective layer on the zinc foil surface is an important breakthrough direction. Summary of the Invention

[0004] The present invention provides a composite zinc foil with a ZnSiO3 protective layer and a preparation method thereof for the above-mentioned existing technical problems. The preparation method has simple process, can be scaled up and conforms to green chemistry. When the obtained ZnSiO3 nanosheet array composite zinc foil (abbreviation: Zn@ZSO) is used as the negative electrode of an aqueous zinc-ion battery, the cycle life of the battery can be significantly improved.

[0005] The technical solution adopted by the present invention for the above technical problems is: a composite zinc foil with a ZnSiO3 protective layer, wherein the ZnSiO3 protective layer is composed of a ZnSiO3 nanosheet array and has a structure with coexistence of amorphous state and crystalline state; the thickness of the ZnSiO3 protective layer is ~300 nm, the thickness of a single ZnSiO3 nanosheet is ~15 nm, and rich pores are distributed in the ZnSiO3 nanosheets.

[0006] The preparation method of the composite zinc foil with a ZnSiO3 protective layer includes the following steps:

[0007] 1) Weigh a certain amount of SiO2 and add it to deionized water, then drop a certain amount of NaOH aqueous solution and stir evenly to obtain a solution;

[0008] 2) Transfer the solution obtained in step 1) into a reaction vessel, put in the zinc foil, take it out after hydrothermal reaction, cool it to room temperature, then take out the zinc foil, wash it with deionized water and dry it.

[0009] According to the above scheme, the size of SiO2 in step 1) is 10 - 50 nm, the mass is 0.12 - 0.4 g, the amount of deionized water used is 30 - 40 mL, the amount of NaOH aqueous solution used is 50 - 100 μL, and its concentration is 2 mol / L. -1 。

[0010] According to the above scheme, the hydrothermal reaction temperature in step 2) is 120 - 140 °C, the time is 12 - 36 h, and the thickness of the zinc foil is 10 - 200 μm.

[0011] Application of the composite zinc foil with a ZnSiO3 protective layer as the negative electrode of an aqueous zinc-ion battery.

[0012] In-situ growth of ZnSiO3 nanosheet arrays on the surface of zinc foil by a one-step hydrothermal method. In the initial stage of the hydrothermal process, due to the alkaline reaction solution, a small amount of zinc on the surface of the zinc foil first dissolves, and the zinc ion concentration in the solution increases with the extension of the reaction time. During the continuous hydrothermal process, when the zinc ion concentration reaches a certain level, it reacts with HSiO3 formed by the dissolution of SiO2 nanoparticles - and OH in the solution -Combined, it grows in situ on the surface of the zinc foil, and finally a nanosheet array perpendicular to the surface of the zinc foil is obtained. The thickness of the array is ~300 nm, and it has the characteristics of full coverage, uniformity, density, electron insulation, hydrophilicity, and porosity. In addition, the synthesis method has simple steps, and large-scale preparation can be achieved by controlling the raw material addition amount, the reactor volume, and the zinc foil area.

[0013] The beneficial effects of the present invention are as follows: By constructing a vertical array of ZnSiO3 nanosheets on the surface of the zinc foil, the present invention promotes the charge transfer and mass transfer processes, provides abundant zinc ion adsorption sites and diffusion channels, reduces the overpotential of zinc nucleation and growth, realizes the uniform distribution of zinc ions at the interface between the zinc negative electrode and the electrolyte, and thus induces flat zinc deposition. Using this composite zinc foil as the electrode and assembling a symmetric battery, when the areal capacity is 1 mAh cm -2 −2, the deposition-dissolution process of zinc can be cycled 800 times at a current density of 1 mA cm -2 −2, with a duration of up to 1600 h; at 5 mA cm -2 −2, it can be cycled 3800 times, with a duration of up to 1520 h. Using this composite zinc foil as the negative electrode and potassium ion pre-embedded layered MnO2 (abbreviation: KMO) as the positive electrode, a 2032-type coin cell is assembled. After cycling 400 times at a current density of 308 mA g -1 −1, it has a discharge specific capacity of 156.8 mA g -1 −1, and the capacity retention rate compared to the first cycle is 98.4%, showing the potential for commercial application. Description of the Drawings

[0014] Figure 1 is the optical photograph of Zn@ZSO prepared in Example 1 of the present invention;

[0015] Figure 2 is the scanning electron microscope image of Zn@ZSO in Example 1 of the present invention;

[0016] Figure 3 is the transmission electron microscope image of the ZSO layer in Example 1 of the present invention;

[0017] Figure 4 is the high-angle annular dark-field scanning transmission electron microscope image and energy spectrum analysis element distribution map of the cross-section of Zn@ZSO in Example 1 of the present invention;

[0018] Figure 5 is the selected area electron diffraction pattern of the ZSO layer in Example 1 of the present invention;

[0019] Figure 6 is the high-resolution transmission electron microscope image of the ZSO layer in Example 1 of the present invention;

[0020] Figure 7For the Zn@ZSO surface in Example 1 of the present invention, the contact angle results for a 2 mol L -1 ZnSO4 solution;

[0021] Figure 8 For the rate performance of the Zn@ZSO||Zn@ZSO symmetric battery in Example 1 of the present invention;

[0022] Figure 9 For the long-term cycling performance of the Zn@ZSO||Zn@ZSO symmetric battery in Example 1 of the present invention at 1 and 5 mA cm -2 current density and 1 mAh cm -2 areal capacity;

[0023] Figure 10 For the cycling performance of the Zn@ZSO||KMO coin cell in Example 1 of the present invention at 308 mA g -1 ;

[0024] Detailed Embodiment Modes

[0025] To better understand the present invention, the content of the present invention will be described below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments.

[0026] Example 1

[0027] A preparation method for a composite zinc foil with a ZnSiO3 protective layer includes:

[0028] 1) Weigh 0.24 g of SiO2 (particle size 15 nm), disperse it in 35 mL of deionized water by stirring, and add 50 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.6;

[0029] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, and place a 100 μm thick zinc foil with a size of 2.5 cm × 4.5 cm. After hydrothermal reaction in an oven at 120 °C for 36 h, take out the reaction kettle, naturally cool it, then take out the zinc foil, wash it with deionized water and dry it;

[0030] Taking Zn@ZSO in this example as an example, the optical photograph of the obtained composite zinc foil is as shown in the appendix Figure 1 ; Figure 2 The morphology of this protective layer is as shown in the appendix Figure 2 ; it is very flat and evenly distributed within a large range (appendix Figure 2 a). The thickness of the nanosheets is about 15 nm and they are arranged closely (appendix Figure 3As shown in the transmission electron microscope image, the nanosheets are composed of ultra-small particles of ~15 nm connected together, and there are many pores between the particles. In the high-angle annular dark field scanning transmission electron microscope image (attached Figure 4 , the Pt layer was deposited before the electron microscope imaging, which plays a protective role for the ZSO layer), the thickness of the protective layer on the zinc foil surface is relatively uniform, about 300 nm. In addition, the elemental distribution map can prove the presence and uniform distribution of the three elements Zn, Si, and O. The selected area electron diffraction pattern further proves that it is ZnSiO3 (JCPDS No. 70-0852) (attached Figure 5 ), and the amorphous region and the crystalline region coexist (attached Figure 6 ). In addition, the contact angle of the 2 mol L -1 ZnSO4 electrolyte droplet on the Zn@ZSO surface is 66.8°, which is significantly smaller than that of the pure zinc foil (attached Figure 7 ).

[0031] Using the Zn@ZSO prepared in this example as the electrode, a glass fiber GF / D as the separator, and a 2 mol L -1 ZnSO4 solution as the electrolyte, an aqueous zinc-ion symmetric battery was assembled. Attached Figure 8 is the evaluation of the rate performance. When the areal capacity is 1 mAh cm -2 , the deposition overpotentials of Zn@ZSO||Zn@ZSO at 0.5, 1, 2, and 5 mA cm -2 are 14, 16, 21, and 34 mV, respectively. The overpotential is small in a relatively wide current density range, indicating that the ZSO layer has fast zinc-ion transport kinetics. Attached Figure 9 is the evaluation of the deposition-dissolution cycle stability of zinc. When the areal capacity is 1 mAh cm -2 , the Zn@ZSO||Zn@ZSO symmetric battery can cycle 800 times at 1 mA cm -2 , with a duration of up to 1600 h (attached Figure 9 a), and it can cycle 3800 times at 5 mA cm -2 , with a duration of up to 1520 h (attached Figure 9 b). This excellent cycle stability is attributed to the inhibition of zinc dendrite growth by the ZnSiO3 protective layer. To verify the practical application potential of Zn@ZSO, a potassium-ion pre-embedded layered MnO2 was used as the cathode material, and a 2 mol L - 1 ZnSO4 + 0.1 mol L -1 MnSO4 solution was used as the electrolyte to assemble a 2032-type button cell. To meet the industrial conditions, the areal loading of the cathode is ~8 mg cm -2 . At 308 mA g -1At a current density of, the discharge specific capacity of the Zn@ZSO||KMO battery after 400 cycles is 156.8 mA g -1 , and the capacity retention rate compared to the first cycle is 98.4% (attached Figure 10 ), proving its excellent long-cycle performance.

[0032] Example 2

[0033] A method for preparing a composite zinc foil with a ZnSiO3 protective layer includes:

[0034] 1) Weigh 0.2 g of SiO2 (particle size of 15 nm), disperse it in 35 mL of deionized water by stirring, and add 50 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.6;

[0035] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, and place a 100 μm thick zinc foil with a size of 2.5 cm × 4.5 cm. After hydrothermal reaction in an oven at 120 °C for 36 h, take out the reaction kettle, naturally cool it, take out the zinc foil, wash it with deionized water and dry it;

[0036] Taking the Zn@ZSO obtained in this example as an example, when used as the negative electrode of an aqueous zinc-ion battery, its electrochemical performance is similar to that of Example 1.

[0037] Example 3

[0038] A method for preparing a composite zinc foil with a ZnSiO3 protective layer includes:

[0039] 1) Weigh 0.24 g of SiO2 (particle size of 15 nm), disperse it in 35 mL of deionized water by stirring, and add 50 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.6;

[0040] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, and add a 100 μm thick zinc foil with a size of 2.5 cm × 4.5 cm. After hydrothermal reaction in an oven at 120 °C for 30 h, take out the reaction kettle, naturally cool it, take out the zinc foil, wash it with deionized water and dry it;

[0041] Taking the Zn@ZSO obtained in this example as an example, when used as the negative electrode of an aqueous zinc-ion battery, its electrochemical performance is similar to that of Example 1.

[0042] Example 4

[0043] A method for preparing a composite zinc foil with a ZnSiO3 protective layer includes:

[0044] 1) Weigh 0.24 g of SiO2 (particle size of 15 nm), disperse it in 35 mL of deionized water by stirring, and add 50 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.6;

[0045] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, add a zinc foil with a size of 2.5 cm × 4.5 cm and a thickness of 50 μm, carry out hydrothermal reaction in an oven at 120 °C for 36 h, take out the reaction kettle, after natural cooling, take out the zinc foil, wash it with deionized water and dry it;

[0046] Taking Zn@ZSO obtained in this example as an example, when used as the negative electrode of an aqueous zinc-ion battery, its electrochemical performance is similar to that of Example 1.

[0047] Example 5

[0048] A preparation method of a composite zinc foil with a ZnSiO3 protective layer includes:

[0049] 1) Weigh 0.24 g of SiO2 (particle size of 15 nm), disperse it in 35 mL of deionized water by stirring, and add 50 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.6;

[0050] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, add a zinc metal foil with a size of 2.5 cm × 4.5 cm and a thickness of 100 μm, carry out hydrothermal reaction in an oven at 130 °C for 20 h, take out the reaction kettle, after natural cooling, take out the zinc foil, wash it with deionized water and dry it;

[0051] Taking Zn@ZSO obtained in this example as an example, when used as the negative electrode of an aqueous zinc-ion battery, its electrochemical performance is similar to that of Example 1.

[0052] Example 6

[0053] A preparation method of a composite zinc foil with a ZnSiO3 protective layer includes:

[0054] 1) Weigh 0.24 g of SiO2 (particle size of 15 nm), disperse it in 35 mL of deionized water by stirring, and add 70 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.8;

[0055] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, add a zinc metal foil with a size of 2.5 cm × 4.5 cm and a thickness of 100 μm, carry out hydrothermal reaction in an oven at 120 °C for 36 h, take out the reaction kettle, after natural cooling, take out the zinc foil, wash it with deionized water and dry it;

[0056] Taking Zn@ZSO obtained in this example as an example, when used as the negative electrode of an aqueous zinc-ion battery, its electrochemical performance is similar to that of Example 1.

[0057] Example 7

[0058] A preparation method of a composite zinc foil with a ZnSiO3 protective layer includes:

[0059] 1) Weigh 0.24 g of SiO2 (with a particle size of 20 nm), disperse it in 35 mL of deionized water by stirring, and add 50 μL of 2 mol L -1 NaOH solution, and the pH of the solution is 10.6;

[0060] 2) Transfer the solution obtained in step 1) to a 50 mL reaction kettle, add a 2.5 cm × 4.5 cm zinc metal foil with a thickness of 100 μm, take out the reaction kettle after hydrothermal reaction at 120 °C in an oven for 36 h, take out the zinc foil after natural cooling, wash it with deionized water and dry it;

[0061] Taking Zn@ZSO obtained in this example as an example, when used as the negative electrode of an aqueous zinc-ion battery, its electrochemical performance is similar to that of Example 1.

Claims

1. A composite zinc foil with a ZnSiO3 protective layer, wherein the ZnSiO3 protective layer is composed of a ZnSiO3 nanosheet array and has a structure with coexistence of amorphous and crystalline states; the thickness of the ZnSiO3 protective layer is 300 nm, the thickness of a single ZnSiO3 nanosheet is 15 nm, and there are abundant pores distributed in the ZnSiO3 nanosheets.

2. A preparation method of the composite zinc foil with a ZnSiO3 protective layer according to claim 1, comprising the following steps: 1) Weigh a certain amount of SiO2 and add it to deionized water, then drop a certain amount of NaOH aqueous solution and stir evenly to obtain a solution; 2) Transfer the solution obtained in step 1) into a reaction vessel, put in the zinc foil, take it out after hydrothermal reaction, cool it to room temperature, then take out the zinc foil, wash it with deionized water and dry it.

3. The preparation method of the composite zinc foil with a ZnSiO3 protective layer according to claim 2, characterized in that In Step 1), the size of the SiO2 is 10 - 50 nm, the mass is 0.12 - 0.4 g, the amount of deionized water used is 30 - 40 mL, the amount of NaOH aqueous solution used is 50 - 100 μL, and its concentration is 2 mol / L -1 .

4. The preparation method of the composite zinc foil with a ZnSiO3 protective layer according to claim 2, characterized in that In step 2), the hydrothermal reaction temperature is 120 - 140 °C, the time is 12 - 36 h, and the thickness of the zinc foil is 10 - 200 μm.

5. Application of the composite zinc foil with a ZnSiO3 protective layer according to claim 1 as a negative electrode of an aqueous zinc-ion battery.

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