Eutectic aqueous aluminum ion battery electrolyte as well as preparation method and application thereof

Abstract

The invention provides eutectic aqueous aluminum ion battery electrolyte as well as a preparation method and application thereof, and relates to the technical field of aluminum ion batteries. According to the invention, the eutectic aqueous aluminum ion battery electrolyte is prepared by solid-solid mixing and dissolving of aluminum metal salt and eutectic substances; the aluminum metal salt is selected from at least one of aluminum chloride hexahydrate, aluminum perchlorate nonahydrate, aluminum nitrate nonahydrate and aluminum sulfate octadecahydrate; the eutectic substance is an organic small molecule compound containing amino and ester groups. By screening hydrated aluminum metal salt and eutecticevaporate substances and regulating and controlling the proportion, the prepared electrolyte is applied to aqueous aluminum ion batteries, such as symmetrical batteries and total batteries, and shows excellent performance. According to the electrolyte, the stability of the aluminum ion battery can be improved, a solvation structure dominated by anions is formed, and meanwhile, a compact anion-rich solid electrolyte interface layer is formed on the surface of an aluminum negative electrode to protect the aluminum negative electrode. The problem that an existing water-based aluminum ion battery negative electrode is poor in stability is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum-ion batteries, and particularly to a deep eutectic aqueous aluminum-ion battery electrolyte and its preparation method and application. Background Art

[0002] In order to address the energy shortage and environmental pollution crises caused by the excessive consumption of traditional fossil fuels, the world urgently needs to shift to renewable energy sources such as solar, wind, biomass, waterfall, and geothermal energy. These clean energy sources have great potential, but due to their limitations in spatio-temporal variations and geographical conditions, power production is intermittent and unstable. Therefore, how to effectively store this unstable electrical energy and provide stable grid dispatching has become an urgent problem to be solved. Among traditional energy storage methods, mechanical energy storage systems such as pumped hydro storage, gravitational energy storage, and compressed air energy storage have been widely used, but they are restricted by geographical conditions and the environment, have high installation and maintenance costs, and occupy a large area, making it difficult to popularize in diverse application scenarios. Therefore, electrochemical energy storage systems, as a new type of energy storage technology, have shown great potential. Compared with traditional mechanical energy storage methods, electrochemical energy storage systems are not restricted by environmental conditions such as terrain and climate, can be flexibly deployed in different regions and scenarios, and have strong adaptability; electrochemical energy storage systems can store more energy in a smaller volume and weight, especially suitable for occasions with high space requirements such as portable electronic devices and wearable devices; electrochemical energy storage systems have a high power output and can instantaneously respond to grid fluctuations or load demands to ensure grid stability; electrochemical energy storage systems can meet different scales of energy demands, from small household energy storage devices to large-scale grid energy storage, and are an important part of future energy infrastructure.

[0003] Although current electrochemical energy storage systems still face problems such as high costs, service life, and cycle efficiency, with continuous technological innovation, especially driven by the research and development of new materials, improvement of manufacturing processes, and industrial large-scale production, future electrochemical energy storage is expected to achieve lower costs, higher performance, and longer service life. This provides broad prospects for a variety of applications from small portable devices to large fixed energy storage systems. By continuously promoting the progress of electrochemical energy storage technology, in the future, we can achieve efficient utilization of energy and further promote the transformation of the global energy structure and the development of a green and low-carbon economy.

[0004] Research has found that aqueous aluminum-ion batteries can fully meet the requirements of large-scale energy storage systems. Due to the abundance and excellent safety of aluminum, aluminum-ion batteries have significant potential. In addition, as a multivalent metal, aluminum can provide a higher volumetric specific capacity than lithium-ion batteries (aluminum: 8046 mAh / cm 3 , lithium: 2045 mAh / cm 3) Therefore, aluminum-ion batteries are expected to be more compact than lithium-ion batteries in terms of volume, and this advantage is particularly significant in applications with limited space. Aluminum has a mass specific capacity of 2980 mAh / g, which is slightly lower than lithium's 3860 mAh / g but still higher than many other metals (such as sodium, potassium, magnesium, and calcium). Due to aluminum's relatively high mass and volume specific capacities, the overall energy density of aluminum-ion battery systems still has the potential to approach or even exceed that of lithium-ion batteries. This characteristic makes aluminum-ion batteries show great potential in applications with high energy density requirements. Compared with traditional lithium-ion batteries, the advantages of aluminum-ion batteries are not only reflected in the abundance and low cost of materials, but also the safety of aluminum is far better than that of lithium-ion batteries. Lithium-ion batteries have safety hazards such as overcharging, short circuit, and thermal runaway, while aluminum batteries have better thermal stability and are not easily prone to fire or explosion, so they can provide higher safety guarantees under high temperature or extreme environmental conditions. In addition to safety and cost advantages, the long-cycle stability and relatively fast charge and discharge rates of aluminum-ion batteries are also their potential advantages. With the progress of battery technology, the cycle life and efficiency of aluminum-ion batteries are expected to be further improved, enabling them to meet the needs of diverse applications from small portable devices to large-scale grid energy storage systems. Generally speaking, aluminum-ion batteries, with their low cost, high safety, relatively high energy density, and excellent comprehensive performance, are expected to become an important supplement to the current energy storage battery system. With continuous technological innovation, aluminum-ion batteries have the potential to become an important part of future energy storage solutions, especially in the fields of large-scale energy storage, electric transportation, and renewable energy storage, where they will play an important role.

[0005] In an aluminum-ion electrolyte with water as the main solvent, the standard electrode potential of aluminum is -1.66 V (relative to the standard hydrogen electrode), and this potential value is relatively low. According to electrochemical principles, when aluminum is in an electrolyte with water as the main solvent, it is more likely to react with water to produce hydrogen gas (H 2 ) and aluminum hydroxide (Al(OH) 3 ) and other products. This makes the electrochemical behavior of aluminum unstable. Especially during the charging process, oxidation reactions are likely to occur on the aluminum negative electrode rather than the deposition of metallic aluminum on its surface. In an ionic liquid electrolyte mainly composed of AlCl 3 / [EMIm]Cl, the carrier ions change from Al 3 + to AlCl 4 - and Al 2 Cl 7 -, the three-electron transfer reaction of aluminum is difficult to achieve, and the actual energy density is relatively low. In addition, the inevitable corrosion phenomenon in the chlorine-based electrolyte seriously shortens the service life of the aluminum metal negative electrode, and the air sensitivity of the ionic liquid further increases the difficulty of electrolyte storage. These factors have hindered the commercial application of aluminum-ion batteries. Therefore, it is necessary to explore a new type of aqueous aluminum-ion electrolyte with low cost, air stability and protection for the aluminum negative electrode. In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The present invention provides a eutectic aqueous aluminum-ion battery electrolyte, its preparation method and application, aiming to solve the problem of poor stability of the negative electrode of existing aqueous aluminum-ion batteries.

[0007] To achieve the above object, an embodiment of the present invention provides a eutectic aqueous aluminum-ion battery electrolyte, its preparation method and application. The eutectic electrolyte of the present invention is prepared by solid-solid mixing of an aluminum metal salt and a eutectic substance. The aluminum metal salt is selected from at least one of aluminum chloride hexahydrate, aluminum perchlorate nonahydrate, aluminum nitrate nonahydrate and aluminum sulfate octadecahydrate; the eutectic substance is selected from ester compounds. The molar ratio of the aluminum metal salt to a single ester compound is 1:1-8, and the molar ratio of the aluminum metal salt to two ester compounds is 1:2:2; through the screening of the hydrated aluminum metal salt and the ester compound and the regulation of the ratio, the prepared preferred electrolyte exhibits excellent performance in both symmetric batteries and full batteries. The present invention also includes the electrolyte prepared by the described preparation method and its application in aqueous aluminum-ion batteries. The electrolyte described in the present invention can improve the stability of aluminum-ion batteries, form a solvation structure dominated by anions, and at the same time form a dense anion-rich solid electrolyte interface layer (SEI) on the surface of the aluminum negative electrode to protect the aluminum metal negative electrode.

[0008] An embodiment of the present invention provides a eutectic aqueous aluminum-ion battery electrolyte, and the aqueous aluminum-ion battery electrolyte includes an aluminum metal salt and a eutectic substance;

[0009] The aluminum metal salt includes at least one of aluminum chloride hexahydrate, aluminum perchlorate nonahydrate, aluminum nitrate nonahydrate and aluminum sulfate octadecahydrate;

[0010] The eutectic substance is an organic small molecule compound containing an amino group and an ester group.

[0011] Preferably, the eutectic substance is selected from methyl carbamate or ethyl carbamate; the molar ratio of the aluminum metal salt to the eutectic substance is 1:1-8.

[0012] Preferably, the eutectic substance is selected from methyl carbamate and ethyl carbamate.

[0013] More preferably, the molar ratio of the aluminum metal salt, methyl carbamate, and ethyl carbamate is 1:2:2.

[0014] Based on the general concept of an invention, an embodiment of the present invention provides the above-mentioned preparation method of a eutectic aqueous aluminum-ion battery electrolyte. The aluminum metal salt is mixed with the eutectic substance to prepare the aqueous aluminum-ion battery electrolyte.

[0015] Preferably, the mixing process is as follows: heating at 30-90°C for 10-40 minutes, naturally cooling to room temperature, and then stirring for 10-30 minutes. More preferably, the heating temperature is 30-50°C; stirring for 10 minutes.

[0016] An embodiment of the present invention also provides an aqueous aluminum-ion secondary battery, including the above-mentioned eutectic aqueous aluminum-ion battery electrolyte or a eutectic aqueous aluminum-ion battery electrolyte prepared by the above-mentioned preparation method.

[0017] Preferably, the aqueous aluminum-ion secondary battery is a symmetric battery composed of an aluminum metal foil, a glass fiber separator, and an aqueous aluminum-ion battery electrolyte.

[0018] Preferably, the aqueous aluminum-ion secondary battery is a full battery composed of an aluminum metal foil as the negative electrode, a positive electrode, a glass fiber separator, and an aqueous aluminum-ion battery electrolyte.

[0019] More preferably, the positive electrode material is selected from at least one of manganese dioxide, Prussian blue, polyaniline, activated carbon, and diquinoxalino[2,3-a:2',3'-c]phenazine.

[0020] The aluminum metal foil is abbreviated as aluminum foil, and there is no special requirement for its thickness, as long as it meets the application requirements of the aluminum foil negative electrode. For example, it is greater than or equal to 35μm, preferably greater than or equal to 50μm, further preferably 50-300μm, and more preferably 50-200μm. The aluminum foil is pre-treated including grinding and / or cleaning.

[0021] Mechanism

[0022] By screening the hydrated aluminum metal salt and the ester compound and optimizing the ratio, the prepared eutectic aqueous aluminum-ion battery electrolyte has the advantages of low cost, air stability, and aluminum negative electrode protection. The electrolyte of the present invention can improve the stability of the aluminum-ion battery, form an anion-dominated solvation structure, and at the same time form a dense anion-rich solid electrolyte interface layer on the surface of the aluminum negative electrode to protect the aluminum metal negative electrode. Solve the problem of poor negative electrode stability of existing aqueous aluminum-ion batteries. The eutectic aqueous aluminum-ion battery electrolyte of the present invention, as the electrolyte of the aqueous aluminum-ion battery, can significantly improve the battery cycle life and stability, and continuously protect the metal negative electrode.

[0023] The above solution of the present invention has the following beneficial effects:

[0024] (1) The present invention uses a hydrated aluminum metal salt and an ester compound to be miscible, and through the screening of the ratio of the hydrated aluminum metal salt and the ester compound, an electrolyte with low cost, air stability and capable of protecting the aluminum metal negative electrode is preferably obtained.

[0025] (2) The present invention uses the obtained hydrated eutectic electrolyte in the aqueous aluminum metal ion battery electrolyte to obtain excellent electrochemical performance. It alleviates the instability of the traditional aqueous electrolyte and the corrosion of the aluminum metal negative electrode.

[0026] (3) The process of the present invention is simple and low in cost, and it is easy to realize large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is the electrolyte of Embodiment 1 of the present invention, with an aluminum foil as the negative electrode, and the cyclic charge and discharge curve diagram of the symmetric cell at a current density of 0.5 mA / cm 2 current density.

[0029] Figure 2 It is the electrolyte of Embodiment 2 of the present invention, with an aluminum foil as the negative electrode, and the cyclic charge and discharge curve diagram of the symmetric cell at a current density of 0.5 mA / cm 2 current density.

[0030] Figure 3 It is the electrolyte of Embodiment 3 of the present invention, with an aluminum foil as the negative electrode, and the cyclic charge and discharge curve diagram of the symmetric cell at a current density of 0.5 mA / cm 2 current density.

[0031] Figure 4 It is the electrolyte of Comparative Example 1 of the present invention, with an aluminum foil as the negative electrode, and the cyclic charge and discharge curve diagram of the symmetric cell at a current density of 0.5 mA / cm 2 current density.

[0032] Figure 5 It is the electrolyte of Comparative Example 2 of the present invention, with an aluminum foil as the negative electrode, and the cyclic charge and discharge curve diagram of the symmetric cell at a current density of 0.5 mA / cm 2 current density.

[0033] Figure 6is the electrolyte of Comparative Example 3 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.5 mA / cm 2

[0034] Figure 7 is the electrolyte of Comparative Example 4 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.5 mA / cm 2

[0035] Figure 8 is the electrolyte of Comparative Example 5 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.5 mA / cm 2

[0036] Figure 9 is the scanning electron microscope images of the electrolyte of Examples 1-3 and Comparative Examples 1-5 of the present invention after the symmetric cell is cycled with the aluminum foil as the negative electrode.

[0037] Figure 10 is the electrolyte of Example 1 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.2 mA / cm 2

[0038] Figure 11 is the electrolyte of Comparative Example 5 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.2 mA / cm 2

[0039] Figure 12 is the electrolyte of Comparative Example 6 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.2 mA / cm 2

[0040] Figure 13 is the electrolyte of Comparative Example 7 of the present invention. The aluminum foil serves as the negative electrode, and it is the cyclic charge-discharge curve graph of the symmetric cell at a current density of 0.2 mA / cm 2

[0041] Figure 14 is the XPS spectra of the electrolyte of Example 1 and Comparative Example 5 of the present invention on the surface of the aluminum foil after the symmetric cell is cycled with the aluminum foil as the negative electrode.

[0042] Figure 15 are the scanning electron microscope images and optical images of the surface of the aluminum foil after the aluminum foil of the electrolyte of Example 1 and Comparative Example 5 of the present invention is soaked at different temperatures.

[0043] Figure 16 ​​​​​​​It is the electrolyte of Example 1 of the present invention. The aluminum foil is the negative electrode, and polyaniline is the positive electrode. It is the cycle performance diagram at a current density of 500 mA / g.

[0044] Figure 17 It is the electrolyte of Comparative Example 6 of the present invention. The aluminum foil is the negative electrode, and polyaniline is the positive electrode. It is the cycle performance diagram at a current density of 500 mA / g.

[0045] Figure 18 It is the electrolyte of Comparative Example 7 of the present invention. The aluminum foil is the negative electrode, and polyaniline is the positive electrode. It is the cycle performance diagram at a current density of 500 mA / g.

[0046] Figure 19 It is the cycle charge and discharge curve diagram of the electrolytes of Example 1 and Comparative Examples 6-7 of the present invention. The aluminum foil is the negative electrode, and diquinoxalino[2,3-a:2',3'-c]phenazine is the positive electrode.

[0047] Figure 20 It is the optical picture of the electrolytes of Example 1 and Comparative Example 8 of the present invention under different aluminum salts. Detailed implementation manners

[0048] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0049] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

[0050] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0051] Aiming at the problem of poor negative electrode stability of existing aqueous aluminum-ion batteries, the embodiments of the present invention provide a eutectic aqueous aluminum-ion battery electrolyte, and the aqueous aluminum-ion battery electrolyte includes an aluminum metal salt and a eutectic substance;

[0052] The aluminum metal salt includes at least one of aluminum chloride hexahydrate, aluminum perchlorate nonahydrate, aluminum nitrate nonahydrate and aluminum sulfate octadecahydrate;

[0053] The eutectic substance is an organic small molecule compound containing an amino group and an ester group.

[0054] Preferably, the eutectic substance is selected from methyl carbamate or ethyl carbamate; the molar ratio of the aluminum metal salt to the eutectic substance is 1:1 to 8.

[0055] Preferably, the eutectic substance is selected from methyl carbamate and ethyl carbamate.

[0056] More preferably, the molar ratio of the aluminum metal salt, methyl carbamate and ethyl carbamate is 1:2:2.

[0057] Based on the general concept of an invention, embodiments of the present invention provide a preparation method of the above-mentioned eutectic aqueous aluminum-ion battery electrolyte. The aluminum metal salt and the eutectic substance are mixed to prepare the aqueous aluminum-ion battery electrolyte.

[0058] Preferably, the mixing process is as follows: heating at 30-90 °C for 10-40 min, naturally cooling to room temperature and then stirring for 10-30 min. More preferably, the heating temperature is 30-50 °C; stirring for 10 min.

[0059] Embodiments of the present invention also provide an aqueous aluminum-ion secondary battery, including the above-mentioned eutectic aqueous aluminum-ion battery electrolyte or a eutectic aqueous aluminum-ion battery electrolyte prepared by the above-mentioned preparation method.

[0060] Preferably, the aqueous aluminum-ion secondary battery is a symmetric battery composed of an aluminum metal foil, a glass fiber separator and an aqueous aluminum-ion battery electrolyte.

[0061] Preferably, the aqueous aluminum-ion secondary battery is a full battery composed of an aluminum metal foil as the negative electrode, a positive electrode, a glass fiber separator and an aqueous aluminum-ion battery electrolyte.

[0062] More preferably, the positive electrode material is selected from at least one of manganese dioxide, Prussian blue, polyaniline, activated carbon and diquinoxalino[2,3-a:2',3'-c]phenazine.

[0063] The aluminum metal foil is simply referred to as aluminum foil, and there is no special requirement for the thickness, as long as it meets the application requirements of the aluminum foil negative electrode. For example, it is greater than or equal to 35 μm, preferably greater than or equal to 50 μm, further preferably 50-300 μm, and more preferably 50-200 μm. The aluminum foil is pre-treated including polishing and / or cleaning.

[0064] The following is illustrated by specific examples

[0065] Example 1

[0066] This example provides a preparation method of a eutectic aqueous aluminum-ion battery electrolyte.

[0067] The method includes the following steps:

[0068] Weigh aluminum perchlorate nonahydrate and methyl carbamate according to a molar ratio of 1:4.

[0069] Mix the substances weighed in step (1) and put them into a 25 mL serum bottle. Add a magnetic stir bar of appropriate size, and then stir at a speed of 500 revolutions per minute at 50 °C for 10 minutes to obtain a clear solution.

[0070] Let the clear solution obtained in step (2) cool to room temperature naturally, and then stir at room temperature for 10 minutes to obtain a clear and transparent electrolyte solution at room temperature.

[0071] Use the prepared electrolyte solution as the electrolyte of an aluminum metal ion battery, with aluminum foil as the negative electrode, and assemble a symmetric battery.

[0072] Use the prepared electrolyte solution as the electrolyte of an aluminum metal ion battery, with aluminum foil as the negative electrode and polyaniline or diquinoxalino[2,3-a:2',3'-c]phenazine as the positive electrode, and assemble a full battery.

[0073] Example 2

[0074] This example provides a preparation method of a deep eutectic aqueous aluminum ion battery electrolyte.

[0075] This method includes the following steps:

[0076] Weigh aluminum perchlorate nonahydrate and ethyl carbamate according to a molar ratio of 1:4.

[0077] Mix the substances weighed in step (1) and put them into a 25 mL serum bottle. Add a magnetic stir bar of appropriate size, and then stir at a speed of 500 revolutions per minute at 50 °C for 10 minutes to obtain a clear solution.

[0078] Let the clear solution obtained in step (2) cool to room temperature naturally, and then stir at room temperature for 10 minutes to obtain a clear and transparent electrolyte solution at room temperature.

[0079] Use the prepared electrolyte solution as the electrolyte of an aluminum metal ion battery, with aluminum foil as the negative electrode, and assemble a symmetric battery.

[0080] Example 3

[0081] This example provides a preparation method of a deep eutectic aqueous aluminum ion battery electrolyte.

[0082] This method includes the following steps:

[0083] Weigh aluminum perchlorate nonahydrate, methyl carbamate and ethyl carbamate according to a molar ratio of 1:2:2.

[0084] Mix the substances weighed in step (1) and put them into a 25 mL serum bottle. Add a magnetic stir bar of appropriate size, and then stir at a speed of 500 revolutions per minute at 50 °C for 10 minutes to obtain a clear solution.

[0085] Let the clarified solution obtained in step (2) cool naturally to room temperature, and then stir for 10 minutes at room temperature to obtain a clarified and transparent electrolyte solution at room temperature.

[0086] Use the prepared electrolyte as the electrolyte for an aluminum metal ion battery, with an aluminum foil as the negative electrode, and assemble a symmetric battery.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing an electrolyte for an aluminum ion battery.

[0089] The method includes the following steps:

[0090] Weigh aluminum perchlorate nonahydrate and methyl acrylate in a molar ratio of 1:4.

[0091] Mix the substances weighed in step (1) and put them into a 25 mL serum bottle. Add a magnetic stirrer of appropriate size, and then stir at 50 °C at a speed of 500 revolutions per minute for 10 minutes to obtain a clarified solution.

[0092] Let the clarified solution obtained in step (2) cool naturally to room temperature, and then stir for 10 minutes at room temperature to obtain a clarified and transparent electrolyte solution at room temperature.

[0093] Use the prepared electrolyte as the electrolyte for an aluminum metal ion battery, with an aluminum foil as the negative electrode, and assemble a symmetric battery.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing an electrolyte for an aluminum ion battery.

[0096] The method includes the following steps:

[0097] Weigh aluminum perchlorate nonahydrate and ethyl acrylate in a molar ratio of 1:4.

[0098] Mix the substances weighed in step (1) and put them into a 25 mL serum bottle. Add a magnetic stirrer of appropriate size, and then stir at 50 °C at a speed of 500 revolutions per minute for 10 minutes to obtain a clarified solution.

[0099] Let the clarified solution obtained in step (2) cool naturally to room temperature, and then stir for 10 minutes at room temperature to obtain a clarified and transparent electrolyte solution at room temperature.

[0100] Use the prepared electrolyte as the electrolyte for an aluminum metal ion battery, with an aluminum foil as the negative electrode, and assemble a symmetric battery.

[0101] Comparative Example 3

[0102] This comparative example provides a method for preparing an electrolyte for an aluminum ion battery.

[0103] The method includes the following steps:

[0104] Weigh aluminum perchlorate nonahydrate, methyl carbamate, and ethyl acrylate according to a molar ratio of 1:2:2.

[0105] Mix the substances weighed in step (1) and place them in a 25 mL serum bottle. Add a magnetic stir bar of appropriate size, and then stir at a speed of 500 revolutions per minute at 50 °C for 10 minutes to obtain a clear solution.

[0106] Let the clear solution obtained in step (2) cool naturally to room temperature, and then stir at room temperature for 10 minutes to obtain a clear and transparent electrolyte solution at room temperature.

[0107] Use the prepared electrolyte solution as the electrolyte for an aluminum metal ion battery, with an aluminum foil as the negative electrode, and assemble a symmetric battery.

[0108] Comparative Example 4

[0109] This comparative example provides a method for preparing an electrolyte solution for an aluminum ion battery.

[0110] The method includes the following steps:

[0111] Weigh aluminum perchlorate nonahydrate, methyl acrylate, and ethyl acrylate according to a molar ratio of 1:2:2.

[0112] Mix the substances weighed in step (1) and place them in a 25 mL serum bottle. Add a magnetic stir bar of appropriate size, and then stir at a speed of 500 revolutions per minute at 50 °C for 10 minutes to obtain a clear solution.

[0113] Let the clear solution obtained in step (2) cool naturally to room temperature, and then stir at room temperature for 10 minutes to obtain a clear and transparent electrolyte solution at room temperature.

[0114] Use the prepared electrolyte solution as the electrolyte for an aluminum metal ion battery, with an aluminum foil as the negative electrode, and assemble a symmetric battery.

[0115] Comparative Example 5

[0116] Same as Example 1, the aluminum metal salt is aluminum perchlorate nonahydrate, except that no eutectic substance is added, and an aluminum perchlorate electrolyte solution with a molar concentration of 1 M is prepared using water as the main solvent.

[0117] Mix the substances weighed in step (1) and place them in a 25 mL serum bottle. Add a magnetic stir bar of appropriate size, and then stir at a speed of 500 revolutions per minute at 30 °C for 10 minutes to obtain a clear solution.

[0118] Use the prepared electrolyte solution as the electrolyte for an aluminum metal ion battery, with an aluminum foil as the negative electrode, and assemble a symmetric battery.

[0119] Comparative Example 6

[0120] Compared with Example 1, the only difference is that the ratio of aluminum perchlorate nonahydrate to methyl carbamate is changed to 1:6, and other operations and parameters are the same as those in Example 1.

[0121] The prepared electrolyte is used as the electrolyte of an aluminum metal ion battery, and an aluminum foil is used as the negative electrode to assemble a symmetric battery.

[0122] The prepared electrolyte is used as the electrolyte of an aluminum metal ion battery, an aluminum foil is used as the negative electrode, and polyaniline or diquinoxalino[2,3-a:2',3'-c]phenazine is used as the positive electrode to assemble a full cell.

[0123] Comparative Example 7

[0124] Compared with Example 1, the only difference is that the ratio of aluminum perchlorate nonahydrate to methyl carbamate is changed to 1:8, and other operations and parameters are the same as those in Example 1.

[0125] The prepared electrolyte is used as the electrolyte of an aluminum metal ion battery, and an aluminum foil is used as the negative electrode to assemble a symmetric battery.

[0126] The prepared electrolyte is used as the electrolyte of an aluminum metal ion battery, an aluminum foil is used as the negative electrode, and polyaniline or diquinoxalino[2,3-a:2',3'-c]phenazine is used as the positive electrode to assemble a full cell.

[0127] Comparative Example 8

[0128] Compared with Example 1, the difference is that the aluminum metal salt aluminum perchlorate nonahydrate is modified as follows:

[0129] Group A: aluminum chloride hexahydrate;

[0130] Group B: aluminum nitrate nonahydrate;

[0131] Group C: aluminum sulfate octadecahydrate.

[0132] Stir at 50 °C for 10 minutes, cool to room temperature and then stir for another 10 minutes.

[0133] As Figure 20 shown, after cooling, only the electrolyte formed by aluminum perchlorate nonahydrate and the eutectic substance remains clear, and aluminum perchlorate nonahydrate is the preferred aluminum metal salt.

[0134] Application Example 1

[0135] The electrolytes obtained in Examples 1 to 3 and Comparative Examples 1 to 5, with glass fiber as the separator and aluminum metal foil as the negative electrode, are used to assemble a symmetric battery. The electrochemical performance is tested using a Neware battery test system, and the test conditions are a current density of 0.5 mA / cm 2 , the charge and discharge time are both 1 h, and the temperature is 30 °C.

[0136] Table 1 Data table of the cycle life of the symmetric battery

[0137] Cycle life (h) Example 1 138 Example 2 124 Example 3 85 Comparative Example 1 62 Comparative Example 2 42 Comparative Example 3 73 Comparative Example 4 66 Comparative Example 5 75

[0138] It can be concluded from Table 1 that the symmetrical battery assembled in Example 1 has the longest cycle life. At the same time, through Figure 9 scanning electron microscope images, it can be obtained that the surface of the aluminum foil after cycling in Example 1 is smoother and more orderly. This is because in the electrolyte formed by methyl carbamate, its weak binding with aluminum ions leads to the formation of a solvation structure dominated by anions, and its faster kinetic behavior plays a key role in the uniformity of deposition and stripping. Secondly, the adsorption and decomposition of methyl carbamate and perchlorate on the aluminum surface can form a solid electrolyte membrane rich in perchlorate, which can accelerate ion transport and protect the aluminum negative electrode from corrosion by water.

[0139] Application Example 2

[0140] The electrolytes obtained in Example 1 and Comparative Examples 5-7 were used, with glass fiber as the separator and aluminum metal foil as the negative electrode to assemble a symmetrical battery. The electrochemical performance was tested using a Neware battery test system, and the test conditions were a current density of 0.2 mA / cm 2 , a charge-discharge time of 1 h each, and a temperature of 30 °C.

[0141] Table 2 Data table of the cycle life of the symmetrical battery

[0142] Cycle life (h) Example 1 600 Comparative Example 5 130 Comparative Example 6 225 Comparative Example 7 235

[0143] It can be seen from Table 2 that the symmetrical battery assembled in Example 1 has the longest cycle life. By optimizing the ratio of aluminum metal salt to methyl carbamate, it can be obtained that Example 1 is the preferred ratio. At the same time, through Figure 14 XPS, it can be obtained that compared with Comparative Example 5, the surface of the aluminum foil after cycling in Example 1 has a perchlorate signal and a nitrogen signal, which proves the formation of a solid electrolyte layer (SEI) rich in anions and dense, preventing water from reacting with aluminum, and can prove that it plays a protective role for the aluminum negative electrode. Figure 15 From the scanning electron microscope images and optical images, it can be obtained that the aluminum foil immersed in Example 1 at different temperatures has less corrosion compared with Comparative Example 5, which is also because the adsorption of methyl carbamate on the aluminum surface prevents the further reaction of aluminum with water.

[0144] Application Example 3

[0145] The electrolytes obtained in Example 1 and Comparative Examples 6-7 were used, with glass fiber as the separator, aluminum metal foil as the negative electrode, and polyaniline or diquinoxalino[2,3-a:2',3'-c]phenazine as the positive electrode. The electrochemical performance was tested using a Neware battery test system. When the positive electrode was polyaniline, the test conditions were a current density of 500 mA / g, a voltage range of 0.4 V - 1.5 V, and a temperature of 30 °C; when the positive electrode was diquinoxalino[2,3-a:2',3'-c]phenazine, the test conditions were a current density of 100 mA / g, a voltage range of 0.3 V - 1.5 V, and a temperature of 30 °C.

[0146] It can be obtained that when assembling a full cell with aluminum foil as the negative electrode, polyaniline as the positive electrode, and the electrolyte of Example 1, it has a longer cycle life and specific capacity (800 cycles and specific capacity > 130 mAh / g). It can be obtained through Figures 16 - 18 It can be obtained that when assembling a full cell with aluminum foil as the negative electrode, diquinoxalino[2,3-a:2',3'-c]phenazine as the positive electrode, and the electrolyte of Example 1, it has smaller polarization and a higher specific capacity (309 mAh / g). Therefore, it can be proved that Example 1 performs more excellently and is the preferred ratio. Figure 19

[0147] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.​

Claims

1. A eutectic aqueous aluminum ion battery electrolyte, characterized in that: The aqueous aluminum ion battery electrolyte comprises aluminum metal salt and a eutectic substance; The aluminum metal salt includes at least one of aluminum chloride hexahydrate, aluminum perchlorate nonahydrate, aluminum nitrate nonahydrate and aluminum sulfate 18hydrate; The low eutectic material is an organic small molecule compound containing amino groups and ester groups.

2. The eutectic aqueous aluminum ion battery electrolyte according to claim 1, characterized in that: The low eutectic substance is selected from methyl carbamate or ethyl carbamate; the molar ratio of the aluminum metal salt to the low eutectic substance is 1:1-8.

3. The eutectic aqueous aluminum ion battery electrolyte according to claim 1, characterized in that: The eutectic material is selected from methyl urethane and ethyl urethane.

4. The eutectic aqueous aluminum ion battery electrolyte according to claim 3, characterized in that: The molar ratio of the aluminum metal salt, methyl carbamate and ethyl carbamate is 1:2:

2.

5. The method for preparing a eutectic aqueous aluminum ion battery electrolyte according to any one of claims 1 to 4, characterized in that: The aqueous aluminum ion battery electrolyte is prepared by mixing aluminum metal salt with a low eutectic material.

6. The preparation method according to claim 5, characterized in that: The mixing process is: heating at 30-90° C. for 10-40 minutes, naturally cooling to room temperature, and then stirring for 10-30 minutes.

7. An aqueous aluminum ion secondary battery, characterized in that: It comprises a low eutectic aqueous aluminum ion battery electrolyte as described in any one of claims 1 to 4 or a low eutectic aqueous aluminum ion battery electrolyte prepared by the preparation method as described in claim 5 or 6.

8. The aqueous aluminum ion secondary battery according to claim 7, characterized in that: The aqueous aluminum ion secondary battery is a symmetrical battery composed of aluminum metal foil, glass fiber separator and aqueous aluminum ion battery electrolyte.

9. The aqueous aluminum ion secondary battery according to claim 7, characterized in that: The aqueous aluminum ion secondary battery is a full battery composed of an aluminum metal foil as a negative electrode, a positive electrode, a glass fiber separator and an aqueous aluminum ion battery electrolyte.

10. The aqueous aluminum ion secondary battery according to claim 9, characterized in that: The positive electrode material is selected from at least one of manganese dioxide, Prussian blue, polyaniline, activated carbon and diquinoxalino[2,3-A:2',3'-C]phenazine.

Images