JP6157318B2 - Carbazole compound and lithium ion battery to which carbazole compound is added - Google Patents

Description

  The present invention relates to a carbazole compound useful as an overcharge inhibitor, an electrolytic solution for a lithium ion battery containing the carbazole compound, and a lithium ion battery using the electrolytic solution.

  Lithium ion batteries have a structure in which a metal oxide lithium salt is used as a positive electrode, graphite or the like is used as a negative electrode, and an electrolyte solution such as lithium hexafluorophosphate dissolved in an organic solvent is filled between both electrodes. Lithium ion batteries are widely used in mobile phones, personal computers, and even aircraft, but when charged beyond the specified capacity (overcharge), the organic solvent used in the positive electrode and electrolyte solution decomposes and battery elements May cause expansion and explosion, which is a major issue in terms of safety.

  The overcharge preventing agent is an agent that protects the battery constituent member by undergoing oxidation or reduction prior to the battery constituent member such as an electrode during overcharge, and delivering charges to the counter electrode by its own diffusion. Up to now, as an overcharge inhibitor used for a lithium ion battery, for example, there are compounds disclosed in Patent Documents 1 to 3, but there is no example in which carbazoles are used as an overcharge inhibitor.

  Moreover, although the substance similar to the carbazole compound of this invention is disclosed by patent document 4 or 5, it differs from the carbazole compound of this invention characterized by having a fluoroalkyl group on a carbazole nitrogen atom. Furthermore, Patent Documents 4 and 5 have no description using carbazoles as an overcharge inhibitor.

JP 1997-017447 A WO2007-097912 WO2006-094069 Special table 2012-505860 gazette JP-A-10-134845

  An object of the present invention is to provide a carbazole compound having an effect of preventing overcharge in a lithium ion battery, an electrolyte solution for a lithium ion battery having an overcharge prevention effect by containing the carbazole compound, and the electrolyte solution. Another object of the present invention is to provide a lithium ion battery in which overcharge is suppressed.

  As a result of intensive studies to solve the above problems, the present inventors have found that the carbazole compound represented by the general formula (1) has an oxidation potential suitable for preventing overcharge in lithium ion batteries and excellent redox resistance. In addition, the lithium ion battery electrolyte solution containing the present compound and the lithium ion battery using the electrolyte solution have an effect of suppressing overcharge as compared to the case of not containing the compound. The headline and the present invention were completed.

  That is, the present invention relates to the general formula (1)

(Wherein, R ¹ and R ² each independently represents a fluoroalkyl group having 1 to 6 carbon atoms).

  The present invention also provides a general formula (2)

(Wherein R ¹ represents a fluoroalkyl group having 1 to 6 carbon atoms) and a general formula R ² OSO ₂ CF ₃ (wherein R ² represents 1 carbon atom) And a trifluoromethanesulfonic acid ester represented by the general formula (1), wherein the trifluoromethanesulfonic acid ester represented by (6) is reacted in the presence of a base.

(Wherein R ¹ and R ² each independently represents a fluoroalkyl group having 1 to 6 carbon atoms).

  Moreover, this invention relates to the electrolyte solution for lithium ion batteries containing the carbazole compound shown by General formula (1).

  Furthermore, this invention relates to the lithium ion battery which uses the electrolyte solution for lithium ion batteries containing the carbazole compound shown by General formula (1).

  The present invention is described in further detail below.

The definitions of R ¹ and R ² in the carbazole compound of the present invention will be described.

The C1-C6 fluoroalkyl group represented by R ¹ and R ² may be any of a linear, branched or cyclic fluoroalkyl group, such as a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, 2 , 2,2-trifluoroethyl group, 1,1-difluoroethyl group, 2,2-difluoroethyl group, perfluoropropyl group, 2,2,3,3,3-pentafluoropropyl group, 2,2,3 , 3-tetrafluoropropyl group, 3,3,3-trifluoropropyl group, 1,1-difluoropropyl group, perfluoroisopropyl group, 2,2,2-trifluoro-1- (trifluoromethyl) ethyl group, Perfluorocyclopropyl group, 2,2,3,3-tetrafluorocyclopropyl group, perfluorobutyl group, 2,2,3,3,4,4,4 Heptafluorobutyl group, 3,3,4,4,4-pentafluorobutyl group, 4,4,4-trifluorobutyl group, 1,2,2,3,3,3-hexafluoro-1- (tri Fluoromethyl) propyl group, 1- (trifluoromethyl) propyl group, 1-methyl-3,3,3-trifluoropropyl group, perfluorocyclobutyl group, 2,2,3,3,4,4-hexafluoro Cyclobutyl group, perfluoropentyl group, 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, 3,3,4,4,5,5,5-heptafluoropentyl group, 4,4,5,5,5-pentafluoropentyl group, 5,5,5-trifluoropentyl group, 1,2,2,3,3,3-hexafluoro-1- (perfluoroethyl) propyl group, 2,2,3,3,3- Pentafluoro-1- (perfluoroethyl) propyl group, perfluorocyclopentyl group, perfluorohexyl group, 2,2,3,3,4,4,5,5,6,6,6-undecafluorohexyl group, 3, 3,4,4,5,5,6,6,6-nonafluorohexyl group, 4,4,5,5,6,6,6-heptafluorohexyl group, 5,5,6,6,6- Pentafluorohexyl group, 6,6,6-trifluorohexyl group, perfluorocyclohexyl group and the like can be exemplified. A fluoroalkyl group on a straight chain, specifically a trifluoromethyl group, a difluoromethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, and a 2,2-difluoro, in terms of good solubility in the electrolyte An ethyl group, a perfluoropropyl group, or a 2,2,3,3,3-pentafluoropropyl group or a 2,2,3,3-tetrafluoropropyl group is preferred, and a 2,2-difluoroethyl group is easy in synthesis. 2,2,2-trifluoroethyl group and 2,2,3,3-tetrafluoropropyl group are more preferable, and 2,2,2-trifluoroethyl group is more preferable.

  Next, the manufacturing method of this invention is demonstrated.

  The carbazole compound (1) of the present invention can be produced by the method shown in the following reaction formula (3).

(In the formula, R ¹ and R ² each independently represents a fluoroalkyl group having 1 to 6 carbon atoms.)
In the production method of the present invention, 3,6-dihydroxycarbazole (2) is reacted with a base and subsequently reacted with a trifluoromethanesulfonic acid ester represented by R ² -OSO ₂ CF ₃ , to thereby produce the carbazole compound (1 The target product can be obtained in high yield by applying general Williamson synthesis reaction conditions.

  3,6-Dihydroxycarbazole used in the production method of the present invention can be produced using the method shown in Reference Examples-1 to 1-3.

  Examples of the base that can be used in the production method of the present invention include metal hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide, carbonates such as sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate, and potassium acetate. , Acetates such as sodium acetate, phosphates such as potassium phosphate and sodium phosphate, metal alkoxides such as sodium methoxide, potassium methoxide, sodium ethoxide, potassium isopropyl oxide and potassium tert-butoxide, sodium hydride, Metal hydrides such as potassium hydride and calcium hydride, alkyl metals such as ethyl magnesium chloride, isopropyl magnesium bromide, methyl lithium and butyl lithium, lithium diisopropylamide, lithium 2,2,6,6-tetramethylpiperidide Gold It can be exemplified amides. From the viewpoint of easy handling, carbonates, metal alkoxides or metal hydrides are preferred, and metal hydrides are more preferred. Although there is no restriction | limiting in particular in the molar ratio of a base and 3, 6- dihydroxy carbazole, The ratio suitably selected from 1: 2-10: 1 is preferable at the point of a good yield, and it is 1: 1-1 from an economical viewpoint. A ratio appropriately selected from 4: 1 is more preferable.

The trifluoromethanesulfonic acid ester represented by R ² -OSO ₂ CF ₃ can be produced according to a general synthesis method well known to those skilled in the art, or a commercially available product may be used. Although there is no restriction | limiting in particular in the molar ratio of a trifluoromethanesulfonic acid ester and 3, 6- dihydroxy carbazole, The ratio suitably selected from 1: 2-10: 1 is preferable at the point with a sufficient yield, and 1: 1-4. A ratio appropriately selected from 1 is more preferable economically.

  The production method of the present invention can be carried out in a solvent. There is no restriction | limiting in particular in the solvent which can be used, What is necessary is just a solvent which does not inhibit reaction. Specific examples of the solvent include ethers such as diethyl ether, tetrahydrofuran (THF), dioxane, aromatic hydrocarbons such as toluene, xylene, mesitylene, dimethylformamide (DMF), dimethyl sulfoxide, and the like. May be mixed at an arbitrary ratio. There is no restriction | limiting in particular in the usage-amount of a solvent. It is desirable to use THF in terms of a good yield.

  Although there is no restriction | limiting in particular in the reaction temperature at the time of implementing the manufacturing method of this invention, it can implement at the temperature suitably selected from 0-150 degreeC, and 20-20 degreeC is a point with a good yield. It is preferable to carry out at an appropriately selected temperature.

  The carbazole compound (1) of the present invention can be obtained by performing a usual treatment after the reaction is completed. If necessary, it may be purified by distillation, recrystallization, column chromatography or sublimation.

  Next, a method for preparing an electrolytic solution for a lithium ion battery containing the carbazole compound of the present invention (hereinafter referred to as the electrolytic solution of the present invention) will be described.

  The electrolytic solution of the present invention can be prepared by adding the carbazole compound of the present invention to a lithium ion battery electrolytic solution.

  The electrolyte solution for lithium ion batteries is not particularly limited as long as those skilled in the art normally use, and commercially available products may be used. Moreover, the electrolyte solution for lithium ion batteries can also be obtained by dissolving the supporting electrolyte in an organic solvent. Supporting electrolytes include lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, lithium trifluoromethanesulfonate, lithium bis (trifluoromethanesulfone ) Imido, tetrakis (perfluorophenyl) lithium borate and the like can be exemplified, and lithium tetrafluoroborate or lithium hexafluorophosphate is preferred from the viewpoint of good performance of the lithium ion battery. Examples of the organic solvent used in the electrolyte for lithium ion batteries include carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and 4-fluoroethylene carbonate, methyl formate, ethyl formate, propyl formate, and methyl acetate. , Ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, γ-lactone, esters, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,4-dioxane Such as ether, acetonitrile, propionitrile, valeronitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, nitrile such as 3-methoxypropionitrile, N, N-dimethyl Formamide, N, N- dimethylacetamide, N- methylpyrrolidinone, can be exemplified N- methyloxazolidinone amides, dimethylsulfoxide and the like, may be used by mixing them. From the viewpoint of good solubility, an ester or a carbonate is preferable, and from the viewpoint of good performance of a lithium ion battery, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or a mixed solvent thereof is more preferable.

  When preparing the electrolytic solution of the present invention, the amount of the carbazole compound of the present invention added to the electrolytic solution for a lithium ion battery is preferably an amount appropriately selected from 0.01% by weight to 20% by weight. Further, it is more preferable that the amount is appropriately selected from 0.1% by weight or more and 10% by weight or less from the viewpoint of high overcharge prevention effect.

  Next, a method for producing a lithium ion battery (hereinafter referred to as the lithium ion battery of the present invention) using the electrolytic solution of the present invention will be described.

  The lithium ion battery of the present invention is prepared by sandwiching a separator between a positive electrode and a negative electrode, storing them in a cell case, and then injecting the electrolytic solution of the present invention. The material of the positive electrode is not particularly limited as long as it is a material commonly used by those skilled in the art. Specifically, lithium cobaltate, lithium manganate, lithium nickelate, lithium (manganese-cobalt composite oxide), lithium (nickel- (Manganese-cobalt composite oxide), lithium vanadium pentoxide, lithium vanadate, lithium (olivine-type iron phosphate), and the like. Lithium cobaltate, lithium manganate, lithium nickelate, lithium (manganese-cobalt composite oxide), lithium (nickel-manganese-cobalt composite oxide) or lithium (olivine iron phosphate) in terms of good battery performance Is preferred. The material of the negative electrode is not particularly limited as long as it can reversibly occlude and release lithium. Specifically, carbon such as lithium metal, glassy carbon, natural graphite, aluminum, silicon, germanium, tin, lead An alloy of lithium and one or more elements selected from indium, zinc and titanium, lithium titanate, phosphorus; vanadium; tin; copper; nickel; cobalt; lithium titanium containing one or more elements selected from iron A composite oxide etc. can be illustrated. In view of good battery performance, glassy carbon, natural graphite, silicon; tin; an alloy of lithium and one or more elements selected from titanium and titanium, or lithium titanate is preferable. The material of the separator is not particularly limited as long as it is usually used by those skilled in the art, and specific examples include polyolefin resin, fluorine resin, glass fiber, polyester resin, aromatic polyamide resin, polyoxyalkylene resin, and the like. can do. From the viewpoint of good battery performance, polyolefin resin or fluorine resin is preferable. The material of the cell case is not particularly limited as long as those skilled in the art normally use, and specific examples include stainless steel, aluminum alloy, titanium alloy, nickel alloy and the like. From the viewpoint of good durability, stainless steel or titanium alloy is preferable.

  The carbazole compound of the present invention is useful as an overcharge inhibitor that suppresses overcharge of a lithium ion battery, and can improve the safety of a lithium ion battery using an electrolyte for a lithium ion battery containing the same. .

  Next, although an Example, a reference example, a test example, and a comparative example demonstrate this invention in detail, this invention is not limited to these.

The following analysis method was used for identification of the carbazole compound of the present invention. ^For measurement of ¹ H-NMR and ¹⁹ F-NMR, Bruker ULTRASHIELD PLUS AVANCE III (400 MHz and 376 MHz) was used. ¹ H-NMR was measured using deuterated chloroform (CDCl ₃ ) or deuterated acetone as a measurement solvent and tetramethylsilane (TMS) as an internal standard substance. ¹⁹ F-NMR was measured using deuterated chloroform (CDCl ₃ ) or deuterated acetone as a measurement solvent and benzotrifluoride as an internal standard substance. Mass spectrometry was performed using GCMS-QP2010 manufactured by SHIMADZU. The melting point (mp) was measured using MP70 manufactured by METTLER TRADE. Cyclic voltammetry (CV) was measured using HSV-100 manufactured by Hokuto Denko Corporation. For CV measurement, an ethylene carbonate / ethyl methyl carbonate mixed solution (weight ratio: 3/7) containing 10 mM of the carbazole compound of the present invention and 0.1 M of a supporting electrolyte (tetrabutylammonium hexafluorophosphate) was prepared, Glassy carbon was inserted as a working electrode, Ag / AgCl as a reference electrode, and platinum as a counter electrode, and scanning was performed at 30, 50, 100, and 200 mV / s. From the results of CV measurement, the oxidation-reduction potential (E _1/2 ) and the diffusion coefficient D were calculated. E _1/2 is the half-wave potential of the oxidation and reduction peaks in the reversible voltagram. The diffusion coefficient D (cm ² / s) is given by equation (4)
I _p = 2.69 × 10 ⁵ n ^(3/2) AD ^(1/2) v ^(1/2) c (4)
(Wherein I _p is the oxidation peak current value (A), n is the number of mobile electrons, A is the working electrode area (cm ² ), v is the potential scanning speed (V / s), and c is the concentration of the carbazole compound ( mol / cm ³ ).

Example-1

Under an argon atmosphere, 3,6-dihydroxy-N- (2,2,2-trifluoroethyl) carbazole (2.01 g, 7.11 mmol) synthesized in Reference Example-3 was dissolved in THF (50 mL). Sodium hydride (60% oil dispersion, 587 mg, 14.6 mmol) was added thereto at 0 ° C., and the mixture was stirred at the same temperature for 30 minutes. The temperature of the solution was raised to room temperature, trifluoromethanesulfonic acid (2,2,2-trifluoroethyl) (3.80 g, 16.4 mmol) was added, and the mixture was stirred for 22 hours with heating under reflux. Chloroform and water were added to the reaction solution, the aqueous layer was separated, and the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography (eluent: chloroform / hexane) and recrystallization (chloroform / hexane), and 3,6-bis (2,2,2-trifluoroethoxy) -N- (2, 2,2-Trifluoroethyl) carbazole was obtained as a white solid (mp: 147.9-148.3 ° C.) (2.07 g, yield 65%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.46 (q, J = 8.2 Hz, 4H), δ 4.73 (q, J = 8.7 Hz, 2H), δ 7.19 (dd, J = 8 .8, 2.5 Hz, 2H), δ 7.34 (d, J = 8.8 Hz, 2H), δ 7.56 (d, J = 2.5 Hz, 2H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-74.5 (t, J = 8.2 Hz, 6F), δ-70.9 (t, J = 8.7 Hz, 3F).
MS (EI, 0.92 V): m / z (%) = 445 (M ^<+> , 76), 362 (100), 223 (30).
E1 _{/ 2} : 1.31 V (vs. Ag _/ AgCl).
D: 2.9 × 10 ⁻⁶ cm ² / s.

Reference Example-1

Under an argon atmosphere, sodium ethoxide (8.94 g, 131 mmol), 3,6-dibromocarbazole (7.00 g, 21.5 mmol), copper (I) iodide (8.20 g, 43.1 mmol), DMF (7 mL) and ethanol (24.5 mL) were added and stirred at 120 ° C. for 20 hours. After completion of the reaction, ethyl acetate was added to the reaction solution, silica gel filtration was performed, and the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography (eluent: ethyl acetate / hexane) to give 3,6-diethoxycarbazole as a white solid (4.39 g, yield 80%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 1.47 (t, J = 7.0 Hz, 6H), δ 4.14 (q, J = 7.0 Hz, 4H), δ 7.04 (dd, J = 8 .7, 2.5 Hz, 2H), δ 7.27 (d, J = 8.7 Hz, 2H), δ 7.48 (d, J = 2.5 Hz, 2H), δ 7.74 (brs, 1H).

Reference example-2

Under an argon atmosphere, 3,6-diethoxycarbazole (5.01 g, 19.6 mmol) synthesized in Reference Example-1 was dissolved in THF (100 mL). The solution was cooled to 0 ° C., an n-butyllithium / hexane solution (1.60 M, 14.7 mL, 23.5 mmol) was slowly added dropwise, stirred for 45 minutes, and then concentrated under reduced pressure at room temperature. The resulting residue was dissolved by adding THF (100 mL) and N, N′-dimethylpropyleneurea (10 mL), and then the solution was cooled to 0 ° C. and trifluoromethanesulfonic acid (2,2,2-trifluoro). Ethyl) (8.05 g, 34.7 mmol) was added, and the mixture was stirred at the same temperature for 1 hour and further at room temperature for 16 hours. After completion of the reaction, chloroform and saturated aqueous ammonium chloride were added to the reaction solution, the aqueous layer was separated, and the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography (eluent: chloroform / hexane), and 3,6-diethoxy-N- (2,2,2-trifluoroethyl) carbazole was converted into a white solid (mp: 140.9 to 141.2 ° C.) (3.81 g, yield 58%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 1.47 (t, J = 7.0 Hz, 6H), δ 4.14 (q, J = 7.0 Hz, 4H), δ 4.71 (q, J = 8) 8 Hz, 2H), δ 7.10 (dd, J = 8.9, 2.5 Hz, 2H), δ 7.27 (d, J = 8.9 Hz, 2H), δ 7.49 (d, J = 2. 5Hz, 2H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-71.0 (t, J = 8.8 Hz, 3F).
MS (EI, 0.92 V): m / z (%) = 337 (M ⁺ , 95), 308 (100), 280 (42).
E1 _{/ 2} : 1.10 V (vs. Ag _/ AgCl).
D: 3.6 × 10 ⁻⁶ cm ² / s.

Reference example-3

Under an argon atmosphere, 3,6-diethoxy-N- (2,2,2-trifluoroethyl) carbazole (3.71 g, 11.0 mmol) synthesized in Reference Example-2 was dissolved in dichloromethane (222 mL). The solution was cooled to −78 ° C., boron tribromide-dichloromethane solution (1.1 M, 20.5 mL, 22.6 mmol) was added dropwise, and the mixture was stirred at the same temperature for 2 hours and further at room temperature for 24 hours. After completion of the reaction, ethyl acetate and water were added to the reaction solution, the aqueous layer was separated, and the organic layer was dried over magnesium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain 3,6-dihydroxy-N- (2,2,2-trifluoroethyl) carbazole as a white solid (3.09 g, yield 100%). .
¹ H-NMR (400 MHz, heavy acetone): δ 5.09 (q, J = 9.2 Hz, 2H), δ 7.02 (dd, J = 8.7, 2.4 Hz, 2H), δ 7.43 (d , J = 8.7 Hz, 2H), δ 7.45 (d, J = 2.4 Hz, 2H), δ 8.01 (s, 2H).
¹⁹ F-NMR (376 MHz, heavy acetone): δ-71.1 (t, J = 9.2 Hz, 3F).

Reference example-4

Under an argon atmosphere, 3,6-di-tert-butylcarbazole (2.96 g, 10.6 mmol) was dissolved in THF (45 mL), and this was dissolved in an n-butyllithium / hexane solution (1.64 M, 6 at room temperature). .45 mL, 10.6 mmol) was slowly added dropwise. After stirring at room temperature for 30 minutes, the mixture was cooled to −78 ° C., octafluorotoluene (3.00 g, 12.7 mmol) was added, and the mixture was stirred at the same temperature for 1 hour and further at room temperature for 16 hours. After completion of the reaction, diethyl ether and water were added to the reaction solution, the aqueous layer was separated, and the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography (eluent: hexane) and recrystallization (95% ethanol), and 3,6-di-tert-butyl-N- [2,3,5,6-tetrafluoro- 4- (Trifluoromethyl) phenyl] carbazole was obtained as a white solid (mp: 209.8-210.8 ° C.) (4.71 g, 89% yield).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 1.46 (s, 18H), δ 7.06 (d, J = 8.6 Hz, 2H), δ 7.50 (dd, J = 8.6, 1.9 Hz) , 2H), δ 8.12 (d, J = 1.9 Hz, 2H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-140.5 (d, J = 10.6 Hz, 2F), δ-139.6 (qd, J = 21.7, 10.6 Hz, 2F), δ -56.5 (t, J = 21.7 Hz, 3F).
MS (EI, 0.92 V): m / z (%) = 495 (M ⁺ , 38), 481 (34), 480 (100), 57 (88), 41 (32).
E1 _{/ 2} : 1.57 V (vs. Ag _/ AgCl).
D: 2.9 × 10 ⁻⁶ cm ² / s.

Test Example-1
Under an argon atmosphere, lithium hexafluorophosphate (1.52 g, 10.0 mmol) and 3,6-bis (2,2,2-trifluoroethoxy) -N- (2, synthesized in Example-1) 2,2-trifluoroethyl) carbazole (445 mg, 1.00 mmol) was weighed and made up to 10 mL using an ethylene carbonate / ethyl methyl carbonate mixed solvent (volume ratio: 30/70) to obtain an electrolytic solution. .

  The lithium ion battery has a positive electrode 1 (active material: lithium cobaltate, single-layer sheet press product, manufactured by Piotrek) and negative electrode 4 (active material: natural spherical graphite) with a separator 6 (inorganic filler-containing polyolefin, manufactured by Nippon Sheet Glass) interposed therebetween. , Single layer sheet press product, manufactured by Piotrec Co., Ltd.), a stainless steel leaf spring 5 is installed on the negative electrode stainless steel cap 3, and a laminate composed of the negative electrode 4, the separator 6 and the positive electrode 1 is stored in a coin-type cell. did. After injecting an electrolytic solution containing the above 3,6-bis (2,2,2-trifluoroethoxy) -N- (2,2,2-trifluoroethyl) carbazole into this laminate, a gasket 7 is arranged. Thereafter, a positive electrode stainless steel cap 2 was put on and a coin-type cell case was caulked to obtain a battery element (FIG. 1).

  The battery element was charged with a multi-channel potentiostat / galvanostat (VMP-3) at a constant temperature of 25 ° C. with a charging current of 0.1 C and an upper limit voltage of 4.2 V, and then 0.1 C The battery was discharged until the discharge current reached 3.0V. After this operation is performed three times, constant current charging is performed at a charging current of 0.2 C under a constant temperature condition of 25 ° C., and charging is performed until the battery capacity reaches a prescribed double (6 mAh) with 4.95 V as the upper limit voltage. Went. The voltage at this time was 4.3 V (FIG. 2).

Comparative Example-1
3,6-di-tert-synthesized in Reference Example 4 instead of 3,6-bis (2,2,2-trifluoroethoxy) -N- (2,2,2-trifluoroethyl) carbazole Test was performed in the same manner as in Test Example 1 except that butyl-N- [2,3,5,6-tetrafluoro-4- (trifluoromethyl) phenyl] carbazole (149 mg, 0.30 mmol) was used. The voltage when the prepared lithium ion battery was charged to 6 mAh was 4.7 V (FIG. 2).

Comparative Example-2
The test was performed in the same manner as in Test Example 1 except that the carbazole compound was not added. When the prepared lithium ion battery was charged to 5.2 mAh, the upper limit voltage (4.95 V) was reached, and further charging could not be performed (FIG. 2).

  By adding the carbazole compound of the present invention, the voltage increase accompanying charging is suppressed as compared with Comparative Examples 1 and 2, and it can be seen that the carbazole compound of the present invention functions as an overcharge inhibitor.

It is the schematic of the lithium ion battery created by the test example and the comparative example. It is a figure which shows the charge curve of a test example and a comparative example.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode stainless cap 3 Negative electrode stainless steel cap 4 Negative electrode 5 Stainless steel leaf spring 6 Inorganic filler impregnation polyolefin porous separator 7 Gasket

  According to the present invention, since the voltage rise of the lithium ion battery can be suppressed even during overcharge, a lithium ion battery excellent in safety can be provided. Further, the present invention can be used not only for lithium ion batteries but also for sodium ion batteries, lithium sulfur batteries, calcium negative electrodes, metal negative electrodes such as aluminum, and the like.

Claims (7)

General formula (1)

(Wherein R ¹ and R ² each independently represents a fluoroalkyl group having 1 to 6 carbon atoms). The carbazole compound according to claim ^1, wherein R ¹ and R ² are each independently a fluoroalkyl group having 1 to 4 carbon atoms. The carbazole compound according to claim 1 or 2, wherein R ¹ and R ² are 2,2,2-trifluoroethyl groups. General formula (2)

(Wherein R ¹ represents a fluoroalkyl group having 1 to 6 carbon atoms) and a general formula R ² OSO ₂ CF ₃ (wherein R ² represents 1 carbon atom) And a trifluoromethanesulfonic acid ester represented by the general formula (1), wherein the trifluoromethanesulfonic acid ester represented by (6) is reacted in the presence of a base.

(Wherein, R ¹ and R ² each independently represents. A fluoroalkyl group having 1 to 6 carbon atoms) The method of producing a carbazole compound represented by the.

(Wherein, R ¹ and R ² each independently represents. A fluoroalkyl group having 1 to 6 carbon atoms) an electrolyte for a lithium ion battery comprising a carbazole compound represented by.   The electrolyte solution for a lithium ion battery according to claim 5, wherein the content of the carbazole compound is 0.01 wt% or more and 20 wt% or less.   The lithium ion battery which uses the electrolyte solution for lithium ion batteries of Claim 5 or 6.

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