Alkaline electrolyte for aluminum-air battery and preparation method and application thereof

Abstract

This invention discloses an alkaline electrolyte for aluminum-air batteries, its preparation method, and its application. The electrolyte is composed of a strong alkaline solution, an organic solvent, and inorganic additives. The organic solvent consists of ethers and amides in a volume ratio of (35–90)%:(65–10)%, and the inorganic additives consist of metal salts and metal oxides in a molar ratio of (1–3):(1–2). The volume ratio of the organic solvent to the strong alkaline solution is (5–45):(95–55), and the concentration of the inorganic additives in the alkaline electrolyte for aluminum-air batteries is 0.005–0.3 mol / L. This invention, through the synergistic effect of solvation and interface regulation by the organic solvent and the strengthening effect of the inorganic additives on the interface film, inhibits the activity of free water, effectively suppresses hydrogen evolution corrosion of aluminum, reduces electrode polarization, improves the stability of the electrolyte, and significantly improves the electrochemical performance of aluminum-air batteries.

Description

Technical Field

[0001] This invention belongs to the field of new energy battery technology, specifically relating to an alkaline electrolyte for aluminum-air batteries, its preparation method, and its application. Background Technology

[0002] With continuous economic development, environmental and energy problems are becoming increasingly serious, making the search for a new, clean, and renewable energy source a current research hotspot. Metal-air batteries, due to their environmental friendliness and safety, have broad application prospects. Among them, aluminum-air batteries demonstrate significant advantages and potential due to abundant aluminum resources, high energy density, low price, and good recyclability.

[0003] However, aluminum-air batteries have not yet achieved large-scale commercial application. The main reason is the severe hydrogen evolution corrosion problem of aluminum in aluminum-air batteries. Because aluminum is an amphoteric metal, its chemical properties are highly reactive, and the OH groups in the alkaline electrolyte... - The presence of H2O makes aluminum prone to hydrogen evolution and self-corrosion, resulting in low anode utilization and decreased electrochemical performance of the battery.

[0004] Adding inorganic, organic, or composite additives to the electrolyte of aluminum-air batteries can adsorb and deposit a protective film at the aluminum / electrolyte interface, hindering the contact between water molecules and the corrosive medium with the aluminum and inhibiting hydrogen evolution corrosion. However, this method has limited efficiency. Patent CN202010181154.0 discloses a high-concentration alkaline electrolyte for aluminum-air batteries. By adding a high concentration of potassium salt, the solvation structure of water molecules can be changed, reducing free water and its activity. However, this method requires a large amount of salt, resulting in high electrolyte viscosity and low conductivity. Furthermore, the aluminum surface is affected by water and the corrosive medium OH-. - Hydrogen evolution corrosion still exists even with contact with the anode. Therefore, it is of great significance to find a new electrolyte that can effectively improve the hydrogen evolution corrosion problem of aluminum anodes. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide an alkaline electrolyte for aluminum-air batteries, its preparation method, and its application. The aim is to improve the hydrogen evolution corrosion problem of aluminum anodes, increase the utilization rate of aluminum anodes, and enhance the electrochemical performance of batteries by controlling the solvation structure and interface structure of the electrolyte.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The alkaline electrolyte for aluminum-air batteries provided by this invention is composed of a strong alkaline solution, an organic solvent, and an inorganic additive. The organic solvent is composed of ether solvent and amide solvent in a volume ratio of (35-90)%:(65-10)%. The volume ratio of the organic solvent to the strong alkaline solution is (5-45):(95-55). The inorganic additive is composed of metal salt and metal oxide in a molar ratio of (1-3):(1-2), and the concentration of the inorganic additive in the alkaline electrolyte for aluminum-air batteries is 0.005-0.3 mol / L.

[0008] Preferably, the organic solvents include at least one of the following: ether solvents, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol methyl ethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polytetraethylene glycol dimethyl ether; and amide solvents, at least one of the following: N-methylacetamide, N-methylformamide, N,N-dimethylacetamide, N,N-dimethylhydroxyacetamide, N-methoxy-N-methylacetamide, and N-methoxy-N-methylformamide.

[0009] Preferably, the inorganic additive contains at least one metal salt selected from zinc, tin, indium, bismuth, gallium, and chromium; and at least one metal oxide selected from zinc, tin, indium, bismuth, gallium, and chromium.

[0010] Preferably, the metal salt is at least one selected from sulfate, sulfonate, oxalate, chloride, acetate, and nitrate.

[0011] Further preferably, in the inorganic additive, the metal salt is any one of sodium stannate, zinc sulfate, indium sulfate, and bismuth nitrate, and the metal oxide is any one of tin dioxide, zinc oxide, and indium oxide.

[0012] In this invention, excessively high organic solvent content can easily cause electrode polarization, while excessively low content has limited effect on regulating the electrolyte solvation structure and the aluminum / electrolyte side interface structure. Insufficient inorganic additives result in limited hydrogen evolution inhibition, while excessively high amounts lead to an overly thick product film on the aluminum surface, making it prone to detachment. Therefore, the concentrations of both organic solvents and inorganic additives should be controlled within the selected ranges.

[0013] Preferably, the strong alkali is at least one selected from sodium hydroxide, potassium hydroxide, barium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide.

[0014] Preferably, the concentration of the strong alkali solution is 2–8 mol / L.

[0015] The method for preparing the alkaline electrolyte for aluminum-air batteries includes the following steps:

[0016] 1) Prepare a strong alkaline solution;

[0017] 2) Mix the organic solvent with the strong alkali solution from step 1) according to the set volume ratio, and stir until homogeneous to obtain a mixed solution;

[0018] 3) Add the prescribed amount of inorganic additive to the mixed solution in step 2), stir until dissolved, and the alkaline electrolyte for aluminum-air batteries is obtained.

[0019] Preferably, in steps 2) to 3), the stirring temperature is 20 to 60°C; the stirring method is at least one of magnetic stirring, ultrasonic stirring, and mechanical stirring; and the stirring time is 30 to 90 minutes.

[0020] In the preparation method of this invention, the stirring time and temperature of each step are particularly critical. During solution preparation, increasing the temperature is beneficial for thorough mixing of the components, but excessively high temperatures can easily cause the evaporation of organic solvents or water. To ensure that the components are fully dissolved and mixed, the stirring time should be as long as possible.

[0021] The application of the alkaline electrolyte for aluminum-air batteries in aluminum-air batteries.

[0022] This invention proposes an alkaline electrolyte for aluminum-air batteries, which can effectively improve hydrogen evolution corrosion of aluminum and enhance the electrochemical performance of the battery. Its mechanism of action is as follows:

[0023] (1) This invention introduces ether / amide organic solvents into the alkaline electrolyte. On the one hand, the organic solvent preferentially forms hydrogen bonds with water molecules inside and outside the solvation sheath through the lone pair electrons on the -COC or -C=O functional groups, making the interaction between the organic solvent and water stronger than that between cations and water, reducing the content of free water, and weakening the solvation effect of cations and coordinated water. At the same time, the organic solvent can bind the hydrogen in H2O through the hydrogen bond network formed between itself and H2O molecules, improving the thermodynamic stability of water and thus reducing water activity. On the other hand, these organic solvents contain highly electronegative polar functional groups such as ether bonds or carbonyl groups, which can preferentially adsorb onto the aluminum surface before water molecules, thus constructing a new water-poor double layer at the aluminum / electrolyte interface, reducing the adsorption of water molecules at the aluminum anode interface, occupying the active sites for hydrogen evolution corrosion, and hindering the action of water molecules and the corrosive medium OH. -Contact with aluminum. Therefore, organic solvents can synergistically regulate the solvation structure of the electrolyte and the aluminum / electrolyte interface structure, thus inhibiting the hydrogen evolution corrosion of aluminum. (2) Inorganic additives such as tin salts, zinc salts, indium salts and their oxides with high hydrogen evolution overpotential can preferentially reduce to form an inorganic film on the aluminum layer surface during the aluminum anode discharge process, increasing the coverage area of ​​the protective film, making up for the limited adsorption capacity of organic solvents at the interface, and at the same time increasing the hydrogen evolution overpotential of aluminum, further inhibiting hydrogen evolution corrosion and enhancing its corrosion resistance. (3) Organic solvents and inorganic additives have a synergistic effect. The highly electronegative polar functional groups in organic solvents can be adsorbed on the aluminum surface and also on the surface of inorganic product films. They can also regulate the deposition of inorganic films in the solution system, improve the problem of loose and porous and easy to fall off the single inorganic product film on the aluminum surface, so that the inorganic products are deposited more uniformly and firmly on the aluminum anode surface, enhancing the uniformity, density and stability of the interface film, and further inhibiting the hydrogen evolution self-corrosion of aluminum.

[0024] The beneficial effects of this invention are:

[0025] (1) The organic solvents selected in this invention contain a large number of hydrophilic groups in their molecular structure, which can dissolve in water in any proportion and maintain low viscosity and high ionic conductivity even at high content.

[0026] (2) The organic solvent selected in this invention binds the hydrogen in H2O through hydrogen bonding, which enhances the OH strength in water molecules, improves the thermodynamic stability of water, inhibits the activity of free water, broadens the electrochemical stability window of the electrolyte, and improves the stability of the electrolyte.

[0027] (3) The electrolyte in this invention inhibits the activity of free water through the synergistic effect of solvation of organic solvent and interface regulation and the strengthening effect of inorganic additives on the interface film, effectively inhibits the hydrogen evolution corrosion of aluminum, reduces the polarization of the electrode, and has a corrosion inhibition efficiency of up to 95%. The working voltage is increased by 100-300mV and the discharge specific capacity is increased by 800-1500mAh / g.

[0028] (4) The alkaline electrolyte preparation method provided by the present invention is simple to operate, low in cost, and has a wide range of raw material sources, and has good application prospects. Detailed Implementation

[0029] The following embodiments are intended to further illustrate the content of the present invention; however, the scope of protection of the claims of the present invention is not limited by the embodiments.

[0030] In the following examples and comparative examples, the aluminum negative electrode is pure aluminum, and the positive electrode is a commercial manganese dioxide catalytic electrode.

[0031] Example 1

[0032] First, prepare 70 mL of a 4 mol / L sodium hydroxide solution. Add 30 mL of an organic solvent consisting of tetraethylene glycol dimethyl ether and N,N-dimethylacetamide in a 50%:50% volume ratio. Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of sodium stannate and zinc oxide in a 2:1 molar ratio to the above solution, making the concentration of the inorganic additive in the electrolyte 0.03 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0033] Example 2

[0034] Compared to Example 1, all other conditions remained the same, except that the volume of the sodium hydroxide solution was 55 mL and the volume of the organic solvent was 45 mL.

[0035] Example 3

[0036] Compared to Example 1, all other conditions remained the same, except that the volume of the sodium hydroxide solution was 80 mL and the volume of the organic solvent was 20 mL.

[0037] Example 4

[0038] Compared to Example 1, all other conditions remained the same, except that the volume of the sodium hydroxide solution was 95 mL and the volume of the organic solvent was 5 mL.

[0039] Example 5

[0040] Compared to Example 1, all other conditions remained the same, except that the concentration of the inorganic additive in the electrolyte was 0.005 mol / L.

[0041] Example 6

[0042] Compared to Example 1, all other conditions remained the same, except that the concentration of the inorganic additive in the electrolyte was 0.3 mol / L.

[0043] Example 7

[0044] Compared to Example 1, all other conditions remained the same, except that the volume ratio of ethers to amides in the organic solvent was 35%:65%.

[0045] Example 8

[0046] Compared to Example 1, all other conditions remained the same, except that the volume ratio of ethers to amides in the organic solvent was 90%:10%.

[0047] Example 9

[0048] Compared to Example 1, all other conditions remained the same, except that the molar ratio of metal salt to metal oxide in the inorganic additive was 1:2.

[0049] Example 10

[0050] Compared to Example 1, all other conditions remained the same, except that the molar ratio of metal salt to metal oxide in the inorganic additive was 3:1.

[0051] Example 11

[0052] Compared to Example 1, all other conditions remained the same, except that the concentration of the strong base in the strong base solution was 2 mol / L.

[0053] Example 12

[0054] Compared to Example 1, all other conditions remained the same, except that the concentration of the strong base in the strong base solution was 8 mol / L.

[0055] Example 13

[0056] First, prepare 60 mL of a 5 mol / L sodium hydroxide solution. Add 40 mL of an organic solvent consisting of triethylene glycol dimethyl ether and N-methylformamide in a volume ratio of 40%:60%. Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of sodium stannate and zinc oxide in a molar ratio of 2:1 to the above solution, so that the concentration of the inorganic additive in the electrolyte is 0.1 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0057] Example 14

[0058] First, prepare 70 mL of a 6 mol / L sodium hydroxide solution. Add 30 mL of an organic solvent consisting of 80% ether and 20% N,N-dimethylacetamide (by volume). Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of zinc sulfate and indium oxide in a molar ratio of 1:2 to the above solution, making the concentration of the inorganic additive in the electrolyte 0.08 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0059] Example 15

[0060] First, prepare 70 mL of a 4 mol / L sodium hydroxide solution. Add 30 mL of an organic solvent consisting of diethylene glycol dimethyl ether and N,N-dimethylacetamide in a 50%:50% volume ratio. Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of indium sulfate and tin dioxide in a 1:1 molar ratio to the above solution, making the concentration of the inorganic additive in the electrolyte 0.15 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0061] Example 16

[0062] First, prepare 80 mL of a 4 mol / L sodium hydroxide solution. Add 20 mL of an organic solvent consisting of ethylene glycol monomethyl ether and N,N-dimethylhydroxyacetamide in a 70%:30% (v / v) ratio. Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of bismuth nitrate and zinc oxide in a 2:1 molar ratio to the above solution, making the concentration of the inorganic additive in the electrolyte 0.2 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0063] Example 17

[0064] First, prepare 60 mL of a 4 mol / L sodium hydroxide solution. Add 40 mL of an organic solvent consisting of polytetraethylene glycol dimethyl ether and N-methoxy-N-methylacetamide in a volume ratio of 70%:30%. Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of zinc sulfate and indium oxide in a molar ratio of 2:1 to the above solution, so that the concentration of the inorganic additive in the electrolyte is 0.2 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0065] Example 18

[0066] First, prepare 70 mL of a 4 mol / L sodium hydroxide solution. Add 30 mL of an organic solvent consisting of polytetraethylene glycol dimethyl ether and N-methoxy-N-methylformamide in a volume ratio of 40%:60%. Stir magnetically at 40°C for 50 min until fully mixed to obtain a mixed solution. Add an inorganic additive consisting of indium sulfate and zinc oxide in a molar ratio of 3:2 to the above solution, so that the concentration of the inorganic additive in the electrolyte is 0.1 mol / L. Stir magnetically at 40°C for 40 min until fully dissolved to obtain an alkaline electrolyte for aluminum-air batteries, which is then applied to aluminum-air batteries.

[0067] Comparative Example 1

[0068] The preparation method is similar to that in Example 1, except that no organic solvents and inorganic additives are added.

[0069] Comparative Example 2

[0070] The preparation method is similar to that in Example 1, except that no inorganic additives are added.

[0071] Comparative Example 3

[0072] The preparation method is similar to that in Example 1, except that no organic solvent is added.

[0073] Performance tests are shown in Table 1. Table 1 shows the hydrogen evolution corrosion rate and battery performance at 25 mA cm⁻¹ in the embodiments and comparative examples of the present invention. -2 Electrochemical performance under discharge at a current density for 6 hours.

[0074] Table 1. Hydrogen evolution corrosion rate and electrochemical performance of batteries in the embodiments and comparative examples of the present invention.

[0075]

[0076]

[0077] As shown in Table 1, when the alkaline electrolyte of this invention is used as an electrolyte in aluminum-air batteries, the hydrogen evolution corrosion rate decreases significantly and the discharge specific capacity is significantly improved.

[0078] Analysis of the examples and comparative examples 1-3 shows that the hydrogen evolution corrosion was effectively suppressed in the examples due to the introduction of organic solvents and inorganic additives. In particular, the hydrogen evolution rate of example 1 was only 0.0312 mL / cm. 2 At min, the operating voltage was 1.437V, and the discharge specific capacity was 2384.45mAh / g. However, in Comparative Examples 1 to 3, due to the addition of less or no organic solvents and inorganic additives, hydrogen evolution corrosion was not effectively suppressed, the hydrogen evolution corrosion rate was fast, the operating voltage was reduced, and the discharge specific capacity decreased.

[0079] The embodiments described above merely illustrate several implementations of the present invention and should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An alkaline electrolyte for an aluminum-air battery, comprising a strong alkaline solution, an organic solvent, and an inorganic additive; wherein the organic solvent is composed of an ether solvent and an amide solvent in a volume ratio of (50~90)%:(50~10)%; the volume ratio of the organic solvent to the strong alkaline solution is (30~45):(70~55); the inorganic additive is composed of a metal salt and a metal oxide in a molar ratio of (1~2):(1~2), and the concentration of the inorganic additive in the alkaline electrolyte for the aluminum-air battery is 0.005~0.3 mol / L; The inorganic additives contain metal salts that are at least one of zinc, tin, indium, bismuth, gallium, and chromium; and metal oxides that are at least one of zinc, tin, indium, bismuth, gallium, and chromium oxides. The metal salt is at least one of sulfate, sulfonate, oxalate, chloride, acetate, and nitrate.

2. The alkaline electrolyte for aluminum-air batteries according to claim 1, characterized in that, Among the organic solvents, the ether solvents are at least one selected from diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol methyl ethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and polytetraethylene glycol dimethyl ether; the amide solvents are at least one selected from N-methylacetamide, N-methylformamide, N,N-dimethylacetamide, N,N-dimethylhydroxyacetamide, N-methoxy-N-methylacetamide, and N-methoxy-N-methylformamide.

3. The alkaline electrolyte for aluminum-air batteries according to claim 1, characterized in that, In the inorganic additive, the metal salt is any one of sodium stannate, zinc sulfate, indium sulfate, and bismuth nitrate, and the metal oxide is any one of tin dioxide, zinc oxide, and indium oxide.

4. The alkaline electrolyte for aluminum-air batteries according to claim 1, characterized in that, The strong base is at least one of sodium hydroxide, potassium hydroxide, barium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide.

5. The alkaline electrolyte for aluminum-air batteries according to claim 4, characterized in that, The concentration of the strong alkali solution is 2~8 mol / L.

6. A method for preparing an alkaline electrolyte for an aluminum-air battery as described in claim 1, comprising the following steps: 1) Prepare a strong alkali solution of the concentration described in claim 5; 2) Mix the organic solvent with the strong alkali solution from step 1) according to the set volume ratio, and stir until homogeneous to obtain a mixed solution; 3) Add the prescribed amount of inorganic additive to the mixed solution in step 2), stir until dissolved, and the alkaline electrolyte for aluminum-air batteries is obtained.

7. The preparation method according to claim 6, characterized in that, In steps 2) to 3), the stirring temperature is 20 to 60°C; the stirring method is at least one of magnetic stirring, ultrasonic stirring, and mechanical stirring; and the stirring time is 30 to 90 minutes.

8. The application of the alkaline electrolyte for aluminum-air batteries as described in any one of claims 1 to 5 in aluminum-air batteries.

Images