Preparation method and application of copper phosphate for inhibiting growth of zinc dendrites

Abstract

The invention relates to the field of aqueous zinc ion batteries, in particular to a preparation method and application of copper phosphate for inhibiting zinc dendritic crystal growth, which adopts a hydrothermal reaction method to construct a copper phosphate (CP) protective layer on the surface of a zinc anode in situ, so that more zinc-loving sites are provided, Zn < 2 + > is uniformly deposited on the anode, and the zinc dendritic crystal growth is inhibited. The Cu3 (PO4) 2 cathode prepared by the method has the advantages that the'point effect 'caused by non-uniform deposition of Zn < 2 + > is effectively reduced, the hydrophobicity of the anode side is improved, the direct contact between water and zinc in electrolyte is reduced, the hydrogen evolution and the formation of a by-product Zn4 (OH) 6SO4. XH2O are effectively reduced, and the prepared Cu3 (PO4) 2 cathode has the service life of 2000 hours compared with a pure zinc cathode (110 hours) in the test of an assembled symmetrical battery, and has the advantages of high efficiency, high safety and the like. And compared with a pure zinc negative electrode (38.69%), the total battery assembled with the MnO2 negative electrode has higher capacity retention rate (more than 66%) and longer service life (more than 3000 weeks).

Description

Technical Field

[0001] The invention relates to an aqueous zinc ion battery negative electrode material, a preparation method and a zinc ion battery, and belongs to the technical field of electrochemical energy. Background Art

[0002] In recent years, with the consumption of fossil energy and the improvement of people's environmental awareness, clean energy has gradually become a hot topic of research. Lithium-ion batteries are expensive and unfriendly to the environment, so people are eager to find alternative batteries. Aqueous batteries have gradually attracted people's attention due to their low cost and high safety. Zn is abundant in the earth, aqueous zinc-ion batteries are good for the environment, and zinc-based batteries have a high theoretical capacity (820 Ah kg -1 ) has attracted widespread interest. However, due to the irregular deposition and stripping of zinc anode during battery charging and discharging, a series of side reactions such as zinc dendrite growth, electrode corrosion and hydrogen evolution lead to the attenuation of battery capacity and the reduction of service life. Therefore, reducing the occurrence of dendrites and side reactions is a crucial factor for the large-scale application of zinc-ion batteries.

[0003] At present, there have been many studies on zinc electrode modification, zinc electrode structure, electrolyte and diaphragm modification to inhibit a series of side reactions such as dendrite growth. When Zn is electroplated on 3D copper foam to form a copper-zinc alloy, the contact area with the electrolyte is increased, thereby reducing the impact of dendrites. The zinc-philic metal elements Cu, Sn, Bi, Sb, etc. are used to form alloys to provide more zinc-philic sites to achieve uniform deposition.

[0004] Interface modification is also an effective method to inhibit side reactions and reduce dendrite growth. For example, a layer of dense NaZnPO4 is deposited on the zinc surface to isolate it from direct contact with the electrolyte, which effectively reduces the occurrence of side reactions. However, most of the current interface reactions are relatively cumbersome and complicated, so a simple method is an important condition for realizing application. Summary of the invention

[0005] The main purpose of the present invention is to provide an anode material for an aqueous zinc ion battery, thereby reducing the side reactions of hydrogen evolution, corrosion and dendrite growth, and effectively alleviating the problem of volume expansion during the cycle, thereby greatly improving the cycle stability of the battery and making up for the shortcomings of the prior art.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: S1: Weigh copper salt, phosphate and urea respectively, mix with deionized water, and stir evenly at room temperature.

[0007] S2: The zinc sheet was polished and placed in a polytetrafluoroethylene-lined reactor with the solution in S1 and kept at 100-160°C for 1-12 h. After being taken out and ultrasonicated for 5 min, the final product was dried with deionized water.

[0008] The Cu3(PO4)2 obtained in the present invention has zinc-philic sites and can reduce side reactions on the negative electrode side. The present invention also provides a symmetrical battery, comprising a symmetrical battery assembled using the copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method as both the positive and negative pole pieces of a button battery.

[0009] The present invention also provides a half-cell, comprising a half-cell assembled with the copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method as a negative electrode sheet and copper foil as a positive electrode sheet.

[0010] The present invention also provides an aqueous MnO2 button battery, comprising an aqueous MnO2 button battery assembled using the copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method as an anode.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects: The invention uses low-cost raw materials, adopts a one-step hydrothermal method, and is easy to operate.

[0012] The Cu3(PO4)2 anode of the present invention provides abundant zinc-philic sites by introducing insoluble hydrophobic copper phosphate into the surface of the zinc electrode, so that Zn 2+ Uniform deposition reduces the formation of zinc dendrites, allowing the assembled symmetrical battery to have a cycle life of 2000 h.

[0013] The Cu3(PO4)2 anode of the present invention reduces the direct contact between the electrolyte and the zinc sheet through its strong hydrophobicity, effectively reduces hydrogen evolution and the formation of Zn4(OH)6SO4·xH2O by-products, so that the full battery assembled with MnO2 has a capacity retention rate of more than 66% and a stable cycle of more than 3000 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the X-ray diffraction pattern of Cu3(PO4)2@Zn prepared in Example 1.

[0015] Figure 2 This is a scanning electron microscope image of Cu3(PO4)2@Zn prepared in Example 1.

[0016] Figure 3 When the Cu3(PO4)2@Zn prepared in Example 1 is used as the negative electrode of an aqueous zinc ion battery, the current density is 1 mA / cm 2, with a surface capacity of 0.25 mAh / cm 2 Below is the charge and discharge performance curve of a symmetrical battery.

[0017] Figure 4 When the Cu3(PO4)2@Zn prepared in Example 1 is used as the negative electrode of the aqueous zinc ion battery, the current density is 5 mA / cm 2 , with an area capacity of 1 mAh / cm 2 Below is the charge and discharge performance curve of a symmetrical battery.

[0018] Figure 5 The half-cell assembled with Cu3(PO4)2@Zn prepared in Example 1 as the negative electrode material and Cu foil as the positive electrode material was operated at a current density of 2 mA / cm 2 , with a surface capacity of 0.5 mAh / cm 2 Coulomb efficiency diagram below.

[0019] Figure 6 The charge and discharge performance curve of a full battery assembled with Cu3(PO4)2@Zn prepared in Example 1 as the negative electrode material and MnO2 as the positive electrode at a current density of 1 A / g.

[0020] Figure 7 The charge and discharge performance curve of a full battery assembled with Cu3(PO4)2@Zn prepared in Example 1 as the negative electrode material and MnO2 as the positive electrode at a current density of 2 A / g. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0023] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0024] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0025] Example 1 The preparation process of the copper phosphate coating for inhibiting zinc dendrite growth of the present invention comprises the following steps: (1) Copper nitrate hexahydrate, ammonium dihydrogen phosphate, and urea in a molar ratio of 3:2:(8-10) were dissolved in deionized water and stirred at room temperature for 12 h.

[0026] (2) A 0.1 mm thick zinc sheet was polished and ultrasonicated for 5 min, and then placed together with the solution in (1) in a polytetrafluoroethylene-lined reactor and kept at 120°C for 6 min. The sheet was taken out, ultrasonicated for 5 min, rinsed with deionized water, and dried to obtain a surface-grown copper zinc phosphate sheet.

[0027] The Cu3(PO4)2@Zn prepared in this example is denoted as CP@Zn and used as the positive and negative electrodes of a button battery. A glass fiber separator and 2 mol / L ZnSO4 are used as the electrolyte. The button battery is assembled under normal conditions and is denoted as a CP@Zn / / CP@Zn symmetric battery.

[0028] The Cu3(PO4)2@Zn prepared in this example is denoted as CP@Zn and used as the negative electrode of a button cell. Copper foil is used as the positive electrode. A glass fiber separator is used. 2 mol / L ZnSO4 is used as the electrolyte. The button cell is assembled under normal conditions and denoted as a CP@Zn / / Cu half-cell.

[0029] The Cu3(PO4)2@Zn prepared in this example is denoted as CP@Zn and used as the negative electrode of a button cell. MnO2 is used as the positive electrode. A glass fiber separator and 2 mol / L ZnSO4 are used as the electrolyte. The button cell is assembled under normal conditions and is denoted as a CP / / MnO2 full cell.

[0030] Comparative Example 1 Zinc foil is used as the positive and negative electrodes of the button battery, a glass fiber separator is used, and 2 mol / L ZnSO4 is used as the electrolyte. The button battery is assembled under normal conditions and is recorded as a Zn / / Zn symmetric battery.

[0031] Zinc foil is used as the negative electrode of the button battery, copper foil is used as the positive electrode, a glass fiber separator is used, and 2 mol / L ZnSO4 is used as the electrolyte. The button battery is assembled under normal conditions and is denoted as a Zn / / Cu half-cell.

[0032] Zinc foil is used as the negative electrode of the button battery, MnO2 is used as the positive electrode, a glass fiber separator is used, and 2 mol / L ZnSO4 is used as the electrolyte. The button battery is assembled under normal conditions and is denoted as a Zn / / MnO2 full battery.

[0033] The copper phosphate coating was subjected to X-ray diffraction analysis, scanning electron microscopy analysis, symmetrical battery cycle life test, half-cell coulomb efficiency test, full battery life and retention rate test, and the results are as follows: Figure 1-Figure 7 shown.

[0034] Figure 1 Shown is the X-ray diffraction of the Cu3(PO4)2@Zn sample prepared in Example 1. From the figure, it can be seen that the diffraction peaks of copper phosphate and Zn can be well observed, indicating that the copper phosphate-encapsulated zinc sample has been successfully prepared. Figure 2 This is a scanning electron microscope image of the sample. In the image, copper phosphate crystals with an average particle size of 0.5-1 micron are evenly distributed on the surface of the zinc foil.

[0035] Figure 3 and Figure 4 The symmetrical battery constant current charge and discharge test diagrams of the symmetrical battery assembled in Example 1 and Comparative Example 1 at low current and high current density are shown respectively. Figure 3 It can be seen that the symmetrical battery has a current density of 1 mA / cm 2 , with a surface capacity of 0.25 mAh / cm 2 Under the conditions of CP@Zn, the overpotential of CP@Zn is significantly smaller than that of the symmetric battery with pure Zn electrode, indicating that the presence of copper phosphate coating reduces the nucleation barrier of Zn and also reduces polarization, promoting a relatively uniform zinc deposition / dissolution process, so that the symmetric battery with copper phosphate coating has a cycle life of 2000 h compared with the 113 h of the pure zinc symmetric battery. Figure 4 5 mA / cm 2 The high current density of 1 mAh / cm 2 This rule also applies to surface capacity, and the battery has a longer cycle life than pure Zn electrode, indicating that the presence of copper phosphate can effectively reduce the occurrence of side reactions and thus extend battery life.

[0036] Figure 5 The half-cell assembled with Example 1 and Comparative Example 1 as the negative electrode of the button battery and Cu foil as the positive electrode of the button battery at 2 mA / cm 2Coulomb efficiency tested under current density. It can be seen from the figure that the coulomb efficiency of the pure Zn electrode fluctuates greatly after 200 cycles due to a series of side reactions, resulting in battery damage. However, the half-cell of the copper phosphate coating prepared in Example 1 can still maintain a coulomb efficiency of 99.8% after 1800 cycles due to the excellent ability of copper phosphate to inhibit side reactions, which is significantly better than that of Comparative Example 1.

[0037] Figure 6 and Figure 7 The figures are the charge and discharge test diagrams of the full battery assembled with Example 1 and Comparative Example 1 as the negative electrode sheets of the button battery and MnO2 as the positive electrode sheet of the button battery at different current densities. Figure 6 This is a charge and discharge test diagram at a current density of 1 A / g. From the figure, it can be seen that the initial capacity of the Zn / / MnO2 battery is 155 mAh / g, which decays to 60 mAh / g after 700 cycles, and the capacity retention rate is only 38.69%. The CP / / MnO2 full battery in Example 1 reduces the occurrence of side reactions, so that the battery still has a capacity retention rate of 66.04% after 700 cycles. Figure 7 The figure is a charge and discharge test diagram at a current density of 2 A / g. It can be seen from the figure that after 2250 cycles, the Zn / / MnO2 battery failed due to a series of side reactions that caused dendrites to pierce the diaphragm, resulting in only 45.89% capacity retention. The CP / / MnO2 battery prepared in Example 1 can stably cycle 3000 times and maintain a retention rate of 60.61%, which is significantly better than Comparative Example 1 because of the suppression of side reactions.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for a person skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions claimed to be protected by the present invention.

Claims

1. A method for preparing copper phosphate for inhibiting zinc dendrite growth, characterized in that: The steps include: S1: Weigh copper salt, phosphate and urea respectively, mix them together and stir at room temperature; S2: The zinc sheet and the solution in S1 are placed in a polytetrafluoroethylene-lined reactor for solvent thermal treatment, and then washed with water and dried after ultrasonic treatment to obtain a zinc sheet with copper phosphate grown on the surface.

2. The method for preparing copper phosphate for inhibiting zinc dendrite growth according to claim 1, characterized in that: The copper salt used is one of copper acetate, copper nitrate, copper sulfate and copper chloride.

3. The method for preparing copper phosphate for inhibiting zinc dendrite growth according to claim 1, characterized in that: The phosphate used is one of ammonium phosphate, diammonium phosphate and dipotassium hydrogen phosphate.

4. The method for preparing copper phosphate for inhibiting zinc dendrite growth according to claim 1, characterized in that: The heating rate in S2 is 3-10°C / min, the temperature is raised to 100-160°C, and the temperature is kept for 1-12 hours.

5. The method for preparing copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The obtained Cu3(PO4)2 has zinc-philic sites, which can reduce side reactions on the negative electrode side.

6. A symmetrical battery, characterized in that: A symmetrical battery is assembled using copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method described in any one of claims 1 to 4 as both positive and negative pole pieces of a button battery.

7. A half-cell, characterized in that: The invention comprises a half-cell assembled by using copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method according to any one of claims 1 to 4 as a negative electrode sheet and copper foil as a positive electrode sheet.

8. Aqueous MnO2 button cell, characterized in that: The invention comprises an aqueous MnO2 button battery assembled with copper phosphate for inhibiting zinc dendrite growth prepared by the preparation method according to any one of claims 1 to 4 as an anode.

Images