CN115602925A - Electrolyte and battery comprising same - Google Patents

Electrolyte and battery comprising same Download PDF

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Publication number
CN115602925A
CN115602925A CN202211276013.2A CN202211276013A CN115602925A CN 115602925 A CN115602925 A CN 115602925A CN 202211276013 A CN202211276013 A CN 202211276013A CN 115602925 A CN115602925 A CN 115602925A
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electrolyte
additive
battery
positive electrode
lithium
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邱亚明
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
    • H01M10/056—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
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • 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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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides an electrolyte and a battery comprising the electrolyte. The first additive phosphorus-containing trinitrile compound and the second additive sulfonyl fluoride compound can act together, and form CEI rich in LiF inorganic substances and P inorganic substances on the positive electrode to isolate the positive electrode and electrolyte, so that the side reaction of the electrolyte is reduced, and the loss of active substances of the positive electrode of the battery under the high-temperature condition is reduced, thereby improving the stability of the battery and remarkably improving the high-temperature and high-pressure performance of the battery. In conclusion, through the synergistic effect of the phosphorus-containing trinitrile compound as the first additive and the sulfonyl fluoride compound as the second additive, protective films can be formed on the positive electrode and the negative electrode, so that the oxidative decomposition and reductive decomposition of the electrolyte are inhibited, the stability of the electrolyte on the positive electrode and the negative electrode is obviously improved, and the high-temperature and high-pressure performance of the battery is improved.

Description

Electrolyte and battery comprising same
Technical Field
The invention belongs to the technical field of electrolyte, and particularly relates to electrolyte and a battery comprising the electrolyte.
Background
Lithium ion batteries have a series of advantages of high energy density, long cycle life and the like, and therefore, as high-quality power supplies, lithium ion batteries are widely applied to consumer electronics products such as mobile phones and notebook computers, and simultaneously, with the vigorous development of electric automobiles, the demand of lithium ion batteries as power batteries thereof is greatly increased. With the development of science and technology, lithium ion batteries with higher energy density are needed, so that the ever-increasing long-endurance requirement of people is better met.
One key path for increasing the energy density of lithium ion batteries is to increase the battery voltage, and 4.5V and higher voltages become key points and hot spots for developing high-energy density lithium ion batteries. High temperature cycling and high temperature storage of high voltage lithium ion batteries present major challenges. In order to further improve the performance of the battery under high voltage, whether a novel efficient functional electrolyte additive can be developed becomes a key factor.
Under high temperature and high pressure, the electrolyte is easily oxidized and decomposed on the positive electrode side, the electrolyte is continuously consumed, and a large amount of by-products are generated, so that the battery performance is rapidly deteriorated. Wherein, the high valence transition metal on the surface of the anode is the main reaction site for catalytic oxidative decomposition. The film forming additive can be preferentially oxidized and decomposed by an electrolyte solvent, and meanwhile, a layer of passivation protective film can be formed by a decomposition product, so that the high-temperature and high-pressure performance of the battery is improved. In addition, the catalytic oxidation of the transition metal to the solvent can be reduced through the coordination of the additive molecules and the transition metal.
Disclosure of Invention
In order to improve the high-temperature cycle and high-temperature storage performance of a high-voltage lithium ion battery with the voltage of more than 4.5V, the invention provides an electrolyte and a battery comprising the electrolyte, wherein functional additives in the electrolyte comprise a phosphorus-containing trinitrile compound and a sulfonyl fluoride compound which can generate synergistic action and respectively form protective films on a positive electrode and a negative electrode, so that the oxidative decomposition and the reductive decomposition of the electrolyte are inhibited, the stability of the electrolyte on the positive electrode and the negative electrode is obviously improved, and the high-temperature cycle and high-temperature storage performance of the battery under the high voltage are improved.
The purpose of the invention is realized by the following technical scheme:
an electrolyte comprising an organic solvent, an electrolyte salt, and a functional additive, wherein the functional additive comprises a first additive and a second additive, and the first additive is selected from a group consisting of phosphorus-containing trinitrile compounds; the second additive is selected from sulfonyl fluoride compounds.
According to an embodiment of the invention, the first additive is selected from at least one of the compounds represented by formula (1):
Figure BDA0003896680850000021
in the formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from H, unsubstituted or optionally substituted by one, two or more R a Substituted C 1-5 An alkylene group; each R a Identical or different, independently of one another, from halogen, C 1-5 Alkyl, -C (= O) -C 1-5 Alkyl, -C (= O) -O-C (= O) -C 1-5 Alkyl radical, C 6-14 Aryl, 5-14 membered heteroaryl.
According to an embodiment of the present invention, in formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from H, unsubstituted or optionally substituted by one, two or more R a Substituted C 1-5 An alkylene group; each R a Identical or different, independently of one another, from halogen, C 1-5 Alkyl, -C (= O) -C 1-5 Alkyl, -C (= O) -O-C (= O) -C 1-5 Alkyl radical, C 6-8 Aryl, 5-6 membered heteroaryl.
According to an embodiment of the present invention, in formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from H, unsubstituted or optionally substituted by one, two or more R a Substituted C 1-3 An alkylene group; each R a Identical or different, independently of one another, from halogen, C 1-3 An alkyl group.
According to an embodiment of the present invention, the first additive is at least one selected from compounds represented by the following formulae (2) to (7):
Figure BDA0003896680850000031
according to embodiments of the present invention, the first additive may be prepared by methods known in the art or may be commercially available.
According to an embodiment of the invention, the first additive is added in an amount of 0.1wt% to 4.0wt%, such as 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.3wt%, 1.5wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.3wt%, 3.5wt%, 3.8wt%, or 4wt% of the total mass of the electrolyte.
According to an embodiment of the present invention, the second additive is selected from at least one of perfluoroethanesulfonyl fluoride, perfluoropropanesulfonyl fluoride and perfluorobutanesulfonyl fluoride.
According to an embodiment of the invention, the second additive is added in an amount of 0.1wt% to 2.0wt%, such as 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.3wt%, 1.5wt%, 1.6wt%, 1.8wt%, 2wt% of the total mass of the electrolyte.
According to an embodiment of the invention, the electrolyte salt is selected from electrolyte lithium salts.
According to an embodiment of the present invention, the electrolyte 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 an embodiment of the present invention, the electrolyte salt is added in an amount of 11wt% to 18wt%, for example 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt% or 18wt% of the total mass of the electrolyte.
According to an embodiment of the present invention, the organic solvent is selected from carbonates and/or carboxylic esters, the carbonates being selected from one or several 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 an embodiment of the present invention, the functional additive further comprises a third additive selected from at least one of the following compounds: fluoroethylene carbonate, 1, 3-propane sultone, 1, 3-propene sultone, succinonitrile, adiponitrile, lithium difluorooxalato borate, lithium difluorophosphate, lithium difluorodioxaoxalato phosphate. After the third additive is added, the third additive can participate in the generation of an SEI film and a CEI film at the initial formation stage, so that the protection effect on the positive and negative electrodes is achieved, and meanwhile, the damaged interface film can be continuously repaired at the later cycle stage, so that the electrochemical performance of the battery is improved.
According to an embodiment of the invention, the third additive is added in an amount of 0 to 15wt%, such as 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt% of the total mass of the electrolyte.
According to an embodiment of the present invention, the electrolyte is used for a high voltage battery, illustratively, a high voltage lithium cobalt oxide battery, a high voltage ternary battery, or a high voltage lithium-rich manganese-based battery. Preferably, the electrolyte is used for a high voltage lithium cobalt oxide battery.
The invention also provides a battery, which comprises the electrolyte.
According to an embodiment of the invention, the battery is a lithium ion battery.
According to an embodiment 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 an embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both surfaces of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.
According to an embodiment 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, the negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder.
According to the embodiment of the invention, the positive electrode active material layer comprises the following components in percentage by mass: 80-99.8 wt% of positive 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 to 99.6 weight percent of anode active substance, 0.2 to 5 weight percent of conductive agent and 0.2 to 5 weight percent of binder.
According to the embodiment of the invention, the anode active material layer comprises the following components in percentage by mass: 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 to 99.6 weight percent of negative electrode active material, 0.2 to 5 weight percent of conductive agent and 0.2 to 5 weight percent of binder.
According to an embodiment 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, the binder is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene and polyethylene oxide.
According to an embodiment of the present invention, the anode active material includes a carbon-based anode material.
According to an embodiment of the present invention, the carbon-based negative electrode material is selected from at least one of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon and soft carbon.
According to an embodiment of the present invention, the anode active material further includes a silicon-based anode material.
According to the embodiment of the invention, the silicon-based anode material is selected from at least one of nano-silicon, silicon-oxygen anode materials (SiOx (0 < -x < -2)) or silicon-carbon anode materials.
According to the embodiment of the invention, the mass ratio of the carbon-based anode material and the silicon-based anode material is 10.
According to the embodiment of the invention, the positive active material is selected from one or more of transition metal lithium oxide and lithium-rich manganese-based material; the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O 2 Wherein-0.1 is less than or equal to x is 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 an embodiment of the present invention, the charge cut-off voltage of the battery is 4.5V or more.
Definition and description of terms
Wherein "more" means three or more.
The term "halogen" refers to F, cl, br and I. In other words, F, cl, br, and I may be described as "halogen" in the present specification.
The term "C 1-5 Alkyl "is understood to preferably mean a straight-chain or branched, saturated monovalent hydrocarbon radical having from 1 to 5 carbon atoms. Specifically, "C 1-5 Alkyl "is to be understood as preferredRepresents a straight or branched chain saturated monovalent hydrocarbon group having 1,2, 3, 4 or 5 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-ethylpropyl, 1, 2-dimethylpropyl, neopentyl, 1-dimethylpropyl or the like or an isomer thereof. In particular, the radicals have 1,2 or 3 carbon atoms ("C) 1-3 Alkyl), such as methyl, ethyl, n-propyl or isopropyl.
The term "C 6-14 Aryl "is understood as preferably meaning a monocyclic, bicyclic or tricyclic hydrocarbon ring of monovalent or partial aromaticity having from 6 to 14 carbon atoms. The term "C 6-14 Aryl "is understood as preferably meaning a monocyclic, bicyclic or tricyclic hydrocarbon ring of monovalent or partial aromaticity having 6, 7, 8, 9, 10, 11, 12, 13 or 14 carbon atoms (" C) 6-14 Aryl "), in particular a ring having 6 carbon atoms (" C 6 Aryl "), such as phenyl; or biphenyl, or is a ring having 9 carbon atoms ("C 9 Aryl), such as indanyl or indenyl, or a ring having 10 carbon atoms ("C) 10 Aryl radicals), such as tetralinyl, dihydronaphthyl or naphthyl, or rings having 13 carbon atoms ("C 13 Aryl radicals), such as the fluorenyl radical, or a ring having 14 carbon atoms ("C) 14 Aryl), such as anthracyl.
The term "5-14 membered heteroaryl" is understood to include such monovalent monocyclic, bicyclic or tricyclic aromatic ring systems: having 5 to 14 ring atoms and containing 1 to 4 heteroatoms independently selected from N, O and S. The term "5-14 membered heteroaryl" is understood to include such monovalent monocyclic, bicyclic or tricyclic aromatic ring systems: which has 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 ring atoms, in particular 5 or 6 or 9 or 10 carbon atoms, and which comprises 1 to 5, preferably 1 to 3, heteroatoms each independently selected from N, O and S and, in addition, can in each case be benzo-fused. In particular, heteroaryl is selected from thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl and the like and their benzo derivatives, such as benzofuranyl, benzothienyl, benzoxazolyl, benzoisoxazolyl, benzimidazolyl, benzotriazolyl, indazolyl, indolyl, isoindolyl and the like; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, and the like, and benzo derivatives thereof, such as quinolyl, quinazolinyl, isoquinolyl, and the like; or azocinyl, indolizinyl, purinyl and the like and benzo derivatives thereof; or cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, pteridinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, and the like.
The invention has the beneficial effects that:
the invention provides an electrolyte and a battery comprising the same. The phosphorus-containing trinitrile compound as the first additive can generate oxidative decomposition reaction in the charging and discharging processes, and alkyl nitrile chain segments (-R-CN, R is defined as R) 1 、R 2 Or R 3 ) The nitrile functional group in the electrolyte is coordinated with the transition metal, so that the oxidation of the transition metal on the electrolyte is reduced. The sulfonyl fluoride compound serving as the second additive can form a good SEI film at the negative electrode for protection, and meanwhile, the phosphotrienitrile compound serving as the first additive and the sulfonyl fluoride compound serving as the second additive can act together to form a CEI film rich in LiF inorganic substances and P inorganic substances at the positive electrode to isolate the positive electrode from electrolyte, so that the side reaction of the electrolyte is reduced, and the loss of active substances of the positive electrode under a high-temperature condition is reduced, thereby improving the stability of the battery and remarkably improving the high-temperature and high-pressure performance of the battery. In conclusion, through the synergistic effect of the phosphorus-containing trinitrile compound as the first additive and the sulfonyl fluoride compound as the second additive, protective films can be formed on the positive electrode and the negative electrode, so that the oxidative decomposition and reductive decomposition of the electrolyte are inhibited, the stability of the electrolyte on the positive electrode and the negative electrode is obviously improved, and the high-temperature and high-pressure performance of the battery is improved.
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 the description of the present invention, it should be noted that the terms "first", "second", "third", etc. are used for descriptive purposes only and do not indicate or imply relative importance.
In order to make the objects, technical solutions and advantages of the present invention more apparent, 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 obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to 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 can be obtained by stacking the positive plate, the isolating membrane and the negative plate to obtain the battery core or stacking the positive plate, the isolating membrane 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 7 and comparative examples 1 to 3
The batteries of examples 1 to 7 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; uniformly coating the positive active slurry on two surfaces of the aluminum foil; coating the aluminum foilDrying, rolling and cutting to obtain the required positive plate.
2) Preparation of cathode plate
Mixing artificial graphite serving as a negative electrode active material, sodium carboxymethylcellulose (CMC-Na), styrene butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) according to a mass ratio of 1.5; 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 <0.1 ppm), EC/PC/DEC/PP was mixed uniformly in a mass ratio of 10/20/40/30, and then 1mol/L of well-dried lithium hexafluorophosphate (LiPF) was rapidly added thereto 6 ) After the electrolyte is dissolved, 2wt% of 1, 3-propane sultone, 7wt% of fluoroethylene carbonate, 2wt% of succinonitrile, 2wt% of 1,3, 6-hexanetrinitrile and the additive described in the table 1 are added, the mixture is uniformly stirred, and the required electrolyte is obtained after the moisture and the free acid are detected to be qualified.
4) Preparation of the 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 core in an aluminum foil package, injecting the electrolyte obtained in the step 3) into the package, and carrying out vacuum packaging, standing, formation, shaping, sorting and other processes to obtain the battery. The battery of the invention has a charge-discharge range of 3.0-4.5V.
The batteries obtained in examples and comparative examples were subjected to a 60 ℃ high-temperature storage performance test and a 45 ℃ cycle performance test, respectively, and the test results are shown in table 2.
1) 60 ℃ storage Performance test
The batteries in table 1 were charged at 25 ℃ to a cut-off voltage at a rate of 1C, and a cut-off current of 0.025C, and left to stand for 5min, and the thickness of the lithium ion battery (here, the thickness before storage) was measured. Opening the fully charged battery cell/battery at (60 +/-2) DEG C for 35 days, storing for 35 days, opening the battery cell/battery at room temperature for 2 hours, measuring the cold thickness after storage, and calculating the thickness expansion rate of the lithium ion battery:
thickness expansion rate = [ (thickness after storage-thickness before storage)/thickness before storage ] × 100%.
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 measured to be x2mAh, and the discharge capacity in the Nth circle is measured to be y2mAh; the capacity at the nth week was divided by the capacity at the 1 st week to obtain the cycle capacity retention ratio R2= y2/x2 at the nth week, and when the cycle capacity retention ratio R2 decreased to 80% or less, the number of cycle weeks at that time was recorded.
TABLE 1 composition of electrolyte additive in batteries of examples and comparative examples
Figure BDA0003896680850000101
Table 2 results of performance test of batteries of examples and comparative examples
Figure BDA0003896680850000111
As can be seen from Table 2, the expansion rate of the storage thickness at 60 ℃ of the comparative example 1 without adding the phosphorus-containing trinitrile compound and the sulfonyl fluoride compound is obviously greater than that of other groups, and the retention rate of the circulation capacity at 45 ℃ of 80% of the circulation turns is obviously less than that of other groups. Compared with the groups of the comparative example 2 and the comparative example 3, which are added with the phosphorus-containing trinitrile compound or the sulfonyl fluoride compound separately, the expansion rate of the thickness at 60 ℃ storage thickness is obviously greater than that of the groups of the examples 1 to 7, and the cycle capacity retention rate at 45 ℃ of 80 percent is also obviously less than that of the groups of the examples 1 to 7. From examples 1 to 4, it is understood that when the phosphotrienitrile compound and the sulfonyl fluoride compound are added simultaneously, the thickness expansion rate of 35 days after storage at 60 ℃ is gradually reduced with the increase of the addition amount of the phosphotrienitrile compound, and the cycle capacity retention rate at 45 ℃ is increased first and then reduced after 80% of cycle number. This is because the storage performance is improved as the amount of the phosphorus-containing trinitrile compound added is increased, and the protection of the positive electrode is improved, but the battery resistance is excessively increased by a large amount of the phosphorus-containing trinitrile compound, which adversely deteriorates the cycle performance of the battery. It can be seen from examples 5 to 7 that the phosphorus-containing trinitrile compounds of different structures selected in the present application still have the same improved high-temperature storage and high-temperature cycle properties.
In conclusion, through the synergistic effect of the phosphorus-containing trinitrile compound as the first additive and the sulfonyl fluoride compound as the second additive, protective films can be formed on the positive electrode and the negative electrode, so that the oxidative decomposition and reductive decomposition of the electrolyte are inhibited, the stability of the electrolyte on the positive electrode and the negative electrode is obviously improved, and the high-temperature and high-pressure performance of the battery is 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 without departing from the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. An electrolyte, characterized in that the electrolyte comprises an organic solvent, an electrolyte salt and a functional additive, wherein the functional additive comprises a first additive and a second additive, and the first additive is selected from a group of phosphorus-containing trinitrile compounds; the second additive is selected from sulfonyl fluoride compounds.
2. The electrolyte of claim 1, wherein the first additive is selected from at least one compound represented by formula (1):
Figure FDA0003896680840000011
in the formula (1), R 1 、R 2 、R 3 Identical or different, independently of one another, from H, unsubstituted or optionally substituted by one, two or more R a Substituted C 1-5 An alkylene group; each R a Identical or different, independently of one another, from halogen, C 1-5 Alkyl, -C (= O) -C 1-5 Alkyl, -C (= O) -O-C (= O) -C 1-5 Alkyl radical, C 6-14 Aryl, 5-14 membered heteroaryl.
3. The electrolyte according to claim 2, wherein in formula (1), R is 1 、R 2 、R 3 Identical or different, independently of one another, from H, unsubstituted or optionally substituted by one, two or more R a Substituted C 1-5 An alkylene group; each R a Identical or different, independently of one another, from halogen, C 1-5 Alkyl, -C (= O) -C 1-5 Alkyl, -C (= O) -O-C (= O) -C 1-5 Alkyl radical, C 6-8 Aryl, 5-6 membered heteroaryl.
4. The electrolyte solution according to claim 2 or 3, wherein the first additive is at least one selected from compounds represented by the following formulas (2) to (7):
Figure FDA0003896680840000012
Figure FDA0003896680840000021
5. the electrolyte according to claim 1, wherein the first additive is added in an amount of 0.1 to 4.0wt% based on the total mass of the electrolyte.
6. The electrolyte of claim 1, wherein the second additive is selected from at least one of perfluoroethanesulfonyl fluoride, perfluoropropanesulfonyl fluoride, and perfluorobutanesulfonyl fluoride.
7. The electrolyte of claim 1 or 6, wherein the second additive is added in an amount of 0.1 to 2.0wt% based on the total mass of the electrolyte.
8. The electrolyte of claim 1, wherein the functional additive further comprises a third additive selected from at least one of the following compounds: fluoroethylene carbonate, 1, 3-propane sultone, 1, 3-propene sultone, succinonitrile, adiponitrile, lithium difluorooxalato borate, lithium difluorophosphate, lithium difluorodioxaoxalato phosphate; the addition amount of the third additive is 0-15 wt% of the total mass of the electrolyte.
9. A battery comprising the electrolyte of any one of claims 1-8.
10. The battery according to claim 9, wherein a charge cut-off voltage of the battery is 4.5V or more.
CN202211276013.2A 2022-10-18 2022-10-18 Electrolyte and battery comprising same Pending CN115602925A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024041150A1 (en) * 2022-08-25 2024-02-29 珠海冠宇电池股份有限公司 Electrolyte and battery comprising same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024041150A1 (en) * 2022-08-25 2024-02-29 珠海冠宇电池股份有限公司 Electrolyte and battery comprising same

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