Mg-sn-er anode material and preparation method and application thereof

Abstract

This invention relates to the field of air batteries and discloses a Mg-Sn-Er anode material. Its chemical composition includes tin, erbium, magnesium, and other impurities. The mass percentage of the chemical composition of this anode material is: tin 1.0-1.5%, erbium 0.5-1.0%, other impurities less than 0.01%, and the remainder being magnesium. The preparation method is as follows: under a protective atmosphere of mixed CO2 and SF6, metallic magnesium, magnesium-tin alloy, and magnesium-erbium alloy are melted at 700-720℃ to obtain an alloy liquid. When the temperature of the alloy liquid drops to 680-700℃, a refining agent is added and stirred. Subsequently, water cooling is performed to obtain an ingot. Finally, the ingot is solution treated to obtain the Mg-Sn-Er anode material. Its application is in magnesium-air batteries. The technical solution of this invention solves the problems of low discharge voltage and poor material utilization caused by the performance defects of the anode material in magnesium-air batteries.

Description

Technical Field

[0001] This invention relates to the field of air batteries, specifically to a Mg-Sn-Er anode material, its preparation method, and its application. Background Technology

[0002] Magnesium-air batteries are a new type of primary battery that uses magnesium and its alloys as the negative electrode active material and oxygen from the air as the positive electrode active material. Due to its advantages such as negative standard electrode potential, large theoretical specific capacity, and excellent overall performance in terms of theoretical discharge voltage and energy density, it has become a highly efficient, green, and safe energy storage option. During discharge, magnesium and magnesium alloys undergo oxidation at the anode, while oxygen at the air cathode is reduced to OH- with water in the electrolyte. - Ultimately, Mg(OH)2 product is formed on the surface of the magnesium anode.

[0003] However, in practical applications, this battery faces significant technical bottlenecks: on the one hand, discharge products accumulate on the anode surface, resulting in an actual discharge voltage significantly lower than the theoretical value; on the other hand, magnesium and magnesium alloys exhibit self-corrosion during discharge, and the "block effect" caused by material detachment from the matrix greatly reduces the utilization efficiency of the anode material. These problems severely hinder the application and promotion of magnesium-air batteries, and developing high-performance anode materials is a key breakthrough to improve their discharge performance. Therefore, developing an anode material that can effectively address these problems has become an urgent technical challenge. Summary of the Invention

[0004] The present invention aims to provide a Mg-Sn-Er anode material, its preparation method and application, in order to solve the problems of low discharge voltage and poor material utilization caused by the performance defects of anode materials in magnesium-air batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a Mg-Sn-Er anode material, the chemical composition of which includes tin, erbium, magnesium and other impurities, wherein the mass percentage of the chemical composition of the anode material is: tin 1.0-1.5, erbium 0.5-1.0, other impurities less than 0.01, and the remainder being magnesium.

[0006] The present invention also provides another technical solution, a method for preparing Mg-Sn-Er anode material, wherein metallic magnesium, magnesium-tin alloy and magnesium-erbium alloy are melted at 700-720℃ under a protective atmosphere of mixed CO2 and SF6 to obtain an alloy liquid, and when the temperature of the alloy liquid drops to 680-700℃, a refining agent is added and stirred, followed by water cooling to obtain an ingot, and finally the ingot is subjected to solid solution treatment to obtain Mg-Sn-Er anode material.

[0007] Preferably, the solution treatment process is as follows: the ingot is placed in a heat treatment furnace and kept at 480-500℃ for 24-26 hours, followed by water cooling treatment to obtain Mg-Sn-Er anode material.

[0008] Preferably, the refining agent is a mixture of MgCl2, KCl, BaCl2 and CaF2, with a mass ratio of (44-48):(40-44):(6-10):(2-4).

[0009] Preferably, the volume ratio of CO2 to SF6 in the mixed protective gas is (33-36):1.

[0010] Preferably, before smelting, the raw materials need to be pretreated by cutting magnesium metal, magnesium-tin alloy and magnesium-erbium alloy into small pieces and polishing them.

[0011] Preferably, after the magnesium, magnesium-tin alloy, and magnesium-erbium alloy are completely melted, slag removal and stirring are performed first, and then refining agents are added.

[0012] Compared with the existing technology, the beneficial effects of this solution are as follows: (1) By alloying with Sn and Er elements, the performance of magnesium anode materials is fundamentally improved. Sn element, with its higher hydrogen evolution overpotential, can effectively weaken the hydrogen evolution corrosion reaction during the discharge process, improve the corrosion resistance of the alloy, and an appropriate amount of Mg2Sn phase can enhance the surface electrochemical activity and improve the discharge efficiency; rare earth element Er can improve the purity of magnesium alloy, reduce the impurity content, and refine the grain size, further enhance the electrochemical activity, thereby significantly improving the discharge performance of the alloy.

[0013] (2) Adding a small amount of Er element to the Mg-Sn binary alloy not only improves the discharge performance but also effectively controls the material cost, thus balancing performance and economy.

[0014] (3) The solid solution treatment process used in the preparation process has a significant effect, which can effectively refine the grain size of the alloy, improve the content and distribution of the second phase Mg2Sn in the alloy, and form a fine and uniform network second phase structure.

[0015] (4) This structure can suppress hydrogen evolution self-corrosion and “block effect”, promote the shedding of discharge products, and thus improve discharge stability and material utilization. At a current density of 5 mA / cm², the discharge voltage reaches 1.34V and the anode utilization rate reaches 40.6%, which is significantly improved compared with traditional magnesium anode materials.

[0016] (5) The entire preparation process ensures uniform diffusion of alloying elements and avoids component segregation by precisely controlling the melting temperature, protective gas ratio and refining agent composition, thus providing process assurance for the preparation of high-performance anode materials. Attached Figure Description

[0017] Figure 1 The image shows the metallographic microstructure of the Mg-Sn-Er anode material prepared in Example 1 of this invention.

[0018] Figure 2 This is a SEM microstructure image of the Mg-Sn-Er anode material prepared in Example 1 of this invention;

[0019] Figure 3 The EIS spectrum of the Mg-Sn-Er anode material prepared in Example 1 of this invention in 3.5 wt.% NaCl electrolyte;

[0020] Figure 4 The Land cell test curve of the Mg-Sn-Er anode material prepared in Example 1 of this invention in 3.5 wt.% NaCl electrolyte. Detailed Implementation

[0021] The following detailed description illustrates the specific implementation method:

[0022] Example 1

[0023] A Mg-Sn-Er anode material has a chemical composition including tin, erbium, magnesium, and other impurities. The mass percentage of the chemical composition of the anode material is: tin 1.0-1.5, erbium 0.5-1.0, other impurities less than 0.01, and the remainder being magnesium. Other impurities include Fe, Ni, Al, and Mn, etc. In this embodiment, the mass percentage of the chemical composition of the anode material is: tin 1.5, erbium 1.0, other impurities less than 0.01, and the remainder being magnesium.

[0024] A method for preparing Mg-Sn-Er anode material, the specific steps of which are as follows:

[0025] S1: Raw material pretreatment: Magnesium metal, magnesium-tin alloy, and magnesium-erbium alloy are cut into small pieces and polished. After polishing, 875g of magnesium blocks, 75g of magnesium-tin alloy, and 50g of magnesium-erbium alloy are weighed out for later use, ensuring that the surface of the raw materials is clean and free of oxide layer. In this embodiment, magnesium blocks are used for magnesium metal, Mg-20Sn is used for magnesium-tin alloy, and Mg-20Er is used for magnesium-erbium alloy. The purity of magnesium blocks is 99.99%, the purity of Mg-20Sn is 99.99%, and the purity of Mg-20Er is 99.99%.

[0026] S2: Crucible preparation: Check the new crucible for holes and impurities, and confirm its dryness; after confirming that the crucible has no external defects, put it in a drying oven and preheat it at 200℃ for 30 minutes; take out the preheated crucible, clean its interior, and then evenly coat the inner wall of the crucible with a layer of boron nitride alcohol solution, with a mass ratio of boron nitride to alcohol of 1:4.

[0027] S3: Alloy Smelting: During the entire smelting process, a mixed protective gas of CO2 and SF6 is introduced, with a volume ratio of CO2 to SF6 of (33-36):1. The furnace temperature is raised to 700-720℃. First, 875g of magnesium blocks are added and held for 40 minutes until they are completely melted. Then, 75g of Mg-20Sn and 50g of Mg-20Er are added sequentially and held for 60 minutes to allow other alloying elements to diffuse fully and homogenize the alloy. In this embodiment, the volume ratio of CO2 to SF6 in the mixed protective gas is 35:1, and the furnace temperature is raised to 720℃.

[0028] S4: Slag Removal and Refining: After confirming that all alloys in the crucible are completely melted, slag removal and stirring are performed using a spoon coated with boron nitride alcohol solution. Protective gas must be continuously introduced during this process. After slag removal and stirring, the furnace temperature is lowered to 690-700℃, 20g of refining agent is added, and the alloy liquid is vigorously stirred with a stirring rod at the same time. The entire process is maintained for 2 minutes. The crucible is then removed, and the alloy liquid is water-cooled to obtain an ingot. The refining agent is a mixture of MgCl2, KCl, BaCl2 and CaF2, with a mass ratio of (44-48):(40-44):(6-10):(2-4). In this embodiment, the furnace temperature is lowered to 700℃; the mass ratio of MgCl2, KCl, BaCl2 and CaF2 is 46:43:8:3.

[0029] S5: Solution treatment: Solution treatment is performed using a heat treatment furnace. The heat treatment furnace is heated to 480-500℃, and the ingot is placed in the heated heat treatment furnace and held for 24-26 hours. After the holding period, the ingot is removed and water-cooled to finally obtain the Mg-Sn-Er anode material, denoted as Mg-1.5Sn-1Er. In this embodiment, the heat treatment furnace is heated to 500℃ and held for 24 hours.

[0030] An application of a Mg-Sn-Er anode material in magnesium-air batteries.

[0031] Example 2

[0032] Unlike Example 1, in a method for preparing a Mg-Sn-Er anode material, in S1, 900g of magnesium block, 75g of Mg-20Sn and 25g of Mg-20Er are weighed after grinding, and the Mg-Sn-Er anode material obtained in S5 is denoted as Mg-1.5Sn-0.5Er.

[0033] Comparative Example 1

[0034] Unlike Example 1, in a method for preparing a Mg-Sn-Er anode material, in S1, after grinding, 950g of magnesium block and 50g of Mg-20Er are weighed, without adding Mg-20Sn, and the Mg-Sn-Er anode material obtained in S5 is denoted as Mg-1Er.

[0035] Comparative Example 2

[0036] Unlike Example 1, in a method for preparing a Mg-Sn-Er anode material, in S1, after grinding, 925g of magnesium block and 75g of Mg-20Sn are weighed, without adding Mg-20Er. The Mg-Sn-Er anode material obtained in S5 is denoted as Mg-1.5Sn.

[0037] Comparative Example 3

[0038] Unlike Example 1, the preparation method of a Mg-Sn-Er anode material does not include S5 and does not perform solid solution treatment on the ingot.

[0039] Metallographic microstructure analysis was performed on the Mg-Sn-Er anode material prepared in Example 1. Figure 1 It can be seen that the Mg-Sn-Er anode material prepared in Example 1 has a small grain size.

[0040] The Mg-Sn-Er anode material prepared in Example 1 was subjected to SEM microstructure analysis. Figure 2 It can be seen that the white substance is the second phase Mg2Sn, which is uniformly distributed in a network on the surface, and the second phase is even finer after solid solution treatment.

[0041] The Mg-Sn-Er anode material prepared in Example 1 was subjected to EIS testing in a 3.5 wt.% NaCl electrolyte. Figure 3 It can be seen that the alloy exhibits a large capacitive arc diameter, indicating that it has high corrosion resistance in NaCl solution, and thus has a weak self-corrosion reaction during discharge, which can effectively improve discharge efficiency.

[0042] The Mg-Sn-Er anode materials prepared in Examples 1-2 and Comparative Examples 1-3 were assembled into magnesium-air batteries, and their discharge performance was tested.

[0043] The assembly process of the magnesium-air battery is illustrated using Example 1 as an example. The assembly methods of Examples 2 and Comparative Examples 1-3 are the same as those of Example 1 and will not be repeated. The specific assembly process is as follows: using the Mg-Sn-Er anode material prepared in Example 1 as the metal anode (working area 1 cm²). 2 A magnesium-air battery was assembled using commercially available air cathodes and a 3.5 wt.% NaCl solution as the electrolyte.

[0044] At a discharge current density of 5 mA / cm 2 Performance testing will be conducted under the following circumstances. Figure 4 It can be seen that the Mg-1.5Sn-1Er alloy prepared in Example 1 exhibited a brief drop in discharge voltage at the beginning of the discharge process, but subsequently showed stable discharge performance throughout the entire discharge process at a current density of 5 mA / cm². 2 The discharge voltage is 1.34V, and the anode utilization rate is 40.6%.

[0045] The Mg-1.5Sn-1Er alloy prepared in Example 1 was used as the anode material, and its performance was tested under different discharge current densities. The results are shown in Table 1.

[0046] Table 1

[0047]

[0048] Using the Mg-Sn-Er anode materials prepared in Examples 1-2 and Comparative Examples 1-3 as anode materials, the discharge current density was 5 mA / cm². 2 Performance tests were conducted under these conditions, and the results are shown in Table 2.

[0049] Table 2

[0050]

[0051] As can be seen from Table 2, at 5 mA / cm 2 At the discharge current density, the Mg-Sn-Er anode materials prepared in Examples 1-2 all exhibited excellent discharge performance. Among them, the Mg-1.5Sn-1Er alloy after solid solution treatment showed better discharge voltage and anode efficiency than other alloys.

[0052] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a Mg-Sn-Er anode material, characterized in that: The chemical composition of a Mg-Sn-Er anode material includes tin, erbium, magnesium and other impurities. The mass percentage of the chemical composition of the anode material is: tin 1.0-1.5, erbium 0.5-1.0, other impurities less than 0.01, and the remainder is magnesium. Under a protective atmosphere of mixed CO2 and SF6, magnesium, magnesium-tin alloy and magnesium-erbium alloy are melted at 700-720℃ to obtain an alloy liquid. When the temperature of the alloy liquid drops to 680-700℃, a refining agent is added and stirred. Then, water cooling is performed to obtain an ingot. Finally, the ingot is solution treated to obtain Mg-Sn-Er anode material. The solution treatment process is as follows: the ingot is placed in a heat treatment furnace and kept at 480-500℃ for 24-26 hours. Then, water cooling is performed to obtain Mg-Sn-Er anode material.

2. The method for preparing a Mg-Sn-Er anode material according to claim 1, characterized in that: The refining agent is a mixture of MgCl2, KCl, BaCl2 and CaF2, with a mass ratio of (44-48): (40-44): (6-10): (2-4).

3. The method for preparing a Mg-Sn-Er anode material according to claim 2, characterized in that: The volume ratio of CO2 to SF6 in the mixed protective gas is (33-36):

1.

4. The method for preparing a Mg-Sn-Er anode material according to claim 3, characterized in that: Before smelting, the raw materials need to be pre-treated by cutting magnesium metal, magnesium-tin alloy and magnesium-erbium alloy into small pieces and polishing them.

5. The method for preparing a Mg-Sn-Er anode material according to claim 4, characterized in that: After the magnesium, magnesium-tin alloy, and magnesium-erbium alloy are completely melted, slag removal and stirring are carried out first, and then refining agents are added.

6. An application of a Mg-Sn-Er anode material, characterized in that: The Mg-Sn-Er anode material prepared by the method according to any one of claims 1-5 is applied in magnesium-air batteries.

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