Mg-ca-sn-in anode material and preparation method and application thereof

Abstract

This invention provides a Mg-Ca-Sn-In anode material, its preparation method, and its application, belonging to the field of magnesium-air battery technology. The mass percentage of each metal element in the Mg-Ca-Sn-In anode material is as follows: calcium 0.001~2.0 wt.%; tin 0.001~2.0 wt.%; indium 0.001~4.0 wt.%; the total content of unavoidable impurity elements is less than 0.01 wt.%; the remainder is magnesium. Microalloying is achieved by doping appropriate amounts of Ca, Sn, and In into the pure magnesium anode, and elemental segregation in the magnesium anode is improved through heat treatment. The Mg-Ca-Sn-In alloy of this invention, as an anode material, can enhance the corrosion resistance of the magnesium-air battery anode, activate the anode reaction kinetics, maintain the anode activation area, suppress the negative differential effect, reduce self-corrosion hydrogen evolution, and improve the battery's discharge voltage and anode efficiency while ensuring stable discharge, significantly extending the battery's service life.

Description

Technical Field

[0001] This invention belongs to the field of magnesium-air battery technology, and specifically relates to a Mg-Ca-Sn-In anode material and its preparation method, as well as its application as an anode in magnesium-air batteries. Background Technology

[0002] Magnesium-air batteries are primary batteries that use magnesium and its alloys as "fuel." They are batteries that cannot be recharged by an external current after discharge, but can continue to supply power by mechanically replacing the anode and electrolyte. Magnesium has a relatively negative standard electrode potential (-2.37 V). vs.SHE Magnesium ore is a metallic fuel that can release electrons to generate electricity, and my country's magnesium ore reserves and production are among the highest in the world, making it an advantageous resource.

[0003] In magnesium-air batteries, magnesium and its alloys, acting as the anode, are oxidized to Mg during discharge. 2+ Electrons are output to the external circuit, where a reduction reaction occurs at the cathode, causing oxygen in the air and water in the electrolyte to gain electrons and generate OH-. - However, in practical applications, several key issues still limit its large-scale industrial use. Theoretically, the voltage of a magnesium-air battery is 3.1 V. However, due to internal resistance within the battery system, such as anode and cathode polarization and electrolyte resistance, and the accumulation of discharge products on the anode and cathode surfaces separating the electrodes from the electrolyte, the actual operating voltage is much lower than the theoretical value. Furthermore, during discharge, due to the reactive nature of magnesium, it easily undergoes self-discharge, releasing hydrogen gas, leading to ineffective consumption of the anode and reducing anode efficiency.

[0004] Therefore, it is necessary to develop a magnesium alloy anode material with stable discharge, high discharge voltage, and high anode efficiency to extend the service life of magnesium-air batteries and enable their application in high-power electrical equipment. Summary of the Invention

[0005] To address the problems existing in the use of anode materials in magnesium-air batteries, this invention provides a Mg-Ca-Sn-In alloy, its preparation method, and its application as an anode material in magnesium-air batteries, based on the design concept of using Ca, Sn, and In as the main alloying elements.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] In a first aspect, the present invention provides a Mg-Ca-Sn-In anode material, wherein the mass percentage of each metal element in its chemical composition is as follows: calcium (Ca) 0.001 ~ 2.0 wt.%; tin (Sn) 0.001 ~ 2.0 wt.%; indium (In) 0.001 ~ 4.0 wt.%; the total content of unavoidable impurity elements is less than 0.01 wt.%; and the remainder is magnesium (Mg).

[0008] Furthermore, in the Mg-Ca-Sn-In anode material, the main alloying elements are Ca, Sn, and In, but it is not limited to alloy materials containing only Mg, Sn, and In. Within the aforementioned alloy composition range, magnesium alloy anode materials obtained by adding one or more commonly used trace alloying elements of magnesium alloys are also within the scope of protection of this invention:

[0009] Aluminum (Al): 0.01 wt.% ~0.05 wt.%;

[0010] Manganese (Mn): 0.01 wt.% ~ 0.05 wt.%;

[0011] Zinc (Zn): 0.01 wt.% ~ 0.05 wt.%;

[0012] Cerium (Ce): 0.01 wt.% ~ 0.05 wt.%;

[0013] Copper (Cu): 0.01 wt.% ~ 0.05 wt.%;

[0014] Zirconium (Zr): 0.01 wt.% ~ 0.05 wt.%;

[0015] Silver (Ag): 0.01 wt.% ~ 0.05 wt.%;

[0016] Mercury (Hg): 0.01 wt.% ~ 0.05 wt.%;

[0017] Gallium (Ga): 0.01 wt.% ~ 0.05 wt.%;

[0018] Germanium (Ge): 0.01 wt.% ~ 0.05 wt.%;

[0019] Rare earth elements (Re): 0.01 wt.% ~ 0.05 wt.%.

[0020] Secondly, the present invention provides a method for preparing the Mg-Ca-Sn-In anode material, comprising the following steps:

[0021] (1) Weigh the required raw materials according to the composition ratio of Mg-Ca-Sn-In alloy, including high-purity magnesium ingot, high-purity indium ingot, magnesium-tin master alloy and magnesium-calcium master alloy.

[0022] (2) After cleaning the high-purity magnesium ingot, high-purity indium ingot, magnesium-tin master alloy and magnesium-calcium master alloy, add them to the crucible, fill it with a protective atmosphere, heat and melt it into a melt, and then hold it for the first time. After that, cast it to obtain Mg-Ca-Sn-In ingot.

[0023] (3) The ingot is kept warm for a second time to obtain a homogeneous Mg-Ca-Sn-In alloy, which is used as the Mg-Ca-Sn-In anode material.

[0024] Furthermore, the protective atmosphere is a mixture of SF6-containing gases, nitrogen, or argon. The SF6-containing gas mixture is a mixture of SF6 with carbon dioxide, sulfur dioxide, nitrogen, or argon, wherein the volume percentage of SF6 is ≤10%.

[0025] Furthermore, the first heat treatment is carried out at a temperature of 700~750℃ for 20 minutes. This process is intended to melt and obtain Mg-Ca-Sn-In alloy ingots.

[0026] Furthermore, the second heat treatment is carried out at a temperature of 200~450℃ for 10~30 hours. This serves to homogenize the Mg-Ca-Sn-In alloy ingot.

[0027] Thirdly, this invention provides the application of the Mg-Ca-Sn-In anode material, specifically as an anode material in a magnesium-air battery. The magnesium-air battery of this invention includes: a Mg-Ca-Sn-In anode, an air cathode, and an electrolyte.

[0028] The present invention has the following beneficial effects:

[0029] The Mg-Ca-Sn-In alloy of the present invention is microalloyed by doping appropriate amounts of Ca, Sn and In elements into a pure magnesium anode, and the elemental segregation of the magnesium anode is improved by heat treatment. For the homogeneous Mg-Ca-Sn-In anode material, Ca and Sn mainly exist in two forms: (1) in the form of second-phase Mg2Ca and CaMgSn intermetallic compounds in the α-Mg matrix, with strip-shaped Mg2Ca distributed along the grain boundaries and granular Mg2Ca and CaMgSn distributed within the grains; (2) a small amount of Ca and Sn are dissolved in the α-Mg matrix in atomic form. In element is mainly dissolved in the α-Mg matrix, Mg2Ca and CaMgSn in atomic form. Mg2Ca, as the anode phase, promotes the formation of preferential discharge sites. CaMgSn can act as a cathode to accelerate the discharge dissolution of the surrounding α-Mg matrix and activate the anode reaction kinetics; through physical shedding, it causes cracks in the discharge products, maintaining the contact between the anode and the electrolyte.

[0030] In has a high solid solubility in the magnesium matrix, and mainly exists as dissolved atoms in α-Mg, Mg2Ca, and CaMgSn, reducing the potential difference between the three, inhibiting the further development of microgalvanic corrosion, slowing down hydrogen evolution during discharge, and improving anode efficiency. During discharge, indium is oxidized to indium ions, which are then reduced to metallic indium by magnesium and calcium and deposited at the interface between the anode and the film, thereby improving the interfacial conditions between the anode surface and the electrolyte.

[0031] The Mg-Ca-Sn-In alloy of this invention, used as an anode material, can enhance the corrosion resistance of the magnesium-air battery anode, activate anode reaction kinetics, maintain the anode activation area, suppress the negative differential effect, and reduce self-corrosion hydrogen evolution. It can improve the battery's discharge voltage and anode efficiency while ensuring stable discharge, significantly extending the battery's lifespan. Furthermore, the Mg-Ca-Sn-In alloy of this invention has a simple preparation process, low cost, and is easy to promote and apply, making it suitable for high-power electrical equipment. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 Metallographic optical microscope and electron microscope images of the homogeneous Mg-Ca-Sn-In alloys prepared in Examples 1-3, wherein, Figure 1 (a) is a metallographic optical microscope image of the alloy in Example 1. Figure 1(b) is a metallographic optical microscope image of the alloy in Example 2. Figure 1 (c) is a metallographic optical microscope image of the alloy of Example 3. Figure 1 (a1) is an electron microscope image of the alloy in Example 1. Figure 1 (b1) is an electron microscope image of the alloy in Example 2. Figure 1 (c1) is an electron microscope image of the alloy in Example 3.

[0034] Figure 2 The alloys of Examples 1-3 were tested at 2mA cm. -2 and 40mA cm -2 Electron micrographs of the anode surface after discharge at current density, in which Figure 2 (a) Example 1 at 2mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (b) Example 2 at 2mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (c) Example 3 at 2mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (d) is Example 1 at 40mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (e) Example 2 at 40mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (f) Example 3 at 40mA cm -2 Electron microscope image of the anode surface after discharge at current density. Detailed Implementation

[0035] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be described in detail below with reference to specific embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of the invention.

[0036] Example 1

[0037] A Mg-Ca-Sn-In alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 0.42 wt.% Sn; 0.92 wt.% Ca; 0.44 wt.% In; the remainder being unavoidable impurities and magnesium.

[0038] Prepare a crucible, ensuring it is free from leaks and defects that would affect its use. Preheat the crucible to approximately 600°C, fill it with argon gas for protection, and add high-purity magnesium ingots, high-purity indium ingots, magnesium-tin master alloy, and magnesium-calcium master alloy. Increase the heating temperature to 750°C to melt the raw materials into a molten state. After stirring, skim off any scum floating on the surface of the alloy liquid. Maintain the temperature at 720°C and hold the alloy liquid at this temperature for 20 minutes. Cast the alloy into cylindrical ingots, and then hold the ingots at 400°C for 10 hours for homogenization.

[0039] Example 2

[0040] A Mg-Ca-Sn-In alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 0.45 wt.% Sn; 0.95 wt.% Ca; 0.90 wt.% In; the remainder being unavoidable impurities and magnesium.

[0041] Prepare a crucible, ensuring it is free from leaks and defects that would affect its use. Preheat the crucible to approximately 600°C, fill it with argon gas for protection, and add high-purity magnesium ingots, high-purity indium ingots, magnesium-tin master alloy, and magnesium-calcium master alloy. Increase the heating temperature to 750°C to melt the raw materials into a molten state. After stirring, skim off any scum floating on the surface of the alloy liquid. Maintain the temperature at 720°C and hold the alloy liquid at this temperature for 20 minutes. Cast the alloy into cylindrical ingots, and then hold the ingots at 400°C for 10 hours for homogenization.

[0042] Example 3

[0043] A Mg-Ca-Sn-In alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 0.46 wt.% Sn; 0.92 wt.% Ca; 1.76 wt.% In; the remainder being unavoidable impurities and magnesium.

[0044] Prepare a crucible, ensuring it is free from leaks and defects that would affect its use. Preheat the crucible to approximately 600°C, fill it with argon gas for protection, and add high-purity magnesium ingots, high-purity indium ingots, magnesium-tin master alloy, and magnesium-calcium master alloy. Increase the heating temperature to 750°C to melt the raw materials into a molten state. After stirring, skim off any scum floating on the surface of the alloy liquid. Maintain the temperature at 720°C and hold the alloy liquid at this temperature for 20 minutes. Cast the alloy into cylindrical ingots. Hold the ingots at 400°C for 10 hours for homogenization treatment.

[0045] Comparative Example 1

[0046] A Mg-Ca-Zn alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 1.02 wt.% Ca; 1.18 wt.% Zn, with the remainder being magnesium and unavoidable impurities.

[0047] Prepare a crucible, ensuring it is free from leaks and defects that could affect its use. Preheat the crucible to approximately 600°C, fill it with argon gas for protection, add high-purity magnesium ingots, high-purity zinc ingots, and magnesium-calcium master alloy, and raise the heating temperature to 715°C to melt the raw materials into a molten state. After stirring, skim off any scum floating on the surface of the alloy liquid. After holding the liquid at this temperature for 20 minutes, pour it into a preheated graphite crucible at 200°C and cast it into a cylindrical ingot.

[0048] Comparative Example 2

[0049] A Mg-Ca-In alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 1.54 wt.% Ca; 3.36 wt.% In, with the remainder being magnesium and unavoidable impurities.

[0050] Prepare a crucible, ensuring it is free from leaks and defects that could affect its use. Fill the crucible with a mixture of CO2 and SF6 as a protective gas, with SF6 comprising 5% by volume. Add high-purity magnesium ingots, high-purity indium ingots, and magnesium-calcium master alloy to the low-carbon steel crucible. Increase the heating temperature to 720°C to melt the raw materials into a molten state. After stirring, skim off the slag from the surface of the alloy liquid and cool it to 690°C. Cast the liquid and water-cool it into a cylindrical ingot.

[0051] Comparative Example 3

[0052] A Mg-Ca-In alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 4.32 wt.% Ca; 3.76 wt.% In, with the remainder being magnesium and unavoidable impurities.

[0053] Prepare a crucible, ensuring it is free from leaks and other defects that could affect its use. Add high-purity magnesium ingots, high-purity indium ingots, and a magnesium-calcium master alloy to the low-carbon steel crucible. Pour in argon gas for protection and raise the heating temperature to 720°C to melt the raw materials in a vacuum. After stirring, skim off the slag from the surface of the alloy melt. Cool the mixture to 690°C and cast it into a cylindrical ingot using water cooling. (Liu, H.; Zhao, G.; Li, H.; Tang, S.; Xiu, D.; Wang, J.; Yu, H.; Cheng, K.; Huang, Y.; Zhou, J. The Discharge Performance of Mg-3In-xCa Alloy Anodes for Mg–Air Batteries. Coatings 2022, 12, 428.)

[0054] Comparative Example 4

[0055] A Mg-Al-In alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 6 wt.% Al; 1 wt.% In; the remainder being magnesium and unavoidable impurities.

[0056] Prepare a crucible free from leaks and other defects that could affect its use. Add high-purity magnesium ingots, high-purity indium ingots, and high-purity aluminum ingots to a low-carbon steel crucible, purge with argon gas for protection, and raise the heating temperature to 720℃ to melt the raw materials in a vacuum. After stirring, skim off any scum from the surface of the molten alloy and pour it into a preheated crucible to form a cylindrical ingot. (Yaqiong Li, Jingling Ma, Guangxin Wang, Fengzhang Ren, Yujie Zhu, Yongfa Song, Jingli Zhang. Effect by adding Ce and In to Mg–6Al Alloy as anode on performance of Mg-air batteries. Materials Research Express 2019, 6, 066315.)

[0057] Comparative Example 5

[0058] A Mg-Al-In-Ce alloy anode material for magnesium-air batteries is formulated with the following chemical composition by mass percentage: 6 wt.% Al; 1 wt.% In; 1 wt.% Ce, with the remainder being magnesium and unavoidable impurities.

[0059] Prepare a crucible, ensuring it is free from leaks and defects that could affect its use. Fill the crucible with a mixture of CO2 and SF6 as a protective gas, with SF6 comprising 5% by volume. Add high-purity magnesium ingots, high-purity indium ingots, high-purity aluminum ingots, and magnesium-cerium master alloy to the low-carbon steel crucible. Increase the heating temperature to 720°C to melt the raw materials into a molten state. After stirring, skim off the slag from the surface of the alloy liquid and pour it into the preheated crucible to form a cylindrical ingot.

[0060] Figure 1 Metallographic optical microscope and electron microscope images of the homogeneous Mg-Ca-Sn-In alloys prepared in Examples 1-3, wherein, Figure 1 (a) is a metallographic optical microscope image of the alloy in Example 1. Figure 1 (b) is a metallographic optical microscope image of the alloy in Example 2. Figure 1 (c) is a metallographic optical microscope image of the alloy of Example 3, showing that as the In content increases, the grain size gradually decreases, which is beneficial to enhancing electrochemical activity. Figure 1 (a1) is an electron microscope image of the alloy in Example 1. Figure 1 (b1) is an electron microscope image of the alloy in Example 2. Figure 1(c1) is an electron microscope image of the alloy in Example 3. It can be seen that the elongated Mg2Ca phase is distributed along the grain boundaries, and the granular Mg2Ca and CaMgSn phases are dispersed in the anode matrix.

[0061] Figure 2 The alloys of Examples 1-3 were tested at 2mA cm. -2 and 40mA cm -2 Electron micrographs of the anode surface after discharge at current density, in which Figure 2 (a) Example 1 at 2mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (b) Example 2 at 2mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (c) Example 3 at 2mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (d) is Example 1 at 40mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (e) Example 2 at 40mA cm -2 Electron microscope images of the anode surface after discharge at current density. Figure 2 (f) Example 3 at 40mA cm -2 Electron micrographs of the anode surface after discharge at current density show that the smooth pores are a second phase that promotes the discharge dissolution of the anode matrix, and that the In / Sn interface modification promotes the uniform dissolution of the anode material, resulting in a flat discharge morphology.

[0062] The discharge current, average operating voltage, and anode efficiency of the anode materials in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1. Examples 1-3 exhibited excellent discharge performance. In Comparative Example 1, only the cathode second phase Ca2Mg6Zn3 promoted the matrix discharge dissolution, but the discharge interface was not optimized, resulting in only average discharge performance. In Comparative Examples 2 and 3, only the Mg2Ca anode second phase was present, without the distribution of the CaMgSn cathode second phase or the interface modification effect of Sn, resulting in lower anode efficiency, thus indicating that In is suitable for composite alloying with Ca and Sn. In Comparative Examples 4-5, Al mainly formed Mg... 17 The Al2 and Ce-containing cathode second phase, lacking the role of Ca, exhibit poor discharge performance.

[0063] Table 1

[0064]

[0065] In summary, this invention addresses the severe hydrogen evolution and anodic polarization problems of magnesium-air battery anode materials during discharge. It prepares a Mg-Ca-Sn-In anode material with excellent discharge performance through Ca, Sn, and In alloying casting and heat treatment processes. The raw material cost is low, the preparation process is simple and scalable, and the data are accurate and detailed. By modifying the Sn / In interface and optimizing the type of the second phase, the hydrogen evolution side reaction during discharge is effectively mitigated, and uniform dissolution and discharge of the anode material are promoted, resulting in excellent discharge performance (e.g., 1.5356 V, 1930.49 mWh g). -1 10mA cm -2 ).

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this invention, and these modifications or substitutions should all be covered within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope defined in the claims.

Claims

1. A Mg-Ca-Sn-In anode material, characterized in that, The mass percentage of each metallic element in its chemical composition is as follows: Calcium 0.001 ~ 2.0 wt.%; Tin 0.001 ~ 2.0 wt.%; Indium 0.001 ~ 4.0 wt.%; Aluminum: 0.01 wt.% ~ 0.05 wt.%; Manganese: 0.01 wt.% ~ 0.05 wt.%; Zinc: 0.01 wt.% ~ 0.05 wt.%; Cerium: 0.01 wt.% ~ 0.05 wt.%; Copper: 0.01 wt.% ~ 0.05 wt.%; Zirconium: 0.01 wt.% ~ 0.05 wt.%; Silver: 0.01 wt.% ~ 0.05 wt.%; Mercury: 0.01 wt.% ~ 0.05 wt.%; Gallium: 0.01 wt.% ~ 0.05 wt.%; Germanium: 0.01 wt.% ~ 0.05 wt.%; Rare earth elements: 0.01 wt.% ~ 0.05 wt.%; The total content of unavoidable impurity elements is less than 0.01 wt.%; The rest is magnesium.

2. The method for preparing the Mg-Ca-Sn-In anode material according to claim 1, characterized in that, Includes the following steps: (1) Weigh the required raw materials according to the composition ratio of Mg-Ca-Sn-In alloy, including high-purity magnesium ingot, high-purity indium ingot, magnesium-tin master alloy and magnesium-calcium master alloy. (2) After cleaning the high-purity magnesium ingot, high-purity indium ingot, magnesium-tin master alloy and magnesium-calcium master alloy, add them to the crucible, fill it with a protective atmosphere, heat and melt it into a melt, and then hold it for the first time. After that, cast it to obtain Mg-Ca-Sn-In ingot. (3) The ingot is kept warm for a second time to obtain a homogeneous Mg-Ca-Sn-In alloy, which is used as the Mg-Ca-Sn-In anode material.

3. The method for preparing the Mg-Ca-Sn-In anode material according to claim 2, characterized in that, The protective atmosphere is a mixture of gases containing SF6, nitrogen, or argon.

4. The method for preparing the Mg-Ca-Sn-In anode material according to claim 3, characterized in that, The SF6-containing mixed gas is a mixture of SF6 with carbon dioxide, sulfur dioxide, nitrogen or argon, wherein the volume percentage of SF6 is ≤10%.

5. The method for preparing the Mg-Ca-Sn-In anode material according to claim 2, characterized in that, In step (2), the temperature of the first heat preservation is 700~750℃ and the heat preservation time is 20 min.

6. The method for preparing the Mg-Ca-Sn-In anode material according to claim 2, characterized in that, In step (3), the temperature of the second heat preservation is 200~450℃, and the heat preservation time is 10~30 hours.

7. The application of the Mg-Ca-Sn-In anode material according to claim 1 or the Mg-Ca-Sn-In anode material prepared by the method according to any one of claims 2 to 6 in magnesium-air batteries.

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