Low-temperature aqueous electrolyte and preparation method and application thereof

Abstract

The invention discloses a low-temperature aqueous electrolyte and a preparation method and application thereof, and belongs to the technical field of aqueous electrolytes. The low-temperature aqueous electrolyte provided by the invention comprises a metal salt, an additive, water and a cosolvent, the metal salt is selected from one or more of lithium chloride, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, bis (trifluoromethanesulfonyl) lithium imide, sodium chloride, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium nitrate, potassium chloride, potassium nitrate, magnesium chloride, magnesium perchlorate, zinc perchlorate and zinc chloride; the additive is calcium chloride; the cosolvent is ethylene glycol. According to the aqueous electrolyte provided by the invention, the ethylene glycol with relatively low toxicity is used as a cosolvent, so that the aqueous electrolyte has excellent low-temperature performance while reducing the concentration of the lithium salt in the aqueous electrolyte, and has the advantages of being green, environment-friendly, relatively low in price, safe and flame-retardant.

Description

Technical Field

[0001] The present application belongs to the technical field of aqueous electrolytes, and in particular, relates to a low-temperature aqueous electrolyte and a preparation method and application thereof. Background Art

[0002] Aqueous batteries and capacitors have been favored by researchers due to their low cost, intrinsic safety, and environmental friendliness. However, since water freezes at temperatures below zero, the performance of aqueous batteries and devices degrades severely at low temperatures. Therefore, broadening the electrochemical stability window of aqueous electrolytes and lowering the freezing point of aqueous electrolytes are the key to developing aqueous batteries and capacitors with low-temperature high performance.

[0003] At present, the design and preparation of various low-temperature aqueous electrolytes have been reported in the literature. For example, Wu Zhongshuai (National Science Review, DOI: 10.1093 / nsr / nwac024) developed a low-temperature resistant, safe and environmentally friendly aqueous electrolyte (20m LiCl). The MXene-based supercapacitor constructed with this electrolyte can work stably for a long time at -40°C. However, due to the excessive amount of lithium salt used, the cost is relatively high. In order to overcome the disadvantages of high-concentration salt, researchers began to try to add some additives to reduce the salt concentration while improving the low-temperature performance. For example, the aqueous electrolyte (composed of water, zinc sulfate and ethylene glycol) designed by Li Xianfeng et al. (Energy & Environmental Science, DOI: 10.1039 / d0ee01538e) uses this electrolyte to construct aqueous zinc ion capacitors and zinc ion batteries that show excellent electrochemical performance at -20°C. However, the current research in this area is still limited, and there is still a lot of room for development. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a low-temperature aqueous electrolyte and a preparation method and application thereof. The low-temperature aqueous electrolyte is low in cost and has a wide voltage window. It uses less toxic ethylene glycol as a co-solvent and uses a relatively small concentration of lithium salt, which is more green and environmentally friendly.

[0005] In order to achieve the above-mentioned invention object, this application provides the following technical solutions:

[0006] In one aspect, the present application provides a low-temperature aqueous electrolyte, the low-temperature aqueous electrolyte comprising a metal salt, an additive, water and a co-solvent;

[0007] The metal salt is selected from one or more of lithium chloride, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, sodium chloride, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium nitrate, potassium chloride, potassium nitrate, magnesium chloride, magnesium perchlorate, zinc perchlorate and zinc chloride;

[0008] The additive is calcium chloride;

[0009] The co-solvent is ethylene glycol.

[0010] Optionally, the low-temperature aqueous electrolyte consists of a metal salt, an additive, water and a co-solvent.

[0011] Optionally, the molar ratio of the metal salt to the additive is 1:0.125-8, wherein the molar amount of the metal salt is calculated based on the molar amount of the substance itself, and the molar amount of the additive is calculated based on the molar amount of the substance itself.

[0012] Optionally, the molar ratio of the metal salt to the additive is independently selected from any value of 8:1, 6:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:6, 1:8, or any range between two values.

[0013] Optionally, the molar ratio of the metal salt to the additive is 1:2-6, wherein the molar amount of the metal salt is calculated based on the molar amount of the substance itself, and the molar amount of the additive is calculated based on the molar amount of the substance itself.

[0014] Optionally, the molar ratio of the metal salt to the additive is independently selected from any value of 1:2, 1:3, 1:4, 1:5, 1:6 or any range between two values.

[0015] Optionally, the volume ratio of water to co-solvent is 0.1 to 9:1.

[0016] Optionally, the volume ratio of water to co-solvent is independently selected from any value of 9:1, 6:1, 4:1, 1:1, 1:3, 1:9 or any range therebetween.

[0017] Optionally, the volume ratio of water to co-solvent is 1 to 9:1.

[0018] Preferably, the volume ratio of water to co-solvent is 2 to 7:1.

[0019] Optionally, the final concentration of the metal ions in the metal salt in the low-temperature aqueous electrolyte is 1 to 5 mol / kg.

[0020] Optionally, the final concentration of the metal ions in the metal salt in the low-temperature aqueous electrolyte is independently selected from any value of 1 mol / kg, 2 mol / kg, 3 mol / kg, 4 mol / kg, 5 mol / kg or a range between any two values.

[0021] Optionally, the electrochemical window of the aqueous electrolyte is 2.5 to 4.5V.

[0022] Optionally, the electrochemical window of the aqueous electrolyte is independently selected from any value among 2.5V, 3V, 3.5V, 4V, 4.5V, or a range of values ​​between any two of them.

[0023] In a second aspect, the present application provides a method for preparing the above-mentioned low-temperature aqueous electrolyte, comprising the following steps:

[0024] The metal salt, additive, water and co-solvent are mixed to obtain the low-temperature aqueous electrolyte.

[0025] In a third aspect, the present application provides the use of the above-mentioned low-temperature aqueous electrolyte in the preparation of an aqueous high-voltage energy storage device.

[0026] Optionally, the water-based high-voltage energy storage device includes a water-based high-voltage battery and / or a water-based high-voltage capacitor.

[0027] Compared with the prior art, this application has the following beneficial effects:

[0028] (1) The aqueous electrolyte provided in the present application uses ethylene glycol with low toxicity as a co-solvent and reduces the concentration of lithium salt in the aqueous electrolyte, which has the advantages of being green, environmentally friendly, relatively low in price, and safe and flame retardant.

[0029] (2) The method for preparing the aqueous electrolyte provided in this application produces a product with high quality, good performance and a wide range of applications.

[0030] (3) Compared with traditional aqueous electrolytes, the aqueous electrolyte provided in this application significantly broadens the electrochemical stability window and has excellent low-temperature performance, and has the characteristics of low cost and green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The electrolytes prepared in Comparative Examples 1 to 3 and Example 2 of the present application were subjected to linear sweep voltammetry (LSV) tests using a glassy carbon electrode as the working electrode;

[0032] Figure 2 Linear sweep voltammetry (LSV) test was performed on the electrolyte prepared in Comparative Example 1 and Examples 1 to 3 of the present application using a glassy carbon electrode as the working electrode;

[0033] Figure 3Cyclic voltammetry test (different cut-off voltages) of the electrolyte prepared in Example 2 of the present application in an AC / electrolyte / AC capacitor;

[0034] Figure 4 Cyclic voltammetry test (different scan rates) of the electrolyte prepared in Example 2 of the present application in an AC / electrolyte / AC capacitor;

[0035] Figure 5 The electrolyte prepared in Example 2 of the present application, the constant current charge and discharge (GCD) curves at the same current density at different temperatures are tested in an AC / electrolyte / AC capacitor, and the surface capacitance of the capacitor at different temperatures is calculated by the formula;

[0036] Figure 6 The electrolyte prepared in Example 2 of the present application was subjected to a long cycle test (-40°C) in an AC / electrolyte / AC capacitor. DETAILED DESCRIPTION

[0037] The present application is further described below in conjunction with specific embodiments. The following are only a few embodiments of the present application, and are not intended to limit the present application in any form. Although the present application discloses the following preferred embodiments, they are not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the above disclosed technical content to make some changes or modifications are equivalent to equivalent implementation cases and are within the scope of the technical solution.

[0038] Unless otherwise specified, the raw materials in the examples of the present application were purchased from commercial sources and used directly without any special treatment.

[0039] Unless otherwise specified, the analysis methods in the examples all adopt conventional settings and conventional analysis methods of instruments or equipment.

[0040] The following examples and comparative examples were analyzed by cyclic voltammetry and constant current charge and discharge using a Chenhua 760E electrochemical workstation.

[0041] Example 1

[0042] Add 0.038 mol of anhydrous calcium chloride and 0.01 mol of lithium chloride into a sample bottle containing 10 mL of a mixed solution of ethylene glycol and water (volume ratio of 1:9), stir evenly, and obtain an electrolyte.

[0043] Example 2

[0044] Add 0.038 mol of anhydrous calcium chloride and 0.01 mol of lithium chloride into a sample bottle containing 10 mL of a mixed solution of ethylene glycol and water (volume ratio of 3:7), stir evenly, and obtain an electrolyte.

[0045] Example 3

[0046] Add 0.038 mol of anhydrous calcium chloride and 0.01 mol of lithium chloride into a sample bottle containing 10 mL of a mixed solution of ethylene glycol and water (volume ratio of 1:1), stir evenly, and obtain an electrolyte.

[0047] Example 4

[0048] Add 0.038 mol of anhydrous calcium chloride and 0.01 mol of lithium nitrate into a sample bottle containing 10 mL of a mixed solution of ethylene glycol and water (volume ratio of 3:7), stir evenly, and obtain an electrolyte.

[0049] Example 5

[0050] Add 0.038 mol of anhydrous calcium chloride and 0.01 mol of zinc chloride into a sample bottle containing 10 mL of a mixed solution of ethylene glycol and water (volume ratio of 1:1), stir evenly, and obtain an electrolyte.

[0051] Comparative Example 1

[0052] Add 0.038 mol of anhydrous calcium chloride and 0.01 mol of lithium chloride into a sample bottle containing 10 mL of water, stir evenly, and obtain an electrolyte.

[0053] Comparative Example 2

[0054] Add 0.01 mol lithium chloride into a sample bottle containing 10 mL of water and stir evenly to obtain an electrolyte.

[0055] Comparative Example 3

[0056] Add 0.01 mol of lithium chloride into a sample bottle containing 10 mL of a mixed solution of ethylene glycol and water (volume ratio of 3:7), stir evenly, and obtain an electrolyte.

[0057] Experimental Example 1

[0058] Electrochemical tests were performed on the electrolytes prepared in Comparative Examples 1 to 3 and Examples 1 to 5, using cyclic voltammetry, constant current charge and discharge, and electrochemical window tests.

[0059] Typical test results are as follows: Figure 1 As shown, the electrolytes prepared in corresponding Examples 1 to 3 and Example 2. Figure 1 It can be seen that the addition of calcium chloride and ethylene glycol significantly broadens the electrochemical window.

[0060] Typical test results are as follows: Figure 2 As shown, the electrolytes prepared in Example 1 and Examples 1 to 3 are corresponding. Figure 2 It can be seen that the voltage window of CaCl2-EG3 aqueous electrolyte is 3.5V.

[0061] Typical test results are as follows: Figure 3 As shown, the electrolyte prepared in Example 2 corresponds to the electrolyte prepared in Example 2. Figure 3 It can be seen that the assembled capacitor has no obvious polarization phenomenon when operating at 0-1.6V.

[0062] Typical test results are as follows: Figure 4 As shown, the electrolyte prepared in accordance with Embodiment 2. Figure 4 It can be seen that the assembled capacitors exhibit ideal double-layer effect at 0-1.6V and a scan rate of 2-20mV / s.

[0063] Typical test results are as follows: Figure 5 and 6 As shown, the electrolyte prepared in Example 2 was subjected to charge and discharge tests at different temperatures in an AC / electrolyte / AC capacitor and a long cycle test at -40°C. Figure 5 and Figure 6 It can be seen that the electrolyte of the present application has a higher capacity retention rate at low temperature than at room temperature and can operate normally and stably for a long time at low temperature.

[0064] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A low-temperature aqueous electrolyte, characterized in that: The low-temperature aqueous electrolyte comprises a metal salt, an additive, water and a co-solvent; The metal salt is selected from one or more of lithium chloride, lithium nitrate, lithium perchlorate, lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, sodium chloride, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium nitrate, potassium chloride, potassium nitrate, magnesium chloride, magnesium perchlorate, zinc perchlorate and zinc chloride; The additive is calcium chloride; The co-solvent is ethylene glycol.

2. A low-temperature aqueous electrolyte according to claim 1, characterized in that: The molar ratio of the metal salt to the additive is 1:0.125-8, wherein the molar amount of the metal salt is calculated based on the molar amount of the substance itself, and the molar amount of the additive is calculated based on the molar amount of the substance itself.

3. A low-temperature aqueous electrolyte according to claim 1, characterized in that: The molar ratio of the metal salt to the additive is 1:2-6, wherein the molar amount of the metal salt is calculated based on the molar amount of the substance itself, and the molar amount of the additive is calculated based on the molar amount of the substance itself.

4. A low-temperature aqueous electrolyte according to claim 1, characterized in that: The volume ratio of water to co-solvent is 0.1 to 9:

1.

5. A low-temperature aqueous electrolyte according to claim 1, characterized in that: The volume ratio of water to co-solvent is 1 to 9:

1.

6. A low-temperature aqueous electrolyte according to claim 1, characterized in that: The final concentration of the metal ions in the metal salt in the low-temperature aqueous electrolyte is 1 to 5 mol / kg.

7. A low-temperature aqueous electrolyte according to claim 1, characterized in that: The electrochemical window of the aqueous electrolyte is 2.5-4.5V.

8. A method for preparing a low-temperature aqueous electrolyte according to any one of claims 1 to 7, characterized in that: The steps include: The metal salt, additive, water and co-solvent are mixed to obtain the low-temperature aqueous electrolyte.

9. Use of a low-temperature aqueous electrolyte as claimed in any one of claims 1 to 7 in the preparation of an aqueous high-voltage energy storage device.

10. The use according to claim 9, characterized in that: The water-based high-voltage energy storage device includes a water-based high-voltage battery and / or a water-based high-voltage capacitor.

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