A water-based electrolyte for water-based aluminum ion batteries, a preparation method and application thereof

Abstract

This invention relates to an aqueous electrolyte for aluminum-ion batteries, its preparation method, and its application. The invention belongs to the field of aqueous aluminum-ion battery electrolytes. The purpose of this invention is to solve the technical problem of unfavorable hydrogen evolution reaction (HER) easily occurring in aluminum in aqueous electrolytes in existing aqueous aluminum-ion batteries. The electrolyte of this invention consists of water-soluble aluminum salts, water, oxane compounds, and hydrogen bond acceptors. The oxane compounds, through their unstable α-hydrogen groups, strongly coordinate with the ether oxygen functional groups, helping to reduce the reducing activity of nitrile hydrogen bond acceptors. Furthermore, during mixing with aluminum salts and water, a large number of hydrogen bond acceptors significantly disrupt the hydrogen bond network of water molecules, inhibiting water decomposition activity and improving the electrochemical stability of the electrolyte. Due to the strong coordination effect of the -CN groups, reversible deposition / stripping of aluminum ions is ensured while suppressing the HER reaction. This invention is applicable to the field of aqueous electrolytes.

Description

Technical Field

[0001] This invention belongs to the field of aqueous aluminum-ion battery electrolytes, specifically relating to an aqueous aluminum-ion battery electrolyte, its preparation method, and its application. Background Technology

[0002] As a highly promising candidate among aqueous metal batteries, aqueous aluminum-ion batteries possess unique energy storage potential: a theoretical capacity second only to lithium metal (2980 mAh g⁻¹). -1 ), and ultra-high volumetric energy density (8056mAh cm⁻¹) -3 It has attracted much attention due to its advantages such as being environmentally friendly, having high abundance, and being low cost.

[0003] Theoretically, constructing a rechargeable aqueous aluminum-ion battery based on an aluminum metal anode and a dilute aqueous electrolyte is not feasible. The specific reasons are as follows: In an aqueous electrolyte, the dense alumina film spontaneously forms on the surface of aluminum, lacking ionic conductivity and hindering the electrochemical performance of the aluminum metal; in dilute aqueous solutions, the aluminum ion solvation structure consists of a primary solvation sheath and a secondary solvation sheath, each containing six water molecules. During charging, hydrated aluminum ions adsorbed on the aluminum metal anode surface release highly reactive water molecules, while Al... 3+ The standard electrode potential of / Al (-1.68V) is lower than that of H. + The presence of H2 leads to the preferential occurrence of the unfavorable hydrogen evolution reaction before aluminum deposition; furthermore, the high surface charge density of aluminum ions results in slow chemical kinetics and poorer cathode material matching. Therefore, it is crucial to explore a novel electrolyte for aqueous aluminum-ion batteries that can significantly suppress the hydrogen evolution reaction while achieving reversible aluminum ion deposition / stripping. Summary of the Invention

[0004] In view of the above-mentioned shortcomings pointed out in the background art, the present invention provides an aqueous electrolyte for aluminum-ion batteries, its preparation method and application, aiming to achieve reversible deposition / stripping of aluminum ions in dilute aqueous solutions, solve the problems of narrow voltage window of existing aqueous electrolytes and suppress hydrogen evolution side reactions.

[0005] The technical solution of the present invention is as follows:

[0006] One of the objectives of this invention is to provide an aqueous electrolyte for an aqueous aluminum-ion battery, wherein the electrolyte is composed of water-soluble aluminum salts, water, oxanes, and hydrogen bond acceptors.

[0007] Further specifying, the oxanes are at least one of 1,3-dioxane, dioxane, 1,4-thiaoxane, and 1,3,5-trioxane.

[0008] Further specifying, the hydrogen bond acceptor is at least one of acetonitrile, butenedionitrile, malononitrile, succinic anionyl glutaronitrile, and adiponitrile.

[0009] Further specifying, the water-soluble aluminum salt is at least one of aluminum trifluoromethanesulfonate, aluminum nitrate, aluminum perchlorate, and aluminum sulfate.

[0010] Further specifying, the mass ratio of oxanes to hydrogen bond acceptors is 1:(0.5-3).

[0011] Further specifying, the total volume ratio of oxanes and hydrogen bond acceptors to water is 1:(4-9).

[0012] Further, the concentration of soluble aluminum salts in the electrolyte is specified to be 0.2-13 mol / L.

[0013] The second objective of this invention is to provide a method for preparing the aqueous electrolyte for the above-mentioned aqueous aluminum-ion battery, wherein the preparation method is carried out by mixing water-soluble aluminum salt, water, oxane substances and hydrogen bond acceptors.

[0014] The third objective of this invention is to provide an application of the above-mentioned aqueous aluminum-ion battery using an aqueous electrolyte in symmetrical cells, half-cells, and aqueous aluminum-ion batteries.

[0015] The fourth objective of this invention is to provide a symmetrical battery, which includes aluminum foil and the aqueous electrolyte used in the above-mentioned aqueous aluminum-ion battery.

[0016] The fifth objective of this invention is to provide a half-cell, which includes a current collector and the aqueous electrolyte used in the above-mentioned aqueous aluminum-ion battery.

[0017] Further specifying, the current collector includes titanium foil, copper foil, nickel foil, molybdenum foil, carbon paper, carbon cloth, stainless steel mesh, copper mesh, nickel mesh, copper foam, and nickel foam.

[0018] The sixth objective of this invention is to provide an aqueous aluminum-ion battery, which includes a positive electrode, a negative electrode, a separator, and an aqueous electrolyte.

[0019] Further specifying, the positive electrode is formed by coating a slurry obtained by grinding a positive electrode material, a conductive agent, and a binder onto a current collector, wherein the positive electrode material is at least one of Prussian blue, MnO, polyaniline, and V2O5.

[0020] Further specifying, the slurry loading on the current collector is 0.3-7 mg / cm³. 2 .

[0021] Further specifying, the conductive agent is selected from one or more of the following: conductive carbon black Super-P Li, conductive carbon black Super-P C45, acetylene black, Ketjen black, and carbon nanotubes.

[0022] Further specifying, the binder is selected from one or more of sodium carboxymethyl cellulose, polytetrafluoroethylene, LA133, and polyvinylidene fluoride.

[0023] Further specifying, the diaphragm is one of glass fiber diaphragm, dust-free paper, or proton exchange membrane.

[0024] The advantages of this invention compared to the prior art are:

[0025] (1) This invention provides an aqueous electrolyte for an aluminum-ion battery, wherein oxanes, through their unstable α-hydrogen groups, strongly coordinate with the ether oxygen functional groups therein, helping to reduce the reducing activity of nitrile hydrogen bond acceptors. Furthermore, during mixing with aluminum salts and water, a large number of hydrogen bond acceptors significantly disrupt the hydrogen bond network of water molecules, inhibiting water decomposition activity and improving the electrochemical stability of the electrolyte.

[0026] (2) The presence of a large number of oxanes and hydrogen bond acceptor components leads to changes in the solvation structure of aluminum ions in dilute aqueous solutions. Due to the strong coordination effect of the -CN group, oxanes and hydrogen bond acceptor components enter the solvation shell of aluminum ions, thereby reducing the amount of coordinated water. This ultimately reduces the content of adsorbed water molecules at the interface during the desolvation process while accelerating the desolvation process of aluminum ions, ensuring the reversible deposition / stripping of aluminum ions while limiting and inhibiting the hydrogen evolution negative reaction.

[0027] (3) The aqueous aluminum-ion battery of the present invention uses an aqueous electrolyte with extremely strong stability and significantly improves the corrosion resistance and cycle stability of the aluminum anode. It is suitable for long-term storage and use of aqueous aluminum-ion battery electrolyte, improves the electrochemical performance and cycle stability of aluminum anode, and achieves more than 400 hours of symmetrical battery cycle and 300 cycles of full battery cycle, effectively improving the performance of aqueous aluminum-ion battery. Attached Figure Description

[0028] Figure 1 The electrochemical stability window of the commercial aluminum sheet used in Example 1 in the aqueous aluminum-ion battery obtained in Example 1 in the aqueous electrolyte and 1M aluminum trifluoromethanesulfonate aqueous solution;

[0029] Figure 2 The electrokinetic polarization curves of the commercial aluminum sheet in Example 2 in the aqueous aluminum-ion battery obtained in Example 1 are shown in the aqueous electrolyte and 1M aluminum trifluoromethanesulfonate aqueous solution.

[0030] Figure 3 Time-voltage comparison graph for cycle stability testing of the symmetrical battery assembled in Application Example 2;

[0031] Figure 4Graphs showing the specific capacity and efficiency of the aqueous aluminum-ion battery assembled in Application Example 3 during cycling.

[0032] Figure 5 Time-voltage comparison graph for cycle stability testing of the symmetrical battery assembled in Application Example 4. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0035] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0036] Example 1: The preparation method of the aqueous electrolyte in this example is carried out according to the following steps:

[0037] (1) Take 1.2g of 1,3,5-trioxane and 1.2g of succinate in a beaker and stir continuously at 25°C until a clear solution is formed.

[0038] (2) Then add 0.8 mL of deionized water and 0.948 g of aluminum trifluoromethanesulfonate to 1.2 mL of the solution prepared in step (1), stir until the solution is clear and uniform, and let it stand for 6 h to obtain a stable aqueous electrolyte for aluminum-ion batteries.

[0039] Example 2:

[0040] The difference between this embodiment and Example 1 is that 1,3,5-trioxane is replaced with dioxane. All other preparation methods are exactly the same as in Example 1, resulting in an aqueous electrolyte for an aqueous aluminum-ion battery.

[0041] Application Example 1:

[0042] Commercial aluminum sheets were used as the negative electrode and commercial molybdenum foil as the positive electrode. The aqueous aluminum-ion batteries obtained in Example 1 were used to assemble half-cells with aqueous electrolyte and 1M aluminum trifluoromethanesulfonate aqueous solution, respectively.

[0043] Electrochemical window testing was performed on the half-cell assembled above, and the results are as follows: Figure 1 As shown, at a scan rate of 10 mV / s, compared to the 1 M aluminum trifluoromethanesulfonate aqueous electrolyte, the aqueous aluminum-ion battery obtained in Example 1 expands the electrochemical window to 2.86 V using the aqueous electrolyte, significantly improving the electrochemical stability of the electrolyte.

[0044] Application Example 2:

[0045] Commercial aluminum sheets were used as negative electrodes to assemble symmetrical cells in the aqueous aluminum-ion battery obtained in Example 1, using both aqueous electrolyte and 1M aluminum trifluoromethanesulfonate aqueous solution.

[0046] The electrokinetic polarization curves of the symmetrical cells assembled above were measured, and the results are as follows: Figure 2 As shown in the figure, the aqueous electrolyte obtained in Example 1 significantly reduced the corrosion current and reduced the damage of the aqueous electrolyte to the aluminum anode.

[0047] Electrochemical tests were performed on the symmetrical cells assembled above, and the results are as follows: Figure 3 As shown, it can be seen that at 0.1 mAcm -2 The aluminum anode was continuously charged and discharged for 1 hour each at a current density of 0.1 mA / cm² to test its cycle stability and cycle life in the electrolyte. Commercial aluminum sheets exhibited superior cycle stability and life in the aqueous electrolyte of the aqueous aluminum-ion battery obtained in Example 1 of this invention, at 0.1 mA / cm². -2 It can be stably cycled for ≥400h at a current density.

[0048] Application Example 3:

[0049] (1) Using Prussian blue as the positive electrode material, Prussian blue, conductive carbon black Super-P Li, and sodium carboxymethyl cellulose were ground into a slurry at a mass ratio of 6:2:2. Then, the slurry was prepared at a concentration of 1.2 mg / cm³. 2 The loading capacity is coated onto carbon paper to obtain a positive electrode sheet;

[0050] (2) Using commercial aluminum sheets as the negative electrode and glass fiber as the separator, the positive electrode sheet, negative electrode sheet, separator and the aqueous aluminum-ion battery obtained in Example 1 are assembled with aqueous electrolyte to obtain an aqueous aluminum-ion battery.

[0051] The electrochemical performance of the assembled aqueous aluminum-ion battery was tested. Charge-discharge tests were performed at a current density of 0.1 A / g, and the results are as follows: Figure 4 As shown, the system can cycle stably for up to 300 cycles without significant capacity decay.

[0052] Application Example 4:

[0053] Commercial aluminum sheets were used as negative electrodes to assemble symmetrical cells in the aqueous aluminum-ion battery obtained in Example 2, using both aqueous electrolyte and 1M aluminum trifluoromethanesulfonate aqueous solution.

[0054] Electrochemical tests were performed on the symmetrical cells assembled above, and the results are as follows: Figure 5 As shown, under the same test conditions, the cycle time can also reach 300h, which is similar to the results in Example 1. It still has excellent cycle performance that significantly surpasses that of aqueous aluminum trifluoromethanesulfonate electrolyte.

[0055] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An aqueous electrolyte for an aqueous aluminum-ion battery, characterized in that, It consists of water-soluble aluminum salt, water, oxanes and hydrogen bond acceptors, wherein the hydrogen bond acceptor is at least one of acetonitrile, butadiene nitrile, malononitrile, succinate, glutaronitrile and adiponitrile.

2. The electrolyte according to claim 1, characterized in that, The oxanes are at least one of 1,3-dioxane, dioxane, 1,4-thiaoxane, and 1,3,5-trioxane, and the water-soluble aluminum salts are at least one of aluminum trifluoromethanesulfonate, aluminum nitrate, aluminum perchlorate, and aluminum sulfate.

3. The electrolyte according to claim 1, characterized in that, The mass ratio of oxanes to hydrogen bond acceptors is 1:(0.5-3).

4. The electrolyte according to claim 1, characterized in that, The total volume ratio of oxanes and hydrogen bond acceptors to water is 1:(4-9), and the concentration of soluble aluminum salts in the electrolyte is 0.2-13 mol / L.

5. The method for preparing the aqueous electrolyte according to any one of claims 1-4, characterized in that, This was accomplished by mixing water-soluble aluminum salts, water, oxanes, and hydrogen bond acceptors.

6. The application of the aqueous electrolyte according to any one of claims 1-4 in symmetrical cells, half-cells and aqueous aluminum-ion batteries.

7. A symmetrical battery, characterized in that, Includes aluminum foil and the aqueous electrolyte as described in any one of claims 1-4.

8. A half-cell, characterized in that, Includes a current collector and the aqueous electrolyte as described in any one of claims 1-4.

9. An aqueous aluminum-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a diaphragm, and an aqueous electrolyte as described in any one of claims 1-4.

10. The aqueous aluminum-ion battery according to claim 9, characterized in that, The positive electrode is formed by coating a slurry obtained by grinding a positive electrode material, a conductive agent and a binder onto a current collector, wherein the positive electrode material is at least one of Prussian blue, MnO, polyaniline and V2O5.

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