Metal electrode for metal-air battery and preparation method of metal electrode

Abstract

The invention discloses a metal electrode for a metal air battery and a preparation method thereof, a mechanical tabletting method is adopted, nickel oxide and ((Fe2O3 or Fe3O4 or Fe) or Fe3O4 or Fe) are mixed, and then mixed powder is pressed into a sheet shape through mechanical pressure in a mold. Calcining a sheet body obtained by tabletting at 1200 DEG C, so that the two oxides are co-sintered. And heating the sintered sheet body at 750 DEG C under the mixed atmosphere of hydrogen and nitrogen, and reducing to prepare the metal electrode of the metal-air battery. The method belongs to the field of metal-air batteries. The metal electrode of the metal-air battery prepared by the method has the properties of relatively high conductivity, good thermal stability and good mechanical strength.

Description

Technical Field

[0001] The present invention relates to the technical field of metal-air batteries, and more specifically, to a metal electrode for a metal-air battery and a preparation method thereof. More specifically, the present invention relates to a method for preparing a metal electrode for a metal-air battery by mechanically pressing and sintering at high temperature, wherein a pressed NiO / (Fe2O3 or Fe3O4 or Fe) sheet material is subjected to high-temperature sintering and then reduced. Background Art

[0002] The rapid depletion of fossil fuels and the increasingly severe ecological crisis have led to a growing demand for sustainable energy conversion and storage devices. Among these energy devices, metal-air batteries are considered the most competitive due to their low environmental pollution, high conversion rate, and high energy density. Among chemical energy storage devices, metal-air batteries are considered a semi-fuel cell between primary cells and fuel cells. They are both efficient and clean energy conversion and storage devices, converting chemical energy into electrical energy through an electrochemical reaction between a metal cathode and an air cathode. They boast low environmental pollution, high discharge capacity, and high energy density, making them considered the most competitive energy device. Their development is of great strategic significance to the rapid development of my country's and local energy, transportation, information, and defense sectors, and to the construction of a "clean, low-carbon, safe, and efficient" modern energy industry system and the formation and development of related strategic emerging industries.

[0003] Metal-air batteries use metal as the negative electrode, air as the positive electrode, and an electrolyte with corresponding conductivity and voltage tolerance. During discharge, the metal on the negative electrode undergoes an oxidation reaction and is gradually consumed. The oxygen on the positive electrode passes through the gas diffusion electrode to the gas-liquid-solid three-phase interface and undergoes oxygen reduction to obtain electrons. At the same time, the metal negative electrode loses electrons to generate metal ions, generating current output, realizing the conversion of chemical energy and electrical energy. The electrolyte of the metal-air battery is mostly an alkaline (NaOH, KOH) solution with good conductivity, a neutral (NaCl) solution or an organic electrolyte to ensure the mass transfer rate and kinetic reaction rate of the air positive electrode reaction. The electrolyte system varies depending on the type of metal-air battery. Due to the use of metal as the negative electrode, the metal-air battery has the characteristics of being environmentally friendly, widely available, and non-toxic. At the same time, air is used as the positive electrode active material. The main problem of metal-air batteries at present is that porous zinc is used as the negative electrode, which requires amalgamation. Mercury not only harms the health of workers but also pollutes the environment, and needs to be replaced by a non-mercury corrosion inhibitor. The present invention uses iron and iron oxides, which are environmentally friendly batteries. Summary of the Invention

[0004] In response to the above-mentioned technical problems, a metal electrode for a metal-air battery and a method for preparing the same are provided. The present invention utilizes a method for mechanically pressing and high-temperature co-sintering metal oxide materials to prepare a composite metal oxide electrode material by mechanical pressing and high-temperature sintering. The metal electrode is then reduced at a predetermined high temperature in a hydrogen and nitrogen atmosphere to form a metal electrode with a high discharge rate.

[0005] The technical means adopted in the present invention are as follows:

[0006] A method for preparing a metal electrode for a metal-air battery comprises the following steps: preparing a mixed powder, ball milling, tableting, and calcining. Specifically, the method comprises the following steps:

[0007] The steps of preparing mixed powder, ball milling, tableting and calcining specifically include the following steps:

[0008] Mixing iron or iron oxide and nickel oxide in a certain proportion to form a mixed powder;

[0009] After ball milling the above mixture, the prepared mixed powder is pressed into a sheet material in a mold using a tabletting method;

[0010] The pressed NiO / iron or iron oxide sheet material is sintered at a high temperature to prepare a NiO / iron or iron oxide sheet material with high mechanical strength;

[0011] The prepared high mechanical strength sheet material is reduced at a preset high temperature in a hydrogen and nitrogen atmosphere to prepare a metal electrode.

[0012] Furthermore, the mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and iron or iron oxide powder are 10-5% and 95-90% respectively.

[0013] Furthermore, nickel oxide powder and iron or iron oxide powder weighed in a preset ratio are respectively ball-milled in a ball mill for 1 hour, and the ball-milled powders are mixed and placed in a centrifuge for stirring for 1 to 3 hours;

[0014] Furthermore, after ball milling the above mixture, the mixed powder is poured into a tablet press mold, pressurized to about 10 MPa, and then left to stand for about 5 to 10 minutes before demoulding. The thickness of the metal sheet is 1.4 to 1.6 mm.

[0015] Furthermore, the pressed NiO / iron or iron oxide sheet material is subjected to high-temperature sintering as follows: the high-temperature sintering is temperature-programmed firing, and when the NiO / iron or iron oxide sheet material is temperature-programmed firing, the heating rate from room temperature to 400±10°C is 1-2°C / min, after being kept constant at 400±10°C for 1±0.5h, the heating rate from 400±10°C to 1200-1300°C is 1-3°C / min, the temperature is kept constant at 1300-1600°C for 3±0.5h, and finally the temperature is cooled to room temperature at 1-2°C / min to prepare the NiO / iron or iron oxide sheet material with high mechanical strength;

[0016] Furthermore, the sintered NiO / iron or iron oxide high mechanical strength sheet material is heated to 750° C. in a mixed atmosphere of hydrogen and nitrogen for reduction.

[0017] Furthermore, the prepared high mechanical strength sheet material is reduced at a preset high temperature and in a hydrogen and nitrogen atmosphere to prepare a metal electrode. Specifically, the high temperature reduction is a programmed temperature firing. When the NiO / iron or iron oxide sheet material is reduced by temperature programming, the heating rate from room temperature to 200±10°C is 1-2°C / min. After being kept constant at 200±10°C for 1±0.5h, the heating rate from 200±10°C to 750-800°C is 1-3°C / min. The temperature is kept constant at 750-800°C for 3±0.5h, and finally the temperature is reduced to room temperature at a rate of 1-2°C / min.

[0018] The present invention also claims protection for the metal electrode of the metal-air battery prepared based on the above method.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The co-sintering process is simple, low-cost, and pollution-free, and the sintered iron electrode has stronger mechanical strength. This strength comes from the fact that the particles of the active material are sintered at a relatively high temperature to form a strong porous electrode;

[0021] 2. Compared with other types of electrodes, the sintered iron electrode prepared by the present invention has better tolerance to charge and discharge cycles and tolerance to overcharge and overdischarge;

[0022] 3. The present invention provides a method for preparing a metal-air battery composite metal electrode with low production cost and simple process, which is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 Shown is a microscopic schematic diagram of a metal-air battery.

[0025] Figure 2 Schematic diagram of the voltage and power density curves obtained in this experiment is shown in FIG.

[0026] Figure 3 The figure shows a discharge curve obtained by constant current discharge in a control group experiment using batteries assembled with electrode sheets prepared in Experimental Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention.

[0028] This embodiment discloses a method for preparing a metal electrode for a metal-air battery, comprising the following steps: preparing a mixed powder, ball milling, tableting, and calcining. Specifically, the method comprises the following steps:

[0029] The iron or iron oxide and nickel oxide are mixed in a certain proportion to form a mixed powder. The mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and iron or iron oxide powder are: 10% to 5% and 95% to 90% respectively;

[0030] Furthermore, as a specific embodiment, the mass range of nickel oxide, iron or iron oxide used to prepare NiO / iron or iron oxide flaky material is 0.1g to 0.05g, 0.6g to 0.5g.

[0031] Weigh nickel oxide powder and iron or iron oxide powder in a preset ratio, ball mill the nickel oxide powder and iron or iron oxide powder in a ball mill for 1 hour, mix the milled powders and place them in a centrifuge for stirring for 1 to 3 hours;

[0032] After ball milling, the mixed powder is poured into a tablet press mold and pressurized to about 10 MPa. After standing for about 5 to 10 minutes, the mold is removed. The thickness of the metal sheet is 1.4 to 1.6 mm.

[0033] The pressed NiO / iron or iron oxide flake material is subjected to high temperature sintering as follows: the high temperature sintering is a programmed temperature firing, when the NiO / iron or iron oxide flake material is subjected to programmed temperature firing, the heating rate from room temperature to 400±10°C is 1-2°C / min, after being kept constant at 400±10°C for 1±0.5h, the heating rate from 400±10°C to 1200-1300°C is 1-3°C / min, the temperature is kept constant at 1300-1600°C for 3±0.5h, and finally the temperature is cooled to room temperature at 1-2°C / min to prepare the NiO / iron or iron oxide flake material with high mechanical strength;

[0034] The sintered NiO / iron or iron oxide high mechanical strength sheet material is heated to 750°C in a mixed atmosphere of hydrogen and nitrogen for reduction. The reduction of the NiO / iron or iron oxide sheet material is specifically as follows: the high-temperature reduction is programmed temperature sintering. When the NiO / iron or iron oxide sheet material is temperature-programmed, the heating rate from room temperature to 200±10°C is 1-2°C / min, after being kept constant at 200±10°C for 1±0.5h, the heating rate from 200±10°C to 750-800°C is 1-3°C / min, the temperature is kept constant at 750-800°C for 3±0.5h, and finally the temperature is reduced to room temperature at 1-2°C / min.

[0035] The metal electrode microstructure of the final prepared metal-air battery is as follows Figure 1 As shown in the figure, during discharge, the negative electrode of a metal-air battery releases metal ions into the electrolyte, while the positive electrode (air electrode) absorbs oxygen. These metal ions migrate through the electrolyte, eventually reaching the positive electrode and reacting with oxygen to form metal oxides and water, while simultaneously releasing electrons and generating electricity. The charging process is the reverse of the discharge process. During charging, the metal oxides and water decompose into metal ions and oxygen, with the metal ions returning to the negative electrode and the oxygen returning to the positive electrode. This process is reversible, ensuring the battery's reusability.

[0036] The voltage and power density curves of the metal-air battery prepared in the ideal case are as follows: Figure 2 shown.

[0037] Example 1

[0038] This embodiment discloses a method for preparing a metal electrode for a metal-air battery, comprising the following steps: preparing a mixed powder, ball milling, tableting, and calcining. Specifically, the method comprises the following steps:

[0039] The iron powder and nickel oxide are mixed in a certain proportion to form a mixed powder. The mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and iron powder are 10% and 90% respectively;

[0040] Weigh nickel oxide powder and iron powder in a preset ratio, ball mill the nickel oxide powder and iron powder in a ball mill for 1 hour, mix the milled powders and place them in a centrifuge for stirring for 1 hour;

[0041] After ball milling, the mixed powder was poured into a tablet press mold, pressurized to about 10 MPa, and then left to stand for about 5 minutes before demoulding. The thickness of the metal sheet was 1.4 mm.

[0042] The pressed NiO / iron flake material is subjected to high temperature sintering as follows: the high temperature sintering is a programmed temperature firing, when the NiO / iron flake material is subjected to programmed temperature firing, the heating rate from room temperature to 400°C is 1°C / min, after being kept constant at 400°C for 1 hour, the heating rate from 400°C to 1200°C is 1°C / min, the temperature is kept constant at 1300°C for 3 hours, and finally the temperature is cooled to room temperature at 1°C / min, thereby preparing the NiO / iron high mechanical strength flake material;

[0043] The sintered NiO / iron flake material is heated to 750°C in a mixed atmosphere of hydrogen and nitrogen for reduction. The reduction of the NiO / iron flake material is specifically as follows: the high-temperature reduction is programmed temperature sintering. When the NiO / iron flake material is reduced by programmed temperature, the heating rate from room temperature to 200°C is 1°C / min. After maintaining the temperature at 200°C for 1 hour, the heating rate from 200°C to 750°C is 1°C / min. The temperature is maintained at 750°C for 3 hours, and finally the temperature is reduced to room temperature at 2°C / min.

[0044] (Further, as a specific embodiment, the masses of nickel oxide and iron used to prepare the NiO / iron flake material are 0.1g and 0.5g respectively.)

[0045] Example 2

[0046] This embodiment discloses a method for preparing a metal electrode for a metal-air battery, comprising the following steps: preparing a mixed powder, ball milling, tableting, and calcining. Specifically, the method comprises the following steps:

[0047] The ferric oxide and nickel oxide are mixed in a certain proportion to form a mixed powder. The mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and ferric oxide powder are 7.5% and 97.5% respectively;

[0048] Weigh nickel oxide powder and ferric oxide powder in a preset ratio, ball mill the nickel oxide powder and ferric oxide powder in a ball mill for 1 hour, and then mix the milled powders and place them in a centrifuge for 2 hours;

[0049] After ball milling, the mixed powder was poured into a tablet press mold, pressurized to about 10 MPa, and allowed to stand for about 7.5 minutes before demoulding. The thickness of the metal sheet was 1.5 mm.

[0050] The pressed NiO / ferric oxide flake material is subjected to high temperature sintering as follows: the high temperature sintering is a programmed temperature firing, when the NiO / ferric oxide flake material is subjected to programmed temperature firing, the heating rate from room temperature to 400±10°C is 1.5°C / min, after being kept constant at 405°C for 1 hour, the heating rate from 405°C to 1250°C is 1-3°C / min, the temperature is kept constant at 1450°C for 3 hours, and finally the temperature is cooled to room temperature at a rate of 1.5°C / min, to prepare a NiO / ferric oxide flake material with high mechanical strength;

[0051] The sintered NiO / ferric oxide flake material is heated to 750°C in a mixed atmosphere of hydrogen and nitrogen for reduction. The reduction of the NiO / ferric oxide flake material is specifically as follows: the high-temperature reduction is programmed temperature sintering. When the NiO / ferric oxide flake material is reduced by programmed temperature, the heating rate from room temperature to 205°C is 1.5°C / min. After maintaining the temperature at 205°C for 1 hour, the heating rate from 205°C to 775°C is 2°C / min. The temperature is maintained at 775°C for 3 hours, and finally the temperature is cooled to room temperature at a rate of 1.5°C / min.

[0052] (Further, as a specific embodiment, the masses of nickel oxide and ferric oxide used to prepare the NiO / ferric oxide flake material are 0.075g and 0.55g respectively.)

[0053] Example 3

[0054] This embodiment discloses a method for preparing a metal electrode for a metal-air battery, comprising the following steps: preparing a mixed powder, ball milling, tableting, and calcining. Specifically, the method comprises the following steps:

[0055] Mix ferroferric oxide and nickel oxide in a certain proportion to form a mixed powder. The mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and ferroferric oxide powder are 5% and 95% respectively;

[0056] Weigh nickel oxide powder and ferroferric oxide powder in a preset ratio, ball mill the nickel oxide powder and ferroferric oxide powder in a ball mill for 1 hour, and then mix the milled powders and place them in a centrifuge for 3 hours;

[0057] After ball milling, the mixed powder was poured into a tablet press mold, pressurized to about 10 MPa, and then left to stand for about 10 minutes before demoulding. The thickness of the metal sheet was 1.6 mm.

[0058] The pressed NiO / ferroferric oxide sheet material is subjected to high-temperature sintering as follows: the high-temperature sintering is a programmed temperature firing, wherein the NiO / ferroferric oxide sheet material is subjected to a temperature-programmed firing process, wherein the temperature is raised from room temperature to 410°C at a rate of 2°C / min, maintained at 410°C for 1.5 hours, then raised from 10°C to 1300°C at a rate of 3°C / min, maintained at 1600°C for 3.5 hours, and finally cooled to room temperature at a rate of 2°C / min, thereby preparing a NiO / ferroferric oxide sheet material with high mechanical strength;

[0059] The sintered NiO / ferroferric oxide flake material was heated to 750°C in a mixed atmosphere of hydrogen and nitrogen for reduction. The reduction of the NiO / ferroferric oxide flake material was specifically as follows: the high-temperature reduction was programmed temperature sintering. When the NiO / ferroferric oxide flake material was temperature-programmed, the heating rate from room temperature to 210°C was 2°C / min. After being kept constant at 210°C for 1.5 hours, the heating rate from 210°C to 800°C was 3°C / min. The temperature was kept constant at 800°C for 3.5 hours, and finally the temperature was cooled to room temperature at 2°C / min.

[0060] (Further, as a specific embodiment, the mass range of nickel oxide and ferroferric oxide used to prepare the NiO / ferroferric oxide sheet material is 0.05g and 0.6g.)

[0061] Comparative Example 1

[0062] This embodiment discloses a method for preparing a metal electrode for a metal-air battery, comprising the following steps: preparing a mixed powder, ball milling, tableting, and calcining. Specifically, the method comprises the following steps:

[0063] The ferric oxide and nickel oxide are mixed in a certain proportion to form a mixed powder. The mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and ferric oxide powder are 7.5% and 92.5% respectively;

[0064] Weigh nickel oxide powder and ferric oxide powder in a preset ratio, ball mill the nickel oxide powder and ferric oxide powder in a ball mill for 1 hour, and then mix the milled powders and place them in a centrifuge for 2 hours;

[0065] After ball milling, the mixed powder was poured into a tablet press mold, pressurized to about 10 MPa, and allowed to stand for about 7.5 minutes before demoulding. The thickness of the metal sheet was 1.5 mm.

[0066] The pressed NiO / FeO2 sheet material was combined with the air electrode to assemble a battery with 30% KOH as the electrolyte solution, and the battery assembled with the electrode sheet prepared in Experimental Example 2 was used as a control experimental group. Figure 3 It can be seen that the electrode sheet prepared by the dry pressing co-sintering method in Example 2 has better discharge efficiency than that in Comparative Example 1 under the discharge environment.

[0067] (Further, as a specific embodiment, the mass range of nickel oxide and ferric oxide used to prepare the NiO / ferric oxide flake material is 0.075g and 0.55g respectively.)

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a metal electrode for a metal-air battery, characterized in that: The method comprises the following steps: preparing mixed powder, ball milling, tableting, and calcining, specifically comprising the following steps: Mixing iron or iron oxide and nickel oxide in a certain proportion to form a mixed powder; After ball milling the mixture, the prepared mixed powder is pressed into a sheet material in a mold using a tabletting method to obtain a sheet material; The pressed NiO / iron or iron oxide sheet material is sintered at a high temperature to prepare a NiO / iron or iron oxide sheet material with high mechanical strength; The prepared high mechanical strength sheet material is reduced at a preset high temperature in a hydrogen and nitrogen atmosphere to prepare a metal electrode.

2. The method according to claim 1, characterized in that The mixed powder material is calculated by mass ratio, and the proportions of nickel oxide powder and iron or iron oxide powder are 10-5% and 95-90% respectively.

3. The method according to claim 1, characterized in that The specific steps of configuration and mixing are: weighing nickel oxide powder and iron or iron oxide powder according to a preset ratio, ball milling the nickel oxide powder and iron or iron oxide powder in a ball mill for 1±0.5h respectively, and mixing the ball-milled powders into a centrifuge and stirring for 1 to 3 hours.

4. The method according to claim 1, wherein The prepared mixed powder is pressed into NiO / iron or iron oxide sheet material in a mold as follows: the mixed powder is poured into a tablet press mold, pressurized and allowed to stand for 5 to 10 minutes before demoulding. The thickness of the metal sheet is 1.4 to 1.6 mm.

5. The method according to claim 1, characterized in that The preparation of NiO / iron or iron oxide flake materials is specifically as follows: high-temperature sintering is programmed temperature firing. When the NiO / iron or iron oxide flake materials are programmed temperature fired, the heating rate from room temperature to 400±10°C is 1-2°C / min, after being kept constant at 400±10°C for 1±0.5h, the heating rate from 400±10°C to 1200-1300°C is 1-3°C / min, and the temperature is kept constant at 1300-1600°C for 3±0.5h, and finally the temperature is reduced to room temperature at 1-2°C / min.

6. The method according to claim 1, characterized in that The sintered NiO / iron or iron oxide high mechanical strength sheet material is heated to 650-800° C. in a mixed atmosphere of hydrogen and nitrogen for reduction.

7. The method according to claim 1, characterized in that The prepared high mechanical strength sheet material is reduced at a preset high temperature and in a hydrogen and nitrogen atmosphere to prepare a metal electrode. Specifically, the high temperature reduction is a programmed temperature firing. When the NiO / iron or iron oxide sheet material is reduced by temperature programming, the heating rate from room temperature to 200±10°C is 1-2°C / min. After being kept constant at 200±10°C for 1±0.5h, the heating rate from 200±10°C to 750-800°C is 1-3°C / min. The temperature is kept constant at 750-800°C for 3±0.5h, and finally the temperature is dropped to room temperature at a rate of 1-2°C / min.

8. A metal electrode for a metal-air battery prepared by the method according to any one of claims 1 to 6.

Images