Electrolytes and electrochemical devices

Abstract

The present invention relates to an electrolyte and an electrochemical device. Specifically, the present invention provides an electrolyte containing a compound represented by formula IA and a compound represented by formula IB, wherein the contents of the compound represented by formula IA and the compound represented by formula IB are each within the range of 0.12% to 5.1% by mass of the electrolyte. The electrolyte of the present invention is useful for improving the high-temperature storage characteristics, safety performance, and low-temperature discharge characteristics of an electrochemical device. [Formula 1] TIFF2026505358000028.tif5581

Description

[Technical Field]

[0001] The present invention relates to the field of energy storage, and in particular to electrolytes and electrochemical devices. [Background technology]

[0002] As electrochemical devices (e.g., lithium-ion batteries) are widely used in various electronic products, users are placing increasingly higher demands on the performance of electrochemical devices, such as thinner, lighter, and higher power. All of these performance characteristics are related to the high energy density of electrochemical devices. Increasing the charging voltage is one of the main ways to improve the energy density of electrochemical devices. However, increasing the charging voltage can destabilize the positive electrode active materials (especially high-valent transition metals), accelerating the decomposition of the electrolyte and generating gas, which has a serious impact on the lifespan and safety performance of electrochemical devices. In addition, people are increasingly placing demands on the environmental resistance of electrochemical devices, such as low-temperature discharge characteristics. This in turn increases the requirements for electrolytes.

[0003] In view of this situation, there is a need to provide an electrolyte and an electrochemical device that can provide improved high temperature storage characteristics and safety performance while maintaining good low temperature discharge characteristics. Summary of the Invention

[0004] SUMMARY OF THE INVENTION The present invention provides an electrolyte and electrochemical device to solve, in part, at least one of the problems existing in the related art.

[0005] According to one aspect of the present invention, there is provided an electrolyte comprising a compound represented by formula IA and a compound represented by formula IB,

[0006] [ka]

[0007] R 11is a substituted or unsubstituted C1-C 10 alkylene groups, substituted or unsubstituted C5-C 15 or a substituted or unsubstituted C6-C 15 and the aryl group is selected from the group consisting of R 12 , R 13 and R 14 are each independently selected from a single bond, a C1-C5 alkylene group, or a C1-C5 alkyleneoxy group; and When substituted, the substituents are each independently halogen, and With respect to the mass of the electrolyte, The content of the compound represented by formula IA is X A When set to %, X A is in the range of 0.12 to 5.1, and The content of the compound represented by the formula IB is X B When set to %, X B is in the range of 0.12 to 5.1.

[0008] According to an embodiment of the present invention, the X A is in the range of 0.52 to 4.2, and B is in the range of 0.52 to 4.2. According to an embodiment of the present invention, the X A is in the range of 1.25 to 3.8, and B is in the range of 1.25 to 3.8.

[0009] The compound represented by formula IA can stabilize the interface between the positive electrode active material and the electrolyte to a certain extent, and the compound represented by formula IA has low viscosity, while the compound represented by formula IB has stronger stability at the interface between the positive electrode active material and the electrolyte. The synergistic effect of the two can improve the high-temperature storage characteristics and safety performance of the electrochemical device while maintaining good low-temperature discharge characteristics.

[0010] According to an embodiment of the present invention, X A and X B is 1.1≦X A+X B Meets ≦9.3. According to an embodiment of the present invention, X B / X A is less than or equal to 2. According to an embodiment of the present invention, X A and X B is 0.5≦X B / X A ≦1.8.

[0011] According to an embodiment of the present invention, the compound of formula IA includes at least one of the following compounds:

[0012] [ka]

[0013] According to an embodiment of the present invention, the compound represented by formula IB includes at least one of the following compounds:

[0014] [ka]

[0015] According to an embodiment of the present invention, the electrolyte further comprises a sulfur-oxygen double bond-containing compound, and the content of the sulfur-oxygen double bond-containing compound is 0.01% to 8% by mass of the electrolyte.

[0016] According to an embodiment of the present invention, the sulfur-oxygen double bond-containing compound includes at least one of the following compounds:

[0017] [ka]

[0018] When the electrolyte further contains a certain amount of a sulfur-oxygen double bond-containing compound, it can effectively improve the stability of the positive electrode interface and the negative electrode interface without significantly affecting the viscosity of the electrolyte and the impedance of the positive electrode interface and the negative electrode interface, and it can further improve the high-temperature storage characteristics of the electrochemical device and maintain good low-temperature discharge characteristics.

[0019] According to an embodiment of the present invention, the electrolyte solution further comprises a compound represented by formula III, and the compound represented by formula III comprises at least one of the following compounds:

[0020] [ka]

[0021] and, The content of the compound represented by formula III is 0.01% to 15% based on the mass of the electrolyte solution. When the electrolyte solution further contains a certain amount of the compound represented by formula III, the negative electrode interface can be sufficiently protected, and the cycle characteristics and high-temperature storage characteristics of the electrochemical device can be further improved. According to an embodiment of the present invention, the electrolyte solution further comprises compound IV, which comprises at least one of the following compounds:

[0022] [ka]

[0023] According to an embodiment of the present invention, the content of the compound IV is 0.01% to 5% based on the mass of the electrolyte solution. The addition of Compound IV to the electrolyte further improves the high temperature storage characteristics of the electrochemical device and also helps maintain good low temperature discharge characteristics. According to an embodiment of the present invention, the electrolyte solution further comprises a phosphorus-containing lithium salt, and the content of the phosphorus-containing lithium salt is 0.01% to 1% based on the mass of the electrolyte solution.

[0024] According to an embodiment of the present invention, the phosphorus-containing lithium salt includes at least one of lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate. According to an embodiment of the present invention, when the content of the phosphorus-containing lithium salt is M% with respect to the mass of the electrolyte solution, M / X A is less than or equal to 1. When the electrolyte solution contains a phosphorus-containing lithium salt, it contributes to further stabilizing the positive electrode active material (e.g., a high-valent transition metal and oxygen atoms) and acts synergistically with the compound represented by formula IA and the compound represented by formula IB, thereby further improving the high-temperature storage characteristics of the electrochemical device and maintaining good low-temperature discharge characteristics.

[0025] According to another aspect of the present invention, there is provided an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte solution as described in the present invention. According to an embodiment of the present invention, the positive electrode includes a positive electrode active material, which includes at least one of an La element, a Y element, and a W element, and satisfies at least one of the following conditions: The mass content of the La element relative to the mass of the positive electrode active material is X La When set to %, X La , 0.01≦X La ≦0.5. The mass content of the Y element relative to the mass of the positive electrode active material is X Y When set to %, X Y , 0.01≦X Y ≦0.5. The mass content of the W element relative to the mass of the positive electrode active material is X W When set to %, X W , 0.01≦X W ≦0.5.

[0026] According to an embodiment of the present invention, the electrochemical device satisfies at least one of the following conditions (a) to (c): (a)X A and X Lais 1≦X A / X La Meets ≦50. (b)X A and X Y is 1≦X A / X Y Meets ≦50. (c)X A and X W is 1≦X A / X W Meets ≦50.

[0027] Introducing La, Y, and / or W into the positive electrode active material can improve the structural stability and reversibility of the positive electrode active material. Furthermore, Y can reduce the charge transfer impedance, thereby further improving the cycle characteristics and safety performance of the electrochemical device.

[0028] According to a further aspect of the present invention, there is provided an electronic device comprising an electrochemical device as described herein. The present invention provides an electrolyte and an electrochemical device, wherein when the electrolyte simultaneously contains a specific amount of the compound represented by formula IA and the compound represented by formula IB, the electrolyte has an appropriate viscosity, and can stabilize the positive electrode active material, protect the positive electrode interface, and inhibit the decomposition of the electrolyte, thereby significantly improving the high-temperature storage properties and safety performance of the electrochemical device, and maintaining good low-temperature discharge properties. Additional aspects and advantages of the present invention will be described in part in the following, illustrated in part, or may be learned by practice of embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Examples of the present invention will be described in detail below, but the examples of the present invention should not be construed as limiting the present invention.

[0030] In specific embodiments and claims, a list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if item A and item B are listed, the phrase "at least one of A and B" means A only, B only, or A and B. In other examples, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0031] The term "hydrocarbon group" includes alkyl groups, alkenyl groups, and alkynyl groups. The term "alkyl group" refers to a straight-chain saturated hydrocarbon structure having 1 to 20 carbon atoms. "Alkyl group" is also contemplated as a branched or cyclic hydrocarbon structure having 3 to 20 carbon atoms. When an alkyl group having a specific number of carbon atoms is specified, all geometric isomers having that number of carbon atoms are contemplated. Thus, for example, "butyl group" is meant to include n-butyl group, sec-butyl group, isobutyl group, tert-butyl group, and cyclobutyl group. "propyl group" includes n-propyl group, isopropyl group, and cyclopropyl group. Illustrative examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, n-pentyl, isopentyl, neopentyl, cyclopentyl, methylcyclopentyl, ethylcyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, octyl, cyclopropyl, cyclobutyl, norbornyl, and the like.

[0032] The term "alkenyl group" refers to a monovalent unsaturated hydrocarbon group that is straight or branched and has at least one, and typically one, two, or three carbon-carbon double bonds. Unless otherwise defined, such alkenyl groups typically contain from 2 to 20 carbon atoms and include (for example) -C 2-4 alkenyl group, -C 2-6 alkenyl groups, and -C 2-10 Representative alkenyl groups include (for example) vinyl, n-propenyl, isopropenyl, n-but-2-enyl, but-3-enyl, n-hex-3-enyl, and the like.

[0033] The term "alkynyl group" refers to a monovalent unsaturated hydrocarbon group that is straight or branched and has at least one, and typically one, two, or three carbon-carbon triple bonds. Unless otherwise defined, such alkynyl groups typically contain from 2 to 20 carbon atoms and include (for example) -C 2-4 an alkynyl group, -C 3-6 Alkynyl groups of -C 3-10 Representative alkynyl groups include (for example) ethynyl, prop-2-ynyl (n-propargyl), n-but-2-ynyl, n-hex-3-ynyl, and the like.

[0034] The term "alkylene group" includes straight-chain and branched-chain alkylene groups. For example, an alkylene group can be C-C 50 Alkylene groups, C1-C 40 Alkylene groups, C1-C 30 Alkylene groups, C1-C 20 Alkylene groups, C1-C 10 It may be an alkylene group of C1-C6, a C2-C6 alkylene group, or a C2-C5 alkylene group.

[0035] The term "alkenylene group" includes straight-chain and branched-chain alkenylene groups. For example, an alkenylene group can be a C-C 50 Alkenylene groups, C2-C 40 Alkenylene groups, C2-C 30Alkenylene groups, C2-C 20 Alkenylene groups, C2-C 10 or a C2-C6 alkenylene group.

[0036] The term "aryl group" refers to a monovalent aromatic hydrocarbon group having a single ring (e.g., a phenyl group) or fused rings. Fused ring systems include fully unsaturated ring systems (e.g., naphthalene) and partially unsaturated ring systems (e.g., 1,2,3,4-tetrahydronaphthalene). Unless otherwise defined, the aryl group typically contains 6 to 26 carbon atoms, such as (e.g.,) -C 6-10 Representative aryl groups include (for example) phenyl, methylphenyl, propylphenyl, isopropylphenyl, benzyl, and naphthalen-1-yl, naphthalen-2-yl groups.

[0037] The term "cycloalkyl group" refers to a non-aromatic monocyclic or polycyclic hydrocarbon group, consisting solely of carbon and hydrogen atoms, which may include fused or bridged ring systems, having from 3 to 15 carbon atoms, preferably from 3 to 10 carbon atoms (C3-C4). 10 and may be saturated or unsaturated. Monocyclic groups include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc. Polycyclic groups include, for example, adamantine, norbornane, decahydronaphthyl, 7,7-dimethyl-bicyclo[2.2.1]heptyl, etc.

[0038] The term "alkoxy" refers to an alkyl group attached to a parent structure through an oxygen atom (-O-alkyl). When a cycloalkyl group is attached to a parent structure through an oxygen atom, the group is also referred to as a "cycloalkoxy group." Examples include methoxy, ethoxy, propoxy, isopropoxy, cyclopropoxy, butoxy, sec-butoxy, tert-butoxy, pentyloxy, cyclohexyloxy, and the like.

[0039] The term "alkyleneoxy" refers to the group -LO-, where L is an alkylene group. For example, the alkyleneoxy group can be an alkyleneoxy group having 1 to 20 carbon atoms, an alkyleneoxy group having 1 to 12 carbon atoms, an alkyleneoxy group having 1 to 5 carbon atoms, an alkyleneoxy group having 5 to 20 carbon atoms, an alkyleneoxy group having 5 to 15 carbon atoms, or an alkyleneoxy group having 5 to 10 carbon atoms. The term "halogen" may be F, Cl, Br or I.

[0040] With technological development and the expansion of application fields, people are placing higher demands on the energy density and environmental durability of electrochemical devices (e.g., lithium-ion batteries). The main method for increasing the energy density of electrochemical devices involves increasing the charging voltage of the electrochemical device. However, high charging voltages not only accelerate the oxidative decomposition of the electrolyte by the positive electrode active material (e.g., high-valent transition metals), but also cause oxygen release from the positive electrode active material, further accelerating the decomposition of the electrolyte. This increases gas generation in electrochemical devices and affects their safety performance and high-temperature storage characteristics. Furthermore, the electrolyte is currently one of the main factors affecting the environmental durability of electrochemical devices. When improving the electrolyte composition, the effect of viscosity must usually be taken into consideration. The viscosity of the electrolyte composition increases at low temperatures, and in some cases even solidification occurs, causing a decrease in its ionic conductivity and thereby deteriorating the low-temperature discharge characteristics of electrochemical devices.

[0041] In order to improve the high-temperature storage characteristics and safety performance of an electrochemical device while maintaining good low-temperature discharge characteristics, the present invention provides an electrolyte solution comprising a compound represented by formula IA and a compound represented by formula IB,

[0042] [ka]

[0043] R 11 is a substituted or unsubstituted C1-C 10alkylene groups, substituted or unsubstituted C5-C 15 or a substituted or unsubstituted C6-C 15 and the aryl group is selected from the group consisting of R 12 , R 13 and R 14 are each independently selected from a single bond, a C1-C5 alkylene group, or a C1-C5 alkyleneoxy group; and When substituted, the substituents are each independently halogen, and With respect to the mass of the electrolyte, The content of the compound represented by formula IA is X A When set to %, X A is in the range of 0.12 to 5.1, and The content of the compound represented by the formula IB is X B When set to %, X B is in the range of 0.12 to 5.1.

[0044] The compounds represented by formulas IA, IB, and IC are all polynitrile compounds. The compound represented by formula IA can stabilize the interface between the positive electrode active material and the electrolyte to a certain extent, and the compound represented by formula IA has a low viscosity. The compound represented by formula IB has stronger stability at the interface between the positive electrode active material and the electrolyte, but the compound represented by formula IB has a high viscosity. If the content of the compounds represented by formulas IA and IB in the electrolyte is too low, the interface between the positive electrode active material and the electrolyte cannot be sufficiently stabilized, making it difficult to achieve effective results. As the content of the compounds represented by formulas IA and IB in the electrolyte increases, the high-temperature storage characteristics and safety performance of the electrochemical device are improved, but further increase in the content of the compounds represented by formulas IA and IB in the electrolyte is difficult to further improve. Excessive amounts of the compounds represented by formulas IA and IB increase the viscosity of the electrolyte, thereby adversely affecting the low-temperature discharge characteristics of the electrochemical device. When the electrolyte solution simultaneously contains a specific amount of the compound represented by formula IA and the compound represented by formula IB, the electrolyte solution has an appropriate viscosity, and can stabilize the positive electrode active material, protect the positive electrode interface, and inhibit decomposition of the electrolyte solution, thereby significantly improving the high-temperature storage characteristics and safety performance of the electrochemical device, and maintaining good low-temperature discharge characteristics.

[0045] In some embodiments, X A In some embodiments, X is in the range of 0.15 to 5.0. A In some embodiments, X is in the range of 0.2 to 4.8. A In some embodiments, X is in the range of 0.5 to 4.5. A In some embodiments, X is in the range of 0.52 to 4.2. A In some embodiments, X is in the range of 1.0 to 4.0. A In some embodiments, X is in the range of 1.25 to 3.8. AIn some embodiments, X is in the range of 1.5 to 3.5. A In some embodiments, X is in the range of 2.0 to 3.0. A is 0.12, 0.15, 0.2, 0.5, 0.52, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 3.8, 4.0, 4.2, 4.5, 5.0, or 5.1, or is within a range consisting of any two of the above values. When the content of the compound represented by formula IA in the electrolyte is within the above range, it is helpful in further improving the high-temperature storage characteristics and safety performance of the electrochemical device and maintaining good low-temperature discharge characteristics.

[0046] In some embodiments, X B In some embodiments, X is in the range of 0.15 to 5.0. B In some embodiments, X is in the range of 0.2 to 4.8. B In some embodiments, X is in the range of 0.5 to 4.5. B In some embodiments, X is in the range of 0.52 to 4.2. B In some embodiments, X is in the range of 1.0 to 4.0. B In some embodiments, X is in the range of 1.25 to 3.8. B In some embodiments, X is in the range of 1.5 to 3.5. B In some embodiments, X is in the range of 2.0 to 3.0. B is 0.12, 0.15, 0.2, 0.5, 0.52, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 3.8, 4.0, 4.2, 4.5, 5.0, or 5.1, or is within a range consisting of any two of the above values. When the content of the compound represented by formula IB in the electrolyte is within the above range, it is helpful in further improving the high-temperature storage characteristics and safety performance of the electrochemical device and maintaining good low-temperature discharge characteristics.

[0047] In some embodiments, X A and X B is 1.1≦X A +X BIn some embodiments, X satisfies ≦9.3. A and X B is 1.2≦X A +X B In some embodiments, X satisfies ≦9.0. A and X B is 1.5≦X A +X B In some embodiments, X satisfies ≦8.0. A and X B is 1.9≦X A +X B In some embodiments, X satisfies ≦7.8. A and X B , 2.0≦X A +X B In some embodiments, X satisfies ≦7.0. A and X B , 2.6≦X A +X B In some embodiments, 3.0≦X A +X B In some embodiments, X satisfies ≦5.0. A +X B is 1.1, 1.5, 1.9, 2.0, 2.5, 2.6, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.4, 6.5, 7.0, 7.5, 7.8, 8.0, 8.5, 9.0, or 9.3, or is within a range consisting of any two of the above numerical values. The total content of the compound represented by formula IA and the compound represented by formula IB in the electrolyte (X A +X B ) within the above range further improves the high-temperature storage characteristics and safety performance of the electrochemical device, and also helps to maintain good low-temperature discharge characteristics.

[0048] In some embodiments, X B / X A is less than or equal to 2. In some embodiments, X A and X B is 0.5≦X B / X A In some embodiments, X satisfies ≦1.8. A and XB is 1.0≦X B / X A In some embodiments, X satisfies ≦1.5. B / X A is 0.01, 0.05, 0.1, 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, or 2.0, or is within a range consisting of any two of the above numerical values. The content ratio of the compound represented by formula IB to the compound represented by formula IA in the electrolyte (X B / X A ) within the above range further improves the high-temperature storage characteristics and safety performance of the electrochemical device, and also helps to maintain good low-temperature discharge characteristics.

[0049] In some embodiments, the compound of formula IA includes at least one of the following compounds:

[0050] [ka]

[0051] In some embodiments, the compound of formula IB includes at least one of the following compounds:

[0052] [ka]

[0053] In some embodiments, the electrolyte further comprises a sulfur-oxygen double bond-containing compound, and the content of the sulfur-oxygen double bond-containing compound is 0.01% to 8% by mass of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 0.05% to 7% by mass of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 0.1% to 6% by mass of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 0.5% to 5% by mass of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 1% to 4% by mass of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 2% to 3% by mass of the electrolyte. In some embodiments, the content of the sulfur-oxygen double bond-containing compound is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8% by weight of the electrolyte, or a range consisting of any two of the foregoing values.

[0054] In some embodiments, the sulfur-oxygen double bond-containing compound comprises at least one of a compound represented by formula II-A and a compound represented by formula II-B,

[0055] [ka]

[0056] X and Y are each independently [ka]

[0057] is selected from at least one of

[0058] [ka]

[0059] represents the bonding site with the adjacent atom, R 21 and R 22 are each independently a substituted or unsubstituted C1-C5 alkyl group or a substituted or unsubstituted C2-C 10 and the alkenyl group is selected from the group consisting of R 23 , R 24 , R 25 and R 26 are each independently a substituted or unsubstituted C1-C5 alkylene group or a substituted or unsubstituted C2-C 10 and If substituted, the substituents are each independently halogen or C6-C 10 is an aryl group of the formula:

[0060] In some embodiments, the sulfur-oxygen double bond-containing compound includes at least one of the following compounds:

[0061] [ka]

[0062] On the one hand, sulfur-oxygen double bond-containing compounds have strong antioxidant properties and can improve the stability of the positive electrode interface. On the other hand, sulfur-oxygen double bond-containing compounds are reduced on the negative electrode surface to form a protective film, which inhibits the decomposition of the electrolyte and further enhances the stability of the negative electrode interface. When the electrolyte further contains a certain amount of sulfur-oxygen double bond-containing compounds, not only can the stability of the positive electrode interface and the negative electrode interface be effectively improved, but also the viscosity of the electrolyte and the impedance of the positive electrode interface and the negative electrode interface are not significantly affected, thereby further improving the high-temperature storage characteristics of the electrochemical device and maintaining good low-temperature discharge characteristics.

[0063] In some embodiments, the electrolyte further comprises a compound represented by Formula III:

[0064] [ka]

[0065] R 31 is selected from a substituted or unsubstituted C1-C6 alkylene group or a substituted or unsubstituted C2-C6 alkenylene group; If substituted, the substituents are each independently selected from halogen, a C1-C6 alkyl group, or a C2-C6 alkenyl group; and In some embodiments, the compound of Formula III includes at least one of the following compounds:

[0066] [ka]

[0067] and, The content of the compound represented by formula III is 0.01% to 15% based on the mass of the electrolyte solution.

[0068] In some embodiments, the content of the compound represented by Formula III relative to the mass of the electrolyte solution is 0.05% to 12%. In some embodiments, the content of the compound represented by Formula III relative to the mass of the electrolyte solution is 0.1% to 10%. In some embodiments, the content of the compound represented by Formula III relative to the mass of the electrolyte solution is 0.5% to 8%. In some embodiments, the content of the compound represented by Formula III relative to the mass of the electrolyte solution is 1% to 5%. In some embodiments, the content of the compound represented by Formula III relative to the mass of the electrolyte solution is 2% to 4%. In some embodiments, the content of the compound represented by Formula III relative to the mass of the electrolyte solution is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or a range consisting of any two of the foregoing values.

[0069] The compound represented by formula III can help enhance the film formation stability of the negative electrode solid electrolyte interfacial film (SEI), increase the flexibility of the SEI film, strengthen the protective effect on the negative electrode active material, and reduce the probability of interfacial contact between the negative electrode active material and the electrolyte, thereby reducing the impedance during cycling of the electrochemical device. When the electrolyte further contains a certain amount of the compound represented by formula III, it can fully protect the negative electrode interface, and further improve the cycling characteristics and high-temperature storage characteristics of the electrochemical device.

[0070] In some embodiments, the electrolyte further comprises compound IV, wherein compound IV comprises at least one of the following compounds:

[0071] [ka]

[0072] Compound IV may be a short-chain hydrocarbon compound having two cyano groups (i.e., a hydrocarbon chain having fewer than five carbon atoms, excluding the carbon atoms in the cyano groups), a compound having a P=O bond and at least three cyano groups, or a compound having an ether bond and at least four cyano groups. The short-chain hydrocarbon compound having two cyano groups can act synergistically with the compound represented by formula IA to further protect the positive electrode interface. Compounds having a P=O bond and at least three cyano groups, and compounds having an ether bond and at least four cyano groups, can enhance protection of the positive electrode interface due to the increased number of cyano groups. Therefore, adding compound IV to the electrolyte can further improve the high-temperature storage characteristics of electrochemical devices while maintaining good low-temperature discharge characteristics.

[0073] In some embodiments, the content of Compound IV is 0.01% to 5% by weight of the electrolyte solution. In some embodiments, the content of Compound IV is 0.05% to 4% by weight of the electrolyte solution. In some embodiments, the content of Compound IV is 0.1% to 3% by weight of the electrolyte solution. In some embodiments, the content of Compound IV is 0.5% to 2% by weight of the electrolyte solution. In some embodiments, the content of Compound IV is 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5% by weight of the electrolyte solution, or within a range consisting of any two of the foregoing values. When the content of Compound IV in the electrolyte solution is within the above range, the high-temperature storage characteristics of the electrochemical device can be further improved while maintaining good low-temperature discharge characteristics.

[0074] In some embodiments, the electrolyte further comprises a phosphorus-containing lithium salt, and the content of the phosphorus-containing lithium salt is 0.01% to 1% by weight of the electrolyte. In some embodiments, the content of the phosphorus-containing lithium salt is 0.05% to 0.8% by weight of the electrolyte. In some embodiments, the content of the phosphorus-containing lithium salt is 0.1% to 0.6% by weight of the electrolyte. In some embodiments, the content of the phosphorus-containing lithium salt is 0.2% to 0.5% by weight of the electrolyte. In some embodiments, the content of the phosphorus-containing lithium salt is 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% by weight of the electrolyte, or a range consisting of any two of the foregoing values.

[0075] In some embodiments, the phosphorus-containing lithium salt comprises at least one of lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0076] The phosphorus-containing lithium salt contributes to further stabilization of the positive electrode active material (e.g., high-valent transition metal and oxygen atom) and can act synergistically with the compound represented by formula IA and the compound represented by formula IB. When the electrolyte contains a certain amount of phosphorus-containing lithium salt, the high-temperature storage characteristics of the electrochemical device can be further improved while maintaining good low-temperature discharge characteristics.

[0077] In some embodiments, when the content of the phosphorus-containing lithium salt is M% relative to the mass of the electrolyte, M / X is 1 or less. In some embodiments, M / X is 0.01 to 0.8. In some embodiments, M / X is 0.05 to 0.6. In some embodiments, M / X is 0.1 to 0.5. In some embodiments, M / X is 0.2 to 0.4. In some embodiments, M / X is 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, or is within a range consisting of any two of the foregoing numbers. When M / X is within the above range, the high-temperature storage characteristics of the electrochemical device are further improved, while maintaining good low-temperature discharge characteristics.

[0078] In some embodiments, the electrolyte solution may further include other non-aqueous organic solvents and electrolyte salts. The non-aqueous organic solvents may include at least one of carbonate esters, carboxylic acid esters, ethers, and other aprotic solvents. Examples of carbonate ester solvents include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, bis(2,2,2-trifluoroethyl)carbonate, etc. Examples of carboxylic acid ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, γ-butyrolactone, 2,2-difluoroethyl acetate, valerolactone, butyrolactone, 2-fluoroethyl acetate, 2,2-difluoroethyl acetate, trifluoroethyl acetate, and 2,2,3,3,3-pentafluoropropyl. Examples of the ether solvent include ethyl propionate, methyl 2,2,3,3,4,4,4,4-heptafluorobutyrate, methyl 4,4,4-trifluoro-3-(trifluoromethyl)butyrate, ethyl 2,2,3,3,4,4,5,5,5,5-nonafluorovalerate, methyl 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoate, ethyl 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanoate, etc. Examples of the ether solvent include ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, bis(2,2,2-trifluoroethyl)ether, etc.

[0079] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt and an inorganic lithium salt, ie, lithium hexafluorophosphate LiPF, lithium bis(trifluoromethanesulfonyl)imide LiN(CFSO) (abbreviated as LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SOF)) (abbreviated as LiFSI), lithium hexafluorocesium oxide (LiCsF), lithium perchlorate LiClO, and lithium trifluoromethanesulfonate LiCFSO.

[0080] In some embodiments, the content of the electrolyte salt is 10% to 15% by weight of the electrolyte solution. In some embodiments, the mass percentage of the electrolyte salt is 12% to 15% by weight of the electrolyte solution. When the content of the electrolyte salt is within the above ranges, the electrolyte solution has appropriate ionic conductivity and viscosity, and the electrochemical device can have good rate and cycle characteristics.

[0081] The present invention further provides an electrochemical device, comprising an electrode assembly and an electrolyte, the electrode assembly comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, in some embodiments, the electrolyte is an electrolyte described in the present invention.

[0082] In some embodiments, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer may be disposed on one or both sides of the negative electrode current collector. In some embodiments, the negative electrode current collector may be made of at least one of copper foil, aluminum foil, nickel foil, and a carbon-based current collector. In some embodiments, the thickness of the negative electrode current collector may be 1 μm to 200 μm. In some embodiments, the negative electrode active material layer may be applied to only a partial region of the negative electrode current collector. In some embodiments, the thickness of the negative electrode active material layer may be 10 μm to 500 μm. It should be understood that this is merely an example, and other appropriate thicknesses may be employed.

[0083] In some embodiments, the negative electrode active material layer includes a negative electrode active material. In some embodiments, the negative electrode active material in the negative electrode active material layer includes at least one of lithium metal, natural graphite, artificial graphite, and a silicon-based material. In some embodiments, the silicon-based material includes at least one of silicon, a silicon-oxygen compound, a silicon-carbon compound, and a silicon alloy.

[0084] In some embodiments, the negative electrode active material layer may further include a conductive agent and / or a binder. The conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers, and carbon nanowires. In some embodiments, the binder in the negative electrode active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyacrylate, polyacrylic acid ester, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, and polyfluorene. It should be understood that the above-disclosed materials are merely exemplary, and any other suitable materials may be employed in the negative electrode active material layer. In some embodiments, the mass ratio of the negative electrode active material, conductive agent, and binder in the negative electrode active material layer may be (80-99):(0.5-10):(0.5-10). It should be understood that this is merely an example and is not intended to limit the invention.

[0085] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer may be disposed on one or both sides of the positive electrode current collector. In some embodiments, the positive electrode current collector may be aluminum foil, or, of course, other positive electrode current collectors commonly used in the art may be used. In some embodiments, the thickness of the positive electrode current collector may be 1 μm to 200 μm. In some embodiments, the positive electrode active material layer may be applied to only a portion of the positive electrode current collector. In some embodiments, the thickness of the positive electrode active material layer may be 10 μm to 500 μm. It should be understood that this is merely an example, and other appropriate thicknesses may be employed.

[0086] In some embodiments, the positive electrode active material layer includes a positive electrode active material. In some embodiments, the positive electrode active material layer includes a positive electrode active material. In some embodiments, the positive electrode active material is LiCoO2, LiNiO2, LiMn2O4, LiCo 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M y O4, LiNi x Co y Mn z M 1-x-y-z O2, wherein M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, La, Y, W, and Ti, and x, y, and z satisfy 0≦y≦1, 0≦x≦1, 0≦z≦1, and x+y+z≦1. In some embodiments, the active cathode material may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel manganese oxide, and the active cathode material may be doped and / or coated.

[0087] In some embodiments, the positive electrode active material contains at least one of La, Y, and W elements, and satisfies at least one of the following conditions: The mass content of the La element relative to the mass of the positive electrode active material is X La When set to %, X La , 0.01≦X La ≦0.5. The mass content of the Y element relative to the mass of the positive electrode active material is X Y When set to %, X Y , 0.01≦X Y ≦0.5. The mass content of the W element relative to the mass of the positive electrode active material is X W When set to %, X W , 0.01≦X W ≦0.5.

[0088] In some embodiments, X La , 0.01≦X La In some embodiments, X satisfies ≦0.5. La , 0.05≦X La In some embodiments, X satisfies ≦0.4. La , 0.1≦X La In some embodiments, X satisfies ≦0.3. La is 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or is within a range consisting of any two of the foregoing numbers.

[0089] In some embodiments, X Y , 0.01≦X Y In some embodiments, X satisfies ≦0.5. Y , 0.05≦X Y In some embodiments, X satisfies ≦0.4. Y , 0.1≦X Y In some embodiments, X satisfies ≦0.3. Y is 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or is within a range consisting of any two of the foregoing numbers.

[0090] In some embodiments, X W , 0.01≦X W In some embodiments, X satisfies ≦0.5. W , 0.05≦X W In some embodiments, X satisfies ≦0.4. W , 0.1≦X W In some embodiments, X satisfies ≦0.3. Y is 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or is within a range consisting of any two of the foregoing numbers.

[0091] The introduction of La, Y, and / or W into the positive electrode active material can improve the structural stability and reversibility of the positive electrode active material. Furthermore, Y can reduce the charge transfer impedance, thereby improving the cycle characteristics and safety performance of the electrochemical device.

[0092] In some embodiments, the electrochemical device satisfies at least one of the following conditions (a) to (c): (a)X A and X La is 1≦X A / X La Meets ≦50. (b)X A and X Y is 1≦X A / X Y Meets ≦50. (c)X A and X W is 1≦X A / X W Meets ≦50.

[0093] In some embodiments, X A and X La , 5≦X A / X La In some embodiments, X satisfies ≦40. A and X La , 10≦X A / XLa In some embodiments, X A and X La , 15≦X A / X La Satisfy ≦20.

[0094] In some embodiments, X A and X Y , 5≦X A / X Y In some embodiments, X satisfies ≦40. A and X Y , 10≦X A / X Y In some embodiments, X A and X Y , 15≦X A / X Y Satisfy ≦20.

[0095] In some embodiments, X A and X W , 5≦X A / X W In some embodiments, X satisfies ≦40. A and X W , 10≦X A / X W In some embodiments, X A and X W , 15≦X A / X W Satisfy ≦20.

[0096] When the content of the compound represented by formula IA in the electrolyte and the content of La, Y or W element in the positive electrode active material satisfy the above-mentioned relationship, it helps to further improve the cycle characteristics and safety performance of the electrochemical device.

[0097] In some embodiments, the positive electrode active material layer further includes a binder and a conductive agent. In some embodiments, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. In some embodiments, the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, acetylene black, ketjen black, flake graphite, graphene, carbon nanotubes, and carbon fiber. In some embodiments, the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode active material layer may be (70-98):(1-15):(1-15). It should be understood that the above description is merely an example, and the positive electrode active material layer may employ any other suitable material, thickness, and mass ratio.

[0098] In some embodiments, the separator comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, and aramid. For example, the polyethylene may comprise at least one selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene are effective in preventing short circuits and can improve battery stability through their shutdown effect. In some embodiments, the thickness of the separator is within the range of approximately 3 μm to 500 μm.

[0099] In some embodiments, the separator can further include a porous layer on a surface thereof, the porous layer being provided on at least one surface of the separator, the porous layer including at least one of inorganic particles and a binder, the inorganic particles being selected from at least one of aluminum oxide (Al2O3), silicon oxide (SiO2), magnesium oxide (MgO), titanium oxide (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium oxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (YO3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. In some embodiments, the pores of the separator have a diameter in the range of about 0.01 μm to 1 μm. The binder for the porous layer is selected from at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The porous layer on the surface of the separator improves the separator's heat resistance, oxidation resistance, and electrolyte permeability, and can enhance adhesion between the separator pole pieces.

[0100] In some embodiments of the present invention, the electrode assembly of the electrochemical device is a wound electrode assembly or a stacked electrode assembly. In some embodiments, the electrochemical device is a lithium ion battery, although the present invention is not limited thereto.

[0101] In some embodiments of the present invention, taking a lithium ion battery as an example, a positive electrode piece, a separator, and a negative electrode piece are sequentially wound or stacked to form an electrode assembly, which is then sealed in, for example, an aluminum plastic film case, and an electrolyte is injected, formed, and sealed to form a lithium ion battery, and the characteristics of the prepared lithium ion battery are then measured.

[0102] Those skilled in the art should understand that the above-described methods for preparing electrochemical devices (e.g., lithium ion batteries) are merely examples, and other methods commonly used in the art may be used without departing from the teachings of the present invention.

[0103] The present invention further provides an electronic device comprising the electrochemical device described in the present invention. The electronic device of the present invention is not particularly limited and can be used in any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, a laptop computer, a pen-based computer, a mobile computer, an electronic book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc player, a walkie-talkie, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large-scale household battery, and a lithium-ion capacitor.

[0104] Hereinafter, the preparation of a lithium ion battery will be described with reference to specific examples, taking a lithium ion battery as an example. Those skilled in the art should understand that the preparation method described in the present invention is merely exemplary, and any other suitable preparation method is also within the scope of the present invention.

[0105] (Example) The following describes performance evaluation of examples of the lithium ion battery according to the present invention and comparative examples.

[0106] 1. Preparation of lithium-ion batteries 1. Preparation of the positive electrode According to the settings of the examples or comparative examples, lithium cobalt oxide (LiCoO2) or lithium cobalt oxide containing a doping element, conductive carbon black, and polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) in a weight ratio of 97.9:0.9:1.2 (lithium cobalt oxide:carbon black:PVDF), and the mixture was thoroughly stirred to form a uniform mixture, forming a positive electrode slurry. A 13 μm aluminum foil was used as the positive electrode current collector. The positive electrode slurry was applied to the positive electrode current collector, dried, cold pressed, and slit to obtain a positive electrode. The compressed density of the positive electrode was 4.15 g / cm. 3 It was.

[0107] 2. Preparation of the negative electrode Artificial graphite, styrene butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) were dissolved in deionized water in a weight ratio of 97.4:1.4:1.2 (artificial graphite:SBR:CMC) to form a negative electrode slurry. A 10 μm thick copper foil was used as the negative electrode current collector. The negative electrode slurry was applied to the negative electrode current collector, dried, cold pressed, and slit to obtain a negative electrode. The compressed density of the negative electrode was 1.8 g / cm. 3 It was.

[0108] 3. Preparation of separator The separator substrate was polyethylene (PE) with a thickness of 5 μm. A 2 μm thick alumina ceramic layer was applied to each side of the separator substrate, and then 2.5 mg of polyvinylidene fluoride (PVDF) was applied to each side of the separator with one ceramic layer applied, followed by drying to obtain a separator.

[0109] 4. Preparation of electrolyte In an environment where the water content was less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were uniformly mixed in a mass ratio of EC:PC:DEC of 2:1:7, and the electrolyte salt LiPF6 was dissolved in the non-aqueous solvent and mixed uniformly to form a base electrolyte solution, the mass percentage of LiPF6 being 12.5%.

[0110] According to the settings of each of the following Examples or Comparative Examples, a certain amount of additive was added to the base electrolyte to obtain the electrolyte of each of the Examples or Comparative Examples. The additives used in each example or comparative example are as shown in the table below.

[0111] [Table 1]

[0112] 5. Preparation of Lithium-ion Battery The positive electrode, separator, and negative electrode were stacked in this order, with a separator positioned between the positive and negative electrodes to act as an insulator, and then wound to obtain an electrode assembly. The electrode assembly was placed in an exterior aluminum plastic film, and after removing moisture at 80°C, the above electrolyte solution was poured in, sealed, and subjected to processes such as chemical formation, degassing, and trimming to obtain a lithium-ion battery.

[0113] 2.Measurement method 1. Measurement method for high-temperature storage characteristics of lithium-ion batteries At 25°C, the lithium-ion battery was charged at a constant current of 0.5C up to 4.55V, then charged at a constant voltage until the current reached 0.05C. The thickness of the lithium-ion battery was measured and denoted as d0. The lithium-ion battery was then placed in a 60°C oven for 20 days, and the thickness was measured and denoted as d. The thickness expansion rate and voltage drop of the lithium-ion battery during high-temperature storage were calculated using the following equations. Thickness expansion rate when stored at high temperature = (d-d0) / d0 x 100%. If the thickness expansion rate of the lithium-ion battery exceeds 50%, the measurement is stopped.

[0114] 2. Lithium-ion battery safety performance testing method Under the condition of 25°C, the lithium-ion battery was charged to 4.55V at a constant current of 0.5C, and then charged at a constant voltage until the current reached 0.02C. The sample was then placed vertically in a hot box and heated to 200±2°C at a heating rate of 2°C / min and held for 0 minutes. The time until the lithium-ion battery ignited or exploded was recorded and considered to be the failure time.

[0115] 3. Measurement method for low-temperature discharge characteristics of lithium-ion batteries At 25°C, the lithium-ion battery was charged to 4.5V at 0.5C and then constant-voltage charged to 0.025C at 4.5V. At 25°C, it was discharged to 3.0V at 0.2C, and the discharge capacity was measured as C0. Then, at 25°C, the lithium-ion battery was charged to 4.5V at 0.5C and then constant-voltage charged to 0.025C at 4.5V. At -20°C, it was discharged to 3.0V at 0.2C, and the discharge capacity was measured as C1. The low-temperature discharge capacity retention of the lithium-ion battery was calculated using the following formula. Low temperature discharge capacity maintenance rate = C1 / C0×100%.

[0116] 4. Measurement method for cycle characteristics of lithium-ion batteries At 25°C, the lithium-ion battery was charged to 4.5 V at 0.7 C, then constant-voltage charged to 0.05 C at 4.5 V. It was then discharged to 3.0 V at 0.7 C, and cycled 800 times with a 0.7 C charge and 1 C discharge cycle. The discharge capacities at the third and 800th cycles were measured. The cycle capacity retention of the lithium-ion battery was calculated using the following formula: Cycle capacity retention rate = discharge capacity at the 800th cycle / discharge capacity at the 3rd cycle × 100%.

[0117] 3. Measurement results Table 1 shows the effects of the compounds represented by formula IA and formula IB in the electrolyte and their contents on the high-temperature storage characteristics, low-temperature discharge characteristics, and safety performance of the lithium-ion battery.

[0118] [Table 2]

[0119] The electrolyte of Comparative Example 1 contains only the compound represented by formula IA; Comparative Example 2 contains only the compound represented by formula IB; Comparative Example 3 contains a short-chain dinitrile compound (other than the compound represented by formula IA) and no compound represented by formula IB; and Comparative Example 4 contains a short-chain dinitrile compound (other than the compound represented by formula IA) and a compound represented by formula IB. Comparative Examples 5 and 6 contain both the compound represented by formula IA and the compound represented by formula IB, but the content of the compound represented by formula IA or the compound represented by formula IB is too low. The lithium-ion batteries of Comparative Examples 1-6 have good low-temperature discharge capacity retention, but their thickness expansion rate during high-temperature storage is high and their hot box failure time is short, making them unable to meet usage requirements.

[0120] As shown in Examples 1-20, when the electrolyte solution simultaneously contains 0.12% to 5.1% of the compound represented by formula IA and 0.12% to 5.1% of the compound represented by formula IB, the lithium ion battery still has good low-temperature discharge capacity retention, but also has a significantly reduced thickness expansion rate during high-temperature storage and a significantly increased hot box failure time. That is, the lithium ion battery has significantly improved high-temperature storage characteristics and safety performance, while maintaining good low-temperature discharge characteristics.

[0121] When the content of the compound represented by formula IA in the electrolyte is within the range of 0.52% to 4.2%, and the content of the compound represented by formula IB is within the range of 0.52% to 4.2%, the high-temperature storage characteristics and safety performance of the lithium-ion battery can be further improved, and the low-temperature discharge characteristics can be maintained.

[0122] When the total content of the compound represented by formula IA and the compound represented by formula IB in the electrolyte is within the range of 1.1% to 9.5%, particularly within the range of 1.9% to 7.8% or within the range of 2.6% to 6.4%, the high-temperature storage characteristics and safety performance of the lithium-ion battery can be further improved, and good low-temperature discharge characteristics can be maintained.

[0123] The content of the compound represented by formula IB in the electrolyte (XB %) and the content of the compound represented by formula IA (X A % is X B / X A When the ratio satisfies ≦2, especially when it is in the range of 0.5 to 1.8, it is helpful in further improving the high-temperature storage characteristics and safety performance of the lithium-ion battery and maintaining good low-temperature discharge characteristics.

[0124] Table 2 shows the sulfur-oxygen double bond-containing compound, compound IV, and phosphorus-containing lithium salt in the electrolyte, and the effects of their contents on the high-temperature storage characteristics and low-temperature discharge performance of the lithium-ion battery.

[0125] [Table 3]

[0126] The high-temperature storage characteristics of lithium-ion batteries can be further improved while maintaining good low-temperature discharge characteristics by adding 0.01% to 8% of a sulfur-oxygen double bond-containing compound, 0.01% to 15% of compound IV, and / or 0.01% to 1% of a phosphorus-containing lithium salt to the electrolyte, in addition to simultaneously containing 0.12% to 5.1% of the compound represented by formula IA and 0.12% to 5.1% of the compound represented by formula IB. The cycle characteristics of lithium-ion batteries can be further improved by adding 0.01% to 15% of a compound represented by formula III to the electrolyte, in addition to simultaneously containing 0.12% to 5.1% of the compound represented by formula IA and 0.12% to 5.1% of the compound represented by formula IB.

[0127] When the content of compound IV in the electrolyte solution is within the range of 0.01% to 5%, the high-temperature storage characteristics of the lithium-ion battery can be further improved, and good low-temperature discharge characteristics can be maintained.

[0128] The content of the phosphorus-containing lithium salt in the electrolyte (M%) and the content of the compound represented by formula IA (X A %) is M / X AWhen the condition ≦1 is satisfied, the high-temperature storage characteristics of the lithium ion battery can be further improved and good low-temperature discharge characteristics can be maintained.

[0129] Table 3 shows the influence of the elements doped in the positive electrode active material and their contents on the cycle characteristics and safety performance of the lithium-ion battery.

[0130] [Table 4]

[0131] The electrolyte solution contains 0.12% to 5.1% of the compound represented by formula IA and 0.12% to 5.1% of the compound represented by formula IB simultaneously, and also uses a positive electrode active material containing 0.01% to 0.5% of La, 0.01% to 0.5% of Y, and / or 0.01% to 0.5% of W, which helps to further improve the cycle capacity retention rate of the lithium-ion battery and reduce the expansion rate during high-temperature storage.

[0132] The content of the compound represented by formula IA in the electrolyte (X A ) and the content of La in the positive electrode active material (X La ), Y element content (X Y ) or W element content (X W ) ratio is 1≦X A / X La ≦50, 1≦X A / X Y ≦50 or 1≦X A / X W If the ratio satisfies ≦50, the cycle capacity retention rate of the lithium ion battery is further improved and the expansion rate during high temperature storage is reduced.

[0133] References throughout the specification to "in some embodiments," "in one embodiment," "another example," "example," "embodiment," or "some examples" mean that at least one embodiment or example of the present invention includes the particular feature, structure, material, or characteristic described in that embodiment or example. Thus, the appearances of, for example, "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "example" in various places throughout the specification do not necessarily refer to the same embodiment or example of the present invention. Furthermore, particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

[0134] While illustrative embodiments have been disclosed and described, those skilled in the art should understand that the above embodiments are not to be construed as limiting the present invention, and that modifications, substitutions, and alterations can be made to the embodiments without departing from the spirit, principle, and scope of the present invention.

Claims

1. An electrolyte solution comprising a compound represented by formula IA and a compound represented by formula IB, 【Chemistry 1】 R １１ is a substituted or unsubstituted C １ -C １０ an alkylene group of the formula ５ -C １５ or a substituted or unsubstituted C ６ -C １５ and the aryl group is selected from the group consisting of R １２ , R １３ and R １４ are each independently a single bond, C １ -C ５ or an alkylene group of C １ -C ５ and if substituted, the substituents are each independently halogen; and With respect to the mass of the electrolyte, The content of the compound represented by formula IA is X Ａ When set to %, X Ａ is in the range of 0.12 to 5.1, and The content of the compound represented by formula I-B is X Ｂ When set to %, X Ｂ is in the range of 0.12 to 5.

1.

2. The X Ａ is in the range of 0.52 to 4.2, and Ｂ The electrolyte solution according to claim 1, wherein is in the range of 0.52 to 4.

2.

3. The X Ａ is in the range of 1.25 to 3.8, and Ｂ The electrolyte solution according to claim 1, wherein the σ is in the range of 1.25 to 3.

8.

4. The X Ａ and the X Ｂ is 1.1≦X Ａ +X Ｂ 2. The electrolyte solution according to claim 1, wherein the electrolyte satisfies the following conditions: ≦9.

3.

5. X Ｂ / X Ａ The electrolyte solution according to claim 1 , wherein is 2 or less.

6. The X Ａ and the X Ｂ is 0.5≦X Ｂ / X Ａ 2. The electrolyte solution according to claim 1, wherein the pH satisfies ≦1.

8.

7. The compound represented by formula IA is the following compound: 【Chemistry 2】 The electrolyte solution according to claim 1, comprising at least one of:

8. The compound represented by formula I-B is the following compound: 【Transformation 3】 The electrolyte solution according to claim 1, comprising at least one of:

9. 2. The electrolyte solution according to claim 1, further comprising a sulfur-oxygen double bond-containing compound, and the content of the sulfur-oxygen double bond-containing compound relative to the mass of the electrolyte solution is 0.01% to 8%.

10. The sulfur-oxygen double bond-containing compound is the following compound: 【Chemistry 4】 The electrolyte solution according to claim 9, comprising at least one of:

11. The electrolyte further comprises a compound represented by Formula III, The compound represented by formula III is the following compound: 【Transformation 5】 and 2. The electrolyte solution according to claim 1, wherein the content of the compound represented by formula III is 0.01% to 15% by mass of the electrolyte solution.

12. the electrolyte further comprises Compound IV; Compound IV is the following compound: 【Transformation 6】 The electrolyte solution according to claim 1, comprising at least one of:

13. 13. The electrolyte solution according to claim 12, wherein the content of the compound IV is 0.01% to 5% by mass of the electrolyte solution.

14. 2. The electrolyte solution according to claim 1, further comprising a phosphorus-containing lithium salt, and the content of the phosphorus-containing lithium salt is 0.01% to 1% by mass of the electrolyte solution.

15. 15. The electrolyte of claim 14, wherein the phosphorus-containing lithium salt comprises at least one of lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

16. When the content of the phosphorus-containing lithium salt is M % with respect to the mass of the electrolyte solution, M / X Ａ The electrolyte solution of claim 14, wherein is 1 or less.

17. An electrochemical device comprising a positive electrode, a negative electrode, a separator and the electrolyte solution according to any one of claims 1 to 18.

18. The positive electrode includes a positive electrode active material, and the positive electrode active material includes at least one of an La element, a Y element, and a W element, and The positive electrode active material is The mass content of the La element relative to the mass of the positive electrode active material is X Ｌａ When set to %, X Ｌａ is 0.01≦X Ｌａ ≦0.5; The mass content of the Y element relative to the mass of the positive electrode active material is X Ｙ When set to %, X Ｙ is 0.01≦X Ｙ ≦0.5; The mass content of the W element relative to the mass of the positive electrode active material is X Ｗ When set to %, X Ｗ is 0.01≦X Ｗ ≦0.5; 18. The electrochemical device of claim 17, wherein at least one of the following is satisfied:

19. The electrochemical device comprises: (a) X Ａ and X Ｌａ is 1≦X Ａ / X Ｌａ ≦50; (b) X Ａ and X Ｙ is 1≦X Ａ / X Ｙ ≦50; (c) X Ａ and X Ｗ is 1≦X Ａ / X Ｗ ≦50; 20. The electrochemical device of claim 18, wherein at least one of the following is satisfied:

20. An electronic device comprising the electrochemical device according to any one of claims 17 to 19.

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