Non-aqueous electrolyte solution, secondary battery, and electric device

Abstract

The present application provides a non-aqueous electrolyte solution, a secondary battery, and an electric device. The non-aqueous electrolyte solution comprises additives, wherein the additives comprise a first additive and a second additive, the first additive is any one or more cyclic sulfate compounds having a structure represented by general formula (I), and the second additive comprises one or more of lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, a compound represented by general formula (III), and fluorosulfates.

Description

Non-aqueous electrolyte, secondary battery, and electrical device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a non-aqueous electrolyte, a secondary battery, and an electrical device. Background Art

[0002] In recent years, with the development of lithium-ion secondary battery technology, lithium-ion secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As lithium-ion secondary batteries have achieved such rapid development, higher requirements have been placed on their fast charging performance, cycle performance, and safety performance.

[0003] Battery performance, especially for lithium secondary batteries used in automobiles, requires high output power and long life. Low resistance and improved battery life are also key challenges. One known cause of increased battery resistance and reduced battery life is the continued reduction of the electrolyte at the negative electrode during charging. To overcome these issues, attempts have been made to add various compounds to the electrolyte to form a passivation layer, also known as the SEI film, on the negative electrode surface. The SEI film is a good lithium ion conductor but a poor electron conductor, inhibiting the continued lithium-consuming reaction and thus protecting the electrode. Research has shown that forming a uniform, dense, stable solid electrolyte interphase (SEI) film with low impedance and good adhesion properties is beneficial for improving battery electrochemical performance. However, if the SEI film generated by electrolyte additives is rich in organic components such as alkyl lithium, it can lead to high electrode impedance, deteriorating the power performance of the battery cell. Furthermore, high impedance can lead to lithium deposition at the negative electrode, further deteriorating the battery cell life.

[0004] Summary of the Invention

[0005] The present application provides a non-aqueous electrolyte, a secondary battery and an electrical device to improve the cycle performance of the battery.

[0006] The first aspect of the present application provides a non-aqueous electrolyte, comprising an additive, wherein the additive comprises a first additive and a second additive, the first additive being any one or more cyclic sulfate compounds having a structure represented by general formula (I),

[0007] Among them, R 1 、R 2 、R 3 and R 4Each is independently selected from any one of a group having a structure represented by general formula (II), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and n1 and n2 are each independently any integer from 0 to 2,

[0008] General formula (II) is

[0009] R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and n3 is any integer from 0 to 2;

[0010] The second additive includes one or more of lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, a compound represented by the general formula (III), and a fluorosulfonate.

[0011] In the general formula (III), M is a metal, the metal includes one or more selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu and Ni, Y represents a boron atom or a phosphorus atom, X represents a halogen atom, R represents a C1-C10 alkylene group, a C1-C10 haloalkylene group, a C6-C20 arylene group, or a C6-C20 haloarylene group, and each group representing R is optionally substituted with a substituent or a heteroatom, m represents an integer of 1-3, n represents an integer of 0-4, q represents 0 or 1, and a, b, and c represent natural numbers;

[0012] Fluorosulfonate (FSO3) y M y+ , M y+ is a metal ion or an organic cation; the metal ion includes Li + 、Na + , K + , Rb + 、Cs + Mg 2+ , Ca 2+ 、Ba 2+ 、Al 3+ 、Fe 2+ 、Cu 2+ 、Fe 3+ 、Ni 2+ and Ni 3+ One or more of the groups.

[0013] The cyclic sulfate additive in the non-aqueous electrolyte will form a highly elastic SEI film on the negative electrode side during the first charge process. After further combining with the above-mentioned second additive, inorganic components such as Li2S, ROSO2Li, carbonates, LiF, borates, and phosphates will also be generated on the negative electrode side during the first charge of the secondary battery. Compared with single sulfides, the mixed inorganic components have more stable and higher ion conductivity and electron blocking capabilities. Therefore, the generated SEI film can more effectively block electrons, alleviate the continuous decomposition of the electrolyte at the negative electrode, optimize the cycle and storage performance of the battery cell, and greatly improve the battery cell life.

[0014] In any embodiment of the first aspect, R 1 and R 2 are not hydrogen atoms and R 3 and R 4 Not all hydrogen atoms.

[0015] In any embodiment of the first aspect, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0016] R 1 and R 2 At the same time, it is a hydrogen atom and R 3 and R 4 One is a hydrogen atom and the other is any one of a group having a structure represented by general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and R 5 and R 6 Not all hydrogen atoms.

[0017] In any embodiment of the first aspect, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0018] R 3 and R 4 At the same time, it is a hydrogen atom and R 1 and R 2One is a hydrogen atom and the other is any one of a group having a structure represented by general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and R 5 and R 6 Not all hydrogen atoms.

[0019] The above R 1 、R 2 、R 3 and R 4 There are substituents in the groups. By introducing substituents such as alkyl groups, an elastic SEI film with a longer organic chain can be generated at the negative electrode, which can cope with the volume change of the negative electrode during the cycle and avoid the destruction of the SEI film; the introduction of substituents containing F and N can participate in the film formation at the negative electrode, generating a SEI film rich in more inorganic components such as LiF and Li3N, thereby improving the mechanical strength of the SEI film, and then improving the stability of the negative electrode SEI film, thereby achieving the purpose of further improving the battery cycle performance.

[0020] In any embodiment of the first aspect, the cyclic sulfate compound has a structure represented by general formula (I-1),

[0021] R 1 、R 2 、R 3 and R 4 Each independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group, and a sulfonic acid group;

[0022] General formula (II-1) is

[0023] R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group.

[0024] In any embodiment of the first aspect, R 1 、R 2 、R 3 、R 4 、R 5 and R6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a C1-C3 haloalkoxy group, a C2-C3 alkenyl group, a C1-C3 ester group, a cyano group and a sulfonic acid group.

[0025] In any embodiment of the first aspect, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C3 alkyl group, and a C1-C3 halogenated alkyl group.

[0026] In any embodiment of the first aspect, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 Each independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group and an isopropyl group.

[0027] In any embodiment of the first aspect, the group represented by the general formula (II-1) is selected from any one of the following groups: Wherein, X is a F atom, a Cl atom or a Br atom.

[0028] In any embodiment of the first aspect, R 1 、R 2 、R 3 and R 4 Each independently selected from Any one of a hydrogen atom, a F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group and an isopropyl group, wherein X is a F atom.

[0029] In any embodiment of the first aspect, R 1 、R 2 、R 3 and R 4 Each independently selected from any one of a hydrogen atom, a methyl group and an ethyl group, and X is a F atom.

[0030] In any embodiment of the first aspect, the cyclic sulfate compound is selected from any one or more of the following compounds:

[0031] In any embodiment of the first aspect, in the general formula (III), the metal includes one or more selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu and Ni, Y represents a boron atom or a phosphorus atom, X represents a halogen atom, R is a C1-C10 alkylene group, a C1-C10 haloalkylene group, a C6-C20 arylene group, or a C6-C20 haloarylene group, and each group representing R is optionally substituted with a substituent or a heteroatom, m represents an integer of 1-3, n represents an integer of 0-4, and q represents 0 or 1.

[0032] In any embodiment of the first aspect, the fluorosulfonate includes any one or more of lithium fluorosulfonate, sodium fluorosulfonate, and potassium fluorosulfonate.

[0033] In any embodiment of the first aspect, the mass proportion of the first additive in the non-aqueous electrolyte is W1, optionally between 0.001% and 20%, and further optionally between 0.1% and 5%. The cyclic sulfate ester compound is used to form a sufficient organic and inorganic hybrid SEI film with a more stable and stronger electron-blocking ability, thereby effectively improving not only the cycle performance of the secondary battery but also the output power of the secondary battery.

[0034] In any embodiment of the first aspect, the mass proportion of the second additive in the non-aqueous electrolyte is W2, and W2 is optionally between 0.001% and 20%, and further optionally between 0.1% and 5%.

[0035] In any embodiment of the first aspect, 0.01≤W1 / W2≤10, preferably 0.02≤W1 / W2≤5. By controlling the ratio of the two substances, the types and contents of the inorganic components on the negative electrode side are optimized, thereby further improving the stability, ion conductivity, and electron blocking capabilities of the SEI film, thereby further optimizing the overall SEI performance on the cycling and storage performance of the battery cell.

[0036] In any embodiment of the first aspect, the non-aqueous electrolyte further comprises an electrolyte, optionally the electrolyte comprises an alkali metal salt electrolyte; optionally the electrolyte comprises a lithium salt or a sodium salt; optionally, the lithium salt comprises one or more selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide, and the sodium salt comprises one or more selected from the group consisting of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide and sodium trifluoromethanesulfonate.

[0037] In any embodiment of the first aspect, the non-aqueous electrolyte further includes a non-aqueous solvent. Optionally, the non-aqueous solvent includes any one or more selected from the group consisting of cyclic carbonates, chain carbonates, nitrile solvents, ketone solvents and sulfone solvents; further optionally, the non-aqueous solvent includes one or more selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, tetrahydrofuran, ethylene glycol dimethyl ether, dioxolane, acetone, acetonitrile and butyronitrile.

[0038] In any embodiment of the first aspect, the additive further comprises one or more selected from the group consisting of sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic acid anhydride compounds, phosphite compounds, phosphate compounds, borate compounds, and carboxylate compounds.

[0039] A second aspect of the present application provides a secondary battery, which includes a positive electrode sheet, an electrolyte, a separator, and a negative electrode sheet, wherein the electrolyte includes any one of the above-mentioned non-aqueous electrolytes.

[0040] In any embodiment of the second aspect, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on one side or both sides of the positive electrode current collector, and the lithium ion diffusion coefficient of the positive electrode film layer is Ds, wherein 10 -16 cm 2 / s≤Ds≤10 -5 cm 2 / s; optionally, 10 -13 cm 2 / s≤Ds≤10 -9 cm 2 / s.

[0041] In any embodiment of the second aspect, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on one side or both sides of the negative electrode current collector. The porosity of the negative electrode film layer is 30%-45%, and can be optionally 37-42%.

[0042] In any embodiment of the second aspect, the negative electrode film layer includes a negative electrode active material. Optionally, the D V 50≥6μm, further optionally, the D V 50 is between 15μm-20μm.

[0043] A third aspect of the present application provides an electrical device including a secondary battery, wherein the secondary battery includes any one of the aforementioned secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0045] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0046] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .

[0047] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0048] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0049] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0050] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0051] In the drawings, the drawings are not drawn to scale.

[0052] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0053] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0054] Below, the embodiments of the non-aqueous electrolyte, secondary battery and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0055] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0057] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0058] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0059] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0060] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0061] [Secondary battery]

[0062] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0063] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte between the positive and negative electrode sheets mainly plays the role of conducting active ions.

[0064] [Non-aqueous electrolyte]

[0065] One embodiment of the present application provides a non-aqueous electrolyte, including additives, wherein the additives include a first additive and a second additive, wherein the first additive is any one or more cyclic sulfate compounds having a structure represented by general formula (I),

[0066] Among them, R 1 、R 2 、R 3 and R 4 Each is independently selected from any one of a group having a structure represented by general formula (II), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and n1 and n2 are each independently any integer from 0 to 2,

[0067] General formula (II) is

[0068] R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and n3 is any integer from 0 to 2;

[0069] The second additive is one or more of lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, a compound represented by the general formula (III), and a fluorosulfonate.

[0070] In the general formula (III), M is a metal, the metal includes one or more selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu and Ni, Y represents a boron atom or a phosphorus atom, X represents a halogen atom, R represents a C1-C10 alkylene group, a C1-C10 haloalkylene group, a C6-C20 arylene group, or a C6-C20 haloarylene group, and each group representing R is optionally substituted with a substituent or a heteroatom, m represents an integer of 1-3, n represents an integer of 0-4, q represents 0 or 1, and a, b, and c represent natural numbers;

[0071] Fluorosulfonate (FSO3) y M y+ , M y+ is a metal ion or an organic cation; metal ions include Li + 、Na + , K + , Rb + 、Cs + Mg 2+ , Ca 2+ 、Ba 2+ 、Al 3+ 、Fe 2+ 、Cu 2+ 、Fe 3+ 、Ni 2+ and Ni 3+ One or more of the groups.

[0072] The cyclic sulfate additive in the non-aqueous electrolyte will form a highly elastic SEI film on the negative electrode side during the first charge process. After further combining with the above-mentioned second additive, inorganic components such as Li2S, ROSO2Li, carbonates, LiF, borates, and phosphates will also be generated on the negative electrode side during the first charge of the secondary battery. Compared with single sulfides, the mixed inorganic components have more stable and higher ion conductivity and electron blocking capabilities. Therefore, the generated SEI film can more effectively block electrons, alleviate the continuous decomposition of the electrolyte at the negative electrode, optimize the cycle and storage performance of the battery cell, and greatly improve the battery cell life.

[0073] In some embodiments, the above R 1 and R 2 are not hydrogen atoms and R 3 and R 4 Not all hydrogen atoms. Of course, R 1 、R 2、R 3 、R 4 It can also be a hydrogen atom.

[0074] In some embodiments, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0075] R 1 and R 2 At the same time, it is a hydrogen atom and R 3 and R 4 One is a hydrogen atom and the other is any one of a group having a structure represented by general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and R 5 and R 6 Not all hydrogen atoms.

[0076] In some embodiments, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0077] R 3 and R 4 At the same time, it is a hydrogen atom and R 1 and R 2 One is a hydrogen atom and the other is any one of a group having a structure represented by general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and R 5 and R 6 Not all hydrogen atoms.

[0078] The above R 1 、R 2 、R 3 and R 4There are substituents in the groups. By introducing substituents such as alkyl groups, an elastic SEI film with a longer organic chain can be generated at the negative electrode, which can cope with the volume change of the negative electrode during the cycle and avoid the destruction of the SEI film; the introduction of substituents containing F and N can participate in the film formation at the negative electrode, generating a SEI film rich in more inorganic components such as LiF and Li3N, thereby improving the mechanical strength of the SEI film, and then improving the stability of the negative electrode SEI film, thereby achieving the purpose of further improving the battery cycle performance.

[0079] The above-mentioned alkyl group may be a straight-chain alkyl group, a branched-chain alkyl group or a cycloalkyl group, including but not limited to methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, cyclopropyl, cyclobutane, etc.; the alkyl group in the above-mentioned haloalkyl group includes but is not limited to a straight-chain alkyl group, a branched-chain alkyl group or a cycloalkyl group, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, cyclopropyl, cyclobutane, etc.; the halogen atom may be a fluorine atom, a chlorine atom or a bromine atom, and the halogen atom replaces any one or more hydrogen atoms on the alkyl group; the above-mentioned alkoxy group includes but is not limited to a cyclopropane group, an oxetane group, etc.; the halogen atom in the haloalkoxy group may be a fluorine atom, a chlorine atom or a bromine atom, and the halogen atom replaces any one or more hydrogen atoms on the alkoxy group; the alkenyl group includes but is not limited to -CH=CH2, -CH=CH2CH3, -CH2CH=CH2, -CH2CH=CH2CH3; the ester group includes but is not limited to methyl formate, ethyl formate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, etc.

[0080] In some embodiments, the cyclic sulfate compound has a structure represented by formula (I-1),

[0081] R 1 、R 2 、R 3 and R 4 Each independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group, and a sulfonic acid group;

[0082] General formula (II-1) is

[0083] R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group.

[0084] The cyclic sulfate rings in the general formula (I-1) are all five-membered rings, which can form a denser SEI film. Compared to six-membered rings, they have greater ring tension and are easier to form at the positive and negative electrodes. However, six-membered rings have less ring tension and are more stable, but they form more slowly at the negative electrode. Therefore, the efficiency of forming the electron-blocking SEI film is lower, which affects the effectiveness of the SEI film.

[0085] In some embodiments, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a C1-C3 haloalkoxy group, a C2-C3 alkenyl group, a C1-C3 ester group, a cyano group and a sulfonic acid group.

[0086] In some embodiments, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C3 alkyl group, and a C1-C3 halogenated alkyl group.

[0087] In some embodiments, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 Each independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group and an isopropyl group.

[0088] In some embodiments, the group represented by the structure of formula (II-1) is selected from any one of the following groups: Wherein, X is a F atom, a Cl atom or a Br atom;

[0089] Optionally, R 1 、R 2 、R 3 and R 4 Each independently selected from Any one of a hydrogen atom, a F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group and an isopropyl group, and X is a F atom;

[0090] In some embodiments, R 1 、R 2 、R 3 and R 4 Each independently selected from any one of a hydrogen atom, a methyl group and an ethyl group, and X is a F atom.

[0091] In some embodiments, the cyclic sulfate compound is selected from any one or more of the following compounds:

[0092] The preparation methods of some of the above-mentioned cyclic sulfate compounds are simpler, easier to promote and implement in industry, and have a more stable effect on improving the life of secondary batteries.

[0093] In some embodiments, in the general formula (III), the metal includes one or more selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu and Ni, Y represents a boron atom or a phosphorus atom, X represents a halogen atom, R represents a C1-C10 alkylene group, a C1-C10 halogenated alkylene group, a C6-C20 arylene group, or a C6-C20 halogenated arylene group, and each group representing R is optionally substituted with a substituent or a heteroatom, m represents an integer of 1-3, n represents an integer of 0-4, and q represents 0 or 1.

[0094] In some embodiments, the substituents in the general formula (III) replace one or more hydrogen atoms in R, which can be selected from conventional groups, such as any one of halogen atoms, -CN, -NCO, -OH, -COOH, -SOOH, -OC=(O)alkyl, -C=(O)Oalkyl, C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl and C2-C10 alkoxy; in some embodiments, the heteroatom in the general formula (III) replaces the carbon atoms on the carbon chain in R, which can be any one or more of nitrogen atoms, sulfur atoms, phosphorus atoms and boron atoms.

[0095] In some embodiments, the compound of general formula (III) is selected from one or more of the following compounds: lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium trioxalatophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobismalonate phosphate, lithium tetrafluoromalonate phosphate, lithium trimalonate phosphate, lithium difluoromalonateborate, lithium bismalonateborate, preferably one or more of lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, lithium difluorooxalatoborate, and lithium bisoxalatoborate.

[0096] In some embodiments, the fluorosulfonate salt includes any one or more of lithium fluorosulfonate, sodium fluorosulfonate, and potassium fluorosulfonate.

[0097] The amount of the cyclic sulfate compound in each of the above embodiments of the present application can refer to the amount of conventional cyclic sulfate compounds in conventional non-aqueous electrolytes. In some embodiments, the mass proportion of the first additive in the non-aqueous electrolyte is W1, and W1 is optionally between 0.001% and 20%, such as 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, 10%, 15% or 20%, and further optionally W1 is between 0.1% and 5%. By utilizing the cyclic sulfate compound to form a sufficient organic and inorganic mixed SEI film with a more stable and stronger electron-blocking ability, not only can the cycle performance of the secondary battery be effectively improved, but also the output power of the secondary battery can be improved. By limiting the above-mentioned mass content, it is possible to avoid the SEI film not being able to fully function due to too little content of the cyclic sulfate compound, and to avoid the electrolyte viscosity being too high and the SEI film formed on the negative electrode being too thick due to too much cyclic sulfate compound, thereby worsening the conductivity of the electrolyte and further worsening the improvement effect of the cycle performance and charging capacity.

[0098] In some embodiments of the present application, the mass percentage of the second additive in the non-aqueous electrolyte is W2, and W2 is optionally between 0.001% and 20%, such as 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 3%, 5%, 10%, 15%, or 20%. W2 can further be between 0.1% and 5%. This can fully utilize the second additive to enhance the stability of the SEI film and better improve the cycling and storage performance of the battery cell.

[0099] In some embodiments, 0.01≤W1 / W2≤10, preferably 0.02≤W1 / W2≤5. By controlling the ratio of the two substances, the types and contents of the inorganic components on the negative electrode side are optimized, further improving the stability, ion conductivity, and electron blocking capabilities of the SEI film, thereby further optimizing the overall SEI performance on the cycle and storage performance of the battery cell.

[0100] In some embodiments, the non-aqueous electrolyte further includes an electrolyte. Any electrolyte that can be generally used in non-aqueous electrolytes can be considered for application in the non-aqueous electrolyte of the present application. Those skilled in the art can make a selection based on the battery system to which the non-aqueous electrolyte is applied, such as selecting a conventional electrolyte suitable for lithium-ion secondary batteries or sodium-ion secondary batteries. In some embodiments, the electrolyte optionally includes an alkali metal salt electrolyte; optionally, the electrolyte includes a lithium salt or a sodium salt; optionally, the lithium salt includes one or more selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide, and the sodium salt includes one or more selected from the group consisting of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, and sodium trifluoromethanesulfonate.

[0101] The above lithium salts or sodium salts may be used alone or in combination of two or more.

[0102] The content of electrolyte in the non-aqueous electrolyte can refer to the electrolyte content in conventional non-aqueous electrolyte. In some embodiments, the electrolyte content in the non-aqueous electrolyte is 0.1mol / L-5mol / L, for example, it can be 0.1mol / L, 0.3mol / L, 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, 4mol / L or 5mol / L, optionally 0.5mol / L-1.5mol / L, further optionally 0.7mol / L-1.2mol / L.

[0103] In some embodiments, the non-aqueous electrolyte further comprises a non-aqueous solvent. Optionally, the non-aqueous solvent comprises any one or more selected from the group consisting of cyclic carbonates, chain carbonates, nitrile solvents, ketone solvents and sulfone solvents; further optionally, the non-aqueous solvent comprises one or more selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, tetrahydrofuran, ethylene glycol dimethyl ether, dioxolane, acetone, acetonitrile and butyronitrile. The above non-aqueous solvents can be used alone or in combination of two or more. For example, to improve the load characteristics and low-temperature characteristics of a secondary battery, a mixed solvent of a cyclic carbonate and a chain carbonate can be used. When the non-aqueous electrolyte of the present application is used in a solid battery, a solid solvent such as dimethyl sulfone can be used.

[0104] In addition to the aforementioned additives, the additives may also include negative electrode film-forming additives, positive electrode film-forming additives, and additives capable of improving certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc. In some embodiments, the aforementioned additives further include, but are not limited to, one or more selected from the group consisting of sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic acid anhydride compounds, phosphite compounds, phosphate compounds, borate compounds, and carboxylate compounds.

[0105] [Method for preparing a cyclic sulfate compound having a structure represented by general formula (I)]

[0106] The preparation method of the cyclic sulfate compound having the structure shown in the general formula (I) of the present application refers to the following synthetic route:

[0107] The reaction temperature of the first step is controlled at 30-60° C.; the reaction temperature of the second step is controlled at 10-30° C. The second step is catalyzed by a catalyst such as ruthenium trichloride trihydrate, and the oxidant can be sodium hypochlorite, ozone, etc.

[0108] [Positive electrode]

[0109] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.

[0110] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0111] In some embodiments, the positive electrode 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 base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0112] In some embodiments, the lithium ion diffusion coefficient of the positive electrode film is Ds, wherein 10 -16 cm 2 / s≤Ds≤10 -5 cm 2 / s; optionally, 10 -13 cm2 / s≤Ds≤10 -9 cm 2 / s; Optionally, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material that meets the above conditions and is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an 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 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 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 NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0113] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0114] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0115] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0116] [Negative electrode]

[0117] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0118] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0119] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0120] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0121] In some embodiments, the porosity of the negative electrode film is 30%-45%, and can be 37-42%. When the porosity of the negative electrode film on the negative electrode sheet is less than 30%, the interparticle pores within the negative electrode film are limited, the particle structure is squeezed and damaged, and the electrolyte infiltration becomes more difficult, resulting in increased polarization of the battery cell and deterioration of the long-term cycle performance of the battery cell. When the porosity of the negative electrode film on the negative electrode sheet is greater than 45%, the electrode sheet rebounds significantly, resulting in reduced actual compaction of the electrode sheet, affecting the energy density of the battery cell.

[0122] The porosity of the negative electrode active material coating on the negative electrode sheet was measured using an AccuPyc II 1340 true density meter according to the instrument's manual. The porosity of the negative electrode active material coating on the electrode sheet can be controlled by adjusting the particle size of the negative electrode active material and the pressure during the cold pressing process.

[0123] In some embodiments, the negative electrode active material layer includes a negative electrode active material. Optionally, the D V 50≥6μm, further optionally, the D V 50 is between 15μm and 20μm. Since the first additive and the second additive will form a SEI film of a certain thickness on the surface of the negative electrode plate, increasing the volume particle size of the negative electrode active material can reduce the contact area between the negative electrode active material and the electrolyte, reduce the side reactions on the negative electrode surface, and thus improve the battery cell cycle and storage performance.

[0124] In this application, the volume average particle size Dv50 of the negative electrode active material has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be measured using a laser powder analyzer (e.g., Master Size 3000) with reference to GB / T 19077-2016 particle size distribution laser diffraction method.

[0125] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may 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).

[0126] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0128] In some embodiments, the negative electrode sheet can be prepared by the following method: the 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.

[0129] [Isolation film]

[0130] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0131] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0132] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0133] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0134] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0135] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0136] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 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 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0137] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0138] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0139] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0140] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0141] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0142] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0143] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0144] Figure 6 shows an example of an electric device. This device 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, a battery pack or battery module can be used.

[0145] [Example]

[0146] Below, the embodiment of the application is described. The embodiment described below is exemplary, is only used to explain the application, and is not to be construed as limiting the application. Where specific techniques or conditions are not indicated in the embodiment, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not indicate the manufacturer are conventional products that can be obtained commercially. The remaining reagents or compound information are recorded in Table 1.

[0147] Table 1

[0148] Synthesis Example 1: Compound 1 Synthesis

[0149] Step 1: Add 300g (2mol) of solid 1,6-dideoxygalactitol to a 2L three-necked flask, start stirring, and add 523g (4.4mol) of thionyl chloride dropwise to the three-necked flask. Control the temperature at about 15°C during the addition process. After the addition is completed, keep the reaction at 45°C for 4 hours. A large amount of pasty solid precipitates from the reaction solution. After cooling, slowly add 1L of deionized water dropwise, and quickly stir to break up the reaction system. The filtered solid is slurried and washed with deionized water several times until the pH is neutral. The filter cake is dried under reduced pressure at 60°C to obtain an intermediate product.

[0150] Step 2: To a 3L three-necked flask, 184.2g (0.8mol) of intermediate 1 was added, 1000mL of acetonitrile was added, and 80mg of ruthenium trichloride trihydrate catalyst was added. After nitrogen displacement of the system, the system was cooled to 20°C, stirring was started, and 2000g of 20% sodium hypochlorite aqueous solution was added dropwise within 1h, and the reaction temperature was controlled at 10-20°C. After the addition was complete, the mixture was stirred at 10-20°C for 10min, separated, and the organic phase was quenched with sodium sulfite aqueous solution until the starch potassium iodide test paper did not turn blue. The liquid was separated again, the organic layer was concentrated, and crystallized from acetonitrile to obtain a white powder solid, which was the above-mentioned compound 1. 1H-NMR, CD3CN, δppm 5.42-5.39 (m, 2H), 5.36-5.34 (m, 2H), 1.67-1.65 (d, 6H).

[0151] Synthesis Example 2: Compound 2 Synthesis

[0152] Step 1: 356.5 g (2 mol) of solid 3,4,5,6-octanetrol was added to a 2 L three-necked flask, stirring was started, and 523 g (4.4 mol) of thionyl chloride was added dropwise to the three-necked flask. The temperature was controlled at about 15 ° C during the addition process. After the addition was completed, the reaction was kept at 45 ° C for 4 hours. A large amount of pasty solid precipitated from the reaction solution. After cooling, 1 L of deionized water was slowly added dropwise, and the reaction system was quickly stirred to break up. The filtered solid was slurried and washed with deionized water several times until the pH was neutral. The filter cake was dried under reduced pressure at 60 ° C to obtain an intermediate product.

[0153] Step 2: 216.2 g (0.8 mol) of intermediate 1 was added to a 3L three-necked flask, 1000 mL of acetonitrile was added, 80 mg of ruthenium trichloride trihydrate catalyst was added, and after nitrogen replacement of the system, the system was cooled to 20 ° C, stirring was started, and 2000 g of 20% sodium hypochlorite aqueous solution was added dropwise within 1 h, and the reaction temperature was controlled at 10-20 ° C; after the addition was complete, stirred at 10-20 ° C for 10 min, separated, and the organic phase was quenched with sodium sulfite aqueous solution until the starch potassium iodide test paper did not turn blue; the liquid was separated again, the organic layer was concentrated, and acetonitrile was crystallized to obtain compound 2.

[0154] Synthesis Example 3: Compound 3 Synthesis

[0155] Step 1: 328.4 g (2 mol) of solid 2,3,4,5-heptetrol was added to a 2L three-necked flask, stirring was started, and 523 g (4.4 mol) of thionyl chloride was added dropwise to the three-necked flask. The temperature was controlled at about 15°C during the addition process. After the addition was completed, the reaction was kept at 45°C for 4 hours. A large amount of pasty solid precipitated from the reaction solution. After cooling, 1 L of deionized water was slowly added dropwise, and the reaction system was quickly stirred to break up. The filtered solid was slurried and washed with deionized water several times until the pH was neutral. The filter cake was dried under reduced pressure at 60°C to obtain an intermediate product.

[0156] Step 2: 205 g (0.8 mol) of intermediate product 1 was added to a 23-necked flask, 1000 mL of acetonitrile was added, and the mixture was stirred until the solid was completely dissolved. 80 mg of ruthenium trichloride trihydrate catalyst was added. After nitrogen displacement of the system, the system was cooled to 20 ° C., stirring was started, and 2000 g of 20% sodium hypochlorite aqueous solution was added dropwise within 1 h. The reaction temperature was controlled at 10-20 ° C. After the addition was complete, the mixture was stirred at 10-20 ° C for 10 min, separated, and the organic phase was quenched with sodium sulfite aqueous solution until the starch potassium iodide test paper did not turn blue; the liquid was separated again, the organic layer was concentrated, and the acetonitrile crystals were obtained to obtain compound 3 (163.1 g, yield 82.8%).

[0157] Synthesis Example 4: Compound 4 Synthesis

[0158] Step 1: 392.4 g (2 mol) of solid 1,2,3,4,5.6-heptanhexaol was added to a 2 L three-necked flask, stirring was started, and 784.5 g (6.6 mol) of thionyl chloride was added dropwise to the three-necked flask. The temperature was controlled at about 15 ° C during the addition process. After the addition was completed, the reaction was kept at 45 ° C for 4 hours. A large amount of pasty solid precipitated from the reaction solution. After cooling, 1 L of deionized water was slowly added dropwise, and the reaction system was quickly stirred to break up. The filtered solid was slurried and washed with deionized water several times until the pH was neutral. The filter cake was dried under reduced pressure at 60 ° C to obtain an intermediate product.

[0159] Step 2: 140 g (0.4 mol) of intermediate 1 was added to a 4L three-necked flask, 1000 mL of acetonitrile was added, 110 mg of ruthenium trichloride trihydrate catalyst was added, and after nitrogen replacement of the system, the system was cooled to 20 ° C, stirring was started, and 1500 g of 20% sodium hypochlorite aqueous solution was added dropwise within 1 h, and the reaction temperature was controlled at 10-20 ° C; after the addition was complete, stirred at 10-20 ° C for 10 min, separated, and the organic phase was quenched with sodium sulfite aqueous solution until the starch potassium iodide test paper did not turn blue; the liquid was separated again, the organic layer was concentrated, and acetonitrile was crystallized to obtain compound 4.

[0160] Synthesis Example 5: Compound 5 Synthesis

[0161] Step 1: 484 g (2 mol) of solid octitol was added to a 2L three-necked flask, stirring was started, and 1046 g (8.8 mol) of thionyl chloride was added dropwise to the three-necked flask. The temperature was controlled at about 15 ° C during the addition process. After the addition was completed, the reaction was kept at 45 ° C for 4 hours. A large amount of pasty solid precipitated from the reaction solution. After cooling, 1 L of deionized water was slowly added dropwise, and the reaction system was quickly stirred to break up. The filtered solid was washed with deionized water several times until the pH was neutral. The filter cake was dried under reduced pressure at 60 ° C to obtain an intermediate product.

[0162] Step 2: 183.2 g (0.4 mol) of the intermediate product was added to a 4L three-necked flask, 1000 mL of acetonitrile was added, 150 mg of ruthenium trichloride trihydrate catalyst was added, and after nitrogen replacement of the system, the system was cooled to 20 ° C, stirring was started, and 2000 g of 20% sodium hypochlorite aqueous solution was added dropwise within 1 h, and the reaction temperature was controlled at 10-20 ° C; after the addition was complete, the mixture was stirred at 10-20 ° C for 10 min, separated, and the organic phase was quenched with sodium sulfite aqueous solution until the starch potassium iodide test paper did not turn blue; the liquid was separated again, the organic layer was concentrated, and acetonitrile was crystallized to obtain compound 5.

[0163] In addition, the synthesis method of the compound refers to Synthesis Example 1, using the corresponding substrate in Table 2 to replace 1,6-dideoxygalactitol.

[0164] Table 2

[0165] Example 1

[0166] Secondary battery preparation:

[0167] Electrolyte composition: Compound 1 is used as the first additive, and its mass content in the electrolyte is 2%; Compound 3-6 is used as the second additive, and its mass content in the electrolyte is 2%; lithium hexafluorophosphate LiPF6 is used as the electrolyte, and its content in the electrolyte is 10%, and a mixture of EC+EMC (ethylene carbonate+ethyl methyl carbonate) with a volume ratio of 3:7 is used as the solvent.

[0168] Positive electrode preparation:

[0169] The positive electrode active material lithium iron phosphate (LiFePO4), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and are fully stirred and mixed to obtain the positive electrode slurry; the positive electrode slurry is then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain the positive electrode sheet.

[0170] Negative electrode preparation:

[0171] Anode active material graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water at a weight ratio of 90:4:4:2 and mixed thoroughly to prepare anode slurry. The slurry was then evenly coated onto anode current collector copper foil once or multiple times. The resulting negative electrode sheet, with a negative electrode film layer, was dried, cold-pressed, and slit. The porosity of the negative electrode film layer was 40%, and the graphite used had a DV50 of 18 μm.

[0172] Diaphragm:

[0173] Conventional polypropylene film is used as the separator.

[0174] Lithium-ion battery assembly:

[0175] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation, and then wound to obtain an electrode assembly; the electrode assembly is placed in a battery casing, dried, and then injected with electrolyte, and then undergoes formation, static and other processes to produce a lithium-ion battery.

[0176] The substance or amount of the first additive and the substance or amount of the second additive in the electrolytes of Examples 1 to 41 and Comparative Examples 1 to 4 are recorded in Table 3, and the rest are the same as in Example 1.

[0177] Table 3

[0178] The porosity of the negative electrode film layer and the Dv50 of the negative electrode material used in Examples 42 to 51 are recorded in Table 4. The rest is the same as in Example 1.

[0179] Table 4

[0180] Performance testing:

[0181] 1. Cycle performance test

[0182] At 25°C, charge the lithium-ion battery at a constant current of 0.5C to 3.65V, then charge it at a constant voltage of 3.65 until the current is less than 0.05C, and then discharge it at a constant current of 0.5C to 2.5V. This is one charge and discharge cycle. Repeat this charge and discharge cycle and calculate the number of cycles after the lithium-ion battery decays to 80%.

[0183] 2. Storage performance test

[0184] At 25°C, the prepared lithium-ion secondary batteries were first charged to 3.65V at a constant current of 0.33C, and then further charged to a current of 0.05C at a constant voltage of 3.65V, and then discharged to 2.5V at a constant current of 0.33C. The discharge capacity C0 is the discharge capacity of the lithium-ion secondary battery before high-temperature storage; then the lithium-ion secondary battery was charged to 3.65V at a constant current of 0.33C, and charged to a current of 0.05C at a constant voltage of 3.65V to fully charge the lithium-ion battery. The battery was placed in a 60°C oven for 30 days, the battery was taken out, and the battery was placed in a 25°C environment for 0.33C discharge. The discharge capacity was recorded as C1; Capacity retention rate = (C1 / C0)×100%

[0185] 3. Volume expansion rate test

[0186] At 25°C, the prepared lithium-ion secondary batteries were first charged to 3.65V at a constant current of 0.33C, further charged at a constant voltage of 3.65V to a current of 0.05C, and then discharged to 2.5V at a constant current of 0.33C. The discharge capacity was the discharge capacity of the lithium-ion secondary battery before high-temperature storage; then the lithium-ion secondary battery was charged to 3.65V at a constant current of 0.33C, and charged to a current of 0.05C at a constant voltage of 3.65V to fully charge the lithium-ion battery. The volume of the battery was tested using the drainage method. The lithium-ion battery was then stored at 60°C for 60 days. After the storage was completed, the lithium-ion secondary battery was placed in an environment of 25°C and the volume of the battery was tested using the drainage method. Battery volume expansion rate = (volume after storage / volume before storage - 1)%.

[0187] The test results are recorded in Table 5.

[0188] Table 5

[0189] According to the data comparison in Table 5, it can be found that when different first additives are used in combination with the same second additive, the cycle performance and storage performance of the battery are improved, but the degree of improvement is different. Moreover, according to the data comparison of Example 1 and Examples 30 to 41, it can be found that the amount of the first additive and the second additive and the ratio of the two will affect the improvement effect of the cycle performance and storage performance of the battery, especially when W1 / W2 is between 0.05 and 5, the cycle performance, storage performance and volume expansion rate of the battery are significantly improved. According to the data comparison of Examples 42 to 51, it can be found that the porosity of the negative electrode film layer on the negative electrode side and the D V50 have an impact on the improvement of battery cycle performance, storage performance and volume expansion rate.

[0190] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A non-aqueous electrolyte comprising an additive, wherein: The additives include a first additive and a second additive, wherein the first additive is any one or more cyclic sulfate compounds having a structure shown in general formula (I), Among them, R 1 , R 2 , R 3 and R 4 Each is independently selected from any one of a group having a structure represented by general formula (II), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and n1 and n2 are each independently any integer of 0-2, The general formula (II) is R 5 and R 6 Each is independently selected from any one of a group having a structure represented by the general formula (II), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and n3 is any integer from 0 to 2; The second additive includes one or more of lithium monofluorophosphate, lithium difluorophosphate, lithium tetrafluoroborate, a compound represented by the general formula (III) and a fluorosulfonate. In the general formula (III), M is a metal, and the metal includes one or more selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu and Ni, Y represents a boron atom or a phosphorus atom, X represents a halogen atom, R represents a C1-C10 alkylene group, a C1-C10 halogenated alkylene group, a C6-C20 arylene group, or a C6-C20 halogenated arylene group, and each group of R is optionally substituted by a substituent or a heteroatom, m represents an integer of 1-3, n represents an integer of 0-4, q represents 0 or 1, and a, b, and c represent natural numbers; The fluorosulfonate is (FSO3) y M y+ , M y+ is a metal ion or an organic cation; the metal ion includes Li + 、Na + , K + , Rb + , Cs + Mg 2+ , Ca 2+ , Ba 2+ 、Al 3+ , Fe 2+ , Cu 2+ , Fe 3+ 、Ni 2+ and Ni 3+ One or more of the groups.

2. The nonaqueous electrolyte according to claim 1, wherein R 1 and R 2 are not hydrogen atoms and R 3 and R 4 Not all hydrogen atoms at the same time; Or, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 The following conditions are met: R 1 and R 2 At the same time, R 3 and R 4 One is a hydrogen atom and the other is any one of a group having a structure represented by the general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and R 5 and R 6 Not all hydrogen atoms at the same time; Or, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 The following conditions are met: R 3 and R 4 At the same time, R 1 and R 2 One is a hydrogen atom and the other is any one of a group having a structure represented by the general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group, and R 5 and R 6 Not all are hydrogen atoms.

3. The nonaqueous electrolyte according to claim 1 or 2, wherein The cyclic sulfate compound has a structure represented by general formula (I-1), R 1 , R 2 , R 3 and R 4 Each is independently selected from any one of a group having a structure represented by the general formula (II-1), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group; The general formula (II-1) is R 5 and R 6 Each is independently selected from a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C6 alkyl group, a C1-C6 haloalkyl group, a C1-C6 alkoxy group, a C1-C6 haloalkoxy group, a C2-C6 alkenyl group, a C2-C6 ester group, a cyano group and a sulfonic acid group.

4. The nonaqueous electrolyte according to any one of claims 1 to 3, wherein R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each independently selected from a group having a structure represented by the general formula (II-1), hydrogen any one of an atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a C1-C3 haloalkoxy group, a C2-C3 alkenyl group, a C1-C3 ester group, a cyano group and a sulfonic acid group; Optionally, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each is independently selected from any one of a group having a structure represented by general formula (II-1), a hydrogen atom, a halogen atom, a C1-C3 alkyl group, and a C1-C3 halogenated alkyl group; Optionally, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 Each is independently selected from any one of a group having a structure represented by the general formula (II-1), a hydrogen atom, a F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group and an isopropyl group; Optionally, the group of the structure represented by the general formula (II-1) is selected from any one of the following groups: Wherein, X is a F atom, a Cl atom or a Br atom; Optionally, R 1 , R 2 , R 3 and R 4 Each independently selected from Any one of a hydrogen atom, a F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group and an isopropyl group, and X is a F atom; Further optionally, R 1 , R 2 , R 3 and R 4 Each independently selected from any of a hydrogen atom, a methyl group and an ethyl group, and X is a F atom.

5. The non-aqueous electrolyte according to claim 1, wherein The cyclic sulfate compound is selected from any one or more of the following compounds:

6. The nonaqueous electrolyte according to any one of claims 1 to 5, wherein In the general formula (III), the metal includes one or more selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Ba, Al, Fe, Cu and Ni, Y represents a boron atom or a phosphorus atom, X represents a halogen atom, R represents a C1-C10 alkylene group, a C1-C10 halogenated alkylene group, a C6-C20 arylene group, or a C6-C20 halogenated arylene group, and each group representing the R is optionally substituted by a substituent or a heteroatom, m represents an integer of 1-3, n represents an integer of 0-4, and q represents 0 or 1.

7. The nonaqueous electrolyte according to any one of claims 1 to 6, wherein The fluorosulfonate includes any one or more of lithium fluorosulfonate, sodium fluorosulfonate and potassium fluorosulfonate.

8. The nonaqueous electrolyte according to any one of claims 1 to 7, wherein The mass proportion of the first additive in the non-aqueous electrolyte is W1, and W1 is optionally between 0.001% and 20%, and further optionally between 0.1% and 5%; and / or the mass proportion of the second additive in the non-aqueous electrolyte is W2, optionally W2 is between 0.001% and 20%, and further optionally W2 is between 0.1% and 5%; Optionally, 0.01≤W1 / W2≤10, preferably 0.02≤W1 / W2≤5.

9. The nonaqueous electrolyte according to any one of claims 1 to 8, wherein The non-aqueous electrolyte also includes an electrolyte, and optionally the electrolyte includes an alkali metal salt electrolyte; optionally the electrolyte includes a lithium salt or a sodium salt; optionally, the lithium salt includes one or more selected from the group consisting of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide, and the sodium salt includes one or more selected from the group consisting of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium perchlorate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide and sodium trifluoromethanesulfonate.

10. The nonaqueous electrolyte according to any one of claims 1 to 9, wherein The non-aqueous electrolyte also includes a non-aqueous solvent. Optionally, the non-aqueous solvent includes any one or more selected from the group consisting of cyclic carbonates, chain carbonates, nitrile solvents, ketone solvents and sulfone solvents; further optionally, the non-aqueous solvent includes one or more selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone, diethyl sulfone, tetrahydrofuran, ethylene glycol dimethyl ether, dioxolane, acetone, acetonitrile and butyronitrile.

11. The nonaqueous electrolyte according to any one of claims 1 to 10, wherein The additive also includes one or more selected from the group consisting of sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic acid anhydride compounds, phosphite compounds, phosphate compounds, borate compounds, and carboxylate compounds.

12. A secondary battery, comprising a positive electrode sheet, an electrolyte, a separator and a negative electrode sheet, wherein: The electrolyte solution includes the nonaqueous electrolyte solution according to any one of claims 1 to 11.

13. The secondary battery according to claim 12, wherein: The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on one side or both sides of the positive electrode current collector. The lithium ion diffusion coefficient of the positive electrode film layer is Ds, wherein 10 -16 cm 2 / s≤Ds≤10 -5 cm 2 / s; optionally, 10 -13 cm 2 / s≤Ds≤10 -9 cm 2 / s.

14. The secondary battery according to claim 13, wherein The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on one side or both sides of the negative electrode current collector, and the porosity of the negative electrode film layer is 30%-45%, and can be optionally 37-42%; The negative electrode film layer includes a negative electrode active material. Optionally, the D V 50≥6μm, further optionally, the D of the negative electrode active material V 50 between 15μm-20μm.

15. An electrical device comprising a secondary battery, wherein: The secondary battery includes the secondary battery according to any one of claims 12 to 14.

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