Ester nitrile compound, electrolyte, electrochemical device and vehicle

Abstract

The invention provides an ester nitrile compound, an electrolyte, an electrochemical device and a vehicle, the ester nitrile compound has a structure as shown in formula I: R1 is selected from one of linear alkyl, substituted linear alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, silyl and the like; r2 and R3 are respectively and independently selected from one of hydrogen, halogen, linear alkyl, substituted linear alkyl, branched alkyl, substituted branched alkyl, silyl and the like. The ester nitrile compound provided by the invention can effectively reduce the viscosity of the electrolyte and broaden the low-temperature liquid path of the electrolyte, and meanwhile, cyano groups in the compound can inhibit oxidation of other components of the electrolyte by a positive electrode in a manner of complexing active sites on the surface of the positive electrode, so that the oxidation resistance of the electrolyte is improved, and the dissolution of transition metals in the positive electrode is inhibited; and the electrolyte has relatively good thermal stability in a high-temperature environment.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and in particular to an ester-based nitrile compound, an electrolyte, an electrochemical device, and a vehicle. Background Technology

[0002] Lithium-ion batteries possess advantages such as high operating voltage, high specific energy, long cycle life, low self-discharge rate, and no memory effect. However, in practical applications, their performance is significantly affected by ambient temperature. Currently, the operating temperature range for lithium-ion batteries is -20℃ to 55℃. When the ambient temperature drops further (below -40℃), severe polarization occurs, leading to a significant decrease in discharge capacity, cycle life, and high-power charge / discharge performance. It can even result in severe lithium plating, posing a significant safety hazard. Conversely, at higher ambient temperatures (above 45℃), various internal side reactions are enhanced, drastically reducing the stability of the internal material bulk phase and interfaces, severely impacting all aspects of battery performance, particularly cycle life.

[0003] While existing technologies propose using mixed solvents to improve the conductivity and low-temperature discharge efficiency of lithium-ion batteries, and using high-salt-concentration electrolytes or highly stable electrolyte additives to improve interface stability and cycle efficiency at high temperatures, improvements in low-temperature performance are often accompanied by deterioration in high-temperature performance, and vice versa. It is difficult to improve low-temperature and high-temperature performance simultaneously. This is because low-temperature solvents (such as methyl formate and ethyl acetate) have poor passivation effects on the negative electrode, and side reactions between the negative electrode and the electrolyte are exacerbated in high-temperature environments, leading to deterioration in high-temperature battery performance. High-salt-concentration electrolytes or highly stable electrolyte additives (such as vinylene carbonate) increase electrolyte viscosity or interfacial resistance, reducing lithium-ion migration rates in low-temperature environments, thus deteriorating low-temperature battery performance.

[0004] Therefore, there is an urgent need for a solvent that, when used in electrolytes formulated with high-salt-concentration electrolytes or highly stable electrolyte additives (such as vinylene carbonate), ensures that the lithium-ion battery possesses both excellent low-temperature performance and high-temperature performance. Summary of the Invention

[0005] In view of this, one objective of this application is to provide an ester-based nitrile compound. Because ester-based nitrile compounds have low viscosity, they can effectively reduce the viscosity of the electrolyte and broaden the low-temperature liquid range of the electrolyte, resulting in high ionic conductivity even at low temperatures. Simultaneously, due to its large steric hindrance, this compound exhibits weak interaction with the metal ions corresponding to electrolyte salts such as lithium ions. Lithium ions have low desolvation energy at the electrode / electrolyte interface, thus enabling lithium-ion batteries to exhibit excellent low-temperature performance. Furthermore, the cyano group in this compound can inhibit the oxidation of other electrolyte components by the positive electrode through complexation with the active sites on the positive electrode surface, thereby improving the oxidation resistance of the electrolyte and inhibiting the dissolution of transition metals from the positive electrode. This results in better thermal stability of the electrolyte at high temperatures, further enhancing the high-temperature performance of lithium-ion batteries.

[0006] Another object of this application is to provide an electrolyte.

[0007] Another object of this application is to provide an electrochemical device.

[0008] To achieve the above objectives, the first aspect of this application provides an ester-based nitrile compound having the structure shown in Formula I:

[0009]

[0010] R1 is selected from one of straight-chain alkyl, substituted straight-chain alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, silyl, substituted silyl, heterocyclic alkyl, substituted heterocyclic alkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl; R2 and R3 are each independently selected from one of hydrogen, halogen, straight-chain alkyl, substituted straight-chain alkyl, branched alkyl, substituted branched alkyl, silyl, substituted silyl, heterocyclic alkyl, substituted heterocyclic alkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl.

[0011] In some embodiments, the substituent groups in the substituted straight-chain alkyl, the substituted branched alkyl, the substituted alkoxy, the substituted silyl, the substituted heterocyclic alkyl, the substituted aryl, and the substituted heteroaryl all include one of C1-10 alkyl, halogen, nitro, cyano, and sulfonic acid groups.

[0012] In some embodiments, R1 is selected from one of straight-chain C1-C10 alkyl, substituted straight-chain C1-C10 alkyl, branched C3-C10 alkyl, substituted branched C3-C10 alkyl, C1-C10 alkoxy, substituted C1-C10 alkoxy, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C6-C10 aryl, substituted C6-C10 aryl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0013] In some embodiments, R2 and R3 are each independently selected from hydrogen, halogen, straight-chain C1-C10 alkyl, substituted straight-chain C1-C10 alkyl, branched C3-C10 alkyl, substituted branched C3-C10 alkyl, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C6-C10 aryl, substituted C6-C10 aryl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0014] In some embodiments, R1 is selected from one of straight-chain C7-C10 alkyl, substituted straight-chain C7-C10 alkyl, branched C7-C10 alkyl, substituted branched C7-C10 alkyl, C1-C10 alkoxy, substituted C1-C10 alkoxy, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0015] In some embodiments, R2 and R3 are each independently selected from one of the following: straight-chain C7-C10 alkyl, substituted straight-chain C7-C10 alkyl, branched C7-C10 alkyl, substituted branched C7-C10 alkyl, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0016] In some embodiments, R1 is selected from one of straight-chain C1-C6 alkyl, substituted straight-chain C1-C6 alkyl, branched C3-C6 alkyl, substituted branched C3-C6 alkyl, C1-C6 alkoxy, substituted C1-C6 alkoxy, silyl, substituted silyl, C6-C10 aryl, substituted C6-C10 aryl, C6-C10 heteroaryl, or substituted C2-C10 heteroaryl.

[0017] In some embodiments, R2 and R3 are each independently selected from hydrogen, halogen, straight-chain C1-C6 alkyl, substituted straight-chain C1-C6 alkyl, branched C3-C6 alkyl, substituted branched C3-C6 alkyl, silyl, substituted silyl, C6-C10 aryl, substituted C6-C10 aryl, C6-C10 heteroaryl, or substituted C2-C10 heteroaryl.

[0018] In some embodiments, the ester-based nitrile compound is selected from at least one of compounds 1 to 12;

[0019]

[0020] A second aspect of this application provides an electrolyte comprising a non-aqueous organic solvent and an electrolyte salt, wherein the non-aqueous organic solvent comprises a first solvent comprising the ester-based nitrile compound described in this application.

[0021] In some embodiments, the ester-based nitrile compound has a volume content of 2% to 80% in the non-aqueous organic solvent.

[0022] In some embodiments, the electrolyte further includes additives, including at least one of tris(pentafluorophenyl)borane, tris(trimethylsilyl) borate, tris(2,2,2-trifluoroethyl) borate, 2,4,6-trimethoxyboronoxane, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, trimethylsilanol, alkylolamide, polyacrylamide, trimethyl phosphite, vinylene carbonate, vinyl sulfite, propylene sulfite, butene sulfite, ethylene sulfite, 4-methyl ethylene sulfite, fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate, lithium nitrate, dichloromethane, tris(2,2,2-trifluoroethyl) phosphite, 3,5-bis(trifluoromethyl)phenylboronic acid, butyrate lactone, acrylonitrile, 12-crown-4-ether, 18-crown-6-ether, methyl difluoroacetate, ethyl difluoroacetate, lithium nitrate, lithium carbonate, and carbon dioxide.

[0023] In some embodiments, the additive is present in the electrolyte at a mass content of 0.02% to 8%.

[0024] In some embodiments, the non-aqueous organic solvent further includes a second solvent, the second solvent including at least one of cyclic carbonates, chain carbonates, and chain carboxylic esters.

[0025] In some embodiments, the cyclic carbonate has a volume content of 5% to 50% in the non-aqueous organic solvent.

[0026] In some embodiments, the chain carbonate has a volume content of 10% to 70% in the non-aqueous organic solvent.

[0027] In some embodiments, the chain carboxylic acid ester has a volume content of 0.01% to 70% in the non-aqueous organic solvent.

[0028] In some embodiments, the electrolyte salt includes at least one of lithium salt, sodium salt, and potassium salt.

[0029] In some embodiments, the concentration of the electrolyte salt in the electrolyte is from 0.05 mol / L to 1.8 mol / L.

[0030] A third aspect of this application provides an electrochemical device comprising the electrolyte described in this application.

[0031] A fourth aspect of this application proposes a vehicle that includes the electrochemical device described in this application.

[0032] The ester-based nitrile compounds described in this application can bring at least the following beneficial effects:

[0033] Because ester-based nitrile compounds have low viscosity, they can effectively reduce the viscosity of the electrolyte and widen the low-temperature liquid range of the electrolyte, resulting in high ionic conductivity even at low temperatures. Simultaneously, due to their large steric hindrance, these compounds exhibit weak interactions with the metal ions corresponding to electrolyte salts such as lithium ions. This results in low desolvation energy for lithium ions at the electrode / electrolyte interface, leading to excellent low-temperature performance in lithium-ion batteries. Furthermore, the cyano group in these compounds can inhibit the oxidation of other electrolyte components by the positive electrode through complexation of the positive electrode surface active sites, thereby improving the electrolyte's oxidation resistance and inhibiting the dissolution of transition metals from the positive electrode. This provides good thermal stability at high temperatures, further enhancing the high-temperature performance of lithium-ion batteries.

[0034] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0035] The embodiments of this application are described in detail below. These embodiments are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0036] In this application, the disclosure of numerical ranges includes all values ​​throughout the range and the disclosure of further subdivisions of the range, including the endpoints and subranges given for these ranges.

[0037] Unless otherwise specified, all raw materials and equipment involved in this application are self-made through commercial means or known methods; and all methods involved are conventional methods unless otherwise specified.

[0038] definition:

[0039] The term "halogen" refers to F, Cl, Br, or I.

[0040] The term "nitro" refers to the group remaining after removing a hydroxyl group from a nitric acid molecule; its chemical formula is -NO2.

[0041] The term "cyano" refers to a group in which carbon and nitrogen atoms are linked by a triple bond, with the chemical formula -CN.

[0042] The term "sulfonic acid group" refers to the -SO3H group.

[0043] The term "alkyl" refers to a hydrocarbon group formed by removing one hydrogen atom from an alkane molecule.

[0044] The term "linear alkyl" refers to an alkyl radical containing one or more carbon atoms in an unbranched linear sequence. Examples include ethyl, n-propyl, and n-butyl.

[0045] The term "branched alkyl" refers to a monovalent hydrocarbon group whose constituent carbon atoms have a branched structure. Examples include isobutyl and tert-butyl.

[0046] The term "substituted" refers to the fact that hydrogen atoms in the structure are replaced by substituents. A "substituent" is an atom or group that replaces a hydrogen atom when a hydrocarbon is "substituted".

[0047] The term "alkoxy" refers to a group consisting of an alkyl group and an oxygen atom. It can be a straight-chain or branched alkyl group bonded by an oxygen atom, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, pentoxy, etc.

[0048] The term "heterocyclic alkyl" refers to a ring containing at least one heteroatom selected from N, S, and O, such as pyrrolidinyl, tetrahydrofuranyl, dihydrofuranyl, tetrahydropyranyl, pyranyl, thiaranyl, aziridinyl, ethylene oxide, dioxanepentyl, chromenyl, isothiazolyl, piperazine, etc.

[0049] The term "aryl" refers to a monovalent group that is aromatic and optionally has a carbocyclic ring. An aryl group has at least one aromatic ring. Any additional rings can be unsaturated, partially saturated, saturated, or aromatic. Examples include phenyl, naphthyl, etc.

[0050] The term "heteroaryl" refers to a 2 to 15-membered unsaturated heteromonocyclic or fused monocyclic, bicyclic or tricyclic system, wherein at least one fused ring is aromatic and contains at least one atom selected from N, O and S.

[0051] The term "ester group" refers to the functional group of an ester in a carboxylic acid derivative, with the structural formula -COOR (R is generally an alkyl group or other non-H group).

[0052] The term "silyl" refers to a -Si(Rs)3 substituent or a Si(Rs)2 substituent, where 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, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, and combinations thereof.

[0053] The prefix "Cm-Cn" indicates that the following group has from m to n carbon atoms. For example, "C1-C10 straight-chain alkyl" means that the straight-chain alkyl has 1 to 10 carbon atoms.

[0054] <Ester-based nitrile compounds>

[0055] The ester-based nitrile compounds of this application have the structure shown in Formula I:

[0056]

[0057] R1 is selected from one of straight-chain alkyl, substituted straight-chain alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, silyl, substituted silyl, heterocyclic alkyl, substituted heterocyclic alkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl; R2 and R3 are each independently selected from one of hydrogen, halogen, straight-chain alkyl, substituted straight-chain alkyl, branched alkyl, substituted branched alkyl, silyl, substituted silyl, heterocyclic alkyl, substituted heterocyclic alkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl.

[0058] In some embodiments, the substituent groups in the substituted straight-chain alkyl, substituted branched-chain alkyl, substituted alkoxy, substituted silyl, substituted heterocyclic alkyl, substituted aryl, and substituted heteroaryl groups all include one of C1-10 alkyl, halogen, nitro, cyano, and sulfonic acid groups.

[0059] By way of non-limiting example, the alkyl group in the substituent is a straight-chain alkyl group of C1-C10 or a branched alkyl group of C3-C10, such as methyl, ethyl, n-propyl, n-butyl, isopropyl, 2-methylpropyl, 2-chloropropyl, etc.

[0060] In some embodiments, R1 is selected from one of the following: straight-chain C1-C10 alkyl, substituted straight-chain C1-C10 alkyl, branched C3-C10 alkyl, substituted branched C3-C10 alkyl, C1-C10 alkoxy, substituted C1-C10 alkoxy, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C6-C10 aryl, substituted C6-C10 aryl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0061] In some embodiments, R2 and R3 are each independently selected from hydrogen, halogen, straight-chain C1-C10 alkyl, substituted straight-chain C1-C10 alkyl, branched C3-C10 alkyl, substituted branched C3-C10 alkyl, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C6-C10 aryl, substituted C6-C10 aryl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0062] By way of non-limiting example, the number of carbon atoms in straight-chain C1-C10 alkyl groups and substituted straight-chain C1-C10 alkyl groups can be 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0063] Among them, C1-C10 straight-chain alkyl and substituted C1-C10 straight-chain alkyl include, but are not limited to, methyl, ethyl, n-propyl, n-butyl, etc.

[0064] By way of non-limiting example, the number of carbon atoms in branched C3-C10 alkyl groups and substituted branched C3-C10 alkyl groups can be 3, 4, 5, 6, 7, 8, 9, or 10. For example, isopropyl, 2-methylpropyl, 2-chloropropyl, etc.

[0065] By way of non-limiting example, the number of carbon atoms in C3-C6 heterocyclic alkyl groups and substituted C3-C6 heterocyclic alkyl groups can be 3, 4, 5 or 6. Examples include pyrrolidinyl, tetrahydrofuranyl, dihydrofuranyl, etc.

[0066] By way of non-limiting example, the number of carbon atoms in C6-C10 aryl and substituted C6-C10 aryl can be 6, 7, 8, 9 or 10.

[0067] Among them, C6-C10 aryl and substituted C6-C10 aryl include, but are not limited to, phenyl, naphthyl, 2-bromophenyl, 4-nitrophenyl, 4-methylphenyl, etc.

[0068] By way of a non-limiting example, the number of carbon atoms in C2-C10 heteroaryl groups and substituted C2-C10 heteroaryl groups can be 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0069] Among them, C2-C10 heteroaryl and substituted C2-C10 heteroaryl include, but are not limited to, 3-methylpyridinyl, 3-cyanothiophene, etc.

[0070] In some embodiments, R1 is selected from one of straight-chain C7-C10 alkyl, substituted straight-chain C7-C10 alkyl, branched C7-C10 alkyl, substituted branched C7-C10 alkyl, C1-C10 alkoxy, substituted C1-C10 alkoxy, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0071] In some embodiments, R2 and R3 are each independently selected from one of the following: straight-chain C7-C10 alkyl, substituted straight-chain C7-C10 alkyl, branched C7-C10 alkyl, substituted branched C7-C10 alkyl, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

[0072] In other embodiments, R1 is selected from one of straight-chain C1-C6 alkyl, substituted straight-chain C1-C6 alkyl, branched C3-C6 alkyl, substituted branched C3-C6 alkyl, C1-C6 alkoxy, substituted C1-C6 alkoxy, silyl, substituted silyl, C6-C10 aryl, substituted C6-C10 aryl, C6-C10 heteroaryl, or substituted C2-C10 heteroaryl.

[0073] In other embodiments, R2 and R3 are each independently selected from hydrogen, halogen, straight-chain C1-C6 alkyl, substituted straight-chain C1-C6 alkyl, branched C3-C6 alkyl, substituted branched C3-C6 alkyl, silyl, substituted silyl, C6-C10 aryl, substituted C6-C10 aryl, C6-C10 heteroaryl, or substituted C2-C10 heteroaryl.

[0074] In some embodiments, the ester-based nitrile compound is selected from at least one of compounds 1 to 12;

[0075]

[0076] The ester-based nitrile compounds of this application can bring at least the following beneficial effects:

[0077] Because ester-based nitrile compounds have low viscosity, they can effectively reduce the viscosity of the electrolyte and widen the low-temperature liquid range of the electrolyte, resulting in high ionic conductivity even at low temperatures. Simultaneously, due to their large steric hindrance, these compounds exhibit weak interactions with the metal ions corresponding to electrolyte salts such as lithium ions. This results in low desolvation energy for lithium ions at the electrode / electrolyte interface, leading to excellent low-temperature performance in lithium-ion batteries. Furthermore, the cyano group in these compounds can inhibit the oxidation of other electrolyte components by the positive electrode through complexation of the positive electrode surface active sites, thereby improving the electrolyte's oxidation resistance and inhibiting the dissolution of transition metals from the positive electrode. This provides good thermal stability at high temperatures, further enhancing the high-temperature performance of lithium-ion batteries.

[0078] In the embodiments of this application, the above-mentioned ester-based nitrile compounds can be prepared by different methods. The specific preparation method is not limited. It can be reasonably and comprehensively designed based on the conventional preparation process of methyl cyanoacetate substitution reaction and the properties of the substituent groups.

[0079] In some embodiments, taking the ester-based nitrile compound as an example, it can be prepared in the following manner:

[0080] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of diisopropylethylamine and 2 g of trichlorosilane. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. The mixture was then extracted, washed with water, dried, and further purified by column chromatography to obtain compound 1.

[0081] In other embodiments, taking the case where the ester-based nitrile compound is compound 2 as an example, it can be prepared in the following manner:

[0082] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of trimethyltrifluoromethylsilane. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. The mixture was then extracted, washed with water, dried, and further purified by column chromatography to obtain compound 2.

[0083] In some other embodiments, taking the case where the ester-based nitrile compound is compound 3 as an example, it can be prepared in the following manner:

[0084] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of sodium hydroxide and 5 ml of methanol. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. Extraction, washing with water, and drying were then performed, followed by further purification by column chromatography to obtain compound 3.

[0085] In some other embodiments, taking the ester-based nitrile compound as compound 4 above as an example, it can be prepared in the following manner:

[0086] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of difluoromethyl iodine. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. The mixture was then extracted, washed with water, dried, and further purified by column chromatography to obtain compound 4.

[0087] In some other embodiments, taking the case where the ester-based nitrile compound is compound 5 as an example, it can be prepared in the following manner:

[0088] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of trifluoromethanesulfonyl fluoride. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. Extraction, washing with water, and drying were then performed, followed by further purification by column chromatography to obtain compound 5.

[0089] In some other embodiments, taking the ester-based nitrile compound as compound 6 above as an example, it can be prepared in the following manner:

[0090] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 ml of boron trifluoride-methanol solution. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. Extraction, washing with water, and drying were then performed, followed by further purification by column chromatography to obtain compound 6.

[0091] In some other embodiments, taking the ester-based nitrile compound as compound 7 above as an example, it can be prepared in the following manner:

[0092] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 3 g of N-fluorinated benzenesulfonamide. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until the reaction was complete. The mixture was then extracted, washed with water, dried, and further purified by column chromatography to obtain compound 7.

[0093] In some other embodiments, taking the case where the ester-based nitrile compound is compound 8 as an example, it can be prepared in the following manner:

[0094] 10 g of methyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of phenyl Grignard reagent (PhMgBr). The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. Extraction, washing with water, and drying were then performed, followed by further purification by column chromatography to obtain compound 8.

[0095] In some other embodiments, taking the ester-based nitrile compound as compound 9 above as an example, it can be prepared in the following manner:

[0096] 10 g of butyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 ml of boron trifluoride-methanol solution. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. Extraction, washing with water, and drying were then performed, followed by further purification by column chromatography to obtain compound 9.

[0097] In some other embodiments, taking the ester-based nitrile compound as an example, it can be prepared in the following manner:

[0098] 10 g of methyl 2-cyano-2-methylpropionate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of sulfonyl chloride. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until the reaction was complete. The mixture was then extracted, washed with water, dried, and further purified by column chromatography to obtain compound 10.

[0099] In some other embodiments, taking the case where the ester-based nitrile compound is compound 11 as an example, it can be prepared in the following manner:

[0100] 10 g of ethyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of pyridine chloride. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until completion. Extraction, washing with water, and drying were then performed, followed by further purification by column chromatography to obtain compound 11.

[0101] In some other embodiments, taking the ester-based nitrile compound as compound 12 above as an example, it can be prepared in the following manner:

[0102] 10 g of isopropyl cyanoacetate was dissolved in 50 ml of tetrahydrofuran, followed by the addition of 1 g of triethylamine and 2 g of trimethyltrifluoromethylsilane. The mixture was stirred at room temperature, and the reaction progress was monitored by thin-layer chromatography until the reaction was complete. The mixture was then extracted, washed with water, dried, and further purified by column chromatography to obtain compound 12.

[0103] Electrolyte

[0104] The electrolyte in this application embodiment includes a non-aqueous organic solvent and an electrolyte salt. The non-aqueous organic solvent includes a first solvent, which includes an ester-based nitrile compound according to this application embodiment.

[0105] In some embodiments, the volume content of the ester-based nitrile compound in the non-aqueous organic solvent is 2% to 80%, including but not limited to 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%. In the electrolyte of this application embodiment, the volume content of the ester-based nitrile compound in the non-aqueous organic solvent is within the above range, resulting in a high ionic conductivity of the electrolyte even at low temperatures, improving the low-temperature performance of the lithium-ion battery; simultaneously, it improves the oxidation resistance of the electrolyte and inhibits the dissolution of the positive electrode transition metal, giving the electrolyte better thermal stability at high temperatures, thereby improving the high-temperature performance of the lithium-ion battery; if it is less than 2%, the improvement effect on the high and low temperature performance of the lithium-ion battery is not significant; if it is greater than 80%, only the high-temperature performance can be improved, and the low-temperature performance cannot be improved simultaneously.

[0106] In some embodiments, the electrolyte further includes additives, including but not limited to at least one of the following: tris(pentafluorophenyl)borane, tris(trimethylsilyl) borate, tris(2,2,2-trifluoroethyl) borate, 2,4,6-trimethoxyboronoxane, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, trimethylsilanol, alkylolamide, polyacrylamide, trimethyl phosphite, vinylene carbonate, vinyl sulfite, propylene sulfite, butene sulfite, ethylene sulfite, 4-methyl ethylene sulfite, fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate, lithium nitrate, dichloromethane, tris(2,2,2-trifluoroethyl) phosphite, 3,5-bis(trifluoromethyl)phenylboronic acid, butyrate lactone, acrylonitrile, 12-crown-4-ether, 18-crown-6-ether, methyl difluoroacetate, ethyl difluoroacetate, lithium nitrate, lithium carbonate, and carbon dioxide (gaseous).

[0107] In the embodiments of this application, the above-mentioned additives have two functions: First, they can effectively isolate lithium ions and anionic groups, increase the migration number of electrolyte salt metal ions such as lithium ions, and form a uniform and stable low-resistance solid electrolyte interface film, which also improves the low-temperature performance of the battery. Second, they can work synergistically with the selected non-aqueous organic solvent to form a passivation film mainly composed of polymer components on the surface of the aluminum current collector, thereby inhibiting the corrosion of the aluminum current collector and enhancing the compatibility between the wide-temperature-range electrolyte and the aluminum current collector.

[0108] As an optional example, the above-mentioned additive is at least one of tris(pentafluorophenyl)borane, fluoroethylene carbonate, vinylene carbonate, butene sulfite, lithium nitrate, difluoroethylene carbonate, 12-crown-4-ether, trimethyl phosphite, and butyryl lactone.

[0109] In some embodiments, the mass content of the above-mentioned additive in the electrolyte is from 0.02% to 8%, including but not limited to 0.02%, 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%. In the electrolyte of the embodiments of this application, when the mass content of the additive in the electrolyte is within the above range, it can improve the stability of the electrode / electrolyte interface and extend the cycle life of the lithium-ion battery; if it is less than 0.02%, the improvement effect on the cycle life of the lithium-ion battery is not significant; if it is greater than 8%, it will increase the viscosity of the electrolyte and deteriorate the low-temperature performance of the lithium-ion battery.

[0110] In some embodiments, the non-aqueous organic solvent further includes a second solvent, which includes, but is not limited to, at least one of cyclic carbonates, chain carbonates, chain carboxylic esters, etc.

[0111] In some embodiments, the cyclic carbonate has a volume content of 5% to 50% in a non-aqueous organic solvent, including but not limited to 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%.

[0112] In some embodiments, the chain carbonate has a volume content of 10% to 70% in a non-aqueous organic solvent, including but not limited to 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0113] In some embodiments, the chain carboxylic acid ester has a volume content of 0.01% to 70% in a non-aqueous organic solvent, including but not limited to 0.01%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0114] As an optional example, the first solvent is an ester-based nitrile compound from the embodiments of this application, and the second solvent is a mixed solvent of cyclic carbonate, linear carbonate, and linear carboxylic acid ester, wherein the volume ratio of the cyclic carbonate, linear carbonate, linear carboxylic acid ester, and ester-based nitrile compound is (5-50):(10-70):(0.01-70):(2-80), including but not limited to 5:25:30:40, 5:45:0.01:49.99, 35:40:20:5, 50:10:1:39, or 5:10:15:70, etc.

[0115] As another optional example, the first solvent is the ester-based nitrile compound of the present application embodiments, and the second solvent is a mixed solvent of cyclic carbonate and chain carbonate, wherein the volume ratio of cyclic carbonate, chain carbonate and ester-based nitrile compound is (5-50):(10-70):(2-80), including but not limited to 5:30:65, 5:40:55, 5:70:25, 50:45:5, 30:30:40 or 3:15:80, etc.

[0116] By way of non-limiting example, cyclic carbonates include, but are not limited to, at least one of ethylene carbonate, propylene carbonate, 1,4-butyrolactone, etc.

[0117] By way of non-limiting example, chain carbonates include, but are not limited to, at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0118] By way of non-limiting example, chain 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 their fluorine analogs.

[0119] In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium salt, sodium salt, potassium salt, etc.

[0120] As an optional example, the electrolyte salt is a lithium salt. By way of non-limiting enumeration, the lithium 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(oxalateborate), lithium difluorooxalateborate, lithium difluorophosphate, and lithium bis(pentafluoroethylsulfonyl)imino.

[0121] In some embodiments, the concentration of the electrolyte salt in the electrolyte is from 0.05 mol / L to 1.8 mol / L, including but not limited to 0.05 mol / L, 0.1 mol / L, 0.25 mol / L, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, 1.5 mol / L, or 1.75 mol / L.

[0122] The electrolyte in this embodiment of the application has at least the following beneficial effects:

[0123] 1. By introducing ester-based nitrile compounds as shown in Formula I, the viscosity of the electrolyte is effectively reduced due to their low viscosity, and the low-temperature liquid range of the electrolyte is widened, resulting in high ionic conductivity of the electrolyte even in low-temperature environments. Furthermore, due to the large steric hindrance of the ester-based nitrile compounds shown in Formula I, their interaction with lithium ions is weak, resulting in low desolvation energy of lithium ions at the electrode / electrolyte interface, thus enabling the lithium-ion battery to exhibit excellent low-temperature performance. Simultaneously, the selected additives can effectively isolate lithium-ion and anion groups, increase the lithium-ion transference number, and form a uniform and stable low-resistivity solid electrolyte interface film, further improving the low-temperature performance of the battery.

[0124] 2. By introducing ester-based nitrile compounds as shown in Formula I, the cyano groups can inhibit the oxidation of other components of the electrolyte by the positive electrode through complexation of the active sites on the positive electrode surface, thereby improving the oxidation resistance of the electrolyte and inhibiting the dissolution of transition metals from the positive electrode. Furthermore, the selected additives can synergistically work with the selected non-aqueous organic solvents to form a passivation film mainly composed of polymer components on the surface of the aluminum current collector, thereby inhibiting corrosion of the aluminum current collector and enhancing the compatibility between the wide-temperature-range electrolyte and the aluminum current collector.

[0125] 3. The electrolyte is a wide-temperature-range electrolyte. Lithium-ion batteries containing this electrolyte can operate stably in the full temperature range of -60℃ to 80℃, exhibiting excellent low-temperature and high-temperature performance.

[0126] <Electrochemical Device>

[0127] The electrochemical device of this application includes the electrolyte of this application.

[0128] In some embodiments, the electrochemical device described above includes, but is not limited to, secondary batteries such as lithium-ion batteries, capacitors, etc. The secondary battery is not limited to one of the following: button cell, pouch cell, square aluminum-cased cell, or cylindrical cell.

[0129] As a preferred example, the electrochemical device described above is a lithium-ion battery.

[0130] In some embodiments, the electrochemical device further includes a positive electrode, which includes a positive electrode active material, including but not limited to 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, fluorinated graphite, MnO2, FeS2, FeF3, etc.

[0131] In some embodiments, the positive electrode further includes a positive electrode material, which includes the aforementioned positive electrode active material, positive electrode conductive agent, and positive electrode binder. In the embodiments of this application, there are no particular limitations on the specific selection of the positive electrode conductive agent and positive electrode binder. As a non-limiting example, the positive electrode conductive agent 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.

[0132] In some embodiments, the positive electrode further includes a positive electrode current collector, the surface of which is provided with a positive electrode material layer, the material of which is the aforementioned positive electrode material. The positive electrode current collector may be selected to contain aluminum or any other suitable conductive metal foil (e.g., solid, 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 contain a surface-treated (e.g., carbon-coated and / or etched) metal foil.

[0133] In some embodiments, the electrochemical device further includes a negative electrode, which includes a negative electrode active material, including but not limited to at least one of lithium titanate, highly stabilized pyrolytic graphite, artificial graphite, natural graphite, graphitized mesophase carbon microspheres, silicon suboxide, silicon-carbon composite negative electrode material, lithium metal negative electrode material, and composite lithium metal negative electrode material.

[0134] By way of non-limiting example, silicon-carbon composite anode materials include, but are not limited to, at least one of graphite-doped silicon-oxygen materials, graphite-doped pre-magnesium silicon-oxygen materials, graphite-doped pre-lithium silicon-oxygen materials, and silane-deposited silicon-carbon materials.

[0135] By way of non-limiting example, composite metal lithium anode materials include, but are not limited to, at least one of lithium-carbon composite anode materials, lithium-tin composite anode materials, and lithium-silver composite anode materials.

[0136] In some embodiments, the electrochemical device further includes a separating membrane disposed between the positive and negative electrodes.

[0137] In some embodiments, the separator is including, but is not limited to, at least one of the following: polyethylene (PE), polypropylene (PP), polyolefin (PO) separators based on polytetrafluoroethylene, polyester membranes (e.g., polyethylene diethyl terephthalate (PET) membranes), cellulose membranes, polyimide membranes (PI), polyamide membranes (PA), spandex or aramid membranes, woven membranes, nonwoven membranes (non-woven fabrics), microporous membranes, composite membranes, separator paper, rolled membranes, or spun membranes.

[0138] It should be noted that in the embodiments of this application, there are no restrictions on the specific technical parameters such as the thickness of the positive electrode, negative electrode, and separator, as long as the purpose of this application can be achieved.

[0139] The preparation method of the electrochemical device in the embodiments of this application is not limited and can be any method known to those skilled in the art.

[0140] <Vehicles>

[0141] The vehicle in this application embodiment includes the electrochemical device of this application embodiment.

[0142] By way of a non-limiting example, the above-mentioned vehicles include, but are not limited to, automobiles, motorcycles, electric bicycles, bicycles, power tools, etc.

[0143] The following non-limiting embodiments further illustrate certain features of the present technology.

[0144]

[0145] The pouch cells involved in the following embodiments and comparative examples all include a positive electrode, a negative electrode, and a separator. Wherein:

[0146] The positive electrode sheet includes a positive current collector and positive electrode material layers disposed on opposite sides of the positive current collector. The positive current collector is an aluminum foil with a thickness of 20 μm. 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.

[0147] The negative electrode sheet includes a negative current collector and negative electrode material layers disposed on opposite sides of the negative current collector. The negative current collector is an aluminum foil with a thickness of 12 μm. 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).

[0148] All diaphragms are porous polyethylene (PE) membranes, and the thickness of each diaphragm is 20 μm.

[0149] Example 1

[0150] (electrolyte)

[0151] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0152] The non-aqueous organic solvent consists of the following components in volume fractions: 15% ethylene carbonate, 30% methyl ethyl carbonate, and 55% compound 1.

[0153] 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 0.8 mol / L and the concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0.2 mol / L.

[0154] The additives are tris(pentafluorophenyl)borane and fluoroethylene carbonate, wherein tris(pentafluorophenyl)borane accounts for 1.0% of the total mass of the electrolyte and fluoroethylene carbonate accounts for 1.5% of the total mass of the electrolyte.

[0155] (Preparation of electrolyte)

[0156] In a dry room (dew point below -40°C), ethylene carbonate, ethyl methyl carbonate and compound 1 are mixed evenly according to volume fraction. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0157] (The manufacture of lithium-ion batteries)

[0158] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 1.

[0159] Example 2

[0160] (electrolyte)

[0161] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0162] The non-aqueous organic solvent consists of the following components in volume fractions: 20% propylene carbonate, 20% dimethyl carbonate, and 60% compound 2.

[0163] The lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1 mol / L.

[0164] The additives are vinylene carbonate and butylene sulfite, wherein vinylene carbonate accounts for 1.5% of the total mass of the electrolyte and butylene sulfite accounts for 0.5% of the total mass of the electrolyte.

[0165] (Preparation of electrolyte)

[0166] In a dry room (dew point below -40°C), propylene carbonate, dimethyl carbonate and compound 2 are mixed evenly according to volume fraction. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0167] (The manufacture of lithium-ion batteries)

[0168] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 2.

[0169] Example 3

[0170] (electrolyte)

[0171] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0172] The non-aqueous organic solvent consists of the following components in volume fractions: 10% ethylene carbonate, 30% propylene carbonate, 10% methyl formate, and 50% compound 3.

[0173] The lithium salt is lithium bis(trifluoromethanesulfonylimide), and its concentration in the electrolyte is 1.2 mol / L.

[0174] The additive is lithium nitrate, which accounts for 0.025% of the total mass of the electrolyte.

[0175] (Preparation of electrolyte)

[0176] In a dry room (dew point below -40°C), ethylene carbonate, propylene carbonate, methyl formate and compound 3 are mixed evenly according to volume fraction. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0177] (The manufacture of lithium-ion batteries)

[0178] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 3.

[0179] Example 4

[0180] (electrolyte)

[0181] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0182] The non-aqueous organic solvent consists of the following components in volume fractions: 20% propylene carbonate and 80% compound 4.

[0183] 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 1.0 mol / L and the concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0.2 mol / L.

[0184] The additives are ethylene difluorocarbonate and ethylene sulfite, wherein ethylene difluorocarbonate accounts for 1.0% of the total mass of the electrolyte and ethylene sulfite accounts for 1.5% of the total mass of the electrolyte.

[0185] (Preparation of electrolyte)

[0186] In a dry room (dew point below -40°C), propylene carbonate and compound 4 are mixed evenly according to volume fraction, and then lithium salt is slowly added and stirred thoroughly to form a mixed solution. Then, additives are added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0187] (The manufacture of lithium-ion batteries)

[0188] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 4.

[0189] Example 5

[0190] (electrolyte)

[0191] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0192] The non-aqueous organic solvent consists of the following components in volume fractions: 10% ethylene carbonate, 30% diethyl carbonate, 20% isobutyl acetate, and 40% compound 5.

[0193] The lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 1.8 mol / L.

[0194] The additives are 12-crown-4-ether and trimethyl phosphite, wherein the mass of 12-crown-4-ether accounts for 0.5% of the total mass of the electrolyte, and the mass of trimethyl phosphite accounts for 1.0% of the total mass of the electrolyte.

[0195] (Preparation of electrolyte)

[0196] In a dry room (dew point below -40°C), ethylene carbonate, diethyl carbonate, isobutyl acetate and compound 5 are mixed evenly according to volume fraction. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0197] (The manufacture of lithium-ion batteries)

[0198] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 5.

[0199] Example 6

[0200] (electrolyte)

[0201] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0202] The non-aqueous organic solvent consists of the following components in volume fractions: 25% propylene carbonate, 30% dimethyl carbonate, and 45% compound 6.

[0203] The lithium salt is a mixed salt of lithium bis(fluorosulfonyl)imide and lithium difluorooxalate borate, wherein the concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0.8 mol / L and the concentration of lithium difluorooxalate borate in the electrolyte is 0.2 mol / L.

[0204] The additives are vinylene carbonate and ethylene sulfite, wherein vinylene carbonate accounts for 2.0% of the total mass of the electrolyte and ethylene sulfite accounts for 1.0% of the total mass of the electrolyte.

[0205] (Preparation of electrolyte)

[0206] In a dry room (dew point below -40°C), propylene carbonate, dimethyl carbonate and compound 6 are mixed evenly in volume fraction ratio, and then lithium salt is slowly added and stirred thoroughly to form a mixed solution. Then, additives are added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0207] (The manufacture of lithium-ion batteries)

[0208] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 6.

[0209] Example 7

[0210] (electrolyte)

[0211] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0212] The non-aqueous organic solvent consists of the following components in volume fractions: 20% ethylene carbonate, 30% methyl acetate, and 50% compound 7.

[0213] The lithium salt is a mixed lithium salt of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorophosphate, wherein the concentration of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte is 0.9 mol / L and the concentration of lithium difluorophosphate in the electrolyte is 0.1 mol / L.

[0214] The additives are butyrolactone and fluoroethylene carbonate, wherein butyrolactone accounts for 3% of the total mass of the electrolyte and fluoroethylene carbonate accounts for 5% of the total mass of the electrolyte.

[0215] (Preparation of electrolyte)

[0216] In a dry room (dew point below -40°C), ethylene carbonate, methyl acetate and compound 7 are mixed evenly in volume fraction ratio, and then lithium salt is slowly added and stirred thoroughly to form a mixed solution. Then, additives are added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0217] (The manufacture of lithium-ion batteries)

[0218] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 7.

[0219] Example 8

[0220] (electrolyte)

[0221] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0222] The non-aqueous organic solvent consists of the following components in volume fractions: 10% propylene carbonate, 30% ethyl acetate, and 60% compound 8.

[0223] The lithium salt is lithium bis(trifluoromethanesulfonylimide), and its concentration in the electrolyte is 1.1 mol / L.

[0224] The additive is ethylene difluorocarbonate, which accounts for 1.5% of the total mass of the electrolyte.

[0225] (Preparation of electrolyte)

[0226] In a dry room (dew point below -40°C), propylene carbonate, ethyl acetate and compound 8 are mixed evenly in volume fraction, and then lithium salt is slowly added and stirred thoroughly to form a mixed solution. Then, additives are added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0227] (The manufacture of lithium-ion batteries)

[0228] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 8.

[0229] Example 9

[0230] (electrolyte)

[0231] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0232] The non-aqueous organic solvent consists of the following components in volume fractions: 15% ethylene carbonate, 35% isobutyl acetate, and 50% compound 9.

[0233] The lithium salt is a mixed lithium salt of lithium tetrafluoroborate and lithium difluorophosphate, wherein the concentration of lithium tetrafluoroborate in the electrolyte is 0.9 mol / L and the concentration of lithium difluorophosphate in the electrolyte is 0.1 mol / L.

[0234] The additive is tris(trimethylsilyl) borate, which accounts for 2% of the total mass of the electrolyte.

[0235] (Preparation of electrolyte)

[0236] In a dry room (dew point below -40°C), ethylene carbonate, isobutyl acetate and compound 9 are mixed evenly in volume fraction ratio, and then lithium salt is slowly added and stirred thoroughly to form a mixed solution. Then, additives are added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0237] (The manufacture of lithium-ion batteries)

[0238] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 9.

[0239] Example 10

[0240] (electrolyte)

[0241] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0242] The non-aqueous organic solvent consists of the following components in volume fractions: 30% propylene carbonate, 25% isobutyl formate, and 45% compound 10.

[0243] The lithium salt is a mixed lithium salt of lithium hexafluorophosphate and lithium tetrafluoroborate, wherein the concentration of lithium hexafluorophosphate in the electrolyte is 0.7 mol / L and the concentration of lithium tetrafluoroborate in the electrolyte is 0.3 mol / L.

[0244] The additives are vinyl sulfite and vinylene carbonate, wherein the mass of vinyl sulfite accounts for 1% of the total mass of the electrolyte and the mass of vinylene carbonate accounts for 2% of the total mass of the electrolyte.

[0245] (Preparation of electrolyte)

[0246] In a dry room (dew point below -40°C), propylene carbonate, isobutyl formate, and compound 10 are mixed evenly in volume fractions. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0247] (The manufacture of lithium-ion batteries)

[0248] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 10.

[0249] Example 11

[0250] (electrolyte)

[0251] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0252] The non-aqueous organic solvent consists of the following components in volume fractions: 15% propylene carbonate, 30% ethyl acrylate, and 55% compound 11.

[0253] The lithium salt is a mixed lithium salt of lithium bis(fluorosulfonyl)imide and lithium hexafluorophosphate, wherein the concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is 0.6 mol / L and the concentration of lithium hexafluorophosphate in the electrolyte is 0.4 mol / L.

[0254] The additive is trimethyl phosphite, which accounts for 3.5% of the total mass of the electrolyte.

[0255] (Preparation of electrolyte)

[0256] In a dry room (dew point below -40°C), propylene carbonate, ethyl acrylate and compound 11 are mixed evenly according to volume fraction. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0257] (The manufacture of lithium-ion batteries)

[0258] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 11.

[0259] Example 12

[0260] The electrolyte in this embodiment includes a non-aqueous organic solvent, a lithium salt, and additives. Wherein:

[0261] The non-aqueous organic solvent consists of the following components in volume fractions: 35% ethylene carbonate, 45% methyl formate, and 20% compound 12.

[0262] The lithium salt is a mixed lithium salt of lithium difluorooxalate borate and lithium tetrafluoroborate, wherein the concentration of lithium difluorooxalate borate in the electrolyte is 0.6 mol / L and the concentration of lithium tetrafluoroborate in the electrolyte is 0.5 mol / L.

[0263] The additives are vinylene carbonate and propylene sulfite, wherein vinylene carbonate accounts for 2.5% of the total mass of the electrolyte and propylene sulfite accounts for 1% of the total mass of the electrolyte.

[0264] (Preparation of electrolyte)

[0265] In a dry room (dew point below -40°C), ethylene carbonate, methyl formate and compound 12 are mixed evenly according to volume fraction. Lithium salt is then slowly added and stirred thoroughly to form a mixed solution. Additives are then added to the mixed solution and stirred evenly again to obtain the electrolyte of this embodiment.

[0266] (The manufacture of lithium-ion batteries)

[0267] The electrolyte prepared in this embodiment is injected into a soft-pack battery. After standing, formation and capacity testing, the lithium-ion battery of this embodiment is obtained and labeled as lithium-ion battery 12.

[0268] Example 13 (Lower limit for ester-based nitrile compounds)

[0269] This embodiment is basically the same as embodiment 1, except that:

[0270] In the electrolyte, the non-aqueous organic solvent consists of the following components in volume fractions: 32% ethylene carbonate, 63% methyl ethyl carbonate, and 2% compound 1.

[0271] In the manufacture of lithium-ion batteries, the electrolyte used in this embodiment is adopted, and the resulting lithium-ion battery is labeled as lithium-ion battery 13.

[0272] Example 14 (Electrolyte without additives)

[0273] This embodiment is basically the same as embodiment 1, except that:

[0274] The electrolyte contains no additives.

[0275] In the manufacture of lithium-ion batteries, the electrolyte used in this embodiment is adopted, and the resulting lithium-ion battery is labeled as lithium-ion battery 14.

[0276] Example 15 (Lower limit of lithium salt concentration)

[0277] This embodiment is basically the same as embodiment 1, except that:

[0278] The lithium salt is lithium hexafluorophosphate, and its concentration in the electrolyte is 0.05 mol / L.

[0279] In the manufacture of lithium-ion batteries, the electrolyte used in this embodiment is adopted, and the resulting lithium-ion battery is labeled as lithium-ion battery 15.

[0280] Comparative Example 1

[0281] (electrolyte)

[0282] The electrolyte in this comparative example includes a non-aqueous organic solvent and a lithium salt. Specifically:

[0283] The non-aqueous organic solvent consists of the following components in volume fractions: 30% ethylene carbonate, 30% dimethyl carbonate and 30% diethyl carbonate.

[0284] The lithium salt is lithium bis(fluorosulfonyl)imide, and the concentration of the lithium salt in the electrolyte is 1 mol / L.

[0285] (Preparation of electrolyte)

[0286] In a dry room (dew point below -40°C), ethylene carbonate, dimethyl carbonate and diethyl carbonate are mixed evenly in volume fraction ratio, and then lithium salt is slowly added and stirred thoroughly to form a mixed solution, thus obtaining the electrolyte of this comparative example.

[0287] (The manufacture of lithium-ion batteries)

[0288] The electrolyte prepared in this comparative example was injected into a pouch cell. After standing, formation and capacity testing, the lithium-ion battery of this comparative example was obtained and labeled as lithium-ion battery D1.

[0289] Comparative Example 2

[0290] This comparative example is basically the same as Example 1, except that:

[0291] The electrolyte and its preparation method do not contain compound 1; the non-aqueous organic solvent consists of the following components in volume fractions: 33% ethylene carbonate and 67% methyl ethyl carbonate.

[0292] In the manufacture of lithium-ion batteries, the electrolyte used in this comparative example is used, and the resulting lithium-ion battery is labeled as D2.

[0293] II. Performance Testing

[0294] Viscosity test: Inject the electrolyte of the example or comparative example into the test cup, select a rotor with a diameter of 16 mm and set the rotation speed to 1500 rpm, start the viscometer and record the viscosity reading.

[0295] Conductivity test: At a stable test temperature (25℃ or -20℃), inject the electrolyte sample of the example or comparative example into the conductivity cell, ensuring that the electrolyte completely submerges the conductivity electrode, and record the conductivity measurement value.

[0296] High-temperature cycle performance test: After formation and capacity testing, the batteries obtained in each example and comparative example were charged at 45°C with a constant current of 1C to a voltage of 4.25V, then discharged at a constant voltage to a current of 0.05C, rested for 10 minutes, and then discharged at a constant current of 1C to 2.5V. This constitutes one charge-discharge cycle. The obtained batteries were subjected to 500 charge-discharge cycles at 45°C.

[0297] Low-temperature discharge performance test: After formation and capacity testing, the batteries obtained in each example and comparative example were charged at 25°C with a constant current of 1C to a voltage of 4.25V, and then discharged at a constant voltage to a current of 0.05C. The fully charged batteries were discharged at -60°C and -20°C with a constant current of 1C to 2.5V, respectively. The discharge capacity was recorded to complete the low-temperature discharge performance test.

[0298] The electrolyte properties and battery performance test results of each embodiment and comparative example are shown in Table 1 and Table 2, respectively.

[0299] Table 1. Electrolyte properties of each embodiment and comparative example.

[0300]

[0301] As shown in Table 1, the electrolytes of the embodiments of this application exhibit lower viscosity and higher ionic conductivity at -20°C compared to the electrolytes of the comparative examples. Comparing Example 1 and Comparative Example 2, it can be seen that adding compound 1 of this application to the electrolyte can reduce the viscosity of the electrolyte at 25°C and increase the ionic conductivity at that temperature; simultaneously, it can significantly improve the low-temperature performance of the electrolyte. Specifically, at -20°C, the viscosity of the electrolyte in Example 1 is reduced by 76.7% compared to Comparative Example 2, and the ionic conductivity is increased by 11.29 times compared to Comparative Example 2. Comparing Example 1 and Example 14, it can be seen that in the electrolytes of the embodiments of this application, the additives have little effect on the viscosity and ionic conductivity at 25°C, but do affect the viscosity and ionic conductivity of the electrolyte at -20°C—the viscosity decreases slightly, and the ionic conductivity increases slightly.

[0302] Table 2 shows the performance test results of the batteries in each embodiment and comparative example.

[0303]

[0304]

[0305] As shown in Table 2, compared to Comparative Examples 1 and 2, the batteries in Examples 1-15 all exhibit higher capacity retention rates after 500 cycles at 45°C, -60°C, and -20°C. This indicates that the ester-based nitrile compounds of this application, in synergy with additives, enable lithium-ion batteries to exhibit excellent low-temperature and high-temperature performance. Furthermore, comparing Examples 1, 14, and Comparative Example 1 shows that the ester-based nitrile compounds of this application simultaneously improve both high-temperature and low-temperature performance. However, their synergistic effect with additives is even better in improving the high-temperature and low-temperature performance of lithium-ion batteries, while additives alone have limited effect on improving these performance characteristics.

[0306] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0307] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0308] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An ester-based nitrile compound, characterized in that, The ester-based nitrile compound has the structure shown in Formula I: R1 is selected from one of straight-chain alkyl, substituted straight-chain alkyl, branched alkyl, substituted branched alkyl, alkoxy, substituted alkoxy, silyl, substituted silyl, heterocyclic alkyl, substituted heterocyclic alkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl; R2 and R3 are each independently selected from one of hydrogen, halogen, straight-chain alkyl, substituted straight-chain alkyl, branched alkyl, substituted branched alkyl, silyl, substituted silyl, heterocyclic alkyl, substituted heterocyclic alkyl, aryl, substituted aryl, heteroaryl, and substituted heteroaryl.

2. The ester-based nitrile compound according to claim 1, characterized in that, The substituted linear alkyl group, the substituted branched alkyl group, the substituted alkoxy group, the substituted silyl group, the substituted heterocyclic alkyl group, the substituted aryl group, and the substituted heteroaryl group all include one of C1-10 alkyl, halogen, nitro, cyano, and sulfonic acid groups. And / or, R1 is selected from one of the following: straight-chain C1-C10 alkyl, substituted straight-chain C1-C10 alkyl, branched C3-C10 alkyl, substituted branched C3-C10 alkyl, C1-C10 alkoxy, substituted C1-C10 alkoxy, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C6-C10 aryl, substituted C6-C10 aryl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl; And / or, R2 and R3 are each independently selected from one of hydrogen, halogen, straight-chain C1-C10 alkyl, substituted straight-chain C1-C10 alkyl, branched C3-C10 alkyl, substituted branched C3-C10 alkyl, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C6-C10 aryl, substituted C6-C10 aryl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

3. The ester-based nitrile compound according to claim 1, characterized in that, R1 is selected from one of the following: straight-chain C7-C10 alkyl, substituted straight-chain C7-C10 alkyl, branched C7-C10 alkyl, substituted branched C7-C10 alkyl, C1-C10 alkoxy, substituted C1-C10 alkoxy, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl. And / or, R2 and R3 are each independently selected from one of the following: straight-chain C7-C10 alkyl, substituted straight-chain C7-C10 alkyl, branched C7-C10 alkyl, substituted branched C7-C10 alkyl, silyl, substituted silyl, C3-C6 heterocyclic alkyl, substituted C3-C6 heterocyclic alkyl, C2-C10 heteroaryl, and substituted C2-C10 heteroaryl.

4. The ester-based nitrile compound according to claim 1, characterized in that, R1 is selected from one of the following: straight-chain C1-C6 alkyl, substituted straight-chain C1-C6 alkyl, branched C3-C6 alkyl, substituted branched C3-C6 alkyl, C1-C6 alkoxy, substituted C1-C6 alkoxy, silyl, substituted silyl, C6-C10 aryl, substituted C6-C10 aryl, C6-C10 heteroaryl, or substituted C2-C10 heteroaryl. And / or, R2 and R3 are each independently selected from one of hydrogen, halogen, straight-chain C1-C6 alkyl, substituted straight-chain C1-C6 alkyl, branched C3-C6 alkyl, substituted branched C3-C6 alkyl, silyl, substituted silyl, C6-C10 aryl, substituted C6-C10 aryl, C6-C10 heteroaryl or substituted C2-C10 heteroaryl.

5. The ester-based nitrile compound according to claim 1, characterized in that, The ester-based nitrile compound is selected from at least one of compound 1 to compound 12; 6. An electrolyte, characterized in that, It includes a non-aqueous organic solvent and an electrolyte salt, wherein the non-aqueous organic solvent includes a first solvent, and the first solvent includes an ester-based nitrile compound as described in any one of claims 1 to 5.

7. The electrolyte according to claim 6, characterized in that, The ester-based nitrile compound has a volume content of 2% to 80% in the non-aqueous organic solvent.

8. The electrolyte according to claim 6, characterized in that, The electrolyte further includes additives, which include at least one of the following: tris(pentafluorophenyl)borane, tris(trimethylsilyl) borate, tris(2,2,2-trifluoroethyl) borate, 2,4,6-trimethoxyboronoxane, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, trimethylsilanol, alkylolamide, polyacrylamide, trimethyl phosphite, vinylene carbonate, vinyl sulfite, propylene sulfite, butene sulfite, ethylene sulfite, 4-methyl ethylene sulfite, fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate, lithium nitrate, dichloromethane, tris(2,2,2-trifluoroethyl) phosphite, 3,5-bis(trifluoromethyl)phenylboronic acid, butyrate lactone, acrylonitrile, 12-crown-4-ether, 18-crown-6-ether, methyl difluoroacetate, ethyl difluoroacetate, lithium nitrate, lithium carbonate, and carbon dioxide.

9. The electrolyte according to claim 8, characterized in that, The additive is present in the electrolyte at a mass content of 0.02% to 8%.

10. The electrolyte according to claim 6, characterized in that, The non-aqueous organic solvent further includes a second solvent, which includes at least one of cyclic carbonates, chain carbonates, and chain carboxylic esters; And / or, the electrolyte salt includes at least one of lithium salt, sodium salt, and potassium salt.

11. The electrolyte according to claim 10, characterized in that, The cyclic carbonate has a volume content of 5% to 50% in the non-aqueous organic solvent; And / or, the chain carbonate has a volume content of 10% to 70% in the non-aqueous organic solvent; And / or, the chain carboxylic acid ester has a volume content of 0.01% to 70% in the non-aqueous organic solvent; And / or, the concentration of the electrolyte salt in the electrolyte is from 0.05 mol / L to 1.8 mol / L.

12. An electrochemical device, characterized in that, Includes the electrolyte as described in any one of claims 6 to 11.

13. A vehicle, characterized in that, Includes the electrochemical device as described in claim 12.

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