CN111620822A - Imidazole ionic liquid and preparation method and application thereof - Google Patents
Imidazole ionic liquid and preparation method and application thereof Download PDFInfo
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- CN111620822A CN111620822A CN202010508190.3A CN202010508190A CN111620822A CN 111620822 A CN111620822 A CN 111620822A CN 202010508190 A CN202010508190 A CN 202010508190A CN 111620822 A CN111620822 A CN 111620822A
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- RAXXELZNTBOGNW-UHFFFAOYSA-N imidazole Natural products C1=CNC=N1 RAXXELZNTBOGNW-UHFFFAOYSA-N 0.000 title claims abstract description 241
- 239000002608 ionic liquid Substances 0.000 title claims abstract description 156
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000003792 electrolyte Substances 0.000 claims abstract description 63
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 34
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 34
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 claims description 102
- 238000006243 chemical reaction Methods 0.000 claims description 45
- 229910003002 lithium salt Inorganic materials 0.000 claims description 31
- 159000000002 lithium salts Chemical class 0.000 claims description 31
- 239000003960 organic solvent Substances 0.000 claims description 31
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical group CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 30
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 25
- 239000008367 deionised water Substances 0.000 claims description 23
- 229910021641 deionized water Inorganic materials 0.000 claims description 23
- 239000012071 phase Substances 0.000 claims description 22
- 238000003756 stirring Methods 0.000 claims description 22
- 239000007788 liquid Substances 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 21
- OSSNTDFYBPYIEC-UHFFFAOYSA-N 1-ethenylimidazole Chemical compound C=CN1C=CN=C1 OSSNTDFYBPYIEC-UHFFFAOYSA-N 0.000 claims description 18
- 238000002390 rotary evaporation Methods 0.000 claims description 18
- 238000000746 purification Methods 0.000 claims description 16
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 15
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 15
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 15
- 239000002904 solvent Substances 0.000 claims description 15
- -1 chloroalkyl ester Chemical class 0.000 claims description 14
- 229910017053 inorganic salt Inorganic materials 0.000 claims description 14
- 239000011259 mixed solution Substances 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 14
- 229910052757 nitrogen Inorganic materials 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 13
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 claims description 13
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 claims description 13
- 238000001291 vacuum drying Methods 0.000 claims description 12
- 229910001290 LiPF6 Inorganic materials 0.000 claims description 11
- QABLOFMHHSOFRJ-UHFFFAOYSA-N methyl 2-chloroacetate Chemical group COC(=O)CCl QABLOFMHHSOFRJ-UHFFFAOYSA-N 0.000 claims description 10
- 239000000376 reactant Substances 0.000 claims description 10
- 238000001514 detection method Methods 0.000 claims description 9
- 239000000243 solution Substances 0.000 claims description 8
- 239000007795 chemical reaction product Substances 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 239000002244 precipitate Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 229910013188 LiBOB Inorganic materials 0.000 claims description 6
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 6
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 6
- ZXMGHDIOOHOAAE-UHFFFAOYSA-N 1,1,1-trifluoro-n-(trifluoromethylsulfonyl)methanesulfonamide Chemical compound FC(F)(F)S(=O)(=O)NS(=O)(=O)C(F)(F)F ZXMGHDIOOHOAAE-UHFFFAOYSA-N 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- 101710134784 Agnoprotein Proteins 0.000 claims description 3
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000012074 organic phase Substances 0.000 claims description 3
- 238000010992 reflux Methods 0.000 claims description 3
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical group [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 2
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052794 bromium Inorganic materials 0.000 claims description 2
- 229910052801 chlorine Chemical group 0.000 claims description 2
- 239000000460 chlorine Chemical group 0.000 claims description 2
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 2
- 150000002148 esters Chemical class 0.000 claims description 2
- VEUUMBGHMNQHGO-UHFFFAOYSA-N ethyl chloroacetate Chemical compound CCOC(=O)CCl VEUUMBGHMNQHGO-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- RAXXELZNTBOGNW-UHFFFAOYSA-O Imidazolium Chemical compound C1=C[NH+]=CN1 RAXXELZNTBOGNW-UHFFFAOYSA-O 0.000 claims 4
- 125000001246 bromo group Chemical group Br* 0.000 claims 1
- 125000001309 chloro group Chemical group Cl* 0.000 claims 1
- 125000003342 alkenyl group Chemical group 0.000 abstract description 13
- 239000007772 electrode material Substances 0.000 abstract description 13
- 229910002099 LiNi0.5Mn1.5O4 Inorganic materials 0.000 abstract description 10
- 125000004185 ester group Chemical group 0.000 abstract description 10
- 125000000524 functional group Chemical group 0.000 abstract description 7
- 239000007774 positive electrode material Substances 0.000 abstract description 4
- 239000007787 solid Substances 0.000 description 20
- 239000000047 product Substances 0.000 description 18
- 230000014759 maintenance of location Effects 0.000 description 10
- 238000005349 anion exchange Methods 0.000 description 8
- 238000002474 experimental method Methods 0.000 description 8
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 8
- 238000011160 research Methods 0.000 description 7
- 239000000463 material Substances 0.000 description 6
- 238000006116 polymerization reaction Methods 0.000 description 6
- JDIIGWSSTNUWGK-UHFFFAOYSA-N 1h-imidazol-3-ium;chloride Chemical compound [Cl-].[NH2+]1C=CN=C1 JDIIGWSSTNUWGK-UHFFFAOYSA-N 0.000 description 5
- 150000001768 cations Chemical class 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 150000001335 aliphatic alkanes Chemical class 0.000 description 4
- 150000001450 anions Chemical class 0.000 description 4
- 238000005342 ion exchange Methods 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 229910001961 silver nitrate Inorganic materials 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 238000004448 titration Methods 0.000 description 4
- 229920001567 vinyl ester resin Polymers 0.000 description 4
- 239000002000 Electrolyte additive Substances 0.000 description 3
- 229910013716 LiNi Inorganic materials 0.000 description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 230000002238 attenuated effect Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 239000004570 mortar (masonry) Substances 0.000 description 3
- 238000001644 13C nuclear magnetic resonance spectroscopy Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 150000001348 alkyl chlorides Chemical class 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 239000010405 anode material Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005611 electricity Effects 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002367 halogens Chemical group 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 238000006864 oxidative decomposition reaction Methods 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000012827 research and development Methods 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 238000005160 1H NMR spectroscopy Methods 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- 229910005143 FSO2 Inorganic materials 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000012983 electrochemical energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 125000001033 ether group Chemical group 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 125000002560 nitrile group Chemical group 0.000 description 1
- 238000000655 nuclear magnetic resonance spectrum Methods 0.000 description 1
- 230000005311 nuclear magnetism Effects 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D233/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings
- C07D233/54—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members
- C07D233/56—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring carbon atoms
- C07D233/60—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring carbon atoms with hydrocarbon radicals, substituted by oxygen or sulfur atoms, attached to ring nitrogen atoms
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- C07D233/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings
- C07D233/54—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members
- C07D233/56—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring carbon atoms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- 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
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Abstract
The invention relates to imidazole ionic liquid and a preparation method and application thereof. The structural formula of the ionic liquid is as follows. Wherein R is1Is CHCH2，R2Is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1; y is‑Is BF4 ‑，PF6 ‑，TFSI‑，N(CN)2 ‑，FSI‑Or (FSO)2)2N‑. The functional group in the imidazole ionic liquid is alkenyl and ester group, the alkenyl is introduced intoThe compatibility and stability of the electrolyte and the electrode material are improved. In the preparation process, proper parameters are selected to introduce the ester group, so that the electrochemical window and the electrochemical stability of the ionic liquid are improved, and the conductivity can also be improved. The ionic liquid obtained by the invention is applied to LiNi0.5Mn1.5O4The high-voltage lithium ion battery which is a positive electrode material can improve the safety, the stability and the electrochemical performance of the lithium ion battery.
Description
Technical Field
The invention relates to the technical field of ionic liquid, and mainly researches functionalized ionic liquid and application thereof in lithium ion battery electrolyte.
Background
At present, energy problems such as energy supply and energy acquisition become hot topics in the current society. Meanwhile, fossil fuels represented by combustion of thermal energy such as coal, oil, and natural gas also cause global problems such as air pollution and environmental pollution. Electrochemical energy storage systems, i.e., batteries, can conveniently and quickly store chemical energy and convert the stored energy into devices that can store electrical energy in an efficient, pollution-free manner.
Lithium ion batteries have become an important part of our lives. Rechargeable lithium ion batteries have been widely used in electric vehicles, hybrid electric vehicles, and consumer electronics products due to their advantages of high specific capacity, high rate performance, and long service life. However, current lithium ion batteries still have problems in applications such as higher energy density requirements and stability in high temperature and high voltage environments. Among these problems, the development of high-temperature and high-voltage electrolytes remains a challenge. The current commercial electrolyte is generally made of LiPF6And carbonate solvents, and because the electrolyte has poor oxidation stability and is easy to generate thermal decomposition in a high-temperature environment (above 55 ℃), the decomposition products can damage the structure of an electrode to cause the performance reduction of the battery, and the defects make the battery not meet the requirements of the high-temperature and high-voltage environmentThe following use requirements.
LiNi0.5Mn1.5O4The material is known as an ideal electrode material for next generation high voltage LIBs due to the advantages of large energy density, wide raw material source, high working voltage and the like. However, the development of this material is hindered by the limitations of commercial electrolytes. Mainly because most of commercial electrolytes use carbonate as an organic solvent, the organic solvent can undergo severe oxidative decomposition reaction when the LIBs working voltage reaches above 4.5V (vs. Li/Li +), thereby reducing the electrochemical performance of the electrolyte. Further, LiPF in the electrolyte6Can react with water to generate HF. And HF will further dissolve LiNi0.5Mn1.5O4Ni and Mn ions in the material destroy the structure of the electrode material, so that the capacity of the electrode material is seriously attenuated, and the cyclicity of the battery is further reduced. Therefore, LiNi was sought0.5Mn1.5O4The electrolyte matched with the material can improve the utilization rate of the material, and compared with the development of a new electrolyte system, the electrolyte additive is developed to improve the performance of the electrolyte, so that the electrolyte has important significance in the research and development of high-voltage LIBs.
The ionic liquid serving as a novel green chemical reaction medium has the advantages of low melting point, difficult volatilization, wide electrochemical window, close relation between the property and the application and the structure, and can replace the common traditional solvent ionic liquid under specific conditions, and the ionic liquid has certain unique performance, higher thermodynamic and chemical stability, designability of molecules and the like, so that the ionic liquid is a hot point of research in recent years. Because of the properties of green and designability, ionic liquids containing functional groups are one of the hot spots in the research field of the ionic liquids at present. The functionalized ionic liquid is realized by introducing functional groups, such as amine groups, ether groups, nitrile groups, ester groups, alkenyl groups and the like, on cations or anions of the ionic liquid. The functional group is introduced to endow the ionic liquid with special performance, so that the functionalized ionic liquid has many characteristics which are not possessed by the traditional ionic liquid.
The wide electrochemical window characteristic of the ionic liquid can widen the working voltage of the lithium ion battery, so that the ionic liquid is used in the electrolyte of the lithium ion battery, and is expected to solve the problem of high working electricity of the electrolyteEasily decomposed under reduced pressure. Gives a brand new research direction, and the subject group is dedicated to research on the improvement of the oxidation resistance of the electrolyte by taking the ionic liquid as the electrolyte additive of the lithium ion battery so as to meet the requirement of high-voltage LiNi0.5Mn1.5O4The requirement of the material provides a certain reference value for the research and development of the high-voltage-resistant electrolyte. Meanwhile, in the battery, the compatibility and stability of the electrode material still have a great problem, mainly because the electrochemical performance of the currently used ionic liquid is not excellent enough.
Therefore, a new functionalized ionic liquid is synthesized and used as an electrolyte additive, and the lithium ion battery has a wide electrochemical window and good compatibility and stability with electrode materials.
Disclosure of Invention
The invention relates to an imidazole ionic liquid, a preparation method and application thereof, wherein the structural formula of the ionic liquid is shown as the following, and R of the ionic liquid is1Is CHCH2，R2Is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1; y is-Is BF4 -,PF6 -，TFSI-，N(CN)2 -Or FSI-One kind of (1). The functional groups in the functionalized ionic liquid are alkenyl and ester groups, and the alkenyl is introduced to improve the compatibility and stability of the electrolyte and the electrode material. In the preparation process, proper parameters are selected to introduce the ester group, so that the electrochemical window and the electrochemical stability of the ionic liquid are improved, and the conductivity can also be improved. It is applied to LiNi0.5Mn1.5O4The high-voltage lithium ion battery which is a positive electrode material can improve the safety, the stability and the electrochemical performance of the lithium ion battery.
The technical scheme of the invention is that
An imidazole ionic liquid, wherein the structural formula of the ionic liquid is as follows:
wherein R is1Is CHCH2，R2Is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1; y is-Is BF4 -，PF6 -，TFSI-，N(CN)2 -，FSI-Or (FSO)2)2N-。
The preparation method of the imidazole ionic liquid comprises the following steps:
(1) under the protection of nitrogen atmosphere, dissolving 1-vinyl imidazole and chloroalkyl ester in a solvent, then stirring and refluxing at 65-80 ℃ for 30-48 hours to obtain a reactant, stopping the reaction, performing rotary evaporation, and placing the reaction product after the reaction at 50-65 ℃ for vacuum drying for 20-30 hours to obtain yellow transparent viscous liquid, so as to obtain chlorinated 1-vinyl-3-ester-based imidazole halide with the following structural formula:
wherein, the mol ratio is 1-vinyl imidazole: a chloroalkyl ester 1:1 to 1.2; the solvent is acetonitrile or dichloromethane, and 200-300 ml of solvent is added to each mol of 1-vinylimidazole; the chloro-ester is methyl chloroacetate or ethyl chloroacetate.
R is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1, Y is halogen bromine or chlorine;
(2) the 1-vinyl-3-ester imidazole halide and the inorganic salt M are mixed+Y-Mixing the mixture with deionized water, and then reacting for 7-14 hours at 40-50 ℃ under the protection of nitrogen gas to obtain the 1-vinyl-3-ester imidazole bis (trifluoromethyl sulfonyl) imide ionic liquid with the following structure:
wherein M is+Is Li; y is-Is BF4 -，PF6 -，TFSI-，N(CN)2 -，FSI-Or (FSO)2)2N-Adding 150-200 ml of deionized water, 1-vinyl-3-ester imidazole halide and inorganic salt M into each mole of 1-vinyl-3-ester imidazole halide+Y-The molar ratio of (a) to (b) is 1:1 to 1: 1.2.
The molar ratio of the 1-vinylimidazole to the chloroalkyl ester is preferably 1: 1.1.
The molar ratio of the 1-vinyl-3-ester imidazole halide to the inorganic salt is preferably 1: 1.1.
And (3) the protective gas in the step (1) and the step (2) is nitrogen or argon.
In the step (2), the method further comprises the following steps: mixing the 1-vinyl-3-ester imidazole halide with an inorganic salt M+Y-And stirring deionized water at 40-50 ℃ for reaction, and then separating and purifying the ionic liquid, wherein the separation and purification process comprises the following steps:
putting the mixed solution obtained after the reaction into dichloromethane to extract an organic phase, then collecting a dichloromethane phase, and washing the dichloromethane phase by using deionized water until saturated AgNO is used3No precipitate is generated by solvent detection; and carrying out rotary evaporation treatment on the treated solution to remove dichloromethane, and drying to obtain the purified imidazole ionic liquid.
The application of the imidazole ionic liquid is used for preparing the electrolyte of the lithium ion battery.
The electrolyte comprises: organic solvents, lithium salts and ionic liquids; wherein the mass percent of the lithium salt is 1-10%, the mass percent of the ionic liquid is 1-30%, and the mass percent of the organic solvent is 70-80%. The imidazole ionic liquid has the following structure:
r is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is0 or 1; y is-Is BF4 -，PF6 -，TFSI-，N(CN)2 -，FSI-Or (FSO)2)2N-One kind of (1).
The organic solvent is a mixed solution consisting of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, wherein the weight ratio of ethylene carbonate: dimethyl carbonate: the volume ratio of the methyl ethyl carbonate is 1:1: 1-1: 1.5: 2.
The lithium salt is LiPF6、LiBF4LiBOB, LiDFOB or LiTFSI.
The preparation method of the ionic liquid electrolyte is characterized by comprising the following steps of:
mixing ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate according to the proportion to obtain an organic solvent; and mixing an organic solvent and the imidazole ionic liquid, adding a lithium salt after stirring, and continuously stirring until the lithium salt is completely dissolved to obtain the ionic liquid electrolyte.
Wherein the lithium salt is LiPF6、LiBF4LiBOB, LiDFOB or LiTFSI.
The molar ratio of the 1-vinylimidazole to the chloro-ester is preferably 1: 1.1.
The molar ratio of the 1-vinyl-3-ester based imidazole halide to the inorganic salt is preferably 1: 1.1.
The invention has the substantive characteristics that:
the cation of the imidazole ionic liquid obtained by the invention is a 1-vinyl-3-ester imidazole cation, and compared with the traditional imidazole ionic liquid, the imidazole ionic liquid has alkenyl groups, so that the electrochemical stability of the ionic liquid can be improved, and the compatibility and stability of an electrolyte and an electrode material are improved. Particularly, the reduction stability is ensured, so that the electrochemical window is higher, and the introduction of the alkenyl ensures that the imidazole ionic liquid can be reduced before lithium ions are inserted into the graphite electrode and generate a stable SEI film on the surface of the electrode through a polymerization reaction, so that the cycle performance of the lithium ion battery is improved. An ester group is introduced into the N-3 position, so that the electrochemical window and the electrochemical stability of the ionic liquid are improved, and the conductivity can also be improved. Through performance detection, the imidazole ionic liquid has a wider electrochemical window and better electrochemical stability than the traditional ionic liquid.
In the process of the electrolyte, the inventor obtains that the control of the reaction temperature and the reaction time is very important after a great deal of research and experiments, for example, the temperature of the second step of anion exchange is normal temperature in general, but the invention is heated to 40-50 ℃; the reaction is incomplete when the temperature is too low (when the 1-vinyl-3-ester halide is generated in the first step, the liquid is better kept at 40 ℃ by respectively standing and treating at room temperature and 40 ℃, the anion exchange in the second step is more complete by increasing the temperature to 40-50 ℃, the time is too short, the reaction is incomplete, the time is too long, side reactions are generated, and the purity of the ionic liquid is influenced, compared with the ionic liquid used in the high-pressure electrolyte disclosed before the subject group, the ionic liquid is mostly replaced by a ternary element before, and the operation period is longer (about 100 hours; the invention only needs about 70 hours).
The invention has the beneficial effects that:
the preparation method of the imidazole ionic liquid electrolyte has the advantages of simple process, easy control of reaction and suitability for industrial production, and the prepared ionic liquid electrolyte has excellent electrochemical performance, a wider electrochemical window, high stability and good safety and can be applied to the field of high-voltage lithium ion batteries.
The concrete expression is as follows: the obtained 1-vinyl-3-ester imidazole ionic liquid has high electrochemical stability, an alkenyl functional group is arranged in the selected structure, the compatibility and stability, particularly the reduction stability, of the electrolyte and an electrode material are improved, and a stable SEI film is generated through a polymerization reaction on the surface of an electrode. And then an ester group is introduced into the N-3 position, so that the electrochemical window and the electrochemical stability of the ionic liquid are improved, and the conductivity can also be improved. The lithium ion battery anode material is applied to lithium ion battery electrolyte as an additive, and LiNi is used as a positive electrode material0.5Mn1.5O4Good circulation effect and high capacity retention rate.
Compared with the traditional electrolyte, the imidazole ionic liquid electrolyte has the advantages that the ionic liquid exists, so that electricity is generatedThe electrochemical stability of the electrolyte is obviously improved, so that the safety of the battery is improved; meanwhile, the stable formation of an SEI film of the negative electrode is promoted, and the cyclicity of the battery is improved. The cation of the imidazole ionic liquid is 1-vinyl-3-ester imidazole cation, compared with the traditional imidazole ionic liquid, the electrochemical stability of the ionic liquid is higher due to the existence of alkenyl and ester functional groups, the alkenyl has the function of improving the compatibility and stability, particularly the reduction stability, of the electrolyte and an electrode material, and a stable SEI film is generated through polymerization reaction on the surface of an electrode. The introduction of the ester group improves the electrochemical window and electrochemical stability of the ionic liquid, and can also improve the conductivity. Imidazole ionic liquid electrolyte prepared from the same is applied to high-voltage LiNi0.5Mn1.5O4In the Li lithium ion battery, the discharge capacity retention rate after 50 cycles is about 93 percent. See example 4 for details.
Drawings
FIG. 1 is the nuclear magnetic hydrogen spectrum of the ionic liquid obtained in example 1;
FIG. 2 is the NMR spectrum of the ionic liquid obtained in example 1;
fig. 3 is a charge-discharge cycle diagram of the lithium ion battery obtained in example 4.
Detailed Description
The preparation of the imidazole ionic liquid and the application thereof in the electrolyte of the high-voltage lithium ion battery are further described with reference to the accompanying drawings and specific examples.
One embodiment of the imidazole-based ionic liquid has the following structural formula:
r is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1; y is-Is BF4 -,PF6 -，TFSI-，N(CN)2 -,FSI-,(FSO2)2N-One kind of (1).
The cation of the imidazole ionic liquid obtained by the invention is a 1-vinyl-3-ester imidazole cation, and compared with the traditional imidazole ionic liquid, the imidazole ionic liquid has alkenyl groups, so that the electrochemical stability of the ionic liquid can be improved, and the compatibility and stability of an electrolyte and an electrode material are improved. Particularly, the reduction stability is ensured, so that the electrochemical window is higher, and the introduction of the alkenyl enables the imidazole ionic liquid to be reduced before lithium ions are inserted into the graphite negative electrode, and a stable SEI film is generated on the surface of the electrode through a polymerization reaction, so that the cycle performance of the lithium ion battery is improved. An ester group is introduced into the N-3 position, so that the electrochemical window and the electrochemical stability of the ionic liquid are improved, and the conductivity can also be improved. Through performance detection, the imidazole ionic liquid has a wider electrochemical window and better electrochemical stability than the traditional ionic liquid.
In addition, the implementation also provides a preparation method of the imidazole ionic liquid, which comprises the following steps:
drying and removing impurities from reactants before reaction in the atmosphere of protective gas nitrogen, firstly drying 1-vinylimidazole in a drying oven at 60 ℃ for 12 hours, dissolving 1-vinylimidazole and chloroalkyl ester in a solvent, and performing multiple groups of experiments according to the proportion of 1: 1.1-1: 1.3, stirring and refluxing for reaction at 65-80 ℃ for 30-48 hours to obtain a reactant, stopping the reaction, performing rotary evaporation, and placing the reaction product after the reaction at 50-65 ℃ for vacuum drying for 20-30 hours to obtain a yellow transparent viscous liquid, thus obtaining the 1-vinyl-3-ester imidazole halide with the following structural formula. To give the following formula 1-vinyl-3-ester imidazole halide:
r is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1; y is-Is halogen.
In other preferred embodiments, the molar ratio of 1-vinylimidazole to chloroalkyl ester is 1: 1.1.
Under nitrogenUnder the protection of gas, dissolving the 1-vinyl-3-ester imidazole halide in deionized water according to the ratio of 1: 1-1: 1.2, and reacting with an inorganic salt M at the temperature of 40-50 DEG C+Y-Reacting for 7-14 hours to obtain the 1-vinyl-3-ester imidazole bis (trifluoromethyl sulfonyl) imide ionic liquid with the following structure.
M+Is Li; y is-Is BF4 -，PF6 -，TFSI-，N(CN)2 -，FSI-Or (FSO)2)2N-One kind of (1). The volume ratio of the 1-vinyl-3-ester imidazole halide to the deionized water is 1mol: 150-200 ml.
In a further preferred embodiment the 1-vinyl-3-ester group is reacted with an inorganic salt M+Y-The molar ratio was 1: 1.1.
In addition, the preparation method of the imidazole ionic liquid further comprises a purification step of dissolving the 1-vinyl-3-ester imidazole halide and inorganic salt in deionized water, stirring and reacting at 40-50 ℃, and then generating new ionic liquid, wherein the step is operated at normal temperature in a conventional experiment, but when the 1-vinyl-3-ester halide is generated, the liquid is found to be better maintained at 40 ℃ by standing and treating at room temperature and 40 ℃ respectively, and a polymerization side reaction is not generated by increasing the temperature, and the separation and purification process comprises the following steps:
returning the mixed solution obtained after the reaction to dichloromethane for extracting an organic phase, then collecting the dichloromethane phase, and washing the dichloromethane phase for a plurality of times by using deionized water until saturated AgNO is used3No precipitate is generated by solvent detection; and carrying out rotary evaporation treatment on the treated solution to remove dichloromethane, and drying to obtain the purified imidazole ionic liquid.
The preparation method of the imidazole ionic liquid comprises the steps of firstly preparing 1-vinyl-3-ester imidazole halide through the reaction of 1-vinyl imidazole and alkyl chloride, finally carrying out ion exchange reaction on inorganic salt containing target anions and 1-vinyl-3-ester imidazole halide, and purifying and drying the product after the ion exchange reaction to obtain the imidazole ionic liquid. The process method is simple to operate, the reaction is easy to control, the yield is high (82% -85%), the method is suitable for expanded production, and the prepared imidazole ionic liquid has excellent electrochemical performance and is applied to the field of high-voltage lithium ion batteries.
In addition, the embodiment also provides an ionic liquid electrolyte of the high-voltage lithium ion battery and a preparation method thereof.
The ionic liquid electrolyte includes an organic solvent, an ionic liquid, and a lithium salt. Wherein the ionic liquid is the imidazole ionic liquid. The organic solvent is a mixed solution consisting of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC), wherein the weight ratio of ethylene carbonate: the ratio of dimethyl carbonate to ethyl methyl carbonate is 1:1: 1-1: 1.5:2, and the lithium salt is LiPF6、LiBF4LiBOB, LiDFOB or LiTFSI. The mass fraction of the lithium salt is 1-10%, the mass fraction of the ionic liquid is 1-30%, and the mass fraction of the organic solvent is 70-80%.
Compared with the traditional lithium ion battery organic electrolyte, the ionic liquid electrolyte has the advantages that the stability of the electrolyte is obviously improved due to the existence of the ionic liquid, so that the safety of the battery is improved, a stable SEI film is generated, and the compatibility and the stability of the electrolyte and an electrode material are improved.
The preparation method of the ionic liquid comprises the following steps:
preparing the imidazole ionic liquid.
According to the ethylene carbonate: the volume ratio of dimethyl carbonate to ethyl methyl carbonate is 1:1: 1-1: 1.5:2, and the dimethyl carbonate and the ethyl methyl carbonate are prepared into an organic solvent.
According to the mass percent of the organic solvent being 70-80%, the mass percent of the lithium salt being 1-10%, the lithium salt being LiPF6、LiBF4LiBOB, LiDFOB or LiTFSI. The mass percent of the ionic liquid is 0-30 percent, namely the mass percent of the ionic liquid is respectively added into the ionic liquid according to 0 percent, 5 percent, 10 percent, 15 percent, 20 percent, 25 percent and 30 percentAnd adding lithium salt into the mixed solvent in the organic solvent, and continuously stirring until the lithium salt is completely dissolved to obtain the ionic liquid electrolyte.
The preparation method of the ionic liquid electrolyte is simple, the reaction is easy to control, the safety is high, the method is suitable for industrial production, and the prepared ionic liquid electrolyte has excellent electrochemical performance, a wide electrochemical window, high stability and good safety and can be applied to the field of high-voltage electrolytes.
The following describes the preparation of imidazole ionic liquids, their application in lithium ion battery electrolytes, and their performance tests with reference to specific examples.
Example 1
Under the protection of nitrogen atmosphere, 0.1mol of 1-vinyl imidazole, 0.1mol of methyl chloroacetate and 30ml of acetonitrile are added into a 100ml three-neck flask, then the mixture is stirred and refluxed for reaction for 48 hours at 70 ℃ to obtain a reactant, after the reaction is stopped, unreacted acetonitrile and methyl chloroacetate are removed by rotary evaporation, and the reaction product after the reaction is placed at 60 ℃ for vacuum drying for 24 hours to obtain a yellow transparent liquid: chlorinated 1-vinyl-3-acetic acid methyl ester imidazole.
In the experiment, the inventor finds that after the product (1-vinyl-3-methyl acetate imidazole chloride) is kept still for 3 hours at normal temperature, the liquid begins to be gradually converted into a solid, the color of the solid is changed from obvious yellow to off-white solid, and if the solid is directly used for second-step anion exchange, the solid is obviously completely insoluble after being stirred for 24 hours at room temperature. Improvements are needed. In the improvement, the product purification problem is considered, except that the product is subjected to rotary evaporation and drying, and after a purification step is added, the operation is carried out again, so that yellow transparent liquid stably existing at normal temperature is generated. In the operation process of the reaction, the purification step is further refined, and the high-purity ionic liquid, namely the 1-vinyl-ester imidazole chloride salt, is obtained as far as possible. The yield thereof was found to be 83.2%.
Anion exchange synthesis of the ionic liquid used finally. Into a 100ml flask were charged 0.075mol of 1-vinyl-3-acetic acid methyl ester imidazole chloride prepared as described above, and 0.07875mol of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) (structural formula: LiTFSI)
)15ml of deionized water to obtain a mixed solution, placing the mixed solution in an oil bath pot, stirring and reacting for 12 hours at the temperature of 45 ℃ under the protection of nitrogen, and generating an organic liquid phase which is insoluble in the deionized water; adding 20ml of dichloromethane, stirring for 3 hours, standing for layering, collecting a dichloromethane phase, fully washing the dichloromethane phase for three to five times by using deionized water until no precipitate is generated by titration detection of silver nitrate, removing dichloromethane in an alkane phase obtained in the dichloromethane phase by rotary evaporation, and placing the treated product at 60 ℃ for vacuum drying for 24 hours to finally obtain a yellow brown viscous liquid 1-vinyl-3-ester imidazole bis (trifluoromethanesulfonyl) imide salt.
Under nitrogen protection, according to ethylene carbonate: mixing dimethyl carbonate and ethyl methyl carbonate according to the volume ratio of 1:1.5:2 to prepare an organic solvent, adding the organic solvent into the organic solvent according to the mass percent of 5% of lithium salt, and stirring until the lithium salt is completely dissolved. And then adding the prepared imidazole ionic liquid into the solution according to the proportion that the mass percent of the ionic liquid is 5 percent to obtain the ionic liquid electrolytes with different concentrations. The lithium salt being LiPF6。
To ionic liquids1The HNMR test infers the hydrogen atom type,13CNMR testing infers carbon atom type. Taking 7mg of ionic liquid and 5.5ml of D2And placing the O solvent in a nuclear magnetic tube, uniformly mixing, and carrying out H spectrum test. 20mg of ionic liquid and 5.5ml of D are taken2And placing the O solvent in a nuclear magnetic tube, and uniformly mixing to perform C spectrum test.
Fig. 1 is a graph H of the ionic liquid, and fig. 2 is a graph C of the ionic liquid.
The hydrogen spectrum of the ionic liquid was analyzed as follows:
1H NMR(400MHz，D2O)，(ppm)：5.743-5.788(t，1H，CH﹦CH2),5.370-5.399(d,2H，CH﹦CH2)，5.149(s，2H，N﹣CH2-C＝O)，3.743(s，3H，O＝C－O－CH3)，7.773(s，1H，N＝CH－N)，7.536(s，1H，N－CH＝CH－N)，7.072-7.132(d, 1H, N-CH ═ CH-N) (where s: indicates a single peak; d: double seam; t: triplet; m: multiple peak).
The carbon spectrum analysis of the ionic liquid is as follows:
13C NMR(101MHz,D2O),(ppm),121.077(C＝C－N)，123.042(C＝C－N)，117.413-118.391(C－S－N－S－C)，127.134(N－C＝C－N)，51.201(C－C＝N)。
by nuclear magnetism characterization, the ionic liquid 1-vinyl-3-methyl acetate imidazole bis (trifluoromethylsulfonyl) imide can be confirmed to be synthesized as shown in figures 1 and 2.
Thus, 1-vinyl-3-ester imidazole bis (trifluoromethanesulfonyl) imide salt is obtained.
Example 2
Under the protection of nitrogen atmosphere, 0.1mol of 1-vinyl imidazole, 0.11mol of methyl chloroacetate and 30ml of acetonitrile are added into a 100ml three-neck flask, then the mixture is stirred and refluxed for reaction for 48 hours at 70 ℃ to obtain a reactant, after the reaction is stopped, unreacted acetonitrile and methyl chloroacetate are removed by rotary evaporation, and the reaction product after the reaction is placed at 60 ℃ for vacuum drying for 24 hours to obtain a yellow transparent liquid: chlorinated 1-vinyl-3-acetic acid methyl ester imidazole. In the experiment, the resultant is stood for 3 hours at normal temperature, the liquid begins to be gradually converted into solid, the color of the solid is changed from obvious yellow to off-white solid, and if the solid is directly used for second-step anion exchange, the solid is obviously and completely insoluble after being stirred for 24 hours at room temperature. Improvements are needed. In the improvement, the product purification problem is considered, except the rotary evaporation and drying of the product, after the purification step is added, the operation is carried out again, and yellow transparent liquid which stably exists at normal temperature is generated. In the operation process of the reaction, the purification step is further refined, and the high-purity ionic liquid, namely the 1-vinyl-ester imidazole chloride salt, is obtained as far as possible. The yield thereof was found to be 83.5%.
Anion exchange synthesis of the ionic liquid used finally. Under the protection of nitrogen, respectively adding 0.075mol of the prepared chlorinated 1-vinyl-3-methyl acetate imidazole halide, 0.079mol of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) and 12ml of deionized water into a 100ml flask to obtain a mixed solution, placing the mixed solution into an oil bath kettle, and stirring for reaction for 14 hours at the temperature of 45 ℃ under the protection of nitrogen to generate an organic liquid phase insoluble in the deionized water; adding 20ml of dichloromethane, stirring for three hours, standing for layering, collecting a dichloromethane phase, fully washing the dichloromethane phase for three to five times by using deionized water until no precipitate is generated by titration detection of silver nitrate, removing dichloromethane in an alkane phase obtained in the dichloromethane phase by rotary evaporation, and placing the treated product at 60 ℃ for vacuum drying for 36 hours to finally obtain a yellow brown viscous liquid 1-vinyl-3-ester imidazole bis (trifluoromethanesulfonyl) imide salt.
Under nitrogen protection, according to ethylene carbonate: mixing dimethyl carbonate and ethyl methyl carbonate according to the volume ratio of 1:1.5:2 to prepare an organic solvent, adding the organic solvent into the organic solvent according to the mass percent of 5% of lithium salt, and stirring until the lithium salt is completely dissolved. And then adding the prepared imidazole ionic liquid into the solution according to the proportion that the mass percent of the ionic liquid is 10 percent to obtain the ionic liquid electrolytes with different concentrations. The lithium salt being LiPF6。
Example 3
Under the protection of nitrogen atmosphere, 0.1mol of 1-vinyl imidazole, 0.105mol of methyl chloroacetate and 30ml of acetonitrile are added into a 100ml three-neck flask, then the mixture is stirred and refluxed for reaction for 48 hours at 70 ℃ to obtain a reactant, after the reaction is stopped, unreacted acetonitrile and methyl chloroacetate are removed by rotary evaporation, and the reaction product after the reaction is placed at 60 ℃ for vacuum drying for 24 hours to obtain a yellow transparent liquid: chlorinated 1-vinyl-3-acetic acid methyl ester imidazole. In the experiment, the resultant is stood for 3 hours at normal temperature, the liquid begins to be gradually converted into solid, the color of the solid is changed from obvious yellow to off-white solid, and if the solid is directly used for second-step anion exchange, the solid is obviously and completely insoluble after being stirred for 24 hours at room temperature. Improvements are needed. In the improvement, the purification problem of the product is considered, besides rotary evaporation and drying of the product, the reactant is also dried and purified, and after the purification step is added, the operation is carried out again to generate yellow transparent liquid which stably exists at normal temperature. In the operation process of the reaction, the purification step is further refined, and the high-purity ionic liquid, namely the 1-vinyl-ester imidazole chloride salt, is obtained as far as possible. The yield thereof was found to be 83.4%.
Under the protection of nitrogen, respectively adding 0.075mol of the prepared chlorinated 1-vinyl-3-methyl acetate imidazole, 0.083mol of bis (trifluoromethanesulfonyl) lithium imide (LiTFSI) and 15ml of deionized water into a 100ml flask to obtain a mixed solution, placing the mixed solution into an oil bath kettle, and stirring for reaction for 14 hours at the temperature of 50 ℃ under the protection of nitrogen to generate an organic liquid phase insoluble in the deionized water; adding 20ml of dichloromethane, stirring for three hours, standing for layering, collecting a dichloromethane phase, fully washing the dichloromethane phase for three to five times by using deionized water until no precipitate is generated by titration detection of silver nitrate, removing dichloromethane in an alkane phase obtained in the dichloromethane phase by rotary evaporation, and placing the treated product at 60 ℃ for vacuum drying for 28 hours to obtain a yellow brown viscous liquid 1-vinyl-3-ester imidazole bis (trifluoromethanesulfonyl) imide salt.
Under nitrogen protection, according to ethylene carbonate: the volume ratio of dimethyl carbonate to ethyl methyl carbonate is 1: 1.2: 1.5, mixing to prepare an organic solvent, adding the organic solvent into the organic solvent according to the mass percent of the lithium salt of 5%, and stirring until the lithium salt is completely dissolved. And then adding the prepared imidazole ionic liquid into the solution according to the mass percent of the ionic liquid being 20% to obtain the ionic liquid electrolytes with different concentrations. The lithium salt being LiPF6。
Example 4
Under the protection of nitrogen atmosphere, 0.1mol of 1-vinyl imidazole, 0.11mol of methyl chloroacetate and 30ml of acetonitrile are added into a 100ml three-neck flask, then the mixture is stirred and refluxed for reaction for 48 hours at 70 ℃ to obtain a reactant, after the reaction is stopped, unreacted acetonitrile and methyl chloroacetate are removed by rotary evaporation, and the reaction product after the reaction is placed at 60 ℃ for vacuum drying for 24 hours to obtain a yellow transparent liquid: chlorinated 1-vinyl-3-acetic acid methyl ester imidazole. In the experiment, the resultant is stood for 3 hours at normal temperature, the liquid begins to be gradually converted into solid, the color of the solid is changed from obvious yellow to off-white solid, and if the solid is directly used for second-step anion exchange, the solid is obviously and completely insoluble after being stirred for 24 hours at room temperature. Improvements are needed. In the improvement, the purification problem of the product is considered, besides rotary evaporation and drying of the product, the reactant is also dried and purified, and after the purification step is added, the operation is carried out again to generate yellow transparent liquid which stably exists at normal temperature. In the operation process of the reaction, the purification step is further refined, and the high-purity ionic liquid, namely the 1-vinyl-ester imidazole chloride salt, is obtained as far as possible. The yield thereof was found to be 83.6%.
Under the protection of nitrogen, respectively adding 0.075mol of the prepared chlorinated 1-vinyl-3-methyl acetate imidazole, 0.083mol of bis (trifluoromethanesulfonyl) lithium imide (LiTFSI) and 15ml of deionized water into a 100ml flask to obtain a mixed solution, placing the mixed solution into an oil bath kettle, and stirring for reaction for 12 hours at the temperature of 50 ℃ under the protection of nitrogen to generate an organic liquid phase insoluble in the deionized water; adding 20ml of dichloromethane, stirring for three hours, standing for layering, collecting a dichloromethane phase, fully washing the dichloromethane phase for three to five times by using deionized water until no precipitate is generated by titration detection of silver nitrate, removing dichloromethane in an alkane phase obtained in the dichloromethane phase by rotary evaporation, and placing the treated product at 60 ℃ for vacuum drying for 36 hours to finally obtain a yellow brown viscous liquid 1-vinyl-3-ester imidazole bis (trifluoromethanesulfonyl) imide salt.
Under nitrogen protection, according to ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate volume ratio 1:1: 1.5, mixing to prepare an organic solvent, adding the organic solvent into the organic solvent according to the mass percent of the lithium salt of 15%, and stirring until the lithium salt is completely dissolved. And then adding the prepared imidazole ionic liquid into the solution according to the mass percent of 30% of the ionic liquid to obtain the ionic liquid electrolytes with different concentrations. The lithium salt being LiPF6。
Performance testing
Application of the Ionic liquid electrolyte prepared in example 4 to LiNi0.5Mn1.5O4In the lithium ion battery, a cyclic charge and discharge performance test is carried out, and the steps are as follows:
according to the mass ratio of 8: 1:1, respectively and accurately weighing 8gLiNi0.5Mn1.5O4The preparation method comprises the following steps of (1) putting PVDF into a cleaned agate mortar, adding N-methylpyrrolidone (NMP) into the cleaned agate mortar, and grinding the mixture for 20 minutes to obtain a transparent and uniform paste; then weighing the LiNi0.5Mn1.5O4The active material and acetylene black were put in a mortar and ground for 40 minutes to be uniformly mixed to prepare a slurry.
And (3) uniformly coating the slurry on an aluminum foil cleaned by ethanol by using a four-side coater, drying the aluminum foil in a constant temperature box at 60 ℃ for 12 hours, rolling the dried pole piece into 75% of the original thickness by using a roll press, drying the pole piece in a vacuum drying box at 120 ℃ for 24 hours, and removing a volatile solvent NMP to prepare the positive pole piece. Punching the prepared pole piece into a wafer with the diameter of 16mm, taking the wafer as the anode of the lithium ion battery, and sealing and storing the wafer in a glove box filled with argon; a polypropylene porous diaphragm is selected as a lithium ion battery diaphragm, and a lithium sheet is selected as a lithium battery cathode. The electrolyte prepared in example 4 was placed in the positive and negative electrodes in a glove box, an LIR2032 type button cell was used and assembled, and then mechanically sealed on a sealing machine.
As can be seen from FIG. 2, the ionic liquid is prepared into an electrolyte and assembled into LiNi0.5Mn1.5O4The Li battery is charged and discharged under the multiplying power of 0.1C, after 50 times of circulation, the specific discharge capacity is not obviously attenuated, and the highest specific discharge capacity is 134.9 mAh.g-1And the specific discharge capacity after 50 cycles is 126.1 mAh.g-1The capacity retention rate can reach 93 percent. Has higher capacity retention rate. Therefore, the electrolyte added with the ionic liquid has good conductivity.
The prepared imidazole electrolyte has low viscosity, an alkenyl group exists in a selected functional group structure, the compatibility and stability, particularly the reduction stability, of the electrolyte and an electrode material are improved, and a stable SEI film is generated through a polymerization reaction on the surface of an electrode. And then an ester group is introduced into the N-3 position, so that the electrochemical window and the electrochemical stability of the ionic liquid are improved, and the ionic liquid can also be improvedHigh electrical conductivity. The lithium ion battery anode material is applied to lithium ion battery electrolyte as an additive, and LiNi is used as a positive electrode material0.5Mn1.5O4Good circulation effect and high capacity retention rate.
It can be seen from the above examples that, in the present invention, 1-vinyl imidazole and alkyl chloride are reacted to prepare 1-vinyl-3-ester imidazole halide, then inorganic salt containing target anion and 1-vinyl-3-ester imidazole halide are subjected to ion exchange reaction, and the product after the ion exchange reaction is purified and dried, so as to obtain the imidazole ionic liquid. The process method is simple to operate, low in temperature, easy to operate and control in reaction and high in product yield (82% -85%), is suitable for being applied to industrialization, and meanwhile, the prepared ionic liquid has excellent electrochemical performance and is suitable for the field of high-voltage lithium ion batteries.
The ionic liquid is prepared into electrolyte to be assembled into LiNi0.5Mn1.5O4The Li battery is tested in a charge-discharge cycle under the multiplying power of 0.1C, after 50 cycles, the discharge specific capacity is not obviously attenuated, and the highest discharge specific capacity is 134.9mAh g-1And the specific discharge capacity after 50 cycles is 126.1 mAh.g-1The capacity retention rate reaches 93 percent. The battery has higher capacity retention rate which is about 10 percent higher than the discharge capacity retention rate of the common EC/DMC battery. The addition of the ionic liquid inhibits the oxidative decomposition of the organic solvent in the circulation process, and the solution is completely solvated into free anions and cations, so that the conductivity of the electrolyte is increased along with the increase of the number of ions in a certain range, and the charge and discharge of the battery are facilitated. In the research of the same experiment personnel, the capacity retention rate is basically about 93 percent, which shows that the added synthesized ionic liquid has better performance. The capacity retention rate of the battery is improved, and the cycle life of the battery is further prolonged, so that the ionic liquid synthesized by the inventor is applied to electrolyte as an additive, and the ionic liquid is easy to prepare, has a short reaction period, and has a possibility of industrialization.
It should be understood that the above description is illustrative of the preferred embodiment of the invention and is not to be construed as limiting the scope of the invention.
The invention is not the best known technology.
Claims (9)
1. An imidazole ionic liquid, which is characterized in that the ionic liquid has the following structural formula:
wherein R is1Is CHCH2，R2Is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is 0 or 1; y is-Is BF4 -，PF6 -，TFSI-，N(CN)2 -，FSI-Or (FSO)2)2N-。
2. A process for the preparation of imidazolium ionic liquids according to claim 1, characterized in that it comprises the following steps:
(1) under the protection of nitrogen atmosphere, dissolving 1-vinyl imidazole and chloroalkyl ester in a solvent, then stirring and refluxing at 65-80 ℃ for 30-48 hours to obtain a reactant, stopping the reaction, performing rotary evaporation, and placing the reaction product after the reaction at 50-65 ℃ for vacuum drying for 20-30 hours to obtain yellow transparent viscous liquid, so as to obtain chlorinated 1-vinyl-3-ester-based imidazole halide with the following structural formula:
wherein, the mol ratio is 1-vinyl imidazole: a chloroalkyl ester 1:1 to 1.2; the solvent is acetonitrile or dichloromethane, and 200-300 ml of solvent is added to each mol of 1-vinylimidazole;
r is CH2(CH2)aCOO(CH2)bCH3A is 0 or 1, b is0 or 1, Y is bromine or chlorine;
(2) the 1-vinyl-3-ester imidazole halide and the inorganic salt M are mixed+Y-Mixing the mixture with deionized water, and then reacting for 7-14 hours at 40-50 ℃ under the protection of nitrogen gas to obtain the 1-vinyl-3-ester imidazole bis (trifluoromethyl sulfonyl) imide ionic liquid with the following structure:
wherein M is+Is Li; y is-Is BF4 -，PF6 -，TFSI-，N(CN)2 -，FSI-Or (FSO)2)2N-Adding 150-200 ml of deionized water, 1-vinyl-3-ester imidazole halide and inorganic salt M into each mole of 1-vinyl-3-ester imidazole halide+Y-The molar ratio of (a) to (b) is 1:1 to 1: 1.2.
3. The method for preparing imidazole ionic liquid according to claim 2, wherein the chloro-based ester is methyl chloroacetate or ethyl chloroacetate.
4. The process for the preparation of imidazolium ionic liquids according to claim 2, characterized in that the molar ratio of the 1-vinylimidazole to the chloroalkyl ester is preferably 1: 1.1;
the molar ratio of the 1-vinyl-3-ester imidazole halide to the inorganic salt is preferably 1: 1.1.
5. The method for preparing imidazole ionic liquid according to claim 2, wherein the shielding gas in step (1) and step (2) is nitrogen or argon.
6. The method for preparing imidazole ionic liquid according to claim 2, characterized in that in the step (2), the method further comprises the following steps: mixing the 1-vinyl-3-ester imidazole halide with an inorganic salt M+Y-And go toAfter the ionic water is stirred and reacts at the temperature of 40-50 ℃, the ionic liquid is separated and purified, and the separation and purification process comprises the following steps:
putting the mixed solution obtained after the reaction into dichloromethane to extract an organic phase, then collecting a dichloromethane phase, and washing the dichloromethane phase by using deionized water until saturated AgNO is used3No precipitate is generated by solvent detection; and carrying out rotary evaporation treatment on the treated solution to remove dichloromethane, and drying to obtain the purified imidazole ionic liquid.
7. Use of the imidazolium ionic liquids according to claim 1 for the production of electrolytes for lithium ion batteries.
8. Use of an imidazolium ionic liquid according to claim 7, characterized in that the electrolyte comprises: organic solvents, lithium salts and ionic liquids; wherein, the mass percent of the lithium salt is 1-10%, the mass percent of the ionic liquid is 1-30%, and the mass percent of the organic solvent is 70-80%;
the organic solvent is a mixed solution consisting of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, wherein the weight ratio of ethylene carbonate: dimethyl carbonate: the volume ratio of the methyl ethyl carbonate is 1:1: 1-1: 1.5: 2;
the lithium salt is LiPF6、LiBF4LiBOB, LiDFOB or LiTFSI.
9. The method of preparing the electrolyte of claim 8, comprising the steps of:
mixing ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate according to the proportion to obtain an organic solvent; mixing an organic solvent and the imidazole ionic liquid, adding a lithium salt after stirring, and continuously stirring until the lithium salt is completely dissolved to obtain the ionic liquid electrolyte;
wherein the lithium salt is LiPF6、LiBF4LiBOB, LiDFOB or LiTFSI.
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