Mg-Sn-Er anode material and preparation method and application thereof

Abstract

The invention relates to the field of air batteries, and discloses an Mg-Sn-Er anode material which comprises the following chemical components in percentage by mass: 1.0-1.5% of tin, 0.5-1.0% of erbium, less than 0.01% of other impurities and the balance of magnesium element, the preparation method comprises the following steps: in the atmosphere of CO2 and SF6 mixed protective gas, melting metal magnesium, a magnesium-tin alloy and a magnesium-erbium alloy at 700-720 DEG C to obtain an alloy liquid, adding a refining agent when the temperature of the alloy liquid is reduced to 680-700 DEG C, stirring, then carrying out water cooling treatment to obtain a cast ingot, and carrying out heat treatment on the cast ingot to obtain the magnesium-tin-magnesium-erbium-magnesium alloy. According to the application of the Mg-Sn-Er anode material, the Mg-Sn-Er anode material is applied to a magnesium air battery. According to the technical scheme, the problems of low discharge voltage, poor material utilization rate and the like caused by performance defects of the anode material of the magnesium air battery are solved.

Description

Technical Field

[0001] The present invention relates to the field of air batteries, and in particular to a Mg-Sn-Er anode material and a preparation method and application thereof. Background Art

[0002] Magnesium-air battery is a new type of primary battery with magnesium and its alloys as negative electrode active materials and oxygen in the air as positive electrode active materials. It has become an efficient, green and safe energy storage option due to its advantages such as negative standard electrode potential, large theoretical specific capacity, and excellent comprehensive performance of theoretical discharge voltage and energy density. During the discharge process, magnesium and magnesium alloys undergo oxidation reaction at the anode, and oxygen at the air cathode reacts with water in the electrolyte to generate OH - , and finally form Mg(OH)2 product on the surface of magnesium anode.

[0003] However, in practical applications, this battery faces significant technical bottlenecks: on the one hand, discharge products accumulate on the anode surface, causing the actual discharge voltage to be significantly lower than the theoretical value; on the other hand, magnesium and magnesium alloys exhibit self-corrosion during the discharge process, and the "block effect" caused by the material detaching from the matrix greatly reduces the utilization efficiency of the anode material. These problems have seriously hindered the application and promotion of magnesium-air batteries, and the development of high-performance anode materials is a key breakthrough in improving their discharge performance. Based on this, the development of an anode material that can effectively improve the above-mentioned problems has become a technical challenge that needs to be solved urgently. Summary of the Invention

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

[0005] To achieve the above-mentioned object, the present invention adopts the following technical solution: a Mg-Sn-Er anode material, whose chemical composition includes tin, erbium, magnesium and other impurities. The chemical composition weight percentage of the anode material is: tin 1.0-1.5, erbium 0.5-1.0, other impurities less than 0.01, and the rest is magnesium.

[0006] The present invention also provides another technical solution, a method for preparing a Mg-Sn-Er anode material, comprising melting metallic magnesium, a magnesium-tin alloy, and a magnesium-erbium alloy at 700-720°C in a mixed protective gas atmosphere of CO2 and SF6 to obtain an alloy liquid, adding a refining agent when the alloy liquid temperature drops to 680-700°C, and stirring, followed by water cooling to obtain an ingot, and finally subjecting the ingot to a solid solution treatment to obtain the Mg-Sn-Er anode material.

[0007] Preferably, the solution treatment process is: placing the ingot into a heat treatment furnace, keeping the temperature at 480-500° C. for 24-26 hours, and then performing water cooling to obtain the Mg-Sn-Er anode material.

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

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

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

[0011] Preferably, after the metallic magnesium, magnesium-tin alloy and magnesium-erbium alloy are completely melted, slagging and stirring operations are first performed, and then the refining agent is added.

[0012] Compared with the existing technology, the beneficial effects of this scheme are as follows: (1) Through the alloying design of Sn and Er elements, the performance of magnesium anode materials is fundamentally improved. The Sn element can effectively weaken the hydrogen evolution corrosion reaction during the discharge process due to its higher hydrogen evolution overpotential, improve the corrosion resistance of the alloy, and the appropriate amount of Mg2Sn phase can enhance the surface electrochemical activity and improve the discharge efficiency; the rare earth element Er can improve the purity of the 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, taking into account both performance and economy.

[0014] (3) The solution treatment process used in the preparation process has a significant effect, which can effectively refine the alloy grain size, 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 inhibit hydrogen evolution self-corrosion and the "block effect", promote the shedding of discharge products, and thus improve discharge stability and material utilization. At a current density of 5mA / cm², the discharge voltage reaches 1.34V and the anode utilization rate reaches 40.6%, which is a significant improvement over the performance of traditional magnesium anode materials.

[0016] (5) The entire preparation process ensures uniform diffusion of alloy elements and avoids component segregation by precisely controlling the melting temperature, protective gas ratio and refining agent composition, providing process guarantee for the preparation of high-performance anode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a metallographic microstructure diagram of the Mg-Sn-Er anode material prepared in Example 1 of the present invention; Figure 2 This is a SEM microstructure image of the Mg-Sn-Er anode material prepared in Example 1 of the present invention; Figure 3 This is the EIS spectrum of the Mg-Sn-Er anode material prepared in Example 1 of the present invention in 3.5 wt.% NaCl electrolyte; Figure 4 This is a Land cell test curve of the Mg-Sn-Er anode material prepared in Example 1 of the present invention in 3.5 wt.% NaCl electrolyte. DETAILED DESCRIPTION

[0018] The following is further described in detail through specific implementation methods: Example 1 A Mg-Sn-Er anode material, whose chemical composition includes tin, erbium, magnesium and other impurities. The chemical composition weight percentage 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. Other impurities include Fe, Ni, Al and Mn. In this embodiment, the chemical composition weight percentage of the anode material is: tin 1.5, erbium 1.0, other impurities less than 0.01, and the remainder is magnesium.

[0019] A method for preparing a Mg-Sn-Er anode material, the specific steps are as follows: 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 block, 75g of magnesium-tin alloy, and 50g of magnesium-erbium alloy are weighed and set aside. Ensure that the raw material surfaces are clean and free of oxide layer. In this embodiment, magnesium metal is magnesium block, magnesium-tin alloy is Mg-20Sn, and magnesium-erbium alloy is Mg-20Er. The purity of magnesium block is 99.99%, the purity of Mg-20Sn is 99.99%, and the purity of Mg-20Er is 99.99%. S2: Crucible preparation: Check the new crucible for holes and impurities and confirm its dryness. After confirming that the crucible has no external defects, place it in a drying oven and preheat it at 200°C for 30 minutes. Remove the preheated crucible, clean its interior, and then evenly apply a layer of boron nitride alcohol solution on the inner wall of the crucible. The mass ratio of boron nitride to alcohol is 1:4. S3: Alloy smelting: During the entire smelting process, a mixed protective gas of CO2 and SF6 is introduced, and the volume ratio of CO2 and SF6 in the mixed protective gas is (33-36):1. The temperature of the smelting furnace is raised to 700-720°C, and 875g of magnesium blocks are first added and kept warm for 40 minutes. After they are completely melted, 75g of Mg-20Sn and 50g of Mg-20Er are added in sequence and kept warm for 60 minutes to allow other alloy elements to fully diffuse and make the alloy composition uniform. In this embodiment, the volume ratio of CO2 and SF6 in the mixed protective gas is 35:1, and the temperature of the smelting furnace is raised to 720°C. S4: slag removal and refining treatment: After confirming that all the alloys in the crucible are completely melted, use a spoon coated with boron nitride alcohol solution to perform slag removal and stirring operations. Protective gas must be continuously introduced during this process. After slag removal and stirring, the furnace temperature is lowered to 690-700°C, 20g of refining agent is added, and the alloy liquid is vigorously stirred with a stirring rod. The whole process is maintained for 2 minutes. The crucible is taken out and the alloy liquid is water-cooled to obtain an ingot. The refining agent is a mixture of MgCl2, KCl, BaCl2 and CaF2, and the mass ratios thereof are (44-48): (40-44): (6-10): (2-4). In this embodiment, the furnace temperature is lowered to 700°C; the mass ratios of MgCl2, KCl, BaCl2 and CaF2 are 46:43:8:3. S5: Solution treatment: A heat treatment furnace is used for solution treatment, the heat treatment furnace is heated to 480-500°C, the ingot is placed in the heated heat treatment furnace, and kept warm for 24-26 hours; after the insulation is completed, the ingot is taken out and water-cooled to finally obtain the Mg-Sn-Er anode material, which is recorded as Mg-1.5Sn-1Er. In this embodiment, the heat treatment furnace is heated to 500°C and kept warm for 24 hours.

[0020] The invention discloses an application of a Mg-Sn-Er anode material in magnesium-air batteries.

[0021] Example 2 Different from Example 1, a method for preparing a Mg-Sn-Er anode material is as follows: in S1, 900 g of magnesium block, 75 g of Mg-20Sn and 25 g of Mg-20Er are weighed after grinding, and the Mg-Sn-Er anode material prepared in S5 is recorded as Mg-1.5Sn-0.5Er.

[0022] Comparative Example 1 Different from Example 1, a method for preparing a Mg-Sn-Er anode material is as follows: in S1, 950 g of magnesium block and 50 g of Mg-20Er are weighed after grinding, and no Mg-20Sn is added. The Mg-Sn-Er anode material prepared in S5 is recorded as Mg-1Er.

[0023] Comparative Example 2 Different from Example 1, in a method for preparing a Mg-Sn-Er anode material, in S1, 925 g of magnesium block and 75 g of Mg-20Sn were weighed after grinding, and no Mg-20Er was added. The Mg-Sn-Er anode material prepared in S5 was recorded as Mg-1.5Sn.

[0024] Comparative Example 3 Different from Example 1, a method for preparing a Mg-Sn-Er anode material does not include S5 and does not perform solid solution treatment on the ingot.

[0025] The Mg-Sn-Er anode material prepared in Example 1 was subjected to metallographic microstructural analysis. Figure 1 It can be seen that the grain size of the Mg-Sn-Er anode material prepared in Example 1 is small.

[0026] 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 evenly distributed in a network on the surface, and the second phase becomes finer after solution treatment.

[0027] In 3.5wt.% NaCl electrolyte, EIS test was performed on the Mg-Sn-Er anode material prepared in Example 1. Figure 3 It can be seen that the alloy exhibits a larger capacitive arc diameter, indicating that it has higher corrosion resistance in NaCl solution, and thus the self-corrosion reaction is weaker during the discharge process, which can effectively improve the discharge efficiency.

[0028] The Mg-Sn-Er anode materials prepared in Examples 1-2 and Comparative Examples 1-3 were respectively assembled into magnesium-air batteries, and their discharge performance was tested.

[0029] The assembly process of the magnesium air battery is described using Example 1 as an example. The assembly methods of Example 2 and Comparative Examples 1-3 are the same as those of Example 1 and will not be described in detail. The specific assembly process is as follows: the Mg-Sn-Er anode material prepared in Example 1 is used as the metal anode (working area is 1 cm 2 ), the commercial cathode sheet is an air cathode, and the electrolyte is a 3.5wt.% NaCl solution to assemble a magnesium-air battery.

[0030] At a discharge current density of 5 mA / cm 2 Performance testing is carried out under the condition of Figure 4It can be seen that the Mg-1.5Sn-1Er alloy prepared in Example 1 has a short discharge voltage drop at the initial stage of discharge, and then shows a stable discharge performance throughout the entire discharge process. 2 The lower discharge voltage is 1.34V and the anode utilization rate is 40.6%.

[0031] The Mg-1.5Sn-1Er alloy prepared in Example 1 was used as the anode material, and performance tests were conducted at different discharge current densities. The results are shown in Table 1.

[0032] Table 1

[0033] The Mg-Sn-Er anode materials prepared in Examples 1-2 and Comparative Examples 1-3 were used as anode materials. 2 The performance test is carried out under the condition of , and the results are shown in Table 2.

[0034] Table 2

[0035] 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 have excellent discharge performance, among which the Mg-1.5Sn-1Er alloy after solution treatment shows better discharge voltage and anode efficiency than other alloys.

[0036] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A Mg-Sn-Er anode material, characterized by: Its chemical composition includes tin, erbium, magnesium and other impurities. The chemical composition of the anode material is as follows: tin 1.0-1.5, erbium 0.5-1.0, other impurities less than 0.01, and the rest is magnesium.

2. The method for preparing a Mg-Sn-Er anode material according to claim 1, wherein: In a mixed protective gas atmosphere of CO2 and SF6, metallic magnesium, magnesium-tin alloy and magnesium-erbium alloy are melted at 700-720°C to obtain alloy liquid. When the alloy liquid temperature drops to 680-700°C, a refining agent is added and stirred. Subsequently, the mixture is water-cooled to obtain an ingot, and finally the ingot is solution treated to obtain Mg-Sn-Er anode material.

3. The method for preparing a Mg-Sn-Er anode material according to claim 2, wherein: The solution treatment process is as follows: placing the ingot into a heat treatment furnace, keeping the temperature at 480-500°C for 24-26 hours, and then performing water cooling to obtain the Mg-Sn-Er anode material.

4. The method for preparing a Mg-Sn-Er anode material according to claim 3, wherein: The refining agent is a mixture of MgCl2, KCl, BaCl2 and CaF2, and the mass ratios thereof are (44-48): (40-44): (6-10): (2-4).

5. The method for preparing a Mg-Sn-Er anode material according to claim 4, characterized in that: The volume ratio of CO2 and SF6 in the mixed protective gas is (33-36):

1.

6. The method for preparing a Mg-Sn-Er anode material according to claim 5, wherein: Before smelting, the raw materials need to be pre-treated, and the magnesium metal, magnesium-tin alloy and magnesium-erbium alloy need to be cut into small pieces and polished.

7. The method for preparing a Mg-Sn-Er anode material according to claim 6, characterized in that: After the metal magnesium, magnesium-tin alloy and magnesium-erbium alloy are completely melted, slagging and stirring operations are first performed, and then refining agents are added.

8. An application of a Mg-Sn-Er anode material, characterized by: Used in magnesium-air batteries.

Images