Magnesium alloy anode material for seawater battery and preparation method thereof

Abstract

The application discloses a magnesium alloy anode material for seawater batteries and a preparation method thereof, and the magnesium alloy anode material comprises the following components in percentage by mass: Al: 5-8%, Zn: 2-5%, Nd: 0.8-2%, Mn: 0.1-0.4%, and the balance of Mg. The application discloses the preparation method of the material, and the preparation method comprises the following steps: pure Mg, Al, Zn and Mg-30% Nd are heated to 730 DEG C in proportion by using an electric resistance furnace, Mn is added in the form of an intermediate alloy, and then the mixture is stirred, placed and poured into a carbon steel mold, and finally, the poured mixture is quenched, air-cooled, and then placed in an electric resistance furnace at 380-430 DEG C for heat preservation for 48 hours. The material has the characteristics of excellent discharge performance and easy desorption of discharge products, and the preparation method is simple and easy to implement, and the processing cost is low.

Description

Technical Field

[0001] This invention relates to the field of anode materials for chemical power sources and heat treatment of metallic materials, and in particular to a magnesium alloy anode material for seawater batteries and its preparation method. Background Technology

[0002] Magnesium has a more negative electrode potential of -2.37V (relative to the standard hydrogen electrode), which is more negative than aluminum's -2.31V and Zn's -1.25V. Therefore, when magnesium alloys are used as the anode material in seawater batteries, the more negative electrode potential can provide a larger driving potential for discharge, thereby releasing a larger current, which can power the high-power applications of torpedoes. In addition, magnesium has a high theoretical capacity (2205 A.h / kg) and low density, so when used as a battery anode, it gives the battery a high gravimetric energy density, making it a more ideal anode material.

[0003] my country boasts the world's largest reserves of rare earth elements, and rare earth magnesium alloys have become a research hotspot in the field of magnesium alloys in recent years. The addition of rare earth elements can often modify magnesium alloys by altering their crystal structure. Different rare earth elements can improve the mechanical properties of magnesium alloys to varying degrees, including hardness, tensile strength, and yield strength. However, research on how rare earth elements improve the electrochemical behavior of magnesium alloys is relatively limited.

[0004] Seawater batteries are one of the main applications of magnesium alloys as power anodes. Currently, they are widely used to provide long-term, stable current for underwater facilities such as sonar buoys, life-saving equipment, and meteorological instruments, primarily using low current density discharge. While lithium-ion batteries and alkaline batteries can be used directly, these have disadvantages such as large size and weight, requiring special storage. From an economic and practical perspective, high-power-density lithium-ion or alkaline batteries are not suitable for marine equipment due to their stringent discharge environment requirements. The biggest advantage of seawater batteries is that they do not require a carrying electrolyte; they only need natural seawater as the electrolyte for activation, thus significantly improving their gravimetric energy density.

[0005] The basic working principle of seawater batteries is to achieve discharge through the corrosion of metals in seawater, providing the anode current, while a corresponding reduction reaction occurs at the cathode. The cathode reduction reaction can rely on dissolved oxygen in seawater or directly utilize dissolved oxygen from air / water on an inert electrode, or it can be achieved by the cathode itself participating in the reaction (e.g., using CuCl or AgCl as the cathode). However, magnesium alloys as anode materials also have certain drawbacks, such as the negative differential effect during anodic polarization, voltage hysteresis caused by oxides and hydroxides on the magnesium surface, and α-Mg grain desorption during discharge. Therefore, developing rare-earth magnesium alloy anode materials with negative discharge potential, high discharge stability, high current efficiency, and low processing cost is of great significance. Summary of the Invention

[0006] This invention addresses the problems of low driving potential, poor discharge stability, low current efficiency, complex manufacturing processes, and high processing costs associated with current rare-earth magnesium alloy anode materials used in seawater batteries. It discloses a magnesium alloy anode material for seawater batteries and its preparation method. This material exhibits excellent discharge performance and easy desorption of discharge products. The preparation method is simple, easy to implement, and inexpensive.

[0007] To improve discharge performance, the developed novel magnesium alloy anode material has the following alloy element mass percentages: Al: 5~8%, Zn: 2~5%, Nd: 0.8~2%, Mn: 0.1~0.4%, with the balance being Mg.

[0008] To further improve discharge performance, simplify the production process, and reduce processing costs, the magnesium alloy preparation method of this invention is as follows: Pure magnesium ingots are added to a carbon steel crucible and heated to 730°C in a resistance furnace to melt. Al, Zn, and Mn are added in proportion, with Mn added as a Mg-30%Mn master alloy and Nd as a Mg-30%Nd master alloy. After the alloy components are completely melted, the mixture is stirred for 5-10 minutes and then allowed to stand for 30-50 minutes. The upper melt is then poured into a carbon steel mold preheated to 200°C, quenched, and then naturally cooled in air.

[0009] The rare-earth magnesium alloy anode material prepared by this invention has a uniform microstructure; the dissolution kinetics of the electrode surface indicate that the product is easily desorbed; it is suitable for batteries of different power levels, exhibits stable constant current discharge performance, and the discharge potential is around -1.7V (relative to a saturated calomel reference electrode) at different current densities, with a current efficiency of nearly 80%. This magnesium alloy does not require expensive extrusion or rolling processes and can be directly used as an anode material for seawater batteries in its solution-treated state. Attached Figure Description

[0010] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0011] Figure 1 The microstructure of the magnesium alloy anode material for seawater batteries and its preparation method proposed in this invention is shown below.

[0012] Figure 2 The diagram shows the electrode surface dynamics process (a) and equivalent circuit diagrams (b) and (c) of the magnesium alloy anode material for seawater batteries and its preparation method proposed in this invention.

[0013] Figure 3 The discharge potential-time curves of the magnesium alloy anode material for seawater batteries and its preparation method proposed in this invention are shown at different current densities. Detailed Implementation

[0014] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings. Obviously, the drawings described below are only one embodiment of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings and embodiments without creative effort, and all of them fall within the protection scope of the present invention.

[0015] Specifically, this invention involves adding pure magnesium ingots to a carbon steel crucible and heating them in a resistance furnace to 730°C until melted. Then, alloy components are added in a ratio of (Al: 5-8%, Zn: 2-5%), with Mn (0.1-0.4%) added as a Mg-30%Mn master alloy and Nd (0.8-2%) added as a Mg-30%Nd master alloy. After the alloy components are completely melted, the mixture is stirred for 5-10 minutes and then allowed to stand for 30-50 minutes. The upper melt is then poured into a carbon steel mold preheated to 200°C, quenched, and allowed to cool naturally in air. The cooled magnesium alloy is then placed in a resistance furnace at 380-430°C and held for 48 hours to ensure uniform diffusion of the second phase precipitated at the grain boundaries. The magnesium alloy is then removed and quenched again in a water bath to obtain a supersaturated solid solution.

[0016] Example 1

[0017] Pure magnesium ingots were added to a carbon steel crucible and heated to 730℃ in a resistance furnace until melted. Then, alloy components were added in the following proportions: Al: 5%, Zn: 3%, Mn: 0.15%, Nd: 0.8%. After the alloy components were completely melted, the mixture was stirred for 5 minutes and then allowed to stand for 30 minutes. The upper layer of melt was poured into a carbon steel mold preheated to 200℃, quenched, and then allowed to cool naturally in air. The magnesium alloy, cooled to room temperature, was placed in a 380℃ resistance furnace and held for 48 hours. The magnesium alloy was then removed and quenched again in a water bath. The ingot was then machined into electrodes for electrochemical performance testing. The results are shown in Tables 1 and 2.

[0018] Example 2

[0019] Pure magnesium ingots were added to a carbon steel crucible and heated to 730℃ in a resistance furnace until melted. Then, alloy components were added in the following proportions: Al: 6%, Zn: 4%, Mn: 0.2%, Nd: 1.2%. After the alloy components were completely melted, the mixture was stirred for 8 minutes and then allowed to stand for 40 minutes. The upper layer of melt was poured into a carbon steel mold preheated to 200℃, quenched, and then allowed to cool naturally in air. The magnesium alloy, cooled to room temperature, was placed in a 400℃ resistance furnace and held for 48 hours. The magnesium alloy was then removed and quenched again in a water bath. The ingot was then machined into electrodes for electrochemical performance testing. The results are shown in Tables 1 and 2.

[0020] Example 3

[0021] Pure magnesium ingots were added to a carbon steel crucible and melted in a resistance furnace at 730°C. Then, alloy components were added in the following proportions: Al: 8%, Zn: 5%, Mn: 0.4%, Nd: 2%. After the alloy components were completely melted, the mixture was stirred for 10 minutes and then allowed to stand for 50 minutes. The upper layer of melt was poured into a carbon steel mold preheated to 200°C, quenched, and then allowed to cool naturally in air. The cooled magnesium alloy was then placed in a resistance furnace at 430°C and held for 48 hours. The magnesium alloy was then removed and quenched again in a water bath. The ingots were subsequently machined into electrodes for electrochemical performance testing. The results are shown in Tables 1 and 2.

[0022] Table 1. Discharge current efficiency of example alloys

[0023]

[0024] Table 2 Average Discharge Potential of Example Alloys

[0025]

[0026] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A magnesium alloy anode material for a seawater battery, characterized by, The magnesium alloy has the following mass percentage composition of alloying elements: Al: 5-8%, Zn: 5%, Nd: 2%, Mn: 0.1-0.4%, with the balance being Mg. Its preparation method includes the following steps: Pure magnesium ingots are added to a carbon steel crucible and heated to 730˚C in an electric resistance furnace to melt them. Al and Zn are added according to the mass fraction ratio. Mn is added in the form of Mg-30%Mn master alloy and Nd is added in the form of Mg-30%Nd master alloy. After the above alloy components have completely melted, stir for 5 to 10 minutes and then let stand for 30 to 50 minutes. The upper layer of molten material is poured into a carbon steel mold preheated to 200°C, quenched, and then naturally cooled in air. The magnesium alloy cooled to room temperature was placed in a resistance furnace at 380~430℃ and held for 48 hours to allow the second phase precipitated on the grain boundaries to diffuse evenly. Remove the magnesium alloy and place it in a water bath for re-quenching to obtain a supersaturated solid solution.

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