Preparation method of reverse micelle-like aqueous low-temperature electrolyte and application of energy storage device

Abstract

The invention relates to the technical field of power grid energy storage, discloses a preparation method of a reverse-micelle-like water-based low-temperature electrolyte and application in energy storage devices, and designs a unique reverse-micelle-shaped water-based low-temperature electrolyte. A proper ether cosolvent is selected as an organic phase, amphiphilic anions are selected as a similar surfactant, and an electrolyte saline solution forms a similar reverse micelle structure with a nano-scale water core; wherein the use amount of the cosolvent can be greater than or far greater than the use amount of the solvent water, and the high-concentration characteristic of the electrolyte is still maintained in a water core in the reverse-micelle-like structure, so that the obtained reverse-micelle-like mixed aqueous low-temperature electrolyte greatly widens the electrochemical stability window and the temperature range of an energy storage device, and can stably operate at extremely low temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid energy storage, and in particular to a method for preparing a reverse micelle-like aqueous low-temperature electrolyte and an application of an energy storage device. Background Art

[0002] The thermodynamic decomposition voltage of water is 1.23 V, which leads to side reactions and temperature instability in aqueous energy storage devices. These unfavorable factors together lead to relatively low energy density, suboptimal cycle life and limited operating temperature range of aqueous energy storage devices. Controlling hydrogen bonds between water molecules, revealing the solvation structure at the microscopic level and the ion transport properties at the macroscopic level are the keys to solving the above problems.

[0003] Increasing the electrolyte concentration is one of the common methods to expand the electrochemical window and temperature range by transitioning water molecules from a "free" state to a "bound" state, thereby destroying the hydrogen bonds between molecules. The destruction of this hydrogen bond network creates an energy barrier that hinders the crystallization of water molecules and subsequently lowers the freezing point. However, the practical application of high-concentration electrolytes faces some challenges, including increased viscosity, poor low-temperature ion transport performance, and increased cost.

[0004] Another method uses highly polar organic solvents as hydrogen bond acceptors or donors to provide sites for the interaction between hydrogen bonds and water molecules. These organic solvents destroy the hydrogen bond structure of water and effectively eliminate the existence of "free water". However, the amount added is usually small and cannot fully expand the electrochemical window and temperature range.

[0005] Therefore, the present invention designs a reverse micelle-like aqueous low-temperature electrolyte suitable for aqueous energy storage, selects a suitable ether co-solvent as the organic phase, and the amount of the co-solvent can be greater than or much greater than the amount of solvent water; the amphiphilic anions of the electrolyte salt are used as surfactant-like, and the salt-water-co-solvent three-phase constitutes a unique reverse micelle-like structure with a nanoscale "water core"; the high concentration characteristics of the electrolyte are still maintained in the "water core" inside the reverse micelle-like structure, thereby enhancing the electrochemical stability (electrochemical window), while reducing the apparent salt concentration, reducing the system viscosity and improving the wettability, thereby improving the ionic conductivity and low-temperature stability. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for preparing a reverse micelle-like aqueous low-temperature electrolyte and an application in an energy storage device, aiming to solve the kinetic problems of the existing aqueous low-temperature electrolyte, such as high viscosity and slow ion migration / diffusion rate, and thermodynamic problems such as easy precipitation of crystals in an ultra-low temperature environment.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a reverse micelle-like aqueous low-temperature electrolyte, comprising the steps of:

[0009] An electrolyte salt aqueous solution of a certain concentration is prepared, and the amphiphilic anions of the electrolyte salt are used as surfactant-like substances.

[0010] A suitable ether solvent is added as the organic phase, and the amount of the solvent can be greater than or much greater than the amount of solvent water.

[0011] The uniform mixing of salt-water-cosolvent three phases forms a unique reverse micelle-like structure with a nanoscale "water core".

[0012] Optionally, the amphiphilic anions in the electrolyte salt include but are not limited to one or more of trifluoromethanesulfonate and trifluoromethanesulfonimide.

[0013] Optionally, the metal cations in the electrolyte salt include, but are not limited to, one or more of lithium, sodium, potassium, magnesium, calcium, iron, zinc, tin, lead, aluminum and copper.

[0014] Optionally, the concentration of the electrolyte salt solution of a certain concentration is between 3 mol / L and 30.0 mol / L.

[0015] Optionally, the ether co-solvent includes, but is not limited to, one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

[0016] Optionally, the concentration percentage of the ether co-solvent is between 50% and 99.64%.

[0017] A reverse micelle-like aqueous low-temperature electrolyte is prepared by the method described in the present invention. The aqueous low-temperature electrolyte has excellent electrochemical and low-temperature properties and can effectively improve the low-temperature performance of an energy storage device.

[0018] The aqueous low-temperature electrolyte described in the present invention is used as an electrolyte in an aqueous energy storage device. Due to its unique reverse micelle structure characteristics with a nanoscale "water core", it can improve the stability and service life of the equipment in a low-temperature environment.

[0019] The present invention has the following beneficial effects:

[0020] The present invention designs a unique reverse micelle-like aqueous low-temperature electrolyte, which can reduce the apparent salt concentration, reduce the viscosity of the system and improve the wettability, while still maintaining the high concentration characteristics of the electrolyte in the "water core" inside the reverse micelle-like structure, thereby enhancing the electrochemical stability (electrochemical window) while improving the ionic conductivity and low-temperature stability.

[0021] The present invention selects a suitable ether co-solvent as the organic phase, which has a suitable dielectric constant and donor quantity, is miscible with water and has a moderate solubility for electrolyte salts. Therefore, the amount of the co-solvent used can be greater than or much greater than the amount of solvent water, which is conducive to the formation of a reverse micelle-like structure.

[0022] The present invention utilizes the amphiphilic anions of the electrolyte salt as a quasi-surfactant to promote the salt-water-cosolvent three-phase to form a unique quasi-reverse micelle structure with a nanoscale "water core". The electrolyte salt has multiple uses, which not only avoids the additional introduction of surfactants, but also simplifies the reaction system and saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a structural schematic diagram of the reverse micelle-like aqueous low-temperature electrolyte prepared in Example 1;

[0024] Figure 2 is a graph showing the low temperature performance of a symmetrical battery of the reverse micelle-like aqueous low temperature electrolyte prepared in Example 1;

[0025] Figure 3 This is a low-temperature rate performance diagram of the reverse micelle aqueous low-temperature electrolyte prepared in Example 1 for use in aqueous zinc ion hybrid capacitors. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a reverse micelle-like aqueous low-temperature electrolyte and an application of an energy storage device. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] The invention discloses a method for preparing a reverse micelle-like aqueous low-temperature electrolyte and an application of an energy storage device. The method comprises the following steps: preparing an electrolyte salt aqueous solution of a certain concentration, using amphiphilic anions of the electrolyte salt as a quasi-surfactant; adding a suitable ether cosolvent as an organic phase, wherein the amount of the cosolvent can be greater than or much greater than the amount of solvent water; and uniformly mixing the salt-water-cosolvent three phases to form a unique reverse micelle-like structure with a nanoscale "water core".

[0028] The working principle of the method for preparing reverse micelle-like aqueous low-temperature electrolyte provided by the present invention can be described in detail as follows:

[0029] 1) Electrolyte salt aqueous solution: First, the electrolyte salt aqueous solution of a certain concentration serves as the "water core" in the final reverse micelle-like structure and is the effective region with real electrochemical properties. Second, the amphiphilic anions of the electrolyte salt serve as surfactant-like structures, which are conducive to the formation of the final reverse micelle-like structure.

[0030] 2) Ether co-solvent: Add a suitable ether co-solvent as the organic phase, which has a suitable dielectric constant and donor quantity, can be miscible with water and has a moderate solubility in electrolyte salts. Therefore, the amount of co-solvent used can be greater than or much greater than the amount of solvent water, which is conducive to the formation of a reverse micelle-like structure.

[0031] 3) Salt-water-cosolvent uniform three-phase: The amphiphilic anions of the electrolyte salt are used as surfactant-like to promote the salt-water-cosolvent three-phase to form a unique reverse micelle-like structure with a nanoscale "water core".

[0032] Through the above steps, an aqueous low-temperature electrolyte similar to a reverse micelle structure can be prepared. This electrolyte has enhanced electrochemical stability (electrochemical window) due to its unique reverse micelle structure with a nanoscale "water core", while improving ionic conductivity and low-temperature stability.

[0033] The present invention provides a method for preparing a reverse micelle-like aqueous low-temperature electrolyte, comprising:

[0034] First, an electrolyte salt solution of a certain concentration is prepared, and the amphiphilic anions of the electrolyte salt are used as surfactant-like substances; a suitable ether co-solvent is added as the organic phase, and the amount of the co-solvent can be greater than or much greater than the amount of solvent water; on this basis, the salt-water-co-solvent three phases are evenly mixed to form a unique reverse micelle-like structure with a nanoscale "water core".

[0035] The amphiphilic anions in the electrolyte salt include but are not limited to one or more of trifluoromethanesulfonate and trifluoromethanesulfonimide; the metal cations in the electrolyte salt include but are not limited to one or more of lithium, sodium, potassium, magnesium, calcium, iron, zinc, tin, lead, aluminum and copper; the concentration of the electrolyte salt aqueous solution of a certain concentration is between 3 mol / L and 30.0 mol / L.

[0036] The ether solvent includes, but is not limited to, one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; the concentration percentage of the ether solvent is between 50% and 99.64%.

[0037] The present invention provides a reverse micelle-like aqueous low-temperature electrolyte, which is prepared by the method described in the present invention. The aqueous low-temperature electrolyte has excellent electrochemical and low-temperature properties and can effectively improve the low-temperature performance of an energy storage device.

[0038] The aqueous low-temperature electrolyte described in the present invention is used as an electrolyte in an aqueous energy storage device. Due to its unique reverse micelle structure characteristics with a nanoscale "water core", it can improve the stability and service life of the equipment in a low-temperature environment.

[0039] The embodiment of the present invention provides a method for preparing a reverse micelle-like aqueous low-temperature electrolyte, which comprises the following steps:

[0040] S1. preparing an electrolyte salt aqueous solution of a certain concentration, and using the amphiphilic anions of the electrolyte salt as a surfactant-like substance;

[0041] S2, adding a suitable ether solvent as the organic phase, the amount of the solvent can be greater than or much greater than the amount of solvent water;

[0042] S3, the three phases of salt-water-cosolvent are mixed evenly to form a unique reverse micelle-like structure with a nanoscale "water core".

[0043] In step S1, in one embodiment, the electrolyte salt aqueous solution of a certain concentration is prepared by the following method: an electrolyte salt is dissolved in an aqueous solution to obtain an electrolyte salt aqueous solution of a certain concentration; wherein the amphiphilic anions in the electrolyte salt include but are not limited to one or more of trifluoromethanesulfonate and trifluoromethanesulfonimide; the metal cations in the electrolyte salt include but are not limited to one or more of lithium, sodium, potassium, magnesium, calcium, iron, zinc, tin, lead, aluminum and copper; the concentration of the electrolyte salt aqueous solution of a certain concentration is between 3 mol / L and 30.0 mol / L.

[0044] In step S2, in one embodiment, a suitable ether cosolvent is added as an organic phase; wherein the ether cosolvent includes but is not limited to one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether; the concentration percentage of the ether cosolvent is between 50% and 99.64%. Suitable ether cosolvents have suitable dielectric constants and donor quantities, are miscible with water and have moderate solubility for electrolyte salts, so the amount of cosolvent used can be greater than or much greater than the amount of solvent water used, which is conducive to the formation of a reverse micelle-like structure.

[0045] In step S3, in one embodiment, the salt-water-solvent three phases are mixed evenly by oscillation or ultrasound to form a unique reverse micelle-like structure with a nanoscale "water core". The "water core" inside the reverse micelle-like structure still maintains the high concentration characteristics of the electrolyte.

[0046] The embodiment of the present invention provides a reverse micelle-like aqueous low-temperature electrolyte, which is prepared by the method described in the present invention. The aqueous low-temperature electrolyte has excellent electrochemical and low-temperature properties and can effectively improve the low-temperature performance of an energy storage device.

[0047] The aqueous low-temperature electrolyte described in this embodiment is used as an electrolyte in a water-based energy storage device.

[0048] The present invention will be further described below by means of specific examples.

[0049] Example 1

[0050] First, 3.0 mmol of zinc trifluoromethanesulfonate was weighed and dissolved in 10 mL of deionized water; then 60 mL of triethylene glycol dimethyl ether was measured and stirred and dispersed in the zinc trifluoromethanesulfonate solution, and the salt-water-cosolvent three-phase was evenly mixed by shaking or ultrasound to obtain a reverse micelle-like aqueous low-temperature electrolyte.

[0051] Figure 1 is a schematic diagram of the structure of the reverse micelle aqueous low-temperature electrolyte prepared in this embodiment. Figure 1 It can be seen that the salt-water-cosolvent three-phase constitutes a unique reverse micelle-like structure with a nanoscale "water core".

[0052] Figure 2 is a graph showing the low temperature performance of a zinc symmetric battery using a reverse micelle aqueous low temperature electrolyte prepared in this embodiment. Figure 2 It can be seen that this type of reverse micellar aqueous low-temperature electrolyte can operate stably at a low temperature of −70 °C for nearly a thousand hours.

[0053] Figure 3 is a graph showing the low-temperature rate performance of the reverse micelle aqueous low-temperature electrolyte prepared in this embodiment for use in aqueous zinc ion hybrid capacitors. Figure 3 It can be seen that this type of reverse micelle aqueous low-temperature electrolyte can enable the aqueous zinc ion hybrid capacitor to operate stably at a low temperature of −70 °C.

[0054] Example 2

[0055] The difference between this embodiment and embodiment 1 is that 90 mL of triethylene glycol dimethyl ether is measured and stirred and dispersed in the zinc trifluoromethanesulfonate solution. The other steps and parameters are the same as those in embodiment 1.

[0056] Example 3

[0057] The difference between this embodiment and embodiment 1 is that 30 mL of triethylene glycol dimethyl ether is measured and stirred and dispersed in the zinc trifluoromethanesulfonate solution. The other steps and parameters are the same as those in embodiment 1.

[0058] Example 4

[0059] Diethylene glycol dimethyl ether was used as a cosolvent. Other steps and parameters were the same as those in Example 1.

[0060] In summary, the present invention provides a method for preparing a reverse micelle-like aqueous low-temperature electrolyte and an application of an energy storage device, and designs a unique reverse micelle-like aqueous low-temperature electrolyte, which can reduce the apparent salt concentration, reduce the viscosity of the system and improve the wettability, while still maintaining the high concentration characteristics of the electrolyte in the "water core" inside the reverse micelle-like structure, thereby enhancing the electrochemical stability (electrochemical window), while improving the ionic conductivity and low-temperature stability. The present invention selects a suitable ether cosolvent as an organic phase, which has a suitable dielectric constant and donor number, can be miscible with water and has a moderate solubility for electrolyte salts, so the amount of cosolvent can be greater than or much greater than the amount of solvent water, which is conducive to the formation of a reverse micelle-like structure. The present invention uses the amphiphilic anion of the electrolyte salt as a surfactant-like structure to promote the salt-water-cosolvent three-phase to form a unique reverse micelle-like structure with a nanoscale "water core", and the electrolyte salt is used for multiple purposes, which not only avoids the introduction of additional surfactants, but also simplifies the reaction system and saves costs. The reaction conditions of the invention are easy to obtain, the applicable objects are wide, and it is easy to apply on a large scale, which is conducive to the subsequent enlarged production and industrialization, and has broad application prospects.

[0061] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a reverse micelle-like aqueous low-temperature electrolyte, characterized in that: Prepare electrolyte salt solution of a certain concentration, use amphiphilic anions of electrolyte salt as quasi-surfactants; add suitable ether cosolvent as organic phase, the amount of cosolvent can be greater than or much greater than the amount of solvent water; mix the salt-water-cosolvent three phases evenly to form a unique quasi-reverse micelle structure with nano-scale "water core"; the obtained quasi-reverse micelle mixed aqueous low-temperature electrolyte greatly broadens the electrochemical stability window and temperature range of energy storage devices, and can operate stably at extremely low temperatures. .

2. The preparation method according to claim 1, characterized in that: The amphiphilic anions in the electrolyte salt include, but are not limited to, one or more of trifluoromethanesulfonate and trifluoromethanesulfonimide.

3. The preparation method according to claim 1, characterized in that: The metal cations in the electrolyte salt include, but are not limited to, one or more of lithium, sodium, potassium, magnesium, calcium, iron, zinc, tin, lead, aluminum and copper.

4. The preparation method according to claim 1, characterized in that: The concentration of the electrolyte salt solution of a certain concentration is between 3 mol / L and 30.0 mol / L.

5. The preparation method according to claim 1, characterized in that: The ether solvent includes, but is not limited to, one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether.

6. The preparation method according to claim 1, characterized in that: The concentration percentage of the ether co-solvent is between 50% and 99.64%.

7. A reverse micelle-like aqueous low-temperature electrolyte, characterized in that: The aqueous low-temperature electrolyte is prepared by the method described in any one of claims 1 to 6. The aqueous low-temperature electrolyte has excellent electrochemical and low-temperature properties and can effectively improve the low-temperature performance of the energy storage device.

8. The aqueous low-temperature electrolyte according to claim 7, characterized in that This aqueous low-temperature electrolyte can be used in water-based energy storage devices. Due to its unique reverse micelle structure with a nanoscale "water core", it can improve the stability and service life of the equipment in low-temperature environments.

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