Low-temperature aqueous ammonium ion high-entropy electrolyte and application thereof

Abstract

The invention relates to the technical field of electrochemical energy storage, in particular to a low-temperature aqueous ammonium ion high-entropy electrolyte and application thereof. According to the specific technical scheme, the low-temperature water system ammonium ion high-entropy electrolyte comprises ammonium salt, an organic cosolvent and water, and the ammonium salt is one or more of ammonium sulfate, ammonium acetate, ammonium chloride, ammonium tetrafluoroborate, ammonium nitrate and ammonium trifluoromethanesulfonate; the organic cosolvent is any four or more than four of methanol, dimethyl sulfoxide, sulfolane, glycerol, ethylene glycol, 1-methyl-2-pyrrolidone, N, N-dimethylacetamide, acetonitrile, isopropanol, 1, 4-dioxane and ethylene glycol dimethyl ether. By improving the entropy value of the electrolyte system, the low-temperature-resistant performance is obtained, so that the water-based ammonium ion electrochemical device can normally operate at a low temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly relates to a low-temperature aqueous ammonium ion high-entropy electrolyte and its application. Background Art

[0002] New ammonium ion energy storage devices show unique potential in terms of material cost, environmental friendliness, and special application scenarios. They are expected to play a greater role in the fields of renewable energy storage, electric vehicles, portable electronic devices, etc., providing new solutions for green energy and sustainable development.

[0003] Ammonium ion electrolytes have outstanding advantages: First, as charge carriers, the constituent elements of ammonium ions, nitrogen and hydrogen, are abundant on the earth, without relying on scarce metals such as cobalt and nickel. Second, ammonium ion batteries mostly use aqueous electrolytes, which have higher safety compared to flammable organic electrolytes and are not prone to catching fire and exploding under extreme conditions such as puncture and overcharge. Third, in terms of environmental protection, ammonium ion batteries do not contain heavy metals and have low pollution during production and recycling, meeting the requirements of sustainable development. Fourth, the radius of hydrated ammonium ions is relatively small, which is conducive to improving the diffusion rate in the electrolyte. Fifth, ammonium salts have high solubility and can provide higher ionic conductivity. Finally, the molar mass of ammonium ions is relatively light (18 g / mol), which is conducive to constructing devices with high energy density.

[0004] However, in a low-temperature environment, the viscosity of aqueous ammonium ion solutions increases sharply, and the ionic conductivity decreases, resulting in the attenuation or loss of the energy storage capacity of the device. Therefore, developing low-temperature-resistant ammonium ion electrolytes can broaden the operating temperature range of aqueous ammonium ion electrochemical devices. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a low-temperature aqueous ammonium ion high-entropy electrolyte and its application. By increasing the entropy value of the electrolyte system, the low-temperature-resistant performance is obtained, enabling the normal operation of aqueous ammonium ion electrochemical devices at low temperatures.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0007] The present invention discloses a low-temperature aqueous ammonium ion high-entropy electrolyte, which includes ammonium salts, organic co-solvents, and water. The ammonium salts are one or more of ammonium sulfate, ammonium acetate, ammonium chloride, ammonium tetrafluoroborate, ammonium nitrate, and ammonium trifluoromethanesulfonate. The organic co-solvents are any four or more of methanol, dimethyl sulfoxide, sulfolane, glycerol, ethylene glycol, 1-methyl-2-pyrrolidone, N,N-dimethylacetamide, acetonitrile, isopropanol, 1,4-dioxane, and ethylene glycol dimethyl ether.

[0008] Preferably, when there is one kind of ammonium salt, its concentration is 0.5 mol / L - 3.5 mol / L; when there are multiple kinds of ammonium salts, they are added in equimolar amounts, and the total concentration is 0.5 mol / L - 3.5 mol / L.

[0009] Preferably, the dosage of the organic co-solvent accounts for 35% - 85% of the total volume of the organic co-solvent and water.

[0010] Correspondingly, an electrochemical device includes a low-temperature aqueous ammonium-ion high-entropy electrolyte.

[0011] Preferably, the lowest temperature at which the low-temperature aqueous ammonium-ion high-entropy electrolyte is applied is -50 °C.

[0012] The present invention has the following beneficial effects:

[0013] The high-entropy electrolyte prepared by the present invention not only reduces the liquid-solid transition temperature of the electrolyte, enabling good low-temperature performance; but also due to the presence of water, it has a good flame retardant effect; at the same time, the electrolyte produced by the capacitor with ammonium ions as charge carriers has a weak acidity, which can effectively prevent electrode corrosion and reduce hydrogen evolution; and ammonium ions have a tetrahedral structure, showing more complex topochemical properties in electrode materials compared with spherical metal ions without specific orientation. During the charge and discharge process, ammonium ions transfer charges with the electrode through the formation and breakage of hydrogen bonds, which not only achieves a higher energy storage capacity than metal ions, but also shows greater advantages in terms of energy density.

[0014] The electrolyte prepared by the present invention can be applied to electrochemical devices such as secondary batteries and supercapacitors, and is particularly suitable for high-safety, low-cost, and low-temperature energy storage scenarios. Description of the Drawings

[0015] Figure 1 The aqueous ammonium-ion high-entropy electrolyte prepared in Example 1 remains liquid at -50 °C;

[0016] Figure 2 The cyclic voltammogram of the supercapacitor using the aqueous ammonium-ion high-entropy electrolyte prepared in Example 1;

[0017] Figure 3 The aqueous ammonium-ion high-entropy electrolyte prepared in Example 2 remains liquid at -50 °C;

[0018] Figure 4 The cyclic voltammogram of the supercapacitor using the aqueous ammonium-ion high-entropy electrolyte prepared in Example 2;

[0019] Figure 5 The aqueous ammonium-ion high-entropy electrolyte prepared in Example 3 remains liquid at -50 °C;

[0020] Figure 6 Cyclic voltammetry curve of the aqueous ammonium ion high-entropy electrolyte supercapacitor prepared in Example 3;

[0021] Figure 7 The aqueous ammonium ion high-entropy electrolyte prepared in Example 4 remains liquid at -50 °C;

[0022] Figure 8 Cyclic voltammetry curve of the aqueous ammonium ion supercapacitor with the high-entropy electrolyte prepared in Example 4. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0024] Unless otherwise specified, the technical means used in the implementation examples are conventional means well-known to those skilled in the art.

[0025] The present invention discloses a low-temperature aqueous ammonium ion high-entropy electrolyte, which includes ammonium salts, organic co-solvents and water. The ammonium salts are one or more of ammonium sulfate, ammonium acetate, ammonium chloride, ammonium tetrafluoroborate, ammonium nitrate and ammonium trifluoromethanesulfonate. The organic co-solvents are any four or more of methanol, dimethyl sulfoxide, sulfolane, glycerol, ethylene glycol, 1-methyl-2-pyrrolidone, N,N-dimethylacetamide, acetonitrile, isopropanol, 1,4-dioxane and ethylene glycol dimethyl ether.

[0026] Further, when there is one kind of ammonium salt, its concentration is 0.5 mol / L - 3.5 mol / L. When there are multiple kinds of ammonium salts, the multiple ammonium salts are added in equimolar amounts, and the total concentration is 0.5 mol / L - 3.5 mol / L. If the concentration is too low, the ionic conductivity of the system is not high, resulting in poor device performance; if the concentration is too high, it cannot be completely dissolved, and solids will precipitate in the system, which will also affect the device performance.

[0027] The dosage of the organic co-solvent accounts for 35% - 85% of the total volume of the solvent (organic co-solvent + water). If the volume ratio of the organic co-solvent is too high, the solubility of the ammonium salt is low and solids will precipitate; if the volume ratio of the organic co-solvent is too low, the system cannot achieve low-temperature performance.

[0028] The low-temperature aqueous ammonium ion high-entropy electrolyte disclosed by the present invention is prepared by adding ammonium salts and organic co-solvents to water. Among them, at least one ammonium salt is used, and at least four organic co-solvents are used. If the types of organic co-solvents are less than four, the entropy value of the electrolyte system is insufficient, and the degree of disorder cannot meet the requirements of a high-entropy solution.

[0029] The present invention discloses an electrochemical device, including the above-mentioned low-temperature aqueous ammonium ion high-entropy electrolyte. The electrochemical device can be a secondary battery or a supercapacitor. Among them, the supercapacitor is an activated carbon-activated carbon supercapacitor.

[0030] The present invention will be further elaborated below in conjunction with specific embodiments.

[0031] Example 1

[0032] An appropriate amount of ammonium acetate was mixed evenly with 2 mL of water, and 2 mL of each of the organic co-solvents: acetonitrile, ethylene glycol, 1,4-dioxane, and ethylene glycol dimethyl ether were added in sequence to prepare an ammonium ion high-entropy electrolyte with an ammonium acetate concentration of 1 mol / L (abbreviation: high-entropy electrolyte). The volume of the organic co-solvent accounted for 80% of the total solvent volume.

[0033] The high-entropy electrolyte prepared in this Example 1 could still maintain a liquid state at -50 °C (as Figure 1 shown). This high-entropy electrolyte was used in an aqueous ammonium ion supercapacitor (structural composition: composed of an activated carbon negative electrode, an activated carbon positive electrode, a separator, and a high-entropy electrolyte), which could enable it to operate under a voltage window of 1.6 V (as Figure 2 shown).

[0034] Example 2

[0035] An appropriate amount of ammonium acetate was mixed evenly with 4 mL of water, and 3 mL of each of the organic co-solvents: acetonitrile, tetrahydrofuran, 1,4-dioxane, and ethylene glycol dimethyl ether, and 4 mL of ethylene glycol were added in sequence to prepare an ammonium ion high-entropy electrolyte with an ammonium acetate concentration of 1 mol / L (abbreviation: high-entropy electrolyte). The volume of the organic co-solvent accounted for 80% of the total solvent volume.

[0036] The high-entropy electrolyte prepared in this Example 2 could also maintain a liquid state at -50 °C (as Figure 3 shown). This high-entropy electrolyte was used in an aqueous ammonium ion supercapacitor (the structural composition was the same as that in Example 1), which could enable it to operate under a voltage window of 1.6 V (as Figure 4 shown).

[0037] Example 3

[0038] Mix an appropriate amount of ammonium acetate with 8 mL of water evenly, and successively add 3 mL each of organic co-solvents: acetonitrile, isopropanol, 1,4-dioxane, and ethylene glycol dimethyl ether to prepare an ammonium ion high-entropy electrolyte with an ammonium acetate concentration of 2 mol / L (abbreviation: high-entropy electrolyte). The volume of the organic co-solvent accounts for 60% of the total solvent volume.

[0039] The high-entropy electrolyte prepared in Example 3 can maintain a liquid state at -50 °C (as Figure 5 shown). When this high-entropy electrolyte is used in an aqueous ammonium ion supercapacitor (with the same structural composition as in Example 1), it can operate within a 1.6 V voltage window (as Figure 6 shown).

[0040] Example 4

[0041] Mix an appropriate amount of ammonium acetate with 8 mL of water evenly, and successively add 3 mL each of organic co-solvents: acetonitrile, isopropanol, ethylene glycol dimethyl ether, and tetrahydrofuran to prepare an ammonium ion high-entropy electrolyte with an ammonium acetate concentration of 1 mol / L (abbreviation: high-entropy electrolyte). The volume of the organic co-solvent accounts for 60% of the total solvent volume.

[0042] The high-entropy electrolyte prepared in Example 4 can maintain a liquid state at -50 °C (as Figure 7 shown). When this high-entropy electrolyte is used in an aqueous ammonium ion supercapacitor (with the same structural composition as in Example 1), it can operate within a 1.6 V voltage window (as Figure 8 shown).

[0043] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A low-temperature aqueous ammonium ion high entropy electrolyte, characterized in that: The invention comprises an ammonium salt, an organic co-solvent and water, wherein the ammonium salt is one or more of ammonium sulfate, ammonium acetate, ammonium chloride, ammonium tetrafluoroborate, ammonium nitrate and ammonium trifluoromethanesulfonate, and the organic co-solvent is any four or more of methanol, dimethyl sulfoxide, cyclopentane, glycerol, ethylene glycol, 1-methyl-2-pyrrolidone, N,N-dimethylacetamide, acetonitrile, isopropanol, 1,4-dioxane and ethylene glycol dimethyl ether.

2. A low-temperature aqueous ammonium ion high entropy electrolyte according to claim 1, characterized in that: When there is one type of ammonium salt, its concentration is 0.5 mol / L-3.5 mol / L. When there are multiple types of ammonium salts, the multiple types of ammonium salts are added in equal moles, and the total concentration is 0.5 mol / L-3.5 mol / L.

3. The low-temperature aqueous ammonium ion high entropy electrolyte according to claim 1, characterized in that: The amount of the organic co-solvent used accounts for 35%-85% of the total volume of the organic co-solvent and water.

4. An electrochemical device, characterized in that: It comprises the low-temperature aqueous ammonium ion high entropy electrolyte as described in any one of claims 1 to 3.

5. The use according to claim 4, characterized in that: The lowest application temperature of the low-temperature aqueous ammonium ion high entropy electrolyte is -50°C.

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