Method for constructing zinc metal negative electrode by pulse thermal shock method

Abstract

The invention is applicable to the technical field of zinc metal negative electrodes, and provides a method for constructing a zinc metal negative electrode by a pulse thermal shock method, which comprises the following steps: cutting and washing commercial pure zinc foil; the zinc foil is fixed in a pulse generation device, the output pulse frequency is adjusted to be 1-8 Hz, the output voltage is adjusted to be 200-700 V, and pulse heat treatment is conducted for 10-30 s; and taking down the zinc foil after the pulse heat treatment is finished, and cutting into a circular electrode plate. The invention also provides a zinc metal negative electrode and application thereof. According to the method, pulse type rapid heat treatment is adopted, rapid heating and rapid cooling are mutually switched by adjusting a pulse process and pulse quenching, a discharge neck appears at a critical point, the surface is activated, diffusion free energy is reduced, atomic diffusion is accelerated, and formation of preferred orientation is facilitated; and shock waves generated by pulse discharge and high-speed flow of electrons and ions enable gas adsorbed by the powder to escape, and an oxide film on the surface of the powder is broken down to a certain extent, so that an impacted material is purified.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc metal negative electrodes, and in particular relates to a method for constructing a zinc metal negative electrode using a pulse thermal shock method. Background Art

[0002] As an important part of the renewable energy ecosystem, rechargeable batteries can effectively circumvent some of the drawbacks of intermittent energy storage systems. Among them, aqueous zinc batteries have shown intrinsic safety and environmental friendliness, and have attracted widespread attention in recent years. Zinc resources are abundant, not only suitable for large-scale power storage systems, but also show great application prospects in flexible energy storage devices. The energy storage mechanism of zinc-ion batteries is similar to that of "rocking chair batteries". Zn is stripped from the anode and transferred to the cathode during discharge, and deposited on the anode surface during charging. Generally, commercial zinc foil can be directly used as a negative electrode of the battery. However, it is still hindered by the following problems, such as dendrite growth, hydrogen evolution reaction and surface passivation, which will seriously affect the Coulombic efficiency (CE) and cycle life of the battery, and even cause short circuit and expansion. In response to the above problems, the solutions mainly focus on surface modification, structural design, electrolyte optimization and construction of non-metallic zinc negative electrode, but the coating surface modification process is prone to deformation and cracking during the battery cycle, increasing production costs; and electrolyte additives will also have the limitation of uneven dispersion, increasing process complexity and battery cost, which is not conducive to large-scale application. Current laboratory research often directly uses commercial zinc foil. Zinc metal is easy to process on a large scale, so direct intrinsic structure design of zinc metal foil is the only way for the actual large-scale application of zinc batteries in the future. However, a large number of defects such as cracks, protrusions, and dents will be generated during the rolling process, which will accelerate the deterioration of the tip effect.

[0003] Metallic zinc has a hexagonal close-packed (HCP) structure, and the electrochemical behavior of the zinc anode is determined by the Zn 2+ / Zn stripping / deposition occurs on Zn anodes and is therefore affected by their surface atomic structure, especially for the (002), (100) and (110) crystal planes. The surface atoms on the (002) crystal plane present a regular hexagonal arrangement, resulting in a relatively smooth stacking surface that is conducive to uniform Zn deposition. In addition, the (002) plane has more stable thermodynamic properties than other crystal planes, reducing side reactions such as hydrogen evolution, corrosion and by-products. Therefore, most studies have focused on constructing an ideal (002) texture or inducing preferential deposition of the (002) plane on Zn anodes. The main strategy at present is to use organic electrolyte additives to induce Zn (002) texture homoepitaxial electrodeposition. However, organic components will limit the application scenarios of aqueous batteries and require additional process steps. In addition, the stable thermodynamic properties of the (002) plane will lead to low reaction kinetics during electrochemical plating / stripping. Scratches and pits on the surface of zinc foil will lead to uneven distribution of electric field and Zn ion concentration, promote side reactions, and then strengthen the defects on the surface of zinc foil, forming a vicious circle. Secondly, electrolyte additives will have the limitation of uneven dispersion. Other crystal planes, such as (100), (101) and (110), have been criticized as not conducive to uniform zinc deposition and are rarely studied. In fact, the (110) plane is a highly reactive crystal plane. Zn 2+ Ions have faster ion reaction kinetics on these planes, and their fast ion reaction kinetics are more rapid than that of the (002) crystal plane, which can suppress side reactions such as hydrogen evolution and corrosion, thereby achieving high Coulomb efficiency. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a method for constructing a zinc metal negative electrode by a pulse thermal shock method, aiming to solve the problems raised in the above background technology.

[0005] The embodiment of the present invention is implemented as follows: a method for constructing a zinc metal negative electrode by a pulse thermal shock method, comprising the following steps:

[0006] (1) Pre-treatment operations of cutting and washing commercial pure zinc foil;

[0007] (2) Fixing the pretreated zinc foil in a pulse generator, adjusting the output pulse frequency to 1-8 Hz, the output voltage to 200-700 V, and performing pulse heat treatment for 10-30 s;

[0008] (3) After the pulse heat treatment, remove the zinc foil and cut it.

[0009] Preferably, in step (1), the washing is carried out by ultrasonic washing with ethanol for 3-8 minutes.

[0010] Preferably, in step (1), the commercial pure zinc foil has a thickness of 10-300 μm.

[0011] Preferably, the commercial pure zinc foil has a thickness of 30 μm.

[0012] Preferably, in step (2), the output pulse frequency is 3 Hz, the output voltage is 500 V, and the time is 10 s.

[0013] Another object of an embodiment of the present invention is to provide a zinc metal negative electrode, which is obtained by the above method.

[0014] Another object of an embodiment of the present invention is to provide an application of a zinc metal negative electrode in the preparation of a zinc battery.

[0015] Preferably, the zinc metal negative electrode is cut into circular electrode sheets and assembled into a zinc battery in an air environment.

[0016] A method for constructing a zinc metal negative electrode by a pulse thermal shock method provided in an embodiment of the present invention adopts a pulse rapid thermal treatment, which is a non-equilibrium, non-radiative chemical thermal treatment method. Since the melting point of zinc metal is relatively low (~420°C), by adjusting the pulse process, the pulse quenching method switches between rapid heating and rapid cooling, and a "discharge neck" appears at its critical point, the surface is activated, the diffusion free energy is reduced, and the atomic diffusion is accelerated, which is conducive to the formation of preferential orientation. At the same time, the shock wave generated by the pulse discharge and the high-speed flow of electrons and ions can cause the gas adsorbed by the powder to escape, and the oxide film on the surface of the powder is broken down to a certain extent, so that the impacted material is purified, thereby not only changing the preferred orientation of the crystal plane of the commercial zinc foil, but also self-cleaning the surface of the zinc foil without the need for additional processes;

[0017] The embodiments of the present invention can directly modify commercial zinc foil, the raw material source is sufficient, the price is low, the preparation method is simple, and it is suitable for large-scale development; the preparation process is green and pollution-free, and the zinc foil can achieve a (110) texture within only 10 seconds; when the prepared zinc foil is used as the negative electrode of a zinc battery, it has relatively excellent cycle stability and coulombic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of constructing a zinc metal negative electrode using a pulse thermal shock method provided in an embodiment of the present invention;

[0019] Figure 2 XRD patterns of samples prepared in Examples 1-3 of the present invention;

[0020] Figure 3 Another XRD pattern of the sample prepared in Example 1-3 of the present invention;

[0021] Figure 4 The stability test results of the battery prepared in Example 4 of the present invention;

[0022] Figure 5 This is the nucleation overpotential test result of the battery prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0025] Example 1: A zinc metal negative electrode, the preparation device thereof is as follows Figure 1 As shown, the specific steps include:

[0026] (1) Prepare the EPM-C pulse generator using commercial pure zinc foil with a thickness of 30 μm;

[0027] (2) Cut the zinc foil into strips of 20 × 50 mm, rinse with ethanol ultrasonically for 5 min, and take it out;

[0028] (3) Fix the cut and rinsed zinc foil in the pulse generator and adjust the process parameters, that is, fix the output pulse frequency to 3 Hz and change the output voltage to 500 V through the operation panel in the pulse transmitter to perform pulse heat treatment. The whole process lasts for 10 seconds.

[0029] (4) After the pulse heat treatment is completed, remove the zinc foil.

[0030] Example 2: Compared with Example 1, other preparation steps and parameters remain unchanged, only the output voltage is changed to 300V.

[0031] Example 3: Compared with Example 1, other preparation steps and parameters remain unchanged, only the output voltage is changed to 400V.

[0032] XRD tests were performed on the samples prepared in Examples 1-3 and commercial zinc foil, and the results were as follows: Figure 2 , Figure 3 As shown, according to Figure 2 and Figure 3 It can be seen that when the applied voltage is 500V, the (110) characteristic diffraction peak at 70.7° shows obvious preferential growth, and the (110) crystal plane exhibits higher surface energy and lower dissolution activation energy, with faster ion reaction kinetics and higher Coulomb efficiency; secondly, as the voltage increases, the impurities on the zinc foil surface are effectively removed.

[0033] Example 4. A Zn||Zn symmetrical battery, the preparation method of which comprises the following steps: using the two zinc foils prepared in Example 1 as positive and negative electrodes, using Whatman glass fiber diaphragm (GF / D) as diaphragm, and using 2M zinc sulfate aqueous solution as electrolyte to assemble into a Zn||Zn symmetrical battery.

[0034] Example 5. A Zn||Ti asymmetric battery, the preparation method of which comprises the following steps: using the zinc foil prepared in Example 1 as the negative electrode sheet, using the titanium foil as the positive electrode sheet, using Whatman glass fiber diaphragm (GF / D) as the diaphragm, and using 2M zinc sulfate aqueous solution as the electrolyte to assemble a Zn||Ti asymmetric battery.

[0035] Comparative Example 1: A Zn||Zn symmetrical battery, the preparation method of which comprises the following steps: using two commercial zinc foils as positive and negative electrodes, a Whatman glass fiber separator (GF / D) as a separator, and a 2M zinc sulfate aqueous solution as an electrolyte to assemble a Zn||Zn symmetrical battery.

[0036] Comparative Example 2: A Zn||Ti asymmetric battery, the preparation method of which comprises the following steps: using commercial zinc foil as the negative electrode sheet, titanium foil as the positive electrode sheet, a Whatman glass fiber diaphragm (GF / D) as the diaphragm, and a 2M zinc sulfate aqueous solution as the electrolyte to assemble a Zn||Ti asymmetric battery.

[0037] The stability of the batteries prepared in Example 4 and Comparative Example 1 during the electroplating / stripping process was tested using a Xinwei battery tester, and the results were as follows: Figure 4 As shown, according to Figure 4 It can be seen that at 1 mA cm -2 Current density (capacity 1mAh cm -2 ), the battery prepared by the pulse treated zinc foil can be stably cycled for more than 400h, and the polarization voltage is much lower than that of commercial pure zinc foil;

[0038] The nucleation overpotential of the batteries prepared in Example 5 and Comparative Example 2 was tested, and the results were as follows: Figure 5 As shown, according to Figure 5 It can be seen that the nucleation overpotential of the zinc foil after pulse shock is lower than that of the commercial pure zinc foil, indicating that the (110) textured zinc has faster electrochemical kinetics.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing a zinc metal negative electrode by a pulse thermal shock method, characterized in that: The following steps are involved: (1) Pre-treatment operations of cutting and washing commercial pure zinc foil; (2) Fixing the pretreated zinc foil in a pulse generator, adjusting the output pulse frequency to 1-8 Hz, the output voltage to 200-700 V, and performing pulse heat treatment for 10-30 s; (3) After the pulse heat treatment, remove the zinc foil and cut it.

2. The method for constructing a zinc metal negative electrode by a pulse thermal shock method according to claim 1, characterized in that: In step (1), the washing is carried out by ultrasonic washing with ethanol for 3-8 minutes.

3. The method for constructing a zinc metal negative electrode by a pulse thermal shock method according to claim 1, characterized in that: In step (1), the commercial pure zinc foil has a thickness of 10-300 μm.

4. The method for constructing a zinc metal negative electrode by a pulse thermal shock method according to claim 3, characterized in that: The commercial pure zinc foil has a thickness of 30 μm.

5. The method for constructing a zinc metal negative electrode by a pulse thermal shock method according to claim 4, characterized in that: In step (2), the output pulse frequency is 3 Hz, the output voltage is 500 V, and the time is 10 s.

6. A zinc metal negative electrode, characterized in that: It is obtained by the method described in any one of claims 1 to 5.

7. Use of the zinc metal negative electrode as claimed in claim 6 in the preparation of a zinc battery.

8. The use according to claim 7, characterized in that: The zinc metal negative electrode is cut into circular electrode sheets and assembled into a zinc battery in an air environment.

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