Electrolyte, secondary battery and electrical apparatus

Abstract

An electrolyte, a secondary battery and an electrical apparatus. The components of the electrolyte comprise a functional compound represented by formula (1). In formula (1), T1-T3 are each independently selected from any one of an alkyl group having 1-10 carbon atoms, an alkenyl group having 2-10 carbon atoms, an alkynyl group having 2-10 carbon atoms, and groups represented by following formulae (a)-(f). Among T1-T3, at least one is selected from the group represented by formula (a), and at least one is selected from the group represented by formula (b), (c), (d) or (e). In a charging / discharging process of the electrolyte, the functional compound represented by formula (1) can capture an oxidation product and improve the toughness of a formed SEI film, thereby improving the cycle performance of a secondary battery.

Description

Electrolyte, secondary battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202311279087.6, filed on September 28, 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] Lithium metal batteries, with their high theoretical energy density and low negative electrode potential, are highly promising secondary batteries. However, the performance of lithium metal batteries is severely limited by the electrolyte. Traditional electrolytes often release reactive oxygen species during the charge and discharge process, which can easily cause oxidation reactions in the electrolyte. This has a significant negative impact on key performance indicators such as battery cyclability, and in severe cases, can easily lead to safety accidents.

[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 secondary 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 functional compound represented by formula (1):

[0011] T1 to T3 are independently selected from any one of an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a group represented by the following formulas (a) to (f); at least one of T1 to T3 is selected from the group represented by formula (a), and at least one is selected from the group represented by formula (b), formula (c), formula (d), or formula (e);

[0012] wherein R1 to R3 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms, and an aryl group having 6 to 15 ring atoms, and at least one R1 is not H, and at least one R2 is not H;

[0013] R4 to R6 are each independently selected from a single bond, a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, or a substituted or unsubstituted alkenylene group having 2 to 5 carbon atoms;

[0014] L1 is selected from a single bond or NR7, R7 is selected from H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 15 ring atoms, and Any one of , L2 is selected from a single bond or an alkylene group having 1 to 5 carbon atoms;

[0015] X1 is C(R8)2, X2 is C(R9)2; each R8 and each R9 are independently selected from any one of H, substituted or unsubstituted alkyl having 1 to 5 carbon atoms, substituted or unsubstituted alkenyl having 2 to 5 carbon atoms, and substituted or unsubstituted alkynyl having 2 to 5 carbon atoms;

[0016] * represents the attachment site.

[0017] The components of the above-mentioned electrolyte contain functional compounds with specific structures. The compound shown in formula (1) contains a phosphite structural group, a silicon-containing group and specific structures (b), (c), (d) or (e), wherein the phosphite structural group has nucleophilicity and can capture fluorine-containing byproducts formed by oxidation of the electrolyte, and also has certain flame retardancy; the silicon-containing group captures acidic substances formed by oxidative decomposition of the electrolyte, and can participate in the formation of the SEI film, thereby increasing its toughness; among (b), (c), (d) or (e), some contain nitrogen-containing functional groups with lone pairs of electrons, and some contain specific unsaturated structures, all of which can capture acidic substances while being beneficial to the formation of the SEI film and improving its toughness. The specific structures are organically combined, so that the compound shown in formula (1) can capture oxidation products during the charge and discharge process of the electrolyte, while improving the toughness of the formed SEI film, thereby improving the cycle performance of the secondary battery.

[0018] In some embodiments, the functional compound contains a nitrogen atom.

[0019] Nitrogen atoms have lone pairs of electrons, which can promote the formation of SEI film.

[0020] In some embodiments, the functional compound contains and at least one of the groups of formula (c).

[0021] The study found that the compound represented by formula (1) contains When a group of formula (c) is present, the toughness of the SEI film can be further improved, thereby improving the cycle performance of the battery.

[0022] In some embodiments, R1-R3 are independently selected from any one of H, an alkyl group having 1-5 carbon atoms, an alkyl group having 1-5 carbon atoms substituted by a halogen, an alkenyl group having 2-5 carbon atoms, an alkenyl group having 2-5 carbon atoms substituted by a halogen, an alkynyl group having 2-5 carbon atoms, and an alkynyl group having 2-5 carbon atoms substituted by a halogen;

[0023] Optionally, R1 to R3 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, an alkenyl group having 2 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms substituted by halogen, an alkynyl group having 2 to 3 carbon atoms, and an alkynyl group having 2 to 3 carbon atoms substituted by halogen.

[0024] In some embodiments, R4 to R6 are independently selected from any one of a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 1 to 5 carbon atoms substituted by a halogen, an alkenylene group having 2 to 5 carbon atoms, and an alkenylene group having 2 to 5 carbon atoms substituted by a halogen;

[0025] Optionally, R4 to R6 are independently selected from any one of a single bond, an alkylene group having 1 to 3 carbon atoms, an alkylene group having 1 to 3 carbon atoms substituted by halogen, an alkenylene group having 2 to 3 carbon atoms, and an alkenylene group having 2 to 3 carbon atoms substituted by halogen.

[0026] In some embodiments, R7 is selected from an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, and Any of the following;

[0027] Optionally, R7 is selected from an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by a halogen, and Any one of .

[0028] In some embodiments, each R8 and each R9 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, and an alkenyl group having 2 to 5 carbon atoms, i.e., an alkenyl group having 2 to 5 carbon atoms substituted by a halogen;

[0029] Optionally, each R8 and each R9 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, and an alkenyl group having 2 to 3 carbon atoms, i.e., an alkenyl group having 2 to 3 carbon atoms substituted by halogen.

[0030] The functional compound includes at least one of the following (I) to (X):

[0031] In some embodiments, the electrolyte solution further comprises an electrolyte salt and an organic solvent;

[0032] Based on the total volume of the components in the electrolyte excluding the electrolyte salt and the functional compound, the concentration A of the functional compound satisfies: A≥0.05 mol / L;

[0033] Optionally, 0.05 mol / L ≤ A ≤ 1 mol / L;

[0034] Further optionally, 0.25 mol / L≤A≤0.75 mol / L.

[0035] In some embodiments, the electrolyte further comprises a film-forming agent.

[0036] In some embodiments, the volume ratio of the film-forming agent to the organic solvent is 1:(0.5-3);

[0037] Optionally, the volume ratio of the film-forming agent to the organic solvent is 1:(1-3).

[0038] Film-forming agents can work synergistically with organic solvents to regulate the solvation structure of lithium ions in the electrolyte, form a film on the electrode surface, and improve coulombic efficiency and cycle performance.

[0039] In some embodiments, the electrolyte salt includes a first electrolyte salt and a second electrolyte salt.

[0040] The first electrolyte salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate;

[0041] The second electrolyte salt includes at least one of lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluorobisoxalatophosphate, lithium tetrafluorooxalatophosphate, and lithium difluorophosphate.

[0042] A specific first electrolyte salt and a second electrolyte salt are used in synergistic combination, wherein the second electrolyte salt can regulate the lithium ion deposition morphology, promote film formation, has high stability, can reduce the decomposition of electrolyte components and the probability of harmful side reactions, and further improve the cycle performance of the battery.

[0043] The electrolyte salt satisfies at least one of the following conditions (1) to (2):

[0044] (1) Based on the total volume of the components in the electrolyte solution excluding the electrolyte salt and the functional compound, the concentration of the first electrolyte salt is 0.5 mol / L to 4 mol / L;

[0045] (2) The concentration of the second electrolyte salt in the electrolyte is 0.05 mol / L to 1.5 mol / L based on the total volume of the components in the electrolyte except the electrolyte salt and the functional compound.

[0046] In some embodiments, the concentration of the first electrolyte salt is greater than the concentration of the second electrolyte salt.

[0047] The contents of the first electrolyte salt and the second electrolyte salt are further regulated to give full play to the synergistic effect.

[0048] 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.

[0049] The above-mentioned secondary battery has excellent cycle performance.

[0050] 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

[0051] 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:

[0052] FIG1 is a schematic diagram of an embodiment of a battery cell;

[0053] Figure 2 is an exploded view of Figure 1;

[0054] FIG3 is a schematic diagram of an embodiment of a battery pack;

[0055] FIG4 is an exploded view of FIG3 ;

[0056] FIG5 is a schematic diagram of an embodiment of an electric device using a battery as a power source.

[0057] Explanation of the accompanying reference numerals: 1. battery pack; 2. upper case; 3. lower case; 4. battery cell; 41. housing; 42. electrode assembly; 43. cover plate; 5. electrical device. DETAILED DESCRIPTION

[0058] 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.

[0059] In the description of the embodiments of the present application, “multiple” means two or more, unless otherwise clearly and specifically defined.

[0060] 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.

[0061] 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; similarly, "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.

[0062] In the present application, the number of carbon atoms in the "alkyl group having 1 to 10 carbon atoms" can be 1 to 10, including 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Non-limiting examples include methane, ethyl, and n-propyl.

[0063] In this application, the term "alkylene" refers to a group formed when an alkane loses two hydrogen atoms, such as methane losing two hydrogen atoms to form a methylene group; similarly, "alkenylene or alkynylene" refers to a group formed when an alkene or alkyne loses two hydrogen atoms, such as ethylene losing two hydrogen atoms to form ethenylene and acetylene losing two hydrogen atoms to form ethynylene.

[0064] The term "chain alkyl" refers to a group formed by losing one hydrogen in an alkane in which the carbon atoms are all connected by carbon-carbon single bonds and do not form a ring, and the remaining valence bonds are all bonded to hydrogen, including straight-chain alkane groups and branched-chain alkane groups.

[0065] 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.

[0066] In the present application, the halogen group includes chlorine, fluorine, bromine, and iodine.

[0067] In this application, "aryl" refers to a hydrocarbon group containing at least one aromatic ring, including non-fused-ring aromatic groups and fused-ring aromatic groups. A fused-ring aromatic group is a group formed by linking two or more aromatic rings through two common adjacent ring atoms, i.e., a fused ring.

[0068] Aromatic ring refers to a cyclic hydrocarbon compound with aromatic properties: that is, a hydrocarbon compound with a cyclic closed-ring conjugated system.

[0069] In this application, the term "ring atoms" refers to the number of atoms bonded to form a ring. When a ring is substituted with a substituent, the atoms contained in the substituent are not included in the ring atoms. The term "ring atoms" used below applies unless otherwise specified. For example, a benzene ring has 6 ring atoms, and a naphthalene ring has 10 ring atoms.

[0070] In summary, the performance improvement of traditional secondary batteries, especially lithium metal secondary batteries, is severely restricted by the electrolyte. Traditional electrolytes release acidic byproducts such as HF during the charge and discharge process. Therefore, functional additives containing silane are often used to capture the acidic substances.

[0071] However, studies have found that simply capturing acidic substances has limited effect on improving battery performance. After a large number of experimental studies, the electrolyte of this application was obtained.

[0072] In one embodiment of the present application, an electrolyte is provided, wherein the components of the electrolyte include a functional compound represented by formula (1):

[0073] T1 to T3 are independently selected from any one of an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and a group represented by formula (a) to (f) below; and at least one of T1 to T3 is selected from the group represented by formula (a), and at least one is selected from the group represented by formula (b), formula (c), formula (d), or formula (e);

[0074] wherein R1 to R3 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms, and an aryl group having 6 to 15 ring atoms, and at least one R1 is not H, and at least one R2 is not H;

[0075] R4 to R6 are each independently selected from a single bond, a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, or a substituted or unsubstituted alkenylene group having 2 to 5 carbon atoms;

[0076] L1 is selected from a single bond or NR7, R7 is selected from H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 15 ring atoms, and Any one of , L2 is selected from a single bond or an alkylene group having 1 to 5 carbon atoms;

[0077] X1 is C(R8)2, X2 is C(R9)2; each R8 and each R9 are independently selected from any one of H, substituted or unsubstituted alkyl having 1 to 5 carbon atoms, substituted or unsubstituted alkenyl having 2 to 5 carbon atoms, and substituted or unsubstituted alkynyl having 2 to 5 carbon atoms;

[0078] * represents the attachment site.

[0079] The components of the above-mentioned electrolyte contain functional compounds with specific structures. The compound shown in formula (1) contains a phosphite structural group, a silicon-containing group and specific structures (b), (c), (d) or (e), wherein the phosphite structural group has nucleophilicity and can capture fluorine-containing byproducts formed by oxidation of the electrolyte, and also has certain flame retardancy; the silicon-containing group captures acidic substances formed by oxidative decomposition of the electrolyte, and can participate in the formation of the SEI film, thereby increasing its toughness; among (b), (c), (d) or (e), some contain nitrogen-containing functional groups with lone pairs of electrons, and some contain specific unsaturated structures, all of which can capture acidic substances while being beneficial to the formation of the SEI film and improving its toughness. The specific structures are organically combined, so that the compound shown in formula (1) can capture oxidation products during the charge and discharge process of the electrolyte, while improving the toughness of the formed SEI film, thereby improving the cycle performance of the secondary battery.

[0080] In some embodiments, the functional compound contains a nitrogen atom.

[0081] Nitrogen atoms have lone pairs of electrons, which can promote the formation of SEI film.

[0082] It can be understood that the introduction of nitrogen-containing functional groups by selecting specific types of T1 to T3 means the introduction of nitrogen atoms; further, the nitrogen-containing functional groups can be at least one of the groups represented by formula (b), formula (d) and formula (e), or can be the group represented by formula (a) where L1 is selected from NR7.

[0083] In some embodiments, the functional compound contains and at least one of the groups of formula (c).

[0084] The study found that the compound represented by formula (1) contains When a group of formula (c) is present, the toughness of the SEI film can be further improved, thereby improving the cycle performance of the battery.

[0085] Similarly, by selecting the specific types of T1 to T3,

[0086] In some embodiments, R1-R3 are independently selected from any one of H, an alkyl group having 1-5 carbon atoms, an alkyl group having 1-5 carbon atoms substituted by halogen, an alkenyl group having 2-5 carbon atoms, an alkenyl group having 2-5 carbon atoms substituted by halogen, an alkynyl group having 2-5 carbon atoms, and an alkynyl group having 2-5 carbon atoms substituted by halogen.

[0087] In some embodiments, R1-R3 are independently selected from any one of H, an alkyl group having 1-5 carbon atoms, an alkyl group having 1-5 carbon atoms substituted by halogen, an alkenyl group having 2-5 carbon atoms, an alkenyl group having 2-5 carbon atoms substituted by halogen, an alkynyl group having 2-5 carbon atoms, and an alkynyl group having 2-5 carbon atoms substituted by halogen.

[0088] Optionally, R1 to R3 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, an alkenyl group having 2 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms substituted by halogen, an alkynyl group having 2 to 3 carbon atoms, and an alkynyl group having 2 to 3 carbon atoms substituted by halogen.

[0089] In some embodiments, R1-R3 are independently selected from any one of H, an alkyl group having 1-3 carbon atoms, an alkyl group having 1-3 carbon atoms substituted by halogen, an alkenyl group having 2-3 carbon atoms, an alkenyl group having 2-3 carbon atoms substituted by halogen, an alkynyl group having 2-3 carbon atoms, and an alkynyl group having 2-3 carbon atoms substituted by halogen.

[0090] In some embodiments, R3 is selected from any one of an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, an alkenyl group having 2 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms substituted by halogen, an alkynyl group having 2 to 3 carbon atoms, and an alkynyl group having 2 to 3 carbon atoms substituted by halogen.

[0091] In some embodiments, R1 to R3 are independently selected from any one of H, methyl, ethyl, n-propyl, isopropyl, methyl substituted by halogen, ethyl substituted by halogen, n-propyl substituted by halogen, isopropyl substituted by halogen, vinyl, propenyl, vinyl substituted by halogen, and propenyl substituted by halogen.

[0092] In some embodiments, R4 to R6 are independently selected from any one of a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 1 to 5 carbon atoms substituted by halogen, an alkenylene group having 2 to 5 carbon atoms, and an alkenylene group having 2 to 5 carbon atoms substituted by halogen.

[0093] It can be understood that when R4, R5 or R6 is selected from a single bond, it means that the groups at both ends of R4, R5 or R6 are directly connected by a single bond.

[0094] In some embodiments, R4 to R6 are independently selected from any one of a single bond, a chain alkylene group having 1 to 5 carbon atoms, a chain alkylene group having 1 to 5 carbon atoms substituted by halogen, a chain alkenylene group having 2 to 5 carbon atoms, and a chain alkenylene group having 2 to 5 carbon atoms substituted by halogen.

[0095] Optionally, R4 to R6 are independently selected from any one of a single bond, an alkylene group having 1 to 3 carbon atoms, an alkylene group having 1 to 3 carbon atoms substituted by halogen, an alkenylene group having 2 to 3 carbon atoms, and an alkenylene group having 2 to 3 carbon atoms substituted by halogen.

[0096] In some embodiments, R4 to R6 are independently selected from any one of a single bond, a chain alkylene group having 1 to 3 carbon atoms, a chain alkylene group having 1 to 3 carbon atoms substituted by halogen, a chain alkenylene group having 2 to 3 carbon atoms, and a chain alkenylene group having 2 to 3 carbon atoms substituted by halogen.

[0097] In some embodiments, R4 to R6 are independently selected from any one of a single bond, methylene, ethylene, propylene, isopropylene, methylene substituted by halogen, ethylene substituted by halogen, propylene substituted by halogen, isopropylene substituted by halogen, vinylene, propenylene, vinylene substituted by halogen, and propenylene substituted by halogen.

[0098] In some embodiments, R7 is selected from an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by a halogen, and Any one of .

[0099] In some embodiments, R7 is selected from a chain alkyl group having 1 to 5 carbon atoms, a chain alkyl group having 1 to 5 carbon atoms substituted by halogen, and Any one of .

[0100] Optionally, R7 is selected from an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by a halogen, and Any one of .

[0101] In some embodiments, R7 is selected from a chain alkyl group having 1 to 3 carbon atoms, a chain alkyl group having 1 to 3 carbon atoms substituted by halogen, and Any one of .

[0102] In some embodiments, R7 is selected from methyl, ethyl, propyl, isopropyl, methyl substituted by halogen, ethyl substituted by halogen, propyl substituted by halogen, isopropyl substituted by halogen, and Any one of .

[0103] In some embodiments, L2 is selected from a single bond or a chain alkylene group having 1 to 5 carbon atoms.

[0104] In some embodiments, L2 is selected from a single bond or an alkylene group having 1 to 3 carbon atoms.

[0105] In some embodiments, L2 is selected from a single bond or a chain alkylene group having 1 to 3 carbon atoms.

[0106] In some of these embodiments, L2 is selected from a single bond, methyl, ethyl, n-propyl, or isopropyl.

[0107] In some embodiments, each R8 and each R9 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, and an alkenyl group having 2 to 5 carbon atoms, i.e., an alkenyl group having 2 to 5 carbon atoms substituted by halogen.

[0108] In some embodiments, each R8 and each R9 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, and an alkenyl group having 2 to 5 carbon atoms, i.e., an alkenyl group having 2 to 5 carbon atoms substituted by halogen.

[0109] Optionally, each R8 and each R9 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, and an alkenyl group having 2 to 3 carbon atoms, i.e., an alkenyl group having 2 to 3 carbon atoms substituted by halogen.

[0110] In some embodiments, each R8 and each R9 are independently selected from any one of H, a chain alkyl group having 1 to 3 carbon atoms, a chain alkyl group having 1 to 3 carbon atoms substituted by halogen, and an alkenyl group having 2 to 3 carbon atoms, i.e., an alkenyl group having 2 to 3 carbon atoms substituted by halogen.

[0111] In some embodiments, each R8 and each R9 are independently selected from any one of H, methyl, ethyl, propyl, isopropyl, methyl substituted by halogen, ethyl substituted by halogen, propyl substituted by halogen, isopropyl substituted by halogen, vinyl, propenyl, vinyl substituted by halogen and propenyl substituted by halogen.

[0112] In some embodiments, each R8 may be the same or different.

[0113] In some embodiments, each R9 may be the same or different.

[0114] In some embodiments, the functional compound includes at least one of the following (I) to (X):

[0115] It should be noted that the functional compound represented by formula (1) of the present application can be purchased from commercial channels or synthesized by referring to the following preparation method, which is illustrated below by taking the preparation of compounds represented by formulas (I) to (X) as an example.

[0116] Formula (I): Under a protective atmosphere, oxazolidin-2-one and tris(trimethylsilyl)phosphite are subjected to a first substitution reaction to obtain a compound of formula (I).

[0117] In some embodiments, the molar ratio of oxazolidin-2-one to tris(trimethylsilyl)phosphite is (0.1-0.5):1.

[0118] In some embodiments, the first substitution reaction is carried out at 0-5° C.; further, the first substitution reaction is carried out for 10 h to 24 h.

[0119] In some embodiments, after the substitution reaction is completed, the process further comprises the step of taking the liquid product and purifying it.

[0120] Formula (II): The preparation method of formula (II) refers to formula (I), except that tris(trimethylsilyl)phosphite is replaced by bis(trimethylsilyl)methylphosphite.

[0121] Formula (III): comprising the following steps:

[0122] Under a protective atmosphere, hydrobromic acid is reacted with diethyl cyanomethylphosphite to obtain bis(acetonitrile)ethyl phosphite bromide.

[0123] In some embodiments, the hydrobromic acid is added in the form of a hydrobromic acid aqueous solution with a mass concentration of 40% to 50%.

[0124] In some embodiments, the molar ratio of hydrobromic acid to diethyl cyanomethylphosphite is (1-2):1.

[0125] Among them, the structures of diethyl cyanomethylphosphite and bis(acetonitrile)ethyl phosphite bromide are shown in (a) and (b) respectively:

[0126] Under a protective atmosphere, bis(acetonitrile)ethyl phosphite is reacted with trimethylsilane at 0-5° C., and the resulting product is filtered to obtain bis(acetonitrile)trimethylsilicate phosphite.

[0127] Under a protective atmosphere, bis(acetonitrile)trimethylsilicate phosphite is reacted with (E)-4-methoxybut-3-en-2-one at 0°C or below to obtain the compound of formula (III).

[0128] Formula (IV): Nitrosomethane, bis(trimethylsilyl)methylphosphite and (E)-4-methoxybut-3-en-2-one are mixed and reacted under a protective atmosphere at 0-10°C, and filtered to obtain the product of formula (IV).

[0129] In some embodiments, the reaction time is 10 hours to 15 hours.

[0130] In some embodiments, the molar ratio of nitrosomethane, bis(trimethylsilyl)methylphosphite and (E)-5-methoxypent-3-en-2-one is 1:(1-2):(1-2).

[0131] Formula (V): Ethanolamine and oxazolidin-2-one were mixed and reacted at 0-10°C under a protective atmosphere, and filtered to obtain intermediate product 1, the structure of which is:

[0132] Optionally, the mixing reaction time is 10 h to 15 h.

[0133] In some embodiments, the molar ratio of ethanolamine to oxazolidin-2-one is 1:(1-2).

[0134] The intermediate product 1 was subjected to a second substitution reaction with trimethylsilane and stirred for 10 hours to obtain the intermediate product 2:

[0135] In some embodiments, the second substitution reaction time is 10 to 15 hours.

[0136] The intermediate product 2 is subjected to a substitution reaction with trimethyl phosphite to obtain formula (V).

[0137] Formula (VI): Under a protective atmosphere, at 0-10° C., imino (3-carbonyl-1-butenyl), trimethylsilane and trimethyl phosphite are mixed and reacted, and the product (VI) can be obtained by filtering.

[0138] In some embodiments, the molar ratio of imino(3-carbonyl-1-butenyl), trimethylsilane and trimethyl phosphite is 1:1:(1-2).

[0139] In some embodiments, the mixing reaction time is 10 h to 15 h.

[0140] Formula (VII): Under a protective atmosphere, dimethyltrimethylsilylphosphonate and nitrosomethane are mixed and reacted at 0-10° C., and filtered to obtain product (VII); further, the mixing reaction time is 10 h to 15 h.

[0141] In some embodiments, the molar ratio of dimethyltrimethylsilylphosphonate to nitrosomethane is (1-2):1.

[0142] Formula (VIII): Under a protective atmosphere, N,N-dimethyltrimethylsilylamine and trimethyl phosphite are mixed and reacted at 0-10°C, and filtered to obtain product (VIII); further, the mixing reaction time is 10h-20h.

[0143] In some embodiments, the molar ratio of N,N-dimethyltrimethylsilylamine to trimethyl phosphite is 1:(1-2).

[0144] Formula (IX): Under a protective atmosphere, N-methyl, N-ethyltrimethylsilylamine and 1 mol of trimethyl phosphite are mixed and reacted at 0-10°C, and filtered to obtain product (IX). Furthermore, the mixing reaction time is 10h-20h.

[0145] In some embodiments, the molar ratio of N-methyl, N-ethyltrimethylsilylamine to trimethyl phosphite is 1:(1-2).

[0146] Formula (X): Under a protective atmosphere, nitrosomethane and methylbis(trimethylsilyl)phosphite are mixed and reacted at 0-10°C, and filtered to obtain product (X). Furthermore, the mixing reaction time is 10 h to 20 h.

[0147] In some embodiments, the molar ratio of nitrosomethane to methylbis(trimethylsilyl) phosphite is 1:(1-2).

[0148] In the present application, the functional compounds represented by formula (1) can be prepared by referring to the above preparation process.

[0149] In the present application, the "protective atmosphere" may be at least one of an inert gas and nitrogen.

[0150] Specifically, the above-mentioned “protective atmosphere” includes at least one of argon and nitrogen.

[0151] In some embodiments, the electrolyte solution further comprises an electrolyte salt and an organic solvent.

[0152] In some embodiments, based on the total volume of the components in the electrolyte excluding the electrolyte salt and the functional compound, the concentration A of the functional compound satisfies: A≥0.05 mol / L.

[0153] In some embodiments, 0.05 mol / L≤A≤1 mol / L.

[0154] In some embodiments, 0.25 mol / L≤A≤0.75 mol / L.

[0155] The concentration of the functional compound is regulated to further improve the toughness of the formed SEI film, thereby improving the cycle performance of the secondary battery.

[0156] In the above “0.05mol / L≤A≤1mol / L”, the value of A includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and the following point values: 0.05mol / L, 0.1mol / L, 0.15mol / L, 0.2mol / L, 0.25mol / L, 0.3mol / L, 0.35mol / L, 0.4mol / L, 0.45mol / L, 0.5mol / L, 0.55mol / L, 0.6mol / L, 0.65mol / L, 0.7mol / L, 0.75mol / L, or a range consisting of any two values, for example, 0.05mol / L to 0.1mol / L, 0.05mol / L to 0.9mol / L, 0.1mol / L to 0.9mol / L, 0.2mol / L to 0.9mol / L, 0.3mol / L to 0.9mol / L, 0.4mol / L to 0.9mol / L, 0.5mol / L to 0.9mol / L, 0.6mol / L to 0.9mol / L, 0.7mol / L to 0.9mol / L.

[0157] In some embodiments, the electrolyte further comprises a film-forming agent.

[0158] In some embodiments, the volume ratio of the film-forming agent to the organic solvent is 1:(0.5-3).

[0159] In some embodiments, the volume ratio of the film-forming agent to the organic solvent is 1:(1-3).

[0160] Film-forming agents can work synergistically with organic solvents to regulate the solvation structure of lithium ions in the electrolyte, form a film on the electrode surface, and improve coulombic efficiency and cycle performance.

[0161] In the above "1:(0.5~3)", 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: 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3; or a range consisting of any two values.

[0162] In the present application, the organic solvent and the film-forming agent may be any of the organic solvents and film-forming agents commonly used in the art, and non-limiting examples of the organic solvent and the film-forming agent are provided herein.

[0163] The organic solvent includes at least one of an ester solvent, an ether solvent, a sulfone solvent and a nitrile solvent; specifically, the organic solvent includes ethyl methyl carbonate, diethyl carbonate, methyl trifluoroethyl carbonate, dimethyl carbonate, cyclohexane, benzene, toluene, p-xylene, m-xylene, o-xylene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, trifluorotoluene, trifluoromethoxybenzene, decafluoropentane, perfluoropentanone, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, bis(2,2,2-trifluoroethyl)ether, 1, At least one of 1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, ethyl trifluoromethyl ether, difluoromethyl-2,2,3,3,3-pentafluoropropyl ether, heptafluoropropyl-1,2,2,2-tetrafluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, perfluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, ethyl-2,2,2-tetrafluoroethyl ether and bis(1,1,2,2-tetrafluoroethyl) ether.

[0164] In some embodiments, the film-forming agent includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, and bisfluoroethylene carbonate.

[0165] Optionally, based on the total mass of the components in the electrolyte excluding the electrolyte salt and the functional compound, the mass proportion of the organic solvent is greater than or equal to 20%.

[0166] Organic solvents can adjust the solvation structure in the electrolyte and improve the ionic conductivity.

[0167] In some embodiments, the electrolyte salt includes a lithium electrolyte salt.

[0168] In some embodiments, the electrolyte salt includes a first electrolyte salt and a second electrolyte salt, the first electrolyte salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; the second electrolyte salt includes at least one of lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate, lithium tetrafluorooxalatophosphate and lithium difluorophosphate.

[0169] A specific first electrolyte salt and a second electrolyte salt are used in synergistic combination, wherein the second electrolyte salt can regulate the lithium ion deposition morphology, promote film formation, has high stability, can reduce the decomposition of electrolyte components and the probability of harmful side reactions, and further improve the cycle performance of the battery.

[0170] In some embodiments, the concentration of the first electrolyte salt is 0.5 mol / L to 4 mol / L based on the total volume of the components in the electrolyte excluding the electrolyte salt and the functional compound.

[0171] In some embodiments, based on the total volume of the components in the electrolyte excluding the electrolyte salt and the functional compound, the concentration of the second electrolyte salt in the electrolyte is 0.05 mol / L to 1.5 mol / L.

[0172] In the above "0.5mol / L~4mol / L", 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: 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, 3.5mol / L, 4mol / L; or a range consisting of any two values.

[0173] In the above-mentioned “0.05mol / L~1.5mol / L”, 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: 0.05mol / L, 0.1mol / L, 0.15mol / L, 0.2mol / L, 0.25mol / L, 0.3mol / L, 0.35mol / L, 0.4mol / L, 0.45mol / L, 0.5mol / L, 0.55mol / L, 0.6mol / L, 0.65mol / L, 0.7mol / L, 0.8mol / L, 0.9mol / L, 1mol / L, 1.1mol / L, 1.2mol / L, 1.3mol / L, 1.4mol / L, 1.5mol / L; or a range consisting of any two values.

[0174] In some embodiments, the concentration of the first electrolyte salt is greater than the concentration of the second electrolyte salt.

[0175] The contents of the first electrolyte salt and the second electrolyte salt are further regulated to give full play to the synergistic effect.

[0176] In some of the embodiments, the total concentration of the electrolyte salt is 0.5 mol / L to 5 mol / L based on the total volume of the components in the electrolyte solution excluding the electrolyte salt and the functional compound.

[0177] According to one embodiment of the present application, a secondary battery is provided. The secondary battery includes the electrolyte according to the first aspect.

[0178] In some embodiments, the secondary battery further includes a positive electrode sheet, a negative electrode sheet, and a separator.

[0179] In the present application, the positive electrode sheet, the negative electrode sheet and the separator may adopt the system commonly used in the art, and the positive electrode sheet, the negative electrode sheet and the separator are illustrated below.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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 0.3O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 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.

[0184] 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).

[0185] 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).

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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%.

[0190] In any embodiment of the present application, the components of the positive electrode active layer further include a conductive agent and a binder.

[0191] 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 include at least one of conductive carbon black (super pll, abbreviated as SP), conductive graphite SFG-6, conductive graphite KS-6, acetylene black, branched superconducting carbon black Ketjen black (ECP), vapor grown carbon fiber (VGCF), carbon nanotubes (CNTs), graphene, and composite conductive agents thereof.

[0192] The binder can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS) and fluorine-containing acrylate resin.

[0193] Optionally, in the positive electrode active layer, the conductive agent accounts for 1% to 20% by mass.

[0194] Optionally, in the positive electrode active layer, the binder accounts for 1% to 10% by mass.

[0195] In some embodiments, the thickness of the positive electrode active layer is 30 μm to 200 μm.

[0196] 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.

[0197] In some embodiments, the metal material includes any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0198] 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).

[0199] In any embodiment of the present application, a positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing a positive electrode sheet in a solvent to form a positive electrode slurry; applying the positive electrode slurry to a current collector, and performing drying, cold pressing, and other processes to obtain a positive electrode sheet. The positive electrode slurry has a solid content of 40 wt% to 80 wt%, and a viscosity at room temperature adjusted to 5000 mPa·s to 25000 mPa·s. The positive electrode slurry is applied to the surface of the positive electrode current collector, dried, and then cold-pressed on a cold rolling mill to form a positive electrode sheet.

[0200] Further, the solvent includes N-methylpyrrolidone.

[0201] 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 .

[0202] Areal density of positive electrode active material = mass of positive electrode active material / area of ​​positive electrode sheet.

[0203] 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.

[0204] 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.

[0205] In some embodiments, the negative electrode sheet directly adopts a lithium-containing metal sheet.

[0206] In another embodiment, the negative electrode sheet includes a lithium-containing metal layer and a conductive layer stacked together.

[0207] 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.

[0208] 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).

[0209] In some embodiments, the conductive layer may be copper foil.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] The components of the negative electrode active layer include a negative electrode active material.

[0214] The negative electrode active material may be any commonly used negative electrode active material in this application.

[0215] In any embodiment of the present application, the above-mentioned negative electrode active material includes mesophase carbon 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, iron-based materials, metallic lithium, lithium metal and alloys formed by other metals or non-metallic elements; further, other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In) and platinum (Pt); non-metallic elements include at least one of boron (B), carbon (C) and silicon (Si).

[0216] 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.

[0217] 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%.

[0218] 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.

[0219] In any embodiment of the present application, the above-mentioned negative electrode conductive agent can be a conductive material commonly used in the art, including but not limited to: at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it can include at least one of conductive carbon black (super pll, referred to as SP), conductive graphite SFG-6, conductive graphite KS-6, acetylene black, branched superconducting carbon black Ketjen black (ECP), vapor grown carbon fiber (VGCF), carbon nanotubes (CNTs) and graphene and composite conductive agents thereof.

[0220] 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.

[0221] The negative electrode binder may be a binder commonly used in the art, and may include 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).

[0222] 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.

[0223] 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%.

[0224] 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.

[0225] 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.

[0226] In some embodiments, the metal material includes any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0227] 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).

[0228] 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.

[0229] In some embodiments, the solvent includes but is not limited to water.

[0230] 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.

[0231] 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 .

[0232] The area density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0233] Separator: The separator is placed between the positive electrode and the negative electrode.

[0234] 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.

[0235] In some embodiments, the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] The secondary battery includes one or more battery cells 4 .

[0242] 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.

[0243] 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.

[0244] The plurality of battery cells 4 can be arranged in the battery box in any manner.

[0245] The present application also provides an electrical device, which includes the above-mentioned secondary battery.

[0246] 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.

[0247] 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.

[0248] The above-mentioned electrical devices may be, but are not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc.

[0249] Mobile devices include but are not limited to: mobile phones, laptops, etc. Electric vehicles include but are not limited to: pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0250] 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 a secondary battery, a battery pack may be used.

[0251] 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 lightweight and thin, and may use a secondary battery as a power source.

[0252] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0253] The following are specific examples.

[0254] Example 1

[0255] S1. Preparation of lithium metal secondary batteries

[0256] (1) Preparation of electrolyte: A film-forming agent (difluoroethylene carbonate, DFEC), an organic solvent (ethyl methyl carbonate, EMC), 0.05 mol of the functional compound represented by formula (I), 0.1 mol of a first electrolyte salt (lithium hexafluorophosphate, LiPF6), and 0.03 mol of a second electrolyte salt (lithium difluorophosphate, LiPO2F2) were thoroughly mixed and dissolved to form a colorless and transparent electrolyte. The volume ratio of the film-forming agent to the organic solvent was 1:1.5.

[0257] The concentration of the first electrolyte salt is recorded as M1, and the calculation formula is as follows:

[0258] M1 = number of moles of salt of the first electrolyte / (total volume of organic solvent and film-forming agent)

[0259] The concentration of the second electrolyte salt in the electrolyte is recorded as M2, and the calculation formula is as follows:

[0260] M2 = number of moles of the second electrolyte salt / (total volume of the organic solvent and the film-forming agent)

[0261] The mass concentration of the functional compound is A, and the calculation formula is as follows:

[0262] A = moles of functional compound / (total volume of organic solvent and film-forming agent).

[0263] The volume ratio of film-forming agent to organic solvent is recorded as B, and the calculation formula is as follows:

[0264] B = Film-forming agent volume / organic solvent volume. See Table 1 for details.

[0265] Among them, ion chromatography testing is used to confirm the structure and content of each component in the electrolyte.

[0266] (2) Preparation of negative electrode sheet

[0267] A 50 μm lithium foil was rolled onto a 12 μm copper foil and then cut into a 41 mm × 51 mm rectangle for use as a negative electrode.

[0268] (3) Preparation of positive electrode

[0269] The lithium-rich manganese-based positive electrode active material (Li[Li 0.17 Mn 0.58 Ni 0.25 ]O2), conductive agent acetylene black, binder PVDF were mixed in a mass ratio of 98:1:1, solvent N-methylpyrrolidone (NMP) was added and stirred until the system became uniform to obtain a positive electrode slurry with a solid content of 70%; the positive electrode slurry was heated at about 25 mg / cm 2 The positive electrode was evenly coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying, and then cut into 40mm×50mm rectangles as positive electrode sheets.

[0270] (4) Isolation film: Use a polyethylene porous film and cut it into a 45mm×55mm rectangle for later use.

[0271] (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.

[0272] S2. Room temperature cycling performance test of lithium metal secondary batteries:

[0273] The prepared lithium metal secondary battery was tested at room temperature (25°C) using a charge rate of 0.2C (i.e., 30mA) and a discharge rate of 1C (i.e., 150mA). The cutoff voltages for charge and discharge were set at 4.6V and 2V, respectively. A constant current-constant voltage charging method was used. The specific charging process was as follows: after the 0.2C constant current charge reached a cutoff voltage of 4.6V, a constant voltage charge of 4.6V was continued until the current decayed to 0.1C (i.e., 15mA). One charge-discharge cycle was considered one cycle. The battery life was considered to have expired when the discharge capacity decayed to 80% of the initial discharge capacity, and the number of cycles, Cy@25°C, was recorded.

[0274] Please see Table 1 for specific results.

[0275] Examples 2 to 10

[0276] Examples 2 to 10 are basically the same as Example 1, with the only difference being that in step (1) the preparation of the electrolyte, the type of the regulating functional compound is different from that in Example 1.

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

[0278] Example 11

[0279] Example 11 is substantially the same as Example 1, except that in step (1) of preparing the electrolyte, lithium hexafluorophosphate is replaced with an equimolar amount of lithium bis(fluorosulfonyl)imide (LiFSI).

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

[0281] Examples 12 to 16

[0282] Examples 12 to 16 are basically the same as Example 1, with the only difference being that in step (1) preparing the electrolyte, the amount of the functional compound is regulated so that the concentration A is different from that in Example 1.

[0283] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0284] Examples 17 to 19

[0285] Examples 17 to 19 are basically the same as Example 1, except that in step (1) of preparing the electrolyte, the volume ratio B of the organic solvent and the film-forming agent is regulated differently from that in Example 1.

[0286] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0287] Examples 20 to 25

[0288] Examples 20 to 25 are substantially the same as Example 1, except that in step (1) of preparing the electrolyte, the concentration M1 of the first electrolyte salt or the mass proportion M2 of the second electrolyte salt is regulated differently from that in Example 1.

[0289] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0290] Comparative Example 1

[0291] Comparative Example 1 is substantially the same as Example 1, except that no functional compound is added in the preparation of the electrolyte in step (1).

[0292] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0293] Comparative Examples 2 to 5

[0294] Comparative Examples 2 to 5 are substantially the same as Example 1, except that in step (1) the preparation of the electrolyte, the type of functional compound is different from that in Example 1.

[0295] The other step conditions are the same as those in Example 1. The test results are shown in Table 1.

[0296] The structures of the functional compounds used in the examples and comparative examples are shown below:

[0297] The preparation process of formula (I) to formula (X) is as follows:

[0298] Formula (I): Under argon atmosphere, 0.2 mol of oxazolidin-2-one was added to 1 mol of tris(trimethylsilyl)phosphite at 0-5°C, and the mixture was stirred for 1 hour and allowed to react overnight. The solution was collected and purified to obtain the compound of formula (I).

[0299] Formula (II): Under argon atmosphere, 0.2 mol of oxazolidin-2-one and 1 mol of bis(trimethylsilyl)methylphosphite were stirred and mixed at 0-5°C for 1 hour. After reacting overnight, the liquid phase was purified to obtain the compound of formula (II).

[0300] Formula (III): Under an argon atmosphere, a 50% mass concentration of aqueous hydrobromic acid solution (2 mol) is added to 1 mol of diethyl cyanomethylphosphite, the mixture is stirred overnight, and the product is filtered to obtain bis(acetonitrile)ethyl phosphite; then, under an argon atmosphere, 1 mol of trimethylsilane is added to the product at 0-5°C, the reaction is stirred for 10 hours, and the phosphite is filtered to obtain bis(acetonitrile)trimethylsilicate. An equal molar amount of (E)-4-methoxybut-3-en-2-one is then added, and the reaction is stirred at 0°C overnight to obtain the compound of formula (III).

[0301] Formula (IV): Under an argon atmosphere, 1 mol of nitrosomethane is added to 1.5 mol of bis(trimethylsilyl)methylphosphite at 0-10°C, and 1 mol of (E)-4-methoxybut-3-en-2-one is added thereto. The mixture is stirred and reacted for 15 hours, and filtered to obtain the compound of formula (IV).

[0302] Formula (V): Under argon atmosphere, 1 mol of ethanolamine and 1 mol of oxazolidin-2-one were mixed at 0-10°C, stirred and reacted for 10 hours, and filtered to obtain intermediate 1: Add 1 mol of trimethylsilane to the intermediate product 1 and continue stirring for 10 hours to obtain the intermediate product 2: Then, 1 mol of trimethyl phosphite was added thereto, and the mixture was stirred and reacted for 10 h. The compound of formula (V) was obtained by filtration.

[0303] Formula (VI): Under argon atmosphere, at 0-10°C, add 1 mol of trimethylsilane and 1 mol of trimethyl phosphite to 1 mol of imino (3-carbonyl-1-butenyl), continue stirring and react for 10 hours, and filter to obtain the product compound of formula (VI).

[0304] Formula (VII): Under argon atmosphere, add 1 mol of nitrosomethane to 1 mol of dimethyltrimethylsilylphosphonate at 0-10°C, continue stirring and react for 10 hours, and filter to obtain the product compound of formula (VII).

[0305] Formula (VIII): Under argon atmosphere, 1 mol of N,N-dimethyltrimethylsilylamine and 1 mol of trimethyl phosphite were mixed, stirred continuously at 0-10°C for overnight reaction, and filtered to obtain the compound of formula (VIII).

[0306] Formula (IX): Under argon atmosphere, 1 mol of N-methyl, N-ethyltrimethylsilylamine and 1 mol of trimethyl phosphite were mixed, stirred continuously at 0-10°C for overnight reaction, and filtered to obtain the compound of formula (IX).

[0307] Formula (X): Under argon atmosphere, 1 mol of nitrosomethane and 1 mol of methylbis(trimethylsilyl)phosphite were mixed, stirred continuously at 0-10°C for overnight reaction, and filtered to obtain the compound of formula (X).

[0308] The parameters and relevant test results of each embodiment and comparative example are shown in Table 1.

[0309] Table 1

[0310] Wherein, “ / ” represents that the substance or parameter does not exist.

[0311] By analyzing the data in Table 1 and comparing the performance data of Examples 1 to 25 and Comparative Examples 1 to 5, it can be seen that the electrolyte of the present application can improve the cycle performance of the secondary battery.

[0312] 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.

[0313] The above-described embodiments merely represent several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make a number of variations and improvements without departing from the concept of the present application, and these variations and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the patent application 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, the components of which include a functional compound represented by formula (1): T1 to T3 are independently selected from an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkynyl group having 2 to 10 carbon atoms, and any one of the groups represented by the following formulae (a) to (f); among T1 to T3, at least one is selected from the group represented by formula (a), and at least one is selected from the group represented by formula (b), (c), (d) or (e); in, R1 to R3 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms, and an aryl group having 6 to 15 ring atoms, and at least one R1 is not H, and at least one R2 is not H; R4 to R6 are independently selected from a single bond, a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, or a substituted or unsubstituted alkenylene group having 2 to 5 carbon atoms; L1 is selected from a single bond or NR7, R7 is selected from H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms, an aryl group having 6 to 15 ring atoms, and Any one of, L2 is selected from a single bond or an alkylene group having 1 to 5 carbon atoms; X1 is C(R8)2, X2 is C(R9)2; each R8 and each R9 is independently selected from any one of H, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 5 carbon atoms, and a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms; * represents the ligation site.

2. The electrolyte according to claim 1, wherein The functional compound contains a nitrogen atom.

3. The electrolyte according to any one of claims 1 to 2, wherein The functional compound contains and at least one of the groups of formula (c).

4. The electrolyte according to any one of claims 1 to 3, wherein R1 to R3 are each independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, an alkenyl group having 2 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms substituted by halogen, an alkynyl group having 2 to 5 carbon atoms, and an alkynyl group having 2 to 5 carbon atoms substituted by halogen; Optionally, R1 to R3 are independently selected from any one of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, an alkenyl group having 2 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms substituted by halogen, an alkynyl group having 2 to 3 carbon atoms, and an alkynyl group having 2 to 3 carbon atoms substituted by halogen.

5. The electrolyte according to any one of claims 1 to 4, wherein R4 to R6 are each independently selected from any one of a single bond, an alkylene group having 1 to 5 carbon atoms, an alkylene group having 1 to 5 carbon atoms substituted by a halogen, an alkenylene group having 2 to 5 carbon atoms, and an alkenylene group having 2 to 5 carbon atoms substituted by a halogen; Optionally, R4 to R6 are independently selected from any one of a single bond, an alkylene group having 1 to 3 carbon atoms, an alkylene group having 1 to 3 carbon atoms substituted by halogen, an alkenylene group having 2 to 3 carbon atoms, and an alkenylene group having 2 to 3 carbon atoms substituted by halogen.

6. The electrolyte according to any one of claims 1 to 5, wherein R7 is selected from an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted with a halogen, and Any of the following; Optionally, R7 is selected from an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by a halogen, and Any one of .

7. The electrolyte according to any one of claims 1 to 6, wherein Each R8 and each R9 are independently selected from any one of H, an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted by halogen, and an alkenyl group having 2 to 5 carbon atoms, i.e. an alkenyl group having 2 to 5 carbon atoms substituted by halogen; Optionally, each R8 and each R9 are independently selected from any of H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted by halogen, and an alkenyl group having 2 to 3 carbon atoms, i.e., an alkenyl group having 2 to 3 carbon atoms substituted by halogen. A sort of.

8. The electrolyte according to any one of claims 1 to 7, wherein The functional compound includes at least one of the following (I) to (X):

9. The electrolyte according to any one of claims 1 to 8, wherein The components of the electrolyte also include electrolyte salt and organic solvent; Based on the total volume of the components in the electrolyte except the electrolyte salt and the functional compound, the concentration A of the functional compound satisfies: A≥0.05 mol / L; Optionally, 0.05mol / L≤A≤1mol / L; Further optionally, 0.25 mol / L≤A≤0.75 mol / L.

10. The electrolyte according to claim 9, wherein The components of the electrolyte also include a film former.

11. The electrolyte according to claim 10, wherein The volume ratio of the film-forming agent to the organic solvent is 1:(0.5-3); Optionally, the volume ratio of the film-forming agent to the organic solvent is 1:(1-3).

12. The electrolyte according to any one of claims 9 to 11, wherein The electrolyte salt includes a first electrolyte salt and a second electrolyte salt; The first electrolyte salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate; The second electrolyte salt includes lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonylimide), lithium trifluoromethanesulfonate, At least one of lithium difluorophosphate, lithium dioxalatoborate, lithium difluorooxalatoborate, lithium difluorodioxalatophosphate, lithium tetrafluorooxalatophosphate and lithium difluorophosphate.

13. The electrolyte according to claim 12, wherein The electrolyte salt satisfies at least one of the following conditions (1) to (2): (1) based on the total volume of the components in the electrolyte solution excluding the electrolyte salt and the functional compound, the concentration of the first electrolyte salt is 0.5 mol / L to 4 mol / L; (2) The concentration of the second electrolyte salt in the electrolyte is 0.05 mol / L to 1.5 mol / L based on the total volume of the components in the electrolyte except the electrolyte salt and the functional compound.

14. The electrolyte according to any one of claims 12 to 13, wherein The concentration of the first electrolyte salt is greater than the concentration of the second electrolyte salt.

15. A secondary battery comprising the electrolyte according to any one of claims 1 to 14.

16. An electric device comprising the secondary battery according to claim 15.

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