Wide-temperature-range eutectic electrolyte for aluminum ion battery and application of wide-temperature-range eutectic electrolyte

Abstract

The invention discloses a wide-temperature-range eutectic electrolyte for an aluminum ion battery and application of the wide-temperature-range eutectic electrolyte, and relates to the technical field of aqueous aluminum ion battery electrolytes, the electrolyte comprises the following components: aluminum trifluoromethanesulfonate, deionized water, a lipid-based organic solvent and a hydroxyl organic solvent; the lipid-based organic solvent is dimethyl methylphosphonate, and the hydroxyl organic solvent is ethylene glycol. The invention also discloses an application of the wide-temperature-range eutectic electrolyte in an aqueous aluminum ion battery. The eutectic electrolyte is prepared by introducing the two organic solvents and the aluminum salt, the working temperature interval of the electrolyte is remarkably widened, and organic solvent molecules in the electrolyte can change the solvation structure of aluminum ions and reduce the amount of active water, so that the generation of hydrogen evolution reaction is inhibited, and the service life of the electrolyte is prolonged. And the stability and the cycle capability of the chloride ion battery are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous aluminum ion battery electrolytes, and in particular to a wide-temperature-range eutectic electrolyte for aluminum ion batteries and applications thereof. Background Art

[0002] With the rapid expansion of renewable energy capacity worldwide, the demand for grid-connected intermittent power sources like wind and photovoltaics has surged, and the importance of energy storage systems in grid peak shaving, frequency regulation, and backup capacity has become increasingly prominent. While traditional lithium-ion batteries dominate the market, they are limited by the uneven geographical distribution of lithium resources, fluctuating costs, and safety risks. The industry is exploring alternative technologies with more abundant resources and lower costs. Aluminum is an ideal candidate for energy storage batteries, as its reserves account for 8% of the Earth's crust (approximately 1,300 times that of lithium), its theoretical mass energy density reaches 8.1 kWh / kg (close to that of lithium metal), and it poses no risk of thermal runaway.

[0003] The practical development of aluminum-ion batteries today faces numerous challenges, including severe capacity fading, low Coulombic efficiency, severe hydrogen evolution, and uneven deposition / stripping processes. To address these challenges, researchers have conducted a series of explorations and experiments. These include optimizing the aluminum anode structure, increasing the specific surface area to reduce current density, and promoting more uniform aluminum ion deposition; employing cathode materials with higher theoretical capacity and more positive electrode potential; and employing appropriate electrolytes to suppress water activity, modify the aluminum ion solvation structure, and form a SEI film.

[0004] Selecting the right electrolyte is crucial for optimizing the performance of aluminum-ion batteries, taking into account the physical and chemical properties of the battery's aluminum metal anode, cathode material, and separator. Energy storage batteries are often subject to temperature fluctuations. Rising temperatures facilitate hydrogen evolution reactions at the anode, consuming electrolyte content and causing hydrogen accumulation in the battery, leading to battery deactivation. Lower temperatures increase electrolyte viscosity, decrease ion migration rates, and even cause aqueous electrolyte solidification, rendering the battery inoperable. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a wide-temperature range eutectic electrolyte for aluminum ion batteries and its application. The present invention prepares a eutectic electrolyte by introducing two organic solvents and aluminum salts, which significantly broadens the operating temperature range of the electrolyte. In addition, the organic solvent molecules in the electrolyte can change the solvation structure of aluminum ions and reduce the amount of active water, thereby inhibiting the occurrence of hydrogen evolution reaction, and significantly improving the stability and cycle capacity of chloride ion batteries.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: a wide temperature range eutectic electrolyte for aluminum ion batteries is provided, comprising the following components: aluminum trifluoromethanesulfonate, deionized water, a lipid-based organic solvent and a hydroxyl organic solvent; the lipid-based organic solvent is dimethyl methylphosphonate, and the hydroxyl organic solvent is ethylene glycol.

[0007] Furthermore, the concentration of aluminum trifluoromethanesulfonate in the wide temperature range eutectic electrolyte is 0.5-3 mol / L.

[0008] Furthermore, the volume fraction of the lipid-based organic solvent is 10%-30%, the volume fraction of the hydroxyl organic solvent is 5%-20%, and the balance is deionized water.

[0009] Furthermore, the preparation method comprises the following steps:

[0010] Aluminum trifluoromethanesulfonate is added to a mixed solution of a lipid-based organic solvent and a hydroxyl organic solvent, heated to 70-90° C. and stirred to dissolve, and then deionized water is added and ultrasonically treated to obtain a wide-temperature-range eutectic electrolyte for aluminum ion batteries.

[0011] The present invention also provides the use of the wide temperature range eutectic electrolyte for aluminum ion batteries in aqueous aluminum ion batteries.

[0012] The present invention also provides an aqueous aluminum ion battery, comprising the above-mentioned wide-temperature-range eutectic electrolyte for aluminum ion batteries.

[0013] Furthermore, it also includes a separator and a polyaniline positive electrode material.

[0014] The present invention has the following beneficial effects:

[0015] 1. The electrolyte of the present invention forms a eutectic solution with aluminum trifluoromethanesulfonate by introducing ethylene glycol and dimethyl methylphosphonate, which can significantly lower the freezing point of the electrolyte. The two change the solvation structure of aluminum ions, reduce the amount of solvated water, and form hydrogen bonds with water molecules. Dimethyl methylphosphonate can decompose to form an SEI film, inhibit hydrogen evolution corrosion and reduce the activity of water in the electrolyte, thereby improving the stability of the aluminum negative electrode, reducing corrosion, and greatly improving the stability and reversibility of the aluminum ion battery.

[0016] 2. During the early charge and discharge process of the battery, the electrolyte of the present invention will gradually form a SEI film on the surface of the aluminum negative electrode, preventing water molecules from contacting the aluminum anode, improving the flatness during the aluminum ion deposition process, reducing the corrosion of the aluminum anode, and improving the stability and cycle capacity of the battery.

[0017] 3. The electrolyte components of the present invention are all conventional medicines, and the preparation methods are all conventional methods. The operation is simple and easy to prepare on a large scale. The solution has stable physical and chemical properties and can be used at different operating temperatures to show good electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The solution resistance diagrams of different electrolytes measured at 25°C in Experimental Example 1;

[0019] Figure 2 The solution state diagrams of different electrolytes in Experimental Example 1 at -25°C and 25°C;

[0020] Figure 3 This is a comparison diagram of hydrogen evolution overpotentials of different electrolytes in Experimental Example 1;

[0021] Figure 4 This is a comparison chart of corrosion currents of different electrolytes in Test Example 1;

[0022] Figure 5 This is a comparison chart of hydrogen evolution during aluminum ion deposition in different electrolytes in Experimental Example 1;

[0023] Figure 6 This is the XRD pattern of the aluminum negative electrode surface after the electrolyte in Example 1 was assembled into a full battery and cycled 50 times;

[0024] Figure 7 The Zn / Zn symmetric battery assembled with different electrolytes in Experimental Example 1 was tested at 25°C and 0.05 mA cm -2 The cycle performance diagram below;

[0025] Figure 8 The Zn / Zn symmetric battery assembled with different electrolytes in Experimental Example 1 was tested at -25℃ and 0.05mA cm -2 The cycle performance diagram below;

[0026] Figure 9 The Zn / Zn symmetric battery assembled with different electrolytes in Experimental Example 1 was tested at 25°C and 0.1 mA cm -2 The cycle performance diagram below;

[0027] Figure 10 The Zn / / PANI full battery assembled with different electrolytes in Experimental Example 1 was tested at 25°C and 0.1Ag. -1 The cycle performance diagram below;

[0028] Figure 11 The Zn / / PANI full battery assembled with different electrolytes in Experimental Example 1 was tested at -20℃ and 0.1Ag. -1 The cycle performance diagram below;

[0029] Figure 12 The Zn / / PANI full battery assembled with different electrolytes in Experimental Example 1 was tested at 40°C and 0.1Ag -1 The cycle performance diagram below;

[0030] Figure 13The Zn / / PANI full battery assembled with different electrolytes in Experimental Example 1 was tested at 25°C and 0.5Ag -1 The cycle performance diagram below;

[0031] Figure 14 The Zn / Zn symmetric battery assembled with or without the addition of dimethyl methylphosphonate electrolyte was tested at 25℃ and 0.1mAcm -2 The following cycle performance comparison chart. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below. The examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. In the examples, where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer were used. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0033] In this embodiment, the electrochemical test was completed using a CHI760E electrochemical workstation. In order to evaluate the cycle stability of the aluminum negative electrode, the surface oxide layer of the aluminum foil was polished with 500-mesh sandpaper before use. The electrolyte system prepared in this embodiment was used to assemble a CR2032 button battery with glass fiber as a diaphragm. In order to verify the practicality of the material system in a full battery, the active material (polyaniline), activated carbon and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 8:1:1 to prepare a slurry, which was evenly coated on the surface of the titanium foil. After vacuum drying, it was used as the positive electrode and assembled into a button-type full battery with the polished aluminum foil and the electrolyte of this embodiment. The test voltage window was 0.1-1.05V vs.Al 3+ / Al.

[0034] Example 1

[0035] A wide temperature range eutectic electrolyte for aluminum ion batteries, comprising the following components: 1 mol / L aluminum trifluoromethanesulfonate, 70vt% deionized water, 15vt% dimethyl methylphosphonate, and 15vt% ethylene glycol;

[0036] The preparation method includes the following steps: adding aluminum trifluoromethanesulfonate to a mixed solution of a lipid-based organic solvent and a hydroxyl organic solvent, heating to 80°C and stirring to dissolve, then adding deionized water for ultrasonic treatment to obtain a wide-temperature-range eutectic electrolyte for aluminum ion batteries.

[0037] Example 2

[0038] A wide-temperature-range eutectic electrolyte for aluminum ion batteries comprises the following components: 0.5 mol / L aluminum trifluoromethanesulfonate, 85vt% deionized water, 10vt% dimethyl methylphosphonate, and 5vt% ethylene glycol.

[0039] Example 3

[0040] A wide-temperature-range eutectic electrolyte for aluminum ion batteries comprises the following components: 2 mol / L aluminum trifluoromethanesulfonate, 50vt% deionized water, 30vt% dimethyl methylphosphonate, and 20vt% ethylene glycol.

[0041] Example 4

[0042] An aqueous aluminum ion battery comprises the wide-temperature-range eutectic electrolyte for aluminum ion batteries of embodiment 1, a separator, and a polyaniline positive electrode material.

[0043] Test Example 1

[0044] Referring to Example 1, the electrolyte was prepared by changing the volume ratio of water (60% and 75%) while keeping the volume ratio of the two organic solvents unchanged. A 1 mol / L aqueous solution of aluminum trifluoromethanesulfonate (Al(OTf)3) was used as the electrolyte for performance comparison with the electrolyte of Example 1.

[0045] (1) Resistance of different electrolyte solutions such as Figure 1 As shown, the resistance decreases as the proportion of water increases.

[0046] (2) Different electrolyte solution states such as Figure 2 As shown, the four electrolytes all showed a clear and transparent solution state at 25°C. When the temperature was reduced to -25°C, the electrolytes prepared with three different volume fractions of water still remained in a flowable liquid phase, while the electrolyte prepared with an aqueous solution of aluminum trifluoromethanesulfonate solidified into a solid, indicating that the electrolyte prepared in Example 1 has good low-temperature resistance.

[0047] (3) The hydrogen evolution overpotential of different electrolytes is as follows Figure 3 As shown, the electrolyte prepared with 70% water has a more negative hydrogen evolution potential than the electrolyte prepared with an aqueous solution of aluminum trifluoromethanesulfonate, indicating that the electrolyte prepared in Example 1 can better inhibit the occurrence of hydrogen evolution reaction.

[0048] (4) Corrosion current of different electrolytes Figure 4 As shown, the electrolyte prepared with 70% water has a smaller corrosion current than the electrolyte prepared with an aqueous solution of aluminum trifluoromethanesulfonate, indicating that the electrolyte prepared in Example 1 is more capable of inhibiting the corrosion of the aluminum negative electrode.

[0049] (5) The hydrogen evolution during aluminum ion deposition was photographed using an optical microscope. The results are as follows: Figure 5 As shown, when the aqueous solution of aluminum trifluoromethanesulfonate is used as the electrolyte, hydrogen bubbles are quickly generated during the aluminum ion deposition process, while the electrolyte prepared in Example 1 can better inhibit the generation of hydrogen during the aluminum ion deposition.

[0050] (6) After 50 cycles of assembling a full battery using the electrolyte of Example 1, the XRD pattern of the aluminum negative electrode surface is as follows Figure 6 As shown, the XRD spectrum shows a peak of AlPO4, which indicates that the electrolyte prepared in Example 1 can generate a SEI film to protect the aluminum negative electrode in the early charge and discharge cycles.

[0051] (7) Zn / Zn symmetric batteries assembled with different electrolytes at 25°C and 0.05 mA cm -2 The cycle performance diagram below is as follows Figure 7 As shown, the aluminum trifluoromethanesulfonate aqueous solution electrolyte exhibits a shorter cycle time than the electrolyte prepared in Example 1, indicating that the electrolyte prepared in Example 1 can increase the cycle stability of the aluminum foil and protect the aluminum foil.

[0052] (8) Zn / Zn symmetric batteries assembled with different electrolytes at -25℃ and 0.05mA cm -2 The cycle performance diagram below is as follows Figure 8 As shown, the aluminum trifluoromethanesulfonate aqueous solution electrolyte exhibits a shorter cycle time than the electrolyte prepared in Example 1, indicating that the electrolyte prepared in Example 1 can increase the cycle stability of the aluminum foil and reduce corrosion.

[0053] (9) Zn / Zn symmetric batteries assembled with different electrolytes at 25°C and 0.1 mA cm -2 The cycle performance diagram below is as follows Figure 9 As shown, the aluminum trifluoromethanesulfonate aqueous solution electrolyte exhibits a shorter cycle time than the electrolyte prepared in Example 1, indicating that the electrolyte prepared in Example 1 can increase the cycle stability of the aluminum foil and reduce hydrogen evolution.

[0054] (10) Zn / / PANI full batteries assembled with different electrolytes at 25°C and 0.1Ag -1 The cycle performance diagram below is as follows Figure 10 As shown, the electrolyte prepared in Example 1 exhibits better stability and capacity retention, indicating that the electrolyte prepared in Example 1 can increase the capacity of the full battery and improve the battery stability.

[0055] (11) Zn / / PANI full batteries assembled with different electrolytes at -20℃ and 0.1Ag -1 The cycle performance diagram below is as follows Figure 11 As shown, the electrolyte prepared in Example 1 can carry out the charge and discharge process normally, indicating that the battery assembled with the electrolyte prepared in Example 1 can work normally at a lower temperature.

[0056] (12) Zn / / PANI full cells assembled with different electrolytes at 40°C and 0.1Ag -1 The cycle performance diagram below is as follows Figure 12 As shown, the electrolyte prepared in Example 1 exhibits better cycle stability, indicating that the electrolyte prepared in Example 1 can improve the high temperature resistance of the full battery.

[0057] (13) Zn / / PANI full batteries assembled with different electrolytes at 25°C and 0.5Ag -1 The cycle performance diagram below is as follows Figure 13 As shown, the electrolyte prepared in Example 1 exhibits better stability and capacity retention, indicating that the electrolyte prepared in Example 1 can work normally at a higher current density.

[0058] Test Example 2

[0059] The electrolyte without adding dimethyl methylphosphonate was prepared according to Example 1. Compared with the electrolyte of Example 1, the Zn / Zn symmetric cells assembled with different electrolytes were tested at 25°C and 0.1 mA cm -2 The cycle performance diagram below is as follows Figure 14 As shown, the electrolyte without adding dimethyl methylphosphonate exhibits a shorter cycle time than the electrolyte prepared in Example 1, indicating that the electrolyte prepared in Example 1 can increase the cycle stability of the aluminum foil and improve the cycle performance.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A wide temperature range eutectic electrolyte for aluminum ion batteries, characterized in that: The invention comprises the following components: aluminum trifluoromethanesulfonate, deionized water, a fat-based organic solvent and a hydroxyl organic solvent; the fat-based organic solvent is dimethyl methylphosphonate, and the hydroxyl organic solvent is ethylene glycol.

2. The wide temperature range eutectic electrolyte for aluminum ion batteries according to claim 1, characterized in that: The concentration of aluminum trifluoromethanesulfonate in the wide temperature range eutectic electrolyte is 0.5-3 mol / L.

3. The wide temperature range eutectic electrolyte for aluminum ion batteries according to claim 1, characterized in that: In the total electrolyte, the volume fraction of the lipid-based organic solvent is 10%-30%, and the volume fraction of the hydroxyl organic solvent is 5%-20%.

4. The wide temperature range eutectic electrolyte for aluminum ion batteries according to claim 1, characterized in that The preparation method comprises the following steps: Aluminum trifluoromethanesulfonate is added to a mixed solution of the lipid-based organic solvent and the hydroxyl organic solvent, heated to 70-90° C. and stirred to dissolve, and then deionized water is added and ultrasonically treated to obtain a wide temperature range eutectic electrolyte for aluminum ion batteries.

5. Use of the wide temperature range eutectic electrolyte for aluminum ion batteries according to claim 1 in aqueous aluminum ion batteries.

6. An aqueous aluminum ion battery, characterized in that: Including the wide temperature range eutectic electrolyte for aluminum ion batteries as described in claim 1.

7. The aqueous aluminum ion battery according to claim 6, wherein Also included are a separator and polyaniline positive electrode material.

Images