CN114899476A - Electrolyte and battery comprising same - Google Patents

Electrolyte and battery comprising same Download PDF

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Publication number
CN114899476A
CN114899476A CN202210521055.1A CN202210521055A CN114899476A CN 114899476 A CN114899476 A CN 114899476A CN 202210521055 A CN202210521055 A CN 202210521055A CN 114899476 A CN114899476 A CN 114899476A
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electrolyte
battery
additive
formula
positive electrode
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王海
李素丽
李俊义
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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

Abstract

The invention provides an electrolyte and a battery comprising the electrolyte, wherein a phosphate functional group contained in a first additive in the electrolyte is easy to form a phosphorus-rich protective film on a high-voltage positive electrode, and a nitrile functional group contained in the electrolyte is coordinated with transition metal ions to inhibit the oxidation capability of the transition metal on the surface of the positive electrode, so that the film forming and coordination effects can achieve a synergistic effect, and the high-voltage performance of the battery is remarkably improved. In addition, redundant nitrile functional groups can be coordinated with transition metal ions at some anode positions without film formation, so that the high-voltage performance of the battery is further improved, and the effect of improving the cycle performance is achieved. Meanwhile, the corresponding film forming and coordination effects can also improve the furnace temperature performance of the battery and increase the safety performance of the battery at high temperature.

Description

Electrolyte and battery comprising same
Technical Field
The invention relates to an electrolyte and a battery comprising the same, and belongs to the technical field of batteries.
Background
Lithium ion batteries have high specific energy density and long cycle life, and thus are widely used as chemical power sources for various electronic products, including notebook computers, mobile phones, bluetooth headsets and the like, and are increasingly used in electric vehicles, various electric tools and energy storage devices in recent years. With the development of science and technology, the performance of application products needs to be further improved, and higher requirements are also put forward on the energy density of the battery.
In order to increase the energy density of the battery, it is a common path to further increase the voltage of the lithium ion battery cathode material. At present, a large-scale commercial high-voltage positive electrode material is mainly lithium cobaltate, and the gram energy density of the high-voltage positive electrode material is gradually increased along with the increase of the voltage of the lithium cobaltate, so that the mass energy density and the volume energy density of a corresponding whole battery core are increased. However, as the voltage rises, the side reaction of the electrolyte rapidly increases, the cycle performance of the battery rapidly decays, and the cycle performance of the battery can be improved to a certain extent by the positive electrode protection additive. However, when the voltage reaches 4.5V or more, it is difficult for conventional positive electrode protection additives (such as alkyl nitrile compounds that are commonly used) to ensure the high-temperature cycle stability of the battery, and therefore, development of novel positive electrode protection additives is urgently needed.
Disclosure of Invention
In order to solve the problems of poor oxidation resistance and over-fast high-temperature cycle attenuation of an electrolyte in an existing high-voltage (3.0-4.5V) battery, the invention provides the electrolyte and the battery comprising the electrolyte, wherein the stability of the electrolyte can be improved and the cycle performance of the battery can be improved by using a first additive in the electrolyte.
The purpose of the invention is realized by the following technical scheme:
an electrolytic solution comprising an organic solvent, an electrolyte salt, and a functional additive, wherein the functional additive comprises a first additive selected from at least one of compounds represented by formula (1):
Figure BDA0003641553460000021
in the formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, are selected from the group consisting of unsubstituted or optionally substituted by one, two or moreR a Substituted C 1-10 Alkylene radical, C 6-12 Arylene, -C 1-10 alkylene-C (═ O) -O-C 1-10 Alkylene-; each R a Identical or different, independently of one another, from halogen, C 1-10 An alkyl group.
An electrolyte according to the invention, formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from the group consisting of unsubstituted or optionally substituted by one, two or more R a Substituted C 1-6 Alkylene radical, C 6-8 Arylene, -C 1-6 alkylene-C (═ O) -O-C 1-6 Alkylene-; each R a Identical or different, independently of one another, from halogen, C 1-6 An alkyl group.
An electrolyte according to the invention, formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from the group consisting of unsubstituted or optionally substituted by one, two or more R a Substituted C 1-4 Alkylene, phenylene, -C 1-4 alkylene-C (═ O) -O-C 1-4 Alkylene-; each R a Identical or different, independently of one another, from halogen, C 1-4 An alkyl group.
An electrolyte according to the invention, formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from the group consisting of unsubstituted or optionally substituted by one, two or more R a substituted-CH 2 -、-CH 2 CH 2 -、-CH 2 CH 2 CH 2 -、-CH 2 CH(CH 2 ) -, o-, m-, p-and-phenylene, -CH 2 -C(＝O)-O-CH 2 -、-CH 2 CH 2 -C(＝O)-O-CH 2 CH 2 -; each R a Identical or different, independently of one another, from the group F, -CH 3 、-CH 2 CH 3 、-CH 2 CH 2 CH 3 、-CH(CH 3 )CH 3 。
According to the electrolyte of the present invention, the first additive is at least one selected from compounds represented by formulas (2) to (9):
Figure BDA0003641553460000022
Figure BDA0003641553460000031
according to the electrolyte of the invention, the mass of the first additive is 0.5 wt% to 2.5 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.2 wt%, 1.3 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.4 wt%, or 2.5 wt% of the total mass of the electrolyte.
In the electrolyte according to the present invention, the first additive may be commercially available or may be prepared by a method known in the art.
According to the electrolyte, the functional additive also comprises a second additive, and the second additive is selected from at least one of alkyl polynitrile compounds.
According to the electrolyte of the present invention, the alkyl polynitrile compound has a chemical formula represented by formula (10):
R-(CN) n formula (10)
In the formula (10), R is selected from alkyl, and n is an integer of 3 or more.
According to the electrolyte of the invention, in formula (10), R is selected from C 3-8 Alkyl, for example selected from n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl or isomeric radicals thereof.
According to the electrolyte of the invention, in formula (10), n is 3 or 4.
According to the electrolyte of the invention, the alkylpolynitrile compound is selected from 1,3, 6-Hexanetrinitrile (HTCN).
According to the electrolyte of the invention, the mass of the second additive is 0.5 wt% to 4 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, 3 wt%, 3.4 wt%, 3.7 wt%, 3.9 wt% or 4 wt% of the total mass of the electrolyte.
The second additive may be commercially available or may be prepared by methods known in the art according to the electrolyte of the present invention.
According to the electrolytic solution of the present invention, the electrolyte salt is at least one selected from the group consisting of electrolyte lithium salts, electrolyte sodium salts, electrolyte potassium salts, electrolyte aluminum salts, electrolyte zinc salts, electrolyte magnesium salts, and the like.
According to the electrolyte of the invention, the electrolytic lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 ) Lithium difluorophosphate (LiPO) 2 F 2 ) One or more of lithium difluorooxalato borate (LiDFOB), lithium difluorosulfonimide (LiTFSI), lithium bistrifluoromethylsulfonimide, lithium difluorobis-oxalato phosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium tris (trifluoromethylsulfonyl) methide, or lithium bis (trifluoromethylsulfonyl) imide.
According to the electrolyte, the organic solvent is selected from carbonate and/or carboxylic ester, and the carbonate is selected from one or more of the following fluorinated or unsubstituted solvents: ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate; the carboxylic ester is selected from one or more of the following fluorinated or unsubstituted solvents: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, Propyl Propionate (PP), Ethyl Propionate (EP), methyl butyrate, ethyl n-butyrate.
According to the electrolyte of the invention, the functional additive further comprises a third additive, and the third additive is selected from at least one of the following compounds: 1, 3-propane sultone, 1, 3-propene sultone, succinonitrile, adiponitrile, glycerol trinitrile, lithium difluorooxalato borate, lithium difluorophosphate and lithium difluorooxalato phosphate.
According to the electrolyte of the invention, the mass of the third additive is 0-10 wt% of the total mass of the electrolyte, such as 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%.
The electrolyte according to the invention is used in batteries, for example in lithium ion batteries.
According to the electrolyte of the present invention, the electrolyte is a nonaqueous electrolyte.
The invention also provides a battery, which comprises the electrolyte.
According to the battery of the present invention, the battery further includes a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator.
According to the battery, the positive plate comprises a positive current collector and a positive active material layer coated on one side or two sides of the positive current collector, and the positive active material layer comprises a positive active material, a conductive agent and a binder.
According to the battery of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.
According to the battery, the mass percentage of each component in the positive active material layer is as follows: 80-99.8 wt% of positive electrode active material, 0.1-10 wt% of conductive agent and 0.1-10 wt% of binder.
Preferably, the positive electrode active material layer comprises the following components in percentage by mass: 90-99.6 wt% of positive electrode active material, 0.2-5 wt% of conductive agent and 0.2-5 wt% of binder.
According to the battery, the mass percentage of each component in the negative electrode active material layer is as follows: 80-99.8 wt% of negative electrode active material, 0.1-10 wt% of conductive agent and 0.1-10 wt% of binder.
Preferably, the negative electrode active material layer comprises the following components in percentage by mass: 90-99.6 wt% of negative electrode active material, 0.2-5 wt% of conductive agent and 0.2-5 wt% of binder.
According to the battery of the present invention, the conductive agent is at least one selected from the group consisting of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, and metal powder.
According to the battery of the present invention, the binder is selected from at least one of sodium carboxymethylcellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
According to the battery of the present invention, the anode active material includes a carbon-based anode material.
According to the battery, the carbon-based negative electrode material comprises at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon and soft carbon.
According to the battery of the present invention, the negative electrode active material may further include a silicon-based negative electrode material.
According to the battery, the silicon-based negative electrode material is selected from at least one of nano silicon (Si), silicon-oxygen negative electrode material (SiOx (0< x <2)) and silicon-carbon negative electrode material.
According to the battery, the positive active material is selected from one or more of transition metal lithium oxide, lithium iron phosphate and lithium manganate; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O 2 Wherein x is more than or equal to-0.1 and less than or equal to 1; y 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 y + z is more than or equal to 0 and less than or equal to 1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr.
According to the battery of the present invention, the battery further satisfies the following conditions:
17≥X 2 +Y 2 -Z≥1
wherein Z is the specific surface area of the positive electrode active material and has a unit of m 2 (ii)/g; x is the mass percentage content of the first additive in the electrolyte, and the unit is wt%; and Y is the mass percentage content of the second additive in the electrolyte, and the unit is wt%.
According to the battery, 0.5 wt% to Xwt wt% to 2.5 wt%; 0.5 percent to Ywt percent to 4 percent by weight. Namely X is more than or equal to 0.5 and less than or equal to 2.5; y is more than or equal to 0.5 and less than or equal to 4.
The invention has the beneficial effects that:
the invention provides an electrolyte and a lithium ion battery comprising the same, wherein the electrolyte comprises a first additive, a phosphate ester functional group contained in the first additive is easy to form a phosphorus-rich protective film on a high-voltage positive electrode, the problem of too fast side reaction of the electrolyte at a positive electrode interface under high voltage can be inhibited, the positive electrode interface of the battery can be well protected, the stability of the electrolyte and the interface of the electrolyte can be obviously improved, the consumption of the electrolyte and the damage of a positive electrode structure in the battery circulation process are reduced, and the circulation performance of the battery is obviously improved.
On the basis, a second additive is further added, a nitrile functional group contained in the first additive and a nitrile functional group in the second additive are coordinated with transition metal ions to inhibit the oxidation capability of the transition metal on the surface of the anode, and the film forming and coordination effects can achieve a synergistic effect and remarkably improve the high-voltage performance of the battery; in addition, redundant nitrile functional groups can be coordinated with transition metal ions at some anode positions where films are not formed, so that the high-voltage performance of the battery is further improved, and the effect of improving the cycle performance is achieved. Meanwhile, the corresponding film forming and coordination effects can also improve the furnace temperature performance of the battery and increase the safety performance of the battery at high temperature.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is understood that the battery of the present invention includes a negative electrode tab, an electrolyte, a positive electrode tab, a separator, and an exterior package. The battery of the invention can be obtained by stacking the positive plate, the isolating film and the negative plate to obtain the battery core or stacking the positive plate, the isolating film and the negative plate, then winding to obtain the battery core, placing the battery core in an outer package, and injecting electrolyte into the outer package.
Examples 1 to 10 and comparative examples 1 to 3
The lithium ion batteries of examples 1 to 10 and comparative examples 1 to 3 were prepared by the following steps:
1) preparation of positive plate
The positive electrode active material lithium cobaltate (LiCoO) 2 ) Mixing polyvinylidene fluoride (PVDF), SP (super P) and Carbon Nano Tubes (CNT) according to a mass ratio of 96:2:1.5:0.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until a mixed system becomes positive active slurry with uniform fluidity; uniformly coating the positive active slurry on two surfaces of the aluminum foil; and drying the coated aluminum foil, and then rolling and slitting to obtain the required positive plate.
2) Preparation of negative plate
Mixing artificial graphite serving as a negative electrode active material, silicon monoxide, sodium carboxymethylcellulose (CMC-Na), styrene butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) according to a mass ratio of 79.5:15:2.5:1.5:1:0.5, adding deionized water, and obtaining negative electrode active slurry under the action of a vacuum stirrer; uniformly coating the negative active slurry on two surfaces of a copper foil; and (3) airing the coated copper foil at room temperature, then transferring the copper foil to an oven at 80 ℃ for drying for 10h, and then carrying out cold pressing and slitting to obtain the negative plate.
3) Preparation of the electrolyte
In a glove box filled with argon (H) 2 O<0.1ppm，O 2 <0.1ppm) was added, EC/PC/DEC/PP was mixed in a mass ratio of 10/20/40/30Homogenizing, then adding 1mol/L of fully dried lithium hexafluorophosphate (LiPF) rapidly 6 ) After dissolution, 16 wt% of fluoroethylene carbonate, 2 wt% of 1, 3-propane sultone, 1.5 wt% of adiponitrile, a compound shown in formula (2) or a compound shown in formula (4), and 1,3, 6-hexanetricarbonitrile (the specific dosage is shown in table 1) are added, the mixture is uniformly stirred, and the required electrolyte is obtained after moisture and free acid detection are qualified.
4) Preparation of lithium ion battery
Stacking the positive plate in the step 1), the negative plate in the step 2) and the isolation film in the order of the positive plate, the isolation film and the negative plate, and then winding to obtain a battery cell; placing the battery cell in an aluminum foil package, injecting the electrolyte in the step 3) into the package, and performing vacuum packaging, standing, formation, shaping, sorting and other processes to obtain the lithium ion battery. The battery of the invention has a charge-discharge range of 3.0-4.5V.
The lithium ion batteries obtained in the examples and comparative examples were subjected to 25 ℃ cycle performance test and 45 ℃ cycle performance test, and oven temperature performance test, and the test results are shown in tables 2 and 3.
1) Cycle performance test at 25 deg.C
The batteries in the table 1 are subjected to charge-discharge circulation within a charge-discharge cut-off voltage range at 25 ℃ according to the multiplying power of 1C, the discharge capacity in the 1 st week is x1 mAh, and the discharge capacity in the N week is y1 mAh; the capacity at the N-th week was divided by the capacity at the 1 st week to obtain the cycle capacity retention ratio R1 at the N-th week, y1/x1, and the number of cycle cycles corresponding to 80% of the cycle capacity retention ratio R1 was recorded.
2)45 ℃ cycle performance test
The batteries in the table 1 are subjected to charge-discharge circulation within a charge-discharge cut-off voltage range at the temperature of 45 ℃ according to the multiplying power of 1C, the discharge capacity in the 1 st week is x2 mAh, and the discharge capacity in the N week is y2 mAh; the capacity at the N-th week was divided by the capacity at the 1 st week to obtain the cycle capacity retention ratio R2 at the N-th week, y2/x2, and the number of cycle cycles corresponding to 80% of the cycle capacity retention ratio R2 was recorded.
3) Furnace temperature Performance test
The cells of table 1 were charged to full charge at normal temperature with standard charging conditions (1C standard charge to limit voltage, cut off 0.025C); the full-power battery cell (with the code-sprayed surface facing downwards and the pit surface facing upwards) is placed in an oven in a lying mode, the temperature of the oven is increased to (135 +/-2) DEG C at the speed of (5 +/-2) DEG C/min and is kept for 60min, the middle temperature of the battery cell (the pit surface) body needs to be monitored in the testing process, and whether the battery is subjected to fire and explosion phenomena or not is observed.
Table 1 compositions of electrolyte additives and specific surface areas of positive electrode active materials in lithium ion batteries of examples and comparative examples
Figure BDA0003641553460000091
Table 2 results of cycle performance test of lithium ion batteries of examples and comparative examples
Figure BDA0003641553460000092
Figure BDA0003641553460000101
Table 3 test results of furnace temperature performance of lithium ion batteries of examples and comparative examples
Whether the furnace temperature passes
Comparative example 1 Whether or not
Comparative example 2 Whether or not
Comparative example 3 Whether or not
Example 1 Is that
Example 2 Is that
Example 3 Is that
Example 4 Is that
Example 5 Is that
Example 6 Is that
Example 7 Is that
Example 8 Is that
Example 9 Whether or not
Example 10 Whether or not
As can be seen from table 2, the number of cycles at 25c and 45 c of example 9, to which the first additive was added, was greater than those of comparative examples 1-2, to which the first additive was not added, indicating that the introduction of the first additive improved the high-temperature and normal-temperature cycle performance of the battery.
Further, the number of cycles at 25 ℃ and the number of cycles at 45 ℃ of comparative examples 1-2 and examples 9, in which the first additive and the second additive are not added simultaneously, are both significantly less than those of examples 1-8, in which a proper amount of the first additive and the second additive are added simultaneously, which proves that the first additive and the second additive can synergistically improve the high-voltage performance of the battery, and the oxidation of cobalt on the surface of the positive electrode to the electrolyte in the high-voltage charge-discharge process can be better resisted through the film forming and coordination effects of the first additive and the second additive, so that the effect of improving the cycle performance is achieved.
Further, it can be seen from example 10 that when the amounts of the first additive and the second additive added and the specific surface area of the positive electrode active material are not 17. gtoreq.X 2 +Y 2 When the Z is within the range of-Z.gtoreq.1, the addition of excessive amounts of the first additive and the second additive no longer has a significant effect on the cycle performance of the battery, but may deteriorate the cycle performance of the battery because the specific surface area of the positive electrode active material cannot coordinate excessive amounts of the nitrile compound, which is detrimental to the formation of a negative electrode SEI film and thus to the cycle of the lithium ion battery.
Further, it can be seen from examples 1, 2, 3 and 8 that the improvement of the cycle performance at normal and high temperatures becomes stronger and weaker as the amount of the first additive added increases, which means that the improvement of the cycle performance is facilitated by the addition of a proper amount, and the side effect on the SEI film starts to become more significant when the amount is excessively added.
It can be seen from examples 2 and 4 that the compounds represented by formulas (2) and (4) have the same effect of improving cycle performance at normal and high temperatures, and the compound represented by formula (4) has a slightly weaker improving effect than the compound represented by formula (2), probably because the steric hindrance of the compound represented by the unit molecular formula (4) after fluorination greatly affects the coordination between the nitrile group functional group and the transition metal ion.
Examples 5 to 7 show that, while the amount of the first additive was maintained, the amount of 1,3, 6-hexanetricarbonitrile added was increased in a gradient manner, and the improvement in the normal-temperature and high-temperature cycle properties of the battery was enhanced before it was weakened, which indicates that the addition of 1,3, 6-hexanetricarbonitrile in a proper amount is advantageous for better protection of the positive electrode, thereby improving the cycle properties, and that the side effects on the SEI film began to become more pronounced when the additive amount was excessively increased.
As can be seen from Table 3, when the first additive is used in combination with 1,3, 6-hexanetricarbonitrile, the relation of 17. gtoreq.X is satisfied between the amount of the additive and the specific surface area of the positive electrode active material 2 +Y 2 When Z.gtoreq.1, the oven temperature test was passed for all of examples 1-8, while the oven temperature test was not passed for all of the batteries of comparative examples 1-3 and examples 9-10.
In conclusion, the electrolyte added with the first additive and the second additive can form a protective layer with a synergistic coordination effect on the surface of the positive electrode, the protective layer can reduce the oxidation capacity of the surface of the positive electrode to the electrolyte, can obviously improve the stability of the electrolyte and the interface of the electrolyte, can reduce the consumption of the electrolyte and the damage of the positive electrode structure in the circulation process of the lithium ion battery, and can obviously improve the circulation performance of the lithium ion battery. Since the interface side reaction is suppressed, the furnace temperature performance of the battery can also be improved.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. An electrolyte, comprising an organic solvent, an electrolyte salt, and a functional additive, wherein the functional additive comprises a first additive selected from at least one compound represented by formula (1):
Figure FDA0003641553450000011
in the formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from the group consisting of unsubstituted or optionally substituted by one, two or more R a Substituted C 1-10 Alkylene radical, C 6-12 Arylene, -C 1-10 alkylene-C (═ O) -O-C 1-10 Alkylene-; each R a Identical or different, independently of one another, from halogen, C 1-10 An alkyl group.
2. The electrolyte according to claim 1, wherein in formula (1), R is 1 、R 2 、R 3 Identical or different, independently of one another, from the group consisting of unsubstituted or optionally substituted by one, two or more R a Substituted C 1-6 Alkylene radical, C 6-8 Arylene, -C 1-6 alkylene-C (═ O) -O-C 1-6 Alkylene-; each R a Identical or different, independently of one another, from halogen, C 1-6 An alkyl group.
3. The electrolyte of claim 2, wherein the first additive is at least one selected from compounds represented by formulas (2) to (9):
Figure FDA0003641553450000012
Figure FDA0003641553450000021
4. the electrolyte of any one of claims 1-3, wherein the mass of the first additive is 0.5 wt% to 2.5 wt% of the total mass of the electrolyte.
5. The electrolyte of any one of claims 1-3, wherein the functional additive further comprises a second additive selected from at least one of alkyl polynitrile based compounds.
6. The electrolyte of claim 5, wherein the alkylpolynitrile compound has the formula of formula (10):
R-(CN) n formula (10)
In the formula (10), R is selected from alkyl, and n is an integer of 3 or more.
7. The electrolyte of claim 6, wherein the alkyl polynitrile compound is selected from 1,3, 6-Hexanetrinitrile (HTCN).
8. The electrolyte of claim 5, wherein the second additive is present in an amount of 0.5 wt% to 4 wt% based on the total weight of the electrolyte.
9. A battery comprising the electrolyte of any one of claims 1-8.
10. The battery according to claim 9, further comprising a positive electrode sheet containing a positive electrode active material, a negative electrode sheet containing a negative electrode active material, and a separator;
the battery also satisfies the following conditions:
17≥X 2 +Y 2 -Z≥1
wherein Z is the specific surface area of the positive electrode active material and has a unit of m 2 (ii)/g; x is the mass percentage content of the first additive in the electrolyte, and the unit is wt%; and Y is the mass percentage content of the second additive in the electrolyte, and the unit is wt%.
CN202210521055.1A 2022-05-12 2022-05-12 Electrolyte and battery comprising same Pending CN114899476A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115579507A (en) * 2022-10-21 2023-01-06 江苏正力新能电池技术有限公司 Secondary battery and preparation method thereof, battery pack and power utilization device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115579507A (en) * 2022-10-21 2023-01-06 江苏正力新能电池技术有限公司 Secondary battery and preparation method thereof, battery pack and power utilization device

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