Aluminum alloy electrode material and method for manufacturing the same

Abstract

The application discloses an aluminum alloy electrode material and a preparation method thereof. Raw materials of the aluminum alloy electrode material include magnesium, tin, indium and aluminum. The preparation method of the aluminum alloy electrode material comprises the following steps: melting the raw materials to obtain aluminum alloy ingots according to mass percentage; performing heat treatment on the aluminum alloy ingots; performing rolling on the aluminum alloy ingots after the heat treatment; and obtaining aluminum alloy electrode plates with a target thickness. The aluminum alloy electrode material adopts specific alloy components, alloy proportions and a processing process to alloy the metal aluminum, so that the aluminum alloy electrode material has higher discharge voltage and higher electrode utilization rate when used in an aluminum alloy battery, the occurrence of a side reaction is reduced, the discharge energy of a unit mass electrode is improved when the aluminum alloy electrode is used, and the aluminum alloy electrode plate has better processing consistency compared with the same type of aluminum alloy electrode plate.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloys, and specifically relates to an aluminum alloy electrode material and its preparation method. Background Technology

[0002] An aluminum-air battery consists of an air electrode, an aluminum electrode, and an electrolyte. In most aluminum-air batteries, the aluminum exists in the form of metal sheets, which are made into flat plates of different sizes and thicknesses according to the energy requirements of the battery.

[0003] Aluminum has a high theoretical specific energy, and its gravimetric specific capacity is second only to lithium (3.68 Ah / g) among all metals, reaching 2.98 Ah / g. Its theoretical volumetric specific capacity is the highest among all metals, reaching 8.05 Ah / g. However, under actual conditions, aluminum's performance differs significantly from its theoretical values. Metallic aluminum readily undergoes oxidation on its surface, forming a firmly adhered and highly dense oxide film that isolates the medium from the internal aluminum, thus passivating it and causing a large difference between the electrode potential and the theoretical value. Even the products of the reaction on the surface of metallic aluminum can further react with an alkaline medium to form AlO. 2- However, severe polarization occurs during the reaction, accompanied by severe hydrogen evolution corrosion, which greatly affects the actual electrode potential of aluminum. Furthermore, the coulombic efficiency of the aluminum anode is significantly reduced, leading to decreased material utilization. The corrosion byproduct of the hydrogen evolution reaction is H2, and as the reaction continues, a large amount of hydrogen accumulates, posing a safety hazard to the battery's application.

[0004] Alloying is a fundamental method for improving the performance of aluminum electrodes. Through continuous research, various methods for preparing aluminum alloys for aluminum-air batteries have been publicly disclosed, and the alloying components are diverse. For example, the BDW (Al.1%Mg0.1%In0.2%Mn) aluminum alloy anode developed by Maimoni et al. showed an open-circuit voltage of 1.78V (VS.He / HgO) and an open-circuit corrosion rate of 0.029 mg / cm³ in a 4 mol / L NaOH + 1 mol / L Al(OH)₃ solution at 60℃. 2 The pentaluminum alloy developed by Shi Pengfei et al. exhibits a very low corrosion rate in alkaline solutions, with an anodic potential of -1.642V (vs Hg / HgO). Southwest Aluminum (Group) Co., Ltd., in collaboration with Wuhan 712 Institute, successfully developed a series of high-performance Al.Ga-Bi.Pb aluminum anode materials. These materials demonstrate excellent electrochemical performance in neutral solutions, but their performance in alkaline solutions is slightly inferior to that of Al.In.Mg alloys. The Al.Pb.In.Ga and Al.Pb.In.Ga.Mg series aluminum alloy anodes developed by Ma Zhengqing et al. of Central South University exhibit a current density of 80 mA / cm² in a 25% KOH + 3.5% NaCl medium.2 Under polarization conditions, the stable electrode potentials can reach 1.35V and -1.45V (vs Hg / HgO), respectively.

[0005] Of these publicly disclosed manufacturing processes, few are truly commercially viable. Due to the specific nature of electrode applications, alloyed aluminum electrodes exhibit significant drawbacks in processing performance. Compared to aluminum alloys used in other industries, aluminum alloys for aluminum-air batteries often suffer from poor processing performance, for several reasons:

[0006] (1) Low melting point alloys suffer severe burn-off during processing, which can easily lead to the formation of intergranular inclusions, making the electrodes prone to cracking during the later rolling process.

[0007] (2) Most of the alloying elements added to aluminum alloy electrodes are high-density, low-melting-point metals that are immiscible with aluminum. Therefore, they are prone to compositional segregation, dendrite segregation and density segregation, resulting in uneven internal quality of aluminum electrodes and difficulty in guaranteeing the quality of the same batch.

[0008] (3) The alloy composition itself leads to high hardness and poor toughness of aluminum electrodes, and the performance of most alloy components is affected after hot rolling, making them difficult to process. Summary of the Invention

[0009] This invention aims to address the shortcomings of existing technologies by providing an aluminum alloy electrode material and its preparation method. This aluminum alloy electrode material employs specific alloy compositions, alloy ratios, and processing procedures to alloy metallic aluminum. The alloy composition ensures high performance, resulting in higher discharge voltage and higher electrode utilization when used in aluminum alloy batteries, while reducing the occurrence of side reactions. Furthermore, it exhibits better processing consistency compared to similar aluminum alloy electrode plates.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] An aluminum alloy electrode material is composed of the following raw materials in weight percentages: 1%–5% magnesium, 0.05%–0.25% tin, 0.05%–0.2% indium, with the balance being aluminum;

[0012] Preferably, in the above technical solution, the aluminum alloy electrode material is composed of the following raw materials in mass percentage: 2%–3% magnesium, 0.05%–0.25% tin, 0.05%–0.2% indium, with the balance being aluminum;

[0013] Preferably, in the above technical solution, the aluminum alloy electrode material is composed of the following raw materials in mass percentage: magnesium 1% to 5%, tin 0.1% to 0.2%, indium 0.05% to 0.2%, and the balance being aluminum;

[0014] Preferably, in the above technical solution, the aluminum alloy electrode material is composed of the following raw materials in mass percentage: 2% to 3% magnesium, 0.1% to 0.2% tin, 0.05% to 0.2% indium, and the balance being aluminum.

[0015] Voltage level and corrosion rate are the main indicators of aluminum alloy electrodes, and their alloy composition and preparation process are important factors that determine their performance.

[0016] This invention proposes a quaternary alloy formulation, in which magnesium, tin, and indium are used to alloy metallic aluminum to achieve better performance. Magnesium, an alloying element, has a more negative potential than aluminum, which can shift the potential negative and improve the corrosion resistance of the aluminum electrode. However, excessive magnesium will form Mg2Al3, which not only increases the corrosion current density but also reduces electrochemical activity. After optimization, the mass percentage of magnesium in this invention is 1%-5%, more preferably 2%-3%.

[0017] The added tin can disrupt the compactness of the aluminum oxide film, increase additional vacancies, and reduce the resistance of the oxide film, thereby increasing the discharge voltage of the electrode. However, tin can also easily form segregated phases at grain boundaries, leading to increased corrosion. Preferably, the mass percentage of tin in this invention is 0.05%-0.25%, more preferably 0.1%-0.2%.

[0018] Indium, an alloying element, is a low-melting-point compound that can form a eutectic mixture at relatively low operating temperatures (60–100°C). This disrupts the stable and dense oxide film on the aluminum surface, thus acting to destroy and peel off the oxide film, thereby making the voltage more negative. However, excessive indium can increase the self-corrosion of the electrode. After optimization, the indium mass percentage in this invention is 0.05%–0.2%.

[0019] The three alloying elements work together to ensure that the aluminum alloy electrode possesses both high voltage and low self-corrosion current, exhibiting excellent performance. The performance significantly decreases when any one of the components is missing or its content is outside the range specified in this invention.

[0020] This invention optimizes and limits the composition and content of each component of the aluminum alloy. The aluminum alloy with this composition can ensure high performance, enabling the aluminum alloy electrode plate to have a higher discharge voltage and higher electrode utilization when used in aluminum alloy batteries, reducing the occurrence of side reactions, thereby improving the discharge energy per unit mass of electrode when the aluminum alloy electrode is used.

[0021] Based on the same inventive concept, the present invention also provides a method for preparing an aluminum alloy electrode material, comprising the following steps:

[0022] S1: Heat aluminum to 680-700℃ to obtain molten aluminum liquid;

[0023] S2: Add magnesium, tin and indium to the molten aluminum and stir until homogeneous;

[0024] S3: Perform one or two slag removal processes;

[0025] S4: After heating the molten aluminum liquid to 700-720℃, it is cast into aluminum alloy ingot A;

[0026] S5: Heat aluminum alloy ingot A to 400-450℃, hold for 8-10 hours, and then cool it to room temperature in the air.

[0027] S6: Roll aluminum alloy ingot A to 30% to 40% of A.

[0028] Furthermore, the aluminum alloy ingot rolling process is completed through multiple rolling operations. The feed rate for the first to third rolling operations is 6.5 to 7.5% of A, and the feed rate for the fourth to eighth rolling operations is 3.5 to 4.5% of A.

[0029] Preferably, the feed rate for the first to third rolling passes is 7% of A, and the feed rate for the fourth to eighth rolling passes is 4% of A.

[0030] Furthermore, the first slag removal is followed by standing and keeping warm for 10-20 minutes, and the first slag removal is followed by standing and keeping warm for 5-10 minutes.

[0031] Preferably, the thickness of aluminum alloy ingot A is 1-3 cm.

[0032] There are certain difficulties in the preparation of aluminum alloy electrode plates: (1) Low melting point alloys are easily burned during melting and can easily produce intergranular inclusions; (2) Raw materials need to be stirred thoroughly to achieve uniformity. Inhomogeneity can easily lead to compositional segregation, dendrite segregation and specific gravity segregation. If the stirring time is too long, the aluminum electrode will be burned. Therefore, the holding time and stirring and standing time of alloy melting are critical. If the melting temperature is too high or too low, or the stirring and standing time is too long or too short, the alloy quality will be poor; (3) The alloy composition itself leads to high hardness and poor toughness of aluminum electrodes. However, a certain amount of deformation is required during processing to ensure good performance. Hot rolling will lead to a decrease in performance. Therefore, it is critical to select the appropriate amount of pressing and the pressing process.

[0033] In addition to defining the composition of the aluminum alloy, this invention also studies the key elements of the aluminum alloy preparation process, refines and improves the aluminum alloy preparation process and the control of process parameters at each step, controls the heat preservation and stirring time of melting, and solves the problem that aluminum alloys are prone to forming compositional segregation, dendrite segregation and specific gravity segregation, which leads to uneven internal quality of aluminum alloy electrode plates and large differences in the performance of electrodes in the same batch, thus ensuring the reliability of production and processing.

[0034] This invention balances the contradictions between long melting time, alloy component burn-off, and numerous inclusions in the alloy plate, and short capacity time, resulting in unevenness within the alloy, through various adjustments to the process.

[0035] Aluminum alloy sheets are prone to cracking during rolling, which is controlled by adjusting the feed rate and total pressure. Lower feed rates and pressures can prevent cracking during rolling, but to ensure performance, sufficient deformation is required to achieve good results; therefore, the feed rate and pressure cannot be too low. Compared to existing processes, this invention provides strict control over the feed rate and pressure.

[0036] This invention addresses the problem of poor miscibility between alloy components and aluminum by enhancing the stirring and slag removal processes during smelting, compared to existing technologies. The melting and casting temperatures of the aluminum alloy are controlled at 680-700℃ and 700-720℃, respectively, which is beneficial for the uniformity of the aluminum alloy and reduces the burn-off of alloy components.

[0037] The duration of heat preservation and stirring is also crucial to ensuring the performance of aluminum alloy materials. Research has determined that the holding time before the first slag removal should be 10-20 minutes, and the holding time after the first slag removal should be 5-10 minutes. In S5, the aluminum alloy ingot is heated to 400-450℃ and then held for 8-10 hours.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. This aluminum alloy electrode material optimizes the alloy composition and the content of each component, resulting in higher discharge voltage and higher electrode utilization when used in aluminum alloy batteries, reducing the occurrence of side reactions, thereby increasing the discharge energy per unit mass of the aluminum electrode when in use.

[0040] 2. Based on the high-quality requirements of alloy electrodes, the aluminum alloy smelting process and the control of process parameters at each step were refined and improved, which solved the problem of uneven internal quality of alloy plates used for this type of electrode and large performance differences of electrodes in the same batch.

[0041] 3. This invention strictly controls the feed rate and the amount of pressure applied to ensure that the aluminum alloy does not crack during the rolling process, thus guaranteeing the reliability of production and processing and the performance of the aluminum alloy.

[0042] 4. This aluminum alloy electrode material has a simple manufacturing process, good processing performance, and stable quality, and has better processing consistency compared with similar aluminum alloy electrode materials. Attached Figure Description

[0043] Figure 1 This is a flowchart illustrating the fabrication process of the aluminum alloy electrode material of this invention.

[0044] Figure 2This is a process flow diagram of aluminum alloy ingot smelting according to the present invention. Detailed Implementation

[0045] The present invention will be described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. For ease of description, the words "upper," "lower," "left," and "right" appearing below only indicate that they are consistent with the upper, lower, left, and right directions of the drawings themselves, and do not limit the structure.

[0046] Example 1

[0047] In this embodiment, the aluminum alloy electrode material comprises the following raw materials in weight percentages: magnesium 2.4%, tin 0.14%, indium 0.1%, and aluminum 97.5%;

[0048] like Figure 1 , Figure 2 As shown, the method for preparing the aluminum alloy electrode material in this embodiment is as follows:

[0049] 1000g of high-purity aluminum is placed in an induction furnace and melted at 680℃. After melting and reaching 680℃, 25g of magnesium is added and stirred evenly. Then, 1.5g of tin and 1.1g of indium are added and stirred again. The high-purity aluminum, magnesium, tin, and indium are all dried to remove surface moisture before being added to the induction furnace. After all the aluminum is added to the furnace, it is held at the desired temperature for 10 minutes for slag removal. Then, aluminum alloy refining agent is added, and the mixture is allowed to stand for 2 minutes before stirring. After stirring evenly, it is allowed to stand for another 5 minutes before a second slag removal. The temperature is then raised to 700-710℃ until uniform, and then poured into a casting mold to form a 3cm thick rectangular aluminum ingot. The resulting rectangular aluminum alloy ingot is cut into the required size and placed in a muffle furnace at 400℃ for 8-10 hours. After removal, it is placed in air to cool. The completely cooled aluminum alloy ingot is then rolled in a rolling mill. The 3cm rectangular aluminum ingot is repeatedly pressed to reduce its thickness to 1cm. The thickness is reduced by 2.1 mm each time for the first 3 pressings (7% feed rate), by 1.2 mm each time for the 4th to 8th pressings (4% feed rate), and then reduced by 0.4-0.5 mm each time thereafter.

[0050] The 1cm thick aluminum alloy electrode plate produced by this process has good surface quality, a dense cross-section with no inclusions or cracks, and exhibits uniform, smooth, and pore-free corrosion during discharge. It achieves 50mA / cm at 40℃. 2 The average discharge voltage is 1.45V when operating at the specified current density, and the utilization rate of the aluminum electrode is approximately 92%. At 60℃, the current density is 120mA / cm. 2 The average discharge voltage is 1.3V when operating at current density, and the utilization rate of the aluminum electrode is about 92%.

[0051] Example 2

[0052] In this embodiment, the aluminum alloy electrode material comprises the following raw materials in weight percentages: magnesium 2.8%, tin 0.16%, indium 0.1%, and aluminum 96%.

[0053] like Figure 1 , Figure 2 As shown, the method for preparing the aluminum alloy electrode material in this embodiment is as follows:

[0054] 2000g of high-purity aluminum is placed in an induction furnace and melted at 690℃. After melting and reaching 690℃, 60g of magnesium is added and stirred evenly. Then, 3.5g of tin and 2.5g of indium are added and stirred again. The high-purity aluminum, magnesium, tin, and indium are all dried to remove surface moisture before being added to the induction furnace. After all the aluminum is added to the furnace, it is held at the desired temperature for 15 minutes for slag removal. Then, aluminum alloy refining agent is added, and the mixture is allowed to stand for 2.5 minutes before stirring. After stirring evenly, it is allowed to stand for another 6 minutes before a second slag removal. The temperature is then raised to 710-720℃ until uniform, and then poured into a casting mold to form a 1cm thick rectangular aluminum ingot. The resulting rectangular aluminum alloy ingot is cut into the required size and placed in a muffle furnace at 450℃ for 8-10 hours. After removal, it is placed in air to cool. The completely cooled aluminum alloy ingot is then rolled in a rolling mill. The 1cm thick rectangular aluminum ingot is repeatedly pressed to reduce its thickness to 4mm. The thickness is reduced by 0.7 mm each time for the first 3 pressings (7% feed rate), the thickness is reduced by 0.4 mm each time for the 4th to 8th pressings (4% feed rate), and then reduced by 0.2-0.4 mm each time thereafter.

[0055] The 4mm thick aluminum alloy electrode plate produced by this process has good surface quality, a dense cross-section with no inclusions or cracks, and exhibits uniform, smooth, and pore-free corrosion during discharge. It achieves 50mA / cm at 40℃. 2 The average discharge voltage is 1.4V when operating at the specified current density, and the utilization rate of the aluminum electrode is approximately 90%. At 60℃, the current density is 120mA / cm. 2 When operating at current density, the average discharge voltage is 1.2V, and the utilization rate of the aluminum electrode is about 90%.

[0056] Comparative Example 1

[0057] 1000g of high-purity aluminum is placed in an induction furnace and melted at 680℃. After melting and reaching 680℃, 25g of magnesium is added and stirred evenly. Then, 1.1g of indium is added and stirred again. The high-purity aluminum, magnesium, and indium are all dried to remove surface moisture before being added to the induction furnace. After all the aluminum is added to the furnace, it is held at the desired temperature for 10 minutes for slag removal. Then, aluminum alloy refining agent is added, and the mixture is allowed to stand for 2 minutes before stirring. After stirring evenly, it is allowed to stand for another 5 minutes before a second slag removal. The temperature is then raised to 700-710℃ until uniform, and then poured into a casting mold to form a 3cm thick rectangular aluminum ingot. The resulting rectangular aluminum alloy ingot is cut into the required size and placed in a muffle furnace at 400℃ for 8-10 hours. After removal, it is placed in air to cool. The completely cooled aluminum alloy ingot is then rolled in a rolling mill. The 3cm rectangular aluminum ingot is repeatedly pressed to reduce its thickness to 1cm. The thickness is reduced by 2.1mm each time for the first 3 pressings, by 1.2mm each time for the 4th to 8th pressings, and then by 0.4-0.5mm each time thereafter.

[0058] The 1cm thick aluminum alloy electrode plate produced by this process achieves 50mA / cm at 40℃. 2 The average discharge voltage is 1.35V when operating at the specified current density, and the utilization rate of the aluminum electrode is approximately 89%. At 60℃, the current density is 120mA / cm. 2 The average discharge voltage is 1.3V when operating at current density, and the utilization rate of the aluminum electrode is about 85%.

[0059] Without the addition of tin, the voltage and utilization rate of aluminum alloy electrodes are reduced.

[0060] Comparative Example 2

[0061] 1000g of high-purity aluminum is placed in an induction furnace and melted at 720℃. After melting and reaching 720℃, 25g of magnesium is added and stirred evenly. Then, 1.5g of tin and 1.1g of indium are added and stirred again. The high-purity aluminum, magnesium, tin, and indium are all dried to remove surface moisture before being added to the induction furnace. After all the aluminum is added to the furnace, it is held at the desired temperature for 10 minutes for slag removal. Then, aluminum alloy refining agent is added, and the mixture is allowed to stand for 2 minutes before stirring. After stirring evenly, it is allowed to stand for another 5 minutes before a second slag removal. The temperature is then raised to 730-750℃ until uniform, and then poured into a casting mold to form a rectangular aluminum ingot with a thickness of 3cm. The resulting rectangular aluminum alloy ingot is cut into the required size and placed in a muffle furnace at 400℃ for 8-10 hours. After removal, it is placed in air to cool. The completely cooled aluminum alloy ingot is then rolled in a rolling mill. Due to excessively high melting and casting temperatures, the resulting aluminum alloy suffers significant burn-off from the added alloying elements and exhibits poor resistance to self-corrosion, with an absorption rate of 120 mA / cm² at 60℃. 2 When operating at current density, the utilization rate of aluminum electrodes is only about 80%.

[0062] Comparative Example 3

[0063] After obtaining a 3cm thick aluminum ingot using the same method as in Example 1, it was pressed into a 5mm thick aluminum electrode. Due to excessive deformation, significant cracking occurred when pressed to a thickness of 1cm. If pressed to a thickness of 2cm, the electrode exhibited poor resistance to self-corrosion due to the smaller deformation, reaching 120mA / cm at 60°C. 2 When operating at current density, the utilization rate of aluminum electrodes is only about 83%.

[0064] Comparative Example 4

[0065] Shortening or increasing the holding time will affect performance. For example, using the 1cm thick aluminum alloy electrode prepared in Example 2, if the holding time in S5 is only 6-7 hours, significant cracking will occur during subsequent rolling. If the holding time before the first slag removal is 5-9 minutes, segregation will occur in the subsequently rolled aluminum alloy plate, leading to excessive regional corrosion during use. This results in uneven operation of the aluminum electrode and a low overall utilization rate. Depending on the degree of segregation, some aluminum electrodes may also experience incomplete penetration and breakage during use, causing the total discharge of some aluminum plates to be significantly lower than the average.

Claims

1. An aluminum alloy electrode material, characterized in that, It is composed of the following raw materials in the following mass percentages: magnesium 2%~3%, tin 0.1%~0.2%, indium 0.1%~0.2%, with the balance being aluminum; The preparation method of the aluminum alloy electrode material includes the following steps: S1: Heat aluminum to 680-700℃ to obtain molten aluminum liquid; S2: Add magnesium, tin and indium to the molten aluminum and stir until homogeneous; S3: Perform one or two slag removal processes; S4: After heating the molten aluminum liquid to 700-720℃, it is cast into aluminum alloy ingot A; S5: Heat aluminum alloy ingot A to 400-450℃, hold for 8-10 hours, and then cool to room temperature in the air. S6: Roll aluminum alloy ingot A to 30% to 40% of A; The aluminum alloy ingot rolling process is completed through multiple rolling passes. The feed rate for the first to third rolling passes is 6.5 to 7.5% of A, and the feed rate for the fourth to eighth rolling passes is 3.5 to 4.5% of A. Before the first slag removal, let it stand and keep warm for 10-20 minutes, and after the first slag removal, let it stand and keep warm for 5-10 minutes.

2. The aluminum alloy electrode material according to claim 1, characterized in that, The feed rate for the first to third rolling passes is 7% of A, and the feed rate for the fourth to eighth rolling passes is 4% of A.

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