Zinc negative electrode protective layer, zinc metal negative electrode, preparation method thereof and zinc metal battery

Abstract

The present invention provides a zinc negative electrode protective layer, which is prepared from zinc metal-oxide salts and a polymer. The present application also provides a zinc metal negative electrode and a method for preparing the same. The present application further provides a zinc metal full battery. The zinc negative electrode protective layer provided by the present application is a zinc metal protective layer with strong hydrogen evolution inhibition ability, abundant zincophilic sites and high zinc ion conductivity, which can effectively inhibit water-induced side reactions and dendrite growth, and is expected to be applied to industrial production. The zinc negative electrode protective layer of the present invention is used in zinc metal symmetric batteries and zinc|vanadium pentoxide (V2O5) full batteries, and the batteries exhibit low polarization voltage, excellent rate performance and stable cycle performance, showing good practical application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc metal batteries, and particularly relates to a zinc negative electrode protective layer, a zinc metal negative electrode, a preparation method thereof, and a zinc metal battery. Background Art

[0002] Zinc metal electrodes have advantages such as high volumetric specific capacity (5855 mAh·cm -3 ) and relatively low redox potential (-0.76 V·vs·SHE). Therefore, aqueous zinc metal batteries with metallic zinc as the negative electrode are expected to be applied in the field of large-scale energy storage in the future. In addition, compared with the currently widely used organic lithium-ion batteries, aqueous zinc metal batteries have significant advantages in terms of safety, cost, and environmental friendliness.

[0003] However, metallic zinc is thermodynamically unstable in aqueous solutions and is prone to side reactions such as hydrogen evolution and self-corrosion, which will cause irreversible losses of the electrolyte and the active substance zinc. A large amount of hydrogen evolution will cause the battery to bulge and swell, resulting in a sharp increase in the internal resistance of the battery. In addition, during the charging process, the uneven deposition of zinc metal easily induces the growth of zinc dendrites, piercing the separator and causing the battery to short-circuit and fail.

[0004] In order to improve the thermodynamic stability of the zinc metal negative electrode and simultaneously achieve uniform dendrite-free deposition of zinc metal, there are currently three commonly used strategies: optimizing the electrolyte, constructing a three-dimensional current collector, and designing an artificial protective layer; among them, designing an artificial protective layer is a simple and effective strategy that can not only significantly inhibit side reactions but also regulate the uniform deposition of zinc.

[0005] Generally speaking, in an aqueous zinc metal battery, the artificial protective layer on the surface of the zinc metal negative electrode should have a high hydrogen evolution energy barrier, strong zincophilicity, and high ionic conductivity. Currently, most of the reported artificial protective layers used to modify zinc metal do not meet all the above requirements, and there are problems such as limited hydrogen evolution inhibition ability and low ionic conductivity. Moreover, the cycle life of the modified zinc metal electrode is limitedly improved, making it difficult to meet practical applications. Therefore, it is urgent to prepare and develop an artificial protective layer with high hydrogen evolution energy barrier, strong zincophilicity, and high ionic conductivity from the perspective of material design to stabilize the zinc metal negative electrode and thus achieve a long-life zinc metal battery. Summary of the Invention

[0006] The technical problem solved by the present invention is to provide a zinc negative electrode protective layer. The zinc negative electrode protective layer provided by the present application has a strong hydrogen evolution inhibition ability, rich zincophilic sites, and high ionic conductivity, can significantly inhibit side reactions and dendrite growth, and achieve an ultra-long-life zinc metal battery.

[0007] In view of this, the present application provides a zinc negative electrode protective layer, which is prepared from a zinc metal oxyacid salt and a polymer.

[0008] Preferably, the zinc metal oxoacid salt has a hollow amorphous structure.

[0009] Preferably, the zinc metal oxoacid salt is selected from one of zinc metatinate, zinc stannate and zinc indate, and the polymer is selected from one or more of polyvinylidene fluoride, acrylic acid-based multi-copolymers and polyvinylidene fluoride-hexafluoropropylene; the mass ratio of the zinc metal oxoacid salt to the polymer is (0.5~2):1.

[0010] The present application also provides a zinc metal negative electrode, which is composed of zinc metal and a zinc negative electrode protective layer composite on the surface of the zinc metal, and the zinc negative electrode protective layer is the above-mentioned zinc negative electrode protective layer.

[0011] Preferably, the thickness of the zinc negative electrode protective layer is 5~50 μm.

[0012] The present application also provides a preparation method of a zinc metal negative electrode, including the following steps:

[0013] Mix the polymer and the organic solvent to obtain a polymer precursor solution;

[0014] Mix the zinc metal oxoacid salt and the polymer precursor solution to obtain a zinc metal negative electrode precursor slurry;

[0015] Coat the zinc metal negative electrode precursor slurry on the surface of the zinc metal, and obtain a zinc metal negative electrode after drying.

[0016] Preferably, the mass fraction of the polymer in the polymer precursor solution is 5~20 wt%, and the mass ratio of the zinc metal oxoacid salt to the polymer is (0.5~2):1.

[0017] Preferably, the drying temperature is 30~100 °C and the time is 5~24 h.

[0018] The present application also provides a zinc metal battery, including a positive electrode, a negative electrode and an electrolyte, and the negative electrode is the above-mentioned zinc metal negative electrode or the zinc metal negative electrode prepared by the above-mentioned preparation method.

[0019] Preferably, the material of the positive electrode is selected from one or more of vanadium pentoxide and manganese dioxide, and the electrolyte is selected from one or more of zinc sulfate aqueous solution and zinc trifluoromethanesulfonate aqueous solution.

[0020] The present application provides a zinc negative electrode protective layer, which is prepared from zinc metal-oxide acid salt and a polymer. Due to the introduction of high hydrogen evolution overpotential metal elements in the zinc metal-oxide acid salt of the zinc negative electrode protective layer provided by the present application, the hydrogen evolution inhibition ability of the protective layer is greatly enhanced; further, the amorphous crystal structure enables the zinc metal-oxide acid salt to provide richer zincophilic sites, which is beneficial to inducing uniform nucleation and precipitation of zinc ions; the hollow structure can significantly shorten the solid-phase transmission distance of zinc ions and accelerate the transmission rate of zinc ions. Therefore, the zinc metal full battery assembled from the zinc negative electrode protective layer has excellent rate performance and long cycle stability. Description of the Drawings

[0021] Figure 1 It is the transmission electron microscope picture of hollow ZnSnO3 in Example 1 of the present invention;

[0022] Figure 2 It is the time-voltage curve of the modified zinc|zinc symmetric battery in Example 1 of the present invention;

[0023] Figure 3 It is the transmission electron microscope picture of solid ZnSnO3 in Example 2 of the present invention;

[0024] Figure 4 It is the capacity-voltage curve of the modified zinc|zinc symmetric battery in Example 2 of the present invention;

[0025] Figure 5 It is the time-voltage curve of the modified zinc|zinc symmetric battery and the unmodified zinc|zinc symmetric battery at different current densities in Example 3 of the present invention;

[0026] Figure 6 It is the charge-discharge curve of the modified zinc|V2O5 full battery in Example 4 of the present invention. Detailed Embodiments

[0027] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0028] Aiming at the problems of side reactions such as dendrite growth, hydrogen evolution and corrosion of the zinc metal negative electrode in the aqueous zinc metal battery in the prior art, the present application provides a zinc negative electrode protective layer. Due to the introduction of the zinc metal-oxide acid salt, the zinc metal negative electrode protective layer provided by the present application has a strong hydrogen evolution inhibition ability; especially, the rich zincophilic sites and high ionic conductivity in the hollow amorphous zinc metal-oxide acid salt can significantly inhibit side reactions and dendrite growth, and a zinc metal battery with an ultra-long life can be obtained. Specifically, the embodiments of the present invention disclose a zinc negative electrode protective layer, which is prepared from zinc metal-oxide acid salt and a polymer.

[0029] In the zinc anode protective layer provided by the present application, the zinc metal oxoacid salt has a hollow amorphous structure and is selected from one of zinc metatinate (ZnSnO3), zinc stannate (Zn2SnO4), and zinc indate (Zn3In2O6). The zinc metal oxoacid salt has the following characteristics: in terms of composition, it contains Zn, O, and high hydrogen evolution overpotential elements (such as Sn, In, or Bi); in terms of crystal structure, it is preferably an amorphous material; in terms of geometric structure, it is preferably a material with a hollow structure. In a specific embodiment, the zinc metal oxoacid salt is selected from hollow amorphous ZnSnO3.

[0030] The present invention has no special limitation on the source of the amorphous hollow ZnSnO3, and it can be prepared according to methods well-known to those skilled in the art. In the present invention, the ZnSnO3 is preferably prepared according to the following method: adding a zinc source and sodium citrate to a solvent, stirring and dissolving it at a certain temperature, then adding a mixed solution of a tin source and an alcohol solvent to the above solution and continuing to stir strongly, and then adding the above solution to NaOH solutions with different concentrations in sequence to obtain a precursor, and finally annealing the precursor in an inert atmosphere for a certain time to obtain ZnSnO3. The preparation of other hollow amorphous zinc metal oxoacid salts is also obtained according to methods well-known to those skilled in the art.

[0031] In the above preparation process, the annealing temperature is 150 - 500 °C, more preferably 450 °C; the annealing time is preferably 1 - 6 h, more preferably 2 h. The zinc source is preferably one or more of zinc acetate, zinc nitrate, and zinc chloride, more preferably zinc chloride; the tin source is one or more of tin nitrate, tin acetate, and tin chloride, more preferably tin chloride; the alcohol solvent is preferably one of methanol or ethanol, more preferably ethanol.

[0032] The high molecular polymer is mainly used for film formation and also has a certain effect of delaying side reactions. It is selected from one of polyvinylidene fluoride (PVDF), acrylic acid-based multi-component copolymers, and polyvinylidene fluoride - hexafluoropropylene (PVDF-HFP).

[0033] The mass ratio of the zinc metal oxoacid salt to the high molecular polymer is (0.5 - 2):1. Specifically, the mass ratio of the zinc metal oxoacid salt to the high molecular polymer is (0.8 - 1.5):1. If the content of the zinc metal oxoacid salt is too large, it can enhance the ability of the film layer to conduct zinc ions, but due to the small content of the high molecular polymer, the mechanical stability of the film layer will be weakened, resulting in a decrease in long-cycle stability; if the content of the zinc metal oxoacid salt is too small and the proportion of the high molecular polymer increases accordingly, the mechanical properties of the film layer can be improved, but the zinc ion conduction rate decreases and the corresponding polarization voltage increases.

[0034] The present application also provides a zinc metal negative electrode, which is composed of zinc metal and a zinc negative electrode protective layer compounded on the surface of the zinc metal, and the zinc negative electrode protective layer is the zinc negative electrode protective layer described in the above solution.

[0035] In the present application, the thickness of the zinc negative electrode protective layer is 5-50 μm. Specifically, the thickness of the zinc negative electrode protective layer is 8-40 μm. If the thickness of the zinc negative electrode protective layer is too thin, its zinc ion conduction ability is enhanced, but its mechanical properties become poor and its ability to inhibit dendrite growth is weakened; if it is too thick, its mechanical properties become strong, but the rate of zinc ion conduction decreases, and concentration polarization is likely to occur, and the polarization voltage increases.

[0036] Furthermore, the present application provides a method for preparing a zinc metal negative electrode, including the following steps:

[0037] Mix a polymer and an organic solvent to obtain a polymer precursor solution;

[0038] Mix a zinc metal oxyacid salt and the polymer precursor solution to obtain a zinc metal negative electrode precursor slurry;

[0039] Coat the zinc metal negative electrode precursor slurry on the surface of the zinc metal, and obtain a zinc negative electrode protective layer after drying.

[0040] During the preparation process of the zinc metal negative electrode, the present application first mixes a polymer and an organic solvent to obtain a polymer precursor solution; during this process, the organic solvent can be selected from solvents that can dissolve the polymer, and specifically can be selected from N-methylpyrrolidone (NMP), acetone or N,N-dimethylformamide (DMF), and more specifically is acetone. The polymer has been described in detail above and will not be elaborated here. The mass fraction of the polymer in the polymer precursor solution is 5-20 wt%, and more specifically is 8-12 wt%.

[0041] The present application then mixes a zinc metal oxyacid salt and the above polymer precursor solution to obtain a zinc metal negative electrode precursor slurry; after obtaining the zinc metal negative electrode precursor slurry, it is coated on the surface of the zinc metal, and a zinc negative electrode protective layer is obtained after drying; the coating method can be carried out in a manner well-known to those skilled in the art, and the present application has no special limitation on this, for example, it can be carried out by doctor blade coating, drop coating or spin coating. The drying is specifically carried out by vacuum drying. The drying time is 5-24 h, specifically, the drying time is 10-18 h.

[0042] Furthermore, the present application provides a zinc metal battery, which specifically applies the above zinc metal negative electrode to the zinc metal battery; specifically, the zinc metal battery includes a negative electrode with a protective layer, a positive electrode and an electrolyte; the negative electrode is the zinc metal negative electrode described in the above solution.

[0043] In the zinc metal battery provided by the present application, the material of the positive electrode is selected from one or more of vanadium pentoxide and manganese dioxide. In the present application, the material of the positive electrode is selected from vanadium pentoxide. The present application has no special limitation on the source of the vanadium pentoxide, and it can be prepared according to the methods well-known to those skilled in the art. In the present invention, the V2O5 is preferably prepared as follows: Add V2O5 and oxalic acid to deionized water, stir at a certain temperature to dissolve to obtain vanadyl oxalate, then add a graphene oxide (GO) dispersion to the above solution, and then freeze-dry the above solution; anneal in an inert atmosphere for a certain time to obtain V2O5@rGO. The electrolyte is selected from one or more of zinc sulfate aqueous solution and zinc trifluoromethanesulfonate aqueous solution.

[0044] The zinc metal full battery provided by the present invention can effectively inhibit the hydrogen evolution side reaction and the corrosion side reaction, promote the uniform deposition of zinc ions, reduce the internal resistance of the battery, and improve the long cycle stability of the battery.

[0045] To further understand the present invention, the following examples are used to describe in detail the zinc negative electrode protection layer, the zinc metal electrode and their preparation methods provided by the present invention. The protection scope of the present invention is not limited by the following examples. Example 1

[0046] Mix 0.1 g of amorphous hollow ZnSnO3 and 1 g of an acrylic acid-based multi-component copolymer precursor solution (mass fraction of 10 wt%) evenly by stirring, and scrape-coat it on the surface of the zinc foil; dry it in a vacuum oven at 60 °C, and cut it after drying to obtain a modified zinc metal electrode with a protection layer.

[0047] Using 2 M ZnSO4 as the electrolyte, assemble the above modified zinc metal electrode into a zinc|zinc button-type symmetric battery. Figure 1 It is a transmission electron microscope picture of hollow ZnSnO3. It can be clearly observed that the ZnSnO3 squares are hollow structures. Figure 2 It is the time-voltage curve of the zinc|zinc symmetric battery at a current density of 2 mA cm -2 As can be seen from the figure, the polarization voltage of the zinc|zinc symmetric battery is 26 mV, and the cycle life exceeds 650 h. Example 2

[0048] Mix 0.1 g of amorphous solid ZnSnO3 and 1 g of an acetone solution of PVDF-HFP (mass fraction of 10 wt%) evenly by stirring, and scrape-coat it on the surface of the zinc foil; dry it in a vacuum oven at 60 °C, and cut it after drying to obtain a modified zinc metal electrode with a protection layer.

[0049] Using 2 M ZnSO4 as the electrolyte, assemble the above modified zinc metal electrode sheet into a zinc|zinc button-type symmetric battery.Figure 3 It is a transmission electron microscope image of solid ZnSnO3. It can be clearly observed that the ZnSnO3 squares are of solid structure. Figure 4 is the voltage-capacity curve of the zinc|zinc battery at a current density of 2 mA cm -2 and a capacity of 2 mAh cm -2 As can be seen from the figure, the polarization voltage of the zinc|zinc battery after stabilization is 35 mV. Example 3

[0050] 0.1 g of amorphous hollow ZnSnO3 and 1 g of an acetone solution of PVDF-HFP (mass fraction 10 wt%) were mixed and stirred evenly, and then scrape-coated onto the surface of the zinc foil; it was dried in a vacuum oven at 60 °C, and after drying, it was cut to obtain a modified zinc metal electrode with a protective layer.

[0051] Using 2 M ZnSO4 as the electrolyte, the above-mentioned modified zinc metal electrode sheet was assembled into a zinc|zinc button-type symmetric battery. Figure 5 is the comparison of the rate performance of the unmodified and modified zinc|zinc symmetric batteries. At a current density of 6.0 mA cm -2 , the overpotentials of the unmodified and modified symmetric batteries are 122 mV and 47 mV respectively. The rate performance of the modified symmetric battery is significantly better than that of the unmodified symmetric battery. Example 4

[0052] 0.7 g of V2O5@rGO, 0.2 g of conductive carbon black and 0.1 g of PVDF binder were mixed, ground and stirred evenly, and then coated onto the stainless steel foil; it was dried in a vacuum oven at 60 °C, and after drying, it was cut to obtain the positive electrode sheet; 0.1 g of amorphous hollow ZnSnO3 and 1 g of an acetone solution of PVDF-HFP (mass fraction 10 wt%) were mixed and stirred evenly, and then scrape-coated onto the surface of the zinc foil; it was dried in a vacuum oven at 60 °C, and after drying, it was cut to obtain a modified zinc metal negative electrode with a protective layer. Using a 3M ZnSO4 saturated V2O5 solution as the electrolyte, a Zn|V2O5 battery was assembled. Figure 6 is the charge-discharge curves of the Zn|V2O5 battery at different current densities. As can be seen from the figure, at current densities of 0.3, 0.5, 1, 3, 5 and 10 A / g, the discharge specific capacities of the modified Zn|V2O5 battery are 375, 319, 293, 275, 261 and 235 mAh g -1 .

[0053] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0054] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A zinc metal negative electrode is composed of zinc metal and a zinc negative electrode protective layer compounded on the surface of the zinc metal. The zinc negative electrode protective layer is prepared from zinc metal oxyacid salt and a polymer. The zinc metal oxyacid salt is selected from one of zinc metatinate, zinc stannate, and zinc indate.

2. The zinc metal negative electrode according to claim 1, wherein The zinc metal oxyacid salt has a hollow amorphous structure.

3. The zinc metal negative electrode according to claim 1 or 2, characterized in that, The polymer is selected from one or more of polyvinylidene fluoride, acrylic acid-based multi-component copolymer, and polyvinylidene fluoride - hexafluoropropylene. The mass ratio of the zinc metal oxyacid salt to the polymer is (0.5 - 2):

1.

4. The zinc metal negative electrode according to claim 1, wherein The thickness of the zinc negative electrode protective layer is 5 - 50 μm.

5. The preparation method of the zinc metal negative electrode according to claim 1, comprising the following steps: Mix the polymer and an organic solvent to obtain a polymer precursor solution. Mix the zinc metal oxyacid salt and the polymer precursor solution to obtain a zinc metal negative electrode precursor slurry. The zinc metal oxyacid salt is selected from one of zinc metatinate, zinc stannate, and zinc indate. Coat the zinc metal negative electrode precursor slurry on the surface of the zinc metal and obtain the zinc metal negative electrode after drying.

6. The preparation method according to claim 5, characterized in that, The mass fraction of the polymer in the polymer precursor solution is 5 - 20 wt%, and the mass ratio of the zinc metal oxyacid salt to the polymer is (0.5 - 2):

1.

7. The preparation method according to claim 6, characterized in that The drying temperature is 30 - 100 °C, and the time is 5 - 24 h.

8. A zinc metal battery, comprising a positive electrode, a negative electrode and an electrolyte, characterized in that, The negative electrode is the zinc metal negative electrode according to any one of claims 1 - 4 or the zinc metal negative electrode prepared by the preparation method according to any one of claims 5 - 7.

9. The zinc metal battery according to claim 8, wherein, The material of the positive electrode is selected from one or more of vanadium pentoxide and manganese dioxide, and the electrolyte is selected from one or more of an aqueous zinc sulfate solution and an aqueous zinc trifluoromethanesulfonate solution.

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