Low-temperature electrolyte, preparation method and application thereof

Abstract

The application discloses a low-temperature electrolyte and a preparation method and application thereof. The electrolyte is added with perfluoropolyether and 1,3-propane sultone, can inhibit solvent crystallization in the electrolyte, can accelerate interface film formation, and can double guarantee liquid stability. Meanwhile, the composition of main solvents, auxiliary solvents and electrolytes in the electrolyte and the proportion of each component are optimized, so that the electrolyte can realize low viscosity, high conductivity and low self-discharge under extreme low temperature, and can be used for supercapacitors under ultra-low temperature environment.

Description

Technical Field

[0001] This invention belongs to the field of electrolytes, specifically relating to a low-temperature electrolyte, its preparation method, and its application. Background Technology

[0002] Electrolytes are the dielectric materials used in chemical batteries, electrolytic capacitors, and other similar devices. In supercapacitors, the performance of the electrolyte is crucial; however, current supercapacitor electrolytes suffer from numerous limitations that restrict their application in low-temperature environments.

[0003] Existing supercapacitor electrolytes, such as the TEABF4 / acetonitrile system, are prone to solidification at low temperatures (below -40°C). When the electrolyte solidifies, its ionic conductivity drops sharply, typically below 5 mS / cm. This phenomenon directly leads to a significant decrease in the capacitance of the supercapacitor, with a reduction exceeding 50%.

[0004] Conventional cryogenic electrolytes, represented by PC-based systems, have relatively low freezing points but suffer from viscosity issues. At -55°C, their viscosity exceeds 50 mPa•s. This excessively high viscosity severely restricts ion migration, thus affecting the charge and discharge performance of supercapacitors.

[0005] Furthermore, existing additives (such as vinylene carbonate) have limited effectiveness in improving the low-temperature performance of supercapacitors. Not only do they contribute little to improving low-temperature performance, but they may also trigger side reactions during use, further affecting the performance and stability of supercapacitors.

[0006] In summary, existing supercapacitor electrolytes have significant shortcomings in low-temperature performance, mainly in the following two aspects: First, at a low temperature of -55℃, the product capacity decays severely, exceeding 50%, which cannot meet the stringent performance requirements of capacitors in cutting-edge fields such as aerospace; Second, at -55℃, the internal resistance of supercapacitors increases significantly, exceeding 10 times the internal resistance at room temperature, which is also unsuitable for cutting-edge fields such as aerospace. These problems urgently need to be solved by developing new electrolytes. Summary of the Invention

[0007] The purpose of this invention is to provide a low-temperature electrolyte, its preparation method, and its application, so as to solve at least one aspect of the problems and defects mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] The first aspect of the present invention provides a low-temperature electrolyte, wherein perfluoropolyether and 1,3-propane sulfonyl lactone are added to the low-temperature electrolyte.

[0010] Adding perfluoropolyether (PFPE) and 1,3-propane sulfonyl lactone to the electrolyte can inhibit solvent crystallization and prevent low-temperature solidification by inhibiting the orderly arrangement of solvent molecules through steric hindrance. The hydrophobicity of PFPE can reduce the hydrogen bonding between solvent molecules and help inhibit the increase in viscosity. 1,3-propane sulfonyl lactone (PS) can form a sulfur-containing passivation layer on the surface of the carbon electrode, reduce self-discharge, stabilize the electrode / electrolyte interface, and its sulfonic acid groups can also promote salt dissociation and help improve ionic conductivity.

[0011] As a further embodiment of the present invention: the perfluoropolyether has a molecular weight of 1000~10000, is formed by photo-oxidative polymerization of hexafluoropropylene (HFP), and has the structural formula CF3O(C3F6O). (CF2O) CF3. This perfluoropolyether possesses excellent heat resistance, oxidation resistance, radiation resistance, chemical inertness, and lubrication properties. Furthermore, the liquid temperature range of perfluoropolyether is extremely wide, typically from -80°C to 300°C. The viscosity of perfluoropolyether changes slowly at low temperatures; the "shielding layer" formed by fluorine atoms protects the molecular chains, preventing solidification or embrittlement at low temperatures, and it maintains chemical inertness even at extreme low temperatures of -80°C.

[0012] As a further embodiment of the present invention, the amount of perfluoropolyether added is 0.5-1% by mass percentage, preferably 0.5-0.8%.

[0013] As a further embodiment of the present invention, the amount of 1,3-propanesulfonyl lactone added is 0.5-1% by mass percentage, preferably 0.5-0.8%.

[0014] As a further embodiment of the present invention, the electrolyte further includes a main solvent, an auxiliary solvent, and an electrolyte salt.

[0015] As a further embodiment of the present invention, the main solvent has a mass percentage content of 80-95%, preferably 80-88%.

[0016] As a further embodiment of the present invention: the freezing point of the main solvent is -75℃ to -60℃, preferably -70℃ to -65℃.

[0017] As a further embodiment of the present invention, the auxiliary solvent has a mass percentage content of 5-10%, preferably 5-7%.

[0018] As a further embodiment of the present invention, the mass percentage of the electrolyte salt is 5-15%, preferably 5-10%.

[0019] As a further embodiment of the present invention: the low temperature refers to a temperature of -80℃ to -40℃, preferably -60℃ to -40℃.

[0020] As a further embodiment of the present invention, the main solvent includes at least one of ester solvents and low viscosity solvents.

[0021] As a further embodiment of the present invention, the ester solvent includes at least one of fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate.

[0022] As a further embodiment of the present invention: the ester solvent is fluoroethylene carbonate.

[0023] As a further embodiment of the present invention: the ester solvent is ethylene carbonate.

[0024] As a further embodiment of the present invention, the ester solvent is propylene carbonate.

[0025] As a further embodiment of the present invention, the low viscosity solvent includes at least one of acetonitrile, 1,2-dimethoxyethane, and adiponitrile.

[0026] As a further embodiment of the present invention, the low-viscosity solvent is acetonitrile.

[0027] As a further embodiment of the present invention, the low-viscosity solvent is 1,2-dimethoxyethane.

[0028] As a further embodiment of the present invention: the main solvent is composed of an ester solvent and a low-viscosity solvent, wherein the volume ratio of the ester solvent to the low-viscosity solvent is 1:(0.2~3), preferably 1:1.

[0029] As a further embodiment of the present invention, the main solvent is composed of fluoroethylene carbonate and acetonitrile.

[0030] In this scheme, the intermolecular forces between fluoroethylene carbonate and acetonitrile disrupt the solvent's crystallization tendency, resulting in an extremely low freezing point for the main solvent. Fluoroethylene carbonate possesses high dielectric properties, effectively enhancing salt dissociation, while acetonitrile's low viscosity ensures ion mobility. Together, they reduce concentration polarization, allowing the electrolyte to maintain high conductivity even at extremely low temperatures. The fluorinated groups of fluoroethylene carbonate and the polarity of acetonitrile synergistically reduce the electrode contact angle and interfacial impedance. The main solvent forms a uniform wetting layer on the electrode surface. The reducing fluorinated products of fluoroethylene carbonate and the cyano groups of acetonitrile synergistically construct a dense SEI film, suppressing side reactions, reducing electrolyte loss, and improving low-temperature rate performance.

[0031] As a further embodiment of the present invention, the auxiliary solvent includes at least one of γ-butyrolactone, ethyl propionate, methyl butyrate, and butyl acetate.

[0032] As a further embodiment of the present invention: the auxiliary solvent is γ-butyrolactone.

[0033] γ-Butyrolactone was selected as an auxiliary solvent. The ester groups in γ-butyrolactone form hydrogen bonds with the hydroxyl or carboxyl groups on the electrode surface, enhancing electrode surface wettability, significantly reducing the interfacial contact angle, decreasing charge transfer impedance, and forming a uniform adsorption layer on the electrode surface, thus improving ion transport channels. γ-Butyrolactone has a high boiling point and a low freezing point, allowing it to remain liquid at extremely low temperatures, thus helping to improve the low-temperature rate performance of the electrolyte. The dielectric constant of γ-butyrolactone is between that of fluoroethylene carbonate and acetonitrile, which can balance the polarity gradient of the solvent system, promote the dissociation of electrolyte salts, regulate viscosity, and inhibit salt precipitation. Simultaneously, during cycling, it is partially oxidized to form γ-butyrolactone derivatives (such as carboxylates), which synergistically form a sulfur-oxygen composite passivation layer with 1,3-propanesulfonyl lactone, inhibiting electrode oxidation and self-discharge.

[0034] As a further embodiment of the present invention, the auxiliary solvent is ethyl propionate.

[0035] As a further embodiment of the present invention, the electrolyte salt includes at least one of lithium salt and organic boron salt.

[0036] As a further embodiment of the present invention, the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium perfluorobutyl sulfonate, and lithium bis(trifluoromethanesulfonyl)imide.

[0037] As a further embodiment of the present invention, the lithium salt is lithium bis(fluorosulfonyl)imide, which has the characteristics of high ionic conductivity, electrode compatibility and thermodynamic stability.

[0038] As a further embodiment of the present invention, the lithium salt is lithium hexafluorophosphate.

[0039] As a further embodiment of the present invention: the organoboron salt includes at least one of methyltriethylammonium tetrafluoroborate and tetraethylammonium tetrafluoroborate.

[0040] As a further embodiment of the present invention: the organoboron salt is tetraethylammonium tetrafluoroborate.

[0041] As a further embodiment of the present invention: the electrolyte salt is composed of lithium salt and organic boron salt, wherein the molar ratio of lithium salt to organic boron salt is 1:(1~3), preferably 1:2.

[0042] Using a composite salt composed of lithium salt and organic boron salt in a specific ratio as the electrolyte salt not only provides high delocalized charge and accelerates charge transport, but also inhibits corrosion of aluminum current collectors. The synergistic effect of the two salts reduces concentration polarization, improves low-temperature rate performance, and, together with other components, enables the electrolyte to maintain excellent ionic conductivity and cycling performance under extremely low temperature conditions.

[0043] As a further embodiment of the present invention: the electrolyte salt is composed of a composite salt of lithium difluorosulfonylimide and methyltriethylammonium tetrafluoroborate.

[0044] In this scheme, lithium bis(fluorosulfonyl)imide can improve ion transport efficiency, methyltriethylammonium tetrafluoroborate can balance charge distribution, and the passivation effect of methyltriethylammonium tetrafluoroborate can effectively protect the aluminum current collector. The synergy of the two makes the electrolyte have excellent ionic conductivity and cycle retention rate under extremely low temperature conditions.

[0045] As a further embodiment of the present invention, the electrolyte comprises the following components in weight percentage: 85-87% main solvent, 5-7% auxiliary solvent, 7-9% electrolyte salt, 0.5-0.8% perfluoropolyether, and 0.5-0.8% 1,3-propanesulfonyl lactone;

[0046] The main solvent includes one of the following: a mixture of fluoroethylene carbonate and acetonitrile in a volume ratio of 1:1; a mixture of ethylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1:3; or a mixture of propylene carbonate and acetonitrile in a volume ratio of 3:1.

[0047] The auxiliary solvent includes one of γ-butyrolactone and butyl acetate;

[0048] The electrolyte salt includes one of the following: a mixture of lithium bis(fluorosulfonyl)imide and tetraethylammonium tetrafluoroborate in a molar ratio of 1:2; a mixture of lithium hexafluorophosphate and tetraethylammonium tetrafluoroborate in a molar ratio of 1:3; or a mixture of lithium bis(fluorosulfonyl)imide and tetraethylammonium tetrafluoroborate in a molar ratio of 1:1.

[0049] A second aspect of the present invention provides a method for preparing the low-temperature electrolyte as described above, comprising the following steps: adding the auxiliary solvent to the main solvent and stirring until uniform; adding the electrolyte salt to dissolve; adding perfluoropolyether and 1,3-propane sulfonyl lactone; dispersing and filtering to obtain the low-temperature electrolyte.

[0050] As a further embodiment of the present invention, the stirring time is 20-30 minutes.

[0051] As a further embodiment of the present invention: the dispersion is performed using ultrasonic dispersion, and the dispersion time is 1~1.5h.

[0052] As a further embodiment of the present invention: the filtration uses a filter membrane with a pore diameter of less than 0.25 μm, and more preferably a filter membrane with a pore diameter of 0.22 μm.

[0053] A third aspect of the present invention provides the application of the low-temperature electrolyte as described above or the low-temperature electrolyte prepared by the method described above in a supercapacitor.

[0054] As a further aspect of the present invention, the supercapacitor can be used in ultra-low temperature environments.

[0055] The technical solution of the present invention has at least the following technical effects:

[0056] (1) Using perfluoropolyether and 1,3-propane sulpholactone as additives in the electrolyte can both inhibit solvent crystallization in the electrolyte and accelerate interfacial film formation, thus providing dual protection for liquid stability. By optimizing the component ratio, the passivation layer of 1,3-propane sulpholactone and the interfacial modification of perfluoropolyether can work together to reduce impedance, so that the electrolyte can achieve low viscosity, high conductivity and low self-discharge at extreme low temperatures.

[0057] (2) By optimizing the chemical composition of the electrolyte, the interaction between the main solvent, auxiliary solvent, electrolyte salt and additives can be fully utilized to improve the ionic conductivity of the electrolyte under ultra-low temperature conditions and ensure the capacitance retention rate of the capacitor. The electrolyte provided by the present invention has excellent ionic conductivity under ultra-low temperature conditions, and the capacitor can maintain an average capacitance retention rate of more than 95% after 3 cycles. Detailed Implementation

[0058] 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 only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0059] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0060] Specific conditions not specified in the examples were performed under conventional conditions; reagents or instruments not specified by manufacturers were all commercially available products.

[0061] The perfluoropolyether used in the examples has CAS number 69991-67-9 and an average molecular weight of 1800.

[0062] Example 1

[0063] An electrolyte comprises the following components in weight percentages: 0.8% perfluoropolyether, 0.5% 1,3-propane sulpholol, 86.7% main solvent, 5% auxiliary solvent, and 7% electrolyte salt;

[0064] The main solvent consists of a mixture of an ester solvent and a low-viscosity solvent in a volume ratio of 1:1. The ester solvent is fluoroethylene carbonate, and the low-viscosity solvent is acetonitrile.

[0065] The auxiliary solvent is γ-butyrolactone;

[0066] The electrolyte salt is a complex salt formed by lithium salt and organoboron salt in a molar ratio of 1:2. The lithium salt is lithium bis(fluorosulfonyl)imide (LiN(SO2F)2), and the organoboron salt is tetraethylammonium tetrafluoroborate.

[0067] The preparation method includes the following steps: mixing an ester solvent and a low-viscosity solvent, adding an auxiliary solvent and stirring for 30 min, adding an electrolyte salt to dissolve it, and finally adding perfluoropolyether and 1,3-propane sulpholactone. After ultrasonic dispersion for 1 hour, the mixture is filtered through a 0.22 μm filter membrane to obtain the electrolyte.

[0068] Example 2

[0069] The difference from Example 1 is that the main solvent is replaced with a mixture of an ester solvent and a low-viscosity solvent in a volume ratio of 1:3. The ester solvent is ethylene carbonate and the low-viscosity solvent is 1,2-dimethoxyethane. All other conditions, parameters and preparation methods are the same as in Example 1.

[0070] Example 3

[0071] The difference from Example 1 is that the main solvent is replaced with a mixture of ester solvent and low viscosity solvent in a volume ratio of 3:1. The ester solvent is propylene carbonate and the low viscosity solvent is acetonitrile. All other conditions, parameters and preparation methods are the same as in Example 1.

[0072] Example 4

[0073] The difference from Example 1 is that the electrolyte salt is replaced with lithium hexafluorophosphate and tetraethylammonium tetrafluoroborate in a molar ratio of 1:3. All other conditions, parameters and preparation methods are the same as in Example 1.

[0074] Example 5

[0075] The difference from Example 1 is that the electrolyte salt is replaced with lithium bis(fluorosulfonyl)imide and tetraethylammonium tetrafluoroborate in a molar ratio of 1:1. All other conditions, parameters and preparation methods are the same as in Example 1.

[0076] Example 6

[0077] The difference from Example 1 is that the auxiliary solvent is replaced with butyl acetate, and the mass percentage of the auxiliary solvent in the electrolyte is 10%. That is, the electrolyte is composed of the following components by mass percentage: 0.8% perfluoropolyether, 0.5% 1,3-propanesulfonyl lactone, 81.7% main solvent, 10% auxiliary solvent and 7% electrolyte salt. All other conditions, parameters and preparation methods are the same as in Example 1.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that the main solvent is replaced with fluoroethylene carbonate, while the other conditions, parameters and preparation methods are the same as in Example 1.

[0080] Comparative Example 2

[0081] The difference from Example 1 is that the main solvent is replaced with acetonitrile, while the other conditions, parameters and preparation methods are the same as in Example 1.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that the electrolyte salt is replaced with lithium bis(fluorosulfonyl)imide and tetraethylammonium tetrafluoroborate in a molar ratio of 3:1. All other conditions, parameters and preparation methods are the same as in Example 1.

[0084] Comparative Example 4

[0085] The difference from Example 1 is that the perfluoropolyether and 1,3-propanesulfonyl lactone are replaced with N-trimethylsilylacetamide, that is, the electrolyte is composed of the following components by mass percentage: N-trimethylsilylacetamide 1.3%, main solvent 86.7%, auxiliary solvent 5% and electrolyte salt 7%, and the remaining conditions, parameters and preparation methods are the same as in Example 1.

[0086] Comparative Example 5

[0087] The difference from Example 1 is that the electrolyte is composed of the following components by mass percentage: 0.8% perfluoropolyether, 0.5% 1,3-propanesulfonyl lactone, 78.9% main solvent, 2.8% auxiliary solvent and 17% electrolyte salt. All other conditions, parameters and preparation methods are the same as in Example 1.

[0088] Comparative Example 6

[0089] An electrolyte is composed of a main solvent and an electrolyte salt, wherein the main solvent is acetonitrile (AN) and the electrolyte salt is triethylmethylammonium tetrafluoroborate (Et3MeNBF4), and the mass percentage of the main solvent and the electrolyte salt is 1:1.

[0090] The preparation method includes the following steps: mixing the main solvent and electrolyte salt, ultrasonically dispersing for 1 hour, and then filtering with a 0.22 μm filter membrane to obtain the electrolyte.

[0091] Comparative Example 7

[0092] The difference from Example 1 is that the electrolyte is composed of the following components by mass percentage: 2.2% perfluoropolyether, 84.8% main solvent, 6% auxiliary solvent and 7% electrolyte salt. All other conditions, parameters and preparation methods are the same as in Example 1.

[0093] Comparative Example 8

[0094] The difference from Example 1 is that the electrolyte is composed of the following components by mass percentage: 0.5% 1,3-propanesulfonyl lactone, 82.5% main solvent, 8% auxiliary solvent and 9% electrolyte salt. All other conditions, parameters and preparation methods are the same as in Example 1.

[0095] Experiment Example 1: Performance Testing Test

[0096] The ionic conductivity of the electrolyte in supercapacitors is tested according to the SJ / T 11732-2018 standard, combined with EIS and four-electrode methods to ensure the accuracy and comparability of the data.

[0097] The electrolytes prepared in Examples 1-6 and Comparative Examples 1-8 were tested for ionic conductivity at -55°C, and the results are recorded in Table 1.

[0098] The electrolytes prepared in Examples 1-6, Comparative Examples 1-5, and Comparative Examples 7 and 8 were used in 2.7V-400F capacitors. The capacitance retention rate of the products was tested according to the requirements of GJB8357-2015 for low-temperature performance testing of double-layer capacitors. The results are recorded in Table 1.

[0099] Test method: The product was placed in a low temperature chamber at -55℃ for 16 hours. Then, the 2.7V-400F supercapacitor was charged to the rated voltage of 2.7V with a constant current of 5A. The 2.7V-400F supercapacitor was then discharged to 0.1V with a constant current of 5A. After 3 cycles, the low temperature capacity retention rate of the product was tested.

[0100] Table 1

[0101]

[0102] The results showed that in Example 1, the main solvent was a mixture of fluoroethylene carbonate and acetonitrile with a freezing point of -65°C. Under ultra-low temperature conditions, the main solvent could still remain liquid. When the main solvent in the electrolyte was replaced with fluoroethylene carbonate (freezing point of 18°C) or acetonitrile (freezing point of -45°C), the main solvent would reach its freezing point under ultra-low temperature conditions, resulting in a sharp decrease in the ionic conductivity of the electrolyte and a significant decrease in the capacitance retention of the capacitor.

[0103] When the ratio of lithium salt to organic boron salt in the electrolyte is unreasonable, such as excessive lithium salt content, it will lead to an imbalance in the solvation structure, an increase in electrolyte viscosity, and a high salt concentration viscosity reaction, which will reduce ionic conductivity and capacitor capacity.

[0104] Replacing the additives perfluoropolyether and 1,3-propanesulfonyl lactone with N-trimethylsilylacetamide can lead to problems. N-trimethylsilylacetamide is highly sensitive to moisture and is easily hydrolyzed, generating HF (hydrofluoric acid) and silanol byproducts with other components in the electrolyte. This results in increased HF corrosivity, damage to the diaphragm, and consequently affects the performance of the electrolyte.

[0105] As shown in the results of the five comparative examples, an increase in the content of electrolyte salts in the electrolyte usually increases the ionic conductivity. However, when the content of electrolyte salts is too high, the viscosity of the electrolyte will increase significantly, the wettability will decrease, and the low-temperature adaptability of the electrolyte will decrease, thereby causing the ionic conductivity of the electrolyte to decrease.

[0106] As shown in the results of Comparative Examples 7 and 8, when only perfluoropolyether or 1,3-propane sulfonyl lactone was used as the additive, the ionic conductivity of the electrolyte and the capacitance retention of the capacitor were lower than those of Example 1. This indicates that the simultaneous addition of perfluoropolyether and 1,3-propane sulfonyl lactone to the electrolyte can improve the ionic conductivity of the electrolyte and enable the capacitor to maintain a high capacitance retention under low temperature conditions.

[0107] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A low-temperature electrolyte, characterized in that, Including main solvent, auxiliary solvent, electrolyte salt, perfluoropolyether and 1,3-propane sulpholactone; The main solvent has a mass percentage of 80-88% and is composed of an ester solvent and a low-viscosity solvent in a volume ratio of 1:(0.2-3); the ester solvent includes any one or more of fluoroethylene carbonate, ethylene carbonate, and propylene carbonate; the low-viscosity solvent includes any one or more of acetonitrile and 1,2-dimethoxyethane. The auxiliary solvent has a mass percentage of 5-10%, including any one or more of γ-butyrolactone, butyl acetate, and ethyl propionate. The electrolyte salt has a mass percentage of 5-10% and is composed of lithium salt and organoboron salt in a molar ratio of 1:(1-3); the lithium salt includes any one or more of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; the organoboron salt includes any one or more of methyltriethylammonium tetrafluoroborate and tetraethylammonium tetrafluoroborate. The amount of perfluoropolyether added is 0.5-1%; The amount of 1,3-propanesulfonyl lactone added is 0.5-1%.

2. The low-temperature electrolyte according to claim 1, characterized in that, The amount of perfluoropolyether added is 0.5~0.8%; And / or, the amount of 1,3-propanesulfonyl lactone added is 0.5~0.8%.

3. The low-temperature electrolyte according to claim 1, characterized in that, The auxiliary solvent has a mass percentage content of 5-7%; And / or, the low temperature refers to a temperature of -80℃ to -40℃.

4. The low-temperature electrolyte according to claim 1, characterized in that, The low temperature refers to a temperature of -60℃ to -40℃.

5. The low-temperature electrolyte according to claim 1, characterized in that, The volume ratio of the ester solvent to the low-viscosity solvent is 1:

1.

6. The low-temperature electrolyte according to claim 1, characterized in that, The molar ratio of the lithium salt to the organoboron salt is 1:

2.

7. The method for preparing the low-temperature electrolyte according to any one of claims 1 to 6, characterized in that, Includes the following steps: The auxiliary solvent is added to the main solvent and stirred until homogeneous. The electrolyte salt is added and dissolved. Perfluoropolyether and 1,3-propane sulpholactone are added, dispersed, and then filtered to obtain the low-temperature electrolyte.

8. The application of the low-temperature electrolyte as described in any one of claims 1 to 6 or the low-temperature electrolyte obtained by the preparation method as described in claim 7 in supercapacitors.

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