Electrolyte, secondary battery, and electric device

Abstract

The invention relates to an electrolyte, a secondary battery and a power utilization device, the electrolyte comprises an electrolyte salt and a fluorine-containing sulfonamide solvent, and the fluorine-containing sulfonamide solvent comprises a compound represented by a formula (1), t1 is selected from any one of the following formulas (1-1)-(1-3): R1 and R2 are respectively and independently selected from any one of alkyl, phenyl and sulfuryl with the carbon atom number of 1-3; t2 is a chain alkyl group which is substituted by fluorine and has 1-4 carbon atoms; * represents a connection site.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrolyte, a secondary battery and an electrical device. Background Art

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

[0003] In order to meet the demand for higher energy density of batteries in application fields such as long-range electric vehicles and electric aircraft, metal lithium secondary batteries with higher energy density have been developed, which have broad application prospects in the fields of long-range power batteries, electric aircraft and electric aircraft. However, the performance improvement of lithium metal batteries is severely restricted by the electrolyte. Traditional electrolytes are easy to decompose 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, it is easy to cause safety accidents.

[0004] Therefore, the traditional technology needs to be further improved. Summary of the invention

[0005] Based on this, 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] The present application is implemented through the following technical solutions.

[0007] In a first aspect of the present application, an electrolyte is provided, wherein the components of the electrolyte include an electrolyte salt and a fluorinated sulfonamide solvent, wherein the fluorinated sulfonamide solvent includes a compound represented by formula (1):

[0008]

[0009] Wherein, T1 is selected from any one of the following formulas (1-1) to (1-3):

[0010]

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

[0012] T2 is a fluorine-substituted alkyl group having 1 to 4 carbon atoms;

[0013] * represents the ligation site.

[0014] The above electrolyte contains a fluorinated sulfonamide solvent of a specific structure, wherein the compound represented by formula (1) contains a sulfonamide group, and one side of the sulfonamide group is connected to a fluorinated alkyl group with 1 to 4 carbon atoms having a strong electron-withdrawing property, and the sulfonamide group and the fluorinated alkyl group with 1 to 4 carbon atoms are not directly connected, but are separated by a carbon atom; thus, on the one hand, a group having a stronger electron-withdrawing property than the sulfonyl functional group is introduced on one side of the sulfonamide group to reduce the coordination ability of the sulfonyl functional group in the compound represented by formula (1) with lithium ions, so that the coordination ability of the fluorinated sulfonamide solvent as a whole with lithium ions is weaker than the coordination ability of the anions in the inner layer solvent sheath structure of lithium ions. In other words, the coordination number of the anions is substantially increased, making it easier to obtain electrons for reduction and decomposition, thereby forming a dense interface film mainly composed of inorganic substances, which has a lower diffusion energy barrier and a faster transmission rate. On the other hand, the sulfonamide group and the group with strong electron-withdrawing property are separated by one carbon atom, so that the β-carbon atom connected to the sulfonamide group or the carbon atom farther from the sulfonamide group than the β-carbon atom is replaced by fluorine, so that the electron-withdrawing ability of the sulfonyl functional group in the compound represented by formula (1) and the electron-withdrawing ability of the group part to which it is connected maintain an appropriate gap, so that the sulfonyl functional group still has a certain ability to coordinate with lithium ions, so that the compound represented by formula (1) still has a high donor number, improves its solubility for electrolyte lithium salt, and makes the electrolyte have both good anion coordination performance and good ion conductivity. When used in the preparation of secondary batteries, it can simultaneously improve the rate performance and cycle performance of the battery.

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

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

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

[0018]

[0019] 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 by fluorine, R4 and R5 are independently selected from H or F, and at least one of R4 and R5 is F.

[0020] That is, at least one hydrogen on the β-carbon atom connected to the sulfonamide group is replaced by fluorine, so that the coordination ability of the fluorinated sulfonamide solvent and the coordination ability of the anion are better balanced, further improving the anion coordination performance and good ionic conductivity of the electrolyte.

[0021] Further research also shows that compared with the fluorinated sulfonamide solvent formed by regulating the carbon atoms farther away from the sulfonamide group than the β-carbon atom by fluorine, regulating the replacement of at least one hydrogen on the β-carbon atom connected to the sulfonamide group by fluorine can improve the solubility of the fluorinated sulfonamide solvent for the electrolyte salt on the basis of increasing the coordination number of the anion, 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 embodiments, T1 is selected from formula (1-1), and R1 and R2 are independently selected from an alkyl group having 1 to 3 carbon atoms or a phenyl group.

[0024] When T1 is selected from formula (1-1), its specific structure can enhance the compatibility of the fluorinated sulfonamide solvent with the lithium metal negative electrode, effectively reduce the side reaction of the electrolyte at the lithium metal negative electrode, and further improve the cycle performance of the battery.

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

[0026] The study found that when R1 and R2 are selected from chain 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 fluorinated sulfonamide solvent comprises at least one of the compounds represented by formula (1a) to formula (1r):

[0028]

[0029] In some of these embodiments, the components of the electrolyte further include a fluorinated carboxylic acid ester solvent;

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

[0031]

[0032] wherein R6 and R7 are 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 by fluorine, a cycloalkyl group having 3 to 6 carbon atoms, and a cycloalkyl group having 3 to 6 carbon atoms substituted by fluorine, and at least one of R6 and R7 is selected from a chain alkyl group having 1 to 5 carbon atoms substituted by fluorine or a cycloalkyl group having 3 to 6 carbon atoms substituted by fluorine;

[0033] More optionally, R6 and R7 are independently selected from chain alkyl groups having 1 to 5 carbon atoms or chain alkyl groups having 1 to 5 carbon atoms substituted by fluorine, and at least one of R6 and R7 is a chain alkyl group having 1 to 5 carbon atoms substituted by fluorine.

[0034] Fluorinated carboxylic acid ester solvents can further enhance the coordination ability between anions and lithium ions, increase the proportion of the coordination number of anions in the bulk electrolyte, which is beneficial to improving the interface properties of the negative electrode, and can enhance the wettability of the electrolyte to the diaphragm. Together with the above-mentioned fluorinated sulfonamide solvents of specific structure, the cycle performance of the secondary battery can be further enhanced.

[0035] In some embodiments, 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.

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

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

[0038] Further optionally, the volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent is (1.5-2.25):1.

[0039] By adjusting the volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent, a better balance can be achieved between the coordination ability of the fluorinated sulfonamide 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 of the embodiments, in the electrolyte, the mass ratio of the electrolyte salt to the fluorinated sulfonamide solvent 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 comprises a lithium ion electrolyte salt;

[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 bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate) and lithium tetrafluorooxalatophosphate.

[0045] According to a second aspect of the present application, a secondary battery is provided, wherein the secondary battery comprises the electrolyte according to the first aspect.

[0046] In some embodiments, the secondary battery comprises a lithium metal secondary battery.

[0047] The above secondary battery has excellent cycle performance.

[0048] According to a third aspect of the present application, there is provided an electric device, wherein the electric device comprises the secondary battery according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

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

[0051] Figure 2 yes Figure 1 Exploded diagram of

[0052] Figure 3 is a schematic diagram of an embodiment of a battery pack;

[0053] Figure 4 yes Figure 3 Exploded diagram of

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

[0055] Description of reference numerals:

[0056] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery cell; 41. Shell; 42. Electrode assembly; 43. Cover plate; 5. Electrical device. DETAILED DESCRIPTION

[0057] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0059] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0060] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0061] In the present application, the term "alkyl" refers to a group formed when an alkane loses a hydrogen, such as methane losing a hydrogen to form a methyl group. The term "chain alkyl" refers to a group formed when an alkane loses a hydrogen, wherein the carbon atoms are all connected by carbon-carbon single bonds and do not form a ring, and the remaining valence bonds are all bonded to hydrogen, and includes straight-chain alkane groups and branched-chain alkane groups.

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

[0063] To sum up the background, the performance improvement of traditional secondary batteries, especially lithium metal secondary batteries, is severely restricted by the electrolyte. The solvents in traditional electrolytes are mainly ester solvents: carbonates or carboxylates.

[0064] Studies have found that when fluorinated sulfonamide compounds are used as additives to electrolytes, they can improve the electrolyte's high-voltage resistance and high-temperature storage performance.

[0065] However, further studies have shown that when fluorine-containing sulfonamide compounds are used as solvents for electrolytes, the substitution position of fluorine atoms has a great technical connection with the anion coordination ability and ion conductivity of the electrolyte.

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

[0067] In one embodiment of the present application, an electrolyte is provided, wherein the components of the electrolyte include an electrolyte salt and a fluorinated sulfonamide solvent, wherein the fluorinated sulfonamide solvent includes a compound represented by formula (1):

[0068]

[0069] Wherein, T1 is selected from any one of the following formulas (1-1) to (1-3):

[0070]

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

[0072] T2 is a fluorine-substituted alkyl group having 1 to 4 carbon atoms;

[0073] * represents the ligation site.

[0074] The above electrolyte contains a fluorinated sulfonamide solvent of a specific structure, wherein the compound represented by formula (1) contains a sulfonamide group, and one side of the sulfonamide group is connected to a fluorinated alkyl group with 1 to 4 carbon atoms having a strong electron-withdrawing property, and the sulfonamide group and the fluorinated alkyl group with 1 to 4 carbon atoms are not directly connected, but are separated by a carbon atom; thus, on the one hand, a group having a stronger electron-withdrawing property than the sulfonyl functional group is introduced on one side of the sulfonamide group to reduce the coordination ability of the sulfonyl functional group in the compound represented by formula (1) with lithium ions, so that the coordination ability of the fluorinated sulfonamide solvent as a whole with lithium ions is weaker than the coordination ability of the anions in the inner layer solvent sheath structure of lithium ions. In other words, the coordination number of the anions is substantially increased, making it easier to obtain electrons for reduction and decomposition, thereby forming a dense interface film mainly composed of inorganic substances, which has a lower diffusion energy barrier and a faster transmission rate. On the other hand, the sulfonamide group and the group with strong electron-withdrawing property are separated by one carbon atom, so that the β-carbon atom connected to the sulfonamide group or the carbon atom farther from the sulfonamide group than the β-carbon atom is replaced by fluorine, so that the electron-withdrawing ability of the sulfonyl functional group in the compound represented by formula (1) and the electron-withdrawing ability of the group part to which it is connected maintain an appropriate gap, so that the sulfonyl functional group still has a certain ability to coordinate with lithium ions, so that the compound represented by formula (1) still has a high donor number, improves its solubility for electrolyte lithium salt, and makes the electrolyte have both good anion coordination performance and good ion conductivity. When used in the preparation of secondary batteries, it can simultaneously improve the rate performance and cycle performance of the battery.

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

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

[0077] In some embodiments, R3 is selected from H, F, a linear alkyl group having 1 to 3 carbon atoms, or a linear alkyl group having 1 to 3 carbon atoms substituted by fluorine.

[0078] In some embodiments, R3 is selected from H, F, a linear alkyl group having 1 to 2 carbon atoms, or a linear alkyl group having 1 to 2 carbon atoms substituted by fluorine.

[0079] In some 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 embodiments, T1 is selected from formula (1-1).

[0082] In some embodiments, R1 and R2 are independently selected from an alkyl group having 1 to 3 carbon atoms or a phenyl group.

[0083] When T1 is selected from formula (1-1), its specific structure can enhance the compatibility of the fluorinated sulfonamide solvent with the lithium metal negative electrode, effectively reduce the side reaction of the electrolyte at the lithium metal negative electrode, and further improve the cycle performance of the battery.

[0084] In some embodiments, R1 and R2 are independently selected from a chain alkyl group having 1 to 3 carbon atoms or a phenyl group.

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

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

[0087] The study found that when R1 and R2 are selected from chain 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 radicals having 1 to 3 carbon atoms.

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

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

[0091] In some embodiments, the fluorinated sulfonamide solvent comprises at least one of the compounds represented by formula (1a) to formula (1r):

[0092]

[0093]

[0094] The compound represented by the above formula (1) can be purchased from commercial channels or synthesized by the following preparation method:

[0095] The compound of formula (A) is subjected to a substitution reaction with the compound of formula (B) to prepare a compound of formula (1); wherein the compound of formula (B) includes at least one of the compounds of formula (B-1) to formula (B-3).

[0096]

[0097] Among them, the selection of T2, R1 and R2 is the same as above and will not be repeated here.

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

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

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

[0101] In some 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 embodiments, the molar ratio of the compound of formula (A) to the compound of formula (B) is 1:(1-3).

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

[0104] In some of the embodiments, in the substitution reaction, the compound of formula (A) is firstly added dropwise into a solution containing the compound of formula (B) at 5°C to 10°C, and then reacted at room temperature for 10h to 20h.

[0105] The room temperature may be 20°C to 35°C.

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

[0107] The product after the substitution reaction is extracted with an extractant, then concentrated to remove the extractant, and then distilled under reduced pressure to obtain a purified compound represented by formula (1).

[0108] In some embodiments, the extractant comprises dichloromethane.

[0109] The 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 further comprises a fluorine-containing carboxylic acid ester solvent.

[0111] The study found that the fluorinated carboxylic acid ester solvent can cooperate with the compound represented by the above formula (1) to further improve the coordination ability of anions and lithium ions, increase the proportion of the coordination number of anions in the bulk electrolyte, which is beneficial to improve the interface properties of the negative electrode and can improve the wettability of the electrolyte to the diaphragm. The fluorinated sulfonamide solvent with the above specific structure can further improve the cycle performance of the secondary battery.

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

[0113]

[0114] Among them, R6 and R7 are independently selected from any one of a chain alkyl group with 1 to 5 carbon atoms, a chain alkyl group with 1 to 5 carbon atoms substituted by fluorine, a cycloalkyl group with 3 to 6 carbon atoms and a cycloalkyl group with 3 to 6 carbon atoms substituted by fluorine, and at least one of R6 and R7 is selected from a chain alkyl group with 1 to 5 carbon atoms substituted by fluorine or a cycloalkyl group with 3 to 6 carbon atoms substituted by fluorine.

[0115] In some embodiments, R6 and R7 are independently selected from chain alkyl groups with 1 to 5 carbon atoms or chain alkyl groups with 1 to 5 carbon atoms substituted by fluorine, and at least one of R6 and R7 is a chain alkyl group with 1 to 5 carbon atoms substituted by fluorine.

[0116] In some embodiments, R6 and R7 are independently selected from chain alkyl groups with 1 to 3 carbon atoms or chain alkyl groups with 1 to 3 carbon atoms substituted by fluorine, and at least one of R6 and R7 is chain alkyl groups with 1 to 3 carbon atoms substituted by fluorine.

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

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

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

[0120] In some embodiments, 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.

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

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

[0123] In some of the embodiments, the volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent is (1.5-2.25):1.

[0124] By adjusting the volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent, a better balance can be achieved between the coordination ability of the fluorinated sulfonamide 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 values ​​include the minimum and maximum values ​​of the range, and 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 a range consisting of any two numerical values, for example, it can be (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 of the embodiments, in the electrolyte, the mass ratio of the electrolyte salt to the fluorinated sulfonamide solvent is (0.068-0.68):1.

[0127] In the above “(0.068~0.68):1”, the values ​​include the minimum and maximum values ​​of the range, and 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 ​​consisting of 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 of the embodiments, in the electrolyte solution, the concentration of the electrolyte salt is 0.5 mol / L to 5 mol / L.

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

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

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

[0132] The concentration of the electrolyte salt is adjusted to take into account both higher ionic conductivity and lower viscosity, further improving the positive effect of the electrolyte on the stability of the positive and negative electrodes. In some embodiments, the electrolyte salt can be selected from electrolyte salts commonly used in the art, such as at least one of a lithium ion electrolyte salt, a sodium ion electrolyte salt, and a potassium ion electrolyte salt.

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

[0134] As an example, the lithium ion electrolyte salt includes, but is not limited to, one or more of 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 difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0135] The study found that the above electrolyte has good solubility for the above lithium ion electrolyte salt; further, compared with other types of lithium ion electrolyte salts, its solubility for LiNO3 is slightly worse.

[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 bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate) and lithium tetrafluorooxalatophosphate.

[0137] According to one embodiment of the present application, a secondary battery is provided. The secondary battery includes the electrolyte according to the first aspect.

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

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

[0140] The components of the positive electrode active layer include positive electrode active materials. The positive electrode active materials can be selected from the positive electrode active materials commonly used 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 material of a lithium ion battery, the positive electrode active material of a sodium ion battery and the positive electrode active material of a potassium ion battery are hereinafter referred to as lithium ion active material, sodium ion active material and potassium ion active material, respectively.

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

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

[0144] It should be noted that the lithium content in the positive electrode material exemplified above refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charging and discharging process, that is, the molar subscript of Li in the positive electrode active material in 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 expressed as Li y Fe x Mn (1-x) PO4, y is 0~1.1.

[0146] For example, for the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x , y is 0.2~1.2, 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] The battery will be accompanied by Li deintercalation and consumption during the charge and discharge process. The molar content of Li is different when the battery is discharged to different states. The above definition of y includes the molar content of Li under different charge and discharge states of the battery; further, the battery voltage is usually between 2-5V.

[0148] As an example, the sodium ion active material may include at least one of the following materials: at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present 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 of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. The sodium transition metal oxide is, for example, 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 of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) 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- valence state.

[0151] Polyanionic compounds can also be those with sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal includes 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, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

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

[0153] Polyanionic compounds include 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 .

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

[0155] Prussian blue compounds can be compounds containing sodium ions, transition metal ions and cyanide ions (CN-). The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, 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 the present application, in the positive electrode active layer, the mass proportion of the positive electrode active material is 70% to 99.8%.

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

[0158] Taking the above electrode sheet as the positive electrode as an example, the conductive agent can be a conductive agent commonly used 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 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 binder of the binder can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-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 fluorine-containing acrylate resin.

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

[0161] Optionally, in the positive electrode active layer, the mass proportion of the binder is 1% to 10%.

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

[0163] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. 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 metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0165] In some of the 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 the present application, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on the current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained. The positive electrode slurry has a solid content of 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s. The positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet.

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

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

[0169] The surface 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 sheet: The negative electrode sheet 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 a negative electrode active material.

[0172] The negative electrode active material mentioned above can adopt the commonly used negative electrode active materials in this application.

[0173] In any embodiment of the present application, the above-mentioned 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, metallic lithium, lithium metal and other metal or non-metallic elements; further, 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); non-metallic elements 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 mesophase carbon microbeads, 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 the present application, the battery is a lithium battery, and the mass proportion of the negative electrode active material in the negative electrode active layer is 70% to 100%.

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

[0177] In any embodiment of the present application, the above-mentioned negative electrode conductive agent can be a conductive material commonly used 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 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] The weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.

[0179] The above-mentioned 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), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0180] The weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.

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

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

[0183] The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate.

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

[0185] In some of the 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 the present application, the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000mPa·s to 10000mPa·s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing such as a roller, a negative electrode sheet is obtained.

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

[0188] The surface 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 of the embodiments, the secondary battery is a "lithium metal secondary battery", and 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 assembled battery is 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, thereby obtaining a true negative electrode; or a lithium-containing metal sheet is directly used as the negative electrode.

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

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

[0192] In some of the embodiments, the non-metallic 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 isolation membrane of the present application can be any known porous structure isolation membrane with good chemical stability and mechanical stability.

[0195] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane 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 within a range of 2 μm to 15 μm; optionally, the thickness of the diaphragm is controlled within a range of 2 μm to 13 μm.

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

[0198] In some embodiments, reference Figure 2 The housing may include a shell 41 and a cover plate 43. The shell 41 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 41 has an opening connected to the receiving cavity, and the cover plate 43 can be covered on the opening to close the receiving cavity.

[0199] The positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly 42. The electrode assembly 42 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 42. The number of electrode assemblies 42 contained in the battery cell 4 can be one or more, which can be adjusted according to needs.

[0200] The secondary battery includes one or more battery cells 4 .

[0201] The secondary battery may be a battery module or a battery pack; the battery module or battery pack includes at least one battery cell. The number of battery cells contained in the battery module may be one or more, and those skilled in the art may select an appropriate number according to the application and capacity of the battery module.

[0202] Figure 3 and Figure 4 The battery pack 1 is used as an example. 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 body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for the battery cells 4.

[0203] The plurality of battery cells 4 may be arranged in the battery box in any manner.

[0204] The present application also provides an electrical device, which includes the secondary battery mentioned above.

[0205] Furthermore, in the above-mentioned electrical device, the secondary battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0206] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device, and can also be used as an energy storage unit for an electrical device.

[0207] The above-mentioned electrical devices may be, but are not limited to, mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.

[0208] Mobile devices include but are not limited to: mobile phones, laptops, etc. 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 The power consumption device 5 is taken as an example. The power consumption device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device 5's requirements for high power and high energy density of the secondary battery, a battery pack can be used.

[0210] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and a secondary battery may be used as a power source.

[0211] The present invention will be described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present invention. Under the guidance of the concept of the present invention, those skilled in the art should realize that certain 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 embodiments.

[0213] Example 1

[0214] S1. Preparation of lithium metal secondary batteries

[0215] (1) Preparation of electrolyte:

[0216] The fluorinated carboxylate amine solvent 3,3,3-trifluoropropionic acid ethyl ester (FEP) and the fluorosulfonamide solvent 2,2,2-trifluoro-N,N-dimethylethanesulfonamide (DMTESA) in a volume ratio of 1:2 were fully mixed to form a mixed solvent, and then 1.87 g of bis(fluorosulfonyl)imide lithium salt was added to 5 mL of the mixed solvent and stirred thoroughly to obtain an electrolyte for standby use.

[0217] Among them, gas chromatography test is adopted. First, pure fluorosulfonamide and fluorocarboxylic acid ester solvents are dissolved in diethylene glycol dimethyl ether solvent respectively, and chromatographic test is carried out, and the solvent components are qualitatively analyzed according to the peak time. At the same time, a standard curve is drawn according to the linear relationship between the peak area and the mass of the gas chromatography; the target electrolyte is dissolved in diethylene glycol dimethyl ether solvent, and the solvent type and the solvent quality can be determined based on the peak area and the peak time; similar to the test principle of gas chromatography, the type and quality of lithium salt can also be obtained by using the ion chromatography test method. According to the gas phase and ion chromatography test methods, the structure of the fluorosulfonamide solvent contained in the electrolyte, the mass ratio of the electrolyte lithium salt to the fluorosulfonamide solvent 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. Please see Table 1 for details.

[0218] The types of fluorinated sulfonamide solvents are shown in Table 1. Among them, the preparation method of 2,2,2-trifluoro-N,N-dimethylethanesulfonamide (DMTESA) is as follows:

[0219]

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

[0221] Yield = m1 / m2×100%

[0222] m1 is the mole number of N,N-dimethyl-2,2,2-trifluoroethylsulfonamide actually obtained, and m2 is the mole number of N,N-dimethyl-2,2,2-trifluoroethylsulfonamide theoretically obtainable.

[0223] The prepared N,N-dimethyl-2,2,2-trifluoroethylsulfonamide was subjected to nuclear magnetic hydrogen spectrum test, carbon spectrum test, fluorine spectrum test and mass spectrum test, and the results are as follows.

[0224] H 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] The 12 μm copper foil was cut into a 41 mm × 51 mm rectangle for use as the negative electrode.

[0230] (3) Preparation of positive electrode sheet

[0231] Positive electrode preparation: The positive electrode active material lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder PVDF were mixed in a mass ratio of 98:1:1, and solvent NMP was added and stirred until the system became uniform to obtain a positive electrode slurry with a solid content of 80%;

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

[0233] (4) Isolation film: Use a polyethylene porous film and cut it into a 45 mm × 55 mm rectangle 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 isolation film to isolate the positive and negative electrodes in the middle, and wrap them in an aluminum-plastic film bag to form a stacked dry battery cell, inject 0.3g of the above-mentioned prepared electrolyte, and vacuum hot-press the aluminum-plastic film bag. After standing at room temperature for 6 hours, a lithium metal secondary battery with a rated capacity of 140mAh is obtained.

[0235] S2. Performance test of lithium metal secondary battery:

[0236] (1) Cyclic performance test

[0237] Take the lithium metal secondary battery prepared above, set the ambient temperature to 25°C, use 0.2C (i.e. 28mA) charging, 1C discharge (i.e. 140mA) rate to perform charge and discharge cycles, the charge and discharge cut-off voltages are set to 4.3V and 2.8V respectively, and the charging process adopts constant current-constant voltage charging method, specifically: when the 0.2C constant current charging reaches the cut-off voltage of 4.3V, continue to use 4.3V constant voltage charging until the current decays to 0.1C (i.e. 14mA). When the discharge capacity decays to 80% of the first cycle discharge capacity, the battery life is considered to be terminated, and the cycle number Cy1@1C is recorded.

[0238] (2) Rate performance test

[0239] Take the lithium metal secondary battery prepared above, set the test environment temperature to 25°C, use 0.2C (i.e. 28mA) for charging and discharging cycles at a charging rate of 4C (i.e. 560mA). The cut-off voltages for charging and discharging are set to 4.3V and 2.8V, respectively, and the charging process adopts a constant current-constant voltage charging method, specifically: when the 0.2C constant current charging reaches a cut-off voltage of 4.3V, continue to use a 4.3V constant voltage charging until the current decays to 0.1C (i.e. 14mA). When the discharge capacity decays to 80% of the first cycle discharge capacity, record the number of cycles Cy@4C.

[0240] (3) Coulomb efficiency test

[0241] Take the lithium metal secondary battery prepared above, set the test environment temperature to 25°C, and perform a cycle test according to the cycle 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, which represents the initial total amount of active lithium. When the discharge capacity decays to 80% of the first cycle discharge capacity, the discharge capacity of the last cycle is recorded, and the deep discharge test with a gradually reduced discharge current is continued using C / 10 (7mA), C / 20 (3.5mA) and 1mA currents, and the deep discharge capacity is recorded. 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°C, and use a Mettler Toledo conductivity tester to test. The ionic conductivity of the electrolyte can be obtained by direct reading.

[0246] Please see Table 1 for specific results.

[0247] Embodiments 2 to 9

[0248] Examples 2 to 9 are basically the same as Example 1, except that in step (1) of preparing the electrolyte, the amount of bis(fluorosulfonyl)imide lithium salt added is regulated so that M1 and M2 are different from those in Example 1.

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

[0250] Embodiments 10 to 15

[0251] Examples 10 to 15 are substantially the same as Example 1, except that in step (1) of preparing the electrolyte, the volume ratio M3 of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent is adjusted differently from that in Example 1.

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

[0253] Embodiments 16 to 19

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

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

[0256] Embodiments 20 to 24

[0257] Examples 20 to 24 are basically the same as Example 1, except that in step (1) of preparing the electrolyte, the type of fluorinated carboxylic acid ester solvent is controlled differently from that in Example 1.

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

[0259] Embodiment 25

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

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

[0262] Embodiment 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 ethylene carbonate.

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

[0265] Examples 27 to 31

[0266] Examples 27 to 31 are basically the same as Example 1, except that in step (1) the preparation of the electrolyte, the type of fluorinated sulfonamide solvent is regulated differently from that in Example 1.

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

[0268] Comparative Example 1

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

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

[0271] Comparative Example 2

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

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

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

[0275]

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

[0277] Table 1

[0278]

[0279]

[0280] Among them, “ / ” means that the substance does not exist or the parameter or performance is too poor to be tested normally and obtain accurate test results.

[0281] By analyzing the data in Table 1 and comparing the test results of Example 1 and Comparative Examples 1 to 2, it can be seen that the electrolyte of the present application has both good anion coordination performance and good ion conductivity, and when used in 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-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description and drawings can be used to interpret the content of the claims.

Claims

1. An electrolyte, characterized in that: The components of the electrolyte include an electrolyte salt and a fluorinated sulfonamide solvent, wherein the fluorinated sulfonamide solvent includes a compound represented by formula (1): Wherein, T1 is selected from any one of the following formulas (1-1) to (1-3): R1 and R2 are independently selected from any one of an alkyl group having 1 to 3 carbon atoms, a phenyl group and a sulfone group; T2 is a fluorine-substituted alkyl group having 1 to 4 carbon atoms; * represents the ligation site.

2. The electrolyte according to claim 1, characterized in that 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 by fluorine, R4 and R5 are independently selected from H or F, and at least one of R4 and R5 is F.

3. The electrolyte according to claim 2, characterized in that R3 is selected from H or F.

4. The electrolyte according to claim 1, characterized in that T1 is selected from the formula (1-1), and R1 and R2 are each independently selected from an alkyl group having 1 to 3 carbon atoms or a phenyl group.

5. The electrolyte according to claim 1, characterized in that R1 and R2 are both alkyl radicals having 1 to 3 carbon atoms.

6. The electrolyte according to claim 1, characterized in that The fluorinated sulfonamide solvent comprises at least one of the compounds represented by formula (1a) to formula (1r):

7. The electrolyte according to any one of claims 1 to 6, characterized in that The components of the electrolyte also include a fluorine-containing carboxylic acid ester solvent; Optionally, the structure of the fluorinated carboxylic acid ester solvent is as shown in formula (B): wherein R6 and R7 are 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 by fluorine, a cycloalkyl group having 3 to 6 carbon atoms, and a cycloalkyl group having 3 to 6 carbon atoms substituted by fluorine, and at least one of R6 and R7 is selected from a chain alkyl group having 1 to 5 carbon atoms substituted by fluorine or a cycloalkyl group having 3 to 6 carbon atoms substituted by fluorine; More optionally, R6 and R7 are independently selected from chain alkyl groups having 1 to 5 carbon atoms or chain alkyl groups having 1 to 5 carbon atoms substituted by fluorine, and at least one of R6 and R7 is a chain alkyl group having 1 to 5 carbon atoms substituted by fluorine.

8. The electrolyte according to claim 7, characterized in that 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 according to claim 7, characterized in that The volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent is (0.2-5):1; Optionally, the volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent is (0.5-3):1; Further optionally, the volume ratio of the fluorinated sulfonamide solvent to the fluorinated carboxylic acid ester solvent is (1.5-2.25):

1.

10. The electrolyte according to any one of claims 1 to 6, characterized in that In the electrolyte, the mass ratio of the electrolyte salt to the fluorine-containing sulfonamide solvent is (0.068-0.68):

1.

11. The electrolyte according to any one of claims 1 to 6, characterized in that The electrolyte satisfies at least one of the following conditions (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 comprises a lithium ion electrolyte salt; 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 bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate) and lithium tetrafluorooxalatophosphate.

12. A secondary battery, characterized in that: The secondary battery comprises the electrolyte according to any one of claims 1 to 11.

13. The secondary battery according to claim 12, characterized in that: The secondary battery includes a lithium metal secondary battery.

14. An electrical device, characterized in that: The electric device comprises the secondary battery according to any one of claims 12 to 13.

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