CN113948777A - Ionic liquid electrolyte and preparation method and application thereof - Google Patents

Ionic liquid electrolyte and preparation method and application thereof Download PDF

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CN113948777A
CN113948777A CN202111137851.7A CN202111137851A CN113948777A CN 113948777 A CN113948777 A CN 113948777A CN 202111137851 A CN202111137851 A CN 202111137851A CN 113948777 A CN113948777 A CN 113948777A
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ionic liquid
cation
imide
liquid electrolyte
lithium
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黄建宇
李帅
黄俏
唐亮
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Xiangtan University
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/056Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564Accumulators 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
    • H01M10/0566Liquid materials
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/058Construction or manufacture
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621Binders
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624Electric conductive fillers
    • H01M4/625Carbon or graphite
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention discloses an ionic liquid electrolyte and a preparation method and application thereof, wherein the ionic liquid electrolyte comprises ionic liquid and lithium salt; the ionic liquid comprises a cation and an anion; the cation is selected from C1‑C6Alkyl-substituted imidazolium cations, C1‑C6At least one of the alkyl-substituted pyrrole cations of (a); the anion is selected from at least one of fluorine-containing sulfimide anions; the lithium salt is at least one selected from fluorine-containing lithium sulfonyl imide. The existing electrolyte can be solved by using the ionic liquid electrolyte in the applicationPoor cycle performance in metal fluoride positive lithium ion batteries.

Description

Ionic liquid electrolyte and preparation method and application thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an ionic liquid electrolyte and a preparation method and application thereof.
Background
The lithium ion battery has the advantages of high energy density, high output voltage, long service life, environmental friendliness and the like, and is widely applied to the fields of new energy automobiles, portable equipment and the like. At present, liquid lithium ion batteries are mainly used as marketable lithium ion batteries, and the liquid lithium ion batteries have various potential safety hazards, such as flammable and explosive electrolytes, battery short circuits caused by polypropylene diaphragms which are heated and easily shrunk or melted, and the like, and the popularization and application of the liquid lithium ion batteries are limited by the factors. The electrolyte in the lithium battery is not used properly, which may bring environmental problems, so that it is imperative to find a new environment-friendly electrolyte.
The ferrous fluoride anode material is a novel high-specific-energy lithium ion battery anode material and is a future trend. In the application of the existing ferrous fluoride anode material to a liquid electrolyte: the solvent is generally composed of a carbonate (PC, EC, DMC, etc.), and the lithium salt is LiPF6,LiClO4,LiBF4,LiAsF6And the like. However, these conventional electrolytes have low safety, low high temperature resistance, easy combustion, low electrochemical window, and relatively poor solubility.
Disclosure of Invention
The invention aims to overcome the defects and provides an ionic liquid electrolyte, a preparation method and application thereof.
According to a first aspect of the present application, there is provided an ionic liquid electrolyte comprising an ionic liquid and a lithium salt;
the ionic liquid comprises a cation and an anion;
the cation is selected from C1-C6Alkyl-substituted imidazolium cations, C1-C6At least one of the alkyl-substituted pyrrole cations of (a);
the anion is selected from at least one of fluorine-containing sulfimide anions;
the lithium salt is at least one selected from fluorine-containing lithium sulfonyl imide.
Optionally, the C1-C6Alkyl-substituted imidazolium cations ofAt least one selected from the group consisting of 1-ethyl-3-methylimidazolium cation, 1-alkylimidazolium cation, and 1-alkyl-2, 3-dimethylimidazolium cation;
said C is1-C6The alkyl-substituted pyrrole cation of (a) is selected from at least one of a 1-methyl-1-propyl pyrrole cation, an N-methyl-N-butyl pyrrole cation, an N-alkyl N-methyl pyrrole cation;
the fluorine-containing sulfonyl imide anion is at least one of bis (trifluoromethanesulfonyl) imide anion, bis (fluorosulfonyl) imide anion, tetrafluoroborate anion and hexafluorophosphate anion.
Optionally, the ionic liquid is selected from 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide salt (EMIMTFSI), 1-methyl-1-propylpyrrol bis (trifluoromethanesulfonyl) imide salt (PYR)13TFSI), N-methyl-N-butylpyrrole bis (trifluoromethylsulfonyl) imide salt (PYR)14TFSI), 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide salt, 1-methyl-1-propylpyrroledi (fluorosulfonyl) imide salt, N-methyl-N-butylpyrrolidi (fluorosulfonyl) imide salt.
Optionally, the lithium salt of fluorine-containing sulfonyl imide is selected from at least one of lithium bis (trifluoromethyl) sulfonyl imide (LITFSI) and lithium bis (fluoro) sulfonyl imide (LTFSI).
Optionally, the concentration of the lithium salt in the ionic liquid electrolyte is 0.5-2 mol/L.
According to a second aspect of the present application, there is provided a method of producing the above ionic liquid electrolyte, the method comprising:
and mixing the ionic liquid and the lithium salt, and stirring to obtain the ionic liquid electrolyte.
Optionally, the stirring conditions are: the temperature is 40-70 ℃; the time is 10-18 h.
According to a third aspect of the present application, there is provided a lithium ion battery comprising an electrolyte; the electrolyte comprises the ionic liquid electrolyte.
Optionally, the method further comprises:
a positive electrode containing a positive electrode active material; the positive active material includes ferrous fluoride and Carbon Nanotubes (CNTs);
and a negative electrode, which is a lithium negative electrode.
Optionally, the carbon nanotubes are multi-walled carbon nanotubes.
Optionally, the multi-walled carbon nanotubes have a length of 0.5-2 μm.
Optionally, in the positive electrode active material, the mass ratio of the ferrous fluoride to the carbon nano tubes is 12-15: 3-6.
Optionally, the positive electrode further comprises a conductive agent and a binder;
the mass ratio of the conductive agent to the adhesive to the ferrous fluoride is 0.5-1.5:0.5-1.5: 7-9.
Optionally, the conductive agent is selected from conductive carbon black.
Optionally, the binder is selected from polyvinylidene fluoride (PVDF).
In this application, C1-C6In the alkyl-substituted imidazolium cation of (1)1-C6Refers to the number of carbon atoms in the alkyl group of the imidazolium cation; c1-C6In the alkyl-substituted pyrrole cation of (1)1-C6Refers to the number of carbon atoms in the alkyl group of the pyrrole cation.
The technical scheme of the invention has the following beneficial technical effects:
the ionic liquid in the ionic liquid electrolyte provided by the invention can form a stable electrolyte interface phase film on the surface of a metal fluoride anode, so that the cycle performance of the lithium ion battery is obviously improved, and the ionic liquid electrolyte has high cycle capacity retention rate, good safety and wide use temperature range and can be used at high temperature.
Drawings
FIG. 1 is an X-ray powder diffraction pattern of ferrous fluoride prepared by the present invention;
FIG. 2 is a Li/FeF2Cycling performance curves in sample # 1-4 # ionic liquid electrolyte;
FIG. 3 is a Li/FeF2Cycling performance curves in sample # 5-8 # ionic liquid electrolyte;
FIG. 4 is a Li/FeF2In sample No. 9-cycle performance profile in # 12 ionic liquid electrolyte;
FIG. 5 is a graph of electrochemical resistance performance of sample # 1- # 4 ionic liquid electrolyte at 25 deg.C;
FIG. 6 is a graph of electrochemical resistance performance of sample # 5-8 # ionic liquid electrolyte at 25 deg.C;
FIG. 7 is a graph of electrochemical resistance performance of sample # 9-12 ionic liquid electrolyte at 25 ℃;
FIG. 8 is a graph of electrochemical resistance performance of sample # 1- # 4 ionic liquid electrolyte at 60 ℃;
FIG. 9 is a graph of electrochemical resistance performance of sample # 5-8 # ionic liquid electrolyte at 60 ℃;
FIG. 10 is a graph of electrochemical resistance performance of sample # 9-12 ionic liquid electrolyte at 60 ℃.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The invention provides an ionic liquid electrolyte, which comprises an ionic liquid and a lithium salt; the ionic liquid comprises cations and anions; the cation is selected from C1-C6Alkyl-substituted imidazolium cations, C1-C6At least one of the alkyl-substituted pyrrole cations of (a); the anion is at least one of fluorine-containing sulfimide anions; the lithium salt is at least one selected from fluorine-containing lithium sulfonyl imide.
The ionic liquid electrolyte provided by the invention can be applied to a lithium ion battery taking ferrous fluoride as a positive electrode, wherein the ferrous fluoride is FeF2Is a typical transition metal fluoride, and the theoretical specific discharge capacity of the transition metal fluoride is 571mAh g-1Can be in FeF during charging and discharging2And Fe, to form 2 electron transfer. The ferrous fluoride is oneTypical transition metal fluorides, which are used in the positive electrode material of the novel transition type lithium battery, are represented. The ionic liquid has the advantages of high chemical stability, difficult volatilization and no combustion, and becomes the development trend of the current electrolyte. The ionic liquid electrolyte is applied to a lithium ion battery taking ferrous fluoride as a positive electrode, wherein the ionic liquid can form a stable electrolyte interface phase film on the surface of the ferrous fluoride positive electrode, so that the cycle performance of the battery is obviously improved, and the ionic liquid electrolyte has high cycle capacity retention rate, good safety and wide use temperature range, and can be used at high temperature.
The invention also provides a lithium ion battery, the active materials of the anode are ferrous fluoride and carbon nano tubes, the cathode is metallic lithium, and the following reactions can occur at the anode of the lithium ion battery:
Figure BDA0003282946170000041
the preparation method of the ionic liquid EMIMTFSI used in the examples of the application is as follows:
In a glove box filled with argon, equal amounts of N-methylimidazolium ring and bromoethane are reacted in cyclohexane as solvent at 80 ℃, magnetically stirred for 24h to obtain the crude product ethyltrimethylimidazolium bromide (EMIMIBr), which is purified by recrystallization from a mixture of ethyl acetate and isopropanol (volume ratio 1:1) to obtain pure white crystals EMIMIBr. Weighing EMIMIBr and LITFSI with equal amount of substances, dissolving in water, heating to 70 deg.C, and magnetically stirring for 24 hr to obtain hydrophobic phase EMIMTFSI final product. The product obtained, EMIMTFSI, was dried in vacuum at 120 ℃ for 72h in a vacuum oven.
Ionic liquid PYR used in the examples of this application13TFSI,PYR14The preparation method of TFSI is as follows:
with methyl pyrrole and bromopropane and bromobutane respectively, as 1:1, at 70 ℃ and acetonitrile as a reaction solvent to prepare bromo-1-methyl-1-propyl pyrrole, bromo-N-methyl-N-butyl pyrrole, and adding into a mixture of ethyl acetate and isopropanol (volume ratio is 1:1)And (5) performing recrystallization purification. Respectively weighing equal amount of PYR13Br,PYR14Br and LITFSI are dissolved in water, heated to 70 ℃, and magnetically stirred for 24 hours to obtain PYR of a hydrophobic phase13TFSI,PYR14TFSI final product. The obtained product was dried in vacuum at 120 ℃ for 72h in a vacuum oven.
The synthesis steps of the positive electrode active material used in the examples of the present application:
high purity grade (99.9%) iron powder (purchased from aladdin)1.3g (excess) was poured slowly in portions into 10g H2SiO4In the solution (the mass concentration is about 30 percent), a large amount of bubbles are generated by reaction, after standing for 24 hours, supernatant fluid is taken and centrifuged twice to ensure that excessive iron powder is removed, and light green clear FeSiF is obtained6And (3) precursor solution. Transferring the precursor solution into a 250ml beaker, adding 0.25g of multi-walled carbon nano-tube (the length is 2 mu m), diluting by about 50 times with 50ml of ultrapure water, adding 10ml of ultrapure water each time during dilution, dropwise adding a drop of triton solution, spreading the solution in a plastic box, standing for 24h for natural drying, putting the plastic box into a tubular furnace, annealing at 250 ℃ for 4h, cooling to room temperature, and taking out to obtain light yellow nano-sized FeF2And (3) powder. XRD characterization of the powder (results are shown in FIG. 1) and comparison with standard PDF card showed that the synthesized FeF2Does not contain any impurity phase and is high-purity nano powder.
The electrolyte only contains electrolyte, and other solvents do not need to be added.
EXAMPLE 1 Ionic liquid electrolyte 1# -12#, and
weighing a certain amount of LITFSI, transferring the LITFSI into a 20mL sample bottle, sucking 1mL of ionic liquid by using a syringe with a range of 10mL, dropwise adding the ionic liquid into a volumetric flask, slightly shaking while dropwise adding to fully dissolve lithium salt, and stirring the lithium salt for 12 hours on a stirrer at a rotating speed of 400r/min and a temperature of 50 ℃ to obtain the ionic liquid electrolyte with a certain concentration. Wherein the sample addition is shown in table 1:
TABLE 1
Figure BDA0003282946170000061
Example 2
With a positive electrode active material: conductive carbon black: polyvinylidene fluoride (PVDF) ═ 8: 1: weighing corresponding substances according to the mass ratio of 1, dissolving 0.05g of PVDF in 1mL of NMP (N-methylpyrrolidone), stirring at the rotating speed of 200r/min on a magnetic stirrer, and then pouring the composite powder of ferrous fluoride and CNT subjected to ball milling to form positive electrode slurry. And continuously adding NMP to moderate the viscosity of the slurry, stirring at room temperature for 36h, then coating the slurry on an aluminum foil, coating by using a coating scraper for 50 microns, and then placing the aluminum foil in a constant-temperature drying oven at 100 ℃ for drying for 24 h. And punching the dried pole piece into a circular pole piece with the diameter of 12mm by using a punching machine to obtain the lithium iron fluoride battery positive pole piece.
The positive pole piece of the battery is assembled in a 2016 button type half battery, the battery is compressed by a hydraulic press, and all the processes are operated in a glove box. After the operation is completed, the cell is taken out, and the open circuit voltage is measured to be about 3V, which is consistent with the standard open circuit voltage of a ferrous fluoride button type half cell.
The blue battery test system is adopted to carry out constant current charge-discharge cycle test on the battery, and the current density is 114.2mA g-1(1C=571mA g-1) The average active substance mass load of the pole piece is close to 1mg/cm within the voltage range of (1V-4V) 2And passing about 260 cycles of charge-discharge cycle test.
Long cycle performance analysis of different ionic liquid electrolytes (samples 1# -12#), and FIG. 2 shows Li/FeF2The cycle performance curve in the electrolyte (sample No. 1-4) containing different lithium salt concentrations in EMIMTFSI is 0.2C, the voltage range is 1-4V, the cycle performance of the ionic liquid electrolyte with the lithium salt concentration of 0.5mol/L is optimal, the first 20 circles are a rising trend, the 20 th circle specific capacity reaches 530mAh/g, the capacity loss is caused due to the first charge and discharge, part of the loss is from the redox decomposition of the electrolyte, and part of the loss is from the reaction of an electrode material and the electrolyte to form a surface film. After the 80 th circle, the capacity tends to be stable and is kept at 280mAh/g, and the capacity retention rate is 99 percent, which shows that the film layer formed on the surface of the electrode is opposite to electricityThe electrode has a protective effect and can inhibit further decomposition of the electrolyte. The initial capacity of the positive electrode material in lithium salt concentrations of 1.0 mol/L, 1.5 mol/L and 2.0mol/L is respectively 280mAh/g, 530mAh/g and 510mAh/g, and is higher than the concentration of 0.5 mol/L. It can be seen that an increase in the concentration of the lithium salt contributes to an increase in the conductivity. It can be seen that within the ionic liquid, EMIMTFSI, a suitable increase in lithium salt concentration contributes to a high conductivity of the cell, but the cycling performance is somewhat worse.
And analyzing the long-cycle performance of different ionic liquid electrolytes. As shown in fig. 3-4. PYR13The first-turn capacity of the TFSI ionic liquid electrolyte is higher than that of PYR14First capacity of TFSI ionic liquid electrolyte. FIG. 3 is a Li/FeF2In PYR13The TFSI contains the circulation performance curve of electrolytes (5# -8#) with different lithium salt concentrations, when the lithium salt concentration is 2.0mol/L, the discharge capacity of the first circle is up to 710mAh/g, and the discharge capacity is reduced obviously in the first 70 circles, which may be the electrolyte has decomposition reaction, so that the capacity is reduced. The overall capacity of the lithium salt tends to increase with increasing concentration of the lithium salt, indicating that the ionic liquid PYR is in the form of a solid13In the TFSI electrolyte, the concentration of lithium salts has a significant effect on its performance. At the concentration of 1.5mol/L, the capacity gradually tends to 410mAh/g at the 50 th circle and reaches a relatively stable state, which may form a layer of compact and uniform interface phase film (CEI film) on the surface of the positive electrode, thereby effectively protecting the effective decomposition of the positive electrode material in the circulation process and leading the coulombic efficiency to tend to be stable. FIG. 4 is a Li/FeF2In PYR14TFSI contains electrolyte (9# -12#) with different lithium salt concentrations, and the first loop capacities of 0.5mol/L,1.0mol/L,1.5mol/L and 2.0mol/L are respectively 480mAh/g,491mAh/g, 501mAh/g and 500 mAh/g. From the above results, it can be inferred that in PYR 14In the ionic liquid electrolyte such as TFSI, the capacity is not positively correlated with the conductivity of the electrolyte, and the wettability is preferably 1.5 mol/L. In the first 120 circles, the capacity is continuously reduced, then a relatively stable state is maintained, and the coulombic efficiency reaches 99%, which is supposed to be that a film layer formed on the surface of the electrode has a multi-electrode protection function, so that the further decomposition of the electrolyte can be inhibited. Several different electrolyte cycle performance comparisonsIn comparison, the ionic liquid PYR13The TFSI has the optimum performance of 1.5mol/L lithium salt concentration, and the capacity is maintained at 410mAh/g at 260 turns.
The electrochemical impedance performance analysis at 25 ℃ of different ionic liquid electrolytes, as shown in figures 5-7, are all the impedances measured at 25 ℃ at room temperature. From the impedance diagram, the ionic liquid PYR13The resistance value of the TFSI electrolyte (5# -8#) measured at 25 ℃ is the smallest. PYR13The TFSI electrolyte concentration was 600. omega. at 0.5mol/L, 250. omega. at 1.0mol/L, 1000. omega. at 1.5mol/L, and 550. omega. at 2.0 mol/L. From the above results, it can be inferred that at the concentration of 0.5mol/L and the concentration of 1.5mol/L, the CEI layer was formed, so that the resistance was increased. The ionic liquid EMIMTFSI electrolyte has the greatest resistance and the resistance of its electrolyte increases with increasing concentration. It is likely that the greater the concentration, the less its free ions, so the impedance increases. PYR 14The impedance of TFSI ionic liquid electrolyte (9# -12#) does not change much with the lithium salt concentration.
The electrochemical impedance performance analysis at 60 ℃ for different ionic liquid electrolytes, as shown in fig. 8-10, is the impedance measured at 60 ℃. The impedance value measured under this condition is much reduced as a whole. This indicates that the temperature is increased, the viscosity of the electrolyte is reduced, lithium ions are easier to migrate, the impedance is reduced, and the conductivity is improved. Ionic liquid PYR13TFSI electrolyte, with the lowest impedance of only 40 Ω at 1.5 mol/L. In the EMIMTFSI ionic liquid electrolyte, the impedance generally shows an increasing trend along with the increase of the concentration of the lithium salt, and at the concentration of 1.5mol/L, the impedance reaches 900 ohms, because in the electrolyte, the viscosity of the electrolyte is increased due to the increase of the concentration of the lithium salt, the ion shuttling is blocked, and the impedance is increased. Another possibility is that the electrolyte is incompatible with the ferrous fluoride positive electrode material and the electrolyte reacts easily on the positive electrode surface to form a non-uniform and non-dense CEI layer. PYR14The TFSI has a lower resistance value at 60 c than at 25 c. The impedance value was 100. omega. at a lithium salt concentration of 1.5 mol/L. The ionic liquid electrolyte is higher than room temperature in high-temperature environment Ion conduction effect is better under the environment, and the ion liquid PYR with the concentration of 1.5mol/L13The TFSI electrolyte has the advantages of minimum impedance, highest conductivity, best cycling stability and better compatibility with ferrous fluoride cathode materials.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.

Claims (10)

1. An ionic liquid electrolyte comprising an ionic liquid and a lithium salt;
the ionic liquid comprises a cation and an anion;
the cation is selected from C1-C6Alkyl-substituted imidazolium cations, C1-C6At least one of the alkyl-substituted pyrrole cations of (a);
the anion is selected from at least one of fluorine-containing sulfimide anions;
the lithium salt is at least one selected from fluorine-containing lithium sulfonyl imide.
2. The ionic liquid electrolyte of claim 1, said C1-C6The alkyl-substituted imidazolium cation of (a) is selected from at least one of 1-ethyl-3-methylimidazolium cation, 1-alkylimidazolium cation, and 1-alkyl-2, 3-dimethylimidazolium cation;
said C is1-C6The alkyl-substituted pyrrole cation of (a) is selected from at least one of a 1-methyl-1-propyl pyrrole cation, an N-methyl-N-butyl pyrrole cation, an N-alkyl N-methyl pyrrole cation;
the fluorine-containing sulfonyl imide anion is at least one of bis (trifluoromethanesulfonyl) imide anion, bis (fluorosulfonyl) imide anion, tetrafluoroborate anion and hexafluorophosphate anion.
3. An ionic liquid electrolyte according to claim 2, wherein the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazole bis-trifluoromethanesulfonimide salt, 1-methyl-1-propylpyrrole bis (trifluoromethanesulfonyl) imide salt, N-methyl-N-butylpyrrole bis (trifluoromethanesulfonyl) imide salt, 1-ethyl-3-methylimidazole bis-fluorosulfonyl imide salt, 1-methyl-1-propylpyrrole bis (fluorosulfonyl) imide salt, N-methyl-N-butylpyrrole bis (fluorosulfonyl) imide salt.
4. The ionic liquid electrolyte of claim 1, wherein the lithium salt of fluorosulfonyl imide is selected from at least one of lithium bistrifluoromethylsulfonyl imide and lithium salt of difluorosulfonyl imide.
5. The ionic liquid electrolyte of claim 1, wherein the concentration of the lithium salt in the ionic liquid electrolyte is 0.5-2 mol/L.
6. The method of producing an ionic liquid electrolyte according to any one of claims 1 to 5, comprising:
and mixing the ionic liquid and the lithium salt, and stirring to obtain the ionic liquid electrolyte.
7. A lithium ion battery comprising an electrolyte; the electrolyte solution includes the ionic liquid electrolyte according to any one of claims 1 to 5.
8. The lithium ion battery of claim 7, further comprising:
a positive electrode containing a positive electrode active material; the positive active material comprises ferrous fluoride and carbon nanotubes;
and a negative electrode, which is a lithium negative electrode.
9. The lithium ion battery according to claim 8, wherein the mass ratio of the ferrous fluoride to the carbon nanotubes in the positive electrode active material is 12-15: 3-6.
10. The lithium ion battery of claim 8, the positive electrode further comprising a conductive agent and a binder;
the mass ratio of the conductive agent to the adhesive to the ferrous fluoride is 0.5-1.5:0.5-1.5: 7-9.
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Citations (5)

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