Electrolyte with corrosion inhibitor added for magnesium-air battery and application thereof

Abstract

The application relates to a magnesium-air battery electrolyte with an added corrosion inhibitor and application, and relates to the technical field of magnesium-air batteries. The electrolyte is composed of sodium chloride and sucrose. In the corrosion inhibitor, the sucrose concentration is 0.02-0.10 mol / L, the mass fraction of the sodium chloride solution is 3.0-4.0 wt%, and the rest is water. The application is aimed at the problems of serious hydrogen evolution corrosion of a magnesium alloy anode in an existing sodium chloride electrolyte system, low anode utilization rate, low discharge voltage and the like. The application proposes that sucrose is added to the electrolyte as a corrosion inhibitor to improve the discharge voltage, anode utilization rate and discharge capacity of a magnesium-air battery with an AZ31 magnesium alloy anode under a certain current density, and the AZ31 magnesium alloy anode is uniformly corroded during the discharge process. The sucrose+NaCl electrolyte system for the magnesium-air battery is small in pollution, non-toxic, green and environment-friendly, can significantly improve the discharge performance of the magnesium-air battery, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of magnesium-air battery technology, specifically to an electrolyte for magnesium-air batteries with added corrosion inhibitors and its application. Background Technology

[0002] With the increasing scarcity of global energy resources and the growing emphasis on environmental protection, seeking and developing environmentally friendly green energy has become a primary choice for many countries, leading to the emergence of metal-air battery technology. This technology uses metals with relatively negative electrode potentials, such as magnesium, zinc, aluminum, and lithium, as the anode and oxygen as the cathode in a chemical battery. It boasts advantages such as large capacity, high energy density, stable discharge, and low cost, attracting significant interest from researchers. As an anode material, magnesium exhibits a relatively negative standard electrode potential (-2.37V vs SHE) and a high capacity (3833mAh·cm⁻¹). -3 In addition, magnesium metal has advantages such as low cost and good chemical stability, making magnesium-air batteries a focus of attention.

[0003] Although magnesium-air batteries have high energy density, their application still has some drawbacks due to the immaturity of existing technologies. The main problems are threefold: (1) Corrosion and self-corrosion: During open circuit and discharge, water reduction consumes electrons released by the magnesium anode, leading to rapid hydrogen evolution on the alloy surface, with the hydrogen evolution rate increasing with positive potential shift; (2) Bulk effect: During discharge, the anode undergoes uneven dissolution, and undissolved anode blocks separate and detach from the magnesium matrix, resulting in a loss of anode utilization; (3) Shielding effect of discharge or corrosion products: Magnesium hydroxide (Mg(OH)2) generated during discharge adheres to the anode surface, hindering further reactions on the anode surface and reducing battery voltage. Direct contact between the electrolyte and the magnesium anode affects the structure and composition of the surface film, thereby affecting the dissolution reaction, hydrogen evolution reaction rate, and discharge voltage.

[0004] In view of this, we propose the present invention. Summary of the Invention

[0005] To address the shortcomings and drawbacks of existing magnesium-air battery technology, the primary objective of this invention is to provide an electrolyte with added corrosion inhibitors for magnesium-air batteries. This electrolyte system, as the electrolyte for magnesium-air batteries, effectively promotes uniform corrosion of the alloy, increases the battery's discharge voltage, enhances anode utilization efficiency and discharge capacity, and exhibits excellent discharge performance.

[0006] The present invention provides an electrolyte for magnesium-air batteries with added corrosion inhibitor, which is composed of sucrose, sodium chloride and water, wherein the concentration of sucrose is 0.02-0.10 mol / L, the mass fraction of sodium chloride is 3.0-4.0 wt%, and the balance is water.

[0007] Furthermore, the concentration of sucrose is 0.10 mol / L.

[0008] Furthermore, the sodium chloride solution has a mass fraction of 3.5 wt%.

[0009] The present invention also provides a method for preparing the above-mentioned electrolyte for magnesium-air batteries with added corrosion inhibitors. First, an aqueous solution of sodium chloride is prepared and stirred until completely dissolved. Then, sucrose is weighed and added to the aqueous solution of sodium chloride, and stirred until completely dissolved to obtain the electrolyte for magnesium-air batteries with added corrosion inhibitors.

[0010] Furthermore, the sodium chloride solution has a mass fraction of 3.5 wt%.

[0011] Another object of the present invention is to provide an application of the above-mentioned electrolyte with added corrosion inhibitor for magnesium-air batteries.

[0012] It further includes an anode material, an air cathode, and the electrolyte described above. The anode material is AZ31.

[0013] This invention is particularly suitable for high current densities, such as 20 mA cm⁻¹. -2 -50mA cm -2 .

[0014] This invention utilizes sucrose to reduce the rate of hydrogen evolution self-corrosion in magnesium-air battery anode materials and improve the activity of magnesium alloy anodes. Sucrose molecules possess numerous hydroxyl groups with lone pairs of electrons, which can form hydrogen bonds with water molecules, binding them. The enhanced water molecule bonds and the increased number of hydrogen bonds both contribute to reducing the reactivity of water and inhibiting the occurrence of self-corrosion reactions.

[0015] The electrolyte for magnesium-air batteries of this invention, with the addition of corrosion inhibitors, has a simple composition and possesses advantages such as being non-toxic, non-polluting, low-cost, and safe. Especially under high current density conditions, it can not only effectively suppress the hydrogen evolution self-corrosion rate of the magnesium alloy anode but also improve the discharge voltage of the magnesium-air battery. During discharge, the magnesium alloy anode exhibits excellent discharge performance, meeting the discharge requirements of magnesium-air batteries and showing very promising development prospects. Attached Figure Description

[0016] Figure 1 The polarization curves of AZ31 magnesium alloy anodes in 3.5 wt% sodium chloride solutions containing different concentrations of corrosion inhibitors are shown.

[0017] Figure 2 The impedance curves of AZ31 magnesium alloy anodes in 3.5 wt% sodium chloride solutions containing different concentrations of corrosion inhibitors are shown.

[0018] Figure 3The graph shows the constant current discharge curves of a magnesium-air battery assembled with an AZ31 anode at different discharge current densities.

[0019] Figure 4 Magnesium-air batteries assembled with AZ31 anodes at different discharge current densities (1, 10, 20, 50 mA cm⁻¹) -2 SEM images after 2 hours of discharge and removal of discharge products. Where a and b are the AZ31 anode in 3.5 wt% NaCl and 3.5 wt% NaCl solutions containing 0.10 mol / L sucrose, respectively, at 1 mA cm⁻¹. -2 SEM images of the removal of discharge products after 2 hours of discharge; c and d are the AZ31 anode in 3.5wt% NaCl and 3.5wt% NaCl solutions containing 0.10mol / L sucrose, respectively, at 10mA cm⁻¹. -2 SEM images of the removal of discharge products after 2 hours of discharge; e and f are the results of AZ31 anode in 3.5wt% NaCl and 3.5wt% NaCl solutions containing 0.10mol / L sucrose at 20mA cm⁻¹. -2 SEM images of the removal of discharge products after 2 hours of discharge; g and h represent the values ​​of AZ31 anode in 3.5 wt% NaCl and 3.5 wt% NaCl solutions containing 0.10 mol / L sucrose, respectively, at 50 mA cm⁻¹. -2 SEM image of the products removed after 2 hours of discharge. Specific implementation methods

[0020] The present invention will be further illustrated below with reference to specific embodiments. It should be noted that the following embodiments are only used to illustrate the specific implementation methods of the present invention and do not limit the scope of protection of the present invention.

[0021] The evaluation and testing of the preparation method of the electrolyte with added corrosion inhibitor for magnesium-air batteries of the present invention was carried out theoretically using an electrochemical workstation (PARSTAT2273), and the surface morphology of the samples was observed using a scanning electron microscope (GeminiSEM 300).

[0022] Electrochemical analysis

[0023] The electrochemical experiment employed a standard three-electrode system. The working electrode was the prepared AZ31 alloy, the saturated calomel electrode (SCE) was the reference electrode, and the platinum sheet was the counter electrode. The preparation process for the magnesium alloy working electrode sample was as follows: First, the magnesium alloy to be tested was cut into small pieces of 10mm × 10mm × 3mm. One 10mm × 10mm surface was polished on 240#, 1200#, and 2000# sandpaper, respectively, and the surface was cleaned with alcohol and air-dried. The treated alloy was then sealed with acrylic powder, but the polished working surface was retained. Electrochemical tests were performed on an Autolab electrochemical workstation (PARSTAT2273). The polarization curve scan rate was 0.5 mV s. -1 The scanning range was ±300 mV relative to the open circuit potential; the frequency of the electrochemical impedance spectroscopy test was 10. -1 -10 5 Hz, with a sinusoidal excitation voltage of ±10mV.

[0024] Example 1:

[0025] In this embodiment, the magnesium-air battery uses an electrolyte with added corrosion inhibitor. The electrolyte is a 3.5 wt% NaCl solution, and the corrosion inhibitor is sucrose with a concentration of 0.02–0.10 mol / L. The electrolyte is prepared as follows: a 3.5 wt% NaCl solution is prepared and stirred until completely dissolved; sucrose is added and stirred until completely dissolved.

[0026] The polarization curves and AC impedance of the AZ31 magnesium alloy anode in the above electrolyte were tested by electrochemical methods. The results are shown in the figure. Figure 1 , Figure 2 As per Table 1, the temperature was controlled at 25℃.

[0027] From Table 1, Figure 1 and Figure 2 It can be seen that adding different concentrations of sucrose causes a negative shift in the corrosion potential. The more negative the corrosion potential and the greater the radius of the impedance arc, the higher the sucrose concentration. Therefore, it can be concluded that the AZ31 magnesium alloy in this embodiment causes a negative corrosion potential and a reduced corrosion rate in the electrolyte.

[0028] Example 2:

[0029] In this embodiment, the magnesium-air battery uses an electrolyte with added corrosion inhibitor, wherein the electrolyte is a 3.5 wt% NaCl solution, and the corrosion inhibitor is sucrose with a concentration of 0.10 mol / L. The preparation method of the electrolyte is as follows: prepare a 3.5 wt% NaCl solution, stir until completely dissolved, add sucrose, and stir until completely dissolved.

[0030] The discharge performance of a magnesium-air battery with AZ31 as the anode in the electrolyte prepared in this embodiment was measured using a LAND electrical performance monitoring system (CT2001A). The positive electrode catalyst used was a commercially available MnO2 / C catalyst, and the test temperature was room temperature. Discharge performance was measured at different current densities (1 mA cm⁻¹). -2 10mA cm -2 20mA cm -2 50mA cm -2 Discharged for 2 hours, results are shown below. Figure 3 The average measured voltage is taken as the discharge voltage.

[0031] from Figure 3 As can be seen, the addition of sucrose increased the discharge voltage of the magnesium-air battery under different discharge current densities, indicating that sucrose can improve the anode activity of the magnesium alloy during discharge.

[0032] After the battery discharge test, use 200g L -1 The chromic acid solution removes the reaction products from the anode surface. The anode utilization efficiency and discharge specific capacity of the magnesium-air battery are calculated using equations (1), (2), and (3):

[0033]

[0034]

[0035]

[0036] Where I(A) and t(h) are the applied discharge current and discharge time, respectively. F is the Faraday constant (26.8Ahmol). -1 ). x i n i and m i (g mol -1 These are the mass fraction, number of exchanged electrons, and atomic mass associated with each alloying element.

[0037] Table 2 shows the operating voltage, anode utilization, and discharge capacity of the magnesium-air battery assembled with AZ31 anodes at different current densities. As can be seen from Table 2, at different discharge currents (1, 10, 20, 50 mA cm⁻¹), the operating voltage, anode utilization, and discharge capacity of the magnesium-air battery assembled with AZ31 anodes at different current densities are... -2 The addition of sucrose increased the discharge voltage of magnesium-air batteries, but at 1cm... -2 Adding sucrose significantly reduced the utilization rate and discharge capacity of the AZ31 magnesium alloy anode, at 10cm. -2 Adding sucrose slightly reduced the utilization rate of the AZ31 magnesium alloy anode, 20cm. -2 Adding sucrose improves the utilization rate of AZ31 magnesium alloy anodes, but the difference between the two is not significant (50cm).-2 With the addition of sucrose, the utilization rate and discharge capacity of the AZ31 magnesium alloy anode significantly increased.

[0038] Figure 4 The results show that a magnesium-air battery assembled with an AZ31 anode operates at different current densities (1, 10, 20, 50 mA cm⁻¹) in different electrolytes. -2 SEM image after removing discharge products 2 hours after discharge. Figure 4 As can be seen from a, at low discharge current density (1 mA cm⁻¹) -2 Under these conditions, AZ31 magnesium alloy exhibited uneven corrosion in a 3.5 wt% NaCl solution. The alloy surface showed corrosion pits of varying sizes, with the pits consisting of small internal pits. A small number of large and deep corrosion pits also remained on the surface. Figure 4 As can be seen from b, after adding sucrose, the alloy surface consists of finely distributed corrosion pits of similar size, indicating that the addition of sucrose promotes uniform corrosion of the alloy during the discharge process. From Figure 4 From c and 4e, it can be seen that at 10 and 20 mAcm -2 Under the following conditions, AZ31 magnesium alloy was uniformly corroded in a 3.5 wt% NaCl solution. After discharge, regular corrosion pits formed on the surface, with smooth interiors. Figure 4 In solutions d and 4f, the addition of sucrose resulted in uniform corrosion of the alloys during discharge, but the shape of the corrosion pits on the alloy surface differed from that in the 3.5wt% NaCl solution, exhibiting elongated, cave-like patterns. Figure 4 g and 4h show that 50mA cm -2 Under these conditions, the smooth corrosion pits on the alloy surface change into fine corrosion pits. Even after adding sucrose, the alloy still exhibits uniform corrosion.

[0039] Although implementation examples have been listed and described in detail herein, those skilled in the art will recognize that various improvements, additions, substitutions, etc., can be made without departing from the spirit of the invention, and all such modifications, additions, substitutions, etc., are considered to be within the scope of the invention as defined by the claims.

[0040] Table 1 shows the polarization curve fitting data of AZ31 magnesium alloy anodes in 3.5 wt% NaCl solutions and 3.5 wt% NaCl solutions containing different concentrations of sucrose.

[0041]

[0042] Table 2 provides discharge performance references for Example 2.

[0043]

Claims

1. A magnesium-air battery, characterized in that, The device includes an anode material, an air cathode, and an electrolyte. The anode material is AZ31, and the electrolyte consists of sucrose, sodium chloride, and water. The concentration of the sucrose is 0.02~0.10 mol / L, the mass fraction of the sodium chloride is 3.5wt%, and the balance is water. The discharge current density is 20 mA cm⁻¹. -2 -50mA cm -2 .

2. A magnesium-air battery according to claim 1, characterized in that, The concentration of sucrose is 0.10 mol / L.

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