CN115874100A - A kind of magnesium-air battery negative electrode material Mg-Zn-Er alloy and its preparation method and application - Google Patents

Abstract

A magnesium-air battery negative electrode material Mg-Zn-Er alloy and a preparation method and application thereof relate to the field of magnesium-air batteries. The composition of the alloy is: Zn 0.6-20.0wt%, Er 0.1-3.5wt%, 10≥Zn/Er≥6, and the rest is magnesium. The preparation method comprises the following steps: (1) taking commercially pure magnesium, pure zinc, and Mg-Er intermediate alloy, and removing the oxide skin on the surface; (2) preheating the processed materials, and putting them into a crucible for melting; (3) ) The melt is cast in a mold and cooled to obtain a casting. By controlling the mass ratio of Zn to Er, the present invention obtains a microstructure containing quasicrystalline I phase Mg ₃ Zn ₆ Er ₁ , effectively inhibits the hydrogen evolution reaction of the magnesium negative electrode in the aqueous electrolyte solution, and accelerates the shedding of products, reducing The accumulation thickness of the discharge product on the surface of the negative electrode is improved, and the performance of the magnesium-air battery is improved.

Description

A kind of magnesium-air battery negative electrode material Mg-Zn-Er alloy and its preparation method and application

technical field

The invention relates to the technical field of magnesium-air batteries, in particular to a magnesium-air battery negative electrode material Mg-Zn-Er alloy and a preparation method and application thereof.

Background technique

The world today is facing serious resource shortages, environmental pollution and other issues, and the global energy structure is transitioning to clean energy. Developing advanced energy storage systems is one of the solutions to alleviate the energy crisis. Metal-air battery is a special type of energy storage system, which uses metal as the negative electrode active material and oxygen as the positive electrode active material. It has the advantages of low cost, light weight, safety and environmental protection, and high specific energy. Magnesium has relatively negative standard electrode potential (-2.37V vs SHE), larger theoretical specific capacity (2200mAh g ^-1 ) and power density (6800mWh g ^-1 ), smaller density (1.74g cm ^-3 ), etc. Advantages, magnesium-air batteries with magnesium or magnesium alloys as negative electrodes have received widespread attention, and have been used in emergency power supplies, special military equipment, and backup power supplies.

However, magnesium anodes suffer from severe self-corrosion in aqueous electrolytes, and the formation of discharge products during discharge hinders the contact between the magnesium anode and the electrolyte, resulting in problems such as low discharge voltage, low anode efficiency, and severe energy and capacity loss. , making its discharge performance much lower than the theoretical value, hindering the development of magnesium-air batteries and limiting their commercial development. Selecting a suitable magnesium alloy anode material is the key to solve this problem.

In view of this, we have proposed the present invention.

Contents of the invention

In view of the deficiencies and shortcomings of the prior art of magnesium-air batteries, the primary purpose of the present invention is to provide a negative electrode material Mg-Zn-Er alloy for magnesium-air batteries. When the magnesium alloy is used as the negative electrode of the magnesium-air battery, the hydrogen evolution reaction of the negative electrode during the discharge process is effectively weakened, the discharge process is optimized, the accumulation of discharge products is reduced, and the shedding of magnesium alloy particles is weakened, thereby obtaining a stable discharge voltage , improve the utilization efficiency and discharge capacity of the negative electrode, and have good discharge performance.

Another object of the present invention is to provide a method for preparing the above-mentioned Mg-Zn-Er alloy, which is a negative electrode material for a magnesium-air battery.

Another object of the present invention is to provide an application of the Mg-Zn-Er alloy as a negative electrode material for a magnesium-air battery.

The purpose of the present invention is achieved through the following technical solutions:

A magnesium-air battery negative electrode material with excellent discharge performance, the mass composition percentage of the negative electrode material: Zn 0.6-20.0wt.%, Er 0.1-3.5wt.%, the rest is magnesium and unavoidable impurities; alloy element Zn The mass ratio of /Er is Zn/Er≧6, more preferably 10≧Zn/Er≧6.

A kind of preparation method of the negative electrode material of a kind of high utilization rate magnesium-air battery provided by the present invention comprises the following steps:

(1) According to the above content Zn 2.0～8.0wt.%, Er 0.1～3.5wt.%, the rest is magnesium, Zn/Er mass ratio Zn/Er≥6, weigh commercially pure magnesium, pure zinc, Mg-Er Master alloy, and remove the oxide skin on the surface;

(2) Put the pure magnesium in (1) into a clean cast iron crucible and put them together in the hearth of a resistance furnace, preheat at 150-300°C for 10-20 minutes to remove the moisture in the crucible, pure zinc and Mg-Er Put the master alloy into another clean cast iron crucible and put it into another electric resistance furnace at a constant temperature of 250-350°C for standby;

(3) Heat up the resistance furnace with pure magnesium in (2) to 700-730°C, and pass a protective gas with a volume ratio of 19:1 (N ₂ :SF ₆ ) during the smelting process until the pure magnesium is completely melted After the melt temperature reaches 720-730°C, adjust the temperature to 730-750°C, add all the preheated Zn, keep it for 10-15 minutes, add all the preheated Mg-Er, continue to keep it for 10 minutes ~15min, then stir for 1~3min;

(4) Adjust the temperature in (3) to 710-730°C, remove the dross on the surface of the melt, take out the crucible and cast the melt into a pre-prepared metal mold, and cool it naturally after solidification to obtain the cast iron. ingot. After further cutting, a magnesium alloy negative plate is made.

The purity of the commercially pure magnesium is above 99.9%.

The composition of the Mg-Er master alloy is Mg-20wt.% Er.

The casting is carried out under a protective atmosphere, which is the same as that of the smelting process.

The application of the Mg-Zn-Er alloy obtained in the invention is used as the negative electrode material of the magnesium-air battery and directly acts on the aqueous electrolyte.

Principle of the present invention and advantage are:

(1) The addition of alloying element Zn can improve the corrosion resistance of magnesium alloys, reduce the side reaction of hydrogen evolution of magnesium alloys, and promote the uniform dissolution of magnesium alloys while shortening the battery activation time.

(2) The addition of alloying element Er can refine the grains, purify the melt, change the properties of the discharge product film, slow down the self-corrosion rate of the alloy, and improve the utilization efficiency of the magnesium anode.

When the two are added at the same time, the content of adding Zn and Er will affect the formation and distribution of the second phase of the microstructure. When the mass ratio Zn/Er≥6, especially when 10≥Zn/Er≥6, the quasicrystal I phase (Mg ₃ Zn ₆ Er ₁ ) will precipitate in the alloy. The quasicrystalline I phase is beneficial to improve the corrosion resistance of magnesium alloys, and its morphology, size, distribution and content will affect the hydrogen evolution corrosion strength and rate of magnesium alloys in aqueous solution. At the same time, the existence of phase I is beneficial to weaken the hydrogen evolution reaction, reduce the amount of negative electrode consumed by the hydrogen evolution reaction, and improve the utilization efficiency. By optimizing the content of added Zn and Er elements, I phases with different shapes, sizes, distributions and contents can be obtained, so as to achieve the purpose of regulating the microstructure and improving the discharge performance of magnesium alloys.

Compared with the prior art, the beneficial effects of the present invention are as follows:

The invention provides the application of a magnesium-air battery negative electrode material with excellent discharge performance in the magnesium-air battery through a traditional casting process.

Description of drawings

Fig. 1 is an optical microscope (OM) photo of the magnesium-air battery negative electrode material in Examples 1-4 of the present invention.

Fig. 2 is a scanning electron microscope (SEM) photo of the magnesium-air battery anode material in Examples 1-4 of the present invention.

Fig. 3 is the discharge curves of the magnesium-air battery anode materials in Examples 1 to 4 of the present invention discharged for 2 hours under the discharge currents of 1 mA cm ⁻² and 50 mA cm ⁻² respectively.

Detailed ways:

The present invention is further described in conjunction with specific examples as follows, and it is pointed out that the following examples are only used to illustrate specific implementation methods of the present invention, and cannot limit the protection scope of the present invention.

Example 1:

A magnesium-air battery negative electrode material, the mass composition percentage of the negative electrode material: Zn 2.0wt.%, Er0.25wt.%, the rest is magnesium.

(1) take by weighing commercially pure magnesium (99.99wt.%), pure zinc, Mg-20.0wt.% Er master alloy by the above-mentioned content Zn 2.0wt.%, Er 0.25wt.%, all the other being the mass percent of magnesium, and Remove the oxide skin on the surface;

(2) Put the pure magnesium in (1) into a clean cast iron crucible and put them together in the hearth of a resistance furnace, preheat at 200°C for 15min to remove the moisture in the crucible, pure zinc and Mg-20.0wt.%Er , the master alloy is put into another clean cast iron crucible and put into another electric resistance furnace at a constant temperature of 300°C for standby;

(3) Raise the temperature of the electric resistance furnace with pure magnesium in (2) to 720°C. During the smelting process, a protective gas with a volume ratio of 19:1 (N ₂ :SF ₆ ) is introduced, until the pure magnesium is completely melted. The melt temperature reaches 725°C, adjust the temperature to 730°C, add all the preheated Zn, keep it for 10 minutes, add all the preheated Mg-20.0wt.% Er, keep it for 10 minutes, and then stir for 2 minutes ;

(4) Adjust the temperature in (3) to 715°C, remove the dross on the surface of the melt, take out the crucible and pour the melt into a pre-prepared metal mold, and cool naturally after solidification to obtain an ingot.

Example 2:

A magnesium-air battery negative electrode material, the mass composition percentage of the negative electrode material: Zn 4.0wt.%, Er0.5wt.%, the rest is magnesium.

(1) take by weighing commercially pure magnesium (99.99wt.%), pure zinc, Mg-20.0wt.% Er master alloy by the above-mentioned content Zn 4.0wt.%, Er 0.5wt.%, all the other being the mass percent of magnesium, and Remove the oxide skin on the surface;

(2) Put the pure magnesium in (1) into a clean cast iron crucible and put it together in the hearth of a resistance furnace, preheat at 250°C for 15min to remove the moisture in the crucible, pure zinc and Mg-20.0wt.%Er The master alloy is put into another clean cast iron crucible and put into another electric resistance furnace at a constant temperature of 300°C for standby;

(3) Raise the temperature of the resistance furnace with pure magnesium in (2) to 725°C. During the smelting process, a protective gas with a volume ratio of 19:1 (N ₂ :SF ₆ ) is introduced. After the pure magnesium is completely melted, The melt temperature reaches 728°C, adjust the temperature to 735°C, add all the preheated Zn, keep it for 15 minutes, add all the preheated Mg-20.0wt.% Er, keep it for 15 minutes, and then stir for 3 minutes

(4) Adjust the temperature in (3) to 727°C, remove the dross on the surface of the melt, take out the crucible and pour the melt into a pre-prepared metal mold, and cool naturally after solidification to obtain an ingot.

Example 3:

A magnesium-air battery negative electrode material, the mass composition percentage of the negative electrode material: Zn 6.0wt.%, Er0.75wt.%, the rest is magnesium.

(1) take by weighing commercially pure magnesium (99.99wt.%), pure zinc, Mg-20.0wt.% Er master alloy by the above-mentioned content Zn 6.0wt.%, Er 0.75wt.%, all the other being the mass percent of magnesium, and Remove the oxide skin on the surface;

(2) Put the pure magnesium in (1) into a clean cast iron crucible and put it together in the hearth of a resistance furnace, preheat at 250°C for 15min to remove the moisture in the crucible, pure zinc and Mg-20.0wt.%Er The master alloy is put into another clean cast iron crucible and put into another electric resistance furnace at a constant temperature of 300°C for standby;

(3) Raise the temperature of the electric resistance furnace with pure magnesium in (2) to 715°C. During the smelting process, a protective gas with a volume ratio of 19:1 (N ₂ :SF ₆ ) is introduced, until the pure magnesium is completely melted. The melt temperature reaches 722°C, adjust the temperature to 730°C, add all the preheated Zn, keep it for 15 minutes, add all the preheated Mg-20.0wt.% Er, keep it for 15 minutes, and then stir for 3 minutes

(4) Adjust the temperature in (3) to 720°C, remove the dross on the surface of the melt, take out the crucible and pour the melt into a pre-prepared metal mold, and cool naturally after solidification to obtain an ingot.

Example 4:

A magnesium-air battery negative electrode material, the mass composition percentage of the negative electrode material: Zn 8.0wt.%, Er 1.0wt.%, the rest is magnesium.

(1) take by weighing commercially pure magnesium (99.99wt.%), pure zinc, Mg-20.0wt.% Er intermediate alloy by the mass percent of above-mentioned content Zn 8.0wt.%, Er 1.0wt.%, all the other being magnesium, and Remove the oxide skin on the surface;

(2) Put the pure magnesium in (1) into a clean cast iron crucible and put it together in the hearth of a resistance furnace, preheat at 250°C for 15min to remove the moisture in the crucible, pure zinc and Mg-20.0wt.%Er The master alloy is put into another clean cast iron crucible and put into another electric resistance furnace at a constant temperature of 300°C for standby;

(3) Raise the temperature of the electric resistance furnace with pure magnesium in (2) to 720°C. During the smelting process, a protective gas with a volume ratio of 19:1 (N ₂ :SF ₆ ) is introduced, until the pure magnesium is completely melted. The melt temperature reaches 728°C, adjust the temperature to 735°C, add all the preheated Zn, keep it for 15 minutes, add all the preheated Mg-20.0wt.% Er, keep it for 15 minutes, and then stir for 2 minutes

(4) Adjust the temperature in (3) to 730°C, remove the scum on the surface of the melt, take out the crucible and pour the melt into a pre-prepared metal mold, and cool naturally after solidification to obtain an ingot.

Adopt LAND electrical performance monitoring equipment (CT2001A) to measure the discharge performance of the magnesium-air battery negative electrode material described in Examples 1 to 4, the battery experiment is tested in a metal-air battery reactor, and the positive electrode catalyst used is commercial MnO ₂ /C Catalyst, electrolyte solution is 3.5wt.% NaCl aqueous solution, test temperature is room temperature. Discharge for 2h at different current densities (1mA cm ^-2 , 10mA cm ^-2 , 20mA cm ^-2 and 50mA cm ^-2 ), and take the average value of the measured voltage as the discharge voltage, utilization efficiency, and discharge capacity.

The discharge performance parameters provided by all the embodiments of table 1

It can be seen from Figure 1 that in Example 1, the second phase mainly exists in the form of particles between grain boundaries and dendrites. As the content of added elements increases, the second phase becomes continuous at the grain boundaries, and Example 4 produces coarse irregularities. Stripe second phase. It can be seen from Fig. 2 that in Example 1, the granular second phases at grain boundaries and between dendrites are all quasicrystalline I phases, and that produced in Example 2 is mainly short strip I phases, and in Examples 3 and 4, the grain boundaries on the surface are produced. Irregular strip I phase. The content of phase I generated in Mg-Zn-Er alloys increases with the increase of the content of added elements.

As can be seen from Figure 3, in combination with Table 1, comparing the discharge performance of Examples 1 to 4, it can be seen that the different magnesium alloy negative electrodes all have higher discharge voltages, and the granular I phase is dispersed among the dendrites of Example 1, as The cathode accelerates the discharge of the magnesium matrix. In Example 2, the granular I phase decreases, and the phases begin to gather at the grain boundaries, and intermittent strip-like I phases appear on the grain boundaries; with the increase of the element content, the phase volume fraction further increases. Irregular strip-shaped I phases are distributed at the intersecting grain boundaries of Examples 3 and 4, and the content of I phases in Example 4 is more, and some I phases are connected to each other. Combining the discharge curves and discharge parameters of Examples 1 to 4 at different current densities, Example 1 only contains the granular I phase and the content is small, and the number of corrosion microcouples formed on the solid-liquid interface is small, which effectively inhibits the The hydrogen evolution self-corrosion of the magnesium alloy negative electrode in the aqueous electrolyte reduces the amount of magnesium lost due to self-corrosion, and improves the utilization efficiency and discharge capacity; in Example 4, the I phase at the grain boundary is larger in size and closely connected, which is beneficial to hinder The further expansion of the corrosion suppresses the hydrogen evolution self-corrosion, so it has an optimized discharge effect. Therefore, the alloy composition provided by the invention is a negative electrode material for magnesium-air battery with excellent performance.

Although the preferred implementation cases have been listed and described in detail here, those skilled in the art will know that various improvements, additions, substitutions, etc. can be made without departing from the spirit of the present invention, and these contents are all considered to be defined in the claims. within the scope of the present invention.

Claims (7)

1. Mg-Zn-Er alloy, a negative electrode material for magnesium-air battery, is characterized in that, the mass composition percentage of Mg-Zn-Er alloy: Zn 0.6～20.0wt.%, Er 0.1～3.5wt.%, the rest is magnesium And unavoidable impurities; the mass ratio of alloying elements Zn to Er is Zn/Er≥6. 2. A Mg-Zn-Er alloy as a negative electrode material for a magnesium-air battery according to claim 1, wherein 10≥Zn/Er≥6. 3. A Mg-Zn-Er alloy as a negative electrode material for a magnesium-air battery according to claim 1, wherein the quasi-crystal I phase Mg ₃ Zn ₆ Er ₁ is precipitated in the alloy. 4. prepare the method for the Mg-Zn-Er alloy described in any one of claim 1-3, it is characterized in that, comprise the following steps: (1) According to the above content Zn 2.0～8.0wt.%, Er 0.1～3.5wt.%, the rest is magnesium, Zn/Er mass ratio Zn/Er≥6, weigh commercially pure magnesium, pure zinc, Mg-Er Master alloy, and remove the oxide skin on the surface; (2) Put the pure magnesium in (1) into a clean cast iron crucible and put them together in the hearth of a resistance furnace, preheat at 150-300°C for 10-20 minutes to remove the moisture in the crucible, pure zinc and Mg-Er Put the master alloy into another clean cast iron crucible and put it into another electric resistance furnace at a constant temperature of 250-350°C for standby; (3) Heat up the resistance furnace with pure magnesium in (2) to 700-730°C, and pass a protective gas with a volume ratio of 19:1 (N ₂ :SF ₆ ) during the smelting process until the pure magnesium is completely melted After the melt temperature reaches 720-730°C, adjust the temperature to 730-750°C, add all the preheated Zn, keep it for 10-15 minutes, add all the preheated Mg-Er, continue to keep it for 10 minutes ~15min, then stir for 1~3min; (4) Adjust the temperature in (3) to 710-730°C, remove the dross on the surface of the melt, take out the crucible and cast the melt into a pre-prepared metal mold, and cool it naturally after solidification to obtain the cast iron. ingot. 5. The method according to claim 4, characterized in that, the purity of commercially pure magnesium is above 99.9%; the composition of the Mg-Er master alloy is Mg-20wt.%Er. 6. The method according to claim 4, characterized in that the casting in step (4) is carried out under a protective atmosphere, and the protective atmosphere is the same as the smelting process. 7. The application of the Mg-Zn-Er alloy described in any one of claims 1-3, directly acting in the aqueous electrolyte as the negative electrode material of the magnesium-air battery.

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