Electrolyte additive and application thereof

Abstract

The invention provides an electrolyte additive and application thereof, the electrolyte additive comprises a pyrrolidine nitrate compound, and the pyrrolidine nitrate compound has a structure as shown in a formula I: # imgabs0 # formula I, wherein R1, R2, R3, R4, R5 and R6 are respectively and independently selected from one of hydrogen, halogen, linear alkyl, substituted linear alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, heterocyclic group, substituted heterocyclic group and the like. According to the electrolyte additive disclosed by the invention, the nitrate anions and the pyrrolidinyl cations are contained, and the nitrate anions can form SEI on a negative electrode to improve the stability of a negative electrode interface and enter a solvation structure of lithium ions in the electrolyte to reduce the desolvation energy of the lithium ions; meanwhile, nitrate ions and pyrrolidinyl cations both have excellent oxidation resistance and can be compatible with a high-voltage positive electrode, so that the fast charging performance of the battery is improved on the premise of not sacrificing the service life of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to an electrolyte additive for improving lifespan and fast charging performance and its application. Background Art

[0002] In order to improve the fast charging performance of lithium-ion batteries, it is necessary to optimize the overall internal resistance of lithium-ion batteries. At present, there are related technologies that start from the electrolyte level, by improving the ionic conductivity of the electrolyte, reducing the desolvation energy of lithium ions or reducing the electrode / electrolyte interface impedance to optimize the overall internal resistance of lithium-ion batteries. For example, by using linear carboxylate solvents to replace carbonate solvents, or using LiFSI to partially replace LiPF6, etc., the ionic conductivity of the electrolyte is improved, the internal resistance is reduced, and the fast charging performance of the lithium-ion battery is improved to a certain extent. However, the inventors found that the poor film-forming properties of carboxylate solvents will reduce the stability of the negative electrode / electrolyte interface, resulting in a decrease in the life of the lithium-ion battery; and LiFSI will corrode the positive electrode aluminum current collector at high potential, which will also lead to a decrease in the life of the lithium-ion battery.

[0003] Therefore, how to improve the fast charging performance of lithium-ion batteries without sacrificing the battery life (or even improve the battery life) is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] In view of this, one object of the present application is to provide an electrolyte additive, which contains a pyrrolidine nitrate compound, wherein nitrate ions can form SEI on the surface of the negative electrode, improve the stability of the negative electrode interface, and reduce the interfacial impedance, and on the other hand, can enter the solvation structure of lithium ions in the electrolyte, weaken the interaction between lithium ions and the solvent, and reduce the desolvation energy of lithium ions; at the same time, nitrate ions and substituted or unsubstituted pyrrolidine cations have excellent oxidation resistance and are compatible with high-voltage positive electrodes, and nitrate ions and substituted or unsubstituted pyrrolidine cations can be adsorbed on the surface of the aluminum current collector, inhibiting the corrosion of LiFSI on the aluminum current collector, so that LiFSI can replace LiPF6 in a large proportion, thereby improving the overall life and fast charging performance of the lithium-ion battery.

[0005] Another object of the present application is to provide an electrolyte.

[0006] Yet another object of the present application is to provide an electrochemical device.

[0007] Yet another object of the present application is to provide a vehicle.

[0008] The first aspect of the present application provides an electrolyte additive, comprising a pyrrolidine nitrate compound, wherein the pyrrolidine nitrate compound has a structure shown in Formula I:

[0009]

[0010] wherein R1, R2, R3, R4, R5, and R6 are each independently selected from one of hydrogen, halogen, linear alkyl, substituted linear alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, heterocyclic group, substituted heterocyclic group, aryl, substituted aryl, ester group, substituted ester group, silanoxy, substituted silanoxy, silanyl, or substituted silanyl; and the substituents in the substituted linear alkyl, substituted branched alkyl, substituted alkoxy, substituted heterocyclic group, substituted aryl, substituted ester group, substituted silanoxy, and substituted silanyl groups all include C 1-10 One of alkyl, halogen, nitro, cyano, and sulfonic acid groups.

[0011] In some embodiments, the R1, R2, R3, R4, R5, and R6 are each independently selected from hydrogen, halogen, C 1-10 Straight chain alkyl, substituted C 1-10 Straight chain alkyl, C 3-10 Branched alkyl, substituted C 3-10 Branched alkyl, C 1-10 Alkoxy, substituted C 1-10 Alkoxy, C 3-6 Heterocyclic group, substituted C 3-6 Heterocyclic group, C 6-10 Aryl, substituted C 6-10 Aryl, C 2-10 Ester group, substituted C 2-10 Ester group, C 1-10 Siloxy, substituted C 1-10 One of a silanyl group, a silyl group or a substituted silyl group.

[0012] In some embodiments, the R1, R2, and R3 are each independently selected from hydrogen, fluorine, C 1-6 Straight chain alkyl, fluorine-substituted C 1-6 Straight chain alkyl, C 3-6 Branched alkyl, fluorine-substituted C 3-6 Branched alkyl, C 1-6 Alkoxy, substituted C 1-6 Alkoxy, C 3-6 Heterocyclic group, substituted C 3-6 Heterocyclic group, C 1-6 Siloxy, substituted C 1-6 A type of silanol group.

[0013] In some embodiments, the R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen, halogen, C substituted by halogen, 1-6 Straight chain alkyl or halogen substituted C 3-6 A type of branched alkyl group.

[0014] In some embodiments, the pyrrolidine nitrate compound is selected from at least one of Compound 1 to Compound 6:

[0015]

[0016] A second aspect of the present application provides an electrolyte comprising the electrolyte additive described in the present application.

[0017] In some embodiments, the concentration of the pyrrolidine nitrate compound in the electrolyte is 0.001 mol / L to 1 mol / L, preferably 0.001 mol / L to 0.5 mol / L.

[0018] In some embodiments, the electrolyte further includes a non-aqueous organic solvent, an electrolyte salt, and auxiliary additives.

[0019] In some embodiments, the non-aqueous organic solvent includes at least one of a cyclic carbonate, a chain carbonate, and a chain carboxylate.

[0020] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium perchlorate, lithium bisoxalatoborate, lithium difluorooxalatoborate, lithium difluorophosphate, and lithium bis(pentafluoroethylsulfonyl)imide.

[0021] In some embodiments, the concentration of the electrolyte salt in the electrolyte solution is 0.05 mol / L to 1.8 mol / L.

[0022] In some embodiments, the auxiliary additive includes at least one of tris(pentafluorophenyl)borane, tris(trimethylsilyl) borate, tris(2,2,2-trifluoroethyl) borate, 2,4,6-trimethoxyboroxane, alkylolamide, polyacrylamide, trimethyl phosphite, vinylene carbonate, vinyl sulfite, propylene sulfite, ethylene sulfite, fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate, tris(2,2,2-trifluoroethyl)phosphite, butanesultone, 12-crown-4-ether, 18-crown-6-ether, methyl difluoroacetate, and ethyl difluoroacetate.

[0023] In some embodiments, the mass fraction of the auxiliary additive in the electrolyte is 0.02% to 8%.

[0024] A third aspect of the present application provides an electrochemical device comprising the electrolyte described in the present application.

[0025] In some embodiments, the electrochemical device further includes a positive electrode, the positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate, lithium cobaltate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich layered oxide, lithium nickel manganese oxide, lithium titanate, graphite fluoride, MnO2, FeS2, and FeF3.

[0026] In some embodiments, the electrochemical device further comprises a negative electrode, the negative electrode comprising a negative electrode active material, the negative electrode active material comprising at least one of lithium titanate, high-phase pyrolytic graphite, artificial graphite, natural graphite, graphitized mesophase carbon microbeads, silicon monoxide, silicon-carbon composite negative electrode, metal lithium negative electrode material, and composite metal lithium negative electrode material.

[0027] A fourth aspect of the present application provides a vehicle comprising the electrochemical device described in the present application.

[0028] The electrolyte additive of the present application can at least bring the following beneficial effects:

[0029] The electrolyte additive contains a pyrrolidine nitrate compound with a structure shown in Formula I, wherein the nitrate ion is a Lewis base, and its electron donating ability is greater than that of the hexafluorophosphate in lithium hexafluorophosphate (the DN value of the nitrate anion is approximately twice that of the hexafluorophosphate), and it is easier to enter the solvation shell of the lithium ion and the Helmholtz layer in the interface. Therefore, the nitrate anion can form a smooth and thin SEI rich in inorganic substances (such as Li2O, Li3N and LiF) on the surface of the negative electrode, thereby improving the stability of the negative electrode interface and reducing the interface impedance. On the other hand, it can enter the solvation structure of the lithium ions in the electrolyte, weakening the interaction between the lithium ions and the solvent. Reduce the desolvation energy of lithium ions; at the same time, the HOMO energy level between nitrate ions and substituted or unsubstituted pyrrolidinyl cations is very low, has excellent oxidation resistance, and is compatible with high-voltage positive electrodes. Nitrate ions and substituted or unsubstituted pyrrolidinyl cations can be adsorbed on the surface of the aluminum current collector, inhibiting the corrosion of LiFSI on the aluminum current collector, so that LiFSI can replace LiPF6 in a large proportion, improve the ionic conductivity of the electrolyte liquid phase, and further improve the stability of the electrolyte liquid phase and the electrolyte / negative electrode interface, thereby improving the overall life and fast charging performance of the lithium-ion battery.

[0030] In addition, the substituted or unsubstituted pyrrolidine cations and nitrate anions contained in the structure shown in Formula I each carry only one charge and are relatively large in size, so the attraction between them is relatively small, which makes the pyrrolidine nitrate compound highly soluble in the electrolyte and can introduce more cationic and anionic groups into the electrolyte and exert their effects.

[0031] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below. The embodiments are exemplary and intended to be used to explain the present application, but should not be understood as limiting the present application.

[0033] Throughout this application, the disclosure of numerical ranges includes disclosure of all values ​​within the entire range and further subdivided ranges, including the endpoints and subranges given within those ranges.

[0034] In this application, the raw materials, equipment, etc. involved, unless otherwise specified, are all raw materials and equipment that can be obtained through commercial channels or known methods; the methods involved, unless otherwise specified, are all conventional methods.

[0035] definition:

[0036] The term "halogen" refers to F, Cl, Br or I.

[0037] The term "alkyl" refers to a hydrocarbon group formed by removing a hydrogen atom from an alkane molecule.

[0038] The term "nitro" refers to the group remaining after removing a hydroxyl group from the nitric acid molecule, with the chemical formula -NO2.

[0039] The term "cyano" refers to a group consisting of a carbon atom and a nitrogen atom connected by a triple bond, with the chemical formula -CN.

[0040] The term "sulfonic acid" refers to a -SO3H group.

[0041] The term "straight-chain alkyl" refers to an alkyl radical containing one or more carbon atoms in an unbranched linear sequence, for example, ethyl, n-propyl, n-butyl, etc.

[0042] The term "branched alkyl" refers to a monovalent hydrocarbon group having a branched arrangement of carbon atoms, for example, isobutyl, tert-butyl, etc.

[0043] The term "chain alkyl" refers to a type of straight-chain or branched alkyl group containing carbon and hydrogen atoms, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, 2-ethylbutyl, 2-ethylhexyl or 2-butyloctyl.

[0044] The term "substituted" refers to a structure where a hydrogen is replaced by a substituent. A "substituent" is an atom or group that replaces a hydrogen atom when a hydrocarbon is "substituted."

[0045] The term "alkoxy" refers to a group consisting of an alkyl group and an oxygen atom, which may be a straight-chain or branched alkyl group bonded through the oxygen atom, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, pentoxy, etc.

[0046] The term "heterocyclyl" refers to a monoradical or diradical saturated or unsaturated group having a single ring or multiple fused rings, having one or more heteroatoms selected from nitrogen, sulfur, phosphorus and / or oxygen in the ring. The heteroatoms in the "heterocyclyl" can be oxidized, for example -N(O)-, -S(O)-, -S(O)2-. The heterocyclyl can be a single ring or multiple rings, wherein the multiple rings can be fused, bridged or spiro.

[0047] The term "aryl" refers to a monovalent group that is aromatic and optionally carbocyclic. An aryl group has at least one aromatic ring. Any additional rings may be unsaturated, partially saturated, saturated, or aromatic. Examples include phenyl, naphthyl, and anthracenyl.

[0048] The term "ester group" refers to the ester functional group in carboxylic acid derivatives, and its structural formula is -COOR (R is generally an alkyl group or other non-H group).

[0049] The term "silyl" refers to a -Si(Rs)3 substituent or a Si(Rs)2 substituent, wherein each Rs may be the same or different. Si(Rs)2 may also be a divalent bridge. Each Rs may be hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aralkyl, alkoxy, aryloxy, amino, silanyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, and combinations thereof.

[0050] The term "siloxy" means a silyl group, as defined herein, appended to the parent molecule through an oxygen atom.

[0051] The prefix "C u-v " indicates that the following group has from u to v carbon atoms. For example, "C 1-10 "Straight-chain alkyl" means a straight-chain alkyl group having 1 to 10 carbon atoms.

[0052] The electrolyte additive of the embodiment of the present application includes a pyrrolidine nitrate compound, and the pyrrolidine nitrate compound has a structure shown in Formula I:

[0053]

[0054] Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from one of hydrogen, halogen, linear alkyl, substituted linear alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, heterocyclic group, substituted heterocyclic group, aryl, substituted aryl, ester group, substituted ester group, silanyloxy, substituted silanyloxy, silanyl, and substituted silanyl.

[0055] In some embodiments, the substituents in the substituted straight-chain alkyl group, substituted branched alkyl group, substituted alkoxy group, substituted heterocyclic group, substituted aryl group, substituted ester group, substituted siloxy group and substituted silyl group include but are not limited to one of alkyl group, halogen group, nitro group, cyano group, sulfonic acid group and the like.

[0056] As a non-limiting example, the alkyl group in the substituent group is C 1-10 Straight chain alkyl or C 3-10 branched-chain alkyl groups, such as methyl, ethyl, n-propyl, n-butyl, isopropyl, 2-methylpropyl, 2-chloropropyl, and the like.

[0057] In some embodiments, R1, R2, R3, R4, R5, and R6 are each independently selected from hydrogen, halogen, C 1-10 Straight chain alkyl, substituted C 1-10 Straight chain alkyl, C 3-10 Branched alkyl, substituted C 3-10 Branched alkyl, C 1-10 Alkoxy, substituted C 1-10 Alkoxy, C 3-6 Heterocyclic group, substituted C 3-6 Heterocyclic group, C 6-10 Aryl, substituted C 6-10 Aryl, C 2-10 Ester group, substituted C 2-10 Ester group, C 1-10 Siloxy, substituted C 1-10 One of a silanyl group, a silyl group or a substituted silyl group.

[0058] As a non-limiting example, C 1-10 Straight chain alkyl, substituted C 1-10 Straight chain alkyl, C 3-10 Branched alkyl, substituted C 3-10 Branched alkyl, C 1-10Alkoxy, substituted C 1-10 Alkoxy, C 1-10 Siloxy, substituted C 1-10 The number of carbon atoms in the siloxy group may be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0059] Where: C 1-10 Straight chain alkyl and substituted C 1-10 Straight chain alkyl groups include but are not limited to methyl, ethyl, n-propyl, n-butyl, etc. 3-10 Branched alkyl and substituted C 3-10 Branched alkyl groups include but are not limited to isopropyl, 2-methylpropyl, 2-chloropropyl, etc. 1-10 Alkoxy and substituted C 1-10 Alkoxy includes but is not limited to methoxy, ethoxy, 1-methylethoxy, etc.; C 1-10 Siloxy and substituted C 1-10 The silyloxy groups include, but are not limited to, silyloxy, tris(chloromethyl)silyloxy, disilyloxy, and the like.

[0060] As a non-limiting example, C 3-6 Heterocyclic group, substituted C 3-6 The number of carbon atoms in the heterocyclic group can be 3, 4, 5 or 6.

[0061] Where: C 3-6 Heterocyclic and substituted C 3-6 Heterocyclic groups include, but are not limited to, imidazolyl, pyrrolyl, 2-methylpyrrolyl, 5-nitrothienyl, and the like.

[0062] As a non-limiting example, C 6-10 Aryl, substituted C 6-10 The number of carbon atoms in the aryl group can be 6, 7, 8, 9 or 10.

[0063] Among them, C 6-10 Aryl and substituted C 6-10 Aryl groups include, but are not limited to, phenyl, naphthyl, 2-bromophenyl, 4-nitrophenyl, 4-methylphenyl, and the like.

[0064] As a non-limiting example, C 2-10 Ester group, substituted C 2-10 The number of carbon atoms in the ester group can be 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0065] In some embodiments, R1, R2, and R3 are each independently selected from hydrogen, fluorine, C 1-6 Straight chain alkyl, fluorine-substituted C 1-6 Straight chain alkyl, C3-6 Branched alkyl, fluorine-substituted C 3-6 Branched alkyl, C 1-6 Alkoxy, substituted C 1-6 Alkoxy, C 3-6 Heterocyclic group, substituted C 3-6 Heterocyclic group, C 1-6 Siloxy, substituted C 1-6 A type of silanol group.

[0066] In some embodiments, R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen, halogen, C 1-6 Straight chain alkyl or halogen substituted C 3-6 A type of branched alkyl group.

[0067] Furthermore, R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen, fluorine, C 1-6 Straight chain alkyl or fluorine-substituted C 3-6 A type of branched alkyl group.

[0068] In some embodiments, the pyrrolidine nitrate compound is selected from at least one of Compound 1 to Compound 6:

[0069]

[0070] The electrolyte additives of the embodiments of the present application can at least bring the following beneficial effects:

[0071] 1. The pyrrolidine nitrate compound having the structure shown in Formula I contains substituted or unsubstituted pyrrolidine cations and nitrate anions, each of which has only one charge and is large in size. Therefore, the mutual attraction between them is small, which makes the pyrrolidine nitrate compound highly soluble in the electrolyte and can introduce more cationic and anionic groups into the electrolyte to exert its effect.

[0072] 2. The pyrrolidine nitrate compound having the structure shown in Formula I, whose nitrate anion is a Lewis base, has an electron-donating ability greater than that of hexafluorophosphate in lithium hexafluorophosphate (the DN value of the nitrate anion is approximately twice that of the hexafluorophosphate), and is more likely to enter the solvation shell of lithium ions and the Helmholtz layer within the interface. Therefore, the nitrate anion can form a smooth and thin SEI rich in inorganic substances (such as Li2O, Li3N and LiF) on the surface of the negative electrode, thereby improving the stability of the negative electrode interface and reducing the interfacial impedance. At the same time, it can also enter the solvation structure of lithium ions in the electrolyte, weakening the interaction between lithium ions and the solvent, reducing the desolvation energy of lithium ions, and thus improving the life and fast charging performance of lithium-ion batteries.

[0073] 3. The pyrrolidine nitrate compound having the structure shown in Formula I, whose substituted or unsubstituted pyrrolidine cations and nitrate anions can be adsorbed on the surface of the aluminum current collector, inhibiting the corrosion of LiFSI on the aluminum current collector, so that LiFSI can replace LiPF6 in a large proportion, improving the ionic conductivity of the electrolyte liquid phase, and further improving the stability of the electrolyte liquid phase and the electrolyte / negative electrode interface, thereby improving the battery life and fast charging performance.

[0074] 4. Pyrrolidine nitrate compounds having the structure shown in Formula I have a very low HOMO energy level between the substituted or unsubstituted pyrrolidine cation and the nitrate anion, and have excellent oxidation resistance, making them compatible with high-voltage positive electrodes.

[0075] In the embodiments of the present application, the electrolyte additive can be prepared by different methods. The specific preparation method is not limited and can be rationally and comprehensively designed based on the conventional preparation process of pyrrolidine nitrate derivatives and the properties of the substituent groups.

[0076] In some embodiments, taking the case where the electrolyte additive is the above-mentioned compound 1 as an example, it can be prepared in the following manner:

[0077] Dissolve 10 g of the reaction substrate, N-propyl-N-methylpyrrolidine nitrate, in 50 ml of dichloromethane. Slowly add 2 g of the fluorination reagent, tetraethylammonium tetrafluoroborate. Continue the reaction for 10 hours to complete the fluorination reaction. Place the reaction vessel in an ice-water bath and slowly cool the reaction solution. Filter to obtain crystals, namely, Compound 1.

[0078] In other embodiments, taking the case where the electrolyte additive is the above-mentioned compound 2 as an example, it can be prepared in the following manner:

[0079] Dissolve 10 g of the reaction substrate, N-propyl-N-methylpyrrolidine nitrate, in 50 ml of dichloromethane. Slowly add 2 g of the fluorination reagent, N-fluorobenzenesulfonamide, and continue the reaction for 10 hours to complete the fluorination reaction. Place the reaction vessel in an ice-water bath and slowly cool the reaction solution. Filter to obtain crystals, namely, Compound 2.

[0080] In other embodiments, taking the case where the electrolyte additive is the above-mentioned compound 3 as an example, it can be prepared in the following manner:

[0081] Dissolve 10g of the reaction substrate, N-propyl-N-methylpyrrolidine nitrate, in 50ml of dichloromethane. Slowly add 1g of the fluorination reagent, sulfur tetrafluoride, and continue the reaction for 10 hours to complete the fluorination reaction. Place the reaction vessel in an ice-water bath and slowly cool the reaction solution. Filter to obtain crystals, namely, Compound 3.

[0082] In other embodiments, taking the case where the electrolyte additive is the above-mentioned compound 4 as an example, it can be prepared in the following manner:

[0083] Dissolve 10 g of the reaction substrate, 1-allyl-1-methylpyrrolidine nitrate, in 50 ml of dichloromethane. Slowly add 5 ml of a 70% aqueous hydrofluoric acid solution. Continue the reaction for 6 hours to complete the fluorination reaction. Place the reaction vessel in an ice-water bath to slowly cool the reaction solution, and filter to obtain crystals, namely, Compound 4.

[0084] In other embodiments, taking the case where the electrolyte additive is the above-mentioned compound 5 as an example, it can be prepared in the following manner:

[0085] Dissolve 10g of the reaction substrate, 1-allyl-1-methylpyrrolidine nitrate, in 50ml of dichloromethane. Slowly add 2g of the fluorination reagent, silver fluorosulfonyl difluoroacetate. Continue for 6 hours to complete the fluorination reaction. Place the reaction vessel in an ice-water bath and slowly cool the reaction solution. Filter to obtain crystals, namely, Compound 5.

[0086] In other embodiments, taking the case where the electrolyte additive is the above-mentioned compound 6 as an example, it can be prepared in the following manner:

[0087] Dissolve 10g of the reaction substrate, N-propyl-N-methylpyrrolidine nitrate, in 50ml of dichloromethane. Slowly add 1g of the fluorination reagent, trifluoromethyldiazomethane, and continue the reaction for 10 hours to complete the fluorination reaction. Place the reaction vessel in an ice-water bath and slowly cool the reaction solution. Filter to obtain crystals, namely, Compound 6.

[0088] It should be noted that the above-mentioned pyrrolidine nitrate compounds in the examples of the present application can all be obtained through commercial channels.

[0089] The electrolyte of the embodiment of the present application includes the electrolyte additive of the embodiment of the present application.

[0090] In some embodiments, the concentration of the pyrrolidine nitrate compound in the electrolyte is 0.001 mol / L to 1 mol / L.

[0091] As a non-limiting example, the concentration of the pyrrolidine nitrate compound in the electrolyte of the embodiment of the present application includes but is not limited to 0.001mol / L, 0.01mol / L, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, 0.6mol / L, 0.6mol / L, 0.8mol / L, 0.9mol / L or 1mol / L, etc. In the electrolyte of the embodiment of the present application, the concentration of the pyrrolidine nitrate compound is within the above range, which can improve the interface stability of the negative electrode, reduce the interface impedance, inhibit the corrosion of the aluminum current collector, and reduce the desolvation energy of lithium ions, thereby improving the life and fast charging performance of the lithium-ion battery as a whole; if it is lower than 0.001mol / L, the improvement effect on the interface stability and interface impedance is limited, and the improvement of the battery performance is not obvious; if it is higher than 1mol / L, it will significantly increase the viscosity of the electrolyte and deteriorate the fast charging performance of the lithium-ion battery.

[0092] As a preferred embodiment, the concentration of the pyrrolidine nitrate compound in the electrolyte of the embodiment of the present application is 0.001-0.5 mol / L.

[0093] In some embodiments, the electrolyte further includes a non-aqueous organic solvent, an electrolyte salt, and auxiliary additives.

[0094] In some embodiments, the non-aqueous organic solvent includes, but is not limited to, at least one of cyclic carbonates, chain carbonates, chain carboxylates, and the like.

[0095] As a non-limiting example, the cyclic carbonate includes, but is not limited to, at least one of ethylene carbonate, propylene carbonate, 1,4-butyrolactone, and the like.

[0096] As a non-limiting example, the linear carboxylic acid esters include, but are not limited to, at least one of methyl formate, ethyl formate, propyl formate, isopropyl formate, butyl formate, isobutyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, isopropyl acetate, allyl acetate, butyl acetate, isobutyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl butyrate, ethyl butyrate, propyl butyrate, isopropyl butyrate, and fluorine analogs thereof.

[0097] As a non-limiting example, the chain carbonate includes but is not limited to at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylpropyl carbonate, and the like.

[0098] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of a lithium salt and the like.

[0099] As a non-limiting example, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, and lithium bis(pentafluoroethylsulfonyl)imide.

[0100] In some embodiments, the concentration of the electrolyte salt in the electrolyte solution is 0.05 mol / L to 1.8 mol / L.

[0101] As a non-limiting example, the concentration of the electrolyte salt in the electrolyte solution includes but is not limited to 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.6 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, 1.6 mol / L, 1.7 mol / L or 1.8 mol / L, etc.

[0102] In some embodiments, the auxiliary additive includes at least one of tris(pentafluorophenyl)borane, tris(trimethylsilyl) borate, tris(2,2,2-trifluoroethyl) borate, 2,4,6-trimethoxyboroxane, alkylolamide, polyacrylamide, trimethyl phosphite, vinylene carbonate, vinyl sulfite, propylene sulfite, ethylene sulfite, fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate, tris(2,2,2-trifluoroethyl) phosphite, butane sultone, 12-crown-4-ether, 18-crown-6-ether, methyl difluoroacetate, and ethyl difluoroacetate. Selecting the above substances as auxiliary additives can further improve the positive and negative electrode interface stability and improve the cycle and storage life of lithium-ion batteries.

[0103] In some embodiments, the mass fraction of the auxiliary additive in the electrolyte is 0.02% to 8%. Within this range, the auxiliary additive can further enhance the stability of the positive and negative electrode interfaces and improve the cycle and storage life of the lithium-ion battery. A mass fraction below 0.001 mol / L has little effect on improving cell performance, while a mass fraction above 1 mol / L reduces the storage stability of the electrolyte and increases the production cost of the electrolyte.

[0104] As a non-limiting example, the mass fraction of the auxiliary additive in the electrolyte includes but is not limited to 0.02%, 0.05%, 0.08%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%, etc.

[0105] The preparation method of the electrolyte in the embodiment of the present application is not limited and can be any method for preparing the electrolyte in the art.

[0106] As an optional example, a method for preparing an electrolyte includes the following steps: mixing an electrolyte salt with a non-aqueous organic solvent, then adding a pyrrolidine nitrate compound and an auxiliary additive and mixing again to obtain the electrolyte of an embodiment of the present application.

[0107] It should be noted that the electrolyte salt can be slowly added to the non-aqueous organic solvent, and methods for mixing the electrolyte salt with the non-aqueous organic solvent, adding the pyrrolidine nitrate compound and the auxiliary additives, and mixing again include, but are not limited to, stirring, ultrasonic dispersion, and the like. Furthermore, when the non-aqueous organic solvent includes multiple components as described above, the multiple components of the non-aqueous organic solvent must be mixed before mixing the electrolyte salt with the non-aqueous organic solvent.

[0108] The electrochemical device according to the embodiment of the present application includes the electrolyte according to the embodiment of the present application.

[0109] In some embodiments, the electrochemical device includes but is not limited to secondary batteries such as lithium-ion batteries, capacitors, etc. The secondary battery is not limited to button batteries, soft-pack batteries, square aluminum shell batteries, or cylindrical batteries.

[0110] As a preferred example, the electrochemical device is a lithium-ion battery.

[0111] In some embodiments, the electrochemical device further comprises a positive electrode, the positive electrode comprising a positive electrode active material, the positive electrode active material including but not limited to at least one of lithium iron phosphate, lithium cobaltate, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich layered oxide, lithium nickel manganese oxide, lithium titanate, graphite fluoride, MnO2, FeS2, FeF3, etc.

[0112] In some embodiments, the positive electrode further includes a positive electrode material, and the positive electrode material includes the above-mentioned positive electrode active material, a positive electrode conductor and a positive electrode binder. In the embodiments of the present application, there is no particular restriction on the specific selection of the positive electrode conductor and the positive electrode binder. As a non-limiting example, the positive electrode conductor includes but is not limited to one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotubes; the positive electrode binder includes but is not limited to one or more of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose and polyacrylic acid.

[0113] In some embodiments, the positive electrode further comprises a positive electrode current collector, and a positive electrode material layer is provided on the surface of the positive electrode current collector, and the material of the positive electrode material layer is the above-mentioned positive electrode material. The positive electrode current collector can be selected to comprise aluminum or any other suitable conductive metal foil (such as solid or mesh or covered foil) known to those skilled in the art, a metal grid or screen, or a porous metal. In some variations, the surface of the positive electrode current collector may comprise a metal foil that has been surface treated (e.g., carbon coated and / or etched).

[0114] In some embodiments, the electrochemical device further comprises a negative electrode, which comprises a negative electrode active material, which includes but is not limited to at least one of lithium titanate, high-phase pyrolytic graphite, artificial graphite, natural graphite, graphitized mesophase carbon microbeads, silicon monoxide, silicon-carbon composite negative electrode material, metal lithium negative electrode material, and composite metal lithium negative electrode material.

[0115] As a non-limiting example, the silicon-carbon composite negative electrode material includes but is not limited to at least one of graphite-doped silicon-oxygen material, graphite-doped magnesium-silicon-oxygen material, graphite-doped lithium-silicon-oxygen material, silane-deposited silicon-carbon material, and the like.

[0116] As a non-limiting example, the composite metal lithium negative electrode material includes but is not limited to at least one of a lithium-carbon composite negative electrode material, a lithium-tin composite negative electrode material, a lithium-silver composite negative electrode material, and the like.

[0117] In some embodiments, the electrochemical device further includes a separator disposed between the positive electrode and the negative electrode.

[0118] In some embodiments, the isolation membrane includes but is not limited to polyethylene (PE), polypropylene (PP), polytetrafluoroethylene-based polyolefin (PO) membranes, polyester membranes (such as polyethylene terephthalate (PET) membranes), cellulose membranes, polyimide membranes (PI), polyamide membranes (PA), spandex or aramid membranes, woven membranes, non-woven membranes (non-woven fabrics), microporous membranes, composite membranes, diaphragm paper, rolled membranes or spun membranes, etc.

[0119] It should be noted that in the embodiments of the present application, there is no limitation on the specific technical parameters such as the thickness of the positive electrode, negative electrode, and separator, as long as the purpose of the present application can be achieved.

[0120] The preparation method of the electrochemical device in the embodiment of the present application is not limited and can be any method known to those skilled in the art.

[0121] The vehicle according to the embodiment of the present application includes the electrochemical device according to the embodiment of the present application.

[0122] As a non-limiting example, the above-mentioned vehicles include but are not limited to automobiles, motorcycles, power-assisted bicycles, bicycles, power tools, etc.

[0123] The electrolyte, electrochemical device, vehicle, etc. of the embodiments of the present application all have at least the beneficial effects of the electrolyte of the embodiments of the present application.

[0124] Certain features of the present technology are further illustrated in the following non-limiting examples.

[0125] 1. Examples and Comparative Examples

[0126]

[0127] The soft-pack batteries involved in the following embodiments and comparative examples all include a positive electrode sheet, a negative electrode sheet, and a separator.

[0128] Each positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on opposite sides of the positive electrode current collector. The positive electrode current collector is 20μm thick aluminum foil. The positive electrode material layer is composed of the following components in parts by weight: 90 parts lithium nickel cobalt manganese oxide (positive electrode active material), 5 parts conductive carbon black (SP), and 5 parts polyvinylidene fluoride.

[0129] Each negative electrode sheet includes a negative electrode current collector and negative electrode material layers disposed on opposite sides of the negative electrode current collector. The negative electrode current collector is 12μm thick aluminum foil. The negative electrode material layers are composed of the following components in parts by weight: 92 parts graphite (negative electrode active material), 3 parts conductive carbon black (SP), 2 parts carboxymethyl cellulose (CMC), and 3 parts styrene-butadiene rubber (SBR).

[0130] The separators are all porous polyethylene (PE) films, and the thickness of the separators is 20 μm.

[0131] Example 1

[0132] (Electrolyte)

[0133] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0134] The non-aqueous organic solvent consists of the following components in volume fractions: 25% of ethylene carbonate, 30% of ethyl methyl carbonate and 45% of dimethyl carbonate.

[0135] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.6 mol / L, and the concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0.4 mol / L.

[0136] The electrolyte additive is compound 1, and the concentration of the electrolyte additive in the electrolyte is 0.1 mol / L.

[0137] The auxiliary additive is fluoroethylene carbonate, and the mass of the auxiliary additive accounts for 1.5% of the total mass of the electrolyte.

[0138] (Preparation of Electrolyte)

[0139] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 1 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0140] (Manufacturing of lithium-ion batteries)

[0141] The electrolyte prepared in this embodiment was injected into a soft-pack battery. After standing, forming, and volume separation, a lithium-ion battery of this embodiment was obtained, which was labeled as lithium-ion battery 1.

[0142] Example 2

[0143] (Electrolyte)

[0144] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0145] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate and 70% of dimethyl carbonate.

[0146] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium bis(trifluorosulfonyl)imide, wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.5 mol / L, and the concentration of lithium bis(trifluorosulfonyl)imide in the electrolyte is 0.5 mol / L.

[0147] The electrolyte additive is compound 2, and the concentration of the electrolyte additive in the electrolyte is 0.08 mol / L.

[0148] The auxiliary additive is difluoroethylene carbonate, and the mass of the auxiliary additive accounts for 1.0% of the total mass of the electrolyte.

[0149] (Preparation of Electrolyte)

[0150] In a dry room (dew point below -40°C), ethylene carbonate and dimethyl carbonate were mixed uniformly according to a volume fraction ratio, and then lithium salt was slowly added and fully stirred to form a mixed solution. Then, compound 2 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0151] (Manufacturing of lithium-ion batteries)

[0152] The electrolyte prepared in this embodiment was injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment was obtained, which was marked as lithium-ion battery 2.

[0153] Example 3

[0154] (Electrolyte)

[0155] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0156] The non-aqueous organic solvent consists of the following components in volume fractions: 20% of ethylene carbonate, 40% of ethyl methyl carbonate and 40% of isobutyl acetate.

[0157] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.2 mol / L, and the concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0.8 mol / L.

[0158] The electrolyte additive is compound 3, and the concentration of the electrolyte additive in the electrolyte is 0.12 mol / L.

[0159] The auxiliary additive is lithium difluorophosphate, and the mass of the auxiliary additive accounts for 1.5% of the total mass of the electrolyte.

[0160] (Preparation of Electrolyte)

[0161] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and isobutyl acetate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 3 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0162] (Manufacturing of lithium-ion batteries)

[0163] The electrolyte prepared in this embodiment was injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment was obtained, which was marked as lithium-ion battery 3.

[0164] Example 4

[0165] (Electrolyte)

[0166] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0167] The non-aqueous organic solvent consists of the following components in volume fractions: 20% of ethylene carbonate, 10% of propylene carbonate and 70% of ethyl methyl carbonate.

[0168] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium tetrafluoroborate, wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.8 mol / L, and the concentration of lithium tetrafluoroborate in the electrolyte is 0.2 mol / L.

[0169] The electrolyte additive is compound 4, and the concentration of the electrolyte additive in the electrolyte is 0.2 mol / L.

[0170] The auxiliary additive is butane sultone, and the mass of the auxiliary additive accounts for 1.8% of the total mass of the electrolyte.

[0171] (Preparation of Electrolyte)

[0172] In a dry room (dew point below -40°C), ethylene carbonate, propylene carbonate and ethyl methyl carbonate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 4 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0173] (Manufacturing of lithium-ion batteries)

[0174] The electrolyte prepared in this embodiment is injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment is obtained, which is marked as lithium-ion battery 4.

[0175] Example 5

[0176] (Electrolyte)

[0177] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0178] The non-aqueous organic solvent consists of the following components in volume fractions: 20% of ethylene carbonate, 30% of ethyl methyl carbonate and 50% of ethyl acetate.

[0179] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium difluorooxalatoborate, wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.9 mol / L, and the concentration of lithium difluorooxalatoborate in the electrolyte is 0.1 mol / L.

[0180] The electrolyte additive is compound 5, and the concentration of the electrolyte additive in the electrolyte is 0.5 mol / L.

[0181] The auxiliary additive is fluoroethylene carbonate, and the mass of the auxiliary additive accounts for 2.5% of the total mass of the electrolyte.

[0182] (Preparation of Electrolyte)

[0183] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and ethyl acetate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 5 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0184] (Manufacturing of lithium-ion batteries)

[0185] The electrolyte prepared in this embodiment is injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment is obtained, which is marked as lithium-ion battery 5.

[0186] Example 6

[0187] (Electrolyte)

[0188] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0189] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate, 30% of ethyl methyl carbonate and 40% of methyl propionate.

[0190] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium bis(oxalatoborate), wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.7 mol / L, and the concentration of lithium bis(oxalatoborate) in the electrolyte is 0.3 mol / L.

[0191] The electrolyte additive is compound 5, and the concentration of the electrolyte additive in the electrolyte is 0.32 mol / L.

[0192] The auxiliary additive is vinylene carbonate, and the mass of the auxiliary additive accounts for 2.0% of the total mass of the electrolyte.

[0193] (Preparation of Electrolyte)

[0194] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and methyl propionate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 6 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0195] (Manufacturing of lithium-ion batteries)

[0196] The electrolyte prepared in this embodiment is injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment is obtained, which is marked as lithium-ion battery 6.

[0197] Example 7

[0198] (Electrolyte)

[0199] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0200] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate, 30% of ethyl methyl carbonate and 40% of methyl propionate.

[0201] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium bis(oxalatoborate), wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.7 mol / L, and the concentration of lithium bis(oxalatoborate) in the electrolyte is 0.3 mol / L.

[0202] The electrolyte additive is compound 1, and the concentration of the electrolyte additive in the electrolyte is 0.001 mol / L.

[0203] The auxiliary additive is fluoroethylene carbonate, and the mass of the auxiliary additive accounts for 2.0% of the total mass of the electrolyte.

[0204] (Preparation of Electrolyte)

[0205] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and methyl propionate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 1 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0206] (Manufacturing of lithium-ion batteries)

[0207] The electrolyte prepared in this embodiment is injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment is obtained, which is marked as lithium-ion battery 7.

[0208] Example 8

[0209] (Electrolyte)

[0210] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0211] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate, 30% of ethyl methyl carbonate and 40% of methyl propionate.

[0212] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium bis(oxalatoborate), wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.7 mol / L, and the concentration of lithium bis(oxalatoborate) in the electrolyte is 0.3 mol / L.

[0213] The electrolyte additive is compound 1, and the concentration of the electrolyte additive in the electrolyte is 1 mol / L.

[0214] The auxiliary additive is fluoroethylene carbonate, and the mass of the auxiliary additive accounts for 2.0% of the total mass of the electrolyte.

[0215] (Preparation of Electrolyte)

[0216] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and methyl propionate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 1 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0217] (Manufacturing of lithium-ion batteries)

[0218] The electrolyte prepared in this embodiment is injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment is obtained, which is marked as lithium-ion battery 8.

[0219] Example 9

[0220] (Electrolyte)

[0221] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0222] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate, 30% of ethyl methyl carbonate and 40% of methyl propionate.

[0223] The lithium salt is lithium hexafluorophosphate, and the concentration of lithium hexafluorophosphate in the electrolyte is 0.05 mol / L.

[0224] The electrolyte additive is compound 2, and the concentration of the electrolyte additive in the electrolyte is 0.2 mol / L.

[0225] The auxiliary additive is vinylene carbonate, and the mass of the auxiliary additive accounts for 2.0% of the total mass of the electrolyte.

[0226] (Preparation of Electrolyte)

[0227] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and methyl propionate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 2 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0228] (Manufacturing of lithium-ion batteries)

[0229] The electrolyte prepared in this embodiment is injected into the soft-pack battery. After standing, forming, and volume separation, the lithium-ion battery of this embodiment is obtained, which is marked as lithium-ion battery 9.

[0230] Example 10

[0231] (Electrolyte)

[0232] The electrolyte of this embodiment includes a non-aqueous organic solvent, a lithium salt, an electrolyte additive, and an auxiliary additive.

[0233] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate, 30% of ethyl methyl carbonate and 40% of methyl propionate.

[0234] The lithium salt is lithium hexafluorophosphate, and the concentration of lithium hexafluorophosphate in the electrolyte is 1.8 mol / L.

[0235] The electrolyte additive is compound 2, and the concentration of the electrolyte additive in the electrolyte is 0.2 mol / L.

[0236] The auxiliary additive is vinylene carbonate, and the mass of the auxiliary additive accounts for 2.0% of the total mass of the electrolyte.

[0237] (Preparation of Electrolyte)

[0238] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and methyl propionate were mixed uniformly according to the volume fraction ratio, and then lithium salt was slowly added and stirred thoroughly to form a mixed solution. Then, compound 2 and auxiliary additives were added to the mixed solution and stirred again to obtain the electrolyte of this embodiment.

[0239] (Manufacturing of lithium-ion batteries)

[0240] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, forming, and volume separation processes, a lithium-ion battery of this embodiment is obtained, which is labeled as lithium-ion battery 10.

[0241] Example 11

[0242] This embodiment is basically the same as embodiment 1, except that:

[0243] The electrolyte and the preparation method of the electrolyte do not contain auxiliary additive fluoroethylene carbonate.

[0244] In the preparation of the lithium-ion battery, the electrolyte used was the electrolyte of this comparative example, and the obtained lithium-ion battery was marked as D3.

[0245] Comparative Example 1

[0246] (Electrolyte)

[0247] The electrolyte of this comparative example includes a non-aqueous organic solvent and a lithium salt.

[0248] The non-aqueous organic solvent consists of the following components in volume fractions: 30% of ethylene carbonate, 30% of dimethyl carbonate and 30% of diethyl carbonate.

[0249] The lithium salt is lithium hexafluorophosphate, and the concentration of the lithium salt in the electrolyte is 1 mol / L.

[0250] (Preparation of Electrolyte)

[0251] In a dry room (dew point below -40°C), ethylene carbonate, dimethyl carbonate and diethyl carbonate were uniformly mixed according to a volume fraction ratio, and then lithium salt was slowly added and fully stirred to form a mixed solution, thereby obtaining the electrolyte of this comparative example.

[0252] (Manufacturing of lithium-ion batteries)

[0253] The electrolyte prepared in this comparative example was injected into a soft-pack battery. After standing, forming, and volume separation, a lithium-ion battery of this comparative example was obtained, which was labeled as lithium-ion battery D1.

[0254] Comparative Example 2

[0255] This comparative example is basically the same as Example 1, except that:

[0256] The electrolyte and the preparation method of the electrolyte do not contain the additive compound 1.

[0257] In the preparation of the lithium-ion battery, the electrolyte used was the electrolyte of this comparative example, and the obtained lithium-ion battery was marked as D2.

[0258] 2. Performance Testing

[0259] DCR test: After formation and capacity adjustment, the batteries obtained in each example and comparative example were discharged at a constant current of 1 / 3C to 2.5V at 25°C. They were then charged at a constant current of 1 / 3C for 1.5 hours. After standing for 3 hours, the open-circuit voltage (V1) was recorded. Subsequently, the batteries were charged at a constant current of 3C (I0) for 10 seconds, and the open-circuit voltage (V2) was recorded. The DCR for a 50% SOC (10 seconds charge) was calculated as: (V2 - V1) / I0.

[0260] Charging performance test: After formation and capacity separation, the batteries obtained in each embodiment and comparative example were discharged at a constant current of 1 / 3C to 2.5V at 25°C, and then charged at a constant current of 3C to a voltage of 4.25V, and the charging capacity was recorded.

[0261] Room-Temperature Cycling Performance Test: After formation and capacity quantification, the batteries obtained in each Example and Comparative Example were charged at 1C constant current to a voltage of 4.25V at 25°C, then discharged at a constant voltage to a current of 0.05C. After 10 minutes of rest, they were discharged at 1C constant current to 2.5V. This constituted one charge-discharge cycle. The resulting batteries were subjected to 1000 charge-discharge cycles at 25°C.

[0262] High-temperature cycling performance test: After formation and capacity quantification, the batteries obtained in each example and comparative example were charged at 45°C at a constant current of 1C to a voltage of 4.25V, then discharged at a constant voltage to a current of 0.05C. After 10 minutes of rest, they were discharged at a constant current of 1C to 2.5V. This constituted one charge-discharge cycle. The resulting batteries were subjected to 500 charge-discharge cycles at 45°C.

[0263] The performance test results of the batteries of various embodiments and comparative examples are shown in Table 1.

[0264] Table 1 Performance test results of batteries in various embodiments and comparative examples

[0265]

[0266]

[0267] Note: In Table 1, the charge DCR decrease ratio is a positive number, such as 25% in Example 1, which means that the charge DCR decreases by 25%. The charge DCR decrease ratio is a negative number, such as -0.5% in Comparative Example 2, which means that the charge DCR increases by 0.5%.

[0268] As can be seen from Table 1, the internal resistance DCR of the battery with the addition of the pyrrolidine nitrate compound additive of the present application decreases, the charging capacity is improved, and the cycle life is significantly improved (Examples 1-6). It can also be seen that the lower and upper limits of the pyrrolidine nitrate compound additive of the present application and the lower and upper limits of the lithium salt have limited improvement in battery performance (Examples 7-10). Without the addition of the additive compound 1, the battery performance is significantly deteriorated (Example 1 and Comparative Example 2), without the addition of the auxiliary additive of the present application, the battery performance is slightly deteriorated (Example 1 and Example 11), and without the addition of the pyrrolidine nitrate compound additive and the auxiliary additive of the present application, the charging capacity and cycle life are significantly reduced (Comparative Example 1).

[0269] In this application, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0270] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An electrolyte additive, characterized in that The present invention comprises a pyrrolidine nitrate compound, wherein the pyrrolidine nitrate compound has a structure shown in Formula I: wherein R1, R2, R3, R4, R5, and R6 are each independently selected from one of hydrogen, halogen, linear alkyl, substituted linear alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, heterocyclic group, substituted heterocyclic group, aryl, substituted aryl, ester group, substituted ester group, silanyloxy, substituted silanyloxy, silanyl, and substituted silanyl groups; The substituent groups in the substituted straight-chain alkyl group, the substituted branched-chain alkyl group, the substituted alkoxy group, the substituted heterocyclic group, the substituted aryl group, the substituted ester group, the substituted siloxy group and the substituted silyl group all include C 1-10 One of alkyl, halogen, nitro, cyano, and sulfonic acid groups.

2. The electrolyte additive according to claim 1, characterized in that The R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen, halogen, C 1-10 Straight chain alkyl, substituted C 1-10 Straight chain alkyl, C 3-10 Branched alkyl, substituted C 3-10 Branched alkyl, C 1-10 Alkoxy, substituted C 1-10 Alkoxy, C 3-6 Heterocyclic group, substituted C 3-6 Heterocyclic group, C 6-10 Aryl, substituted C 6-10 Aryl, C 2-10 Ester group, substituted C 2-10 Ester group, C 1-10 Siloxy, substituted C 1-10 One of a silanyl group, a silyl group or a substituted silyl group.

3. The electrolyte additive according to claim 1, characterized in that The R1, R2, and R3 are each independently selected from hydrogen, fluorine, C 1-6 Straight chain alkyl, fluorine-substituted C 1-6 Straight chain alkyl, C 3-6 Branched alkyl, fluorine-substituted C 3-6 Branched alkyl, C 1-6 Alkoxy, substituted C 1-6 Alkoxy, C 3-6 Heterocyclic group, substituted C 3-6 Heterocyclic group, C 1-6 Siloxy, substituted C 1-6 A type of silanol group.

4. The electrolyte additive according to claim 1, characterized in that The R1, R2, R3, R4, R5 and R6 are each independently selected from hydrogen, halogen, C 1-6 Straight chain alkyl or halogen substituted C 3-6 A type of branched alkyl group.

5. The electrolyte additive according to any one of claims 1 to 4, characterized in that The pyrrolidine nitrate compound is selected from at least one of Compound 1 to Compound 6:

6. An electrolyte, characterized in that The electrolyte additive comprises the electrolyte additive according to any one of claims 1 to 5.

7. The electrolyte according to claim 6, characterized in that The concentration of the pyrrolidine nitrate compound in the electrolyte is 0.001 mol / L to 1 mol / L; And / or, the electrolyte further includes a non-aqueous organic solvent, an electrolyte salt and auxiliary additives.

8. The electrolyte according to claim 7, characterized in that The non-aqueous organic solvent includes at least one of a cyclic carbonate, a chain carbonate, and a chain carboxylate; and / or the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorophosphate, and lithium bis(pentafluoroethylsulfonyl)imide; and / or, the concentration of the electrolyte salt in the electrolyte solution is 0.05 mol / L to 1.8 mol / L; And / or, the auxiliary additive includes at least one of tris(pentafluorophenyl)borane, tris(trimethylsilyl) borate, tris(2,2,2-trifluoroethyl) borate, 2,4,6-trimethoxyboroxane, alkylolamide, polyacrylamide, trimethyl phosphite, vinylene carbonate, vinyl sulfite, propylene sulfite, ethylene sulfite, fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate, tris(2,2,2-trifluoroethyl)phosphite, butanesultone, 12-crown-4-ether, 18-crown-6-ether, methyl difluoroacetate, and ethyl difluoroacetate; And / or, the mass fraction of the auxiliary additive in the electrolyte is 0.02% to 8%; And / or, the concentration of the pyrrolidine nitrate compound in the electrolyte is 0.001 mol / L to 0.5 mol / L.

9. An electrochemical device, characterized in that Comprising the electrolyte according to any one of claims 6 to 8.

10. The electrochemical device according to claim 9, characterized in that The electrochemical device further includes a positive electrode, the positive electrode including a positive electrode active material, the positive electrode active material including at least one of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium rich layered oxide, lithium nickel manganese oxide, lithium titanate, graphite fluoride, MnO2, FeS2, and FeF3; And / or, the electrochemical device also includes a negative electrode, the negative electrode includes a negative electrode active material, and the negative electrode active material includes at least one of lithium titanate, high-phase pyrolytic graphite, artificial graphite, natural graphite, graphitized mesophase carbon microbeads, silicon monoxide, silicon-carbon composite negative electrode material, metal lithium negative electrode material, and composite metal lithium negative electrode material.

11. A vehicle, characterized in that: Comprising the electrochemical device according to claim 9 or 10.

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