A material for suppressing zinc dendrites, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a material for inhibiting zinc dendrites, a preparation method thereof, and an application. The chemical formula of the material is MFe5O8, where M is one or more of Li, Na, and K elements. When the material is ground and mixed evenly with carbon, a binder, and an organic solvent and then coated on the surface of a zinc sheet or a zinc alloy sheet, it can be used as a coating material for inhibiting the growth, corrosion, and hydrogen evolution of zinc dendrites. When the material is mixed evenly with zinc powder or zinc alloy powder, a conductive agent, and a binder and then made into a thin film electrode, it can be used as an additive for inhibiting the growth, corrosion, and hydrogen evolution of zinc dendrites. Through the present invention, whether it is used as a coating to modify a zinc sheet or as an additive to modify zinc powder, the growth of zinc dendrites can be effectively inhibited. In particular, it can be used as a negative electrode material in aqueous zinc-based batteries to exert its performance of inhibiting the growth of zinc dendrites and ensure the long-term cycle of aqueous zinc-based batteries.

Description

Technical Field

[0001] The present invention belongs to the field of aqueous zinc-based batteries, and more specifically, relates to a material for inhibiting the growth of zinc dendrites and its application. Background Art

[0002] Due to the advantages of low cost, good conductivity, stable properties, safety and non-toxicity, and high theoretical capacity (819 mAh g -1 ), metallic zinc (Zn) is widely used as the negative electrode material for aqueous zinc-based batteries. However, during the long-term dissolution-deposition process, the surface morphology of zinc changes, and dendrites are easily formed, piercing the battery separator and causing short circuits in the battery, thereby reducing the cycle life of the battery. Therefore, developing effective methods and technologies to inhibit the growth of zinc dendrites is the key to the practical application of aqueous zinc-based batteries. Currently reported methods, such as designing three-dimensional foamy zinc, artificially constructing a SEI film, using a high-concentration electrolyte, designing zinc with a specific orientation, etc., show certain effects in inhibiting the formation and growth of zinc dendrites. However, most of these preparation methods face problems such as cumbersome manufacturing processes, high costs, and difficulty in large-scale production. Therefore, developing more practical and effective methods remains a challenge. Summary of the Invention

[0003] Aiming at the problems of high cost and complex process in the existing methods for inhibiting zinc dendrites, the purpose of the present invention is to provide a material for inhibiting zinc dendrites and its application. By coating technology, this material is modified on the surface of zinc sheets or zinc alloys, or used as an additive and added to zinc powder or zinc alloy powder, which can all inhibit the dendrite growth, corrosion, and hydrogen evolution reaction of the zinc negative electrode, thereby effectively improving the cycle performance of the zinc negative electrode.

[0004] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0005] A material for inhibiting zinc dendrites, with the chemical formula MFe5O8, where M is one or more of the elements Li, Na, and K.

[0006] Preferably, the material for inhibiting zinc dendrites in the present invention has the chemical formula LiFe5O8.

[0007] A preparation method of a material for inhibiting zinc dendrites, wherein M2CO3 or M2O and Fe2O3 are uniformly mixed in a molar ratio of 1:5, and then solid-phase sintered in air at 500 - 800 °C to prepare MFe5O8, where M is one or more of the elements Li, Na, and K.

[0008] A coating manufacturing method for inhibiting zinc dendrites, wherein the above-mentioned material for inhibiting zinc dendrites is ground and mixed uniformly with carbon, a binder, and an organic solvent, and then coated on the surface of zinc sheets or zinc alloy sheets.

[0009] A method for manufacturing a coating for suppressing zinc dendrites, wherein the material for suppressing zinc dendrites is modified onto the surface of a zinc sheet or a zinc alloy sheet by spraying, printing, electroplating or sputtering.

[0010] Preferably, in the method for manufacturing a coating for suppressing zinc dendrites of the present invention, the coating thickness does not exceed 20 μm.

[0011] A method for manufacturing an electrode for suppressing zinc dendrites, wherein the material for suppressing zinc dendrites is uniformly mixed with zinc powder or zinc alloy powder, a conductive agent and a binder to form a thin film electrode.

[0012] Preferably, in the method for manufacturing an electrode for suppressing zinc dendrites of the present invention, the mass fraction of the material for suppressing zinc dendrites does not exceed 30 wt%.

[0013] A negative electrode using the above-mentioned material for suppressing zinc dendrites.

[0014] An aqueous zinc-based battery using the above-mentioned negative electrode.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. LiFe5O8 has certain magnetism. Under the action of an electric field, a local magnetic field can be generated, which helps to regulate the current distribution. When zinc is deposited on a zinc sheet modified with a LiFe5O8 layer at a constant current density, the magnetic LiFe5O8 can induce uniform deposition of zinc atoms on its surface, reduce the aggregation of zinc on the surface, and thus inhibit the growth of dendrites.

[0017] 2. LiFe5O8 has a high hydrogen evolution overpotential. When it is used as a coating to modify the surface of a zinc sheet or added as an additive to zinc powder, it can inhibit the hydrogen evolution side reaction of zinc, thereby reducing the side reaction of gas generation on the zinc surface and improving the Coulombic efficiency of the electrode.

[0018] 3. LiFe5O8 is resistant to acid and alkali corrosion. When it is used as a coating to modify the surface of a zinc sheet or added as an additive to zinc powder, it can inhibit the corrosion reaction of zinc, thereby reducing the self-discharge on the zinc surface and improving the Coulombic efficiency of the electrode.

[0019] 4. The electrochemical performance of LiFe5O8 is stable. Within the aqueous solution window, the electrochemical performance of LiFe5O8 is stable and no reduction reaction will occur.

[0020] 5. The LiFe5O8 material is inexpensive, environmentally friendly, non-toxic and easy to prepare. The preparation method of the material obtained in the present invention is simple. After uniformly mixing Li2CO3 or Li2O with Fe2O3 in a molar ratio of 1:5, it can be prepared by solid-phase sintering in air at 500 - 800 °C. The main raw material of this material is Fe2O3, which has a wide source, low cost, is green and environmentally friendly, and is safe and harmless. It is a material with very promising application potential. Brief Description of the Drawings

[0021] The technical solutions of the present application will be further described below in conjunction with the drawings and embodiments.

[0022] Figure 1 It is a cross-sectional SEM photograph of the zinc sheet electrode modified with LiFe5O8 prepared in Example 1 of the present invention;

[0023] Figure 2 It is an LSV curve graph of the zinc sheet electrode modified with LiFe5O8 prepared in Example 1 of the present invention;

[0024] Figure 3 It is a Tafel curve graph of the zinc sheet electrode modified with LiFe5O8 prepared in Example 1 of the present invention;

[0025] Figure 4 It is a charge-discharge curve graph of the zinc sheet electrode modified with LiFe5O8 and the pure zinc electrode prepared in Example 1 of the present invention in a symmetric battery;

[0026] Figure 5 It is a SEM photograph of the zinc sheet electrode modified with LiFe5O8 and the pure zinc electrode prepared in Example 1 of the present invention after cycling in a symmetric battery;

[0027] Figure 6 It is a cross-sectional SEM photograph of the zinc sheet electrode modified with LiFe5O8 prepared in Example 2 of the present invention;

[0028] Figure 7 It is a charge-discharge curve graph of the zinc sheet electrode modified with LiFe5O8 and the pure zinc electrode prepared in Example 2 of the present invention in a symmetric battery;

[0029] Figure 8 It is a cross-sectional SEM photograph of the zinc sheet electrode modified with LiFe5O8 prepared in Example 3 of the present invention;

[0030] Figure 9 It is a charge-discharge curve graph of the zinc sheet electrode modified with LiFe5O8 and the pure zinc electrode prepared in Example 3 of the present invention in a symmetric battery;

[0031] Figure 10 It is a schematic diagram of the Coulomb efficiency of the zinc sheet electrode modified with LiFe5O8 prepared in Example 4 of the present invention;

[0032] Figure 11 It is a schematic diagram of the stability of the zinc sheet electrode modified with LiFe5O8 prepared in Example 5 of the present invention in a full battery. Detailed Description of the Embodiments

[0033] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0034] In the description of the present application, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as limiting the protection scope of the present application. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0035] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations. In this embodiment, if it involves the X, Y, Z directions or the X, Y, Z axes, they are all based on the Cartesian coordinate system.

[0036] The technical solutions of the present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0037] Embodiment

[0038] Embodiment 1

[0039] Weigh 0.8 g of LiFe5O8, 0.1 g of activated carbon, and 0.1 g of PVDF. Then add a certain amount of NMP solvent and grind and mix them in an agate mortar for 30 minutes. Then adjust the height of the scraper and use the scraper to coat the slurry on the surface of the zinc plate. Dry the zinc plate in a vacuum at 120 °C, and after natural cooling to room temperature, cut the zinc plate into the required size to obtain a zinc composite electrode modified with LiFe5O8 described in Embodiment 1. Use SEM to measure its cross-sectional thickness. Figure 1It shows that the thickness of the prepared LiFe5O8 coating is 7 μm. The prepared zinc composite electrode was used as the working electrode, silver-silver chloride as the reference electrode, and platinum mesh as the counter electrode, and the LSV and Tafel curves were tested in 1 M NaSO4 and 3 M ZnSO4 respectively. Figure 2 It shows that the zinc composite electrode modified with LiFe5O8 has a higher hydrogen evolution overpotential. Figure 3 It shows that the zinc composite electrode modified with LiFe5O8 has a smaller corrosion current. The prepared composite electrode was used as the positive and negative electrodes, and an aqueous solution of 3 M ZnSO4 was used as the electrolyte to assemble a symmetric button cell, and its electrochemical performance was tested. The charge-discharge curve is as Figure 4 shown. Figure 4 It shows that the prepared electrode has a current density of 1 mA cm -2 and can be charged and discharged at a capacity density of 1 mAh cm -2 and can stably cycle 100 times. After disassembling the cycled electrode, the surface was observed by SEM. Figure 5 It shows that no dendrites are formed on the surface of the prepared electrode after 100 cycles.

[0040] Example 2

[0041] Weigh 1.2 g of LiFe5O8, 0.1 g of activated carbon, and 0.1 g of PVDF, then add a certain amount of NMP solvent, grind and mix in an agate mortar for 30 minutes, then adjust the height of the scraper, and then coat the slurry on the surface of the zinc plate with the scraper. The zinc plate was dried in vacuum at 120 °C, and after natural cooling to room temperature, the zinc plate was cut into the required size to obtain a zinc composite electrode modified with LiFe5O8 as described in Example 2. The cross-sectional thickness was measured by SEM. Figure 6 It shows that the thickness of the prepared LiFe5O8 coating is 11 μm. According to the method in Example 1, its electrochemical performance was tested. The charge-discharge curve is as Figure 7 shown. Figure 7 It shows that the prepared electrode has a current density of 1 mA cm -2 and can be charged and discharged at a capacity density of 1 mAh cm -2 and can stably cycle 100 times.

[0042] Example 3

[0043] Weigh 1.5 g of LiFe5O8, 0.1 g of activated carbon, and 0.1 g of PVDF, then add a certain amount of NMP solvent, grind and mix in an agate mortar for 30 minutes, then adjust the height of the scraper, and then coat the slurry on the surface of the zinc plate with the scraper. The zinc plate was dried in vacuum at 120 °C, and after natural cooling to room temperature, the zinc plate was cut into the required size to obtain a zinc composite electrode modified with LiFe5O8 as described in Example 3. The cross-sectional thickness was measured by SEM.Figure 8 It shows that the thickness of the prepared LiFe5O8 coating is 14 μm. According to the method in Example 1, its electrochemical performance was tested, and the charge-discharge curve is as Figure 9 shown. Figure 9 It shows that the prepared electrode was charged and discharged at a current density of 1 mA cm -2 at a capacity density of 1 mAh cm -2 and could be cycled stably for 100 cycles.

[0044] Example 4

[0045] According to the method in Example 2, a zinc electrode modified with LiFe5O8 was prepared. Using this electrode as the counter electrode and reference electrode, a copper sheet as the working electrode, and 3M ZnSO4 as the electrolyte, an asymmetric battery was assembled to test the Coulombic efficiency,

[0046] and the charge-discharge curve is as Figure 10 shown. Figure 10 It shows that compared with the pure zinc electrode, the zinc electrode modified with LiFe5O8 is more stable and has a higher Coulombic efficiency.

[0047] Example 5

[0048] According to the method in Example 1, a zinc composite electrode modified with LiFe5O8 was prepared. Using this electrode as the negative electrode, an electrode with carbon-coated iodine as the positive electrode, and an aqueous solution of 3M ZnSO4 as the electrolyte, a button-type full battery was assembled to test its electrochemical performance, and the charge-discharge cycle stability is as Figure 11 shown. It can be seen from Figure 11 that the full battery using the zinc composite electrode modified with LiFe5O8 can be cycled stably for 3000 cycles. For the full battery assembled with pure zinc, short circuit occurred in less than 500 cycles.

[0049] Example 6

[0050] Weighed zinc powder, LiFe5O8 powder, acetylene black and PTFE according to the ratio of 8:1:0.5:0.5, mixed them evenly, then added deionized water and isopropanol dropwise, and rolled them into a film. The obtained film was dried in an oven at 80 °C, then cut into circular electrodes and pressed onto a titanium mesh to obtain a zinc film electrode containing LiFe5O8 additive.

[0051] Example 7

[0052] Weighed Li2O and Fe2O3 according to a molar ratio of 1:5, mixed them in a ball milling jar for 1 hour, then heated them in a muffle furnace in air at a heating rate of 5 °C / min to 600 °C, held for 3 hours and cooled, then LiFe5O could be prepared 8。

[0053] Example 8

[0054] Weigh Li2CO3 and Fe2O3 respectively according to a molar ratio of 1:5. Mix the two in a ball milling tank for 1 hour, and then in a muffle furnace in air, heat at a rate of 5 °C / min to 800 °C, hold for 3 hours, and after cooling, LiFe5O can be prepared. 8。

[0055] Example 9

[0056] Weigh Na2CO3 and Fe2O3 respectively according to a molar ratio of 1:5. Mix the two in a ball milling tank for 1 hour, and then in a muffle furnace in air, heat at a rate of 5 °C / min to 800 °C, hold for 5 hours, and after cooling, NaFe5O can be prepared. 8。

[0057] Example 10

[0058] Weigh K2CO3 and Fe2O3 respectively according to a molar ratio of 1:5. Mix the two in a ball milling tank for 1 hour, and then in a muffle furnace in air, heat at a rate of 5 °C / min to 800 °C, hold for 8 hours, and after cooling, KFe5O can be prepared. 8。

[0059] The preparation process applicable to the present invention is not limited to the specific several in the above embodiments. For example, LiFe5O8 and Zn powder can be ball milled and mixed according to a certain mass ratio, and then mixed with carbon and a binder to prepare a thin film electrode. When LiFe5O8 is used as a coating, it can be modified onto the surface of zinc or zinc alloy by means such as direct spraying, printing process, electroplating or sputtering. Furthermore, MFe5O8 is not limited to LiFe5O8, NaFe5O8 or KFe5O8, and can be Li x Na 1-x Fe5O8, Li x K 1-x Fe5O8, Na x K 1-x Fe5O8, where 0 < x < 1; or Li x Na y K 1-x-y Fe5O8, where 0 < x < 1; 0 < y < 1 and 0 < x + y < 1. In addition, the present invention is not limited to MFe5O8 type materials. Materials prepared by solid-phase sintering of M2O or M2CO3 and Fe2O3 in different stoichiometric ratios can all be regarded as variant materials of MFe5O8 type and can be flexibly adjusted according to actual application requirements.

[0060] Inspired by the above-described ideal embodiments of the present application, through the above description, relevant staff can fully make various changes and modifications without departing from the technical idea of this application. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for manufacturing a coating for suppressing zinc dendrites, characterized in that, After the material for suppressing zinc dendrites is ground and mixed evenly with carbon, binder and organic solvent, it is coated on the surface of zinc sheet or zinc alloy sheet; the coating thickness does not exceed 20 μm; The material for suppressing zinc dendrites has the chemical formula MFe5O8, where M is one or more of Li, Na, and K elements; The preparation method of the material for suppressing zinc dendrites is as follows: M2CO3 or M2O and Fe2O3 are evenly mixed according to a molar ratio of 1:5, and then solid-phase sintered in air at 500~800 °C to prepare MFe5O8.

2. The method for manufacturing a coating for suppressing zinc dendrites according to claim 1, wherein The chemical formula of the material for suppressing zinc dendrites is LiFe5O8.

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