CN112803068B - Electrolyte solution, electrochemical device, and electronic device - Google Patents

Electrolyte solution, electrochemical device, and electronic device Download PDF

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CN112803068B
CN112803068B CN202011612907.5A CN202011612907A CN112803068B CN 112803068 B CN112803068 B CN 112803068B CN 202011612907 A CN202011612907 A CN 202011612907A CN 112803068 B CN112803068 B CN 112803068B
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CN112803068A (en
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熊亚丽
许艳艳
唐超
徐春瑞
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The application provides an electrolyte, an electrochemical device containing the electrolyte and an electrochemical deviceAn electronic device comprising the electrochemical device. The electrolyte comprises lithium difluorophosphate and a compound represented by formula I; r is1、R2、R3、R4Each independently selected from nitrogen or C-R5And R is1、R2、R3、R4Either or both of which are nitrogen. The electrochemical device comprises a positive plate, a negative plate, an isolating membrane and the electrolyte. The electronic device includes the electrochemical device. The compound represented by the formula I and the lithium difluorophosphate are added into the electrolyte, so that the high-temperature cycle performance of an electrochemical device and an electronic device using the electrolyte can be remarkably improved, the direct-current impedance can be reduced, and the over-discharge storage performance can be improved.

Description

Electrolyte solution, electrochemical device, and electronic device
Technical Field
The present application relates to an electrolyte, an electrochemical device, and an electronic device.
Background
Electrochemical devices, such as lithium ion batteries, have been widely used due to their characteristics of high energy density, high power density, and stable service life. With the rapid development of technology, the diversity of market demands, and the rise of energy storage systems and electric automobile industries in the coming years, more requirements are put on lithium ion batteries, such as thinner, lighter, more diversified profiles, higher safety, higher energy density, and the like.
Disclosure of Invention
In some embodiments, the present application provides an electrolyte comprising lithium difluorophosphate and a compound of formula I;
Figure BDA0002875303590000011
in the formula I, R1、R2、R3、R4Each independently selected from nitrogen or C-R5And R is1、R2、R3、R4Either or both are nitrogen; wherein R is5Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-10Alkyl, substituted or unsubstituted C2-10Alkenyl, substituted or unsubstituted C2-10Alkynyl, substituted or unsubstituted C6-10Aryl, substituted or unsubstituted C3-10Alicyclic hydrocarbon group, substituted or unsubstituted C1-10Any of the heteroatom-containing groups, and when substituted, the substituent comprises halogen and the heteroatom comprises at least one of O, S, N, B, P, Si, wherein R1、R2、R3、R4R in (1)5May be bonded to each other or condensed to form a ring.
In some embodiments, the compound represented by formula I comprises at least one of the compounds represented by formula I-1 through formula I-11;
Figure BDA0002875303590000021
in some embodiments, the compound represented by formula I is present in an amount of 0.01 to 5% by mass, based on the mass of the electrolyte.
In some embodiments, the lithium difluorophosphate is present in an amount of 0.05 to 1.0 mass percent based on the mass of the electrolyte.
In some embodiments, the lithium difluorophosphate is present in an amount of 0.1 to 0.5 mass percent based on the mass of the electrolyte.
In some embodiments, the compound of formula I is present in an amount X by weight based on the weight of the electrolyte; based on the mass of the electrolyte, the mass percentage content of the lithium difluorophosphate is Y; wherein X and Y satisfy: X/Y is more than or equal to 0.2 and less than or equal to 17. In some embodiments, 0.3 ≦ X/Y ≦ 10. In some embodiments, 1 ≦ X/Y ≦ 7.
In some embodiments, X and Y satisfy between: x + Y is more than or equal to 0.4 and less than or equal to 5.5. In some embodiments, 0.8 ≦ X + Y ≦ 5.5. In some embodiments, 0.8 ≦ X + Y ≦ 4.
In some embodiments, the electrolyte further comprises at least one of a polynitrile compound, a compound having a double bond of sulfur and oxygen, and a compound having a lithium salt of boron.
In some embodiments, the polynitrile compound comprises at least one of the compounds represented by formula II;
Figure BDA0002875303590000031
in formula II, R21、R22、R23、R24Each independently selected from hydrogen, substituted or unsubstituted C1-10Alkyl, substituted or unsubstituted- (CH)2)a-CN, substituted or unsubstituted- (CH)2)b-O-(CH2)c-CN, substituted or unsubstituted- (CH)2)d-CH＝CH-(CH2)k-CN, substituted or unsubstituted
Figure BDA0002875303590000032
Substituted or unsubstituted
Figure BDA0002875303590000033
Any one of substituted or unsubstituted alkoxycarbonyl wherein a, b, c, d, e, f, g, h, i, j, k are each independently selected from integers from 0 to 10, and when substituted, the substituents comprise at least one of halogen;
n is selected from an integer of 0 to 3, and, when n is selected from an integer of 1 to 3, R21、R22、R23、R24At least two of which are cyano-containing groups, R being when n is selected from 022And R24Each containing at least a cyano group.
In some embodiments, the polynitrile compound comprises at least one of the compounds represented by formula II-1 through formula II-17;
Figure BDA0002875303590000034
Figure BDA0002875303590000041
in some embodiments, the compound containing a thiooxy double bond includes at least one of the compounds represented by formula III;
Figure BDA0002875303590000042
in formula III, R31、R32Each independently selected from substituted or unsubstituted C1-C5Alkyl, substituted or unsubstituted C2-C10Alkenyl, substituted or unsubstituted C2-C10Alkynyl, substituted or unsubstituted C3-C10Alicyclic hydrocarbon group, substituted or unsubstituted C6-C10Aryl, substituted or unsubstituted C1-C6Any one of the heteroatom-containing groups, and when substituted, the substituent comprises at least one of halogen and the heteroatom comprises at least one of O, S, P, N, Si, B, wherein R is31And R32Can be bonded or condensed to form a ring structure.
In some embodiments, the compound containing a thiooxy double bond includes at least one of the compounds represented by formula III-1 to formula III-8;
Figure BDA0002875303590000043
in some embodiments, the boron-containing lithium salt compound comprises at least one of the compounds represented by formula IV-1 through formula IV-14;
Figure BDA0002875303590000044
Figure BDA0002875303590000051
in some embodiments, the polynitrile compound is contained in an amount of 0.5% to 10% by mass based on the mass of the electrolyte.
In some embodiments, the content of the compound having a sulfur-oxygen-containing double bond is 0.01 to 5% by mass based on the mass of the electrolyte.
In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.01 to 5% by mass, based on the mass of the electrolyte.
In some embodiments, the present application also provides an electrochemical device comprising a positive electrode sheet, a negative electrode sheet, a separator, and the above electrolyte.
In some embodiments, the present application also provides an electronic device comprising the electrochemical device described above.
The technical scheme of the application has at least the following beneficial effects: lithium difluorophosphate and the compound shown in the formula I are added into the electrolyte, so that the high-temperature cycle performance of a high-voltage (4.5V +) lithium ion battery can be remarkably improved, the direct-current impedance is reduced, and the over-discharge storage performance is improved.
Detailed Description
It is to be understood that the disclosed embodiments are merely exemplary of the application that may be embodied in various forms and that, therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present application.
In the description of the present application, unless otherwise expressly specified or limited, the terms "first," "second," "third," "fourth," "fifth," "formula I," "formula II," "formula III," "formula IV," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or relationship to each other.
In the description of the present application, unless otherwise indicated, the functional groups of all compounds may be substituted or unsubstituted.
In the description of this application, the term "heteroatom" means an atom other than C, H. In some embodiments, the heteroatom comprises at least one of O, S, N, B, P, Si.
In the description of the present application, the term "heteroatom-containing group" refers to a functional group that contains at least one heteroatom.
In the description of the present application, the term "alicyclic hydrocarbon group" means a cyclic hydrocarbon having aliphatic properties, and containing a closed carbon ring in the molecule.
(electrolyte)
[ first additive ]
In some embodiments, the electrolyte comprises a first additive comprising lithium difluorophosphate and a compound represented by formula I;
Figure BDA0002875303590000061
in the formula I, R1、R2、R3、R4Each independently selected from nitrogen or C-R5And R is1、R2、R3、R4Either or both are nitrogen; wherein R is5Each independently selected from hydrogen, halogen, substituted or unsubstituted C1-10Alkyl, substituted or unsubstituted C2-10Alkenyl, substituted or unsubstituted C2-10Alkynyl, substituted or unsubstituted C6-10Aryl, substituted or unsubstituted C3-10Alicyclic hydrocarbon group, substituted or unsubstituted C1-10Any of the heteroatom-containing groups, and when substituted, the substituent comprises halogen and the heteroatom comprises at least one of O, S, N, B, P, Si, wherein R1、R2、R3、R4R in (1)5May be bonded to each other or condensed to form a ring.
In the present application, "independently" means that the individual entities described are independent of each other and may independently be the same or differentDifferent specific groups. For example, "R5Each independently selected from … "means that when there are 2 or more R's in formula I5When 2 and more R5The same or different.
One convenient and fast way to improve the performance of electrochemical devices is to add additives to the electrolyte; however, the inventors have found that additives capable of improving storage performance tend to increase the resistance of the electrochemical device and have a large influence on low-temperature performance, and may also affect cycle life. Currently known film forming additives, such as Vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), fluoroethylene carbonate (FEC), etc., can form good interface protection on the surface of the electrode sheet, and thus have certain improvement effect on the electrochemical device, but when the electrode sheet is in a high temperature condition, the performance of the electrochemical device is deteriorated, such as high temperature storage gas generation, cyclic gas generation, etc., problems occur. If the electrochemical device is subjected to decomposition of the electrolyte at a high temperature to cause ballooning, serious safety hazards are often caused.
Further, the inventors found that it is often difficult to form stable interface protection by adding a single additive to the electrolyte, and that the film formation resistance further increases with the addition amount of a single additive.
The compounds of formula I are effective in improving the cycle capacity retention of electrochemical devices (e.g., lithium ion batteries) while improving the amount of battery thickness growth during cycling. The compound represented by the formula I can adsorb trace water and HF in the electrolyte, so that the stability of the electrolyte is improved; meanwhile, the electrolyte is easy to oxidize and forms a compact protective film on the anode, so that the damage of the electrolyte to the anode is reduced; and the electrolyte is preferentially reduced to form a film on the negative electrode during first charge and discharge, the film is compact, and the decomposition reaction of the electrolyte on the negative electrode is inhibited. LiPO2F2It is possible to improve high-temperature cycle performance and reduce impedance of an electrochemical device (e.g., a lithium ion battery). This is because LiPO2F2The composition of LiF in the organic protective film can be increased, and the stability of the organic protective film is increased. The inventors found that the compound having the structure of formula I and LiPO2F2Have an cooperation betweenActing together, when the compound with the structure of the formula I and the LiPO are simultaneously added into the electrolyte2F2In this case, the high-temperature cycle performance of the electrochemical device (lithium ion battery) can be further improved, the direct-current impedance of the lithium ion battery can be reduced, and the over-discharge storage performance can be improved.
In some embodiments, the compound represented by formula I is present in an amount of 0.01 to 5% by mass and the lithium difluorophosphate is present in an amount of 0.05 to 1.0% by mass, based on the mass of the electrolyte. In some embodiments, the compound represented by formula I is present in an amount of 0.1 to 5% by mass and the lithium difluorophosphate is present in an amount of 0.1 to 0.5% by mass, based on the mass of the electrolyte. In some embodiments, the compound represented by formula I is present in an amount of 0.5 to 3% by mass and the lithium difluorophosphate is present in an amount of 0.1 to 0.5% by mass, based on the mass of the electrolyte.
When the mass percentage content of the compound represented by the formula I and the lithium difluorophosphate meets the range, the high-temperature cycle performance of the lithium ion battery can be better improved, the direct-current impedance of the lithium ion battery in the cycle process can be reduced, and the over-discharge storage performance can be better improved. At this time, the first additive with the above content is added, so that the electrolyte can be effectively stabilized, and excellent interface protection can be formed on the positive electrode and the negative electrode. If the mass percentage of the compound represented by formula I and/or lithium difluorophosphate is too high, the film formation resistance is relatively large, which in turn causes an increase in the battery resistance, affecting the battery performance to some extent. If the mass percentage of the compound represented by formula I and/or lithium difluorophosphate is too low, it is not sufficient to form relatively good interface protection, and the improvement of the cycle performance of the battery is affected to some extent.
In some embodiments, the compound of formula I is present in an amount X by weight based on the weight of the electrolyte; based on the mass of the electrolyte, the mass percentage content of the lithium difluorophosphate is Y; wherein X and Y satisfy: x + Y is more than or equal to 0.4 and less than or equal to 5.5. In some embodiments, 0.8 ≦ X + Y ≦ 5.5. In some embodiments, 0.8 ≦ X + Y ≦ 4.
In some embodiments, the compound of formula I is present in an amount X by weight based on the weight of the electrolyte; based on the mass of the electrolyte, the mass percentage content of the lithium difluorophosphate is Y; wherein X and Y satisfy: X/Y is more than or equal to 0.2 and less than or equal to 17. In some embodiments, 0.3 ≦ X/Y ≦ 10. In some embodiments, 1 ≦ X/Y ≦ 7. When the content relationship between the compound represented by formula I and lithium difluorophosphate satisfies the above range, the high-temperature cycle performance of the lithium ion battery can be further improved and the direct-current impedance of the lithium ion battery during the cycle can be reduced. If the ratio of X/Y is too large, i.e., the amount of the compound represented by formula I added to lithium difluorophosphate is too large, the transport of lithium ions may be affected to some extent, and the effect of improving the battery performance may be affected. If the ratio of X/Y is too small, i.e., if the amount of the compound represented by formula I added to lithium difluorophosphate is too small, the effect of improving the lithium difluorophosphate may be weak due to the small amount added.
[ second additive ]
In some embodiments, the electrolyte further comprises a second additive, the second additive comprising a polynitrile compound.
In some embodiments, the polynitrile compound comprises at least one of the compounds represented by formula II;
Figure BDA0002875303590000081
in formula II, R21、R22、R23、R24Each independently selected from hydrogen, substituted or unsubstituted C1-10Alkyl, substituted or unsubstituted- (CH)2)a-CN, substituted or unsubstituted- (CH)2)b-O-(CH2)c-CN, substituted or unsubstituted- (CH)2)d-CH＝CH-(CH2)k-CN, substituted or unsubstituted
Figure BDA0002875303590000091
Substituted or unsubstituted
Figure BDA0002875303590000092
Any one of substituted or unsubstituted alkoxycarbonyl, wherein a, b, c, d, e, f, g, h, i, j, k are each independently selected from integers from 0 to 10, and when substituted, the substituents comprise at least one of halogen; n is selected from an integer of 0 to 3, and, when n is selected from an integer of 1 to 3, R21、R22、R23、R24At least two of which are cyano-containing groups, R being when n is selected from 022And R24Each containing at least a cyano group.
The introduction of the polynitrile compound can obviously improve the performance and the electrical performance of the hot box. The energy level of lone pair electrons in the nitrile functional group is close to the energy level of the vacant orbital at the outermost layer of transition metal atoms in the anode active material of the lithium ion battery, so that organic molecules containing the nitrile functional group can be subjected to complex adsorption on the surface of the anode. The organic molecules adsorbed on the surface of the anode can well separate easily-oxidizable components in the electrolyte from the surface of the anode, so that the oxidation of the anode surface of the charged lithium ion battery on the electrolyte is greatly reduced. The inventors found that when a polynitrile compound is further added to the electrolyte, the polynitrile compound can react with a compound of formula I, LiPO2F2The three components coexist to form a more stable SEI, so that the high-temperature cycle and high-temperature intermittent cycle performance, the high-temperature storage performance and the hot box performance of an electrochemical device (such as a lithium ion battery) are further improved.
In some embodiments, the compound represented by formula II comprises at least one of the compounds represented by formula II-1 through formula II-17;
Figure BDA0002875303590000093
Figure BDA0002875303590000101
in some embodiments, the polynitrile compound is contained in an amount of 0.5 to 10% by mass based on the mass of the electrolyte. In some embodiments, the polynitrile compound is present in an amount of 2 to 10% by mass based on the mass of the electrolyte. In some embodiments, the polynitrile compound is present in an amount of 2 to 5% by mass based on the mass of the electrolyte.
When the mass percentage content of the added polynitrile compound meets the range, the high-temperature cycle and high-temperature intermittent cycle performance, the high-temperature storage performance and the hot box performance of the lithium ion battery can be further improved.
[ third additive ]
In some embodiments, the electrolyte further comprises a third additive, the third additive comprising a compound containing a sulfur-oxygen double bond.
In some embodiments, the compound containing a thiooxy double bond comprises at least one of the compounds represented by formula III;
Figure BDA0002875303590000102
in formula III, R31、R32Each independently selected from substituted or unsubstituted C1-C5Alkyl, substituted or unsubstituted C2-C10Alkenyl, substituted or unsubstituted C2-C10Alkynyl, substituted or unsubstituted C3-C10Alicyclic hydrocarbon group, substituted or unsubstituted C6-C10Aryl, substituted or unsubstituted C1-C6Any one of the heteroatom-containing groups, and when substituted, the substituent comprises at least one of halogen and the heteroatom comprises at least one of O, S, P, N, Si, B, wherein R is31And R32Can be bonded or condensed to form a ring structure.
The inventors found that when a compound containing a sulfur-oxygen double bond is further added to the electrolyte, the thermal stability and the mechanical stability of the interfacial film can be further improved, thereby improving the high-temperature cycle performance and the high-temperature storage performance of an electrochemical device (such as a lithium ion battery), and reducing the direct current impedance of the battery.
In some embodiments, the compound represented by formula III includes at least one of the compounds represented by formula III-1 through formula III-8;
Figure BDA0002875303590000111
in some embodiments, the content of the compound having a sulfur-oxygen-containing double bond is 0.01 to 5% by mass based on the mass of the electrolyte. In some embodiments, the content of the compound having a sulfur-oxygen-containing double bond is 0.5% to 5% by mass based on the mass of the electrolyte. In some embodiments, the content of the compound having a sulfur-oxygen-containing double bond is 0.5% to 3% by mass based on the mass of the electrolyte.
When the mass percentage of the added compound containing the sulfur-oxygen double bond meets the range, the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery can be further improved, and the direct-current impedance of the battery is reduced.
[ fourth additive ]
In some embodiments, the electrolyte further comprises a fourth additive comprising a boron-containing lithium salt compound.
In some embodiments, the boron-containing lithium salt compound comprises at least one of the compounds represented by formula IV-1 through formula IV-14;
Figure BDA0002875303590000112
Figure BDA0002875303590000121
the boron-containing lithium salt compound has a higher film-forming potential than polynitriles and can preferentially form a film to suppress consumption of the polynitriles, and therefore, the inventors have found that when the boron-containing lithium salt compound is further added to the electrolyte, high-temperature cycle, high-temperature storage, and float charge performance of an electrochemical device (e.g., of a lithium ion battery) can be further improved.
In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.01 to 5% by mass, based on the mass of the electrolyte. In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.1 to 5% by mass, based on the mass of the electrolyte. In some embodiments, the boron-containing lithium salt compound is present in an amount of 0.5 to 1% by mass, based on the mass of the electrolyte.
When the mass percentage of the added boron-containing lithium salt compound meets the above range, the high-temperature cycle, high-temperature storage and floating charge performance of the lithium ion battery can be further improved.
In the present application, the first additive, the second additive, the third additive and the fourth additive may be used alone or in combination. In some embodiments, the electrolyte includes a first additive and one or more selected from a second additive, a third additive, and a fourth additive.
In the present application, the additive may further include other additives selected from one or more of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), Vinyl Ethylene Carbonate (VEC), 1, 3-dioxane, 1, 4-dioxane, dioxolane, succinic anhydride, glutaric anhydride, citraconic anhydride, maleic anhydride, methylsuccinic anhydride, 2, 3-dimethylmaleic anhydride, and trifluoromethylmaleic anhydride. In some embodiments, the other additive is present in an amount of 0.01 to 5% by mass, based on the mass of the electrolyte.
[ organic solvent ]
In some embodiments, the electrolyte further comprises an organic solvent. The organic solvent is an organic solvent known in the art to be suitable for an electrochemical device, and for example, a nonaqueous organic solvent is generally used.
In some embodiments, the organic solvent comprises at least one of a cyclic ester organic solvent and a chain ester organic solvent. In some embodiments, the mass ratio of the cyclic ester organic solvent to the chain ester organic solvent is from 1:9 to 7: 3.
In some embodiments, the cyclic ester comprises at least one of ethylene carbonate (abbreviated EC), propylene carbonate (abbreviated PC), γ -butyrolactone (abbreviated BL), fluoro substituted ethylene carbonate, or propylene carbonate. In some embodiments, the chain ester comprises at least one of dimethyl carbonate (abbreviated DMC), diethyl carbonate (abbreviated DEC), ethyl methyl carbonate (abbreviated EMC), ethyl acetate (abbreviated EA), methyl formate (abbreviated MF), ethyl formate (abbreviated MA), ethyl propionate (abbreviated EP), propyl propionate (abbreviated PP), methyl butyrate (abbreviated MB), ethyl fluoro-methyl carbonate, ethyl fluoro-propionate.
In some embodiments, the above organic solvents may be used alone or in a mixture, and when used in a mixture, the ratio of the mixture may be controlled according to desired electrochemical device properties.
[ electrolyte salt ]
In some embodiments, the electrolyte further comprises an electrolyte salt. The electrolyte salt is well known to those skilled in the art and is suitable for use in electrochemical devices, and may be selected for various electrochemical devices. For example, for lithium ion batteries, lithium salts are commonly used as electrolyte salts.
In some embodiments, the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt.
In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF)6) One or more of lithium bis (fluorosulfonyl) imide (LiFSI) and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI).
In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF)6)。
In some embodiments, the molar concentration of lithium in the lithium salt is 0.5 to 3mol/L based on the total volume of the electrolyte. In some embodiments, the molar concentration of lithium in the lithium salt is 0.5 to 2mol/L based on the total volume of the electrolyte. In some embodiments, the molar concentration of lithium in the lithium salt is 0.8 to 1.5mol/L based on the total volume of the electrolyte.
(electrochemical device)
The electrochemical device of the present application is, for example, a primary battery, a secondary battery, a fuel cell, a solar cell, or a capacitor. The secondary battery is, for example, a lithium secondary battery including, but not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
In some embodiments, the electrochemical device is adapted for a charge cutoff voltage of not less than 4.2V.
In some embodiments, the electrochemical device comprises a positive electrode tab, a negative electrode tab, a separator, and an electrolyte as described herein before.
[ Positive electrode sheet ]
The positive electrode tab is a positive electrode tab known in the art that can be used in an electrochemical device. In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is disposed on a surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material.
In some embodiments, the structure of the positive electrode tab is a structure of a positive electrode tab that can be used in an electrochemical device, which is well known in the art.
In some embodiments, the positive current collector is a metal, such as, but not limited to, aluminum foil.
The positive electrode active material may be any conventionally known material capable of reversibly intercalating and deintercalating active ions, which is known in the art and can be used as a positive electrode active material for an electrochemical device.
In some embodiments, the positive electrode active material is a positive electrode having an operating potential of 4.5V or more with respect to lithium metal. That is, in some examples, the positive electrode active material has a charge-discharge region of 4.5V or more with respect to metallic lithium.
In some embodiments, the positive active material comprises a lithium-containing transition metal oxide. In some embodiments, the positive active material includes at least one of a composite oxide of metals of lithium and cobalt, manganese, nickel, or a combination thereof. In some embodiments, the positive active material comprises LiCoO2、LiNiO2、LiMn2O4、LiCo1-yMyO2、LiNi1-yMyO2、LiMn2-yMyO4、LiNixCoyMnzM1-x-y-zO2Wherein M is selected from one or more of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, y is more than or equal to 0 and less than or equal to 1, x is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and x + y + z is less than or equal to 1.
In some embodiments, the positive electrode active material layer further includes a binder and a conductive material. The binder is a binder known in the art to be used as a positive electrode active material layer. A binder such as, but not limited to, polyvinylidene fluoride. The binder is used to improve the binding property between the positive electrode active material particles and the current collector. The conductive material is a conductive material known in the art that can be used as the positive electrode active material layer. Conductive materials such as, but not limited to, conductive carbon black, conductive paste. The conductive material is used to provide conductivity to the electrodes.
In some embodiments, the method for preparing the positive electrode sheet is a method for preparing a positive electrode sheet that can be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the positive electrode slurry, a solvent is generally added, and the positive electrode active material is dissolved or dispersed in the solvent after adding a binder and, if necessary, a conductive material and a thickener to prepare the positive electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art that can be used as the positive electrode active material layer, and is, for example, but not limited to, N-methylpyrrolidone (NMP).
The mixing ratio of the positive electrode active material, the binder, and the conductive material in the positive electrode active material layer is not particularly limited, and may be controlled according to the desired electrochemical device performance.
The application has no special limitation on the compaction density of the positive plate, and can be adjusted according to actual needs.
[ negative electrode sheet ]
The negative electrode tab is a negative electrode tab known in the art that may be used in an electrochemical device. In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is disposed on a surface of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material.
In some embodiments, the structure of the negative electrode sheet is a structure of a negative electrode sheet that may be used in an electrochemical device, as is well known in the art.
In some embodiments, the negative current collector is a metal such as, but not limited to, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or combinations thereof.
The negative electrode active material may be selected from a variety of conventionally known materials capable of reversibly intercalating and deintercalating active ions or a variety of conventionally known materials capable of reversibly doping and dedoping active ions, which are known in the art and can be used as a negative electrode active material for an electrochemical device.
In some embodiments, the negative active material comprises at least one of a carbon material, a metal alloy, a lithium-containing oxide, and a silicon-containing material. In some embodiments, the carbon material is selected from graphite. In some embodiments, the surface of the carbon material is provided with a coating. In some embodiments, the negative active material is graphite coated with amorphous carbon on the surface.
In some embodiments, the negative electrode active material layer further comprises a binder. The binder is a binder known in the art to be used as the anode active material layer. Such as but not limited to styrene butadiene rubber. The binder is used to improve binding properties of the negative active material particles to each other and to the current collector. In some embodiments, the negative electrode active material layer further includes a conductive material. The conductive material is a conductive material known in the art that can be used as the anode active material layer. The conductive material is used to improve the conductivity of the negative electrode sheet.
In some embodiments, the method of preparing the negative electrode sheet is a method of preparing a negative electrode sheet that may be used for an electrochemical device, which is well known in the art. In some embodiments, in the preparation of the negative electrode slurry, a solvent is generally added, and the negative electrode active material is dissolved or dispersed in the solvent after adding a binder and, if necessary, a conductive material and a thickener to prepare the negative electrode slurry. The solvent is evaporated during the drying process. The solvent is a solvent known in the art, such as, but not limited to, water, which can be used as the negative electrode active material layer. The thickener is a thickener known in the art that can be used as the anode active material layer, and is, for example, but not limited to, sodium carboxymethyl cellulose.
The mixing ratio of the positive electrode active material, the binder, and the thickener in the negative electrode active material layer is not particularly limited, and may be controlled according to the desired electrochemical device performance.
The compaction density of the negative electrode plate is not particularly limited and can be adjusted according to actual needs.
[ isolation film ]
In some embodiments, the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and a separator that can be used in the electrochemical device, which is well known in the art, may be used.
In some embodiments, the barrier film comprises at least one of Polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate copolymer.
In some embodiments, the separator film comprises a substrate layer. In some embodiments, the substrate layer is a nonwoven fabric, a film, or a composite film having a porous structure. In some embodiments, the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.
In some embodiments, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. In some embodiments, the inorganic layer comprises inorganic particles and a binder. In some embodiments, the inorganic particles are selected from the group consisting of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. In some embodiments, the binder is selected from the group consisting of polyvinylidene fluoride, copolymers of vinylidene fluoride-hexafluoropropylene, polyamides, polyacrylonitrile, polyacrylates, polyacrylic acids, polyacrylates, polyvinylpyrollidones, polyvinyl alcoxyl, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene, in one or more combinations. In some embodiments, the polymer layer comprises a polymer of a material selected from at least one of a polyamide, a polyacrylonitrile, an acrylate polymer, a polyacrylic acid, a polyacrylate, a polyvinylpyrrolidone, a polyvinyl alkoxide, a polyvinylidene fluoride, a poly (vinylidene fluoride-hexafluoropropylene).
[ outer packaging case ]
In some embodiments, the electrochemical device further comprises an overwrap housing. The outer packaging case is a well known outer packaging case in the art that can be used for electrochemical devices and is stable to the electrolyte used, such as, but not limited to, a metal-based outer packaging case.
(electronic device)
The electronic device of the present application is any electronic device such as, but not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handy cleaner, a portable CD player, a mini disc, a transceiver, an electronic notebook, a calculator, a memory card, a portable recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large-sized household battery, and a lithium ion capacitor. Note that the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-exemplified electronic devices. The air transport carrier device comprises an air transport carrier device in the atmosphere and an air transport carrier device outside the atmosphere.
In some embodiments, the electronic device comprises an electrochemical device as described herein.
The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
In the following examples and comparative examples, reagents, materials and instruments used were commercially available or synthetically available, unless otherwise specified.
The specific additives used in the electrolyte are as follows:
a first additive:
lithium difluorophosphate (LiPO)2F2)；
Figure BDA0002875303590000171
A second additive:
Figure BDA0002875303590000181
a third additive:
Figure BDA0002875303590000182
a fourth additive:
Figure BDA0002875303590000183
preparation method of lithium ion battery
(1) Preparation of the electrolyte
At water content<In a 10ppm argon atmosphere glove box, Ethylene Carbonate (EC), Propylene Carbonate (PC) and diethyl carbonate (DEC) are uniformly mixed according to a mass ratio of 3:3:4, and then fully dried lithium salt LiPF is added6(1M) dissolving in the above non-aqueous solvent, and addingAnd (3) adding additives in a certain mass to prepare the electrolyte in the embodiment.
(2) Preparation of positive plate
Mixing anode active material LCO (molecular formula is LiCoO)2) The conductive carbon black and the adhesive polyvinylidene fluoride (PVDF for short) are fully stirred and mixed in a proper amount of N-methyl pyrrolidone (NMP for short) solvent according to the weight ratio of 97:1.4:1.6 to form uniform anode slurry; coating the slurry on a positive current collector Al foil, drying and cold pressing to obtain a positive plate, wherein the positive electrode compaction density is 4.15g/cm3。
(3) A polyethylene porous polymer film was used as the separator.
(4) Preparation of negative plate
Fully stirring and mixing a negative electrode active material graphite, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) in a proper amount of deionized water solvent according to a weight ratio of 97.7:1.3:1.0 to form uniform negative electrode slurry; coating the slurry on a Cu foil of a negative current collector, drying and cold-pressing to obtain a negative plate, wherein the compaction density of the negative electrode is 1.75g/cm3。
(5) Preparation of lithium ion battery
Stacking the positive plate, the isolating film and the negative plate in sequence to enable the isolating film to be positioned between the positive plate and the negative plate to play an isolating role, and then winding to obtain the bare cell; and (3) placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried cell, and performing vacuum packaging, standing, formation, shaping and other processes to complete the preparation of the lithium ion battery.
Performance test method of lithium ion battery
(1) Cycle test at 45 ℃
Placing the battery in a constant temperature box at 45 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant; charging the battery reaching the constant temperature to 4.5V at 45 ℃ with a constant current of 0.2C, and then charging to 0.05C at 4.5V with a constant voltage; standing for 5 minutes, discharging to 3.0V at a constant current of 0.2C, standing for 5 minutes, testing and recording the thickness of the battery at the moment by using a micrometer to record the thickness as the initial battery thickness, and simultaneously testing the discharge capacity at the moment to record the first cycle discharge capacity; then charging to 4.15V by a constant current of 1.3C, and then charging to 1C by a constant voltage of 4.15V; charging to 4.25V at a constant current of 1C, and then charging to 0.8 at a constant voltage of 4.25V; charging to 4.5V at constant current of 0.8C, and then charging to 0.05C at constant voltage of 4.5V; the mixture was left for 5 minutes, followed by constant current discharge at 1C to a voltage of 3.0V, and left to stand for 5 minutes. The battery was cycled 400 times after the charge/discharge was performed, the impedance after the battery was cycled 400 times was measured and recorded as the battery impedance after the cycle 400 times, and the discharge capacity after the battery was cycled 400 times was measured and recorded as the 400 th cycle discharge capacity.
The capacity retention (%) of the lithium ion battery after 400 cycles at 45 ℃ was equal to 400 th cycle discharge capacity/first cycle discharge capacity × 100%.
The impedance increase rate (%) of the lithium ion battery after 400 cycles at 45 ℃. (battery impedance after 400 cycles-initial battery impedance)/initial battery impedance × 100%.
(2) Over-discharge storage test
Placing the lithium ion battery in a constant temperature box at 25 ℃, standing for 30 minutes to keep the temperature of the lithium ion battery constant, and testing and recording the initial thickness of the battery by using a micrometer; discharging to 2.8V at constant current of 0.5C, standing for 10 min, discharging to 2.8V at constant current of 0.1C, standing for 10 min, and discharging to 2.8V at constant current of 0.01C; placing the discharged battery in a constant temperature box at 60 ℃, storing for 180 days, testing and recording the thickness of the battery after 180 days of storage as the thickness of the battery after 180 days of storage;
thickness expansion (%) of the lithium ion battery after storage at 60 ℃ for 180 days, i.e., battery thickness/initial thickness after storage for 180 days × 100%
(3) Hot box test
The lithium ion battery is charged at 25 ℃ with a constant current of 0.7 ℃ to 4.5V and a constant voltage of 4.5V to a current of 0.05C. The cell was placed in a high temperature oven and heated to 135 ℃ with a temperature rise rate of 5 ± 2 ℃/min and then held for 1h, and the change in voltage, temperature and oven temperature of the cell was recorded. The battery passed the test without ignition, explosion or smoke. And testing 10 batteries in each group, and recording the number of passing test batteries.
(4) Intermittent cycle test at 45 DEG C
Charging the lithium ion battery to 4.5V at a constant current of 1C in a constant temperature box at 45 ℃, and then charging to 0.05C at a constant voltage of 4.5V; standing at 45 ℃ for 19.5h, then discharging to 3V at a constant current of 0.5C, standing for 10 minutes, and testing the discharge capacity at this time and recording as the first cycle discharge capacity; this is done as a cycle. This cycle was repeated 50 times, and the discharge capacity after the 50 th time of the test was recorded as the 50 th intermittent cycle discharge capacity. During this procedure, the thickness change and capacity retention of the battery were recorded and the test was stopped if severe gassing (thickness change rate over 50%) or the cycle capacity retention dropped to 60%.
The capacity retention (%) of the lithium ion battery after 50 intermittent cycles at 45 ℃ was 50% of the 50 th intermittent cycle discharge capacity/the first cycle discharge capacity × 100%
(5)85 ℃ storage test
The cell was discharged at 25 ℃ to 3.0V at 0.5C, charged to 4.5V at 0.5C, then charged to 0.05V at 4.5V at constant voltage, measured with a micrometer and the thickness of the cell recorded as H11(ii) a Then the battery is placed in an oven at 85 ℃ for storage for 12 hours, and after 12 hours, the thickness of the battery is tested and recorded by a micrometer and is recorded as H12。
Thickness expansion rate (%) of lithium ion battery after storage at 85 ℃ for 12 hours12-H11)/H11×100％
(6) 20% SOC DCR (25 ℃ C.) test
Standing the lithium ion battery in a constant temperature box at 25 ℃ for 1 hour to keep the temperature of the lithium ion battery constant; charging to 4.2V at a constant current of 0.5C, then charging to 4.5V at a constant current of 0.3C, charging to a current of 0.02C at a constant voltage of 4.5V, and standing for 30 minutes; discharging to 3.4V at constant current of 0.1C, and standing for 30 min (the step obtains actual capacity); then charging the lithium ion battery to 4.2V at a constant current of 0.5C at 25 ℃, then charging to 4.5V at a constant current of 0.3C and charging at a constant voltage of 4.5V until the current is 0.02C, and standing for 30 minutes; discharging at constant current of 0.1C for 60min (calculated from the actual capacity obtained in the previous step), and recording the voltage at this time as V1(ii) a Then discharging with 1C constant current for 1s (the capacity is marked by corresponding lithium ion battery)Fill volume calculation), the voltage at that time was recorded as V2And calculating the direct current impedance corresponding to the 20% SOC state of the lithium ion battery.
Lithium ion battery 20% SOC dc impedance ═ V1-V2)/1C
(7) Float charge test at 45 deg.C
Charging the battery to 4.15V at 25 ℃ with a constant current of 1.3C, and then charging to a current of 1C with a constant voltage of 4.15V; charging to 4.25V at a constant current of 1C, and then charging to a current of 0.8 at a constant voltage of 4.25V; charging to 4.5V at constant current of 0.8C, charging to 0.05C at constant voltage of 4.5V, testing with micrometer, and recording the thickness of the battery as D11(ii) a Standing at 45 deg.C for 1 hr, charging to 4.5V at 0.4C constant current, charging at 4.5V constant voltage for 1000 hr, measuring with micrometer, and recording the thickness of the battery as D12；
Thickness expansion ratio (%) after 1000h of 45 ℃ floating charge (D)12-D11)/D11×100％
The lithium ion batteries of examples 1 to 23 and comparative examples 1 to 3 were prepared according to the above preparation methods, and the kinds and contents of the additives used were as shown in table 1, wherein the contents of the respective additives were weight percentages calculated based on the total mass of the electrolyte.
TABLE 1 relevant parameters for examples 1-23 and comparative examples 1-3
Figure BDA0002875303590000211
Figure BDA0002875303590000221
From the data analysis of table 1, it can be seen that when the compound represented by formula I and lithium difluorophosphate are added to the electrolyte simultaneously, a synergistic effect is formed between the two, which can improve the capacity retention rate of high-temperature cycle of the lithium ion battery and reduce the impedance increase rate, and can also improve the high-temperature storage performance of the lithium ion battery. And, when the content relationship between the compound represented by formula I and lithium difluorophosphate satisfies a specific relationship, there is a better performance improvement effect.
As can be seen from the comparison of comparative example 2 and example 4, when the compound represented by formula I is used in combination with lithium difluorophosphate, both the cycle performance and the overdischarge storage performance of the lithium ion battery are greatly improved. This is because LiPO2F2The LiF component in the organic protective film formed by the compound shown in the formula I can be increased, the stability of the organic protective film is increased, and the impedance of the protective film can be reduced, so that the capacity retention rate of the lithium ion battery at a high temperature of 45 ℃ under circulation is remarkably improved, the impedance increase rate is greatly reduced, and the over-discharge high-temperature storage performance is more excellent.
It can be seen from the comparison of examples 1 to 23 that when the total content of the compound represented by formula I and lithium difluorophosphate is more than 5.5, the transmission of lithium ions is affected and the improvement effect is affected due to the excessive addition amount of the additive, and when the ratio X/Y of the content of the compound represented by formula I and lithium difluorophosphate is less than 0.2 and X + Y is less than 0.4, the improvement effect is not good due to the small addition amount of the compound represented by formula I.
As can be seen from the comparison of examples 1 to 7 and 14 to 18, the degree of improvement increases and decreases with increasing content when the compound represented by formula I is added, and is relatively optimal when the amount is 1%. In this case, the compound represented by formula I can effectively stabilize the electrolyte and simultaneously form excellent interface protection at the positive and negative electrodes.
The lithium ion batteries of examples 24 to 33 and comparative examples 1 and 4 were prepared according to the above preparation methods, and the kinds and contents of the additives used were as shown in table 2, wherein the contents of the respective additives were weight percentages calculated based on the total mass of the electrolyte.
TABLE 2 relevant parameters for examples 24-33 and comparative examples 1,4
Figure BDA0002875303590000231
It can be seen from the data analysis of table 2 that when the polynitrile compound described in the present application is further added to the electrolyte, a synergistic effect can be formed with the compound represented by formula I in the electrolyte and lithium difluorophosphate, and the coexistence of the compound and lithium difluorophosphate can form a more stable SEI, thereby further improving the high-temperature cycle and high-temperature intermittent cycle performance, the high-temperature storage performance and the hot box performance of the lithium ion battery.
The lithium ion batteries of examples 34 to 46 and comparative examples 5 to 6 were manufactured according to the above-described manufacturing method, and the kinds and contents of the additives used were as shown in table 3, wherein the contents of the respective additives were weight percentages calculated based on the total mass of the electrolyte.
TABLE 3 relevant parameters for examples 34-46 and comparative examples 5-6
Figure BDA0002875303590000232
Figure BDA0002875303590000241
As can be seen from the data analysis of Table 3, the compound represented by formula I, lithium difluorophosphate and the compound having a sulfur double bond act together to improve cycle and storage properties; this is because the sulfur-containing double bond compound can form an S-rich interfacial film, which can further improve the thermal stability and mechanical stability of the interfacial film; when the polynitrile compound is further added into the electrolyte, the high-temperature cycle performance and the high-temperature storage performance of the lithium ion battery can be further improved, and the direct-current impedance is reduced.
The lithium ion batteries of examples 47 to 52 and comparative examples 7 to 9 were prepared according to the above-described preparation methods, and the kinds and contents of the additives used were as shown in table 4, wherein the contents of the respective additives were in weight percent calculated based on the total mass of the electrolyte.
TABLE 4 relevant parameters for examples 47-52 and comparative examples 7-9
Figure BDA0002875303590000242
Figure BDA0002875303590000251
As can be seen from the data analysis of table 4, when the boron-containing lithium salt compound described herein is further added to the electrolyte, it can act together with the compound represented by formula I, lithium difluorophosphate, polynitrile compound and a compound containing a thiooxy double bond in the electrolyte to form a film on the surface of the electrode sheet in preference to the polynitrile compound, thereby suppressing the consumption of polynitrile, and further improving the high-temperature cycle, high-temperature storage and float charge performance of the lithium ion battery.
The above detailed description describes exemplary embodiments, but is not intended to limit the combinations explicitly disclosed herein. Thus, unless otherwise specified, various features disclosed herein can be combined together to form a number of additional combinations that are not shown for the sake of brevity.

Claims (13)

1. An electrolyte for a lithium ion battery, comprising lithium difluorophosphate and a compound represented by formula I;
Figure FDA0003518894760000011
in the formula I, the compound is shown in the specification,
R1、R2、R3、R4each independently selected from nitrogen or C-R5And R is1、R2、R3、R4Either or both are nitrogen;
wherein the content of the first and second substances,
R5each independently selected from hydrogen, halogen, substituted or unsubstituted C1-10Alkyl, substituted or unsubstituted C2-10Alkenyl, substituted or unsubstituted C2-10Alkynyl, substituted or unsubstituted C6-10Aryl, substituted or unsubstituted C3-10Alicyclic hydrocarbon group, substituted or unsubstituted C1-10In the hetero atom-containing groupAnd, when substituted, the substituents include halogen and the heteroatom includes at least one of O, S, N, B, P, Si, wherein R is1、R2、R3、R4R in (1)5May be bonded to each other or condensed to form a ring.
2. The electrolyte for a lithium ion battery according to claim 1, wherein the compound represented by formula I includes at least one of compounds represented by formulae I-1 to I-11;
Figure FDA0003518894760000012
Figure FDA0003518894760000021
3. the electrolyte for a lithium ion battery according to claim 1,
the mass percentage content of the compound represented by the formula I is 0.01-5%, and the mass percentage content of lithium difluorophosphate is 0.05-1.0% based on the mass of the electrolyte.
4. The electrolyte for a lithium ion battery according to claim 1,
the mass percentage content of the compound represented by the formula I is X based on the mass of the electrolyte;
based on the mass of the electrolyte, the mass percentage content of lithium difluorophosphate is Y;
wherein X and Y satisfy: X/Y is more than or equal to 0.2 and less than or equal to 17, and X + Y is more than or equal to 0.4 and less than or equal to 5.5.
5. The electrolyte solution for a lithium ion battery according to claim 1, further comprising at least one of a polynitrile compound, a compound having a double bond of sulfur and oxygen, and a compound having a lithium salt of boron.
6. The electrolyte for a lithium ion battery according to claim 5, wherein the polynitrile compound includes at least one of compounds represented by formula II;
Figure FDA0003518894760000022
in the formula II, the reaction mixture is shown in the formula II,
R21、R22、R23、R24each independently selected from hydrogen, substituted or unsubstituted C1-10Alkyl, substituted or unsubstituted- (CH)2)a-CN, substituted or unsubstituted- (CH)2)b-O-(CH2)c-CN, substituted or unsubstituted- (CH)2)d-CH＝CH-(CH2)k-CN, substituted or unsubstituted
Figure FDA0003518894760000031
Substituted or unsubstituted
Figure FDA0003518894760000032
Any one of substituted or unsubstituted alkoxycarbonyl, wherein a, b, c, d, e, f, g, h, i, j, k are each independently selected from integers from 0 to 10, and when substituted, the substituents comprise at least one of halogen;
n is selected from an integer of 0 to 3, and, when n is selected from an integer of 1 to 3, R21、R22、R23、R24At least two of which are cyano-containing groups, R being when n is selected from 022And R24Each containing at least a cyano group.
7. The electrolyte for a lithium ion battery according to claim 5, wherein the polynitrile compound comprises at least one of compounds represented by formula II-1 to formula II-17;
Figure FDA0003518894760000033
Figure FDA0003518894760000041
8. the electrolyte for a lithium ion battery according to claim 5, wherein the sulfur-oxygen double bond-containing compound includes at least one of compounds represented by formula III;
Figure FDA0003518894760000042
in the case of the formula III,
R31、R32each independently selected from substituted or unsubstituted C1-C5Alkyl, substituted or unsubstituted C2-C10Alkenyl, substituted or unsubstituted C2-C10Alkynyl, substituted or unsubstituted C3-C10Alicyclic hydrocarbon group, substituted or unsubstituted C6-C10Aryl, substituted or unsubstituted C1-C6Any one of the heteroatom-containing groups, and when substituted, the substituent comprises at least one of halogens, and the heteroatom comprises at least one of O, S, P, N, Si, B, wherein R is31And R32Can be bonded or condensed to form a ring structure.
9. The electrolyte for a lithium ion battery according to claim 8, wherein the sulfur-oxygen double bond-containing compound includes at least one of compounds represented by formulae III-1 to III-8;
Figure FDA0003518894760000043
10. the electrolyte for a lithium ion battery according to claim 5, wherein the boron-containing lithium salt compound comprises at least one of compounds represented by formula IV-1 to formula IV-14;
Figure FDA0003518894760000051
11. the electrolyte for a lithium ion battery according to claim 5, satisfying at least one of the following conditions:
a) the mass percentage content of the polynitrile compound is 0.5 to 10 percent based on the mass of the electrolyte;
b) the sulfur-oxygen double bond-containing compound is contained in an amount of 0.01 to 5% by mass based on the mass of the electrolyte;
c) the content of the boron-containing lithium salt compound is 0.01 to 5 mass% based on the mass of the electrolyte.
12. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte for a lithium ion battery according to any one of claims 1 to 11.
13. An electronic device comprising the lithium ion battery of claim 12.
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