CN113782833A - Electrolyte and preparation method and application thereof - Google Patents
Electrolyte and preparation method and application thereof Download PDFInfo
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- CN113782833A CN113782833A CN202111133733.9A CN202111133733A CN113782833A CN 113782833 A CN113782833 A CN 113782833A CN 202111133733 A CN202111133733 A CN 202111133733A CN 113782833 A CN113782833 A CN 113782833A
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- electrolyte
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- lithium
- glutaronitrile
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 72
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- 239000002904 solvent Substances 0.000 claims abstract description 53
- 239000002994 raw material Substances 0.000 claims abstract description 34
- 239000000654 additive Substances 0.000 claims abstract description 28
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 26
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 26
- 230000000996 additive effect Effects 0.000 claims abstract description 24
- ZTOMUSMDRMJOTH-UHFFFAOYSA-N glutaronitrile Chemical compound N#CCCCC#N ZTOMUSMDRMJOTH-UHFFFAOYSA-N 0.000 claims abstract description 24
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 claims abstract description 17
- -1 lithium hexafluorophosphate Chemical group 0.000 claims abstract description 15
- UJTPZISIAWDGFF-UHFFFAOYSA-N ethenylsulfonylbenzene Chemical compound C=CS(=O)(=O)C1=CC=CC=C1 UJTPZISIAWDGFF-UHFFFAOYSA-N 0.000 claims abstract description 10
- DIEXQJFSUBBIRP-UHFFFAOYSA-N tris(2,2,2-trifluoroethyl) borate Chemical compound FC(F)(F)COB(OCC(F)(F)F)OCC(F)(F)F DIEXQJFSUBBIRP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 22
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 20
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 claims description 18
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 16
- 238000002844 melting Methods 0.000 claims description 16
- 230000008018 melting Effects 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 10
- 229910052744 lithium Inorganic materials 0.000 claims description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 8
- FPPLREPCQJZDAQ-UHFFFAOYSA-N 2-methylpentanedinitrile Chemical compound N#CC(C)CCC#N FPPLREPCQJZDAQ-UHFFFAOYSA-N 0.000 claims description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 20
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 20
- 230000000052 comparative effect Effects 0.000 description 17
- 239000010408 film Substances 0.000 description 12
- 239000000047 product Substances 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 238000005086 pumping Methods 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 239000004743 Polypropylene Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 229920001155 polypropylene Polymers 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- WTQMTUQXPWPJIT-UHFFFAOYSA-N 3-methylpentanedinitrile Chemical compound N#CCC(C)CC#N WTQMTUQXPWPJIT-UHFFFAOYSA-N 0.000 description 3
- 230000002411 adverse Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000003759 ester based solvent Substances 0.000 description 3
- 229910013872 LiPF Inorganic materials 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000004806 packaging method and process Methods 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 229910014336 LiNi1-x-yCoxMnyO2 Inorganic materials 0.000 description 1
- 229910014446 LiNi1−x-yCoxMnyO2 Inorganic materials 0.000 description 1
- 229910014825 LiNi1−x−yCoxMnyO2 Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 150000005678 chain carbonates Chemical class 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 150000005676 cyclic carbonates Chemical class 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000010534 mechanism of action Effects 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0568—Liquid materials characterised by the solutes
-
- 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
- H01M10/0569—Liquid materials characterised by the solvents
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
Abstract
The invention discloses an electrolyte and a preparation method and application thereof, and the preparation raw materials of the electrolyte comprise: lithium salts, solvents and additives; the lithium salt is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide; the solvent comprises a glutaronitrile solvent; the additive includes phenyl vinyl sulfone and tris (2, 2, 2-trifluoroethyl) borate. According to the invention, lithium bis (fluorosulfonyl) imide is used for partially replacing lithium hexafluorophosphate, and the conductivity of the lithium ion electrolyte is improved by utilizing the excellent high-temperature stability and higher solubility of the lithium bis (fluorosulfonyl) imide. The electrolyte solvent uses glutaronitrile solvents, so that the electrolyte still has high thermal stability at ultrahigh temperature. The lithium salt, the solvent and the additive in the electrolyte are mutually cooperated and matched, so that the excellent electrochemical performance of the lithium ion battery under the high-temperature condition is realized.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte and a preparation method and application thereof.
Background
In recent years, due to the pressure of environmental pollution and energy shortage, all countries are forced to search new green, environment-friendly and sustainable energy. Lithium ion batteries have been one of the most attractive power sources because of their advantages such as high energy density, long cycle life, and high operating voltage. However, as people have increasingly learned about the use conditions of batteries, it is found that the use of batteries is often higher than normal temperature, for example, when a notebook computer is running, the temperature of the batteries rises to about 45 ℃ due to heat generation; the battery for the GPS is exposed to the sun for a long time, the temperature is often about 80 ℃, and the requirements on the working stability and the storage stability of a battery system for working or storing under a high-temperature condition are more strict, so that the attention is paid to the improvement of the electrical property and the high-temperature storage property of the battery under the high-temperature condition in the industry.
Under high temperature environment, a series of changes occur in the lithium ion battery system. The anode material has high activity and can generate oxidation reaction with the electrolyte, thereby affecting the performance of the lithium ion battery. When the battery is stored in a high-temperature environment for a long time, the electrolyte can volatilize or be reduced and decomposed, so that the battery is inflated, and safety problems such as battery explosion and the like can be caused.
In the related art, the ballooning problem of the battery can be solved to some extent by adjusting each preparation raw material of the electrolyte, for example, by adding some additives, but the electrical properties of the battery at normal and high temperatures are seriously affected.
Therefore, it is required to develop an electrolyte having excellent high-temperature electrical properties.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides the electrolyte which has excellent high-temperature electrical property.
The invention also provides a preparation method of the electrolyte.
The invention also provides application of the electrolyte in a lithium ion battery.
The invention provides an electrolyte in a first aspect, which is characterized in that: the preparation raw materials comprise: lithium salts, solvents and additives;
the lithium salt is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
the solvent comprises a glutaronitrile solvent;
the additive includes phenyl vinyl sulfone and tris (2, 2, 2-trifluoroethyl) borate.
The glutaronitrile solvent has a wide electrochemical window and high thermal stability. And can keep liquid state in a larger temperature range, and can improve the solubility of lithium salt.
The lithium bis (fluorosulfonyl) imide (LiFSI) has good stability, no hydrolysis and good thermal stability.
Phenyl vinyl sulfone (phenyl vinyl sulfone, abbreviated as PVS), the specific mechanism of action of PVS is:
(1) the double bond in the molecule endows PVS with preferential oxidizing property;
(2) the chemical stability of the interfacial film can be ensured by the aromatic ring structure in the molecule;
(3) sulfur in the molecules imparts ionic conductivity to the interfacial film.
By combining the advantages of the three aspects, the additive PVS constructs a protective anode interface film on the layered lithium-rich oxide, and can improve the cycling stability and rate capability of the battery.
The boric acid tri (2, 2, 2-trifluoroethyl) ester (TTFEB) can reduce the content of lithium-containing inorganic matters in the positive electrode/electrolyte interlayer, inhibit the generation of byproducts and the growth of a surface film, and reduce the polarization of the battery in the circulating process. In addition, the generated thin film can inhibit the dissolution of transition metal, improve the discharge capacity and coulombic efficiency of the battery and prolong the cycle life of the battery.
According to some embodiments of the invention, the lithium salt is present in the electrolyte in an amount of 8% to 15% by weight.
According to some embodiments of the invention, the solvent is present in the electrolyte in an amount of 80% to 90% by weight.
According to some embodiments of the invention, the additive is present in the electrolyte in a mass fraction of 1% to 5%.
According to some embodiments of the invention, the mass ratio of lithium hexafluorophosphate to lithium bis-fluorosulfonyl imide in the lithium salt is 1-10: 1.
According to some embodiments of the invention, the solvent further comprises an ester solvent.
According to some embodiments of the invention, the ester solvent comprises Ethyl Methyl Carbonate (EMC), Ethyl Propionate (EP) and Ethylene Carbonate (EC).
According to some embodiments of the invention, the mass ratio of ethyl methyl carbonate, ethyl propionate and ethylene carbonate in the solvent is 1-10: 1-5.
Ethylene Carbonate (EC) is a cyclic carbonate having a high dielectric constant, but also has a high viscosity. The solvent Ethyl Methyl Carbonate (EMC) is a chain carbonate, and has a low viscosity but a low dielectric constant. The EC with high dielectric constant and the EMC with low viscosity are mixed for use, and the requirements of the electrolyte in various aspects such as working temperature range, conductivity and the like can be met.
According to some embodiments of the invention, the glutaronitrile-based solvent includes at least one of glutaronitrile (melting point-29 ℃) and 2-methylglutaronitrile (melting point-45 ℃).
According to some embodiments of the present invention, the mass ratio of the glutaronitrile solvent and the ester solvent is 1: 1-2.
The second aspect of the present invention provides a method for preparing the above electrolyte, comprising the steps of:
s1: controlling the temperature and pressure, and adding the lithium salt into the solvent;
s2: and (4) adding the additive into the product obtained in the step S1 to obtain the product.
According to some embodiments of the present invention, the solvent is subjected to melting, sucking, passing and batching processes before step S1.
According to some embodiments of the invention, the material treatment temperature is 60 ℃ to 70 ℃ and the time is 5h to 7 h.
According to some embodiments of the present invention, the method for preparing the electrolyte specifically includes the following steps:
a. material melting: the melting points of different solvents are different, and the melting point of EC is 35-38 deg.C, so that it is necessary to first carry out melting material in operation.
b. Material suction: and (3) pumping the melted raw materials into a raw material tank by using pressure difference, wherein the pressure of a raw material barrel is in micro-positive pressure, the pressure of the raw material tank is-0.1 Mpa, and the raw materials are transferred into the raw material tank under the protection of nitrogen.
c. Material passing: the pressure of the raw material tank is increased to 0.1-0.15 Mpa, and the pressure of the purification equipment and the high-purity raw material tank is 0.02 Mpa. Controlling the opening degree of the valves of the pipelines, slowly pumping the raw materials from the raw material tank to the purification equipment, purifying, and pumping to the high-purity raw material tank.
d. Preparing materials: strictly controlling feeding according to the principle that the melting point of a raw material solvent is from low to high; during material preparation, the pressure of the high-purity raw material tank is adjusted to 0.15Mpa, the pressure of the metering kettle is 0.03Mpa, and the mass of the solvent is accurately metered by an electronic scale.
e. Adding lithium salt: the temperature of the stirring kettle is reduced to below 2 ℃ by a refrigerator and a circulating pump; adjusting the pressure of the stirring kettle to 0.02Mpa, adjusting the pressure of the metering kettle to 0.15Mpa, and transferring the materials; addition of appropriate LiPF Using glove box6And LiFSI, wherein the temperature of the stirring kettle is controlled within 2 ℃ all the time in the process of adding the LiFSI.
f. Adding an additive.
g. And (3) filtering and packaging: transferring the qualified electrolyte to a finished product barrel through a filter; when transferring material, the pressure of the stirring kettle is adjusted to 0.5bar (0.05Mpa), and the pressure of the finished product tank is 0.02 Mpa.
The third aspect of the invention provides the application of the electrolyte in the preparation of a lithium ion battery.
According to some embodiments of the invention, the lithium ion battery further comprises a positive electrode, a negative electrode, a separator, a current collector, and a casing.
According to some embodiments of the invention, the positive electrode material comprises LiNi1-x-yCoxMnyO2、LiFePO4One kind of (1).
According to some embodiments of the invention, the negative electrode material comprises graphite, silicon carbon and SiO2One kind of (1).
According to some embodiments of the invention, the separator comprises one of a polypropylene (PP) membrane, a polypropylene (PP) coated alumina ceramic membrane.
According to some embodiments of the invention, the housing comprises one of a steel-shelled cylindrical, a square-shaped pouch, or an aluminum-shelled battery.
The invention has at least the following beneficial effects:
according to the invention, lithium bis (fluorosulfonyl) imide is used for partially replacing lithium hexafluorophosphate, and the conductivity of the lithium ion electrolyte is improved by utilizing the excellent high-temperature stability and higher solubility of the lithium bis (fluorosulfonyl) imide. The electrolyte solvent uses glutaronitrile solvents, so that the electrolyte still has high thermal stability at ultrahigh temperature. The film forming additive uses an additive with good film forming stability, is beneficial to improving the thermal stability of the SEI film, and the SEI film is not easy to decompose under the high temperature condition. The lithium salt, the solvent and the additive in the electrolyte are mutually cooperated and matched, so that the excellent electrochemical performance of the lithium ion battery under the high-temperature condition is realized.
Detailed Description
The concept and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.
In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Specific examples of the present invention are described in detail below.
Example 1
The embodiment provides an electrolyte and a preparation method thereof.
The electrolyte of the embodiment is prepared from the following raw materials in parts by mass:
lithium salt: lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide (mass ratio 1: 1);
solvent: glutaronitrile solvents (the mass ratio of glutaronitrile to 3-methylglutaronitrile is 1:1) and ester solvents (the mass ratio of methyl ethyl carbonate, ethyl propionate and ethylene carbonate is 1:1: 5);
additive: phenyl vinyl sulfone and boric acid tris (2, 2, 2-trifluoroethyl) ester (mass ratio is 10: 1);
the mass fraction of the lithium salt in the electrolyte is 15 percent;
the mass fraction of the solvent in the electrolyte is 80 percent;
the mass fraction of the additive in the electrolyte is 5%.
The embodiment also provides a preparation method of the electrolyte, which comprises the following steps:
s1: controlling the temperature and pressure, and adding lithium salt into the solvent;
s2: and (5) adding an additive into the product obtained in the step S1 to obtain the product.
The method specifically comprises the following steps:
a. material melting: the melting points of different solvents are different, the melting point of the ethylene carbonate is 35-38 ℃, the melting point is higher, so the material melting is needed to be carried out firstly during operation, and the parameters of the material melting process are as follows: the ethylene carbonate is melted for 5 hours at 60 ℃.
b. Material suction: and (3) pumping the melted raw materials into a raw material tank by using pressure difference, wherein the pressure of a raw material barrel is in micro-positive pressure, the pressure of the raw material tank is-0.1 Mpa, and the raw materials are transferred into the raw material tank under the protection of nitrogen.
c. Material passing: the pressure of the raw material tank is increased to 0.15Mpa, and the pressure of the purification equipment and the pressure of the high-purity raw material tank are both 0.02 Mpa. Controlling the opening degree of the valves of the pipelines, slowly pumping the raw materials from the raw material tank to the purification equipment, purifying, and pumping to the high-purity raw material tank.
d. Preparing materials: according to the melting point of raw materials (ethyl propionate-73.9 ℃, methyl ethyl carbonate-55 ℃, 2-methylglutaronitrile-45 ℃, glutaronitrile-29 ℃ and ethylene carbonate 35-38 ℃, the feeding sequence is strictly controlled to be ethyl propionate, methyl ethyl carbonate, 2-methylglutaronitrile, glutaronitrile and ethylene carbonate, the pressure of a high-purity raw material tank is adjusted to 0.15MPa, the pressure of a metering kettle is 0.03MPa, and the mass of each solvent is accurately metered by an electronic scale during batching.
e. Adding lithium salt: the temperature of the stirring kettle is reduced to below 2 ℃ by a refrigerator and a circulating pump; adjusting the pressure of the stirring kettle to 0.02Mpa, adjusting the pressure of the metering kettle to 0.15Mpa, and transferring the materials; addition of appropriate LiPF Using glove box6And LiFSI, wherein the temperature of the stirring kettle is controlled within 2 ℃ all the time in the process of adding the LiFSI.
f. Adding an additive.
g. And (3) filtering and packaging: transferring the qualified electrolyte to a finished product barrel through a filter; when transferring material, the pressure of the stirring kettle is adjusted to 0.5bar (0.05Mpa), and the pressure of the finished product tank is 0.02 Mpa.
Example 2
The present embodiment is an electrolyte and a preparation method thereof, and the difference from embodiment 1 is that:
the electrolyte consists of the following preparation raw materials in parts by weight:
the electrolyte of the embodiment is prepared from the following raw materials in parts by mass:
lithium salt: lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide (mass ratio 1: 1);
solvent: glutaronitrile solvents (the mass ratio of glutaronitrile to 3-methylglutaronitrile is 1:1) and ester solvents (the mass ratio of methyl ethyl carbonate, ethyl propionate and ethylene carbonate is 5:5: 3);
additive: phenyl vinyl sulfone and boric acid tris (2, 2, 2-trifluoroethyl) ester (mass ratio is 5: 1);
the mass fraction of the lithium salt in the electrolyte is 10 percent;
the mass fraction of the solvent in the electrolyte is 85 percent;
the mass fraction of the additive in the electrolyte is 5%.
Example 3
The present embodiment is an electrolyte and a preparation method thereof, and the difference from embodiment 1 is that:
the electrolyte consists of the following preparation raw materials in parts by weight:
lithium salt: lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide (mass ratio 1: 1);
solvent: glutaronitrile solvents (the mass ratio of glutaronitrile to 3-methylglutaronitrile is 1:2) and ester solvents (the mass ratio of methyl ethyl carbonate, ethyl propionate and ethylene carbonate is 1:1: 1);
additive: phenyl vinyl sulfone and boric acid tris (2, 2, 2-trifluoroethyl) ester (mass ratio is 5: 1);
the mass fraction of the lithium salt in the electrolyte is 10 percent;
the mass fraction of the solvent in the electrolyte is 85 percent;
the mass fraction of the additive in the electrolyte is 5%.
Comparative example 1
The comparative example is an electrolyte and a preparation method thereof, and is different from example 1 in that: no glutaronitrile solvent was added.
Comparative example 2
The comparative example is an electrolyte and a preparation method thereof, and is different from example 1 in that: lithium bis (fluorosulfonylimide) was not added.
Comparative example 3
The comparative example is an electrolyte and a preparation method thereof, and is different from example 1 in that: no ester solvent was added.
Comparative example 4
The comparative example is an electrolyte and a preparation method thereof, and is different from example 1 in that: no phenyl vinyl sulfone was added.
Application example
In this example, lithium ion batteries were prepared by using the electrolytes prepared in examples 1 to 3 and the electrolytes prepared in comparative examples 1 to 4 as electrolytes, respectively.
The materials and parameters of the lithium ion battery are shown in table 1; to demonstrate the consistency of electrolyte properties and the reproducibility of the protocol provided by the present invention, 30 parallel cells were assembled for each electrolyte and tested in parallel.
TABLE 1 Battery materials and parameters
Test example
The battery assembled by the application example is tested by the embodiment, and the specific test items comprise the high-temperature cycle performance and the storage performance of the battery.
The cycle test conditions of the lithium ion battery are as follows:
temperature: 60 ℃;
multiplying power: 1C charging, 1C discharging;
testing voltage: 3.6-4.2V.
The storage performance test conditions are as follows: after charging the battery to 4.2V at 60 ℃, the battery was stored at 60 ℃ for 7 days, and after completion, 1C discharge was performed.
The statistical results of the various properties of the lithium ion battery are shown in table 2.
Table 2 statistics of lithium ion battery performance.
| Capacity Retention/% (60 ℃ C. 1C/1C100 weeks) | Discharge efficiency/% (after 7 days of storage at 60 ℃ C.) | |
| Example 1 | 83.32 | 88.13 |
| Example 2 | 85.12 | 90.21 |
| Example 3 | 82.18 | 87.81 |
| Comparative example 1 | 64.46 | 70.15 |
| Comparative example 2 | 61.71 | 65.56 |
| Comparative example 3 | 67.44 | 73.26 |
| Comparative example 4 | 63.55 | 67.57 |
In the comparative example 1, a glutaronitrile solvent is not added, the glutaronitrile solvent is beneficial to expanding the temperature application range of the lithium ion battery, and the high-temperature performance of the battery is adversely affected by the absence of the glutaronitrile solvent.
Comparative example 2 where the lithium salts were all LiPF6However, LiPF6Sensitive to water and decomposed at high temperature, and the high temperature performance is lowered.
In comparative example 3, no ester solvent was added, which adversely affected the cycle performance of the battery.
Comparative example 4, in which phenyl vinyl sulfone was not added, also adversely affected the high temperature electrical properties of the lithium ion battery.
In conclusion, the lithium difluorosulfonimide lithium is used for partially replacing lithium hexafluorophosphate, and the conductivity of the lithium ion electrolyte is improved by utilizing the excellent high-temperature stability and high solubility of the lithium difluorosulfonimide lithium. The electrolyte solvent uses glutaronitrile solvents, so that the electrolyte still has high thermal stability at ultrahigh temperature. The film forming additive uses an additive with good film forming stability, is beneficial to improving the thermal stability of the SEI film, and the SEI film is not easy to decompose under the high temperature condition. The lithium salt, the solvent and the additive in the electrolyte are mutually cooperated and matched, so that the excellent electrochemical performance of the lithium ion battery under the high-temperature condition is realized.
While the embodiments of the present invention have been described in detail with reference to the specific embodiments, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art. Furthermore, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.
Claims (10)
1. An electrolyte, characterized by: the preparation raw materials comprise: lithium salts, solvents and additives;
the lithium salt is lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide;
the solvent comprises a glutaronitrile solvent;
the additive includes phenyl vinyl sulfone and tris (2, 2, 2-trifluoroethyl) borate.
2. An electrolyte as claimed in claim 1, wherein: the mass fraction of the lithium salt in the electrolyte is 8-15%; preferably, the mass fraction of the solvent in the electrolyte is 80-90%; preferably, the mass fraction of the additive in the electrolyte is 1-5%.
3. An electrolyte as claimed in claim 1, wherein: in the lithium salt, the mass ratio of lithium hexafluorophosphate to lithium bis (fluorosulfonyl) imide is 1-10: 1.
4. An electrolyte as claimed in claim 1, wherein: the solvent further comprises an ester solvent; preferably, the ester solvent includes ethyl methyl carbonate, ethyl propionate, and ethylene carbonate; preferably, in the solvent, the mass ratio of ethyl methyl carbonate, ethyl propionate and ethylene carbonate is 1-10: 1-5.
5. An electrolyte as claimed in claim 1, wherein: the glutaronitrile-based solvent includes at least one of glutaronitrile and 2-methylglutaronitrile.
6. An electrolyte as claimed in claim 4, wherein: the mass ratio of the glutaronitrile solvent to the ester solvent is 1: 1-2.
7. A method of preparing the electrolyte of any of claims 1 to 6, comprising the steps of:
s1: controlling the temperature and pressure, and adding the lithium salt into the solvent;
s2: and (4) adding the additive into the product obtained in the step S1 to obtain the product.
8. The method of claim 7, wherein the solvent is treated by melting, sucking, passing and batching before step S1.
9. The method according to claim 8, wherein the material melting treatment is carried out at a temperature of 60-70 ℃ for 5-7 h.
10. A lithium battery comprising the electrolyte according to any one of claims 1 to 6.
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