Electrolyte, secondary battery, and electric device

Abstract

The application relates to an electrolyte, a secondary battery and a power device, wherein the components of the electrolyte comprise a functional compound shown in formula (1), T1-T3 are independently selected from any one of the following groups: alkyl with 1-10 carbon atoms, alkenyl with 2-10 carbon atoms, alkynyl with 2-10 carbon atoms and groups shown in formula (a)-(f); and at least one of T1-T3 is selected from the group shown in formula (a), and at least one is selected from the group shown in formula (b), (c), (d) or (e). The functional compound shown in formula (1) can capture oxidation products in the charging and discharging process of the electrolyte, improve the toughness of the formed SEI film, and further improve the cycle performance of the secondary battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrolyte, a secondary battery and a power utilization device. BACKGROUND

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

[0003] Among them, lithium metal batteries have high theoretical energy density and low negative electrode potential, and are extremely potential secondary batteries. However, the performance improvement of lithium metal batteries is severely restricted by the electrolyte. The release of active oxygen often accompanies the charging and discharging process of the traditional electrolyte, which is easy to cause the oxidation reaction of the electrolyte, has a great negative impact on the key performance indicators such as the cycle performance of the battery, and even leads to safety accidents in severe cases.

[0004] Therefore, the traditional technology needs to be further improved. SUMMARY

[0005] Therefore, it is necessary to provide an electrolyte, a secondary battery and a power utilization device, which aims to improve the cycle performance of the secondary battery.

[0006] The present application is realized through the following technical solutions.

[0007] In a first aspect of the present application, an electrolyte is provided, and the components of the electrolyte include a functional compound represented by formula (1):

[0008]

[0009] T1-T3 are independently selected from any one of an alkyl group with a carbon atom number of 1-10, an alkenyl group with a carbon atom number of 2-10, an alkynyl group with a carbon atom number of 2-10, and groups represented by formulae (a)-(f) below; 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), formula (c), formula (d) or formula (e);

[0010]

[0011] wherein R1-R3 are independently selected from any one of H, a substituted or unsubstituted alkyl group with a carbon atom number of 1-5, a substituted or unsubstituted alkenyl group with a carbon atom number of 2-5, a substituted or unsubstituted alkynyl group with a carbon atom number of 2-5, and an aryl group with a ring atom number of 6-15, and at least one R1 is not H, and at least one R2 is not H;

[0012] 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;

[0013] L1 is selected from a single bond or NR7, and 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 L2 is selected from a single bond or an alkylene group having 1 to 5 carbon atoms;

[0014] X1 is C(R8)2, and X2 is C(R9)2; each R8 and each R9 are each independently 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, and a substituted or unsubstituted alkynyl group having 2 to 5 carbon atoms;

[0015] * represents a connection site.

[0016] The components of the above electrolyte solution contain functional compounds with specific structures. The compound shown in formula (1) contains a phosphite structure group, a silicon-containing group, and specific structures (b), (c), (d), or (e). The phosphite structure group has nucleophilicity, 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, increasing its toughness. Some of (b), (c), (d), or (e) contain nitrogen-containing functional groups with lone pair electrons, and some contain specific unsaturated structures, which can both capture acidic substances and facilitate the formation of the SEI film and improve its toughness. The organic combination of each specific structure enables the compound shown in formula (1) to capture oxidation products during the charging and discharging process of the electrolyte, while improving the toughness of the formed SEI film, thereby improving the cycle performance of the secondary battery.

[0017] In some embodiments, the functional compound contains a nitrogen atom.

[0018] The nitrogen atom has lone pair electrons, which can promote the formation of the SEI film.

[0019] In some embodiments, the functional compound contains and at least one of the groups of formula (c).

[0020] Research has found that when the compound shown in formula (1) contains or the group of formula (c), the toughness of the SEI film can be further improved, and the cycle performance of the battery can be improved.

[0021] In some embodiments, each of R1to R3is 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 with a halogen, an alkenyl group having 2 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms substituted with a halogen, an alkynyl group having 2 to 5 carbon atoms, and an alkynyl group having 2 to 5 carbon atoms substituted with a halogen;

[0022] Optionally, each of R1to R3is 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 with a halogen, an alkenyl group having 2 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms substituted with a halogen, an alkynyl group having 2 to 3 carbon atoms, and an alkynyl group having 2 to 3 carbon atoms substituted with a halogen.

[0023] In some embodiments, each of R4to R6is 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 with a halogen, an alkenylene group having 2 to 5 carbon atoms, and an alkenylene group having 2 to 5 carbon atoms substituted with a halogen;

[0024] Optionally, each of R4to R6is 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 with a halogen, an alkenylene group having 2 to 3 carbon atoms, and an alkenylene group having 2 to 3 carbon atoms substituted with a halogen.

[0025] In some embodiments, R7is selected from any one of an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted with a halogen, and

[0026] Optionally, R7is selected from any one of an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and

[0027] In some embodiments, each of R8and R9is 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 with a halogen, an alkenyl group having 2 to 5 carbon atoms, and an alkenyl group having 2 to 5 carbon atoms substituted with a halogen;

[0028] Optionally, each of R8and R9is 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 with a halogen, an alkenyl group having 2 to 3 carbon atoms, and an alkenyl group having 2 to 3 carbon atoms substituted with a halogen.

[0029] The functional compound includes at least one of the following (I) to (X):

[0030] ​​

[0031] In some embodiments, the components of the electrolyte further include an electrolyte salt and an organic solvent;

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

[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 components of the electrolyte further include 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] The film-forming agent can synergize with the organic solvent to adjust the solvation structure of lithium ions in the electrolyte, form a film on the electrode surface, and improve the coulombic efficiency and the 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 bisfluorosulfonylimide and lithium hexafluorophosphate;

[0041] The second electrolyte salt includes at least one of lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium difluoro bisoxalate phosphate, lithium tetrafluoro oxalate phosphate, and lithium difluorophosphate.

[0042] The specific first electrolyte salt and the second electrolyte salt synergize with each other, wherein the second electrolyte salt can regulate the morphology of lithium ion deposition, promote film formation, has high stability, can reduce the probability of electrolyte component decomposition and harmful side reactions, and further improve the cycle performance of the battery.

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

[0044] (1) The concentration of the first electrolyte salt is 0.5 mol / L-4 mol / L, based on the total volume of the components in the electrolyte except for the electrolyte salt and the functional compound;

[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 components other than the electrolyte salt and the functional compound in the electrolyte.

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

[0047] The content of the first electrolyte salt and the second electrolyte salt is further regulated to sufficiently exert the synergistic effect.

[0048] In a second aspect of the present application, a secondary battery is provided, the secondary battery including the electrolyte of the first aspect.

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

[0050] In a third aspect of the present application, an electric device is provided, the electric device including the secondary battery of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0051] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of preferred embodiments, and are not intended to limit the scope of the present application. Furthermore, like reference numerals are intended to denote like parts throughout all the drawings. In the drawings:

[0052] Figure 1 is a schematic view of an embodiment of a battery cell;

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

[0054] Figure 3 is a schematic view of an embodiment of a battery pack;

[0055] Figure 4 is an exploded view of Figure 3

[0056] Figure 5 is a schematic view of an embodiment of an electric device in which a battery is used as a power source.

[0057] BRIEF DESCRIPTION OF DRAWINGS

[0058] 1: battery pack; 2: upper case; 3: lower case; 4: battery cell; 41: case; 42: electrode assembly; 43: cover plate; 5: electric device. DETAILED DESCRIPTION

[0059] ​​The technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot be used to limit the protection scope of the present application.

[0060] In the description of the embodiments of the present application, the meaning of "a plurality of" is two and more than two, unless otherwise explicitly and specifically limited.

[0061] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. It is expressly understood that the embodiments described herein are merely examples from among a great variety of embodiments that can be claimed or otherwise used to implement the present application.

[0062] In the present application, the term "alkyl" refers to a group formed by removing one hydrogen from an alkane, for example, removing one hydrogen from methane to form a methyl group; similarly, "alkenyl or alkynyl" refers to a group formed by removing one hydrogen from an alkene or alkane, for example, removing one hydrogen from ethylene to form an ethenyl group, removing one hydrogen from acetylene to form an ethynyl group.

[0063] In the present application, the number of carbon atoms of "an alkyl group having 1 to 10 carbon atoms" can be 1 to 10, including 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and non-limiting examples include a methan group, an ethan group, a n-propan group.

[0064] In the present application, the term "alkylene" refers to a group formed by removing two hydrogens from an alkane, for example, removing two hydrogens from methane to form a methylene group; similarly, "alkenylene or alkynylene" refers to a group formed by removing two hydrogens from an alkene or alkane, for example, removing two hydrogens from ethylene to form an ethenylene group, removing two hydrogens from acetylene to form an ethynylene group.

[0065] The term "alkanyl" refers to a group formed by removing one hydrogen from an alkane in which all carbon atoms are connected by carbon-carbon single bonds and no ring is formed, and the remaining valence bonds are all combined with hydrogen, including straight-chain alkanyl groups and branched-chain alkanyl groups.

[0066] In the present application, the term "substituted or unsubstituted" means that the functional group described after the term can have or not have a substituent.

[0067] In the present application, halogen groups include chlorine, fluorine, bromine, and iodine.

[0068] In the present application, "aryl" refers to a hydrocarbon group containing at least one aromatic ring, including non-fused ring aryl groups and fused ring aryl groups. Fused ring aryl groups refer to groups formed by connecting two or more aromatic rings through two adjacent ring atoms shared, i.e., fused rings.

[0069] Aromatic ring refers to a cyclic hydrocarbon compound having aromaticity: that is, a hydrocarbon compound having a cyclic closed conjugated system.

[0070] In the present application, the "number of ring atoms" means the number of atoms bonded to form a ring, and when the ring is substituted with a substituent, the atoms included in the substituent are not included in the ring-forming atoms. The same applies to the "number of ring atoms" described below, unless otherwise specified. For example, the number of ring atoms of a benzene ring is 6, and the number of ring atoms of a naphthalene ring is 10.

[0071] In view of the above background, the performance improvement of conventional secondary batteries, especially lithium metal secondary batteries, is severely restricted by the electrolyte. The conventional electrolyte releases acidic by-products such as HF during charging and discharging, and therefore a functional additive containing silane is often used to capture acidic substances.

[0072] However, it has been found that merely capturing acidic substances has a very limited effect on the performance improvement of the battery. After a large number of experimental investigations, the electrolyte of the present application was obtained.

[0073] In an embodiment of the present application, an electrolyte is provided, and the components of the electrolyte include a functional compound represented by formula (1):

[0074]

[0075] 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 a group represented by formula (a)-(f) below; and 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), formula (c), formula (d), or formula (e);

[0076]

[0077] wherein R1-R3 are each independently selected from any one of H, a substituted or unsubstituted alkyl group having 1-5 carbon atoms, a substituted or unsubstituted alkenyl group having 2-5 carbon atoms, a substituted or unsubstituted alkynyl group having 2-5 carbon atoms, and an aryl group having 6-15 ring atoms, and at least one of R1 is not H, and at least one of R2 is not H;

[0078] R4-R6 are each independently selected from a single bond, a substituted or unsubstituted alkylene group having 1-5 carbon atoms, or a substituted or unsubstituted alkenylene group having 2-5 carbon atoms;

[0079] L1 is selected from a single bond or NR7, and R7 is selected from H, substituted or unsubstituted alkyl groups having 1 to 5 carbon atoms, substituted or unsubstituted alkenyl groups having 2 to 5 carbon atoms, substituted or unsubstituted alkynyl groups having 2 to 5 carbon atoms, aryl groups having 6 to 15 ring atoms, and so on. Any one of them, where L2 is selected from a single bond or an alkylene group having 1 to 5 carbon atoms;

[0080] X1 is C(R8)2, and X2 is C(R9)2; each R8 and each R9 is independently selected from any one of H, alkyl with 1 to 5 carbon atoms (substituted or unsubstituted), alkenyl with 2 to 5 carbon atoms (substituted or unsubstituted), and alkynyl with 2 to 5 carbon atoms (substituted or unsubstituted);

[0081] * represents a connection point.

[0082] The electrolyte components contain functional compounds with specific structures. The compound shown in formula (1) contains phosphite structural groups, silicon-containing groups, and specific structures (b), (c), (d), or (e). Among them, the phosphite structural groups are nucleophilic and can capture fluorine-containing byproducts formed by the oxidation of the electrolyte, while also having a certain flame retardancy. The silicon-containing groups capture acidic substances formed by the oxidation and decomposition of the electrolyte and can participate in the formation of the SEI film, 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 these can capture acidic substances while facilitating the formation of the SEI film and improving its toughness. The organic combination of these specific structures enables the compound shown in formula (1) to capture oxidation products during the charging and discharging process of the electrolyte, while improving the toughness of the formed SEI film, thereby improving the cycle performance of the secondary battery.

[0083] In some of these embodiments, the functional compound contains nitrogen atoms.

[0084] Nitrogen atoms have lone pairs of electrons, which can promote the formation of SEI films.

[0085] It can be understood that nitrogen-containing functional groups are introduced by selecting specific types of T1 to T3, i.e., nitrogen atoms are introduced; furthermore, the nitrogen-containing functional group can be at least one of the groups shown in formula (b), formula (d) and formula (e), or L1 can be the group shown in formula (a) selected from NR7.

[0086] In some embodiments, the functional compound contains At least one of the groups in formula (c).

[0087] Research has found that the compound shown in formula (1) contains When combined with the group of formula (c), the toughness of the SEI film can be further improved, thus enhancing the cycle performance of the battery.

[0088] Similarly, by selecting specific types of T1 to T3, we can introduce...

[0089] In some embodiments, 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 with halogen, an alkenyl group having 2 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms substituted with halogen, an alkynyl group having 2 to 5 carbon atoms substituted with halogen, and an alkynyl group having 2 to 5 carbon atoms substituted with halogen.

[0090] In some embodiments, 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 with halogen, an alkenyl group having 2 to 5 carbon atoms substituted with halogen, an alkenyl group having 2 to 5 carbon atoms substituted with halogen, an alkynyl group having 2 to 5 carbon atoms substituted with halogen, and an alkynyl group having 2 to 5 carbon atoms substituted with halogen.

[0091] Optionally, R1 to R3 are each independently selected from H, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with halogen, an alkenyl group having 2 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms substituted with halogen, an alkynyl group having 2 to 3 carbon atoms, and an alkynyl group having 2 to 3 carbon atoms substituted with halogen.

[0092] In some embodiments, R1 to R3 are each 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 with halogen, an alkenyl group having 2 to 3 carbon atoms substituted with halogen, an alkenyl group having 2 to 3 carbon atoms substituted with halogen, an alkynyl group having 2 to 3 carbon atoms substituted with halogen, and an alkynyl group having 2 to 3 carbon atoms substituted with halogen.

[0093] In some embodiments, R3 is selected from any one of the following: an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, an alkenyl group having 2 to 3 carbon atoms substituted with a halogen, an alkenyl group having 2 to 3 carbon atoms substituted with a halogen, and an alkyne group having 2 to 3 carbon atoms substituted with a halogen.

[0094] In some embodiments, R1 to R3 are each independently selected from any one of H, methyl, ethyl, n-propyl, isopropyl, halogen-substituted methyl, halogen-substituted ethyl, halogen-substituted n-propyl, halogen-substituted isopropyl, vinyl, propenyl, halogen-substituted vinyl, and halogen-substituted propenyl.

[0095] In some embodiments, 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 with halogen, an alkenyl group having 2 to 5 carbon atoms, and an alkenyl group having 2 to 5 carbon atoms substituted with halogen.

[0096] It is understandable that when R4, R5, or R6 is selected from single bonds, it means that the groups at both ends of R4, R5, or R6 are directly connected by single bonds.

[0097] In some embodiments, R4 to R6 are each 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 with halogen, a chain alkenyl group having 2 to 5 carbon atoms, and a chain alkenyl group having 2 to 5 carbon atoms substituted with halogen.

[0098] Optionally, R4 to R6 are each 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 with halogen, an alkenyl group having 2 to 3 carbon atoms, and an alkenyl group having 2 to 3 carbon atoms substituted with halogen.

[0099] In some embodiments, R4 to R6 are each 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 with halogen, a chain alkenyl group having 2 to 3 carbon atoms, and a chain alkenyl group having 2 to 3 carbon atoms substituted with halogen.

[0100] In some embodiments, R4 to R6 are each independently selected from any one of single bond, methylene, ethylene, propylene, isopropylene, halogen-substituted methylene, halogen-substituted ethylene, halogen-substituted propylene, halogen-substituted isopropylene, vinylene, propenylene, halogen-substituted vinylene, and halogen-substituted propenylene.

[0101] In some embodiments, R7 is selected from alkyl groups having 1 to 5 carbon atoms, alkyl groups having 1 to 5 carbon atoms that have been substituted with halogens, and... Any one of them.

[0102] In some embodiments, R7 is selected from alkyl groups having 1 to 5 carbon atoms, alkyl groups having 1 to 5 carbon atoms substituted with halogen, and... Any one of them.

[0103] Optionally, R7 is selected from alkyl groups having 1 to 3 carbon atoms, alkyl groups having 1 to 3 carbon atoms substituted with halogens, and... Any one of them.

[0104] In some embodiments, R7 is selected from alkyl groups having 1 to 3 carbon atoms, alkyl groups having 1 to 3 carbon atoms substituted with halogen, and... Any one of them.

[0105] In some embodiments, R7 is selected from methyl, ethyl, propyl, isopropyl, halogen-substituted methyl, halogen-substituted ethyl, halogen-substituted propyl, halogen-substituted isopropyl, and... Any one of them.

[0106] In some embodiments, L2 is selected from single bonds or chain alkylene groups having 1 to 5 carbon atoms.

[0107] In some of these embodiments, L2 is selected from single bonds or alkylene groups having 1 to 3 carbon atoms.

[0108] In some of these embodiments, L2 is selected from single bonds or chain alkylene groups having 1 to 3 carbon atoms.

[0109] In some of these embodiments, L2 is selected from single bonds, methyl, ethyl, n-propyl, or isopropyl.

[0110] In some embodiments, each R8 and each R9 is 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 with halogen, and an alkenyl group having 2 to 5 carbon atoms substituted with halogen.

[0111] In some embodiments, each R8 and each R9 is 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 with halogen, and an alkenyl group having 2 to 5 carbon atoms substituted with halogen.

[0112] Optionally, each R8 and each R9 are independently selected from any one of H, alkyl groups having 1 to 3 carbon atoms, alkyl groups having 1 to 3 carbon atoms substituted with halogen, and alkenyl groups having 2 to 3 carbon atoms substituted with halogen.

[0113] In some embodiments, each R8 and each R9 is 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 with halogen, and an alkenyl group having 2 to 3 carbon atoms substituted with halogen.

[0114] In some embodiments, each R8 and each R9 are independently selected from any one of H, methyl, ethyl, propyl, isopropyl, halogen-substituted methyl, halogen-substituted ethyl, halogen-substituted propyl, halogen-substituted isopropyl, vinyl, propenyl, halogen-substituted vinyl and halogen-substituted propenyl.

[0115] In some of these embodiments, each R8 may be the same or different.

[0116] In some of these embodiments, each R9 may be the same or different.

[0117] In some embodiments, the functional compound includes at least one of (I) to (X):

[0118]

[0119] It should be noted that the functional compounds shown in formula (1) of this application can be purchased from commercial sources or synthesized by referring to the preparation method below, with the preparation of compounds shown in formulas (I) to (X) as examples for illustration.

[0120] Formula (I): Under a protective atmosphere, oxazolidin-2-one and tris(trimethylsilyl)phosphite are subjected to a first substitution reaction to obtain compound (I).

[0121] In some embodiments, the molar ratio of oxazolidin-2-one to tris(trimethylsilyl)phosphite is (0.1–0.5):1.

[0122] In some embodiments, the first substitution reaction is carried out at 0–5°C; further, the first substitution reaction takes 10–24 h.

[0123] In some embodiments, after the substitution reaction is complete, a step of purifying the liquid product is also included.

[0124] Formula (II): The preparation method of Formula (II) is the same as that of Formula (I), except that tris(trimethylsilyl) phosphite is replaced with di(trimethylsilyl) methyl phosphite.

[0125] Formula (III): includes the following steps:

[0126] Under a protective atmosphere, hydrobromic acid is reacted with diethyl cyanomethyl phosphite to obtain bis(acetonitrile) ethyl phosphite bromide.

[0127] In some embodiments, hydrobromic acid is added as an aqueous solution of hydrobromic acid with a mass concentration of 40% to 50%.

[0128] In some of these embodiments, the molar ratio of hydrobromic acid to diethyl cyanomethyl phosphite is (1-2):1.

[0129] The structures of diethyl cyanomethyl phosphite and bis(acetonitrile) ethyl phosphite bromide are shown in (a) and (b) respectively:

[0130]

[0131] Under a protective atmosphere, bis(acetonitrile)ethyl phosphite was reacted with trimethylsilane at 0–5 °C, and the mixture was filtered to obtain bis(acetonitrile)trimethylsilicate phosphite.

[0132] Formula (III) can be obtained by reacting bis(acetonitrile)trimethyl phosphite with (E)-4-methoxybut-3-en-2-one at 0°C or below under a protective atmosphere.

[0133] Formula (IV): Under a protective atmosphere, nitrosomethane, di(trimethylsilyl)methyl phosphite, and (E)-4-methoxybut-3-en-2-one were reacted together at 0–10 °C, and the mixture was filtered to obtain the product of formula (IV).

[0134] In some of these embodiments, the reaction time is 10 to 15 hours.

[0135] In some of the embodiments, the molar ratio of nitrosomethane, di(trimethylsilyl)methyl phosphite and (E)-5-methoxypent-3-en-2-one is 1:(1-2):(1-2).

[0136] Formula (V): Ethanolamine and oxazolidin-2-one were reacted under a protective atmosphere at 0–10 °C, and the mixture was filtered to obtain intermediate 1, with the following structure:

[0137] Optionally, the mixing reaction time is 10h to 15h.

[0138] In some of these embodiments, the molar ratio of ethanolamine to oxazolidin-2-one is 1:(1-2).

[0139] Intermediate 1 was reacted with trimethylsilane in a second substitution reaction, and the mixture was stirred continuously for 10 hours to obtain intermediate 2.

[0140] In some of these embodiments, the second substitution reaction takes 10 to 15 hours.

[0141] Intermediate 2 was subjected to a substitution reaction with trimethyl phosphite to obtain formula (V).

[0142] 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) is obtained by filtration.

[0143] In some of these embodiments, the molar ratio of imino (3-carbonyl-1-butenyl), trimethylsilane, and trimethyl phosphite is 1:1:(1-2).

[0144] In some embodiments, the mixing reaction time is 10h to 15h.

[0145] Formula (VII): Under a protective atmosphere, dimethyltrimethylsilylphosphonate and nitrosomethane are mixed and reacted, and the product (VII) is obtained by filtration; further, the mixing reaction time is 10h to 15h.

[0146] In some of these embodiments, the molar ratio of dimethyltrimethoxyphosphonate to nitrosomethane is (1-2):1.

[0147] Formula (VIII): Under a protective atmosphere, N,N-dimethyltrimethylsilane and trimethylphosphite are mixed and reacted at 0-10°C, and the product (VIII) is obtained by filtration; further, the mixing reaction time is 10-20 h.

[0148] In some embodiments, the molar ratio of N,N-dimethyltrimethylsilane to trimethyl phosphite is 1:(1-2).

[0149] Formula (IX): Under a protective atmosphere, N-methyl, N-ethyltrimethylsilane and 1 mol of trimethyl phosphite are mixed and reacted at 0–10 °C, and the product (IX) is obtained by filtration. Further, the mixing reaction time is 10 h–20 h.

[0150] In some embodiments, the molar ratio of N-methyl, N-ethyltrimethylsilane to trimethyl phosphite is 1:(1-2).

[0151] Formula (X): Under a protective atmosphere, nitrosomethane and methyl bis(trimethylsilyl) phosphite are mixed and reacted at 0–10 °C, and the product (X) is obtained by filtration. Further, the mixing reaction time is 10 h–20 h.

[0152] In some embodiments, the molar ratio of nitrosomethane to methyl bis(trimethylsilyl) phosphite is 1:(1-2).

[0153] In this application, the functional compounds shown in formula (1) can all be prepared by referring to the above preparation process.

[0154] In this application, the "protective atmosphere" can be at least one of an inert gas and nitrogen.

[0155] Specifically, the aforementioned "protective atmosphere" includes at least one of argon and nitrogen.

[0156] In some embodiments, the electrolyte also includes an electrolyte salt and an organic solvent.

[0157] In some embodiments, the concentration A of the functional compound is satisfied as follows, based on the total volume of components in the electrolyte excluding electrolyte salts and functional compounds: A≥0.05mol / L.

[0158] In some of these embodiments, 0.05 mol / L ≤ A ≤ 1 mol / L.

[0159] In some of these embodiments, 0.25 mol / L ≤ A ≤ 0.75 mol / L.

[0160] The concentration of functional compounds can be adjusted to further improve the toughness of the formed SEI film, thereby improving the cycle performance of the secondary battery.

[0161] In the above "0.05 mol / L ≤ A ≤ 1 mol / L", the value of A includes the minimum and maximum values ​​within this 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: 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1 mol / L; or any range of two values, for example, 0.05 mol / L to 0.1 mol / L, 0.05 mol / L to 0.9 mol / L, 0.1 mol / L to 0.9 mol / L, 0.2 mol / L to 0.9 mol / L, 0.3 mol / L to 0.9 mol / L, 0.4 mol / L to 0.9 mol / L, 0.5 mol / L to 0.9 mol / L, 0.6 mol / L to 0.9 mol / L, 0.7 mol / L to 0.9 mol / L.

[0162] In some embodiments, the electrolyte also includes a film-forming agent.

[0163] In some embodiments, the volume ratio of the film-forming agent to the organic solvent is 1:(0.5-3).

[0164] In some embodiments, the volume ratio of the film-forming agent to the organic solvent is 1:(1-3).

[0165] 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.

[0166] In the above "1:(0.5~3)", the value includes the minimum and maximum value of the range, as well as every value between the minimum and maximum value. 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 any range of two values.

[0167] In this application, the organic solvents and film-forming agents can be various types of organic solvents and film-forming agents commonly used in the art. Examples of organic solvents and film-forming agents are provided herein in a non-limiting manner.

[0168] Organic solvents include at least one of ester solvents, ether solvents, sulfone solvents, and nitrile solvents; specifically, organic solvents include methyl ethyl 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 the following: 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, perfluoroisopropylmethyl 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.

[0169] In some embodiments, the film-forming agent includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, and difluoroethylene carbonate.

[0170] Optionally, based on the total mass of components in the electrolyte excluding electrolyte salts and functional compounds, the mass percentage of organic solvents is greater than or equal to 20%.

[0171] Organic solvents can adjust the solvation structure in the electrolyte and improve ionic conductivity.

[0172] In some embodiments, the electrolyte salt described above includes an electrolyte lithium salt.

[0173] 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 dioxalate borate, lithium difluorooxalate borate, lithium difluorodioxalate phosphate, lithium tetrafluorooxalate phosphate, and lithium difluorophosphate.

[0174] The battery employs a specific first electrolyte salt and a second electrolyte salt working in synergy. The second electrolyte salt can regulate the lithium-ion deposition morphology, promote film formation, and has high stability. It can also reduce the probability of electrolyte component decomposition and harmful side reactions, thereby further improving the battery's cycle performance.

[0175] 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 components in the electrolyte excluding the electrolyte salt and functional compounds.

[0176] In some embodiments, 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 components other than the electrolyte salt and functional compounds.

[0177] The values ​​in "0.5 mol / L to 4 mol / L" above include the minimum and maximum values ​​of this 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: 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L; or any range consisting of any two values.

[0178] The values ​​in "0.05 mol / L to 1.5 mol / L" above include the minimum and maximum values ​​of this 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: 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L; or any range of two values.

[0179] In some embodiments, the concentration of the first electrolyte salt is greater than the concentration of the second electrolyte salt.

[0180] Further regulate the content of the first and second electrolyte salts to fully leverage their synergistic effect.

[0181] In some embodiments, the total concentration of electrolyte salts is 0.5 mol / L to 5 mol / L, based on the total volume of components in the electrolyte excluding electrolyte salts and functional compounds.

[0182] According to one embodiment of this application, a secondary battery is provided, which includes an electrolyte of the first aspect.

[0183] In some embodiments, the secondary battery further includes a positive electrode, a negative electrode, and a separator.

[0184] In this application, the positive electrode, negative electrode, and separator can adopt systems commonly used in the art, and the following are examples of the positive electrode, negative electrode, and separator.

[0185] Positive electrode: The positive electrode includes a current collector and a positive active layer loaded on the surface of the current collector.

[0186] The positive electrode active layer comprises a positive electrode active material. The positive electrode active material may be any commonly used positive electrode active material 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.

[0187] The positive electrode active materials for lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries are referred to as lithium-ion active materials, sodium-ion active materials, and potassium-ion active materials, respectively, below.

[0188] Further, as an example, lithium-ion active materials may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4, abbreviated as LFP), lithium manganese phosphate (such as LiMnPO4), and lithium manganese iron phosphate. In any embodiment of this application, the molecular formula of the lithium-ion active material is: LiFe x Mn (1-x) PO4, where x takes any number from 0 to 1.

[0189] It is understandable that when x is 0, LiFe x Mn (1-x) PO4 is LiMnPO4, which is lithium manganese phosphate. When x is 1, LiFe x Mn (1-x) PO4 is LiFePO4, which stands for lithium iron phosphate (LFP).

[0190] It should be noted that the lithium content in the cathode material mentioned above refers to its content when it is not in use. During battery use, it will be repeatedly charged, and the Li in the cathode active material will change during the charging and discharging process. That is, the molar subscript of Li in the cathode active material of the battery product will not always remain at 1, but will change; further, the range of change can be (0 to 1.2).

[0191] For example, LiFe x Mn (1-x) PO4 can be further represented as Li y Fe x Mn (1-x) PO4, y is 0 to 1.1.

[0192] For example, regarding the ternary material Li y (Ni a Co b Mn c ) 1-d M d O 2-x A x y is 0.2 to 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.

[0193] During the charging and discharging process, Li will be extracted and consumed. The molar content of Li will be different when the battery is discharged to different states. The above limitation on y includes the molar content of Li in different charging and discharging states of the battery. Furthermore, the battery voltage is usually between 2-5V.

[0194] In any embodiment of this application, the mass percentage of the positive electrode active material in the positive electrode active layer is 70% to 99.8%.

[0195] In any embodiment of this application, the components of the positive electrode active layer further include a conductive agent and a binder.

[0196] The conductive agent can be a 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, it may include at least one of conductive carbon black (super pll, abbreviated as SP), conductive graphite SFG-6, conductive graphite KS-6, acetylene black, superconducting carbon black with a branched structure, Ketjen black (ECP), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), and graphene and their composite conductive agents.

[0197] The adhesive may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-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 fluorinated acrylate resins.

[0198] Optionally, the conductive agent accounts for 1% to 20% of the mass in the positive electrode active layer.

[0199] Optionally, the binder accounts for 1% to 10% of the mass of the positive electrode active layer.

[0200] In some embodiments, the thickness of the positive electrode active layer is 30 μm to 200 μm.

[0201] In any embodiment of this 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate.

[0202] In some embodiments, the metallic material includes any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0203] 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).

[0204] In any embodiment of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto a current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solid content of the positive electrode slurry is 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s. The positive electrode slurry is coated onto the surface of the positive electrode current collector, dried, and then cold-pressed using a cold rolling mill to form the positive electrode sheet.

[0205] Furthermore, the solvent includes N-methylpyrrolidone.

[0206] In some embodiments, the areal density of the positive electrode active material contained in the positive electrode sheet is 0.018 g / cm³. 2 ~0.05g / cm2 .

[0207] The areal density of the positive electrode active material = the mass of the positive electrode active material / the area of ​​the positive electrode sheet.

[0208] Negative electrode: The negative electrode can adopt the negative electrode system of various secondary batteries commonly used in this field. The following are examples of lithium-ion secondary batteries and lithium metal secondary batteries, but are not limited to the following types.

[0209] In some embodiments, the secondary battery is a lithium metal secondary battery, and the negative electrode can be a negative electrode known in the art that can be used in lithium metal batteries.

[0210] In some embodiments, the negative electrode is directly made of lithium-containing metal sheet.

[0211] In another embodiment, the negative electrode includes a lithium-containing metal layer and a conductive layer stacked together.

[0212] Furthermore, the lithium-containing technology in the lithium-containing metal sheet and lithium-containing metal layer can be lithium metal or an alloy formed by lithium metal and other metal or non-metal elements.

[0213] Furthermore, other metals include at least one of tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), and foil (Pt); non-metallic elements include at least one of boron (B), carbon (C), and silicon (Si).

[0214] In some embodiments, the conductive layer may be copper foil.

[0215] In any embodiment of this application, the above-mentioned negative electrode sheet can be prepared by directly pressing a lithium-containing metal sheet to obtain a negative electrode sheet, or by stacking and pressing the above-mentioned lithium-containing metal layer and conductive layer together.

[0216] In some embodiments, the secondary battery is a lithium-ion secondary battery, and the negative electrode can be a negative electrode known in the art that can be used in lithium-ion secondary batteries.

[0217] In some embodiments, the negative electrode includes a current collector and a negative electrode active layer loaded on the surface of the current collector.

[0218] The components of the negative electrode active layer include negative electrode active materials.

[0219] The aforementioned negative electrode active material can be any commonly used negative electrode active material described in this application.

[0220] In any embodiment of this application, the aforementioned negative electrode active material includes mesophase carbon microspheres, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fibers, hard carbon, soft carbon, silicon-based materials, tin-based materials, magnesium-based materials, iron-based materials, lithium metal, lithium metal, and alloys formed by other metals or non-metals; 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-metals include at least one of boron (B), carbon (C), and silicon (Si).

[0221] Optionally, specific examples of the above-mentioned negative electrode active materials include, but are not limited to, at least one of the following: mesophase carbon microspheres, 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.

[0222] In any embodiment of this application, the mass percentage of the above-mentioned negative electrode active material in the negative electrode active layer is 70% to 100%.

[0223] In any embodiment of this application, the components of the above-mentioned negative electrode active layer further include a negative electrode conductive agent and a negative electrode binder.

[0224] In any embodiment of this application, the aforementioned negative electrode conductive agent can be a commonly used conductive material in the art, including but not limited to at least one of graphite, carbon nanotubes, nanofibers, carbon black, and graphene. Specifically, it may include at least one of conductive carbon black (super pll, abbreviated as SP), conductive graphite SFG-6, conductive graphite KS-6, acetylene black, superconducting carbon black with a branched structure, Ketjen black (ECP), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), and graphene and their composite conductive agents.

[0225] Based on the total weight of the negative electrode active layer, the weight ratio of the negative electrode conductive agent in the negative electrode active layer is 0–20 wt%.

[0226] The aforementioned negative electrode binder may be a commonly used binder 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).

[0227] Based on the total weight of the negative electrode active layer, the weight ratio of the negative electrode binder in the negative electrode active layer is 0–30 wt%.

[0228] In any embodiment of this application, the negative electrode active layer may optionally include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na). Based on the total weight of the negative electrode active layer, the weight ratio of other additives in the negative electrode active layer is 0 to 15 wt%.

[0229] In any embodiment of this application, the current collector in the negative electrode can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil.

[0230] Composite current collectors may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. Composite current collectors can be formed by forming a metal material on a polymer substrate.

[0231] In some embodiments, the metallic material includes any one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.

[0232] 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).

[0233] In any embodiment of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0234] In some embodiments, the solvents mentioned above include, but are not limited to, water.

[0235] In some embodiments, the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at 25°C is adjusted to 2000mPa·s to 10000mPa·s.

[0236] In some embodiments, the areal density of the negative electrode active material contained in the negative electrode sheet is 0.005 g / cm³. 2 ~0.03g / cm 2 .

[0237] The areal density of the negative electrode active material = the mass of the negative electrode active material / the area of ​​the negative electrode sheet.

[0238] Separator: The separator is placed between the positive electrode and the negative electrode.

[0239] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0240] In some embodiments, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0241] Optionally, the separator can be a single-layer film or a multi-layer composite film. Furthermore, when the separator is a multi-layer composite film, the materials of each layer can be the same or different.

[0242] In some embodiments, the thickness of the separator is 2 μm to 15 μm; alternatively, the thickness of the separator is 2 μm to 13 μm.

[0243] The secondary battery of this application can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The cell 4 is a secondary battery with a square structure, serving as an example.

[0244] In some embodiments, refer to Figure 2 The outer casing may include a housing 41 and a cover plate 43. The housing 41 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 41 has an opening communicating with the receiving cavity, and the cover plate 43 can be placed over the opening to close the receiving cavity.

[0245] The positive electrode, negative electrode, and separator can be formed into electrode assembly 42 by winding or stacking processes. Electrode assembly 42 is encapsulated within a receiving cavity. Electrolyte is immersed in electrode assembly 42. The number of electrode assemblies 42 contained in a single battery cell 4 can be one or more, and can be adjusted according to requirements.

[0246] A secondary battery comprises one or more battery cells 4.

[0247] The 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.

[0248] Figure 3 and Figure 4 Here is an example of a battery pack 1. The battery pack 1 includes a battery box and one or more battery cells 4 disposed in the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 being able to cover the lower box 3 and form an enclosed space for the battery cells 4.

[0249] Multiple battery cells 4 can be arranged in the battery box in any way.

[0250] This application also provides an electrical device that includes the aforementioned secondary battery.

[0251] Furthermore, in the aforementioned electrical device, the secondary battery can exist in the form of a single battery cell, or it can be further assembled into a battery pack.

[0252] The aforementioned 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.

[0253] The aforementioned electrical devices may include, but are not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.

[0254] Mobile devices include, but are not limited to: mobile phones, laptops, etc., and 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.

[0255] Figure 5 This is an example of an electrical device 5. This electrical device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this electrical device 5, a battery pack can be used.

[0256] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0257] The present application will be described below with reference to specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the appended 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.

[0258] The following are specific examples.

[0259] Example 1

[0260] S1. Preparation of lithium metal secondary batteries

[0261] (1) Preparation of electrolyte: Take film-forming agent (ethylene difluorocarbonate, DFEC), organic solvent (ethyl methyl carbonate, EMC), 0.05 mol of the functional compound shown in formula (I), 0.1 mol of the first electrolyte salt (lithium hexafluorophosphate, LiPF6), and 0.03 mol of the second electrolyte salt (lithium difluorophosphate, LiPO2F2) and mix them thoroughly to form a colorless and transparent electrolyte. The volume ratio of film-forming agent to organic solvent is 1:1.5.

[0262] The concentration of the first electrolyte salt is denoted as M1, and the calculation formula is as follows:

[0263] M1 = Number of moles of salt in the first electrolyte / (Total volume of organic solvent and film-forming agent)

[0264] The concentration of the second electrolyte salt in the electrolyte is denoted as M2, and the calculation formula is as follows:

[0265] M2 = Number of moles of the second electrolyte salt / (Total volume of organic solvent and film-forming agent)

[0266] Let A be the mass concentration of the functional compound. The calculation formula is as follows:

[0267] A = number of moles of functional compound / (total volume of organic solvent and film-forming agent).

[0268] The volume ratio of film-forming agent to organic solvent is denoted as B, and the calculation formula is as follows:

[0269] B = Volume of film-forming agent / Volume of organic solvent. See Table 1 for details.

[0270] Ion chromatography was used to confirm the structure and content of each component in the electrolyte.

[0271] (2) Preparation of negative electrode

[0272] A 50μm lithium foil is rolled onto a 12μm copper foil and then cut into 41mm×51mm rectangles for use as negative electrode sheets.

[0273] (3) Preparation of positive electrode

[0274] Lithium-rich manganese-based cathode active material (Li[Li 0.17 Mn 0.58 Ni 0.25 O2), conductive agent acetylene black, and binder PVDF are mixed at a mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) solvent is added and stirred until the system is homogeneous to obtain a positive electrode slurry with a solid content of 70%. The positive electrode slurry is then mixed at approximately 25 mg / cm³. 2 The load is evenly coated on both surfaces of the positive current collector aluminum foil, air-dried at room temperature, then transferred to an oven for further drying, and then cut into 40mm×50mm rectangles as the positive electrode.

[0275] (4) Separation membrane: Polyethylene porous membrane is selected and cut into rectangles of 45mm×55mm for later use.

[0276] (5) Assembly of lithium metal secondary battery: Take a cut positive electrode sheet and a cut negative electrode sheet and match them. Use the above-mentioned separator 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 prepared electrolyte, vacuum heat-press the aluminum-plastic film bag and let it stand at room temperature for 6 hours to obtain a lithium metal secondary battery with a rated capacity of 140mAh.

[0277] S2, Room temperature cycling performance test of lithium metal secondary batteries:

[0278] Take the prepared lithium metal secondary battery and set the test temperature to room temperature (25℃). Charge at a rate of 0.2C (30mA) and discharge at a rate of 1C (150mA). Set the cutoff voltages for charging and discharging to 4.6V and 2V respectively. Use a constant current-constant voltage charging method. Specifically, after the 0.2C constant current charging reaches the cutoff voltage of 4.6V, continue charging at 4.6V until the current decreases to 0.1C (15mA). One charge-discharge cycle is considered one cycle. When the discharge capacity decreases to 80% of the first cycle's discharge capacity, the battery life is considered to have ended, and the cycle number Cy@25℃ is recorded.

[0279] Please see Table 1 for the specific results.

[0280] Examples 2-10

[0281] Examples 2 to 10 are basically the same as Example 1, except that the types of regulatory functional compounds in step (1) of electrolyte preparation are different from those in Example 1.

[0282] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0283] Example 11

[0284] Example 11 is basically the same as Example 1, except that in step (1) electrolyte preparation, lithium hexafluorophosphate is replaced with an equimolar amount of lithium bisfluorosulfonylimide (LiFSI).

[0285] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0286] Examples 12-16

[0287] Examples 12-16 are basically the same as Example 1, except that in step (1) the preparation of the electrolyte, the amount of functional compound is adjusted so that the concentration A is different from that in Example 1.

[0288] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0289] Examples 17-19

[0290] Examples 17-19 are basically the same as Example 1, except that the volume ratio B of organic solvent and film-forming agent in step (1) electrolyte preparation is different from that in Example 1.

[0291] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0292] Examples 20-25

[0293] Examples 20-25 are basically the same as Example 1, except that in step (1) preparation of electrolyte, the concentration M1 of the first electrolyte salt or the mass ratio M2 of the second electrolyte salt are different from those in Example 1.

[0294] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0295] Comparative Example 1

[0296] Comparative Example 1 is basically the same as Example 1, except that no functional compound is added in step (1) of preparing the electrolyte.

[0297] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0298] Comparative Examples 2-5

[0299] Comparative Examples 2-5 are basically the same as Example 1, except that in step (1) the preparation of the electrolyte, the types of functional compounds are different from those in Example 1.

[0300] The other steps and conditions are the same as in Example 1. The test results are shown in Table 1.

[0301] The structures of the functional compounds used in the agents of each embodiment and the comparative examples are shown below:

[0302]

[0303]

[0304] The preparation processes of formulas (I) to (X) are as follows:

[0305] Formula (I): Under an argon atmosphere, 0.2 mol of oxazolidin-2-one was added to 1 mol of tris(trimethylsilyl) phosphite at 0–5 °C. After stirring for 1 h, the reaction was allowed to proceed overnight. The solution was then purified to obtain compound (I).

[0306] Formula (II): Under an argon atmosphere, 0.2 mol of oxazolidin-2-one and 1 mol of di(trimethylsilyl)methyl phosphite were stirred and mixed for 1 h at 0–5 °C. After reacting overnight, the liquid phase was purified to obtain compound (II).

[0307] Formula (III): Under an argon atmosphere, 2 mol of 50% (w / w) aqueous solution of hydrobromic acid was added to 1 mol of diethyl cyanomethyl phosphite and stirred overnight. The product was filtered to obtain bis(acetonitrile) ethyl phosphite. Then, under an argon atmosphere, 1 mol of trimethylsilane was added to the product at 0–5 °C and stirred for 10 h. The product was filtered to obtain bis(acetonitrile) trimethyl silicate phosphite. Then, an equimolar amount of (E)-4-methoxybut-3-en-2-one was added and stirred overnight at 0 °C to obtain compound (III).

[0308] Formula (IV): Under an argon atmosphere, 1 mol of nitrosomethane was added to 1.5 mol of di(trimethylsilyl)methyl phosphite at 0–10 °C, and 1 mol of (E)-4-methoxybut-3-en-2-one was added to it. The mixture was stirred continuously for 15 hours, and then filtered to obtain compound (IV).

[0309] Formula (V): Under an argon atmosphere, 1 mol of ethanolamine and 1 mol of oxazolidin-2-one were mixed at 0–10 °C and stirred continuously for 10 h. The mixture was then filtered to obtain intermediate product 1. 1 mol of trimethylsilane was added to intermediate 1, and the mixture was stirred continuously for 10 h to obtain intermediate 2. Then add 1 mol of trimethyl phosphite, stir continuously for 10 h, and filter to obtain compound (V).

[0310] Formula (VI): Under an argon atmosphere, at 0–10 °C, 1 mol of trimethylsilane and 1 mol of trimethyl phosphite were added to 1 mol of imino (3-carbonyl-1-butenyl), and the mixture was stirred continuously for 10 h. The product compound (VI) was obtained by filtration.

[0311] Formula (VII): Under an argon atmosphere, 1 mol of nitrosomethane is added to 1 mol of dimethyltrimethylsilylphosphonate at 0–10 °C, and the mixture is stirred continuously for 10 h. The product compound (VII) is obtained by filtration.

[0312] Formula (VIII): Under an argon atmosphere, 1 mol of N,N-dimethyltrimethylsilane and 1 mol of trimethyl phosphite are mixed and stirred overnight at 0–10 °C. The mixture is then filtered to obtain compound (VIII).

[0313] Formula (IX): Under an argon atmosphere, 1 mol of N-methyl,N-ethyltrimethylsilane and 1 mol of trimethyl phosphite are mixed and stirred overnight at 0–10 °C. The mixture is then filtered to obtain compound (IX).

[0314] Formula (X): Under an argon atmosphere, 1 mol of nitrosomethane and 1 mol of methyl bis(trimethylsilyl) phosphite are mixed and stirred overnight at 0–10 °C. The compound of formula (X) is obtained by filtration.

[0315] Please refer to Table 1 for the parameters and related test results involved in each embodiment and comparative example.

[0316] Table 1

[0317]

[0318]

[0319] In this context, " / " indicates that the substance or parameter does not exist.

[0320] Analysis of the data in Table 1 and comparison of the performance data of Examples 1-25 and Comparative Examples 1-5 show that the electrolyte of this application can improve the cycle performance of secondary batteries.

[0321] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0322] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. An electrolyte, characterized by, The electrolyte includes a functional compound represented by formula (1): ， T1~T3 are 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 formulae (a)~(f) below; at least one of T1~T3 is selected from the group represented by formula (a), and at least one is selected from the groups represented by formulae (b), (c), (d), or (e); ， wherein R1~R3 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1~5 carbon atoms, a substituted or unsubstituted alkenyl group having 2~5 carbon atoms, a substituted or unsubstituted alkynyl group having 2~5 carbon atoms, and an aryl group having 6~15 ring atoms, and at least one of R1 is not H, and at least one of R2 is not H; R4~R6 are independently selected from a single bond, a substituted or unsubstituted alkylene group having 1~5 carbon atoms, or a substituted or unsubstituted alkenylene group having 2~5 carbon atoms; L1is selected from a single bond or NR7, R7is selected from H, substituted or unsubstituted alkyl of 1 to 5 carbon atoms, substituted or unsubstituted alkenyl of 2 to 5 carbon atoms, substituted or unsubstituted alkynyl of 2 to 5 carbon atoms, aryl of 6 to 15 ring atoms, and any one of the group consisting of -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2-, -CH X1 is C(R8)2, and X2 is C(R9)2; each R8 and each R9 are independently selected from any one of H, a substituted or unsubstituted alkyl group having 1~5 carbon atoms, a substituted or unsubstituted alkenyl group having 2~5 carbon atoms, and a substituted or unsubstituted alkynyl group having 2~5 carbon atoms; * represents a connection site.

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

3. The electrolyte of claim 1, wherein The functional compound contains at least one of the groups of formula (c).

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

5. The electrolyte of claim 4, wherein R1~R3 are independently selected from any one of H, an alkyl group having 1~3 carbon atoms, a halogen-substituted alkyl group having 1~3 carbon atoms, an alkenyl group having 2~3 carbon atoms, a halogen-substituted alkenyl group having 2~3 carbon atoms, an alkynyl group having 2~3 carbon atoms, and a halogen-substituted alkynyl group having 2~3 carbon atoms.

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

7. The electrolyte of claim 6, wherein R4~R6 are independently selected from any one of a single bond, an alkylene group having 1~3 carbon atoms, a halogen-substituted alkylene group having 1~3 carbon atoms, an alkenylene group having 2~3 carbon atoms, and a halogen-substituted alkenylene group having 2~3 carbon atoms.

8. The electrolyte according to any one of claims 1 to 3, wherein R7is selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms substituted with a halogen, and any one of the group consisting of 9. The electrolyte of claim 8, wherein R7is selected from the group consisting of an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms substituted with a halogen, and any one of the group consisting of 10. The electrolyte according to any one of claims 1 to 3, wherein Each R8 and each R9 are independently selected from any one of H, an alkyl group having 1~5 carbon atoms, a halogen-substituted alkyl group having 1~5 carbon atoms, an alkenyl group having 2~5 carbon atoms, and a halogen-substituted alkenyl group having 2~5 carbon atoms.

11. The electrolyte of claim 10, wherein Each R8 and each R9 are independently selected from any one of H, an alkyl group having 1~3 carbon atoms, a halogen-substituted alkyl group having 1~3 carbon atoms, an alkenyl group having 2~3 carbon atoms, and a halogen-substituted alkenyl group having 2~3 carbon atoms.

12. The electrolyte according to any one of claims 1 to 3, wherein The functional compound includes at least one of (I) to (X) below: 。 13. The electrolyte according to any one of claims 1 to 3, wherein The components of the electrolyte solution further include an electrolyte salt and an organic solvent. A concentration A of the functional compound satisfies A ≥ 0.05 mol / L, based on the total volume of components in the electrolyte solution other than the electrolyte salt and the functional compound.

14. The electrolyte of claim 13, wherein, 0.05 mol / L ≤ A ≤ 1 mol / L.

15. The electrolyte of claim 14, wherein, 0.25 mol / L ≤ A ≤ 0.75 mol / L.

16. The electrolyte of claim 13, wherein The components of the electrolyte solution further include a film former.

17. The electrolyte of claim 16, wherein A volume ratio of the film former to the organic solvent is 1: (0.5 to 3).

18. The electrolyte of claim 17, wherein, A volume ratio of the film former to the organic solvent is 1: (1 to 3).

19. The electrolyte of claim 13, wherein The electrolyte salt includes a first electrolyte salt and a second electrolyte salt. The first electrolyte salt includes at least one of lithium bisfluorosulfonylimide and lithium hexafluorophosphate. The second electrolyte salt includes at least one of lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium bisoxalate borate, lithium difluoro bisoxalate borate, lithium difluoro bisoxalate phosphate, lithium tetrafluoro oxalate phosphate, and lithium difluorophosphate.

20. The electrolyte of claim 19, wherein, The electrolyte salt satisfies at least one of (1) to (2) below: (1) A concentration of the first electrolyte salt is 0.5 mol / L to 4 mol / L, based on the total volume of components in the electrolyte solution other than the electrolyte salt and the functional compound; (2) A concentration of the second electrolyte salt is 0.05 mol / L to 1.5 mol / L in the electrolyte solution, based on the total volume of components in the electrolyte solution other than the electrolyte salt and the functional compound.

21. The electrolyte of claim 20, wherein, The concentration of the first electrolyte salt is greater than the concentration of the second electrolyte salt.

22. A secondary battery characterized by comprising: The secondary battery includes the electrolyte solution according to any one of claims 1 to 21.

23. An electrical device, comprising: The electric device includes the secondary battery according to claim 22.

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