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

Abstract

The invention provides a non-aqueous electrolyte for a secondary battery, the secondary battery and an electric device. The non-aqueous electrolyte for the secondary battery comprises an additive and a non-aqueous solvent, wherein the non-aqueous solvent comprises dimethyl carbonate; the additive comprises a cyclic sulfate compound as shown in a formula (I); # imgabs0 #

Description

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

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

[0002] In recent years, the application of secondary batteries has become increasingly widespread. They are 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 secondary batteries have achieved great development, higher requirements have been placed on their DCR, cycle performance, and storage performance.

[0003] Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a non-aqueous electrolyte for a secondary battery, a secondary battery and an electrical device. The use of the non-aqueous electrolyte of the present application improves the DCR of the battery, improves the cycle performance and storage performance of the battery, reduces the cycle gas production of the battery, and improves the rate performance of the battery.

[0005] In order to achieve the above-mentioned object, the present application provides a non-aqueous electrolyte for a secondary battery in a first aspect, comprising an additive and a non-aqueous solvent, wherein the non-aqueous solvent comprises dimethyl carbonate;

[0006] The additive comprises a cyclic sulfate compound represented by formula (I),

[0007] 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 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] R 5 and R 6 Each is independently selected from any one of 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;

[0009] R 1 and R2 are not hydrogen atoms and R 3 and R 4 Not all hydrogen atoms at the same time;

[0010] Or, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0011] 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 at the same time;

[0012] Or, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0013] 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.

[0014] Thus, the present application forms a non-aqueous electrolyte by combining dimethyl carbonate and additives. The non-aqueous electrolyte of the present application has better high-voltage resistance. During the first charging process of the battery, the additive forms a more stable inorganic and organic mixed CEI film on the surface of the positive electrode with stronger electron blocking ability, which inhibits the side reaction between the electrolyte and the positive electrode, improves the DCR of the battery, improves the cycle performance and storage performance of the battery, and reduces the cycle gas production of the battery. Dimethyl carbonate can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and thus improve the rate performance of the battery.

[0015] In any embodiment, the cyclic sulfate compound has a structure represented by formula (I-1),

[0016] 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-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;

[0017] R 5 and R 6 Each is independently selected from any one of 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.

[0018] The cyclic sulfate rings in the general formula (I-1) are all five-membered rings, which can form denser CEI films. Compared to six-membered rings, these rings have greater ring tension and are easier to form films on the positive electrode. However, six-membered rings have less ring tension and are more stable, but they form films more slowly on the positive electrode. Therefore, the efficiency of forming electron-blocking CEI films is lower, affecting the effectiveness of the CEI films.

[0019] In any embodiment, 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-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a C1-C3 haloalkoxy group and a cyano group; R 5 and R 6 Each is independently selected from any one of 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 and a cyano group;

[0020] Optionally, 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-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group and a cyano group; R 5 and R6 Each is independently selected from any one of a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group and a cyano group;

[0021] More optionally, 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 F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group; R 5 and R 6 Each is 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, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group;

[0022] Further optionally, the group of the structure represented by the general formula (II-1) is selected from any one of the following groups:

[0023] Wherein, X is a F atom, a Cl atom or a Br atom.

[0024] In any embodiment, 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, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group, wherein X is a F atom;

[0025] Optionally, R 1 、R 2 、R 3 and R 4 Each independently selected from Any one of a hydrogen atom, a F atom, a methyl group, an ethyl group, a propyl group, a trifluoromethyl group, an ethoxy group and a cyano group, wherein X is a F atom.

[0026] In any embodiment, the cyclic sulfate compound is selected from the following compounds:

[0027] The preparation method of the cyclic sulfate compound is simple, which is conducive to promotion and implementation in industry, and has a more stable effect on improving the cycle performance of the battery.

[0028] In any embodiment, the mass content of the additive in the non-aqueous electrolyte is 0.001%-15%, optionally 0.005%-10%, and more optionally 0.05%-5%.

[0029] When the mass content of the additive in the non-aqueous electrolyte is within the above range, the high-voltage resistance of the electrolyte can be further improved, and the stability and electron-blocking ability of the positive electrode CEI film can be further improved to inhibit the side reaction between the electrolyte and the positive electrode, thereby improving the DCR of the battery, improving the cycle performance and storage performance of the battery, and reducing the cycle gas production of the battery.

[0030] In any embodiment, the mass content of the dimethyl carbonate in the non-aqueous solvent is 5%-80%, optionally 10%-70%, and more optionally 20%-50%.

[0031] The mass content of dimethyl carbonate in the non-aqueous solvent is within the above range, which further improves the DCR of the battery, improves the cycle performance and storage performance of the battery, reduces the cycle gas production of the battery, further reduces the viscosity of the electrolyte, thereby increasing the conductivity of the electrolyte and improving the rate performance of the battery.

[0032] The second aspect of the present application further provides a battery, comprising the non-aqueous electrolyte of the first aspect of the present application, a positive electrode plate and a negative electrode plate, wherein the negative electrode plate comprises a negative electrode active material; optionally, the secondary battery is a lithium secondary battery.

[0033] Thus, the present application forms a non-aqueous electrolyte by combining dimethyl carbonate and additives. The electrolyte of the present application has better high-voltage resistance. During the first charge of the battery, the additive forms a more stable inorganic and organic mixed CEI film on the surface of the positive electrode with stronger electron blocking ability, which inhibits the side reaction between the electrolyte and the positive electrode, improves the DCR of the battery, and improves the cycle performance and storage performance of the battery. Dimethyl carbonate can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and thus improve the rate performance of the battery.

[0034] In any embodiment, the resistance of the positive electrode plate is less than or equal to 15Ω, and can be optionally less than or equal to 8Ω.

[0035] As a result, while improving the stability and safety of the battery system, the battery has good kinetic performance, improves the DCR of the battery, improves the cycle performance and storage performance of the battery, reduces the cycle gas production of the battery, and improves the rate performance of the battery.

[0036] In any embodiment, the volume average particle size Dv50 of the negative electrode active material is 3-30 μm, optionally 6-20 μm, and more optionally 8-15 μm.

[0037] The volume average particle size Dv50 of the negative electrode active material satisfies the above range, which is beneficial to forming a stable SEI film on the surface of the negative electrode, reducing the side reaction between the electrolyte and the negative electrode active material, reducing the cyclic gas generation amount of the battery, improving the cyclic performance and storage performance of the battery, improving the DCR of the battery, being beneficial to reducing the polarization degree of the battery, and improving the capacity performance of the battery.

[0038] In any implementation manner, the positive electrode sheet includes a positive electrode active material; optionally, the positive electrode active material includes Li 1+x Ni a Co b M 1-a-b O 2-y A y ; wherein, M includes one or more elements of Mn, Fe, Cr, Ti, Zn, V, Al, Zr, Ce, Mg, Ga, Cu, Nb, and may be optionally one or two elements including Mn and Al; A includes one or more elements of S, F, Cl, I, and may be optionally one or two elements including S and F; -0.1 ≤ x ≤ 0.2; 0 < a < 1, may be optionally 0.5 ≤ a < 1, more optionally 0.7 ≤ a ≤ 0.9; 0 < b < 1, may be optionally < b < 0.5, more optionally 0 < b ≤ 0.2; 0 < a + b < 1; 0 ≤ y < 0.2.

[0039] The third aspect of the present application provides an electrical device, including the non-aqueous electrolyte for a secondary battery of the first aspect of the present application or the secondary battery of the second aspect of the present application. Description of the Drawings

[0040] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0041] FIG. 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in FIG. 1.

[0042] FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0043] FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0044] FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4.

[0045] FIG. 6 is a schematic diagram of an electrical device using the secondary battery according to an embodiment of the present application as a power source.

[0046] Description of the Reference Numerals:

[0047] 1 battery pack; 2 upper box body; 3 lower box body; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. Detailed Embodiments

[0048] Below, the embodiments of the non-aqueous electrolyte for secondary batteries, secondary batteries, battery modules, battery packs and electrical devices 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 are 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.

[0049] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0051] 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.

[0052] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates 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.

[0053] 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 indicate that other components not listed may also be included or that only the listed components are included.

[0054] 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).

[0055] If not otherwise specified, in this application, the term "halogen" refers to atoms of Group VIIA elements, including fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), etc.

[0056] Unless otherwise specified, in this application, the term "C1-C6 alkyl" refers to a straight-chain or branched alkyl group containing 1 to 6 carbon atoms, specifically including C1-C3 alkyl, C2-C4 alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl or n-hexyl, etc.

[0057] Unless otherwise specified, the term "C1-C6 haloalkyl" as used herein refers to a C1-C6 alkyl group with one or more H groups substituted with halogen, wherein "C1-C6 alkyl" and "halogen" are as defined above. Specifically, it includes C1-C3 haloalkyl and C2-C4 haloalkyl groups, such as monofluoromethyl, difluoromethyl, trifluoromethyl, and 2,2,2-trifluoroethyl.

[0058] If not otherwise specified, in this application, the term "C1-C6 alkoxy" refers to a C1-C6 alkyl-O-group, wherein "C1-C6 alkyl" is as described above. Non-limiting examples of suitable C1-C6 alkoxy groups include methoxy, ethoxy, and isopropoxy.

[0059] Unless otherwise specified, the term "C1-C6 haloalkoxy" as used herein refers to a C1-C6 alkoxy group with one or more H groups substituted by a halogen, wherein "C1-C6 alkoxy" and "halogen" are as defined above. Specifically, it includes C1-C3 haloalkoxy and C2-C4 haloalkoxy groups, such as difluoromethoxy, trifluoromethoxy, and 2,2,2-trifluoroethoxy.

[0060] Unless otherwise specified, in this application, the term "C2-C6 alkenyl" refers to a straight-chain or branched monovalent hydrocarbon group containing 2 to 6 carbon atoms and having at least one unsaturated carbon-carbon double bond, specifically including C2-C5 alkenyl, C2-C4 alkenyl, such as ethylene, propylene, n-butene, isobutene, n-pentene, isopentene, etc.

[0061] Unless otherwise specified, in this application, the term "C2-C6 ester group" refers to -COO-C1-C6 alkyl, wherein "C1-C6 alkyl" is as described above. Specifically, it includes C2-C5 ester groups and C2-C4 ester groups, such as -COOCH3, -COOCH2CH3, etc.

[0062] [Secondary battery]

[0063] 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.

[0064] 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.

[0065] [Non-aqueous electrolyte for secondary batteries]

[0066] One embodiment of the present application provides a non-aqueous electrolyte for a secondary battery, comprising an additive and a non-aqueous solvent, wherein the non-aqueous solvent comprises dimethyl carbonate;

[0067] The additive comprises a cyclic sulfate compound represented by formula (I),

[0068] 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 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, for example, 0, 1 or 2;

[0069] R 5 and R 6 are each independently selected from any one of 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, for example, 0, 1 or 2;

[0070] R 1 and R 2 are not hydrogen atoms and R 3 and R 4 Not all hydrogen atoms at the same time;

[0071] Or, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0072] 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 at the same time;

[0073] Or, R 1 、R 2 、R 3 、R 4 、R 5 and R 6 The following conditions are met:

[0074] 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.

[0075] Although the mechanism is still unclear, the applicant unexpectedly discovered that: the present application forms a non-aqueous electrolyte by combining dimethyl carbonate and additives; the electrolyte of the present application has better high-voltage resistance. During the first charging process of the battery, the additive forms a more stable inorganic and organic mixed CEI film with stronger electron blocking ability on the surface of the positive electrode, which inhibits the side reaction between the electrolyte and the positive electrode, improves the DCR of the battery, improves the cycle performance and storage performance of the battery, and reduces the cycle gas production of the battery; dimethyl carbonate can reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and thereby improve the rate performance of the battery.

[0076] In some embodiments, the cyclic sulfate compound has a structure shown in formula (I-1),

[0077] 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-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;

[0078] R 5 and R 6 Each is independently selected from any one of 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.

[0079] The cyclic sulfate rings in the general formula (I-1) are all five-membered rings, which can form denser CEI films. Compared to six-membered rings, these rings have greater ring tension, making them easier to form films at the positive electrode. Six-membered rings, on the other hand, have less ring tension and greater stability, but they form films more slowly at the positive electrode. Consequently, the efficiency of electron-blocking CEI films is lower, affecting their effectiveness.

[0080] In some embodiments, R 1 、R 2 、R3 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-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a C1-C3 haloalkoxy group and a cyano group; R 5 and R 6 Each is independently selected from any one of 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 and a cyano group;

[0081] Optionally, 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-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group and a cyano group; R 5 and R 6 Each is independently selected from any one of a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group and a cyano group;

[0082] More optionally, 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 F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group; R 5 and R 6 Each is 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, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group;

[0083] Further optionally, the group of the structure represented by the general formula (II-1) is selected from any one of the following groups:

[0084] Wherein, X is a F atom, a Cl atom or a Br atom.

[0085] In some embodiments, 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, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group, wherein X is a F atom;

[0086] Optionally, R 1 、R 2 、R 3 and R 4 Each independently selected from Any one of a hydrogen atom, a F atom, a methyl group, an ethyl group, a propyl group, a trifluoromethyl group, an ethoxy group and a cyano group, wherein X is a F atom.

[0087] In some embodiments, the cyclic sulfate compound is selected from the following compounds:

[0088] The preparation method of the cyclic sulfate ester compound is simple, which is conducive to industrial promotion and implementation, and has a more stable effect on improving the cycle performance of batteries. The numbering of the above compounds is shown in the table below.

[0089] 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:

[0090] 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. 1 、R 2 、R 3 、R 4 , n1, and n2 are defined as described above.

[0091] In some embodiments, the mass content of the additive in the non-aqueous electrolyte is 0.001%-15%, optionally 0.005%-10%, and more optionally 0.05%-5%, for example, 0.001%, 0.003%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1%, 2%, 3%, 5%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 15% and the range consisting of any of the above values.

[0092] When the mass content of the additive in the non-aqueous electrolyte is within the above range, the high-voltage resistance of the electrolyte can be further improved, and the stability and electron-blocking ability of the positive electrode CEI film can be further improved to inhibit the side reaction between the electrolyte and the positive electrode, thereby improving the DCR of the battery, improving the cycle performance and storage performance of the battery, and reducing the cycle gas production of the battery.

[0093] In some embodiments, the mass content of dimethyl carbonate in the non-aqueous solvent is 5%-80%, optionally 10%-70%, and more optionally 20%-50%, for example, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% and the range consisting of any of the above values.

[0094] The mass content of dimethyl carbonate in the non-aqueous solvent is within the above range, which can further improve the DCR of the battery, improve the cycle performance and storage performance of the battery, reduce the cycle gas production of the battery, and further reduce the viscosity of the electrolyte, increase the conductivity of the electrolyte, and thus improve the rate performance of the battery.

[0095] In some embodiments, the electrolyte includes an electrolyte salt and an additional solvent.

[0096] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0097] In some embodiments, the other solvents may be selected from at least one of, for example, ethylene carbonate, propylene 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, and diethyl sulfone.

[0098] In some embodiments, the electrolyte may optionally include other additives. For example, the other additives may include negative electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0099] [Positive electrode]

[0100] 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, wherein the positive electrode film layer includes a positive electrode active material.

[0101] 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.

[0102] In some embodiments, the resistance of the positive electrode plate is less than or equal to 15Ω, and can be optionally less than or equal to 8Ω, for example, 0.5Ω, 1Ω, 2Ω, 3Ω, 4Ω, 5Ω, 6Ω, 8Ω, 9Ω, 10Ω, 11Ω, 12Ω, 13Ω, 14Ω, 15Ω and a range consisting of any of the above values.

[0103] As a result, while improving the stability and safety of the battery system, the battery has good kinetic performance, improves the DCR of the battery, improves the cycle performance and storage performance of the battery, reduces the cycle gas production of the battery, and improves the rate performance of the battery.

[0104] In some embodiments, the resistance of the positive electrode plate is tested using conventional methods in the art. For example, the test is performed using the following method:

[0105] The secondary battery was charged at a constant current of 0.33C to a full charge voltage of 4.3V, and then charged at a constant voltage of full charge voltage to a cutoff current of 0.055C, so that the secondary battery reached a fully charged state; the secondary battery was disassembled to obtain the positive electrode sheet; the positive electrode sheet was placed in a 140°C oven for 60 minutes, then cooled to 25°C, sealed and transferred for testing;

[0106] Use a diaphragm resistance tester (such as BER1200 model) to test the resistance of the positive electrode sheet at 25°C. The test conditions are: the pressure head area is 153.94mm 2 , pressure 3.5t, hold time 50s. Test multiple points on the electrode (for example, 15), with adjacent test points separated by 2mm to 3mm, record the resistance of all test points, and calculate the average value to be the positive electrode sheet resistance R.

[0107] 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.).

[0108] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that 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.

[0109] In some embodiments, the positive electrode active material includes Li 1+x Ni a Co b M 1-a-b O 2- y A y; wherein, M includes one or more elements of Mn, Fe, Cr, Ti, Zn, V, Al, Zr, Ce, Mg, Ga, Cu, Nb, and may be optionally one or two elements including Mn and Al; A includes one or more elements of S, F, Cl, I, and may be optionally one or two elements including S and F; -0.1 ≤ x ≤ 0.2; 0 < a < 1, may be optionally 0.5 ≤ a < 1, more optionally 0.7 ≤ a ≤ 0.9; 0 < b < 1, may be optionally 0 < b < 0.5, more optionally 0 < b ≤ 0.2; 0 < a + b < 1; 0 ≤ y < 0.2.

[0110] 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), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer, tetrafluoroethylene - hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0111] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an 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.

[0112] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N - methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0113] [Negative electrode plate]

[0114] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0115] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0116] In some embodiments, the volume - average particle size Dv50 of the negative electrode active material is 3 - 30 μm, may be optionally 6 - 20 μm, more optionally 8 - 15 μm, such as 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13 μm, 15 μm, 17 μm, 18 μm, 20 μm, 21 μm, 22 μm, 23 μm, 25 μm, 27 μm, 28 μm, 30 μm and the range composed of any of the above values.

[0117] The volume average particle size Dv50 of the negative electrode active material meets the above range, which is conducive to forming a stable SEI film on the negative electrode surface and reducing the side reaction between the electrolyte and the negative electrode active material, reducing the cycle gas production of the battery, improving the cycle performance and storage performance of the battery, improving the DCR of the battery, and helping to reduce the polarization degree of the battery and improve the capacity of the battery.

[0118] The volume average particle size Dv50 represents the particle size corresponding to the cumulative volume distribution percentage of the negative electrode active material reaching 50%. In some embodiments, the volume average particle size Dv50 is measured using instruments and methods known in the art. For example, it can be measured using a laser particle size analyzer (e.g., Master Size 300) in accordance with the particle size distribution laser diffraction method specified in GB / T 19077-2016.

[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 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).

[0122] 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.

[0123] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0124] 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.

[0125] [Isolation film]

[0126] 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.

[0127] 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.

[0128] 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.

[0129] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0130] 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.

[0131] 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.

[0132] In some embodiments, referring to FIG2 , the outer package 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] In addition, the present application also provides an electrical 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 electrical device, or as an energy storage unit for the electrical device. The electrical 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.

[0139] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0140] 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.

[0141] [Example]

[0142] 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.

[0143] Table 1

[0144] Preparation Example 1: Compound 1 Synthesis

[0145] 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.

[0146] Step 2: 184.2 g (0.8 mol) of intermediate product 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 a white powder solid, which was the above-mentioned compound 1.

[0147] 1H-NMR, CD3CN, δppm 5.42-5.39(m,2H), 5.36-5.34(m,2H), 1.67-1.65(d,6H).

[0148] Preparation Example 2: Compound 2 Synthesis

[0149] 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.

[0150] Step 2: To a 3L three-necked flask was added 216.2 g (0.8 mol) of intermediate 1, 1000 mL of acetonitrile was added, and 80 mg of ruthenium trichloride trihydrate catalyst was added. 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. 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 2.

[0151] Preparation Example 3: Compound 3 Synthesis

[0152] 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.

[0153] 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%).

[0154] Preparation Example 4: Compound 9 Synthesis

[0155] use (CAS No.: 7460-93-7) was used to replace 1,6-dideoxygalactitol, and the rest was the same as in Preparation Example 1. Compound LC-MS: 285.25.

[0156] Preparation Example 5: Compound 11 Synthesis

[0157] 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.

[0158] Step 2: To a 4L three-necked flask, 140g (0.4mol) of intermediate 1 was added, 1000mL of acetonitrile was added, 110mg 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 1500g 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 the acetonitrile crystals were obtained to obtain compound 11.

[0159] Preparation Example 6: Compound 14 Synthesis

[0160] 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.

[0161] 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 completed, 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 14.

[0162] The preparation methods of compounds 4 to 8, compound 10, and compounds 12 to 13 can refer to the above-mentioned preparation examples and the preparation methods of the compounds of the general formula.

[0163] Example 1

[0164] (1) Preparation of an electrolyte: Dimethyl carbonate, ethylene carbonate, and ethyl methyl carbonate solvents were mixed, with dimethyl carbonate accounting for 40% by mass of the total solvent mass and the mass ratio of ethylene carbonate to ethyl methyl carbonate being 3:7. Then, the additive compound 1 and the electrolyte salt LiPF6 were uniformly dissolved in the above solution to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L, and the mass content of compound 1 was 2%.

[0165] (2) Preparation of negative electrode sheets: The negative electrode active material graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC-Na) are dissolved in the solvent deionized water in a weight ratio of 90:4:4:2, and mixed evenly to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil once or multiple times, and the negative electrode sheets are obtained after drying, cold pressing, and slitting.

[0166] (3) Preparation of positive electrode sheet: positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and are fully stirred and mixed to obtain a 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 a positive electrode sheet.

[0167] (4) Isolation film: Conventional polypropylene film is used as the isolation film.

[0168] (5) Secondary battery assembly: 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 layer, and then wound to obtain an electrode assembly; the electrode assembly is placed in a battery case, dried, and then injected with electrolyte, and then subjected to formation, standing, and other processes to obtain a secondary battery.

[0169] The secondary battery preparation methods of Examples 2-30 and Comparative Examples 1-2 are similar to those of Example 1, and the different product parameters are detailed in Table 2. The resistance of the positive electrode sheet is adjusted by the mass ratio of the conductive agent to the positive electrode active material.

[0170] Table 2: Parameter results of Examples 1-30 and Comparative Examples 1-2

[0171] Material testing and battery testing

[0172] (1) Test of volume average particle size Dv50:

[0173] According to GB / T 19077-2016 “Particle size distribution by laser diffraction method”, the particle size was determined using a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.

[0174] (2) Test of positive electrode sheet resistance:

[0175] The secondary battery was charged at a constant current of 0.33C to a full charge voltage of 4.3V, and then charged at a constant voltage of full charge voltage to a cutoff current of 0.055C, so that the secondary battery reached a fully charged state; the secondary battery was disassembled to obtain the positive electrode sheet; the positive electrode sheet was placed in a 140°C oven for 60 minutes, then cooled to 25°C, sealed and transferred for testing;

[0176] The resistance of the positive electrode sheet at 25°C was tested using a BER1200 diaphragm resistance tester. The test conditions were: the pressure head area was 153.94 mm 2 , pressure 3.5t, hold time 50s. Test 15 points on the electrode, with adjacent test points separated by 2mm to 3mm, record the resistance of all test points, and calculate the average value to be the positive electrode sheet resistance R.

[0177] (3)DCR test:

[0178] At room temperature, the secondary battery is charged to 4.3V at a constant current of 1C, then charged to a current of 0.05C at a constant voltage of 4.3V, left to stand for 5 minutes, discharged at 1C for 30 minutes (the battery cell is charged to 50% SOC at this time), and then left to stand for 5 minutes. Adjust the temperature to 25°C, let it stand for 1 hour, record the voltage V1 of the battery cell at this time, discharge at 4C for 30 seconds, and record the voltage V2 after pulse discharge. Calculate the DCR of the battery cell when it is discharged at 50% SOC for 30 seconds according to the following formula;

[0179] DCR when discharging for 30 seconds at 50% SOC = (V1-V2) / I, where I = 4C.

[0180] (4) Cyclic performance test:

[0181] Four secondary batteries in each group of the examples and comparative examples were taken, and the secondary batteries were repeatedly charged and discharged through the following steps. The discharge capacity retention rates of the secondary batteries were calculated and the average value was taken.

[0182] At 45°C, the secondary battery was first fully discharged at 1C before testing. The test process was as follows: At 45°C, the secondary battery was charged at a constant current of 1C to a voltage of 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current of 0.5C to a voltage of 3.0V. This constituted one charge-discharge cycle, and the discharge capacity at this time was recorded as the discharge capacity of the first cycle. The charge and discharge cycle was then repeated, and the discharge capacity of the 400th cycle was recorded. The capacity retention rate after 400 cycles was calculated according to the following formula: 400-cycle capacity retention rate = (discharge capacity of the 400th cycle / discharge capacity of the first cycle) × 100%.

[0183] (5) Storage performance test:

[0184] At 25°C, the secondary battery was first charged to 4.3V at a constant current of 0.5C, then charged at a constant voltage of 4.3V with a cutoff current of 0.05C. The battery was then discharged to 3.0V at a constant current of 0.5C, and the discharge capacity was recorded. This discharge capacity was recorded as the initial capacity C0. The secondary battery was then charged to 4.3V at a constant current of 0.5C, and then charged at a constant voltage of 4.3V with a cutoff current of 0.05C. The secondary battery was then placed in a 60°C constant temperature box for storage for 15 days. After storage, the battery was removed and discharged again at a constant current of 0.5C to 3.0V. The discharge capacity after storage was recorded, C1. The remaining capacity of the battery after 15 days of constant temperature storage at 60°C was calculated according to the following formula: Remaining capacity after 15 days of constant temperature storage at 60°C = 100% × C1 / C0.

[0185] (6) 45℃ cyclic gas production test:

[0186] At 45°C, the secondary battery was fully discharged at 1C and then tested. The test process is as follows: at 45°C, the secondary battery was charged at a constant current of 1C to a voltage of 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C. After standing for 5 minutes, the lithium-ion battery was discharged at a constant current of 0.5C to a voltage of 3.0V. This is a charge and discharge cycle process, and the discharge capacity at this time is recorded as the discharge capacity of the first cycle; then the charge and discharge cycle was repeated for a total of 400 cycles. The volume V1 of the battery before high-temperature cycling was measured using the drainage method. After the cycle was completed, the battery was removed and the volume V2 of the battery after cooling for 8 hours was measured. The volume expansion rate of the battery after 400 cycles was calculated according to the following formula; The volume expansion rate of the battery after 400 cycles = (V2 / V1-1)×100%.

[0187] The results of items (1) to (2) above are shown in Table 1, and the results of items (3) to (6) are shown in Table 3.

[0188] Table 3: Performance test results of Examples 1-30 and Comparative Examples 1-2

[0189] According to the above results, we can know that:

[0190] Compared with Comparative Example 1, the batteries of Examples 1-10 of the present application showed improved DCR, higher cycle performance, and lower cycle gas production. Compared with Comparative Example 2, the batteries of Examples 11-13 of the present application showed improved DCR, higher cycle performance, higher storage performance, and lower cycle gas production. This demonstrates that the use of the non-aqueous electrolyte of the present application can improve the DCR of batteries, enhance the cycle performance and storage performance of batteries, and reduce the cycle gas production of batteries.

[0191] Compared with Example 23, the DCR of the batteries of Examples 1 and 15-16 of the present application is improved, the cycle performance is higher, the storage performance is higher, and the cycle gas production is lower.

[0192] Compared with Examples 25-26, the battery cells of Examples 1 and 17-18 of the present application have higher cycle performance and lower cycle gas production. In addition, the DCR performance of the battery cells of Examples 1 and 17-18 of the present application is better than that of the battery of Example 25.

[0193] Compared with Example 27, the DCR of the batteries of Examples 1, 19-20 of the present application is improved, the cycle performance is higher, the storage performance is higher, and the cycle gas production is lower.

[0194] Compared with Example 28, the batteries of Examples 1 and 21-22 of the present application have higher cycle performance, higher storage performance, and lower cycle gas production. Compared with Example 29, the DCR of the batteries of Examples 1 and 21-22 of the present application is improved. Compared with Example 30, the battery of Example 1 of the present application has improved DCR, higher cycle performance, higher storage performance, and lower cycle gas production.

[0195] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A non-aqueous electrolyte for a secondary battery, comprising an additive and a non-aqueous solvent, wherein the non-aqueous solvent comprises dimethyl carbonate; The additive comprises a cyclic sulfate compound represented by formula (I), in, R 1 , R 2 , R 3 and R 4 Each is independently selected from any one of a group having a structure represented by 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, R 5 and R 6 Each is independently selected from any one of 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; 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 a group having a structure represented by the general formula (II), a halogen atom, a C1-C6 alkyl group, a C1-C6 alkyl halide any one of 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.

2. The non-aqueous electrolyte for secondary batteries according to claim 1, wherein The cyclic sulfate compound has a structure shown in 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; R 5 and R 6 Each is independently selected from any one of 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.

3. The non-aqueous electrolyte for a secondary battery according to claim 2, wherein 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-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group, a C1-C3 haloalkoxy group and a cyano group; R 5 and R 6 Each is independently selected from any one of 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 and a cyano group; Optionally, R 1 , R 2 , R 3 and R 4 Each independently selected from a group having a structure represented by the general formula (II-1), a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1- Any one of C3 alkoxy and cyano; R 5 and R 6 Each is independently selected from any one of a hydrogen atom, a halogen atom, a C1-C3 alkyl group, a C1-C3 haloalkyl group, a C1-C3 alkoxy group and a cyano group; More optionally, 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 F atom, a Cl atom, a Br atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group; R 5 and R 6 Each is 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, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group; Further 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.

4. The nonaqueous electrolyte for a secondary battery according to any one of claims 1 to 3, wherein 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, an isopropyl group, a trifluoromethyl group, an ethoxy group and a cyano group, and X is a F 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 methyl group, an ethyl group, a propyl group, a trifluoromethyl group, an ethoxy group and a cyano group, wherein X is a F atom.

5. The nonaqueous electrolyte for a secondary battery according to any one of claims 1 to 4, wherein The cyclic sulfate compound is selected from the following compounds:

6. The non-aqueous electrolyte for a secondary battery according to any one of claims 1 to 5, wherein The mass content of the additive in the non-aqueous electrolyte is 0.001%-15%, optionally 0.005%-10%, and more optionally 0.05%-5%.

7. The nonaqueous electrolyte according to any one of claims 1 to 6, wherein The mass content of the dimethyl carbonate in the non-aqueous solvent is 5%-80%, optionally 10%-70%, and more optionally 20%-50%.

8. A secondary battery, comprising the non-aqueous electrolyte for a secondary battery according to any one of claims 1 to 7, a positive electrode sheet and a negative electrode sheet, wherein the negative electrode sheet comprises a negative electrode active material; optionally, the secondary battery is a lithium secondary battery.

9. The secondary battery according to claim 8, wherein The resistance of the positive electrode plate is less than or equal to 15Ω, and can be optionally less than or equal to 8Ω.

10. The secondary battery according to claim 8 or 9, wherein: The volume average particle size Dv50 of the negative electrode active material is 3-30 μm, optionally 6-20 μm, and more optionally 8-15 μm.

11. The secondary battery according to any one of claims 8 to 10, wherein The positive electrode sheet includes a positive electrode active material; Optionally, the positive electrode active material includes Li 1+x Ni a Co b M 1-a-b O 2-y A y ; wherein, M includes one or more elements selected from Mn, Fe, Cr, Ti, Zn, V, Al, Zr, Ce, Mg, Ga, Cu, Nb, and is optionally one or two elements selected from Mn, Al; A includes one or more elements selected from S, F, Cl, I, and is optionally one or two elements selected from S, F; -0.1 ≤ x ≤ 0.2; 0 < a < 1, is optionally 0.5 ≤ a < 1, more optionally 0.7 ≤ a ≤ 0.9; 0 < b < 1, is optionally 0 < b < 0.5, more optionally 0 < b ≤ 0.2; 0 < a + b < 1; 0 ≤ y < 0.

2. 12 . An electrical device comprising the nonaqueous electrolyte for a secondary battery according to claim 1 or the secondary battery according to claim 8 .

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