Zinc negative electrode with piezoelectric protective layer and preparation method and application thereof

Abstract

The application discloses a zinc negative electrode with a piezoelectric protective layer and a preparation method and application thereof, and relates to the technical field of secondary zinc-based batteries. The method comprises the following steps: dissolving an ester-capped left-handed polylactic acid in dichloromethane solvent, then adding a DMF solution to promote the conductive performance of the solution and BaTiO3 nano material, uniformly mixing, and obtaining a precursor solution; uniformly applying the precursor solution on a pretreated zinc sheet through an electrostatic spinning method or a spin coating method; and after drying, the piezoelectric protective layer is prepared on the pretreated zinc sheet. The piezoelectric characteristics of the protective layer can be further improved by adding BaTiO3 nano particles in the PLLA base, so that the electric field distribution on the surface of the zinc negative electrode is balanced, and the growth of zinc dendrites is slowed down.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary zinc-based batteries, and in particular to a zinc negative electrode with a piezoelectric protective layer, a preparation method thereof, and applications thereof. Background Art

[0002] Metallic zinc has a relatively low redox potential (-0.76 V vs. SHE) and a high theoretical capacity (~820 mAh·g -1 / ~5855 mAh·cm -3 ), and the electrolyte can be water, offering excellent chemical stability, low cost, and easy recycling. Metallic zinc is a commonly used anode material in green batteries, including secondary zinc-based batteries such as alkaline zinc-nickel batteries, alkaline zinc-silver batteries, neutral zinc-manganese batteries, and zinc-bromine flow batteries. Therefore, improving the stability and electrochemical performance of zinc anodes is a key research priority.

[0003] However, the zinc anode faces various unfavorable bottlenecks. First, because the reduction potential of the zinc anode is lower than that of the standard hydrogen electrode, hydrogen evolution occurs when it comes into direct contact with the electrolyte. Furthermore, inevitable corrosion and byproduct deposition can lead to uneven zinc deposition, resulting in uneven electric field distribution and exacerbated zinc dendrite growth. These zinc dendrites can puncture the diaphragm and cause a short circuit. Furthermore, the hydrogen gas produced by the hydrogen evolution reaction increases internal pressure in the battery, increasing the possibility of explosion. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, the present invention provides a zinc anode with a piezoelectric protective layer, as well as a preparation method and application thereof. This method utilizes ester-terminated L-lactic acid (PLLA) as a substrate and BaTiO3 as a filler. Through electrospinning or spin coating, a PLLA-based zinc anode protective layer encapsulated with BaTiO3 nanofillers is prepared. This method is simple to operate and has a low production cost. The addition of BaTiO3 nanoparticles to the PLLA substrate further enhances the piezoelectric properties of the protective layer, thereby balancing the electric field distribution on the zinc anode surface and slowing the growth of zinc dendrites.

[0005] The first object of the present invention is to provide a method for preparing a piezoelectric protective layer, comprising the following steps:

[0006] The ester-terminated L-polylactic acid was dissolved in dichloromethane solvent, and then DMF solution and BaTiO3 nanomaterials were added and mixed uniformly to obtain a precursor solution;

[0007] The precursor solution is evenly applied on the pretreated zinc sheet through an electrostatic spinning method or a spin coating method, and after drying, a piezoelectric protective layer is prepared on the pretreated zinc sheet.

[0008] Preferably, the precursor solution is evenly applied to the pretreated zinc sheet by an electrospinning method, including: using a conductive glue to stick the pretreated zinc sheet to an electrospinning receiving roller, and then electrospinning the precursor solution to obtain a piezoelectric protective layer on the pretreated zinc sheet.

[0009] Preferably, the parameters during the electrospinning process include: the electrospinning syringe needle is connected to the positive electrode, the voltage is 15-20 kV; the receiving roller is connected to the negative electrode, the voltage is -8~-5 kV;

[0010] The distance between the needle tip and the receiving roller is 10-15 cm, the speed of the receiving roller is 120-150 r / min, the left and right translation distance of the needle is 80-120 mm, and the translation speed is 180-250 mm / min;

[0011] The syringe containing the precursor solution was pushed at a speed of 0.1-0.2 mm / min;

[0012] During the spinning process, the temperature is maintained at 10-15°C and the humidity is maintained at 20-50%.

[0013] Preferably, the precursor solution is evenly applied to the pretreated zinc sheet by spin coating, and the spin coating parameters are an acceleration of 400-600 r / s. 2 ; The spin coating speed is 1800-2000 r / s; the spin coating time is 20-40s.

[0014] Preferably, the mass concentration of the ester-terminated L-polylactic acid in the precursor solution is 10-15%; the mass concentration of the BaTiO3 nanomaterial in the precursor solution is 5-10%.

[0015] Preferably, the pre-treated zinc sheet comprises: grinding and polishing the zinc sheet using sandpaper of 2000, 3000, 5000 and 10000 mesh in sequence, and then cleaning the surface-polished metal zinc with deionized water, ethanol and acetone under ultrasonic conditions, respectively, at a treatment temperature of 20-25°C and a treatment time of 20-40 minutes. After the treatment, the zinc sheet is dried in a vacuum drying oven at 80-100°C for 5-8 hours to obtain the pre-treated zinc sheet.

[0016] A second object of the present invention is to provide a piezoelectric protective layer.

[0017] The third object of the present invention is to provide an application of a piezoelectric protective layer on a zinc electrode.

[0018] A fourth object of the present invention is to provide a zinc negative electrode with a piezoelectric protective layer, comprising a zinc sheet and a piezoelectric protective layer attached to the zinc sheet.

[0019] A fifth object of the present invention is to provide a zinc negative electrode with a piezoelectric protective layer for use in a secondary zinc-based battery.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a zinc anode with a piezoelectric protective layer, as well as a preparation method and application thereof. This method uses PLLA as a substrate and BaTiO3 nanomaterials as inorganic fillers, and utilizes electrospinning / spin coating or other methods to prepare a piezoelectric protective layer in a single step. The unique interaction between PLLA and the zinc sheet ensures the stable presence of the protective layer on the zinc sheet; the high piezoelectricity of the BaTiO3 nanomaterials is utilized to further enhance the piezoelectric output of the protective layer. This method is simple to operate and low in cost, ensuring that the PLLA-based zinc anode protective layer containing BaTiO3 nanofillers has a high piezoelectric output, effectively balancing the internal electric field of zinc-ion batteries.

[0022] The PLLA material used in the present invention not only has good hydrophobicity but also has piezoelectric properties. A layer of PLLA material is coated on the surface of the zinc negative electrode, which can effectively isolate the water molecules in the electrolyte from direct contact with the zinc sheet, thereby reducing the corrosion of the electrolyte on the zinc negative electrode and slowing down the occurrence of side reactions. Although the PLLA material itself has piezoelectric properties, the microstress generated during the zinc negative electrode deposition and stripping process is not enough to induce the protective layer to generate a local electric field. Therefore, BaTiO3 nanofillers are selected to enhance the piezoelectric effect of the protective layer. In this way, the internal stress generated during the zinc ion deposition and stripping process can induce the protective layer to generate a local electric field, thereby regulating the built-in electric field inside the battery, thereby inducing uniform deposition of zinc ions, slowing the growth of dendrites, and increasing the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flowchart of the preparation method of Example 1 (a) and Example 2 (b) of the present invention.

[0024] Figure 2 These are optical and SEM images of the zinc negative electrode protective layers prepared by Example 1 and Example 2 of the method of the present invention.

[0025] Figure 3 1 is the XRD diagram of the zinc negative electrode protective layer prepared by Example 1 and Example 2 of the method of the present invention.

[0026] Figure 4 1 is an output performance diagram of the zinc negative electrode protective layer prepared by Example 1 and Example 2 of the method of the present invention.

[0027] Figure 5 1 is the Tafel diagram of the zinc symmetrical battery of Example 1, Example 2 and Comparative Example 1 of the method of the present invention.

[0028] Figure 6 1 is a graph showing the relationship between voltage and cycle number of the zinc symmetrical battery of Example 1 and Comparative Example 1 under conditions of certain current density and capacity. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0030] The present invention primarily relies on two approaches: designing a three-dimensional framework structure, and surface modification, namely alloying or applying a protective coating. Ferroelectric materials, due to their high dielectric constant and spontaneous polarization, can effectively address these issues. First, the high dielectric constant of ferroelectric materials can suppress the formation of a space charge layer, thereby improving the transport efficiency of zinc ions. Second, when a coating containing a ferroelectric material is applied to the zinc negative electrode, a built-in electric field is generated near the coating. During downward polarization, the electric field lines are directed from the metal protrusions toward the coating surface. Under the influence of the electric field, zinc ions are transported to the base of the protrusions, reducing the "tip effect" and thus inhibiting dendrite growth. Given that ferroelectric materials are generally piezoelectric, they can also regulate ion transport at the electrode by effectively utilizing volume changes. If a piezoelectric material can be introduced into the substrate, a piezoelectric field (i.e., a piezoelectric effect-induced field) will be generated under pressure near the electrode surface. Specifically, when compressive stress is applied to the piezoelectric layer, a piezoelectric field is generated directly from the cathode to the anode. This generated piezoelectric field can be considered an ion pump, driving the migration and uniform distribution of ions toward the electrodes.

[0031] Currently, there is little research on fully degradable and piezoelectric biomaterials. The present invention selects L-polylactic acid (PLLA) with piezoelectric properties, high safety and degradability as the base material of the zinc negative electrode protective layer, and adds BaTiO3 with a high dielectric constant. A L-polylactic acid-based zinc negative electrode protective layer containing BaTiO3 nanofiller with piezoelectric properties can be obtained through a one-step method such as electrospinning / spin coating.

[0032] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a piezoelectric protective layer, comprising the following steps:

[0033] The ester-terminated L-polylactic acid was dissolved in dichloromethane solvent, and then DMF solution and BaTiO3 nanomaterials were added and mixed uniformly to obtain a precursor solution;

[0034] The precursor solution is evenly applied on the pretreated zinc sheet through an electrostatic spinning method or a spin coating method, and after drying, a piezoelectric protective layer is prepared on the pretreated zinc sheet.

[0035] Among them, DMF solution is used to promote the conductive properties of the solution.

[0036] The present invention uses a polymer with ferroelectric properties as a protective layer for the zinc negative electrode. It can not only make good use of the ferroelectric / piezoelectric field brought by the ferroelectric material to regulate the electric field inside the battery, thereby inhibiting the growth of dendrites, but also further prevent direct contact between the electrolyte and the zinc negative electrode, reducing the occurrence of side reactions such as corrosion.

[0037] According to the present invention, the precursor solution is evenly applied to the pretreated zinc sheet by an electrostatic spinning method, including: using a conductive glue to stick the pretreated zinc sheet to an electrostatic spinning receiving roller, and then electrostatically spinning the precursor solution to obtain a piezoelectric protective layer on the pretreated zinc sheet.

[0038] Specifically, the parameters during the electrospinning process include: the electrospinning syringe needle is connected to the positive electrode with a voltage of 15-20 kV; the receiving roller is connected to the negative electrode with a voltage of -8~-5 kV;

[0039] The distance between the needle tip and the receiving roller is 10-15 cm, the speed of the receiving roller is 120-150 r / min, the left and right translation distance of the needle is 80-120 mm, and the translation speed is 180-250 mm / min;

[0040] The syringe containing the precursor solution was pushed at a speed of 0.1-0.2 mm / min;

[0041] During the spinning process, the temperature is maintained at 10-15°C and the humidity is maintained at 20-50%.

[0042] According to the present invention, the precursor solution is evenly applied to the pretreated zinc sheet by spin coating, and the spin coating parameters are an acceleration of 400-600 r / s. 2 ; The spin coating speed is 1800-2000 r / s; the spin coating time is 20-40s.

[0043] The mass concentration of the ester-terminated L-polylactic acid in the precursor solution is 10-15%; the mass concentration of the BaTiO3 nanomaterial in the precursor solution is 5-10%.

[0044] The pre-treated zinc sheet comprises: grinding and polishing the zinc sheet with sandpaper of 2000, 3000, 5000 and 10000 meshes in sequence, and then cleaning the surface-polished metal zinc with deionized water, ethanol and acetone under ultrasonic conditions, respectively, at a treatment temperature of 20-25° C. and a treatment time of 20-40 minutes. After the treatment, the zinc sheet is dried in a vacuum drying oven at 80-100° C. for 5-8 hours to obtain the pre-treated zinc sheet.

[0045] In one embodiment, a method for preparing a PLLA-based zinc negative electrode protective layer containing BaTiO3 nanofillers by electrospinning comprises the following steps:

[0046] Step 1: Prepare the precursor solution: Weigh 1.2 g of ester-terminated L-polylactic acid (OH-PLLA-COOR, hereinafter referred to as PLLA) and dissolve it in dichloromethane (DCM). Alternately stir for 30 minutes and sonicate for 20 minutes three times. Once the PLLA is fully dissolved until the solution is clear and transparent, add 3 mL of DMF and 0.12 g of BaTiO3 nanomaterials to the mixture. Stir for 60 minutes to thoroughly mix, then allow the solution to stand to eliminate bubbles. Keep the temperature below 10°C throughout the process to minimize DCM volatilization.

[0047] Step 2: Zinc sheet treatment: Cut the zinc sheet into 10 x 12 cm pieces and grind and polish them using 2000, 3000, 5000, and 10000 grit sandpaper, respectively. The polished zinc metal is then cleaned using deionized water, ethanol, and acetone under ultrasonic conditions at 25°C for 30 minutes. After treatment, the zinc is dried in a vacuum oven at 80°C for 6 hours to obtain a pure zinc anode. Grinding not only removes the oxide layer on the zinc sheet but also makes the surface smoother, which not only facilitates the adhesion of the PLLA layer but also reduces the possibility of dendrite growth.

[0048] Step 3: Use conductive glue to stick the treated zinc sheet to the receiving roller of electrospinning. Wrap the remaining part of the receiving roller with plastic wrap to avoid contamination. Use the syringe of the electrospinning syringe to draw 5 mL of PLLA solution. Connect the syringe to the electrospinning needle and place it on the electrospinning machine for spinning to obtain a PLLA-based zinc negative electrode protective layer with BaTiO3 nanofiller.

[0049] Electrospinning parameters: The needle tip was connected to the positive electrode at a voltage of 17 kV; the receiving drum was connected to the negative electrode at a voltage of -5 kV. The distance between the needle tip and the receiving drum was 12 cm, the receiving drum rotation speed was 140 rpm, the needle tip translation distance was 100 mm, and the translation speed was 200 mm / min. The syringe containing the precursor solution was pushed at a speed of 0.15 mm / min.

[0050] Spinning environment parameters: the temperature was maintained at 10°C and the humidity was maintained at 30% during the spinning process.

[0051] Step 4: After spinning is completed, remove the prepared sample and dry it under vacuum at 30°C for 12 hours.

[0052] In one embodiment, a method for preparing a PLLA-based zinc negative electrode protective layer containing BaTiO3 nanofillers is performed by spin coating.

[0053] Step 1: Prepare the precursor solution: Weigh 1.2 g of PLLA, add 10 mL of dichloromethane (DCM) and 0.12 g of BaTiO nanomaterials. Stir for 3 hours, then sonicate for 30 minutes to obtain a clear, transparent solution. Allow the solution to stand to eliminate bubbles. Keep the temperature below 10°C throughout the process to minimize DCM volatilization.

[0054] Step 2: Treatment of zinc sheet: Cut the zinc sheet into 6*6cm size, and grind and polish the zinc sheet with 2000, 3000, 5000 and 10000 sandpaper in turn. Then, use deionized water, ethanol and acetone to clean the polished metal zinc under ultrasonic conditions. The treatment temperature is 25℃ and the treatment time is 30min. After the treatment, dry it in a vacuum drying oven at 80℃ for 6h to obtain a pure zinc negative electrode.

[0055] Step 3: Place the treated zinc sheet on a spin coater for spin coating.

[0056] Spin coating parameters: acceleration is 500 r / s 2 ; The spin coating speed is 2000 r / s; the spin coating time is 30s.

[0057] Step 4: After the spin coating is completed, remove the prepared sample and dry it in a vacuum at 30°C for 12 hours.

[0058] A second aspect of the present invention provides a piezoelectric protective layer.

[0059] A third aspect of the present invention provides an application of a piezoelectric protective layer on a zinc electrode.

[0060] A fourth aspect of the present invention provides a zinc negative electrode with a piezoelectric protective layer, comprising a zinc sheet and a piezoelectric protective layer attached to the zinc sheet.

[0061] A fifth aspect of the present invention provides an application of a zinc negative electrode having a piezoelectric protective layer in a secondary zinc-based battery.

[0062] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0063] Example 1

[0064] See also Figure 1 (a), the preparation method comprises:

[0065] (1) Weigh 1.2 g of PLLA and dissolve it in DCM. Stir for 30 min and sonicate for 20 min alternately three times. After PLLA is fully dissolved until the solution is clear and transparent, add 3 mL of DMF and 0.12 g of BaTiO3 nanomaterials to the mixed solution. Stir for 60 min to mix it evenly. Then let it stand to eliminate bubbles in the solution to obtain a precursor solution. The whole process should be carried out at below 10°C to minimize the volatilization of DCM.

[0066] (2) The zinc sheet was cut into a size of 10*12 cm, and the zinc sheet was ground and polished with 2000, 3000, 5000 and 10000 sandpaper in sequence. Then, the surface polished metal zinc was cleaned with deionized water, ethanol and acetone under ultrasonic conditions. The treatment temperature was 25℃ and the treatment time was 30 min. After the treatment, it was dried in a vacuum drying oven at 80℃ for 6 h to obtain a pure zinc negative electrode.

[0067] (3) Use conductive glue to stick the treated zinc sheet to the receiving roller of electrospinning. Wrap the remaining part of the receiving roller with plastic wrap to avoid contamination. Use the syringe of the electrospinning syringe to draw 5 mL of the precursor solution (PLLA solution). Connect the syringe to the electrospinning needle and place it on the electrospinning machine for spinning.

[0068] Electrospinning parameters: The needle tip was connected to the positive electrode at a voltage of 17 kV; the receiving drum was connected to the negative electrode at a voltage of -5 kV. The distance between the needle tip and the receiving drum was 12 cm, the receiving drum rotation speed was 140 rpm, the needle tip translation distance was 100 mm, and the translation speed was 200 mm / min. The syringe containing the precursor solution was pushed at a speed of 0.15 mm / min.

[0069] Spinning environment parameters: the temperature was maintained at 10°C and the humidity was maintained at 30% during the spinning process.

[0070] After spinning, the prepared sample was removed and dried at 30 °C in a vacuum for 12 h to obtain the BaTiO3 nanofiller PLLA-based zinc negative electrode protective layer (PLLA-BaTiO3@Zn E).

[0071] Example 2

[0072] See also Figure 1 (b), the preparation method comprises:

[0073] (1) Weigh 1.2 g of PLLA, add 10 mL of dichloromethane (DCM) and 0.12 g of BaTiO3 nanomaterials, stir for 3 h, and then ultrasonicate for 30 min to obtain a clear and transparent solution. Then let the solution stand to eliminate bubbles and obtain a precursor solution; the whole process must be carried out below 10 °C to minimize the volatilization of DCM.

[0074] (2) The zinc sheet was cut into a size of 10*12 cm, and the zinc sheet was ground and polished with 2000, 3000, 5000 and 10000 sandpaper in sequence. Then, the surface polished metal zinc was cleaned with deionized water, ethanol and acetone under ultrasonic conditions. The treatment temperature was 25℃ and the treatment time was 30 min. After the treatment, it was dried in a vacuum drying oven at 80℃ for 6 h to obtain a pure zinc negative electrode.

[0075] (3) Place the treated zinc sheet on a spin coater and spin coat the precursor solution onto the treated zinc sheet; spin coating parameters: acceleration is 500 r / s 2 The spin coating speed is 2000 r / s and the spin coating time is 30s.

[0076] After the spin coating was completed, the prepared sample was removed and dried at 30°C in a vacuum for 12 h to obtain a piezoelectric protective layer (PLLA-BaTiO3@ZnS) on the pretreated zinc sheet.

[0077] Comparative Example 1

[0078] The zinc sheet was ground and polished with 2000, 3000, 5000 and 10000 sandpaper in turn, and then the surface-polished metal zinc was cleaned with deionized water, ethanol and acetone under ultrasonic conditions. The treatment temperature was 25°C and the treatment time was 30 minutes. After the treatment, it was dried in a vacuum drying oven at 80°C for 6 hours to obtain a pure zinc negative electrode (BareZn).

[0079] Example 3:

[0080] (1) Zinc symmetrical batteries were prepared using the samples obtained in Example 1, Example 2, and Comparative Example 1 as the positive and negative electrodes, respectively, a solution containing 2M ZnSO4 as the electrolyte, and glass fiber as the separator.

[0081] (2) Symmetrical battery charge and discharge tests were conducted at room temperature with a current density of 1 mAh / cm 2 The charge and discharge capacity of one cycle is 0.5mAh / cm 2 .

[0082] In order to illustrate the relevant performance of the piezoelectric protective layer provided by the present invention, it is described in conjunction with the accompanying drawings.

[0083] from Figure 2 It can be seen that the surface uniformity and flatness of the left-handed polylactic acid-based zinc negative electrode protective layer containing BaTiO3 nanofiller with high piezoelectric performance prepared by electrospinning and spin coating are good, and the BaTiO3 nanofiller can be evenly distributed.

[0084] from Figure 3 It can be seen that the zinc negative electrode protective layer prepared by electrospinning and spin coating does contain BaTiO3 nanofillers, which is consistent with the standard card peak position. The standard peak corresponding to PLLA has not been detected. The reason is that its crystallinity is not as good as that of BaTiO3 nanofillers and its content is relatively low.

[0085] from Figure 4 It can be seen that the prepared zinc negative electrode protective layer does have piezoelectric properties, and can output voltage under the action of pressure, thereby adjusting the electric field distribution.

[0086] from Figure 5 It can be seen that the zinc negative electrode protective layer with piezoelectric properties can reduce the corrosion of the electrolyte on the Zn-Zn symmetrical battery, and the corrosion current is greatly reduced.

[0087] from Figure 6 It can be seen that the zinc negative electrode protective layer with piezoelectric properties can improve the cycle life of the Zn-Zn symmetric battery.

[0088] The present invention describes preferred embodiments and their effects. However, those skilled in the art, once informed of the basic inventive concept, may make additional changes and modifications to these embodiments. Therefore, it is intended that the appended claims be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the invention.

[0089] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a piezoelectric protective layer, characterized in that: The following steps are involved: The ester-terminated L-polylactic acid was dissolved in dichloromethane solvent, and then DMF solution and BaTiO3 nanomaterials were added and mixed uniformly to obtain a precursor solution; The precursor solution is evenly applied on the pretreated zinc sheet through an electrostatic spinning method or a spin coating method, and after drying, a piezoelectric protective layer is prepared on the pretreated zinc sheet.

2. The method for preparing a piezoelectric protective layer according to claim 1, wherein: The precursor solution is evenly applied to the pretreated zinc sheet by an electrostatic spinning method, including: using a conductive glue to stick the pretreated zinc sheet to an electrostatic spinning receiving roller, and then electrostatically spinning the precursor solution to obtain a piezoelectric protective layer on the pretreated zinc sheet.

3. The method for preparing a piezoelectric protective layer according to claim 2, wherein: The parameters during the electrospinning process include: the electrospinning syringe needle is connected to the positive electrode with a voltage of 15-20 kV; the receiving roller is connected to the negative electrode with a voltage of -8~-5 kV; The distance between the needle tip and the receiving roller is 10-15 cm, the speed of the receiving roller is 120-150 r / min, the left and right translation distance of the needle is 80-120 mm, and the translation speed is 180-250 mm / min; The syringe containing the precursor solution was pushed at a speed of 0.1-0.2 mm / min; During the spinning process, the temperature is maintained at 10-15°C and the humidity is maintained at 20-50%.

4. The method for preparing a piezoelectric protective layer according to claim 1, wherein: The precursor solution is evenly applied on the pretreated zinc sheet by spin coating. The spin coating parameters are acceleration of 400-600 r / s. 2 ; The spin coating speed is 1800-2000 r / s; The spin coating time is 20-40s.

5. The method for preparing a piezoelectric protective layer according to claim 1, wherein: The mass concentration of the ester-terminated L-polylactic acid in the precursor solution is 10-15%; the mass concentration of the BaTiO3 nanomaterial in the precursor solution is 5-10%.

6. The method for preparing a piezoelectric protective layer according to claim 1, wherein: The pre-treated zinc sheet comprises: grinding and polishing the zinc sheet with sandpaper of 2000, 3000, 5000 and 10000 meshes in sequence, and then cleaning the surface-polished metal zinc with deionized water, ethanol and acetone under ultrasonic conditions, respectively, at a treatment temperature of 20-25° C. and a treatment time of 20-40 minutes. After the treatment, the zinc sheet is dried in a vacuum drying oven at 80-100° C. for 5-8 hours to obtain the pre-treated zinc sheet.

7. A piezoelectric protective layer prepared by the method according to claims 1 to 6.

8. Use of the piezoelectric protective layer according to claim 7 on a zinc electrode.

9. A zinc negative electrode having a piezoelectric protective layer, characterized in that: The invention comprises a zinc sheet and a piezoelectric protective layer attached to the zinc sheet.

10. Use of the zinc negative electrode with a piezoelectric protective layer according to claim 9 in a secondary zinc-based battery.

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