Electrolyte, secondary battery and electrical device

Abstract

This application relates to an electrolyte, a secondary battery, and an electrical device. The electrolyte comprises an electrolyte salt and a fluorosulfonamide solvent. The fluorosulfonamide solvent comprises a compound of formula (1): wherein T1 is selected from any one of formulas (1-1) to (1-3); R1 and R2 are independently selected from any one of alkyl, phenyl, and sulfone groups having 1 to 3 carbon atoms; T2 is a fluorinated alkyl group having 1 to 4 carbon atoms; * represents a linking site.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an electrolyte, a secondary battery, and an electrical device. Background Technology

[0002] Lithium batteries and other secondary batteries are increasingly widely used due to their clean and renewable characteristics. Lithium-ion secondary batteries have been widely used in consumer electronics, electric vehicles, energy storage and many other fields.

[0003] To meet the demand for higher energy density batteries in applications such as long-range electric vehicles and electric aircraft, lithium metal secondary batteries with higher energy density have been researched and developed, showing broad application prospects in long-range power batteries, electric aircraft, and electric flight vehicles. However, the performance improvement of lithium metal batteries is severely limited by the electrolyte. Traditional electrolytes are prone to decomposition and cause the growth of lithium dendrites, which has a significant negative impact on key performance indicators such as battery cycle performance and rate performance, and in severe cases, can lead to safety accidents.

[0004] Therefore, traditional techniques need further improvement. Summary of the Invention

[0005] Therefore, it is necessary to provide an electrolyte, a secondary battery, and an electrical device to improve the rate performance and cycle performance of the battery.

[0006] This application is achieved through the following technical solution.

[0007] A first aspect of this application provides an electrolyte comprising an electrolyte salt and a fluorosulfonamide solvent, the fluorosulfonamide solvent comprising a compound of formula (1):

[0008]

[0009] Where T1 is selected from any one of the following equations (1-1) to (1-3):

[0010]

[0011] R1 and R2 are each independently selected from any one of alkyl, phenyl, and sulfone groups having 1 to 3 carbon atoms;

[0012] T2 is an alkyl group with 1 to 4 carbon atoms that has been substituted with fluorine;

[0013] * Represents a connection point.

[0014] The electrolyte contains a fluorinated sulfonamide solvent with a specific structure. The compound shown in formula (1) contains a sulfonamide group. One side of the sulfonamide group is attached to a fluorinated alkyl group with 1 to 4 carbon atoms that has strong electron-withdrawing properties. The sulfonamide group and the fluorinated alkyl group with 1 to 4 carbon atoms are not directly connected, but are separated by one carbon atom. In this way, on the one hand, a group with stronger electron-withdrawing properties than the sulfonyl functional group is introduced on the side of the sulfonamide group to reduce the coordination ability of the sulfonyl functional group with lithium ions in the compound shown in formula (1). This makes the overall coordination ability of the fluorinated sulfonamide solvent with lithium ions weaker than the coordination ability of the anion in the inner solvent sheath structure of lithium ions. In other words, it substantially increases the coordination number of the anion, making it easier to gain electrons and undergo reduction decomposition to generate a dense interface film mainly composed of inorganic substances. This film has a lower diffusion barrier and a faster transport rate. In particular, it can increase the coordination number of anions in the electrolyte portion (i.e., the bulk electrolyte portion) that diffuses to the electrode interface, which is beneficial to the rate performance of the battery. On the other hand, by separating the sulfonamide group from the group with strong electron-withdrawing properties by one carbon atom, the β-position carbon atom connected to the sulfonamide group or the carbon atom farther away from the sulfonamide group than the β-position carbon atom is replaced by fluorine, so that the electron-withdrawing ability of the sulfonyl functional group in the compound shown in formula (1) is kept at an appropriate gap with the electron-withdrawing ability of the group portion connected to it, so that the sulfonyl functional group still has a certain ability to coordinate with lithium ions, so that the compound shown in formula (1) still has a high number of donors, improves its ability to dissolve electrolyte lithium salt, and makes the electrolyte have both good anion coordination performance and good ionic conductivity. When applied to the preparation of secondary batteries, it can simultaneously improve the rate performance and cycle performance of the battery.

[0015] Meanwhile, the fluorosulfonamide solvent with the above-mentioned specific structure can reduce the solubility of the decomposition products at the positive electrode interface, improve the stability of the interface film, inhibit the penetration of the electrolyte into the intergranular particles of the positive electrode, avoid chemical corrosion at the positive electrode grain boundaries, improve the phase stability of the positive electrode, and the electrolyte has low solubility for corrosion products of aluminum foil current collectors such as Al(FSI)3, which reduces the negative impact of such corrosion products and can further slow down the high-pressure corrosion of the current collector.

[0016] In particular, when the above-mentioned electrolyte is used to prepare lithium metal secondary batteries, it is beneficial to the uniform deposition of lithium ions and inhibits dendrite growth.

[0017] In some embodiments, the structure of T2 is as shown in (A):

[0018]

[0019] R3 is selected from H, F, alkyl groups having 1 to 3 carbon atoms, or alkyl groups having 1 to 3 carbon atoms that are substituted with fluorine. R4 and R5 are each independently selected from H or F, and at least one of R4 and R5 is F.

[0020] This ensures that at least one hydrogen atom on the β-position carbon atom connected to the sulfonamide group is replaced by fluorine, thereby achieving a better balance between the coordination ability of the fluorinated sulfonamide solvent and the coordination ability of the anion, further improving the anion coordination performance and good ionic conductivity of the electrolyte.

[0021] Further research has shown that, compared to fluorinated sulfonamide solvents formed by replacing carbon atoms farther from the sulfonamide group than the β-carbon atom, replacing at least one hydrogen atom on the β-carbon atom connected to the sulfonamide group with fluorine can improve the solubility of electrolyte salts in fluorinated sulfonamide solvents by increasing the coordination number of anions, thereby further improving the ionic conductivity of the electrolyte.

[0022] In some of these embodiments, R3 is selected from H or F.

[0023] In some of these embodiments, T1 is selected from formula (1-1), and R1 and R2 are each independently selected from alkyl or phenyl groups having 1 to 3 carbon atoms.

[0024] When T1 is selected from formula (1-1), its specific structure can improve the compatibility between the fluorosulfonamide solvent and the lithium metal anode, effectively reduce the side reactions of the electrolyte at the lithium metal anode, and further improve the cycle performance of the battery.

[0025] Optionally, R1 and R2 are both alkyl groups having 1 to 3 carbon atoms.

[0026] Studies have found that when R1 and R2 are selected from alkyl groups with 1 to 3 carbon atoms, the ionic conductivity of the electrolyte can be further improved, the viscosity of the electrolyte can be reduced, and the cycle performance of the battery can be improved.

[0027] In some embodiments, the fluorosulfonamide solvent includes at least one of the compounds represented by formulas (1a) to (1r):

[0028]

[0029] In some embodiments, the electrolyte further comprises a fluorinated carboxylic acid ester solvent;

[0030] Optionally, the structure of the fluorinated carboxylic acid ester solvent is shown in formula (B):

[0031]

[0032] R6 and R7 are each independently selected from any one of alkyl groups having 1 to 5 carbon atoms, alkyl groups having 1 to 5 carbon atoms that are fluorinated, cycloalkyl groups having 3 to 6 carbon atoms, and cycloalkyl groups having 3 to 6 carbon atoms that are fluorinated, and at least one of R6 and R7 is selected from alkyl groups having 1 to 5 carbon atoms that are fluorinated or cycloalkyl groups having 3 to 6 carbon atoms that are fluorinated;

[0033] Alternatively, R6 and R7 are each independently selected from alkyl groups having 1 to 5 carbon atoms or alkyl groups having 1 to 5 carbon atoms that have been substituted with fluorine, and at least one of R6 and R7 is an alkyl group having 1 to 5 carbon atoms that has been substituted with fluorine.

[0034] Fluorinated carboxylic acid ester solvents can further enhance the coordination ability of anions and lithium ions, increase the proportion of anion coordination number in the bulk electrolyte, which is beneficial to improving the negative electrode interface properties and can also improve the wettability of the electrolyte to the separator. In synergy with the above-mentioned fluorinated sulfonamide solvents with specific structures, the cycle performance of secondary batteries can be further improved.

[0035] In some embodiments, the fluorinated carboxylic acid ester solvent includes at least one selected from ethyl 2,2,2-trifluoroacetate, propyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, methyl difluoroacetate, ethyl 3,3,3-trifluoropropionate, and ethyl 3,3-trifluoropropionate.

[0036] In some embodiments, the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is (0.2-5):1;

[0037] Optionally, the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is (0.5-3):1;

[0038] Further optionally, the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is (1.5 to 2.25):1.

[0039] By adjusting the volume ratio of fluorosulfonamide solvent to fluorocarboxylic acid ester solvent, a better balance is achieved between the coordination ability of the fluorosulfonamide solvent and the coordination ability of the anion, thereby further improving the anion coordination performance and good ionic conductivity of the electrolyte.

[0040] In some embodiments, the mass ratio of the electrolyte salt to the fluorosulfonamide solvent in the electrolyte is (0.068–0.68):1.

[0041] In some embodiments, the electrolyte satisfies at least one of the following conditions (a) to (b):

[0042] (a) In the electrolyte, the concentration of the electrolyte salt is 0.5 mol / L to 5 mol / L;

[0043] (b) The electrolyte salt includes lithium-ion electrolyte salts;

[0044] Optionally, the lithium-ion electrolyte salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0045] A second aspect of this application provides a secondary battery, said secondary battery comprising the electrolyte of the first aspect.

[0046] In some embodiments, the secondary battery described above includes a lithium metal secondary battery.

[0047] The aforementioned secondary batteries exhibit excellent cycle performance.

[0048] A third aspect of this application provides an electrical device comprising the secondary battery of the second aspect. Attached Figure Description

[0049] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0050] Figure 1 This is a schematic diagram of one embodiment of a battery cell;

[0051] Figure 2 yes Figure 1 Exploded view;

[0052] Figure 3 This is a schematic diagram of one embodiment of the battery pack;

[0053] Figure 4 yes Figure 3 Exploded view;

[0054] Figure 5 This is a schematic diagram of one embodiment of an electrical device in which a battery is used as a power source.

[0055] Explanation of reference numerals in the attached figures:

[0056] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Individual battery cell; 41. Housing; 42. Electrode assembly; 43. Cover plate; 5. Electrical device. Detailed Implementation

[0057] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0059] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0060] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0061] In this application, the term "alkyl" refers to a group formed by the loss of a hydrogen atom from an alkane, such as methyl from the loss of a hydrogen atom from methane. The term "chain alkyl" refers to a group formed by the loss of a hydrogen atom from an alkane in which all carbon atoms are linked by carbon-carbon single bonds and do not form a ring, and the remaining valence bonds are bonded to hydrogen atoms; this includes straight-chain alkyl groups and branched-chain alkyl groups.

[0062] In this application, the number of carbon atoms in "alkyl group having 1 to 5 carbon atoms" can be 1 to 5, including 1, 2, 3, 4 or 5, and non-limiting examples include methane, ethane, and n-propane.

[0063] In summary, the performance improvement of traditional secondary batteries, especially lithium metal secondary batteries, is severely limited by the electrolyte, which is mainly composed of ester solvents: carbonates or carboxylic acid esters.

[0064] Studies have found that fluorosulfonamide compounds, when used as additives in electrolytes, can improve the electrolyte's high-voltage resistance and enhance its high-temperature storage performance.

[0065] However, further research has shown that when fluorosulfonamide compounds are used as solvents for electrolytes, the substitution position of fluorine atoms is closely related to the anion coordination ability and ionic conductivity of the electrolyte.

[0066] Based on this, after extensive creative exploration, the electrolyte in this application that can improve the rate capability and cycle performance of the battery was obtained.

[0067] One embodiment of this application provides an electrolyte comprising an electrolyte salt and a fluorosulfonamide solvent, wherein the fluorosulfonamide solvent comprises a compound of formula (1):

[0068]

[0069] Where T1 is selected from any one of the following equations (1-1) to (1-3):

[0070]

[0071] R1 and R2 are each independently selected from any one of alkyl, phenyl, and sulfone groups having 1 to 3 carbon atoms;

[0072] T2 is an alkyl group with 1 to 4 carbon atoms that has been substituted with fluorine;

[0073] * Represents a connection point.

[0074] The electrolyte contains a fluorinated sulfonamide solvent with a specific structure. The compound shown in formula (1) contains a sulfonamide group. One side of the sulfonamide group is attached to a fluorinated alkyl group with 1 to 4 carbon atoms that has strong electron-withdrawing properties. The sulfonamide group and the fluorinated alkyl group with 1 to 4 carbon atoms are not directly connected, but are separated by one carbon atom. In this way, on the one hand, a group with stronger electron-withdrawing properties than the sulfonyl functional group is introduced on the side of the sulfonamide group to reduce the coordination ability of the sulfonyl functional group with lithium ions in the compound shown in formula (1). This makes the overall coordination ability of the fluorinated sulfonamide solvent with lithium ions weaker than the coordination ability of the anion in the inner solvent sheath structure of lithium ions. In other words, it substantially increases the coordination number of the anion, making it easier to gain electrons and undergo reduction decomposition to generate a dense interface film mainly composed of inorganic substances. This film has a lower diffusion barrier and a faster transport rate. In particular, it can increase the coordination number of anions in the electrolyte portion (i.e., the bulk electrolyte portion) that diffuses to the electrode interface, which is beneficial to the rate performance of the battery. On the other hand, by separating the sulfonamide group from the group with strong electron-withdrawing properties by one carbon atom, the β-position carbon atom connected to the sulfonamide group or the carbon atom farther away from the sulfonamide group than the β-position carbon atom is replaced by fluorine, so that the electron-withdrawing ability of the sulfonyl functional group in the compound shown in formula (1) is kept at an appropriate gap with the electron-withdrawing ability of the group portion connected to it, so that the sulfonyl functional group still has a certain ability to coordinate with lithium ions, so that the compound shown in formula (1) still has a high number of donors, improves its ability to dissolve electrolyte lithium salt, and makes the electrolyte have both good anion coordination performance and good ionic conductivity. When applied to the preparation of secondary batteries, it can simultaneously improve the rate performance and cycle performance of the battery.

[0075] Meanwhile, the fluorosulfonamide solvent with the above-mentioned specific structure can reduce the solubility of the decomposition products at the positive electrode interface, improve the stability of the interface film, inhibit the penetration of the electrolyte into the intergranular particles of the positive electrode, avoid chemical corrosion at the positive electrode grain boundaries, improve the phase stability of the positive electrode, and the electrolyte has low solubility for corrosion products of aluminum foil current collectors such as Al(FSI)3, which reduces the negative impact of such corrosion products and can further slow down the high-pressure corrosion of the current collector.

[0076] In particular, when the above-mentioned electrolyte is used to prepare lithium metal secondary batteries, it is beneficial to the uniform deposition of lithium ions and inhibits dendrite growth.

[0077] In some embodiments, R3 is selected from H, F, straight-chain alkyl groups having 1 to 3 carbon atoms, or straight-chain alkyl groups having 1 to 3 carbon atoms that have been substituted with fluorine.

[0078] In some embodiments, R3 is selected from H, F, straight-chain alkyl groups having 1 to 2 carbon atoms, or straight-chain alkyl groups having 1 to 2 carbon atoms that have been substituted with fluorine.

[0079] In some of these embodiments, R3 is selected from any one of H, F, methyl, ethyl, and trifluoromethyl.

[0080] In some of these embodiments, R3 is selected from H or F.

[0081] In some of these embodiments, T1 is selected from formula (1-1).

[0082] In some of these embodiments, R1 and R2 are each independently selected from alkyl or phenyl groups having 1 to 3 carbon atoms.

[0083] When T1 is selected from formula (1-1), its specific structure can improve the compatibility between the fluorosulfonamide solvent and the lithium metal anode, effectively reduce the side reactions of the electrolyte at the lithium metal anode, and further improve the cycle performance of the battery.

[0084] In some of these embodiments, R1 and R2 are each independently selected from alkyl or phenyl groups having 1 to 3 carbon atoms.

[0085] In some of these embodiments, R1 and R2 are each independently selected from methyl, ethyl, or phenyl.

[0086] In some embodiments, R1 and R2 are both selected from alkyl or phenyl groups having 1 to 3 carbon atoms.

[0087] Studies have found that when R1 and R2 are selected from alkyl groups with 1 to 3 carbon atoms, the ionic conductivity of the electrolyte can be further improved, the viscosity of the electrolyte can be reduced, and the cycle performance of the battery can be improved.

[0088] In some embodiments, R1 and R2 are both alkyl groups having 1 to 3 carbon atoms.

[0089] In some of these embodiments, R1 and R2 are each independently selected from methyl, ethyl, or propyl.

[0090] In some of these embodiments, R1 and R2 are both selected from methyl, ethyl, or propyl.

[0091] In some embodiments, the fluorosulfonamide solvent includes at least one of the compounds shown in formulas (1a) to (1r):

[0092]

[0093]

[0094] The compound shown in formula (1) above can be purchased commercially or synthesized by the following preparation method:

[0095] The compound of formula (1) is prepared by substituting the compound of formula (A) with the compound of formula (B); wherein the compound of formula (B) includes at least one of the compounds of formula (B-1) to (B-3).

[0096]

[0097] The choices of T2, R1, and R2 are the same as above, and will not be repeated here.

[0098] In some embodiments, the above substitution reaction is carried out under alkaline conditions; further, the alkaline environment is controlled by adding alkaline substances.

[0099] In some embodiments, the alkaline substance includes at least one of organic and inorganic bases.

[0100] In some embodiments, the organic base includes organic amines, and specific examples include, but are not limited to, triethylamine.

[0101] In some of these embodiments, the substitution reaction is carried out in an organic solvent; further, the organic solvent includes, but is not limited to, at least one of tetrahydrofuran and dichloromethane.

[0102] In some of these embodiments, the molar ratio of compound (A) to compound (B) is 1:(1-3).

[0103] In some embodiments, the molar ratio of the compound of formula (A) to the basic substance is 1:(1 to 3).

[0104] In some embodiments, the substitution reaction is carried out at 5°C to 10°C by first adding the compound of formula (A) dropwise into a solution containing the compound of formula (B), and then reacting at room temperature for 10 to 20 hours.

[0105] The room temperature can be between 20℃ and 35℃.

[0106] In some embodiments, the above preparation method further includes a post-processing step:

[0107] The product after the substitution reaction was extracted with an extractant, then concentrated to remove the extractant, and then subjected to vacuum distillation to obtain the purified compound shown in formula (1).

[0108] In some of these embodiments, the extractant includes dichloromethane.

[0109] The above preparation method is simple to operate, has mild conditions, produces few by-products, and can achieve a high yield.

[0110] In some embodiments, the electrolyte also includes a fluorinated carboxylic acid ester solvent.

[0111] Studies have found that fluorinated carboxylic acid ester solvents, in synergy with the compounds shown in formula (1) above, can further improve the coordination ability of anions and lithium ions, increase the proportion of coordination number of anions in the bulk electrolyte, which is beneficial to improve the properties of the negative electrode interface and can improve the wettability of the electrolyte to the separator. In synergy with the fluorinated sulfonamide solvents with the above specific structure, the cycle performance of secondary batteries can be further improved.

[0112] In some embodiments, the structure of the fluorinated carboxylic acid ester solvent is shown in formula (B):

[0113]

[0114] R6 and R7 are each independently selected from any one of the following: alkyl groups having 1 to 5 carbon atoms, alkyl groups having 1 to 5 carbon atoms that have been fluorinated, cycloalkyl groups having 3 to 6 carbon atoms, and cycloalkyl groups having 3 to 6 carbon atoms that have been fluorinated, and at least one of R6 and R7 is selected from either alkyl groups having 1 to 5 carbon atoms that have been fluorinated or cycloalkyl groups having 3 to 6 carbon atoms that have been fluorinated.

[0115] In some embodiments, R6 and R7 are each independently selected from alkyl groups having 1 to 5 carbon atoms or alkyl groups having 1 to 5 carbon atoms that have been fluorinated, and at least one of R6 and R7 is an alkyl group having 1 to 5 carbon atoms that has been fluorinated.

[0116] In some embodiments, R6 and R7 are each independently selected from alkyl groups having 1 to 3 carbon atoms or alkyl groups having 1 to 3 carbon atoms that have been fluorinated, and at least one of R6 and R7 is an alkyl group having 1 to 3 carbon atoms that has been fluorinated.

[0117] In some embodiments, R6 and R7 are each independently selected from any one of methyl, ethyl, propyl, fluorinated methyl, fluorinated ethyl, or fluorinated propyl.

[0118] In some of these embodiments, at least one of R6 and R7 is selected from fluorinated methyl, fluorinated ethyl, or fluorinated propyl.

[0119] In this application, "propyl" includes at least one of n-propyl and isopropyl.

[0120] In some embodiments, the fluorinated carboxylic acid ester solvent includes at least one selected from ethyl 2,2,2-trifluoroacetate, propyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, methyl difluoroacetate, ethyl 3,3,3-trifluoropropionate, and ethyl 3,3-trifluoropropionate.

[0121] In some embodiments, the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is (0.2-5):1.

[0122] In some embodiments, the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is (0.5-3):1.

[0123] In some embodiments, the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is (1.5 to 2.25):1.

[0124] By adjusting the volume ratio of fluorosulfonamide solvent to fluorocarboxylic acid ester solvent, a better balance is achieved between the coordination ability of the fluorosulfonamide solvent and the coordination ability of the anion, thereby further improving the anion coordination performance and good ionic conductivity of the electrolyte.

[0125] In the above "(0.2~5):1", the value includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 5:1, 4:1, 3:1, 2:1, 1:1, 0.5:1, 0.4:1, 0.3:1, 0.2:1; or any range of two values, for example, (0.2~5):1, (0.2~4):1, (0.2~3):1, (0.5~5):1, (0.5~4):1, (0.5~3):1, (0.5~2.5):1, (1~5):1, (1~4):1, (1~3):1, (2~5):1, (2~4):1, (2~3):1.

[0126] In some embodiments, the mass ratio of the electrolyte salt to the fluorosulfonamide solvent in the electrolyte is (0.068–0.68):1.

[0127] In the above "(0.068~0.68):1", the values ​​include the minimum and maximum values ​​within this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 0.68:1, 0.6:1, 0.58:1, 0.55:1, 0.5:1, 0.45:1, 0.4:1, 0.35:1, 0.3:1, 0.25:1, 0.2:1, 0.15:1, 0.1:1, 0.08:1, 0.07:1; or any two values. The range, for example, can be (0.07~0.6):1, (0.08~0.5):1, (0.068~0.4):1, (0.068~0.3):1, (0.068~0.2):1, (0.068~0.1):1, (0.1~0.5):1, (0.1~0.4):1, (0.1~0.3):1, (0.1~0.2):1, (0.2~0.5):1, (0.2~0.4):1, (0.2~0.3):1, (0.2~0.6):1.

[0128] In some embodiments, the concentration of the electrolyte salt in the electrolyte is 0.5 mol / L to 5 mol / L.

[0129] In some of these embodiments, the concentration of the electrolyte salt is 1 mol / L to 3 mol / L.

[0130] In some of these embodiments, the concentration of the electrolyte salt is 1.5 mol / L to 2.5 mol / L.

[0131] In one specific example, the concentration of the electrolyte salt is 2 mol / L.

[0132] Adjusting the concentration of the electrolyte salt to balance high ionic conductivity and low viscosity further enhances the positive impact of the electrolyte on the stability of the positive and negative electrodes. In some embodiments, the electrolyte salt may be selected from at least one of commonly used electrolyte salts in the art, such as lithium-ion electrolyte salts, sodium-ion electrolyte salts, and potassium-ion electrolyte salts.

[0133] In some embodiments, the electrolyte salt described above includes a lithium-ion electrolyte salt.

[0134] As an example, lithium-ion electrolyte salts include, but are not limited to, one or more of the following: LiNO3, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0135] Studies have found that the electrolyte exhibits good solubility for the aforementioned lithium-ion electrolyte salts; furthermore, its solubility for LiNO3 is slightly lower compared to other types of lithium-ion electrolyte salts.

[0136] Optionally, the lithium-ion electrolyte salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0137] According to one embodiment of this application, a secondary battery is provided, which includes an electrolyte of the first aspect.

[0138] In some embodiments, the secondary battery further includes a positive electrode, a negative electrode, and a separator.

[0139] Positive electrode: The positive electrode includes a current collector and a positive active layer loaded on the surface of the current collector.

[0140] The positive electrode active layer comprises a positive electrode active material. The positive electrode active material may be any commonly used positive electrode active material in the art, including but not limited to: positive electrode active materials for lithium-ion batteries, positive electrode active materials for sodium-ion batteries, and positive electrode active materials for potassium-ion batteries.

[0141] The positive electrode active materials for lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries are referred to as lithium-ion active materials, sodium-ion active materials, and potassium-ion active materials, respectively, below.

[0142] Further, as an example, lithium-ion active materials may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4, abbreviated as LFP), lithium manganese phosphate (such as LiMnPO4), and lithium manganese iron phosphate. In any embodiment of this application, the molecular formula of the lithium-ion active material is: LiFe x Mn (1-x) PO4, where x takes any number from 0 to 1.

[0143] It is understandable that when x is 0, LiFe x Mn (1-x) PO4 is lithium manganese phosphate (LiMnPO4). When x is 1, LiFePO4 is lithium iron phosphate (LiFePO4).

[0144] It should be noted that the lithium content in the cathode material mentioned above refers to its content when it is not in use. During battery use, it will be repeatedly charged, and the Li in the cathode active material will change during the charging and discharging process. That is, the molar subscript of Li in the cathode active material of the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0145] For example, LiFe x Mn (1-x) PO4 can be further represented as Li y Fe x Mn (1-x) PO4, y is 0 to 1.1.

[0146] For example, regarding the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x y is 0.2 to 1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn and Al, and A is one or more of S, N, F, Cl, Br and I.

[0147] During the charging and discharging process, Li will be extracted and consumed. The molar content of Li will be different when the battery is discharged to different states. The above limitation on y includes the molar content of Li in different charging and discharging states of the battery. Furthermore, the battery voltage is usually between 2-5V.

[0148] As an example, sodium-ion active materials may include at least one of the following: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0149] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide includes at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na. x MO2, wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0150] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n-A class of compounds with anionic units. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y includes at least one of P, S, and Si; n represents (YO4). n- The price state.

[0151] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds comprising anionic units and halide anions. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y includes at least one of P, S, and Si, where n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0152] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y includes at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents (ZO). y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0153] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7)(NFPP), NaM1PO4F, and Na3(VO y )2(PO4)2F (3-2y) At least one of them.

[0154] M1 is at least one of V, Fe, Mn and Ni, and 0≤y≤1.

[0155] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a M2 b M3 c(CN)6, wherein M2 and M3 are each independently selected from at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0156] In any embodiment of this application, the mass percentage of the positive electrode active material in the positive electrode active layer is 70% to 99.8%.

[0157] In any embodiment of this application, the components of the positive electrode active layer further include a conductive agent and a binder.

[0158] Taking the aforementioned electrode sheet as the positive electrode as an example, the conductive agent can be a commonly used conductive agent in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, it can be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene and their composite conductive agents.

[0159] The adhesive can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS), and fluorinated acrylate resins.

[0160] Optionally, the conductive agent accounts for 1% to 20% of the mass in the positive electrode active layer.

[0161] Optionally, the binder accounts for 1% to 10% of the mass of the positive electrode active layer.

[0162] In some embodiments, the thickness of the positive electrode active layer is 30 μm to 200 μm.

[0163] In any embodiment of this application, the current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate.

[0164] In some embodiments, the metallic material is selected from any one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys.

[0165] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0166] In any embodiment of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto a current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solid content of the positive electrode slurry is 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s. The positive electrode slurry is coated onto the surface of the positive electrode current collector, dried, and then cold-pressed using a cold rolling mill to form the positive electrode sheet.

[0167] Furthermore, the solvent includes N-methylpyrrolidone.

[0168] In some embodiments, the areal density of the positive electrode active material contained in the positive electrode sheet is 0.018 g / cm³. 2 ~0.05g / cm 2 .

[0169] The areal density of the positive electrode active material = the mass of the positive electrode active material / the area of ​​the positive electrode sheet.

[0170] Negative electrode: The negative electrode includes a current collector and a negative electrode active layer loaded on the surface of the current collector.

[0171] The components of the negative electrode active layer include negative electrode active materials.

[0172] The aforementioned negative electrode active material can be any commonly used negative electrode active material described in this application.

[0173] In any embodiment of this application, the aforementioned negative electrode active material includes mesophase carbon microspheres, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials, iron-based materials, lithium metal, lithium metal, and alloys formed by other metals or non-metals; further, the other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), and foil (Pt); the non-metals include at least one of boron (B), carbon (C), and silicon (Si).

[0174] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to, at least one of the following: mesophase carbon microspheres, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal, and lithium metal alloys.

[0175] In any embodiment of this application, the battery is a lithium battery, and the mass percentage of the negative electrode active material in the negative electrode active layer is 70% to 100%.

[0176] In any embodiment of this application, the components of the above-mentioned negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0177] In any embodiment of this application, the aforementioned negative electrode conductive agent can be a commonly used conductive material in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, it can be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, and graphene and their composite conductive agents.

[0178] Based on the total weight of the negative electrode active layer, the weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0–20 wt%.

[0179] The aforementioned negative electrode binder can be a commonly used binder in the art, and can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl methacrylate (PMAA), and carboxymethyl chitosan (CMCS).

[0180] Based on the total weight of the negative electrode active layer, the weight ratio of the negative electrode binder in the negative electrode active layer is 0–30 wt%.

[0181] In any embodiment of this application, the negative electrode active layer may optionally include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na). Based on the total weight of the negative electrode active layer, the weight ratio of other additives in the negative electrode active layer is 0 to 15 wt%.

[0182] In any embodiment of this application, the current collector in the negative electrode can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil.

[0183] Composite current collectors may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Composite current collectors can be formed by forming a metal material on a polymer substrate.

[0184] In some embodiments, the metallic material is selected from any one of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys.

[0185] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0186] In any embodiment of this application, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then performing processes such as drying and cold pressing to obtain the negative electrode sheet. The negative electrode slurry has a solid content of 30wt% to 70wt% and its viscosity at room temperature is adjusted to 2000 mPa·s to 10000 mPa·s; the obtained negative electrode slurry is coated onto a negative electrode current collector, and after drying and cold pressing (e.g., with rollers), the negative electrode sheet is obtained.

[0187] In some embodiments, the areal density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm³. 2 ~0.03g / cm 2 .

[0188] The areal density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0189] In some embodiments, the secondary battery is a "lithium metal secondary battery". In this case, no negative electrode active material is added during the preparation of the negative electrode sheet. Only the negative electrode current collector or the current collector coated with a conductive agent is used as the nominal negative electrode. The negative electrode current collector does not have the function of a negative electrode in a substantial sense. After the battery is assembled and charged for the first time, the lithium element in the positive electrode migrates to the surface of the negative electrode current collector, and a lithium metal layer is formed on the negative electrode current collector, thus obtaining a true negative electrode; or a lithium metal sheet is directly used as the negative electrode.

[0190] Furthermore, the lithium-containing metal sheet can be metallic lithium, or it can be an alloy formed by metallic lithium with other metallic or non-metallic elements.

[0191] In some of these embodiments, other metallic elements include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), and foil (Pt).

[0192] In some embodiments, the nonmetallic element includes at least one of boron (B), carbon (C), and silicon (Si).

[0193] Separator: The separator is placed between the positive electrode and the negative electrode.

[0194] The separator in this application can be any known porous separator with good chemical and mechanical stability.

[0195] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0196] The thickness of the diaphragm is controlled between 2 μm and 15 μm; optionally, the thickness of the diaphragm is controlled between 2 μm and 13 μm.

[0197] The secondary battery of this application can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The cell 4 is a secondary battery with a square structure, serving as an example.

[0198] In some embodiments, refer to Figure 2 The outer casing may include a housing 41 and a cover plate 43. The housing 41 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 41 has an opening communicating with the receiving cavity, and the cover plate 43 can be placed over the opening to close the receiving cavity.

[0199] The positive electrode, negative electrode, and separator can be formed into electrode assembly 42 by winding or stacking processes. Electrode assembly 42 is encapsulated within a receiving cavity. Electrolyte is immersed in electrode assembly 42. The number of electrode assemblies 42 contained in a single battery cell 4 can be one or more, and can be adjusted according to requirements.

[0200] A secondary battery comprises one or more battery cells 4.

[0201] The secondary battery can be a battery module or a battery pack; a battery module or battery pack includes at least one battery cell. A battery module can contain one or more battery cells, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0202] Figure 3 and Figure 4 Here is an example of a battery pack 1. The battery pack 1 includes a battery box and one or more battery cells 4 disposed in the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 being able to cover the lower box 3 and form an enclosed space for the battery cells 4.

[0203] Multiple battery cells 4 can be arranged in the battery box in any way.

[0204] This application also provides an electrical device that includes the aforementioned secondary battery.

[0205] Furthermore, in the aforementioned electrical device, the secondary battery can exist in the form of a single battery cell, or it can be further assembled into a battery pack.

[0206] The aforementioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device or as an energy storage unit for an electrical device.

[0207] The aforementioned electrical devices may include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.

[0208] Mobile devices include, but are not limited to: mobile phones, laptops, etc., and electric vehicles include, but are not limited to: pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0209] Figure 5 This is an example of an electrical device 5. This electrical device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this electrical device 5, a battery pack can be used.

[0210] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0211] The present invention will now be described with reference to specific embodiments. However, the present invention is not limited to the embodiments described below. It should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art should realize that any changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

[0212] The following are specific examples.

[0213] Example 1

[0214] S1. Preparation of lithium metal secondary batteries

[0215] (1) Preparation of electrolyte:

[0216] A mixed solvent was prepared by thoroughly mixing ethyl 3,3,3-trifluoropropionate (FEP) and 2,2,2-trifluoro-N,N-dimethylethanesulfonamide (DMTESA) in a volume ratio of 1:2. Then, 1.87 g of lithium bis(fluorosulfonyl)imide was added to 5 mL of the mixed solvent and stirred thoroughly to obtain the electrolyte, which was then ready for use.

[0217] In this study, gas chromatography was used. First, pure fluorosulfonamide and fluorocarboxylic acid ester solvents were dissolved in diethylene glycol dimethyl ether solvent for chromatographic analysis. The solvent components were qualitatively analyzed based on the peak elution time. Simultaneously, a standard curve was plotted based on the linear relationship between peak area and mass in gas chromatography. The target electrolyte was dissolved in diethylene glycol dimethyl ether solvent, and the solvent type and mass were determined based on the peak area and elution time. Similar to the principle of gas chromatography, ion chromatography was also used to determine the type and mass of the lithium salt. Based on the gas chromatography and ion chromatography methods, the structure of the fluorosulfonamide solvent in the electrolyte, the mass ratio of the electrolyte lithium salt to the fluorosulfonamide solvent (M1), the concentration of the electrolyte salt (M2), and the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent (M3) were confirmed. See Table 1 for details.

[0218] Please refer to Table 1 for a list of fluorosulfonamide solvents. The preparation method for 2,2,2-trifluoro-N,N-dimethylethanesulfonamide (DMTESA) is as follows:

[0219]

[0220] A solution of dimethylamine in tetrahydrofuran (60.3 mL, dimethylamine 0.121 mol), triethylamine (Et3N, 12.19 g, 0.121 mol), and 120 mL of anhydrous dichloromethane (DCM) were added to a 500 mL three-necked flask. The mixture was cooled to 10 °C, and 2,2,2-trifluoroethylsulfonyl chloride (20.0 g, 0.11 mol) was added dropwise to anhydrous dichloromethane (20 mL of anhydrous dichloromethane). After the addition was complete, the mixture was stirred at room temperature for 18 h. Once the reaction was complete, the reaction solution was quenched dropwise in ice water, extracted with dichloromethane, concentrated under reduced pressure to remove the organic solvent, and finally distilled under reduced pressure to obtain 15.84 g of compound N,N-dimethyl-2,2,2-trifluoroethylsulfonamide, yield: 75.63%. The yield was calculated as follows:

[0221] Yield = m1 / m2 × 100%

[0222] m1 represents the actual number of moles of N,N-dimethyl-2,2,2-trifluoroethylsulfonamide obtained, and m2 represents the theoretically obtainable number of moles of N,N-dimethyl-2,2,2-trifluoroethylsulfonamide.

[0223] The prepared N,N-dimethyl-2,2,2-trifluoroethylsulfonamide was subjected to 1H NMR, 1C NMR, fluorine NMR, and mass spectrometry tests, and the results are as follows.

[0224] 1H NMR spectrum: 1 HNMR (CDCl3, 400MHz), δ (ppm): 3.93 (s, 2H), 2.68 (s, 6H).

[0225] Carbon spectrum: 13 CNMR (CDCl3, 100MHz), δ (ppm): 102.6, 61.9, 33.1.

[0226] Fluorine spectrum: 19 FNMR (CDCl3, 376MHz), δ (ppm): -77.3.

[0227] Mass spectrometry results: found: 191.0221. Exact Mass, calcd: 191.0228.

[0228] (2) Preparation of negative electrode sheet

[0229] Cut 12μm copper foil into rectangles of 41mm×51mm to be used as negative electrode sheets.

[0230] (3) Preparation of positive electrode sheet

[0231] Cathode preparation: The cathode active material is lithium nickel cobalt manganese oxide (LiNiO). 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder PVDF are mixed at a mass ratio of 98:1:1, and solvent NMP is added and stirred until the system is homogeneous to obtain a positive electrode slurry with a solid content of 80%.

[0232] The positive electrode slurry was uniformly coated on both sides of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. The positive electrode slurry loading on the current collector aluminum foil was 25 mg / cm³. 2 After air-drying at room temperature, transfer to an oven to continue drying, and then cut into 40mm×50mm rectangles to serve as positive electrode sheets.

[0233] (4) Separation membrane: Polyethylene porous membrane is selected and cut into rectangles of 45mm×55mm for later use.

[0234] (5) Assembly of lithium metal secondary battery: Take a cut positive electrode sheet and a cut negative electrode sheet and match them. Use the above-mentioned separator to isolate the positive and negative electrodes in the middle and wrap them in an aluminum-plastic film bag to form a stacked dry cell. Inject 0.3g of the prepared electrolyte, vacuum heat-press the aluminum-plastic film bag and let it stand at room temperature for 6 hours to obtain a lithium metal secondary battery with a rated capacity of 140mAh.

[0235] S2, Performance testing of lithium metal secondary batteries:

[0236] (1) Cyclic performance test

[0237] Take the prepared lithium metal secondary battery and set the ambient temperature to 25℃. Perform charge-discharge cycles at a rate of 0.2C (28mA) and 1C (140mA), with the cutoff voltages for charging and discharging set at 4.3V and 2.8V respectively. The charging process uses a constant current-constant voltage charging method: after reaching the cutoff voltage of 4.3V with 0.2C constant current charging, continue charging at 4.3V constant voltage until the current decays to 0.1C (14mA). When the discharge capacity decays to 80% of the first cycle's discharge capacity, the battery life is considered to have ended, and the cycle number Cy1@1C is recorded.

[0238] (2) Ratio Performance Test

[0239] Take the prepared lithium metal secondary battery and set the test environment temperature to 25℃. The charging rate remains at 0.2C (28mA), and the discharging rate is 4C (560mA). Perform charge-discharge cycles. The cutoff voltages for charging and discharging are set to 4.3V and 2.8V, respectively. A constant current-constant voltage charging method is used during the charging process: after the 0.2C constant current charging reaches the cutoff voltage of 4.3V, switch to 4.3V constant voltage charging until the current decays to 0.1C (14mA). When the discharge capacity decays to 80% of the first cycle's discharge capacity, record the cycle number Cy@4C.

[0240] (3) Coulomb efficiency test

[0241] Take the prepared lithium metal secondary battery and set the test environment temperature to 25℃. Perform a cyclic test according to the cyclic test steps in (1) above. The discharge capacity of each cycle is marked as Ci, and the first cycle charge capacity is marked as Cact,1. This value represents the initial total amount of active lithium. When the discharge capacity decays to 80% of the first cycle discharge capacity, the test is stopped. Record the discharge capacity of the last cycle. Then, continue to perform a deep discharge test with gradually decreasing discharge current using C / 10 (7mA), C / 20 (3.5mA) and 1mA. Record the capacity of deep discharge. The total amount of active lithium when the battery fails is the sum of the last cycle discharge capacity and the deep discharge capacity, marked as Cact,n.

[0242] Average coulombic efficiency (CE) of lithium metal secondary batteries ave The calculation formula is as follows:

[0243]

[0244] (4) Ionic conductivity test

[0245] Take 15 ml of the prepared electrolyte, set the test environment temperature to 25℃, and use a Mettler Toledo conductivity meter to test the electrolyte. The ionic conductivity of the electrolyte can be obtained by directly reading the value.

[0246] Please see Table 1 for the specific results.

[0247] Examples 2-9

[0248] Examples 2 to 9 are basically the same as Example 1, except that in step (1) the amount of lithium difluorosulfonylimide added is adjusted in the preparation of the electrolyte so that M1 and M2 are different from those in Example 1.

[0249] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0250] Examples 10-15

[0251] Examples 10-15 are basically the same as Example 1, except that in step (1) preparation of electrolyte, the volume ratio M3 of fluorinated sulfonamide solvent and fluorinated carboxylic acid ester solvent is different from that in Example 1.

[0252] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0253] Examples 16-19

[0254] Examples 16-19 are basically the same as Example 1, except that in step (1) the preparation of electrolyte, the type of electrolyte salt is changed to be different from that in Example 1.

[0255] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0256] Examples 20-24

[0257] Examples 20-24 are basically the same as Example 1, except that the type of fluorinated carboxylic acid ester solvent used in step (1) preparation of the electrolyte is different from that in Example 1.

[0258] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0259] Example 25

[0260] Example 25 is basically the same as Example 1, except that: in step (1) the preparation of electrolyte, no fluorinated carboxylic acid ester solvent is added.

[0261] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0262] Example 26

[0263] Example 26 is basically the same as Example 1, except that in step (1) of preparing the electrolyte, the fluorinated carboxylic acid ester solvent is replaced with an equal volume of ethylene carbonate. In this case, M3 represents the volume ratio of the fluorinated sulfonamide solvent to the ethylene carbonate.

[0264] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0265] Examples 27-31

[0266] Examples 27-31 are basically the same as Example 1, except that the type of fluorosulfonamide solvent used in step (1) of electrolyte preparation is different from that in Example 1.

[0267] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0268] Comparative Example 1

[0269] Comparative Example 1 is basically the same as Example 1, except that: in step (1) the preparation of the electrolyte, no fluorosulfonamide solvent is added.

[0270] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0271] Comparative Example 2

[0272] Comparative Example 2 is basically the same as Example 1, except that in step (1) preparation of electrolyte, the fluorosulfonamide solvent is replaced with an equal volume of 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide (denoted as 2a).

[0273] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0274] The structures of the fluorosulfonamide solvents used in the various embodiments and comparative examples are shown below:

[0275]

[0276] The relevant parameters and test results of each embodiment and comparative example are shown in Table 1. The mass ratio of the electrolyte lithium salt to the fluorosulfonamide solvent is M1, the concentration of the electrolyte salt is M2, and the volume ratio of the fluorosulfonamide solvent to the fluorocarboxylic acid ester solvent is M3.

[0277] Table 1

[0278]

[0279]

[0280] In this context, " / " indicates that the substance or parameter does not exist, or the performance is too poor to be tested properly and obtain accurate test results.

[0281] Analysis of the data in Table 1 and comparison of the test results of Example 1 and Comparative Examples 1-2 show that the electrolyte of this application has both good anion coordination properties and good ionic conductivity. When applied to the preparation of secondary batteries, it can simultaneously improve the rate performance and cycle performance of the battery.

[0282] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0283] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. An electrolyte, characterized by, The electrolyte includes an electrolyte salt and a fluorine-containing sulfonamide solvent including a compound represented by Formula (1): ， T1 is selected from any one of Formula (1-2) to Formula (1-3): ， T2 is a chain alkyl group having 1 to 4 carbon atoms substituted with fluorine; * represents a connection site.

2. The electrolyte of claim 1, wherein The structure of T2 is shown in (A): ， R3 is selected from H, F, a chain alkyl group having 1 to 3 carbon atoms, or a chain alkyl group having 1 to 3 carbon atoms substituted with fluorine, R4 and R5 are each independently selected from H or F, and at least one of R4 and R5 is F.

3. The electrolyte of claim 2, wherein R3 is selected from H or F.

4. The electrolyte of claim 1, wherein The fluorine-containing sulfonamide solvent includes at least one of compounds represented by Formula (1m) to Formula (1r): 。 5. The electrolyte according to any one of claims 1 to 4, wherein The electrolyte further includes a fluorine-containing carboxylic acid ester solvent.

6. The electrolyte of claim 5, wherein The fluorine-containing carboxylic acid ester solvent has a structure represented by Formula (B): ， R6 and R7 are each independently selected from any one of a chain alkyl group having 1 to 5 carbon atoms, a chain alkyl group having 1 to 5 carbon atoms substituted with fluorine, a cycloalkyl group having 3 to 6 carbon atoms, and a cycloalkyl group having 3 to 6 carbon atoms substituted with fluorine, and at least one of R6 and R7 is selected from a chain alkyl group having 1 to 5 carbon atoms substituted with fluorine or a cycloalkyl group having 3 to 6 carbon atoms substituted with fluorine.

7. The electrolyte of claim 6, wherein R6 and R7 are each independently selected from a chain alkyl group having 1 to 5 carbon atoms or a chain alkyl group having 1 to 5 carbon atoms substituted with fluorine, and at least one of R6 and R7 is a chain alkyl group having 1 to 5 carbon atoms substituted with fluorine.

8. The electrolyte of claim 5, wherein The fluorine-containing carboxylic acid ester solvent includes at least one of ethyl 2,2,2-trifluoroacetate, propyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, methyl difluoroacetate, ethyl 3,3,3-trifluoropropionate, and ethyl 3,3-trifluoropropionate.

9. The electrolyte of claim 5, wherein The volume ratio of the fluorine-containing sulfonamide solvent to the fluorine-containing carboxylic acid ester solvent is (0.2 to 5):

1.

10. The electrolyte of claim 9, wherein The volume ratio of the fluorine-containing sulfonamide solvent to the fluorine-containing carboxylic acid ester solvent is (0.5 to 3):

1.

11. The electrolyte of claim 10, wherein The volume ratio of the fluorine-containing sulfonamide solvent to the fluorine-containing carboxylic acid ester solvent is (1.5 to 2.25):

1.

12. The electrolyte according to any one of claims 1 to 4, wherein In the electrolyte, the mass ratio of the electrolyte salt to the fluorine-containing sulfonamide solvent is (0.068 to 0.68):

1.

13. The electrolyte according to any one of claims 1 to 4, wherein The electrolyte satisfies at least one of the following (a) to (b): (a) In the electrolyte, the concentration of the electrolyte salt is 0.5 mol / L to 5 mol / L; (b) The electrolyte salt includes a lithium ion electrolyte salt.

14. The electrolyte of claim 13, wherein, The lithium ion electrolyte salt includes at least one of lithium bisfluorosulfonimide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bistrifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bisoxalato borate, lithium difluorooxalato borate, lithium difluorobisoxalato phosphate, and lithium tetrafluorooxalato phosphate.

15. A secondary battery characterized by comprising: The secondary battery includes the electrolyte according to any one of claims 1 to 14.

16. The secondary battery according to claim 15, wherein The secondary battery includes a lithium metal secondary battery.

17. An electrical device, comprising: The electric device includes the secondary battery according to any one of claims 15 to 16.

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