Electrolyte, secondary battery, and electric device

Abstract

An electrolyte, a secondary battery, and an electric device. The electrolyte comprises a component, a nitrile solvent. The nitrile solvent comprises a compound represented by formula (1): wherein: L is selected from any one of C(R1R2), O, Si(R3R4), B(R5), P(R6R7R8), and N(R9); R1-R9 are each independently selected from at least one of H, halogen, substituted or unsubstituted alkyl having 1-3 carbon atoms, alkoxy having 1-3 carbon atoms, amino, and cyano, and R1 and R2 are not cyanos and H; R11 is an alkane chain containing 1-4 carbon atoms; R12-R14 are each independently selected from at least one of H, halogen, substituted or unsubstituted alkyl having 1-3 carbon atoms, alkoxy having 1-3 carbon atoms, amino, and cyano; and when L is C(R1R2), R12-R14 are not cyanos.

Description

Electrolyte, secondary battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202311191041.9 filed on September 15, 2023, entitled “Electrolyte, Secondary Battery and Electrical Device,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an electrolyte, a secondary battery, and an electrical device. Background Art

[0004] Secondary batteries such as lithium batteries are increasingly widely used due to their clean and renewable characteristics. Lithium-ion secondary batteries have been widely used in many fields such as consumer electronics, electric vehicles and energy storage.

[0005] With the rapid development of the new energy industry, people are increasingly demanding new energy vehicles such as electric vehicles and electric bicycles, and their performance requirements are also becoming increasingly higher. The energy density of traditional secondary batteries has almost reached its theoretical limit. To meet the needs of future applications such as long-range electric vehicles and electric aircraft, lithium-ion secondary batteries with higher energy density have been developed. However, the lithium metal anode in lithium-ion secondary batteries is highly reactive and easily reacts with the electrolyte, resulting in reduced mechanical strength and chemical stability of the solid electrolyte interface (SEI) layer formed. This can trigger dendrite growth, deplete the lithium source, reduce battery life, and pose safety risks.

[0006] Therefore, the traditional technology needs to be further improved.

[0007] Summary of the Invention

[0008] According to various embodiments of the present application, the present application provides an electrolyte, a secondary battery, and an electrical device, aiming to improve the cycle performance of the battery.

[0009] This application is achieved through the following technical solutions.

[0010] In a first aspect of the present application, an electrolyte is provided, wherein the components of the electrolyte include a nitrile solvent, and the nitrile solvent includes a compound represented by formula (1):

[0011] wherein L is selected from any one of C(R1R2), O, Si(R3R4), B(R5), P(R6R7R8), and N(R9); R1 to R9 are independently selected from any one of H, halogen, substituted or unsubstituted alkyl having 1 to 3 carbon atoms, alkoxy having 1 to 3 carbon atoms, amino, and cyano; and R1 and R2 are not cyano;

[0012] R 11 It is an alkane chain containing 1 to 4 carbon atoms;

[0013] R 12 ~R 14 are independently selected from any one of H, halogen, substituted or unsubstituted alkyl with 1 to 3 carbon atoms, alkoxy with 1 to 3 carbon atoms, amino and cyano; and when L is selected from C(R1R2), R 12 ~R 14 Not cyano.

[0014] The electrolyte contains a nitrile solvent with a specific structure. The compound represented by formula (1) contains an alkyl chain. When L is selected from O, Si(R3R4), B(R5), P(R6R7R8), and N(R9), the alkyl carbon chain is separated from the cyano group by these groups, thereby reducing the activity of the groups on the alkyl chain and improving the redox stability of the nitrile solvent. When L is selected from C(R1R2), that is, when the cyano group is directly connected to the alkyl chain, the groups of R1 and R2 are regulated so that R1 and R2 are not cyano and H, and R 12 ~R 14 It is not a cyano group, thereby reducing the reactivity of the carbon atom directly connected to the cyano group to maintain good redox stability; in this way, the compound represented by formula (1) with the specific structure can have good solubility for electrolyte salts and good oxidation stability. When used in the preparation of secondary batteries, especially lithium metal secondary batteries, the probability of corrosion of the anode metal can be reduced, thereby improving the cycle performance of the battery.

[0015] In some embodiments, the nitrile solvent includes a compound represented by formula (1-1):

[0016] In some embodiments, L is selected from any one of C(R1R2), Si(R3R4) and N(R9).

[0017] When L is selected from C(R1R2), Si(R3R4) and N(R9), the compound represented by formula (1) can simultaneously take into account a wider melting and boiling point range, higher redox stability and excellent lithium salt solubility.

[0018] In some embodiments, the compound represented by formula (1) satisfies at least one of the following conditions (1) to (3):

[0019] (1) R1 to R9 are independently selected from any one of halogen, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, an alkoxy group having 1 to 3 carbon atoms, and a cyano group;

[0020] (2) R1 and R2 are not H at the same time, R3 and R4 are not H at the same time, R6, R7 and R8 are not H at the same time, and R5 and R9 are not H;

[0021] (3)R 12 ~R 14 Each of them is independently selected from any one of H, halogen, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, an alkoxy group having 1 to 3 carbon atoms, and a cyano group.

[0022] In some embodiments, the nitrile solvent includes at least one of the compounds represented by formula (1a) to formula (1f):

[0023] Among them, each R a1 , each R b1 , each R c1 , each R d1 , each R e1 and each R f1 are independently selected from any one of H, halogen, alkyl having 1 to 3 carbon atoms, alkyl having 1 to 3 carbon atoms substituted by halogen, alkoxy having 1 to 3 carbon atoms, and cyano, and each R a1 None of them are cyano groups;

[0024] Each R a2 , each R b2 , each R c2 , each R d2 and each R e2 Each independently selected from the group consisting of halogen, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0025] In some embodiments, the nitrile solvent satisfies at least one of the following conditions (1) to (6):

[0026] (1) At least one R a2 is an alkoxy group having 1 to 3 carbon atoms;

[0027] (2) Each R b2 Each of the following groups is independently selected from an alkyl group having 1 to 3 carbon atoms and an alkoxy group having 1 to 3 carbon atoms;

[0028] (3) Each R c1 are independently selected from alkyl groups having 1 to 3 carbon atoms;

[0029] (4) Each R d1 are independently selected from alkyl groups having 1 to 3 carbon atoms;

[0030] (5) Each R e1 are independently selected from alkoxy groups having 1 to 3 carbon atoms;

[0031] (6) Each R f1 Each is independently selected from any one of H and an alkyl group having 1 to 2 carbon atoms.

[0032] In some embodiments, the nitrile solvent includes at least one of the compounds represented by formula (11) to formula (58):

[0033] In some embodiments, the electrolyte solution further comprises an electrolyte salt, and the molar volume ratio of the electrolyte salt to the nitrile solvent is 1 mol / L to 15 mol / L.

[0034] In some embodiments, the electrolyte salt satisfies at least one of the following conditions (1) to (2):

[0035] (1) The molar volume ratio of the electrolyte salt to the nitrile solvent is 2 mol / L to 12 mol / L;

[0036] (2) The electrolyte salt includes a lithium ion electrolyte salt.

[0037] In some embodiments, the components of the electrolyte further include a film-forming additive, and the film-forming additive includes an unsaturated cyclic carbonate film-forming additive;

[0038] Unsaturated ester film-forming additives are more conducive to the formation of a dense negative electrode SEI film during the charge and discharge process of secondary batteries, further inhibiting the corrosion of lithium metal by the electrolyte.

[0039] In some embodiments, the molar ratio of the film-forming additive to the nitrile solvent is (0.05-0.5):1.

[0040] In some embodiments, the film-forming additive includes at least one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, propylene sulfate, and vinyl sulfite.

[0041] According to a second aspect of the present application, a secondary battery is provided, wherein the secondary battery includes the electrolyte according to the first aspect.

[0042] In some embodiments, the secondary battery comprises a lithium metal secondary battery.

[0043] The above-mentioned secondary battery has excellent cycle performance.

[0044] According to a third aspect of the present application, an electric device is provided, wherein the electric device comprises the secondary battery according to the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces 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 those skilled in the art, other drawings can be obtained based on the drawings without inventive work. In the drawings:

[0046] FIG1 is a schematic diagram of an embodiment of a battery cell;

[0047] Figure 2 is an exploded view of Figure 1;

[0048] FIG3 is a schematic diagram of an embodiment of a battery pack;

[0049] FIG4 is an exploded view of FIG3 ;

[0050] FIG5 is a schematic diagram of an embodiment of an electric device using a battery as a power source.

[0051] Explanation of the accompanying reference numerals: 1. battery pack; 2. upper case; 3. lower case; 4. battery cell; 41. shell; 42. electrode assembly; 43. cover plate; 5. electrical device. DETAILED DESCRIPTION

[0052] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0053] In the description of the embodiments of the present application, “multiple” means two or more, unless otherwise clearly and specifically defined.

[0054] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0055] In this application, the term "alkyl" refers to a group formed when an alkane loses a hydrogen, such as methane loses a hydrogen to form a methyl group; "alkenyl or alkynyl" refers to a group formed when an alkene or alkyne loses a hydrogen, such as ethylene loses a hydrogen to form vinyl, and acetylene loses a hydrogen to form ethynyl.

[0056] In the present application, the number of carbon atoms in the "alkyl group having 1 to 3 carbon atoms" may be 1 to 3, including 1, 2, and 3. Non-limiting examples include methane, ethyl, and n-propane.

[0057] In the present application, the term "substituted or unsubstituted" means that the functional group described after the term may or may not have a substituent.

[0058] "Alkoxy" refers to a group with the structure -OR, where R is an alkyl group, i.e., an alkyl group as defined above attached to the adjacent group via an oxygen atom. Phrases containing this term, for example, "alkoxy having 1-3 carbon atoms," refer to groups where the alkyl portion contains 1-3 carbon atoms. Examples of alkoxy groups include, but are not limited to, methoxy (-O-CH or -OMe) and ethoxy (-O-CHCH or -OEt).

[0059] In the present application, the halogen group includes chlorine, fluorine, bromine, and iodine.

[0060] In this application, R 11 is selected from an alkane chain containing 1 to 4 carbon atoms, which means R 11 The residues are selected from the residues formed by the loss of any three H atoms from alkanes containing 1 to 4 carbon atoms. In other words, in the compound represented by formula (1), the loss of any three H atoms from alkanes containing 1 to 4 carbon atoms is replaced by R 12 、R 13 and R 14 replace.

[0061] In traditional technology, acetonitrile solvents are often used as electrolyte additives for secondary batteries to improve battery performance. However, studies have found that acetonitrile solvents are too active and easily react with the lithium metal in lithium metal secondary batteries, thereby corroding the lithium metal.

[0062] In traditional technology, in order to reduce the corrosion degree of acetonitrile solvents on lithium metal, diluents are often added to the electrolyte to dilute the concentration of acetonitrile solvents.

[0063] However, research has found that adding diluents to the electrolyte to dilute the concentration of acetonitrile solvents can only reduce the degree of corrosion of acetonitrile solvents on lithium metal in a relatively short period of time. When used to prepare lithium metal batteries, acetonitrile solvents are still prone to corrode lithium metal during long-term cyclic charging and discharging processes, and cannot fundamentally and substantially improve the cycle life of lithium metal secondary batteries.

[0064] Based on this, we explored the essential structure of acetonitrile solvents and found that the type and position of substituents in acetonitrile solvents are closely related to the redox stability of acetonitrile solvents.

[0065] Therefore, one embodiment of the present application provides an electrolyte, wherein the components of the electrolyte include a nitrile solvent, and the nitrile solvent includes a compound represented by formula (1):

[0066] wherein L is selected from any one of C(R1R2), O, Si(R3R4), B(R5), P(R6R7R8), and N(R9); R1 to R9 are independently selected from any one of H, halogen, substituted or unsubstituted alkyl having 1 to 3 carbon atoms, alkoxy having 1 to 3 carbon atoms, amino, and cyano; and R1 and R2 are not cyano and H;

[0067] R 11 It is an alkane chain containing 1 to 4 carbon atoms.

[0068] R 12 ~R 14 are independently selected from any one of H, halogen, substituted or unsubstituted alkyl with 1 to 3 carbon atoms, alkoxy with 1 to 3 carbon atoms, amino and cyano; and when L is selected from C(R1R2), R 12 ~R 14 Not cyano.

[0069] The above electrolyte contains a nitrile solvent with a specific structure. The compound represented by formula (1) contains an alkyl chain. When L is selected from O, Si(R3R4), B(R5), P(R6R7R8), and N(R9), the carbon chain is separated from the cyano group by these groups, thereby reducing the activity of the groups on the alkyl chain and improving the redox stability of the nitrile solvent. Among them, O, Si, B, P, and N can all form a relatively stable connection with the cyano group, and Si can also provide an empty orbital so that Si can form a more stable electronic structure with the cyano group, thereby reducing the activity of the groups on the alkyl chain.

[0070] When L is selected from C(R1R2), that is, when the cyano group is directly connected to the alkyl chain, the groups of R1 and R2 are adjusted so that R1 and R2 are not cyano and H, and R 12 ~R 14 It is not a cyano group, thereby reducing the reactivity of the carbon atom directly connected to the cyano group to maintain good redox stability; in this way, the compound represented by formula (1) with the specific structure can have good solubility for electrolyte salts and good oxidation stability. When used in the preparation of secondary batteries, especially lithium metal secondary batteries, the probability of corrosion of the anode metal can be reduced, thereby improving the cycle performance of the battery.

[0071] In some embodiments, the nitrile solvent includes a compound represented by formula (1-1):

[0072] In some embodiments, L is selected from any one of C(R1R2), Si(R3R4) and N(R9).

[0073] When L is selected from C(R1R2), Si(R3R4) and N(R9), the compound represented by formula (1) can simultaneously take into account a wider melting and boiling point range, higher redox stability and excellent lithium salt solubility.

[0074] In some embodiments, R1-R9 are independently selected from any one of H, halogen, alkyl with 1-3 carbon atoms, alkyl with 1-3 carbon atoms substituted by halogen, alkoxy with 1-3 carbon atoms, and cyano.

[0075] In some embodiments, R1 to R9 are independently selected from any one of halogen, alkyl with 1 to 3 carbon atoms, alkyl with 1 to 3 carbon atoms substituted by halogen, alkoxy with 1 to 3 carbon atoms, and cyano.

[0076] In some embodiments, R1 and R2 are not H at the same time, R3 and R4 are not H at the same time, R6, R7 and R8 are not H at the same time, and R5 and R9 are not H.

[0077] In some embodiments, R1 and R2 are not H, R3 and R4 are not H, R6, R7 and R8 are not H, and R5 and R9 are not H.

[0078] Further regulating the structure of R1 to R9, relative to R1 to R9 being H, when R1 to R9 are independently selected from any one of halogen, alkyl group with 1 to 3 carbon atoms, alkyl group with 1 to 3 carbon atoms substituted by halogen, alkoxy group with 1 to 3 carbon atoms and cyano group, the nitrile solvent has higher redox stability.

[0079] In some embodiments, R1 to R9 are independently selected from any one of F, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by F, an alkoxy group having 1 to 3 carbon atoms, and a cyano group.

[0080] In some embodiments, R1-R9 are independently selected from any one of F, an alkyl group with 1-2 carbon atoms, an alkyl group with 1-2 carbon atoms substituted by F, an alkoxy group with 1-2 carbon atoms, and a cyano group.

[0081] In some embodiments, R1-R9 are independently selected from any one of F, an alkyl group with 1-2 carbon atoms, an alkyl group with 1-2 carbon atoms substituted by F, an alkoxy group with 1-2 carbon atoms, and a cyano group.

[0082] In some embodiments, R1 to R9 are independently selected from any one of F, methyl, ethyl, trifluoromethyl, methoxy, ethoxy and cyano.

[0083] In some embodiments, R 12 ~R 14 Each of them is independently selected from any one of H, halogen, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, an alkoxy group having 1 to 3 carbon atoms, and a cyano group.

[0084] In some embodiments, R 12 ~R 14 Each of them is independently selected from any one of H, halogen, alkyl group having 1 to 2 carbon atoms, alkyl group having 1 to 2 carbon atoms substituted with halogen, alkoxy group having 1 to 2 carbon atoms, and cyano group.

[0085] In some embodiments, R 12 ~R 14 Each independently selected from any one of H, F, an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with F, an alkoxy group having 1 to 2 carbon atoms, and a cyano group.

[0086] In some embodiments, R 12 ~R 14 Each independently selected from any one of H, F, an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with F, an alkoxy group having 1 to 2 carbon atoms, and a cyano group.

[0087] In some embodiments, R 12 ~R 14 Each is independently selected from any one of H, F, methyl, ethyl, trifluoromethyl, methoxy, ethoxy and cyano.

[0088] In some embodiments, the nitrile solvent comprises at least one of the compounds represented by formula (1a) to formula (1f):

[0089] Among them, each R a1 , each R b1 , each R c1 , each R d1 , each R e1 and each R f1are independently selected from any one of H, halogen, alkyl having 1 to 3 carbon atoms, alkyl having 1 to 3 carbon atoms substituted by halogen, alkoxy having 1 to 3 carbon atoms, and cyano, and each R a1 None of them are cyano groups.

[0090] Each R a2 , each R b2 , each R c2 , each R d2 and each R e2 Each independently selected from the group consisting of halogen, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0091] In some embodiments, each R a1 , each R b1 , each R c1 , each R d1 and each R e1 Each independently selected from an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0092] In some embodiments, each R a1 , each R b1 , each R c1 , each R d1 and each R e1 Each independently selected from any one of an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 2 carbon atoms.

[0093] In some embodiments, each R a1 , each R b1 , each R c1 , each R d1 and each R e1 Each independently selected from any one of an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with F, and an alkoxy group having 1 to 2 carbon atoms.

[0094] In some embodiments, each R a1 , each R b1 , each R c1 , each R d1 and each R e1 Each independently represents any one of methyl, ethyl, trifluoromethyl, methoxy and ethoxy.

[0095] In some embodiments, at least one R a2 It is an alkoxy group having 1 to 3 carbon atoms.

[0096] The study found that in formula (1a), when at least one R a2 In the case of an alkoxy group having 1 to 3 carbon atoms, the redox stability of the nitrile solvent is higher.

[0097] In some embodiments, at least one R a2 It is an alkoxy group having 1 to 2 carbon atoms.

[0098] In some embodiments, at least one R a2 The number of carbon atoms is methoxy or ethoxy.

[0099] In some embodiments, at least one R a2 It is an alkyl group having 1 to 3 carbon atoms.

[0100] In some embodiments, at least one R a2 It is an alkyl group having 1 to 2 carbon atoms.

[0101] In some embodiments, at least one R a2 The number of carbon atoms is methyl or ethyl.

[0102] In some embodiments, each R b2 Each independently selected from an alkyl group having 1 to 3 carbon atoms and an alkoxy group having 1 to 3 carbon atoms.

[0103] The study found that the regulation of R in formula (1b) b2 The structure can further improve the redox stability of nitrile solvents.

[0104] In some embodiments, each R b2 Each is independently selected from any one of an alkyl group having 1 to 2 carbon atoms and an alkoxy group having 1 to 2 carbon atoms.

[0105] In some embodiments, each R b2 Each of the carbon atoms is independently selected from any one of methyl, ethyl, methoxy and ethoxy.

[0106] In some embodiments, each R c1 Each is independently selected from an alkyl group having 1 to 3 carbon atoms.

[0107] The study found that the regulation of R in formula (1c) c1 The structure can further improve the redox stability of nitrile solvents.

[0108] In some embodiments, each R c1 Each is independently selected from an alkyl group having 1 to 2 carbon atoms.

[0109] In some embodiments, each R c1are independently selected from methyl or ethyl.

[0110] In some embodiments, each R c2 Each independently selected from any one of F, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0111] In some embodiments, each R c2 Each independently selected from any one of F, an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 2 carbon atoms.

[0112] In some embodiments, each R d1 Each is independently selected from an alkyl group having 1 to 3 carbon atoms.

[0113] The study found that the R d1 The structure can further improve the redox stability of nitrile solvents.

[0114] In some embodiments, each R d1 Each is independently selected from an alkyl group having 1 to 2 carbon atoms.

[0115] In some embodiments, each R d1 are independently selected from methyl or ethyl.

[0116] In some embodiments, each R d2 Each independently selected from any one of F, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0117] In some embodiments, each R d2 Each independently selected from any one of F, an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 2 carbon atoms.

[0118] In some embodiments, each R e1 Each is independently selected from an alkoxy group having 1 to 3 carbon atoms.

[0119] In some embodiments, each R e1 Each is independently selected from an alkoxy group having 1 to 2 carbon atoms.

[0120] In some embodiments, each R e1 are independently selected from methoxy or ethoxy.

[0121] The study found that the R e1The structure can further improve the redox stability of nitrile solvents.

[0122] In some embodiments, each R e2 Each independently selected from any one of F, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0123] In some embodiments, each R e2 Each independently selected from any one of F, an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 2 carbon atoms.

[0124] In some embodiments, each R f1 Each is independently selected from any one of H and an alkyl group having 1 to 2 carbon atoms.

[0125] The study found that the regulation formula (1f) R f1 The structure can further improve the redox stability of nitrile solvents.

[0126] In some embodiments, each R f1 Each is independently selected from any one of H, methoxy and ethoxy.

[0127] In some embodiments, each R f2 Each independently selected from any one of F, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 3 carbon atoms.

[0128] In some embodiments, each R f2 Each independently selected from any one of F, an alkyl group having 1 to 2 carbon atoms, an alkyl group having 1 to 2 carbon atoms substituted with a halogen, and an alkoxy group having 1 to 2 carbon atoms.

[0129] In some embodiments, the nitrile solvent includes at least one of the compounds represented by formula (11) to formula (58):

[0130] It should be noted that the compounds exemplified above are compounds with known structures in the art or compounds that can be obtained according to prior art records.

[0131] In some embodiments, the electrolyte solution further comprises an electrolyte salt, and the molar volume ratio of the electrolyte salt to the nitrile solvent is 1 mol / L to 15 mol / L.

[0132] Optionally, in the electrolyte solution, the molar volume ratio of the electrolyte salt to the nitrile solvent is 2 mol / L to 12 mol / L.

[0133] In the above “1mol / L to 15mol / L”, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 1mol / L, 2mol / L, 3mol / L, 4mol / L, 5mol / L, 6mol / L, 7mol / L, 8mol / L, 9mol / L, 10mol / L, 11mol / L, 12mol / L, 13mol / L, 14mol / L, 15mol / L; or a range consisting of any two values, for example, 1mol / L to 1 5mol / L, 1mol / L~10mol / L, 1mol / L~5mol / L, 2mol / L~15mol / L, 3mol / L~15mol / L, 4mol / L~15mol / L, 5mol / L~15mol / L, 6mol / L~15mol / L, 7mol / L~15mol / L, 8mol / L~15mol / L, 9mol / L~15mol / L, 10mol / L~15mol / L, 3mol / L~10mol / L, 4mol / L~10mol / L, 5mol / L~10mol / L.

[0134] In some embodiments, the electrolyte solution further comprises a film-forming additive.

[0135] In some embodiments, the film-forming additive includes an unsaturated ester film-forming additive; further, the unsaturated ester film-forming additive includes at least one of an unsaturated cyclic carbonate film-forming additive, an unsaturated carboxylic acid ester film-forming additive, and an unsaturated sulfate film-forming additive.

[0136] In some embodiments, the film-forming additive includes an unsaturated cyclic carbonate film-forming additive.

[0137] Unsaturated cyclic carbonate film-forming additives are more conducive to the formation of a dense negative electrode SEI film during the charge and discharge process of secondary batteries, further inhibiting the corrosion of lithium metal by the electrolyte.

[0138] It should be noted that the unsaturated cyclic carbonate film-forming additive refers to a film-forming additive containing a carbon-carbon double bond in the carbonate ring.

[0139] Specifically, the unsaturated cyclic carbonate film-forming additive has the following structure:

[0140] Here, Y1 and Y2 are each independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, and an alkenyl group having 2 to 5 carbon atoms.

[0141] In some embodiments, Y1 and Y2 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, and an alkenyl group having 2 to 5 carbon atoms.

[0142] In some embodiments, Y1 and Y2 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, and an alkenyl group having 2 to 3 carbon atoms.

[0143] In some embodiments, Y1 and Y2 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, and an alkenyl group having 2 to 3 carbon atoms.

[0144] In some embodiments, Y1 and Y2 are the same or different.

[0145] In some embodiments, the film-forming additive includes at least one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, propylene sulfate, and vinyl sulfite.

[0146] In some embodiments, the film-forming additive includes vinylene carbonate.

[0147] In some embodiments, the molar ratio of the film-forming additive to the nitrile solvent is (0.05-0.5):1.

[0148] In the above “(0.05~0.5):1”, the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 0.5:1, 0.4:1, 0.3:1, 0.2:1, 0.1:1, 0.09:1, 0.09:1, 0.08:1, 0.07:1, 0.06:1, 0.05:1; or a range consisting of any two numerical values, for example, it can be (0.08~0.5):1, (0.09~0.5):1, (0.1~0.5):1, (0.2~0.5):1, (0.3~0.5):1, (0.3~0.4):1, (0.1~0.4):1, (0.1~0.3):1, (0.2~0.4):1.

[0149] In some embodiments, the electrolyte further comprises a diluent.

[0150] The diluent helps to reduce the viscosity of the electrolyte and improve the ionic conductivity.

[0151] In some embodiments, the molar ratio of the diluent to the nitrile solvent is (0.5-5):1.

[0152] By regulating the molar ratio of the diluent to the nitrile solvent, the reduction stability of the electrolyte is further improved while maintaining good ionic conductivity of the electrolyte.

[0153] In the above "(0.5~5):1", the values ​​include the minimum and maximum values ​​of the range, and every value between the minimum and maximum values. Specific examples include but are not limited to the point values ​​in the embodiments and the following point values: 5:1, 4.5:1, 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, 0.5:1; or a range consisting of any two numerical values, for example, it can be (1~5):1, (2~5):1, (3~5):1, (2~4):1, (3~4):1.

[0154] In some embodiments, the diluent includes at least one of a fluorinated ether compound, an aromatic hydrocarbon solvent, and a fluorinated aromatic solvent.

[0155] In some embodiments, the diluent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1-(1,1,2,2-tetrafluoroethoxy)propane, 1,1,2,2-tetrafluoroethyl ethyl ether, benzene, and trifluoromethoxybenzene.

[0156] In some embodiments, the electrolyte salt may be selected from commonly used electrolyte salts in the art, such as lithium ion electrolyte salts, sodium ion electrolyte salts, and potassium ion electrolyte salts.

[0157] In some embodiments, the electrolyte salt includes a lithium ion electrolyte salt.

[0158] As an example, the lithium ion electrolyte salt includes, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0159] As an example, the sodium ion electrolyte salt includes, but is not limited to, one or more of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, and sodium bis(trifluoromethylsulfonyl)imide.

[0160] According to one embodiment of the present application, a secondary battery is provided. The secondary battery includes the electrolyte according to the first aspect.

[0161] In some embodiments, the secondary battery further includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0162] Positive electrode sheet: The positive electrode sheet includes a current collector and a positive electrode active layer loaded on the surface of the current collector.

[0163] The components of the positive electrode active layer include a positive electrode active material. The positive electrode active material can be selected from commonly used positive electrode active materials in the art, including but not limited to: positive electrode active materials for lithium ion batteries, positive electrode active materials for sodium ion batteries, and positive electrode active materials for potassium ion batteries.

[0164] The positive electrode active material of a lithium ion battery, the positive electrode active material of a sodium ion battery, and the positive electrode active material of a potassium ion battery are hereinafter referred to as lithium ion active material, sodium ion active material, and potassium ion active material, respectively.

[0165] Further, as an example, the lithium ion active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of lithium phosphates containing olivine structure may include but are not limited to at least one of lithium iron phosphate (such as LiFePO4, referred to as LFP), lithium manganese phosphate (such as LiMnPO4), and lithium manganese iron phosphate. In any embodiment of the present application, the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO4, x is any number from 0 to 1.

[0166] It can be understood that when x is 0, LiFe x Mn (1-x) PO4 is LiMnPO4 lithium manganese phosphate. When x is 1, LiFe x Mn (1-x) PO4 is LiFePO4 lithium iron phosphate (LFP).

[0167] It should be noted that the lithium content in the positive electrode material exemplified above refers to its content when it is not in use. During the use of the battery, it will be repeatedly used as a battery, and the Li in the positive electrode active material will change during the charge and discharge process. That is, the molar subscript of Li in the positive electrode active material in the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0168] For example, LiFe x Mn (1-x) PO4 can be further expressed as Li y Fe x Mn (1-x) PO4, y is 0~1.1.

[0169] For example, for the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x , y is 0.2~1.2, a+b+c=1, 0≤d≤1, 0≤x<2; M is one or more of Zr, Sr, B, Ti, Mg, Sn and Al, and A is one or more of S, N, F, Cl, Br and I.

[0170] The battery is accompanied by Li intercalation and deintercalation and consumption during the charge and discharge process. The molar content of Li varies when the battery is discharged to different states. The above definition of y includes the molar content of Li under different charge and discharge states of the battery. Furthermore, the battery voltage is usually between 2-5V.

[0171] As an example, the sodium ion active material may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as sodium ion battery positive electrode active materials may also be used.

[0172] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0173] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. Transition metals include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y includes at least one of P, S, and Si; n represents (YO4) n- valence.

[0174] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds containing anion units and halogen anions. The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y includes at least one of P, S, and Si, and n represents (YO4) n- valence state; the halogen may be at least one of F, Cl and Br.

[0175] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y includes at least one of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m represents (ZOy ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0176] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7)(NFPP), NaM1PO4F and Na3(VO y )2(PO4)2F (3-2y) At least one of .

[0177] M1 is at least one of V, Fe, Mn and Ni, and 0≤y≤1.

[0178] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a M2 b M3 c (CN)6, wherein M2 and M3 are each independently selected from at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0179] In any embodiment of the present application, in the positive electrode active layer, the mass proportion of the positive electrode active material is 70% to 99.8%.

[0180] In any embodiment of the present application, the components of the positive electrode active layer further include a conductive agent and a binder.

[0181] The conductive agent may be any commonly used conductive agent in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, the conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, graphene, and composite conductive agents thereof.

[0182] The binder of the binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS) and at least one of fluorine-containing acrylate resin.

[0183] Optionally, in the positive electrode active layer, the conductive agent accounts for 1% to 20% by mass.

[0184] Optionally, in the positive electrode active layer, the binder accounts for 1% to 10% by mass.

[0185] In some embodiments, the thickness of the positive electrode active layer is 30 μm to 200 μm.

[0186] In any embodiment of the present application, the current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0187] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0188] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0189] In any embodiment of the present application, the positive electrode sheet can be prepared by the following method: dispersing the above-mentioned components for preparing the positive electrode sheet in an organic solvent to form a positive electrode slurry; coating the positive electrode slurry on the current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0190] In some embodiments, the solid content of the positive electrode slurry is 40 wt % to 80 wt %, and the viscosity at 25° C. is adjusted to 5000 mPa·s to 25000 mPa·s.

[0191] In some embodiments, the organic solvent includes but is not limited to: N-methylpyrrolidone.

[0192] In some embodiments, the surface density of the positive electrode active material contained in the positive electrode sheet is 0.018 g / cm 2 ~0.05g / cm 2 .

[0193] Areal density of positive electrode active material = mass of positive electrode active material / area of ​​positive electrode sheet.

[0194] Negative electrode: The negative electrode may be any of the negative electrode systems commonly used in the art for secondary batteries. Examples of the negative electrode include lithium-ion secondary batteries and lithium metal secondary batteries, but are not limited to the following types.

[0195] In some embodiments, the secondary battery is a lithium metal secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used for a lithium metal battery and is well known in the art.

[0196] In some embodiments, the negative electrode sheet directly adopts a lithium-containing metal sheet.

[0197] In another embodiment, the negative electrode sheet includes a lithium-containing metal layer and a conductive layer stacked together.

[0198] Furthermore, the lithium-containing metal in the lithium-containing metal sheet and the lithium-containing metal layer can be lithium metal, or an alloy formed by lithium metal and other metal or non-metal elements.

[0199] Further, the other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In) and platinum (Pt); the non-metallic elements include at least one of boron (B), carbon (C) and silicon (Si).

[0200] In some embodiments, the conductive layer may be copper foil.

[0201] In any embodiment of the present application, the negative electrode sheet can be prepared by directly pressing a lithium-containing metal sheet to obtain the negative electrode sheet, or by stacking and pressing the lithium-containing metal layer and the conductive layer to obtain the negative electrode sheet.

[0202] In some embodiments, the secondary battery is a lithium-ion secondary battery, and the negative electrode sheet can be a negative electrode sheet that can be used for a lithium-ion secondary battery and is well known in the art.

[0203] In some embodiments, the negative electrode sheet includes a current collector and a negative electrode active layer supported on a surface of the current collector.

[0204] The components of the negative electrode active layer include a negative electrode active material.

[0205] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0206] In any embodiment of the present application, the above-mentioned negative electrode active material includes at least one of mesocarbon microbeads, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials and iron-based materials.

[0207] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to: at least one of mesophase carbon microbeads, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fibers, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, magnesium oxide, silicon-carbon composites, lithium metal and lithium metal alloys.

[0208] In any embodiment of the present application, the mass proportion of the negative electrode active material in the negative electrode active layer is 70% to 100%.

[0209] In any embodiment of the present application, the components of the negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0210] In any embodiment of the present application, the negative electrode conductive agent may be a conductive material commonly used in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, the negative electrode conductive agent may be selected from at least one of SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs, graphene, and composite conductive agents thereof.

[0211] The weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0 to 20 wt % based on the total weight of the negative electrode active layer.

[0212] The negative electrode binder can be a binder commonly used in the art, and can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0213] The weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt % based on the total weight of the negative electrode active layer.

[0214] In any embodiment of the present application, the negative electrode active layer may further optionally include other additives, such as a thickener, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of the other additives in the negative electrode active layer is 0 to 15 wt%.

[0215] In any embodiment of the present application, the current collector in the negative electrode sheet may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil.

[0216] The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material on a polymer substrate.

[0217] In some embodiments, the metal material is selected from any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0218] In some embodiments, the polymer material substrate includes at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0219] In any embodiment of the present application, the negative electrode sheet can be prepared by the following method: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent 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.

[0220] In some embodiments, the solvent includes but is not limited to water.

[0221] In some embodiments, the solid content of the negative electrode slurry is 30 wt % to 70 wt %, and the viscosity at 25° C. is adjusted to 2000 mPa·s to 10000 mPa·s.

[0222] In some embodiments, the surface density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm 2 ~0.03g / cm 2 .

[0223] The area density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0224] Separator: The separator is placed between the positive electrode and the negative electrode.

[0225] The present application has no particular limitation on the type of isolation membrane, and any known isolation membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0226] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0227] Optionally, the isolation film can be a single-layer film or a multi-layer composite film. Further, when the isolation film is a multi-layer composite film, the materials of each layer can be the same or different.

[0228] In some embodiments, the thickness of the isolation film is 2 μm to 15 μm; optionally, the thickness of the isolation film is 2 μm to 13 μm.

[0229] The secondary battery of the present application may be in a cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 4 of a secondary battery with a square structure as an example.

[0230] In some embodiments, referring to FIG2 , the housing may include a shell 41 and a cover 43. Shell 41 may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. Shell 41 may have an opening communicating with the receiving cavity, and cover 43 may be positioned over the opening to seal the receiving cavity.

[0231] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly 42. The electrode assembly 42 is enclosed in a housing. Electrolyte is infiltrated into the electrode assembly 42. The number of electrode assemblies 42 included in a battery cell 4 can be one or more, and can be adjusted based on demand.

[0232] The secondary battery includes one or more battery cells 4 .

[0233] A secondary battery can be a battery module or a battery pack. A battery module or battery pack includes at least one battery cell. A battery module can contain one or more battery cells, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0234] Figures 3 and 4 illustrate an exemplary battery pack 1. Battery pack 1 includes a battery case and one or more battery cells 4 disposed within the battery case. The battery case 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 the battery cells 4.

[0235] The plurality of battery cells 4 can be arranged in the battery box in any manner.

[0236] The present application also provides an electrical device, which includes the above-mentioned secondary battery.

[0237] Furthermore, in the above-mentioned electrical device, the secondary battery may exist in the form of a battery cell, or may be further assembled into a battery pack.

[0238] The above-mentioned battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.

[0239] The above-mentioned electrical devices may be, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc.

[0240] In some embodiments, the mobile device may be a mobile phone or a laptop computer, etc.

[0241] In some embodiments, electric vehicles include, but are not limited to, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, and the like.

[0242] Figure 5 shows an example of an electric device 5. The electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device 5's requirements for high power and high energy density of the secondary battery, a battery pack can be used.

[0243] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery as a power source.

[0244] The present invention will be described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. It should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the concept of the present invention, those skilled in the art should realize that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

[0245] The following are specific examples.

[0246] Example 1

[0247] S1. Preparation of lithium metal secondary batteries

[0248] (1) Preparation of electrolyte:

[0249] Mix the nitrile solvent, diluent, and film-forming agent in the appropriate ratio to obtain a transparent solution. Add a certain amount of lithium bis(fluorosulfonyl)imide salt to 10 mL of the aforementioned mixed solvent and stir thoroughly to obtain an electrolyte solution for later use.

[0250] Among them, by combining gas chromatography and ion chromatography to separate and analyze the components and mass proportions in the electrolyte, and combining with nuclear magnetic resonance testing, the structure of the nitrile solvent in the electrolyte, the molar volume ratio M1 of lithium bis(fluorosulfonyl)imide salt and the nitrile solvent, the molar ratio M2 of the diluent and the nitrile solvent, and the molar ratio M3 of the film-forming agent and the nitrile solvent can be confirmed. Please see Table 1 for details.

[0251] The types of nitrile solvents are listed in Table 1.

[0252] (2) Preparation of negative electrode sheet

[0253] A 50 μm lithium foil was rolled onto a 12 μm copper foil and then cut into a 41 mm × 51 mm rectangle as a negative electrode sheet.

[0254] (3) Preparation of positive electrode

[0255] Positive electrode preparation: The positive electrode active material lithium nickel cobalt manganese oxide (NCM811), the conductive agent acetylene black, and the binder PVDF were mixed in a mass ratio of 98:1:1, and the solvent NMP was added and stirred until the system became homogeneous to obtain a positive electrode slurry;

[0256] The positive electrode slurry was evenly coated on both sides of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. It was then cut into 40mm×50mm rectangles as positive electrode sheets. The surface capacity of the positive electrode sheet was 4mAh / cm 2 .

[0257] (4) Isolation membrane: Use polyethylene porous membrane.

[0258] (5) Assembly of lithium metal secondary batteries: Take a cut positive electrode sheet and a cut negative electrode sheet and match them, use the above-mentioned isolation film to isolate the positive and negative electrodes in the middle, and wrap them in an aluminum-plastic film bag to form a stacked dry cell. Inject 0.3g of the above-mentioned prepared electrolyte, and vacuum hot-press the aluminum-plastic film bag. After standing at room temperature for 6 hours, a lithium metal secondary battery with a rated capacity of 140mAh is obtained.

[0259] S2. Performance test of lithium metal secondary battery:

[0260] At 25° C., the lithium metal secondary battery was subjected to charge-discharge cycles using a rate of 0.5 C (i.e., 70 mA): the charge and discharge cutoff voltages were set to 4.3 V and 2.8 V, respectively, and the charge-discharge cycle was one cycle.

[0261] When the discharge capacity of the lithium metal secondary battery decays to 80% of the initial discharge capacity, the battery life is considered to be over, and the number of charge-discharge cycles experienced is recorded.

[0262] Please see Table 1 for specific results.

[0263] Examples 2 to 18

[0264] Examples 2 to 18 are basically the same as Example 1, with the only difference being that during the preparation of the electrolyte, the type of nitrile solvent is different from that in Example 1. Please see Table 1 for details.

[0265] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0266] Examples 19 to 24

[0267] Examples 19 to 24 are substantially the same as Example 10, except that during the preparation of the electrolyte, the molar volume ratio of the lithium bis(fluorosulfonyl)imide salt to the nitrile solvent is regulated differently from that in Example 10. See Table 1 for details.

[0268] The other step conditions are the same as those in Example 10. The test results are shown in Table 1.

[0269] Examples 25 to 32

[0270] Examples 25 to 32 are basically the same as Example 10, with the only difference being that during the preparation of the electrolyte, the amount or type of the diluent and the amount or type of the film-forming agent are different from those in Example 10. Please see Table 1 for details.

[0271] The other step conditions are the same as those in Example 10. The test results are shown in Table 1.

[0272] Comparative Example 1

[0273] Comparative Example 1 is substantially the same as Example 1, except that the type of nitrile solvent used in the preparation of the electrolyte is different from that in Example 1. The nitrile solvent in Comparative Example 1 is acetonitrile. For details, see Table 1.

[0274] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0275] Comparative Example 2

[0276] Comparative Example 2 is basically the same as Example 1, except that the type of nitrile solvent in the preparation process of the electrolyte is different from that in Example 1. The nitrile solvent in Comparative Example 2 is acetonitrile, and the amount added is different from that in Example 1. Please see Table 1 for details.

[0277] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0278] Comparative Example 3

[0279] Comparative Example 3 is basically the same as Example 1, except that the type of nitrile solvent used in the preparation of the electrolyte is different from that in Example 1. The nitrile solvent in Comparative Example 3 is adiponitrile, as shown in Chemical Formula (A). Please see Table 1 for details.

[0280] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0281] The relevant parameters and performance results of each embodiment and comparative example are shown in Table 1. The structures of the nitrile solvents used in each embodiment and comparative example are shown below.

[0282] Table 1

[0283] Note: In Table 1, “ / ” indicates that the substance or parameter does not exist, and a cycle number of 0 indicates that the performance is too poor to obtain accurate test data; TTE: 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl; BZ: benzene; VC: vinylene carbonate; VEC: vinyl ethylene carbonate.

[0284] Analysis of the data in Table 1: By comparing the test results of Examples 1 to 32 with Comparative Examples 1 to 3, it can be seen that the use of the nitrile solvents with a specific structure in the present application can improve the cycle performance of the secondary battery.

[0285] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0286] The above-described embodiments merely represent several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make several modifications and improvements without departing from the concept of the present invention, and these modifications and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims, and the description and drawings may be used to interpret the content of the claims.

Claims

1. An electrolyte, wherein the electrolyte comprises a nitrile solvent, wherein the nitrile solvent comprises a compound represented by formula (1): in, L is selected from any one of C(R1R2), O, Si(R3R4), B(R5), P(R6R7R8), and N(R9); R1 to R9 are independently selected from any one of H, halogen, substituted or unsubstituted alkyl having 1 to 3 carbon atoms, alkoxy having 1 to 3 carbon atoms, amine, and cyano, and R1 and R2 are not cyano and H; R 11 It is an alkane chain containing 1 to 4 carbon atoms; R 12 ~R 14 are independently selected from any one of H, halogen, substituted or unsubstituted alkyl having 1 to 3 carbon atoms, alkoxy having 1 to 3 carbon atoms, amine and cyano; and when L is selected from C(R1R2), R 12 ~R 14 Not cyano.

2. The electrolyte according to claim 1, wherein The nitrile solvent includes a compound represented by formula (1-1):

3. The electrolyte according to any one of claims 1 to 2, wherein L is selected from any one of C (R1R2), Si (R3R4) and N (R9).

4. The electrolyte according to claim 1, wherein The compound represented by formula (1) satisfies at least one of the following conditions (1) to (3): (1) R1 to R9 are independently selected from any one of halogen, alkyl having 1 to 3 carbon atoms, alkyl having 1 to 3 carbon atoms substituted by halogen, alkoxy having 1 to 3 carbon atoms and cyano; (2) R1 and R2 are not H at the same time, R3 and R4 are not H at the same time, R6, R7 and R8 are not H at the same time, and R5 and R9 are not H; (3)R 12 ~R 14 Each of them is independently selected from any one of H, halogen, alkyl group having 1 to 3 carbon atoms, alkyl group having 1 to 3 carbon atoms substituted with halogen, alkoxy group having 1 to 3 carbon atoms and cyano group.

5. The electrolyte according to any one of claims 1 to 4, wherein The nitrile solvent includes at least one of the compounds represented by formula (1a) to formula (1f): Among them, each R a1 , each R b1 , each R c1 , each R d1 , each R e1 And each R f1 are independently selected from any one of H, halogen, alkyl having 1 to 3 carbon atoms, alkyl having 1 to 3 carbon atoms substituted by halogen, alkoxy having 1 to 3 carbon atoms and cyano, and each R a1 None of them are cyano; Each R a2 , each R b2 , each R c2 , each R d2 And each R e2 Each of them is independently selected from any one of halogen, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with halogen, and an alkoxy group having 1 to 3 carbon atoms.

6. The electrolyte according to claim 5, wherein the nitrile solvent satisfies at least one of the following conditions (1) to (6): (1) At least one R a2 is an alkoxy group having 1 to 3 carbon atoms; (2) Each R b2 are independently selected from an alkyl group having 1 to 3 carbon atoms and an alkoxy group having 1 to 3 carbon atoms. Any one of the bases; (3) Each R c1 are independently selected from alkyl groups having 1 to 3 carbon atoms; (4) Each R d1 are independently selected from alkyl groups having 1 to 3 carbon atoms; (5) Each R e1 Each is independently selected from an alkoxy group having 1 to 3 carbon atoms; (6) Each R f1 Each is independently selected from any one of H and an alkyl group having 1 to 2 carbon atoms.

7. The electrolyte according to any one of claims 1 to 6, wherein The nitrile solvent includes at least one of the compounds represented by formula (11) to formula (58): 8 . The electrolyte according to claim 1 , wherein the electrolyte further comprises an electrolyte salt, and the molar volume ratio of the electrolyte salt to the nitrile solvent is 1 mol / L to 15 mol / L.

9. The electrolyte according to claim 8, wherein the electrolyte salt satisfies at least one of the following conditions (1) to (2): (1) In the electrolyte, the molar volume ratio of the electrolyte salt to the nitrile solvent is 2 mol / L to 12 mol / L; (2) The electrolyte salt includes a lithium ion electrolyte salt.

10. The electrolyte according to any one of claims 1 to 9, wherein the components of the electrolyte further include a film-forming additive, and the film-forming additive includes an unsaturated cyclic carbonate film-forming additive. 11 . The electrolyte according to claim 10 , wherein the molar ratio of the film-forming additive to the nitrile solvent is (0.05-0.5):

1.

12. The electrolyte according to any one of claims 10 to 11, wherein the film-forming additive comprises at least one of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, vinyl sulfate, propylene sulfate and vinyl sulfite.

13. A secondary battery, comprising the electrolyte according to any one of claims 1 to 12. 14 . The secondary battery according to claim 13 , wherein the secondary battery is a lithium metal secondary battery.

15. An electrical device, comprising the secondary battery according to any one of claims 13 to 14.

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