A seawater-based zinc ion battery with a zinc negative electrode interface film having a charge gradient structure

Abstract

The application belongs to the technical field of seawater-based zinc metal batteries, and particularly discloses a seawater-based zinc ion battery with a zinc negative electrode interfacial film with a charge gradient structure. The seawater-based zinc ion battery comprises a seawater-based electrolyte and a zinc metal negative electrode. The seawater-based electrolyte uses natural seawater as a solvent, and the zinc metal negative electrode has an interfacial film with a charge gradient structure, which is prepared by using polycation polysaccharide and polyanion polysaccharide as reactants based on an interfacial electrostatic complexation reaction controlled by diffusion. The charge gradient structure is a negative charge structure gradually enhanced along the zinc ion deposition direction, which can effectively regulate the ion distribution at the zinc negative electrode-electrolyte interface, repel anions with a corrosion effect through electrostatic action, accelerate the diffusion of zinc ions, inhibit the corrosion problem of the zinc metal surface, promote the uniform deposition of zinc ions, and realize effective protection of the zinc metal negative electrode.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of seawater-based zinc metal battery, and more particularly relates to a zinc negative electrode interfacial film with a charge gradient structure and a seawater-based aqueous electrolyte for constructing a seawater zinc ion battery. BACKGROUND

[0002] It is of great significance to integrate renewable energy into grid supply system by advanced energy storage technology for alleviating energy crisis and promoting green and sustainable development. Due to the advantages of high safety, low cost and high energy density, rechargeable aqueous zinc ion battery is a strong candidate for future large-scale stationary energy storage. At present, the aqueous electrolyte is usually prepared by using ultrapure deionized water, which means that the fresh water needs to be further desalted and purified. Natural seawater accounts for ~96.5% of the total water storage on earth, and has high ionic conductivity, making it a potential aqueous electrolyte solvent. With the increasing consumption of fresh water resources, the development of natural seawater as an aqueous electrolyte solvent provides a more sustainable development strategy, which will effectively reduce the cost of the battery, alleviate the growing fresh water crisis, and promote the integration of energy systems in coastal areas with abundant renewable energy (wind power, solar power). However, the chloride ion in seawater system has strong penetration and interfacial adsorption ability, which can easily cause metal pitting and accelerate the corrosion process of zinc metal negative electrode, resulting in reduced coulombic efficiency and cycle life. In addition, complex ion components may interfere with the interfacial deposition of zinc ions, thereby reducing the stability of the zinc metal negative electrode. For example, local pH fluctuations can promote the formation of precipitates or byproducts of complex cations on the zinc metal surface, resulting in increased interfacial resistance and surface inhomogeneity, which will further exacerbate dendrite growth and interfacial parasitic reactions. These strict requirements exclude most of the zinc negative electrode protection strategies used in deionized water electrolyte from seawater system. Therefore, it is urgent to develop more efficient ion modulation strategies to stabilize the zinc metal negative electrode in seawater-based electrolyte. SUMMARY

[0003] In view of the existing technical defects or improvement needs, the present application provides a seawater-based aqueous electrolyte and a zinc metal negative electrode interfacial film with a charge gradient structure for constructing a seawater zinc ion battery. The present application uses natural seawater to replace the commonly used deionized water as a solvent to dissolve electrolyte salt to prepare an aqueous electrolyte. Furthermore, the present application proposes a zinc metal negative electrode interfacial film with a charge gradient structure, which has a negative charge structure gradually increasing along the deposition direction of zinc ions. Further, the interfacial film with a charge gradient structure can effectively repel anions with corrosive properties through electrostatic interaction, while accelerating the diffusion of zinc ions, to achieve excellent effects of inhibiting the corrosion of zinc metal negative electrode in seawater-based electrolyte and promoting uniform deposition.

[0004] To achieve the above object, according to one aspect of the present application, a seawater-based electrolyte is provided, which uses natural seawater to replace deionized water as a solvent to prepare an aqueous electrolyte.

[0005] As a further preferred, the natural seawater is directly taken from the near-shore area, and the taken seawater is simply physically filtered to remove insoluble impurities, and the filtered natural seawater is used as a solvent to dissolve electrolyte salts to prepare an aqueous electrolyte.

[0006] As a further preferred, the electrolyte salt includes one or more of ZnSO4, Zn(CH3COO)2, ZnCl2, Zn(NO3)2, Zn(CF3SO3)2, Zn(TFSI)2, and Zn(BF4)2, and the concentration of the electrolyte salt in the seawater-based electrolyte is 0.5-3.0 mol / L.

[0007] According to another aspect of the present application, an interface film of a zinc metal negative electrode with a charge gradient structure is provided. The charge gradient structure has a negative charge structure gradually enhanced along the direction of zinc ion deposition, which can effectively repel anions with corrosive properties in the seawater-based electrolyte through electrostatic action, while accelerating the diffusion of zinc ions, so as to regulate the ion diffusion behavior of the zinc metal negative electrode-electrolyte interface.

[0008] According to another aspect of the present application, a preparation method of an interface film of a zinc metal negative electrode with a charge gradient structure is provided, which uses a polysaccharide polymer as a precursor, and constructs a charge gradient structure based on a diffusion-controlled interface electrostatic complexation reaction, including the following steps:

[0009] Step 1: coating a low-concentration polyanionic polysaccharide polymer on the surface of a zinc metal negative electrode;

[0010] Step 2: coating a high-concentration polycationic polysaccharide polymer on the zinc metal surface coated with the polyanionic polysaccharide polymer in step 1;

[0011] Step 3: using deionized water to wash away the excess polysaccharide polymer.

[0012] As a further preferred, the polysaccharide polymer precursor includes one or more of polycationic polysaccharide (chitosan) and polyanionic polysaccharide (sodium alginate, xanthan gum, k-carrageenan, sodium carboxymethyl cellulose).

[0013] As a further preferred, the concentration of the low-concentration polyanionic polysaccharide solution is 0.5 wt%-5.0 wt%, and the concentration of the high-concentration polycationic polysaccharide solution is 30 wt%-60 wt%.

[0014] As a further preferred, the electrostatic complexation reaction time of the polyanionic polysaccharide solution and the polycationic polysaccharide solution is 5 s-300 s.

[0015] Overall, the above technical solutions conceived by the present application have the following technical advantages compared with the existing technology.

[0016] 1. The seawater-based electrolyte described in the present application is prepared using natural seawater instead of deionized water. The use of seawater-based electrolyte can significantly reduce the assembly cost of the battery and alleviate the pressure of freshwater consumption. Furthermore, coastal areas have abundant renewable resources, such as offshore wind energy, solar energy, wave energy, etc. The development of seawater-based electrolyte is conducive to promoting the sustainable development of coastal fixed energy storage devices and promoting the integration of coastal energy systems, thus showing great economic and environmental benefits.

[0017] 2. The preparation of the interface film of the zinc metal anode with a charge gradient structure described in the present application uses polysaccharide polymers as precursors. Furthermore, these polysaccharide polymer precursors can come from renewable marine biomass, such as crab shells, seaweed, etc., showing the advantages of low cost and environmental friendliness. Furthermore, the preparation of the interface film of the zinc metal anode with a charge gradient structure is based on a diffusion-controlled electrostatic complexation reaction, which can be completed instantaneously in an open air atmosphere. Therefore, the synthesis process is simple, environmentally friendly, and meets the requirements of sustainable development and large-scale promotion.

[0018] 3. The zinc metal anode interface film described in the present application has a negative charge structure that gradually increases along the direction of zinc ion deposition. It can effectively repel anions with corrosive properties through electrostatic interaction, while accelerating the diffusion of zinc ions. It has the dual advantages of inhibiting the corrosion of zinc metal anode in seawater-based electrolyte and promoting uniform deposition. Therefore, the use of the zinc metal anode interface film provided by the present application can ensure the long-term cycle stability and safety of seawater zinc ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The cross-sectional scanning electron microscope image (a) and the X-ray photoelectron spectroscopy (b) of the interface modification film of the zinc metal anode with a charge gradient structure in Example 1.

[0020] Figure 2 The X-ray diffraction patterns of the zinc electrode of the Zn / / Zn symmetric battery assembled using the zinc electrode in Comparative Example 2 (a) and Example 1 (b) after short circuiting and after 100 cycles.

[0021] Figure 3Scanning electron microscope images of zinc electrodes after shorting and after 100 cycles for Zn / / Zn symmetric cells assembled using zinc electrodes in Comparative Example 2 (a figure) and Example 1 (b figure).

[0022] Figure 4 Time-voltage curves under test conditions for Zn / / Zn symmetric cells assembled using zinc electrodes in Example 1, Comparative Example 1 and Comparative Example 2 at 1 mA cm -2 and 1 mAh cm -2 .

[0023] Figure 5 Time-voltage curves under test conditions for Zn / / Zn symmetric cells assembled using zinc electrodes in Example 1 and Comparative Example 2 at 5 mA cm -2 and 2.5 mAh cm -2 .

[0024] Figure 6 Charge gradient structure regulates the mechanism of ions, schematic diagram. DETAILED DESCRIPTION

[0025] In order to express the purpose, technical scheme and advantages of the present application more clearly, the present application will be further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific examples described herein are merely intended to explain the present application, but not to limit the present application. Obviously, the described examples are only a part of the embodiments of the present application, but not all the embodiments. Based on the examples in the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0026] The raw materials and reagents used in the present embodiment can be obtained from commercial channels or prepared by known methods.

[0027] Example 1

[0028] 1. Preparation of seawater-based electrolyte

[0029] The preparation method of the seawater-based electrolyte in the present embodiment comprises the following steps:

[0030] Step 1: The natural seawater taken from the offshore area is physically filtered to filter out insoluble impurities for standby use.

[0031] Step 2: ZnS04·7H20 is dissolved in the natural seawater obtained in Step 1 to configure a 2 mol / L ZnS04 electrolyte (labeled as NS electrolyte).

[0032] 2. Preparation of zinc metal anode interface film with charge gradient structure

[0033] The method for preparing the interface film of the zinc metal anode with a charge gradient structure in this embodiment includes the following steps:

[0034] Step 1: Chitosan and sodium alginate are dissolved in deionized water at room temperature to prepare homogeneous solutions with concentrations of 40 wt% and 1 wt%, respectively.

[0035] Step 2: Coat the zinc foil surface evenly with a 1 wt% sodium alginate solution;

[0036] Step 3: Add a 40 wt% chitosan solution dropwise onto the zinc foil surface loaded with sodium alginate solution obtained in Step 2;

[0037] Step 4: After the electrostatic complexation reaction has lasted for 10 seconds, rinse off the excess chitosan and sodium alginate solution with deionized water to obtain a zinc metal anode modified with a charge gradient structure interface film (labeled as CGI-Zn).

[0038] Example 2

[0039] This embodiment is a parallel experiment similar to that of Example 1, except that sodium alginate is replaced with xanthan gum, and the other preparation methods are exactly the same as those in Example 1, to obtain a zinc metal anode interface film with a charge gradient structure.

[0040] Example 3

[0041] This embodiment is a parallel experiment similar to that of Example 1, except that sodium alginate is replaced with sodium carboxymethyl cellulose, and the other preparation methods are exactly the same as those in Example 1, to obtain a zinc metal anode interface film with a charge gradient structure.

[0042] Example 4

[0043] This embodiment is a parallel experiment similar to that of Example 1, except that sodium alginate is replaced with k-carrageenan, and the other preparation methods are exactly the same as those in Example 1, to obtain a zinc metal anode interface film with a charge gradient structure.

[0044] Comparative Example 1

[0045] This comparative example was conducted in parallel with Example 1.

[0046] 1. Preparation of seawater-based electrolyte

[0047] The preparation method of the seawater-based electrolyte is the same as that in Example 1.

[0048] 2. Preparation of the interface of a zinc metal anode with opposite charge gradient structure

[0049] The method for preparing the interface film of the zinc metal anode with the opposite charge gradient structure in this embodiment includes the following steps:

[0050] Step 1: Chitosan and sodium alginate were respectively dissolved in deionized water at room temperature to prepare uniform solutions with concentrations of 40 wt% and 1 wt%;

[0051] Step 2: The 1 wt% sodium alginate solution was uniformly coated on the surface of the zinc foil;

[0052] Step 3: The 40 wt% chitosan solution was added dropwise to the surface of the zinc foil loaded with the sodium alginate solution obtained in Step 2;

[0053] Step 4: After the electrostatic complexation reaction lasted for 10 s, the excess chitosan and sodium alginate solution was washed away with deionized water;

[0054] Step 5: The interface film of the zinc metal anode with the charge gradient structure obtained in Step 4 was reversed and the surface of the zinc foil was placed to obtain the zinc metal anode with the interface film modified with the opposite charge gradient structure (labeled as ICGI-Zn).

[0055] Comparative Example 2

[0056] This comparative example was a parallel experiment similar to Example 1, in which the seawater-based electrolyte was prepared in the same way as in Example 1, but the surface of the zinc foil was not modified with the interface film (labeled as Pure-Zn).

[0057] Comparative Example 3

[0058] This comparative example was a parallel experiment similar to Example 1.

[0059] 1. Preparation of seawater-based electrolyte

[0060] The method for preparing the seawater-based electrolyte was the same as in Example 1.

[0061] 2. Preparation of the interface of the zinc metal anode with the charge gradient structure

[0062] The method for preparing the interface film of the zinc metal anode with the charge gradient structure in this embodiment includes the following steps:

[0063] Step 1: Chitosan and sodium alginate were respectively dissolved in deionized water at room temperature to prepare uniform solutions with concentrations of 40 wt% and 1.0 wt%;

[0064] Step 2: The 1.0 wt% sodium alginate solution was uniformly coated on the surface of the zinc foil;

[0065] Step 3: A 40 wt% concentration of chitosan solution was dropped onto the zinc foil surface loaded with sodium alginate solution obtained from step 2;

[0066] Step 4: After the electrostatic complexation reaction lasted for 100 s, the excess chitosan and sodium alginate solution were rinsed off with deionized water. A zinc metal anode with interface film modification of charge gradient structure was obtained.

[0067] Comparative Example 4

[0068] This comparative example is a parallel experiment similar to Example 1.

[0069] 1. Preparation of seawater-based electrolyte

[0070] The preparation method of the seawater-based electrolyte is the same as that of Example 1.

[0071] 2. Preparation of interface of zinc metal anode with charge gradient structure

[0072] The preparation method of the interface film of the zinc metal anode with charge gradient structure in this example includes the following steps:

[0073] Step 1: Chitosan and sodium alginate were respectively dissolved in deionized water at room temperature to prepare uniform solutions with concentrations of 30 wt% and 1.5 wt%;

[0074] Step 2: A 1.5 wt% concentration of sodium alginate solution was uniformly coated on the surface of zinc foil;

[0075] Step 3: A 30 wt% concentration of chitosan solution was dropped onto the zinc foil surface loaded with sodium alginate solution obtained from step 2;

[0076] Step 4: After the electrostatic complexation reaction lasted for 10 s, the excess chitosan and sodium alginate solution were rinsed off with deionized water. A zinc metal anode with interface film modification of charge gradient structure was obtained.

[0077] Material characterization and electrochemical performance test

[0078] Figure 1 a is a cross-sectional scanning electron microscope image of the interface film of the zinc metal anode with charge gradient structure described in Example 1, and the prepared interface modification film shows a smooth micro-morphology with a thickness of about 2 μm. Figure 1 b is an X-ray photoelectron spectrum of the interface film of the zinc metal anode with charge gradient structure described in Example 1, where the N element comes from the amino functional group (-NH2 +), the zinc surface side (2.46 wt%) of the prepared interfacial modification film was lower than the side far from the zinc surface (4.35 wt%), proving that the diffusion behavior of chitosan in the static complexation reaction made it present a gradient distribution in the prepared interfacial modification film. Due to the ionization of functional groups, the chitosan and sodium alginate used in Example 1 were positively and negatively charged, respectively, which means that the gradient distribution of chitosan in the interfacial modification film made the interfacial modification film have a charge gradient structure. Zeta potential test showed that the potential of the side of the interfacial modification film close to the zinc surface and the side far from the zinc surface was -9.43 mV and -5.34 mV, respectively.

[0079] In the present application, the test of the electrochemical performance of the zinc metal negative electrode is carried out using a CR2032 button cell, and the test condition is 25 o C. The preparation of the zinc metal negative electrode is to cut the commercial zinc foil (purity > 99.99%, thickness 100 μm) into a round piece, and then clean it with alcohol. The separator is a commercial glass fiber. The Zn / / Zn symmetric cell is assembled using the seawater-based electrolyte prepared in Example 1, and the amount of the seawater-based electrolyte is 80 μL. The Zn / / Zn symmetric cell is assembled using the zinc metal negative electrode in Example 1, Comparative Example 1 and Comparative Example 2, and the cycle performance is tested under the condition that the current density is 1 mA cm -2 , and the deposition capacity is 1 mAh cm -2 . As shown in Figure 2 , the symmetric cell using the IGC-Zn electrode can be stably cycled for 1300 h, which is much greater than the symmetric cells using the IGC I-Zn and Pure Zn electrodes. Figure 3 It is shown that under extreme conditions (current density of 5 mA cm -2 , deposition capacity of 2.5 mAh cm -2The cycle performance of the symmetric cell with the IGC-Zn electrode was much better than that of the symmetric cell with the Pure-Zn electrode. The symmetric cell with the Pure-Zn electrode could only cycle for 5 h, while the symmetric cell with the IGC-Zn electrode could cycle for 200 h, which proved that the interface modification film with the charge gradient structure had good stability for the zinc metal. Failure analysis was performed on the Zn / / Zn symmetric cell with the Pure-Zn electrode. Without the protection of the interface modification film, the Pure-Zn electrode had serious dendrite growth, which led to the rapid short circuit of the cell. In contrast, the surface of the IGC-Zn electrode remained smooth and dendrite-free after 100 cycles. In addition, the X-ray diffraction test results showed that obvious by-products NaZn4(SO4)Cl(OH)6·6H2O (NZSCO) and Zn4SO4(OH)6·xH2O (ZSO) were detected on the surface of the Pure-Zn electrode after the short circuit. Benefiting from the repulsion of the interface modification film with the charge gradient structure to anions, similar by-products were not detected on the surface of the IGC-Zn electrode. The interface modification film with the charge gradient structure of the zinc metal negative electrode could repel anions through electrostatic interaction, while accelerating the diffusion of zinc ions, so as to inhibit the occurrence of dendrite growth and surface parasitic reactions, and effectively stabilize the zinc metal negative electrode in the seawater-based electrolyte.

[0080] Those skilled in the art will easily understand that the above description is only preferred embodiments of the present application, and the present application is not limited to the above embodiments. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A zinc-ion battery comprising a seawater-based aqueous electrolyte and a zinc metal anode, the seawater-based aqueous electrolyte comprising a natural seawater solvent and an electrolyte salt, the natural seawater being subjected to a simple physical filtration to remove insoluble impurities before use, the electrolyte salt comprising one or more of ZnSO4, Zn(CH3COO)2, ZnCl2, Zn(NO3)2, Zn(CF3SO3)2, Zn(TFSI)2, and Zn(BF4)2, the electrolyte salt having a concentration of 0.5-3.0 mol / L in the seawater-based electrolyte, the zinc metal anode having an interface film with a charge gradient structure, the interface film being prepared by the following steps: Step 1: preparing a low-concentration polyanionic polysaccharide solution and a high-concentration polycationic polysaccharide solution using deionized water as a solvent at room temperature; Step 2: uniformly coating the low-concentration polyanionic polysaccharide solution on the surface of a zinc foil; Step 3: dropwise adding the high-concentration polycationic polysaccharide solution to the zinc foil loaded with the low-concentration polyanionic polysaccharide solution obtained in Step 2; Step 4: after the reaction, rinsing off the excess polyanionic and polycationic polysaccharide solutions with deionized water; the polyanionic polysaccharide comprising one or more of sodium alginate, xanthan gum, k-carrageenan, and sodium carboxymethyl cellulose, the polycationic polysaccharide comprising chitosan, the low-concentration polyanionic polysaccharide solution having a concentration of 0.5 wt%-5.0 wt%, the high-concentration polycationic polysaccharide solution having a concentration of 30 wt%-60 wt%, and the reaction time of the polyanionic polysaccharide solution and the polycationic polysaccharide solution in Step 4 being 5 s-300 s.

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