CN117304098A - Electrolyte additive, preparation method thereof, electrolyte and lithium ion battery - Google Patents

Electrolyte additive, preparation method thereof, electrolyte and lithium ion battery Download PDF

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Publication number
CN117304098A
CN117304098A CN202311253766.6A CN202311253766A CN117304098A CN 117304098 A CN117304098 A CN 117304098A CN 202311253766 A CN202311253766 A CN 202311253766A CN 117304098 A CN117304098 A CN 117304098A
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electrolyte
lithium
additive
positive electrode
battery
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欧阳志鹏
李立飞
周龙捷
张瑞敏
黄建
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Langu Huzhou New Energy Technology Co ltd
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Langu Huzhou New Energy Technology 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
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/62—Oxygen or sulfur atoms
    • C07D213/70—Sulfur atoms
    • C07D213/71—Sulfur atoms to which a second hetero atom is attached
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/78—Carbon atoms having three bonds to hetero atoms, with at the most one bond to halogen, e.g. ester or nitrile radicals
    • C07D213/84—Nitriles
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D239/00—Heterocyclic compounds containing 1,3-diazine or hydrogenated 1,3-diazine rings
    • C07D239/02—Heterocyclic compounds containing 1,3-diazine or hydrogenated 1,3-diazine rings not condensed with other rings
    • C07D239/24—Heterocyclic compounds containing 1,3-diazine or hydrogenated 1,3-diazine rings not condensed with other rings having three or more double bonds between ring members or between ring members and non-ring members
    • C07D239/28—Heterocyclic compounds containing 1,3-diazine or hydrogenated 1,3-diazine rings not condensed with other rings having three or more double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, directly attached to ring carbon atoms
    • C07D239/32—One oxygen, sulfur or nitrogen atom
    • C07D239/38—One sulfur atom
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic System
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/10—Compounds having one or more C—Si linkages containing nitrogen having a Si-N linkage
    • 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

Abstract

The invention provides an electrolyte additive which can be decomposed on the surface of a positive electrode to form an interface film with high voltage stability and low impedance, so that the rapid conduction capability of lithium ions is improved. The electron withdrawing group contained in the additive structure can stabilize the transition metal on the surface of the positive electrode and inhibit the side reaction between the interface of the positive electrode and the electrolyte, so that the electrochemical performance of the battery under high voltage is improved. In addition, the SEI film with stable low impedance can be formed by decomposing the sulfonic acid group and the fluorine-containing group in the structure of the negative electrode, and high-temperature gas production is inhibited. The additive disclosed by the invention is applied to a lithium cobaltate battery, so that the cycle performance and the high-temperature performance of the battery under high voltage are greatly improved.

Description

Electrolyte additive, preparation method thereof, electrolyte and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte additive, a preparation method thereof, electrolyte and a lithium ion battery.
Background
Since the 21 st century, lithium ion batteries have been rapidly developed, and lithium batteries with higher energy density have become a future trend, and requirements for safety performance have become higher and higher while pursuing lithium ion batteries with higher energy density.
The lithium ion battery consists of a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the electrolyte is used as 'blood' of the battery and is used as an important carrier for transmitting lithium ions in the battery, and the lithium ion electrolyte is used as a medium in the charging and discharging process of the battery so as to realize reversible shuttle between the positive electrode and the negative electrode. However, intimate contact between the electrode (especially the positive electrode) and the electrolyte may cause a series of side reactions, which are one of the important causes of capacity degradation and structural degradation of the battery, thereby affecting the practical performance of the lithium ion battery. In particular, the electrolyte commonly used at high voltage/high temperature is easily oxidized and decomposed, so that the formed Solid Electrolyte Interface (SEI) film is unstable, and a stable positive electrode-electrolyte interface (CEI) film and SEI film are constructed between the positive electrode/negative electrode and the electrolyte by adding a functional film forming additive to the electrolyte, so that the electrochemical performance of the lithium ion battery can be effectively improved.
The positive film forming additives currently mainly used in lithium ion electrolyte can be divided into four types, including inorganic solid additives, electro-oxidative polymerization additives, phosphate additives and fluoro-organic additives. The solubility of the inorganic solid additive in the electrolyte is poor, the conductivity of the electrolyte can be negatively influenced, and meanwhile, the problem of uneven dispersion exists in practical application; the electrochemical oxidation polymerization type additive is easy to generate self-discharge phenomenon, the electrolyte and the positive electrode cannot be well isolated if the addition amount is too small, and the impedance is too large if the addition amount is too large; the phosphate additives and the fluoro-organic additives can form a relatively stable CEI film, so that the positive electrode material and the electrolyte are isolated to have a relatively good application prospect, however, the existing phosphate additives and fluoro-organic additives have single functions, and the improvement of the cycle performance of the lithium ion battery can not be well achieved. Therefore, the development of a multifunctional film-forming additive is of great significance.
Disclosure of Invention
In view of the above, the present invention aims to provide an electrolyte additive, a preparation method thereof, an electrolyte and a lithium ion battery. The electrolyte additive can be decomposed on the surface of the positive electrode to form an interface film with high voltage stability and low impedance, so that the quick conduction capability of lithium ions is improved, and meanwhile, the electron withdrawing group contained in the additive structure can stabilize the transition metal on the surface of the positive electrode and inhibit side reaction between the interface of the positive electrode and the electrolyte, so that the electrochemical performance of the battery under high voltage is improved. In addition, the structure contains sulfonic acid groups and fluorine-containing groups, so that stable low-impedance SEI films can be formed by decomposing the negative electrode, high-temperature gas production is inhibited, and the cycle performance and high-temperature performance of the lithium ion battery under high voltage are remarkably improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides an electrolyte additive having a structural formula shown in formula (a);
wherein R is 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C1-C4 saturated hydrocarbon group or C2-C4 unsaturated alkenyl group, X 1 、X 2 Or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not being simultaneously nitrogen atoms, R 3 、R 5 、R 6 Is one of a null, a hydrogen atom, a fluorine atom, a C1-C3 saturated hydrocarbon group or a cyano group, R 4 、R 7 Independently selected from hydrogen atom, fluorine atom, methyl group or cyano group.
Preferably, said R 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C2-C4 saturated hydrocarbon group or C3-C4 unsaturated alkenyl group,X 1 、X 2 or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not being simultaneously nitrogen atoms, R 3 、R 5 、R 6 Is one of a null, hydrogen atom, fluorine atom or cyano group, R 4 、R 7 Independently selected from hydrogen atoms or cyano groups.
Preferably, the compound represented by the structural formula a is at least one selected from the group consisting of compounds (I) to (VIII):
in a second aspect, the invention provides a method for preparing the electrolyte additive, comprising the following steps:
reacting the compound shown in the formula (B) with the compound shown in the formula (C) in the presence of a catalyst and a solvent to obtain the electrolyte additive;
the structural formulas of the formula (B) and the formula (C) are as follows:
wherein R is 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C1-C4 saturated hydrocarbon group or C2-C4 unsaturated alkenyl group, X 1 、X 2 Or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not being simultaneously nitrogen atoms, R 3 、R 5 、R 6 Is one of a null, a hydrogen atom, a fluorine atom, a C1-C3 saturated hydrocarbon group or a cyano group, R 4 、R 7 Independently selected from hydrogen atom, fluorine atom, methyl group or cyano group.
In a third aspect, the present invention provides an electrolyte comprising a lithium salt, a non-aqueous organic solvent, a first electrolyte additive;
the first electrolyte additive is the electrolyte additive according to any one of the technical schemes or the electrolyte additive prepared by the preparation method according to the technical scheme.
Preferably, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bistrifluoromethylsulfonyl imide, lithium bistrifluorosulfonyl imide, lithium bisoxalato borate, lithium difluorooxalato borate or lithium difluorodioxaato phosphate;
the non-aqueous organic solvent is selected from any one or more of organic ester solvents, ether solvents, sulfone solvents or nitrile solvents.
Preferably, the electrolyte further comprises a second electrolyte additive;
the second electrolyte additive is selected from one or more of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, ethylene sulfate, bis-ethylene sulfate, propylene sulfate, 1, 3-propane sultone, 1, 3-propenesulfonlactone, 1, 4-butanesulfonic acid lactone, 2, 4-butane sultone, phenyl methanesulfonate, methane disulfonic acid methylene ester, N-phenyl bis (trifluoromethanesulfonyl) imide, triallyl phosphate, tris (trimethylsilane) phosphite, trimethyl phosphite, triphenyl phosphite, tetramethyl methylenediphosphate, propargyl phosphate, (2-allylphenoxy) trimethyl silane, tris (trimethylsilane) borate, 1,3, 5-triallyl isocyanurate, isocyanatoethyl methacrylate, hexamethylene diisocyanate, terephthalyl diisocyanate, 2, 4-toluene diisocyanate, 1,3, 6-hexane tri-nitrile or 1, 2-bis (cyanoethoxy) ethane.
Preferably, the lithium salt accounts for 11-25% of the electrolyte by mass; the nonaqueous organic solvent accounts for 72-85% of the electrolyte by mass.
Preferably, the first electrolyte additive accounts for 0.1-2% of the electrolyte by mass; the sum of the first electrolyte additive and the second electrolyte additive accounts for 2-5% of the electrolyte by mass.
In a third aspect, the present invention provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte;
the electrolyte is any one of the above technical solutions.
Preferably, the material of the positive electrode is selected from any one of lithium cobaltate, lithium manganate, ternary nickel cobalt manganese lithium, nickel lithium manganate, lithium iron phosphate or lithium manganese iron phosphate;
the material of the negative electrode is selected from any one of artificial graphite, natural graphite, lithium titanate, metallic lithium, silicon-carbon composite material or silicon oxide;
the membrane is selected from polypropylene membrane or polyethylene membrane.
Preferably, the additive shown in the structural formula A is applied to battery electrolyte and can form a CEI interface film at the positive electrode of a battery; meanwhile, an SEI interface film can be formed on the negative electrode of the battery. Compared with the prior art, the invention has the beneficial effects that: the invention provides an electrolyte additive, which can be decomposed on the surface of a positive electrode to form an interfacial film with high voltage stability and low impedance, so that the rapid deintercalation capability of lithium ions is improved, the transition metal dissolution is relieved by a stable positive electrode interface, and the side reaction between the positive electrode interface and electrolyte is reduced, thereby improving the electrochemical performance of a lithium cobalt oxide battery under high voltage. In addition, sulfonic acid groups and fluorine-containing groups in the additive structure can be decomposed at the negative electrode in an induction way to form a stable SEI film with low impedance, and the SEI film rupture induced gas generation at high temperature is relieved. The additive disclosed by the invention is applied to a lithium cobaltate battery, so that the cycle performance and the high-temperature performance of the battery under high voltage are greatly improved.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s).
It should be understood that, in various embodiments of the present application, the sequence number of each process does not mean that the sequence of execution is sequential, and some or all of the steps may be executed in parallel or sequentially, where the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The invention provides a film forming additive which can be decomposed on the surface of a positive electrode to form a film under high pressure, so that the positive electrode is stabilized and forms a low-impedance interfacial film, the interface rapid lithium ion conducting performance is improved, functional groups contained in the structure can be complexed with transition metal on the surface of the positive electrode to form a coordination network, the contact between electrolyte and the positive electrode with high activity is further reduced, in addition, the stable SEI film can be formed on the negative electrode, gas production is inhibited, and finally the aim of improving the high temperature performance and the cycle performance of a battery is achieved.
Based on the above, the invention provides an electrolyte additive, the structural formula of which is shown as the formula (A);
wherein R is 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C1-C4 saturated hydrocarbon group or C2-C4 unsaturated alkenyl group; preferably, said R 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C2-C4 saturated hydrocarbon group or C3-C4 unsaturated alkenyl group;
X 1 、X 2 or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not both nitrogen atoms;
more preferably, X 1 、X 2 Or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not both nitrogen atoms;
R 3 、R 5 、R 6 Is one of a null, a hydrogen atom, a fluorine atom, a C1-C3 saturated hydrocarbon group or a cyano group, R 4 、R 7 Independently selected from hydrogen, fluorine, methyl or cyano;
more preferably, R 3 、R 5 、R 6 Is one of a null, hydrogen atom, fluorine atom or cyano group, R 4 、R 7 Independently selected from hydrogen atoms or cyano groups.
In specific embodiments, the compound of formula a is selected from at least one of compounds (I) to (VIII):
the lithium cobalt oxide battery can be decomposed on the surface of the positive electrode to form an interface film with high voltage stability and low impedance, the rapid lithium ion deintercalation capability is improved, the transition metal dissolution is relieved by the stable positive electrode interface, and the side reaction between the positive electrode interface and electrolyte is reduced, so that the electrochemical performance of the lithium cobalt oxide battery under high voltage is improved. In addition, sulfonic acid groups and fluorine-containing groups in the additive structure can be decomposed at the negative electrode in an induction way to form a stable low-impedance SEI film, and unstable rupture decomposition of the SEI film at high temperature is relieved, so that gas generation is induced, and the battery bulge is invalid. The specific synthetic route template of the electrolyte additive disclosed by the invention is shown as follows, but is not limited to the synthetic method provided by the invention.
The invention provides a preparation method of the electrolyte additive, which comprises the following steps:
reacting the compound shown in the formula (B) with the compound shown in the formula (C) in the presence of a catalyst and a solvent to obtain the electrolyte additive;
the structural formulas of the formula (B) and the formula (C) are as follows:
wherein R is 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C1-C4 saturated hydrocarbon group or C2-C4 unsaturated alkenyl group, X 1 、X 2 Or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not being simultaneously nitrogen atoms, R 3 、R 5 、R 6 Is one of a null, a hydrogen atom, a fluorine atom, a C1-C3 saturated hydrocarbon group or a cyano group, R 4 、R 7 Independently selected from hydrogen atom, fluorine atom, methyl group or cyano group.
According to the invention, the solvent and the compound of formula (B) and the compound of formula (C) and the catalyst are added in the presence of an inert gas and stirred.
The reaction is preferably carried out at 0℃and the addition temperature of the starting materials is preferably 0 ℃.
In some embodiments, the catalyst comprises NaH; the solvent comprises THF.
Specifically, the molar ratio of the addition of the formula (B), the formula (C) and the catalyst is (6-7): 11-12): 8-10.
After the reaction was completed, the ice-water bath was removed, and the resulting mixture was stirred at room temperature. The mixture was then quenched with ammonium chloride solution and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel short pad.
Preferably, the eluent is n-hexane/ethyl acetate mixed solution (volume ratio is 9:1), and the compound is obtained after the solvent is removed by rotary evaporation.
The preparation method of the electrolyte additive provided by the invention is simple, does not need expensive instruments and equipment, and is convenient to realize.
The invention also provides an electrolyte which comprises lithium salt, a nonaqueous organic solvent and a first electrolyte additive. The first electrolyte additive is the electrolyte additive related in the technical scheme or the electrolyte additive prepared by the preparation method.
Wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF) 6 ) Lithium perchlorate (LiClO) 4 ) Lithium tetrafluoroborate (LiBF) 4 ) At least one of lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiLiLiFSI), lithium bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiODFB), and lithium difluoro (oxalato) phosphate (LiDODFP).
The organic solvent is a nonaqueous organic solvent, and specifically can be selected from any one or more of an organic ester solvent, an ether solvent, a sulfone solvent or a nitrile solvent, wherein the organic ester solvent is any one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, 1, 4-butyrolactone, methyl formate, ethyl acetate, methyl propionate (English name n-Propyl propionate, abbreviated as PP), ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, methyltrifluoroethyl carbonate or bis (2, 2-trifluoroethyl) carbonate; the ether solvent is dimethyl ether, diethyl ether, methylethyl ether, 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether any one or more of 1h,5 h-octafluoropentyl-1, 2-tetrafluoroethyl ether; the nitrile solvent is any one or more of adiponitrile, succinonitrile or glutaronitrile; the sulfone solvent is dimethyl sulfoxide and/or sulfolane.
In some embodiments of the invention, the organic solvent is preferably specifically: PC: EMC: femc=30:40:30;
in some embodiments, the organic solvent is preferably specifically: PC: DEC: PP: tfec=25:30:35:10
In some embodiments, the organic solvent is preferably specifically: PC: EMC: adn=30:50:20;
in some embodiments, the organic solvent is preferably specifically: PC: EMC: F-eae=30:50:20;
in some embodiments, the organic solvent is preferably specifically: PC: EMC: PP: tms=30:30:30:10
The first electrolyte additive is the electrolyte additive related in the technical scheme.
In some embodiments of the invention, a second electrolyte additive is also included.
The second electrolyte additive is selected from one or more of ethylene carbonate, fluoroethylene carbonate, ethylene sulfate, bis-ethylene sulfate, propylene sulfate, 1, 3-propane sultone, 1, 3-propenesulfonic acid lactone, 1, 4-butanesulfonic acid lactone, 2, 4-butane sultone, phenyl methanesulfonate, methane disulfonic acid methylene ester, N-phenyl bis (trifluoromethanesulfonyl) imide, triallyl phosphate, tris (trimethylsilane) phosphite, trimethyl phosphite, triphenyl phosphite, tetramethyl methylenediphosphate, propargyl phosphate, (2-allylphenoxy) trisilane, tris (trimethylsilane) borate, 1,3, 5-triallyl isocyanurate, isocyanatoethyl methacrylate, hexamethylene diisocyanate, p-phenylene diisocyanate, 2, 4-toluene diisocyanate, 1,3, 6-hexane trisnitrile or 1, 2-bis (cyanoethoxy) ethane.
In some embodiments of the invention, the lithium salt comprises 11-25% by mass of the electrolyte; preferably 11% -23%; more preferably 11 to 20%.
The nonaqueous organic solvent accounts for 72-85% of the electrolyte by mass; preferably 75% -85%; more preferably 77 to 85%.
In some embodiments of the invention, the first electrolyte additive comprises 0.1% to 2% by mass of the electrolyte.
The sum of the first electrolyte additive and the second electrolyte additive accounts for 2-5% of the mass of the electrolyte.
In some embodiments of the present invention, the electrolyte is preferably performed in an argon glove box during the preparation process, and the organic solvent, the lithium salt and the electrolyte additive are uniformly mixed, more preferably performed in an argon glove box with water oxygen content less than or equal to 0.1ppm, specifically comprising the following steps:
slowly adding lithium salt into an organic solvent in an argon glove box with water oxygen content less than or equal to 0.1ppm, controlling the temperature to be not more than 38 ℃, adding a first electrolyte additive and a second electrolyte additive after the lithium salt is completely dissolved, and uniformly stirring to obtain the electrolyte.
The invention also provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm and the electrolyte related to the technical scheme. Wherein the material of the positive electrode is selected from one of lithium cobaltate, lithium manganate, ternary nickel cobalt manganese lithium, nickel lithium manganate, lithium iron phosphate or lithium manganese iron phosphate, and the lithium cobaltate is preferably selected; the active material of the negative electrode is preferably any one of artificial graphite, natural graphite, lithium titanate, metallic lithium, silicon carbon composite material or silicon oxide, and the artificial graphite is preferably selected according to the invention. The invention preferably selects the polyethylene membrane from one of the membrane polypropylene membrane and the polyethylene membrane.
When the additive shown in the structural formula A is applied to battery electrolyte, an interface film can be formed on the positive electrode and the negative electrode of the battery at the same time, and particularly, the additive can be decomposed on the surface of the positive electrode to form a low-impedance interface film; meanwhile, the high-stability SEI film can be decomposed into at the negative electrode, gas production is inhibited, and the high-temperature performance of the battery is improved. The lithium ion battery prepared from the non-aqueous electrolyte provided by the invention has better high-voltage electrochemical performance, and the overall cycle life of the prepared lithium cobalt oxide battery in a voltage range of 3.0-4.55V is greatly prolonged.
In some embodiments, the invention preferably carries out weighing and mixing on a positive electrode material Lithium Cobalt Oxide (LCO), a conductive agent carbon black (SuperP) and a binder polyvinylidene fluoride (PVDF, NMP solution with the content of 5% by mass) according to the mass ratio of 96.5:1.5:2, adds a proper amount of NMP after the mixing is finished to control the theoretical solid content to be 55%, carries out homogenization by using a vacuum defoaming machine to obtain positive electrode slurry, uniformly coats the positive electrode slurry on aluminum foil with the thickness of 17 mu m, and obtains a 50mm multiplied by 70mm positive electrode plate after drying, rolling and cutting.
Mixing artificial graphite as a cathode material, super P as a conductive agent, sodium carboxymethylcellulose (CMC, deionized water solution with the content of 1.5% by mass fraction) as a thickener and styrene-butadiene rubber as a binder (SBR, deionized water solution with the content of 48% by mass fraction) according to the mass ratio of 95:1:1.5:2.5, adding deionized water after the mixing is completed to control the theoretical solid content to be 52%, homogenizing by using a vacuum defoaming machine to obtain cathode slurry, uniformly coating the cathode slurry on copper foil with the thickness of 17 mu m, and drying, rolling and cutting to obtain the 52mm multiplied by 72mm cathode pole piece. The N/P ratio of the positive electrode and the negative electrode was 1.1.
The polyethylene film was cut to 55mm x 75mm size and baked in vacuo at 70 ℃ for 48h to remove water.
And manufacturing the soft-package laminated battery at the environmental dew point of less than or equal to minus 45 ℃, sequentially stacking the positive plate, the diaphragm and the negative plate, wherein the positive electrode lug and the negative electrode lug are positioned on the same side, the diaphragm is positioned between the positive electrode lug and the negative electrode lug to play a role in isolation, and the bare cell is obtained. And placing the bare cell in an aluminum plastic film outer package, baking for 12 hours at 90 ℃ in vacuum, cooling to below 40 ℃, injecting the prepared electrolyte, and then carrying out the procedures of packaging, high Wen Jinrun, formation, aging, secondary air extraction packaging, capacity division and the like to obtain the battery.
The film forming additive developed by the invention can be decomposed on the surface of the positive electrode under high voltage to form a stable low-impedance CEI film, and the capability of rapidly conducting lithium ions is improved.
The film-forming additive developed by the invention contains abundant electron-withdrawing groups in the structure, can be complexed with transition metal on the surface of the positive electrode, and stabilizes the transition metal Co under high pressure of the positive electrode 4+ Inhibit oxygen precipitation and prolong the cycle life of the battery.
The film forming additive developed by the invention contains sulfonic acid groups in the additive structure, can form a stable SEI film on the negative electrode, inhibit gas production and improve the high temperature performance of the lithium ion battery.
In order to further illustrate the present invention, the following examples are provided. The following examples of the present invention, in which specific conditions are not specified, may be conducted under conventional conditions or conditions suggested by the manufacturer. The reagents or apparatus used were conventional products available commercially without the manufacturer's attention.
Example 1
The preparation of the compound (I) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, 3-iminodipropionitrile (0.86 g,7.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added after the THF was cooled to 0℃and stirring was continued for 30min. To the resulting solution was slowly added 4-methylpyridine-2-sulfonyl chloride (2.10 g,11.00 mmol) pre-frozen to 0 ℃, after the addition was completed the ice-water bath was removed and the resulting mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (I) in 73.2% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 12 H 14 N 4 O 2 S[M+1] + ,278.08,found 278.12。
The electrolyte 1 sample was prepared as follows:
in an argon glove box with water and oxygen content less than or equal to 0.1ppm, propylene Carbonate (PC), methyl ethyl carbonate (EMC) and methyl trifluoroethyl carbonate (FEMC) are uniformly mixed according to a volume ratio of 30:40:30 to obtain an organic solvent, and then lithium hexafluorophosphate (LiPF) is slowly added into the organic solvent 6 ) After complete dissolution, adding 1, 3-Propane Sultone (PS), fluoroethylene carbonate (FEC) and compound (I), stirring uniformly to obtain electrolyte 1, wherein LiPF 6 The use amount of the organic solvent, PS, FEC and the compound (I) is 13 percent of the total mass of the electrolyte、84％、1％、1％、1％。
The experimental battery 1 sample was prepared as follows:
the method comprises the steps of weighing and mixing positive electrode materials of Lithium Cobalt Oxide (LCO), conductive agent carbon black (SuperP) and binder polyvinylidene fluoride (PVDF, NMP solution with the mass fraction of 5%) according to the mass ratio of 96.5:1.5:2, adding a proper amount of NMP after mixing to control the theoretical solid content to be 55%, homogenizing by using a vacuum defoaming machine to obtain positive electrode slurry, uniformly coating the positive electrode slurry on aluminum foil with the thickness of 17 mu m, and drying, rolling and cutting to obtain the 50mm multiplied by 70mm positive electrode plate.
Mixing artificial graphite as a cathode material, super P as a conductive agent, sodium carboxymethylcellulose (CMC, deionized water solution with the content of 1.5% by mass fraction) as a thickener and styrene-butadiene rubber as a binder (SBR, deionized water solution with the content of 48% by mass fraction) according to the mass ratio of 95:1:1.5:2.5, adding deionized water after the mixing is completed to control the theoretical solid content to be 52%, homogenizing by using a vacuum defoaming machine to obtain cathode slurry, uniformly coating the cathode slurry on copper foil with the thickness of 17 mu m, and drying, rolling and cutting to obtain the 52mm multiplied by 72mm cathode pole piece. The N/P ratio of the positive electrode and the negative electrode was 1.1.
The polyethylene film was cut to 55mm x 75mm size and baked in vacuo at 70 ℃ for 48h to remove water.
And manufacturing the soft-package laminated battery at the environmental dew point of less than or equal to minus 45 ℃, sequentially stacking the positive plate, the diaphragm and the negative plate, wherein the positive electrode lug and the negative electrode lug are positioned on the same side, the diaphragm is positioned between the positive electrode lug and the negative electrode lug to play a role in isolation, and the bare cell is obtained. And placing the bare cell in an aluminum plastic film outer package, baking for 12 hours at 90 ℃ in vacuum, cooling to below 40 ℃, injecting the prepared electrolyte, and then carrying out the procedures of packaging, high Wen Jinrun, formation, aging, secondary air extraction packaging, capacity division and the like to obtain the experimental battery 1.
Example 2
The preparation of compound (II) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, bis (but-3-enyl) amine (0.88 g,7.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added after the THF was reduced to 0℃and stirring was continued for 30min. To the resulting solution was slowly added 5-fluoropyridine-3-sulfonyl chloride (2.14 g,11.00 mmol) pre-frozen to 0 ℃ and the resulting mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (II) in 72.4% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 13 H 17 N 2 O 2 FS[M+1] + ,284.10,found 284.08。
Electrolyte 2 and experimental cell 2 were prepared as in example 1, except that additives added to electrolyte 2 were PS, ethylene carbonate (VC) and compound (II), wherein LiPF 6 The use amount of the organic solvent, PS, VC and the compound (II) is 13%, 84%, 1% and 1% of the total mass of the electrolyte respectively.
Example 3
The preparation of compound (III) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, hexamethyldisilazane (1.13 g,7.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added after the THF was reduced to 0℃and stirring was continued for 30min. To the resulting solution was slowly added pyridine-3-sulfonyl chloride (1.95 g,11.00 mmol) pre-frozen to 0 ℃ and the resulting mixture was stirred at room temperature for 12h. The mixture is then treated with ammonium chlorideThe solution (5 mL) was quenched and extracted three times with ethyl acetate (20 mL. Times.3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (III) in 70.9% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 11 H 22 N 2 O 2 SSi 2 [M+1] + ,302.09,found 302.13。
Electrolyte 3 and experimental cell 3 were prepared as in example 1, except that additives added to electrolyte 3 were vinyl sulfate (DTD), 1, 2-bis (cyanoethoxy) ethane (DENE), and compound (III), wherein LiPF 6 The amounts of the organic solvent, DTD, DENE and compound (III) used were 13%, 84%, 1% and 1% of the total mass of the electrolyte, respectively.
Example 4
The preparation of compound (IV) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, and after THF was reduced to 0deg.C, 2-tert-butylamine (0.90 g,7.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added and stirring continued for 30min. To the resulting solution was slowly added pyridine-4-sulfonyl chloride (1.95 g,11.00 mmol) pre-frozen to 0 ℃ and the resulting mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (IV) in 68.7% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 13 H 22 N 2 O 2 S[M+1] + ,270.14,found270.21。
Pressing to realityElectrolyte 4 and experimental cell 4 were prepared by the method of example 1, except that additives added to electrolyte 4 were FEC, propargyl phosphate (TPP), 1,3, 6-Hexanetrinitrile (HTCN), and compound (IV), wherein LiPF 6 The amounts of the organic solvent, FEC, TPP, HTCN and the compound (IV) are 13%, 83%, 1% and 1% of the total mass of the electrolyte.
Example 5
The preparation of compound (V) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, bis (trifluoroethyl) amine (1.27 g,7.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added after the THF was reduced to 0℃and stirring was continued for 30min. To the resulting solution was slowly added 2, 6-dicyano-pyridine-4-sulfonyl chloride (2.50 g,11.00 mmol) pre-frozen to 0 ℃ and the resulting mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (V) in 73.5% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 11 H 6 N 4 O 2 F 6 S[M+1] + ,372.01,found 372.11。
Electrolyte 5 and experimental cell 5 were prepared as in example 1, except that additives added to electrolyte 5 were FEC, tris (trimethylsilane) phosphite (TMSPI) and compound (V), wherein LiPF 6 The amounts of the organic solvent, FEC, TMSPI and the compound (V) used are 13%, 84%, 1% and 1% of the total mass of the electrolyte.
Example 6
The preparation of compound (VI) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, dimethyl aminodiacetate (1.13 g,7.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added after the THF had fallen to 0℃and stirring was continued for 30min. To the resulting solution was slowly added 3-cyanopyrazine-2-sulfonyl chloride (2.43 g,12.00 mmol) pre-frozen to 0deg.C and the resulting mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (VI) in 78.2% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 11 H 12 N 4 O 6 S[M+1] + ,328.05,found 328.08。
Electrolyte 6 and experimental cell 6 were prepared as in example 1, except that the lithium salt added to electrolyte 6 was lithium tetrafluoroborate (LiBF 4 ) The organic solvent is Propylene Carbonate (PC), diethyl carbonate (DEC), propyl Propionate (PP), bis (2, 2-trifluoroethyl) carbonate (TFEC), the volume ratio is 25:30:35:10, and the additive is FEC, TMSP and compound (VI), wherein LiBF is prepared by mixing the following components in proportion by volume 4 The amounts of the organic solvent, FEC, TMSP and compound (VI) used are 11%, 84%, 3%, 1% and 1% of the total mass of the electrolyte.
Example 7
The preparation of compound (VII) comprises the following specific steps:
to a clean and dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was addedAnhydrous THF (50 mL) was added, then the flask was placed in an ice-water bath, stirring was turned on, and di-sec-butylamine (0.77 g,6.00 mmol) and sodium hydride (240 mg,10.00 mmol) were slowly added after the THF was reduced to 0 ℃ and stirring continued for 30min. To the resulting solution was slowly added 4-cyanopyridine-2-sulfonyl chloride (2.22 g,11.00 mmol) pre-frozen to 0℃and the resulting mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (VII) in 71.3% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 14 H 21 N 3 O 2 S[M+1] + ,295.14,found 295.19。
Electrolyte 7 and test cell 7 were prepared as in example 1, except that the lithium salt added to electrolyte 7 was LiPF 6 And lithium perchlorate (LiClO) 4 ) The organic solvent is Propylene Carbonate (PC), methyl ethyl carbonate (EMC) and Adiponitrile (ADN) with the volume ratio of 30:50:20, and the additive is FEC, tris (trimethylsilane) borate (TMSB) and compound (VII), wherein the LiPF is 6 、LiClO 4 The amounts of the organic solvent, FEC, TMSB and the compound (VI) used were 8%, 81%, 1% and 1% of the total mass of the electrolyte.
Example 8
The preparation of compound (VIII) comprises the following specific steps:
to a clean, dry 150mL three-necked flask equipped with a magnetic rotor under nitrogen atmosphere was added anhydrous THF (50 mL), then the flask was placed in an ice-water bath, stirring was turned on, and after THF was reduced to 0deg.C diallylamine (0.68 g,7.00 mmol) and sodium hydride (192 mg,8.00 mmol) were slowly added and stirring continued for 30min. Pyrimidine-2-sulfonyl chloride (1.96 g,11.00 mmol) pre-frozen to 0deg.C was slowly added to the resulting solution and the resulting mixture was admixedThe mixture was stirred at room temperature for 12h. The mixture was then quenched with ammonium chloride solution (5 mL) and extracted three times with ethyl acetate (20 ml×3), the organic phases were combined, dried over anhydrous magnesium chloride, and concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel with a short pad eluting with a mixture of n-hexane/ethyl acetate (volume ratio 9:1) to give compound (VIII) in 71.3% yield after removal of the solvent by rotary evaporation. GC-MS (m/z): calcd.for C 10 H 13 N 3 O 2 S[M+1] + ,239.07,found 239.11。
Electrolyte 8 and test cell 8 were prepared as in example 1, except that the lithium salt added to electrolyte 8 was LiPF 6 Lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiWSI), propylene Carbonate (PC), ethyl Methyl Carbonate (EMC), 1H, 5H-octafluoropentyl-1, 2-tetrafluoroethyl ether (F-EAE) in a volume ratio of 30:50:20, and additives of FEC, 1,3, 5-triallyl isocyanurate (TAIC) and compound (VIII), wherein the LiPF is a mixture of two or more of the following components 6 The amounts of LiTFSI, liLSI, organic solvent, FEC, TAIC and compound (VIII) used are 10%, 5%, 10%, 72%, 1% and 1% of the total mass of the electrolyte respectively.
Example 9
Electrolyte 9 and experimental battery 9 were prepared according to the method of example 1, except that lithium salt added in electrolyte 9 was lithium bisoxalato borate (LiBOB) and lithium difluorooxalato borate (LiODFB), the organic solvents were Propylene Carbonate (PC), ethyl Methyl Carbonate (EMC), propyl Propionate (PP), sulfolane (TMS) in a volume ratio of 30:30:30:10, and the additives were FEC, PS and compound (V), wherein the use amounts of LiBOB, liODFB, the organic solvents, FEC, PS, and compound (IV) were 5%, 8%, 84.9%, 1%, 0.1% of the total mass of the electrolyte, respectively.
Example 10
An electrolyte 10 and an experimental battery 10 were prepared as in example 1, except that lithium salt added to the electrolyte 10 was LiPF 6 And lithium difluorodioxalate phosphate (LiDODFP), the additive added being compound (V), wherein LiPF 6 The use amount of the organic solvent and the compound (IV) is respectively 10 percent and 5 percent of the total mass of the electrolyte、83％、2％。
Comparative example 1
Electrolyte 11 and experimental cell 11 were prepared according to the method of example 1, except that the additive added to electrolyte 11 was FEC in which LiPF 6 The usage amounts of the organic solvent and the FEC are respectively 13%, 85% and 2% of the total mass of the electrolyte.
Comparative example 2
An electrolyte 12 and an experimental cell 12 were prepared according to the method of example 1, except that the additives added to the electrolyte 12 were DTD, HTCN, in which LiPF 6 The usage amounts of the organic solvent, the DTD and the HTCN are respectively 13%, 85%, 1% and 1% of the total mass of the electrolyte.
Comparative example 3
An electrolyte 13 and an experimental cell 13 were prepared according to the method of example 1, except that the additive added to the electrolyte 13 was PS, compound (IX), wherein LiPF 6 The amounts of the organic solvent, PS and the compound (IX) used were 13%, 85%, 1% and 1% of the total mass of the electrolyte.
The compositions and contents of the electrolytes of examples 1 to 10 and comparative examples 1 to 3 are shown in Table 1.
The lithium cobaltates prepared in examples 1 to 10 and comparative examples 1 to 2 were subjected to a normal temperature cycle performance test, a high temperature cycle test and a rate cycle performance test, respectively, under the following test conditions:
battery normal temperature cycle test
The prepared lithium cobaltate battery is charged to cut-off current of 0.05 ℃ at constant current and constant voltage in a constant temperature room with the ambient temperature of 25 ℃ at current of 1 ℃ and voltage of 4.55V, then is discharged to voltage of 3V at constant current of 1 ℃ for 300 weeks, and the recording capacity retention rate and the nth cycle capacity retention rate (%) = (nth cycle discharge specific capacity/first cycle discharge specific capacity) are 100%.
High temperature cycle test of battery
Before the test, an internal resistance tester is used for measuring the internal resistance of the battery, and a drainage method is used for measuring the volume of the battery. And then placing the prepared lithium cobaltate battery in a high-temperature explosion-proof box with the temperature of 45 ℃ for standing for 4 hours, so that the internal and external temperatures of the battery are stable. The constant current and constant voltage charge is carried out to cut-off current of 0.05C at current of 1C and voltage of 4.55V, then the constant current discharge is carried out to voltage of 3V at 1C, the cycle is carried out for 300 weeks, the recording capacity retention rate is recorded, and the nth cycle capacity retention rate (%) = (the nth cycle discharge specific capacity/first cycle discharge specific capacity) ×100%. And taking out the battery after the test is finished, and recording the test internal resistance and volume, wherein the internal resistance increase rate is 100 percent (internal resistance after high-temperature circulation-initial internal resistance) and the initial internal resistance, and the volume expansion rate is 100 percent (volume after high-temperature circulation-initial volume) and the initial volume.
Battery rate cycle test
And placing the prepared lithium cobaltate battery in a constant temperature box at 25 ℃, and standing for 4 hours to stabilize the internal and external temperatures of the battery. The constant current and constant voltage charge was carried out at a current of 3C and a voltage of 4.55V until the off current was 0.05C, and then at a constant current discharge of 0.5C until the voltage was 3V, and the cycle was continued for 200 weeks, thereby recording the capacity retention rate and the n-th cycle capacity retention rate (%) = (n-th cycle specific discharge capacity/first cycle specific discharge capacity) ×100%.
TABLE 1 electrolyte compositions and corresponding cell performances for each of the examples and comparative examples
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The electrolyte prepared in examples 1 to 10 and comparative examples 1 to 3 were used to prepare lithium cobaltate batteries, and the battery performance test results are shown in table 1, and it can be seen that the electrolyte prepared in examples 1 to 10 is used in lithium cobaltate batteries, and all exhibit better capacity retention than those in comparative examples 1 and 3, which proves that the film-forming additive in the present invention has an improving effect on the electrical performance of lithium cobaltate batteries under high pressure. Wherein example 9 also shows advantages over the other with a smaller additionThe cyclic life of the ratio of 1 to 3 is benefited by substituting hydrogen on alpha carbon adjacent to pyridine nitrogen in the compound (V) by cyano, and the cyano of the strong electron withdrawing group and the pyridine nitrogen atom form a synergistic effect, so that the transition metal ion Co with high activity on the LCO surface is greatly stabilized 4+ Side reactions with the electrolyte and escape of lattice oxygen are suppressed. Meanwhile, two trifluoroethyl functional groups of N on sulfonamide are connected, and 6 fluorine atoms improve the oxidation resistance of the structure, improve the high-pressure stability of the CEI film, and in addition, the SEI film with low impedance and rich LiF can be formed on the surface of the negative electrode in an induction mode. As can be seen from the test results, compared with comparative example 3, the film forming additive of the invention introduces rich favorable functional groups through reasonable molecular design, so that the film forming additive is decomposed at the interface of the positive electrode to form a stable CEI film, a series of malignant side reactions of the surface of the positive electrode and electrolyte are relieved, thereby prolonging the cycle life of the battery, and meanwhile, the film forming additive of the invention can also form a stable low-impedance SEI film in cooperation with the negative electrode and the second additive, and from the perspective of volume test after high-temperature test, the generation of gas is effectively inhibited, thereby further improving the high-temperature performance of the battery.
The long-term quick charge capacity of the lithium cobalt oxide battery added with the film forming additive is evaluated through a multiplying power cycle test, and from test results, it can be seen that the lithium cobalt oxide battery adopting the film forming additive is subjected to a large multiplying power 3C charge/0.5C discharge cycle test, and the result is obviously superior to that of a comparison group 1-3, because the film forming additive can effectively reduce interface impedance while inhibiting gas production, and the stable and compact interface film endows lithium ions with quick and reversible transmission capacity.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (11)

1. An electrolyte additive is characterized in that the structural formula of the electrolyte additive is shown as a formula (A);
wherein R is 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C1-C4 saturated hydrocarbon group or C2-C4 unsaturated alkenyl group, X 1 、X 2 Or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not being simultaneously nitrogen atoms, R 3 、R 5 、R 6 Is one of a null, a hydrogen atom, a fluorine atom, a C1-C3 saturated hydrocarbon group or a cyano group, R 4 、R 7 Independently selected from hydrogen atom, fluorine atom, methyl group or cyano group.
2. The additive according to claim 1, wherein the compound represented by structural formula a is selected from at least one of compounds (I) to (VIII):
3. The method for preparing the electrolyte additive according to any one of claims 1 to 2, comprising the steps of:
reacting the compound shown in the formula (B) with the compound shown in the formula (C) in the presence of a catalyst and a solvent to obtain the electrolyte additive;
the structural formulas of the formula (B) and the formula (C) are as follows:
wherein R is 1 And R is 2 Independently selected from propionitrile, trimethylsilyl, trifluoroethyl, methyl acetate, C1-C4 saturated hydrocarbon group or C2-C4 unsaturated alkenyl group, X 1 、X 2 Or X 3 Independently selected from carbon or nitrogen atoms, X 2 And X 3 Not simultaneously being nitrogen atoms, R 3 、R 5 、R 6 Is one of a null, a hydrogen atom, a fluorine atom, a C1-C3 saturated hydrocarbon group or a cyano group, R 4 、R 7 Independently selected from hydrogen atom, fluorine atom, methyl group or cyano group.
4. An electrolyte is characterized by comprising lithium salt, a nonaqueous organic solvent and a first electrolyte additive;
the first electrolyte additive is the electrolyte additive according to any one of claims 1 to 2 or the electrolyte additive prepared by the preparation method according to claim 3.
5. The electrolyte according to claim 4, wherein the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bistrifluoromethylsulfonimide, lithium bistrifluorosulfonylimide, lithium bisoxalato borate, lithium difluorooxalato borate, or lithium difluorodioxaato phosphate;
The non-aqueous organic solvent is selected from any one or more of organic ester solvents, ether solvents, sulfone solvents or nitrile solvents.
6. The electrolyte of claim 4, wherein the electrolyte further comprises a second electrolyte additive;
the second electrolyte additive is selected from one or more of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, ethylene sulfate, bis-ethylene sulfate, propylene sulfate, 1, 3-propane sultone, 1, 3-propenesulfonlactone, 1, 4-butanesulfonic acid lactone, 2, 4-butane sultone, phenyl methanesulfonate, methane disulfonic acid methylene ester, N-phenyl bis (trifluoromethanesulfonyl) imide, triallyl phosphate, tris (trimethylsilane) phosphite, trimethyl phosphite, triphenyl phosphite, tetramethyl methylenediphosphate, propargyl phosphate, (2-allylphenoxy) trimethyl silane, tris (trimethylsilane) borate, 1,3, 5-triallyl isocyanurate, isocyanatoethyl methacrylate, hexamethylene diisocyanate, terephthalyl diisocyanate, 2, 4-toluene diisocyanate, 1,3, 6-hexane tri-nitrile or 1, 2-bis (cyanoethoxy) ethane.
7. The electrolyte according to claim 4, wherein,
the lithium salt accounts for 11-25% of the electrolyte by mass; the nonaqueous organic solvent accounts for 72-85% of the electrolyte by mass.
8. The electrolyte according to claim 6, wherein the first electrolyte additive accounts for 0.1-2% of the electrolyte by mass; the sum of the first electrolyte additive and the second electrolyte additive accounts for 2-5% of the electrolyte by mass.
9. The lithium ion battery is characterized by comprising a positive electrode, a negative electrode, a diaphragm and electrolyte;
the electrolyte according to any one of claims 4 to 8.
10. The lithium ion battery according to claim 9, wherein the material of the positive electrode is selected from any one of lithium cobaltate, lithium manganate, ternary nickel cobalt manganese lithium, lithium nickel manganate, lithium iron phosphate or lithium manganese iron phosphate;
the material of the negative electrode is selected from any one of artificial graphite, natural graphite, lithium titanate, metallic lithium, silicon-carbon composite material or silicon oxide;
the membrane is selected from polypropylene membrane or polyethylene membrane.
11. The additive according to any one of claims 1 to 8, 9 to 10, wherein the additive represented by the structural formula a is applied to a battery electrolyte to form a CEI interface film at a battery positive electrode; meanwhile, an SEI interfacial film is formed at the negative electrode of the battery.
CN202311253766.6A 2023-09-26 2023-09-26 Electrolyte additive, preparation method thereof, electrolyte and lithium ion battery Pending CN117304098A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117638247A (en) * 2024-01-25 2024-03-01 江苏丰山全诺新能源科技有限公司 Functional additive for high-voltage lithium ion battery and application thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117638247A (en) * 2024-01-25 2024-03-01 江苏丰山全诺新能源科技有限公司 Functional additive for high-voltage lithium ion battery and application thereof
CN117638247B (en) * 2024-01-25 2024-04-09 江苏丰山全诺新能源科技有限公司 Functional additive for high-voltage lithium ion battery and application thereof

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