JP3874435B2 - Organosulfonylimide lithium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel compound: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ). This compound is useful as an electrolyte of a non-aqueous electrolyte solution or a salt of a polymer solid electrolyte, and particularly as an electrolyte of a non-aqueous electrolyte solution of a lithium ion secondary battery.
[0002]
[Prior art]
Conventionally, inorganic electrolytes such as lithium tetrafluoroborate and lithium hexafluorophosphate have been used as electrolytes for non-aqueous electrolytes, but these inorganic electrolytes are easily decomposed by water, so several ppm in the electrolyte solvent. It gradually reacts and decomposes with a certain amount of water, and the electrolyte concentration in the electrolytic solution decreases. As a result, for example, capacity reduction occurs in the secondary battery.
As a solution to the drawbacks of the inorganic electrolyte, Japanese Patent Application Laid-Open No. 4-56069 discloses an organic sulfonic acid lithium salt typified by lithium trifluoromethanesulfonate. Since these organic sulfonic acid lithium salts are less likely to react with water than inorganic electrolytes, the decrease in electrolyte concentration in the electrolytic solution is improved. However, the organic sulfonic acid lithium salt has a lower degree of dissociation in the solution than lithium tetrafluoroborate and lithium hexafluorophosphate, and an electrolytic solution having a high conductivity cannot be obtained.
[0003]
As electrolytes having hydrolysis resistance equivalent to that of organic sulfonic acid lithium salts and having a higher degree of dissociation than organic sulfonic acid lithium salts and having high conductivity, Japanese Patent Application Laid-Open No. 5-326018 and Japanese Patent Application Laid-Open 6-176769 and functional materials, 15 (5) P.C. 50-8 (1995) discloses bis (trifluorosulfonyl) imidolithium. However, since aluminum is corroded by anodic oxidation in a solution of bis (trifluorosulfonyl) imide lithium, a lithium ion secondary battery using the solution as an electrolyte has a drawback that aluminum cannot be used as a positive electrode current collector. there were.
Japanese Patent Publication No. 3-501860 discloses a method for producing a compound: ((RSO ₂ ) ₂ N) _y M (where R represents a monovalent organic group and M represents a y-valent metal element). However, only perfluoroalkyl compounds are described in the examples.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a compound having excellent hydrolysis resistance and a high conductivity, and that the solution does not corrode aluminum, and a non-aqueous electrolyte containing the compound as an electrolyte is provided. Is to provide. Furthermore, it is providing the battery which consists of an electrode which used this electrolyte solution and aluminum as a collector.
[0005]
[Means for Solving the Problems]
The present inventors have conducted extensive study results, the formula: found that (XCHFCF ₂ SO ₂₎ organic sulfonyl imide represented by ₂ NLi (where X is F or CF ₃₎ is a compound to solve the above problems The present invention has been reached.
That is, the present invention is as follows.
1. An organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ).
2. A nonaqueous electrolytic solution containing an organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ).
3. A battery comprising a nonaqueous electrolytic solution containing an organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ) and an electrode using aluminum as a current collector.
[0006]
The present invention will be described in detail below.
The compound of the present invention: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ), the organic sulfonylimide lithium is a novel compound.
The synthesis method is not particularly limited, and examples thereof include the following multistage reaction method.
(1) by addition reaction between perfluoro olefin represented by sodium bisulfite and X-CF = CF _2, wherein: XCHFCF ₂ SO ₃ Synthesis of an organic sodium sulfonate represented by _{Na (NaHSO 3 + X-CF} = CF ₂ → XCHFCF ₂ SO ₃ Na (where X is F or CF ₃ )),
(2): by reaction with XCHFCF ₂ SO ₃ organic sodium sulfonate represented by Na and phosphorus pentachloride, wherein: XCHFCF organic sulfonyl represented by ₂ SO ₂ Cl chloride synthesis _{(XCHFCF 2 SO 3 Na + PCl} 5 → XCHFCF ₂ SO ₂ Cl + POCl ₃ + NaCl (where X is F or CF ₃ )),
(3) Synthesis of organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi by reaction of an organic sulfonyl chloride represented by the formula: XCHFCF ₂ SO ₂ Cl and bis (trimethylsilyl) imide lithium (2XCHFCF _{2 SO 2 Cl + ((CH 3} ) 3 Si) 2 NLi → (XCHFCF 2 SO 2) 2 NLi + 2 (CH 3) 3 SiCl ( where X is F or CF ₃₎₎ and the like.
[0007]
The use of the organic sulfonylimide lithium represented by the compound of the present invention: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ), specifically, is an electrolyte of a non-aqueous electrolyte solution of a primary or secondary battery And salts of polymer solid electrolytes, catalysts for organic synthesis reactions, and the like.
The solvent of the non-aqueous electrolyte solution containing the compound of the present invention as an electrolyte is not particularly limited as long as it is an aprotic polar solvent capable of dissolving the compound. For example, carbonates, esters, lactones, ethers, nitriles Amides, sulfones and the like can be used, among which carbonates, esters, lactones and ethers are preferred. Furthermore, not only a single solvent but also a mixture of two or more solvents may be used. The electrolyte concentration of the nonaqueous electrolyte solution is preferably 0.1 mol · dm ^-3 or higher saturated concentration or less, still more preferably a saturated concentration or less 0.5 mol · dm ^-3 or more. When the concentration is less than 0.1 mol · dm ⁻³ , the conductivity of the electrolytic solution is low, which is not preferable.
[0008]
As a battery composed of an electrode using the non-aqueous electrolyte and aluminum as a current collector, for example, a copper foil as a current collector, a carbon-based negative electrode capable of occluding lithium ions, and an aluminum foil are collected. Examples thereof include a lithium ion secondary battery including a positive electrode mainly composed of a lithium-containing transition metal chalcogen compound.
The solid polymer electrolyte using the compound of the present invention as a salt is, for example, a polymer mainly composed of polyethylene glycol (PEG) segments so that the concentration thereof is 0.1 mol · dm ⁻³ or more and 5 mol · dm ⁻³ or less. The concentration of the lithium salt of the present invention is a saturated concentration of 0.1 mol · dm ⁻³ or more of a polymer obtained by directly dissolving a lithium salt, or a polymer mainly composed of PEG segments, polyacrylonitrile (PAN) or polyvinylidene fluoride (PVdF). Examples thereof include those swollen with 10 to 200 parts by weight of the following non-aqueous solvent solution.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to examples.
[0010]
[Example 1]
Synthesis of bis (1,1,2,2-tetrafluoroethanesulfonyl) imidolithium.
(1) Addition reaction of sodium bisulfite and tetrafluoroethylene In a 1000 ml pressure vessel, 80 g of sodium bisulfite (NaHSO ₃ ), 36.7 g of sodium tetraborate decahydrate (Na ₂ B ₄ O ₇ .10H ₂ O), 160 ml of pure water and 100 g of tetrafluoroethylene were added and reacted at 120 ° C. for 110 hours. The reaction solution was filtered, and the filtrate was dehydrated and dried under reduced pressure, and then 300 ml of ethanol was added and refluxed for 3 hours. The formed insoluble solid was filtered off, and the solvent was removed from the filtrate to remove 31.4 g of 1,1,2,2 - give sodium tetrafluoroethane sulfonate _{(HCF 2 CF 2 SO 3 Na} ). Yield 20.1%.
(2) Reaction of sodium 1,1,2,2-tetrafluoroethanesulfonate with phosphorus pentachloride Place 49.2 g of phosphorus pentachloride and 100 g of phosphorus oxychloride in a 300 ml four-necked flask while stirring. 30.0 g of sodium 1,1,2,2-tetrafluoroethanesulfonate synthesized in (1) above was dropped from the dropping funnel, and then heated to maintain the reflux state for 23 hours. Subsequently, atmospheric distillation is performed to separate a fraction at 105 to 110 ° C., and the lower layer is separated by dropping into ice water, washed with 500 ml of water for 1 hour, dehydrated with anhydrous sodium sulfate, and 10.2 g of colorless and transparent. Of 1,1,2,2-tetrafluoroethanesulfonic acid chloride (HCF ₂ CF ₂ SO ₂ Cl) was obtained. Yield 69.0%.
[0011]
(3) Synthesis of bis (1,1,2,2-tetrafluoroethanesulfonyl) imidolithium.
40.0 ml of a 1.0 mol · dm ⁻³ THF solution of bis (tetramethylsilyl) imidolithium ((CH ₃ ) ₃ Si) ₂ NLi was placed in a 300 ml four-necked flask and maintained at 0 ° C. synthesized 1,1,2,2-tetrafluoroethane sulfonic acid chloride in 2) (HCF ₂ CF ₂ SO ₂ Cl) was 8.0g dropwise. The mixture was stirred at room temperature for 10 days, and then the reaction solution obtained by filtering insolubles was evaporated to dryness at 60 ° C. and 15 mmHg to obtain 3.6 g of bis (1,1,2,2-tetrafluoroethanesulfonyl). Imidolithium ((HCF ₂ CF ₂ SO ₂ ) ₂ NLi) was obtained. Yield 59.3%.
Infrared absorption spectrum: 3005 cm ⁻¹ (C—H); 1640 cm ⁻¹ (S═O); 1140 cm ⁻¹ (C—F)
¹⁹ F-NMR spectrum (CFCl ₃ standard): -136 ppm (2F); -139 ppm (2F)
Melting point: 480 ° C. (measured with DSC (Seiko Electronics Co., Ltd .: S-5000), heating rate 15 ° C./min).
Elemental analysis (calculated values in parentheses): Li = 1.9 (2.0)%, C = 13.2 (13.7)%, H = 0.7 (0.6)%, O = 18.4 (18.2)%, N = 4.4 (4.0)%, F = 41.0 (43.2)%, S = 18.5 (18.3)%
[0012]
[Example 2]
Synthesis of bis (1,1,2,3,3,3-hexafluoro-n-propanesulfonyl) imidolithium.
(1) Addition reaction of sodium bisulfite and hexafluoropropylene In a 1000 ml pressure vessel, 80 g of sodium bisulfite (NaHSO ₃ ), 36.7 g of sodium tetraborate decahydrate (Na ₂ B ₄ O ₇ .10H ₂ O), 160 ml of pure water and 120 g of hexafluoropropylene were added and reacted at 120 ° C. for 110 hours. The reaction solution was filtered, and the filtrate was dehydrated and dried under reduced pressure, and then 300 ml of ethanol was added and refluxed for 3 hours. The formed insoluble solid was filtered off, and the solvent was removed from the filtrate to remove 35.2 g of 1,1,2,3. , 3,3-hexafluoro-n-propanesulfonic acid sodium salt (CF ₃ CHFCF ₂ SO ₃ Na) was obtained. Yield 18.0%.
(2) Reaction of sodium 1,1,2,3,3,3-hexafluoro-n-propanesulfonate with phosphorus pentachloride 49.2 g of phosphorus pentachloride and 100 g of oxychloride in a 300 ml four-necked flask 30.0 g of sodium 1,1,2,3,3,3-hexafluoro-n-propanesulfonic acid synthesized in the above (1) was added dropwise from a dropping funnel while stirring, and then heated to 23 The reflux state was maintained for a time. Subsequently, atmospheric distillation was performed to separate a fraction at 105 to 110 ° C., and this was dropped into ice water to separate the lower layer, washed with 500 ml of water for 1 hour, dehydrated with anhydrous sodium sulfate and 21.2 g of colorless and transparent. Of 1,1,2,3,3,3-hexafluoro-n-propanesulfonic acid chloride (CF ₃ CHFCF ₂ SO ₂ Cl) was obtained. Yield 71.5%.
[0013]
(3) Synthesis of bis (1,1,2,3,3,3-hexafluoro-n-propanesulfonyl) imide lithium.
In a 300 ml four-necked flask, 40.0 ml of a 1.0 mol / dm ³ THF solution of bis (tetramethylsilyl) imidolithium ((CH ₃ ) ₃ Si) ₂ NLi was placed and maintained at 0 ° C. (2 20.1 g of 1,1,2,3,3,3-hexafluoro-n-propanesulfonic acid chloride (CF ₃ CHFCF ₂ SO ₂ Cl) synthesized in (1) was added dropwise. The mixture was stirred at room temperature for 10 days, and then the reaction solution from which insolubles had been filtered off was evaporated to dryness at 60 ° C. and 15 mmHg, and then 10.3 g of bis (1,1,2,3,3,3-hexa). Fluoro-n-propanesulfonyl) imidolithium ((CF ₃ CHFCF ₂ SO ₂ ) ₂ NLi) was obtained. Yield 57.3%.
Infrared absorption ^{spectrum: 3005cm -1 (C-H)} ; 1640cm -1 (S = O); 1240cm -1 (C-F)
¹⁹ F-NMR spectrum (CFCl ₃ standard): −78 ppm (3F: t, J = 7 Hz); −109 ppm (1F: md, J = 220 Hz), −116 ppm (1F: md, J = 230 Hz); 1F: m)
Melting point: 502 ° C. (measured with DSC (Seiko Electronics Co., Ltd .: S-5000), heating rate 15 ° C./min).
Elemental analysis (calculated values in parentheses): Li = 1.7 (1.5)%, C = 17.2 (16.0)%, H = 0.7 (0.4)%, O = 15.0 (14.2)%, F = 49.0 (50.6)%, S = 14.5 (14.2)%
[0014]
[Example 3]
Measurement of aluminum anodic oxidation current 1: propylene carbonate / dimethoxyethane (1: 1) of bis (1,1,2,2-tetrafluoroethanesulfonyl) imide lithium synthesized in Example 1 at a concentration of 0.7 mol / dm ^-3 (Volume ratio) When the solution was an electrolyte, the working electrode was aluminum (commercially available aluminum foil), the counter electrode and the reference electrode were lithium metal, and the aluminum was held at a potential of 4.0 V (vs. Li metal), A current of 5 μA · cm ⁻² flowed between the electrodes.
[0015]
[Example 4]
Measurement of aluminum anodic oxidation current 2: propylene carbonate having a concentration of 0.7 mol · dm ⁻³ of bis (1,1,2,3,3,3-hexafluoro-n-propanesulfonyl) imide lithium synthesized in Example 2 / Dimethoxyethane (1/1 volume ratio) solution is used as electrolyte, aluminum is 4.0V (vs. Li metal) in a cell in which the working electrode is aluminum (commercially available aluminum foil) and the counter electrode and reference electrode are lithium metal. When this potential was maintained, a current of 3 μA · cm ⁻² flowed between the electrodes.
[0016]
[Example 5]
Measurement of conductivity of solution 1: propylene carbonate / dimethoxyethane (1/1) having a concentration of 0.7 mol · dm ⁻³ of bis (1,1,2,2-tetrafluoroethanesulfonyl) imide lithium synthesized in Example 1 Volume ratio) The conductivity of the solution was measured with a conductivity meter (Toa Radio Co., Ltd .: CM-60S) and a conductivity cell (Toa Radio Co., Ltd .: CG-511B), and 2.97 mScm ⁻¹ at 23 ° C. Was obtained.
[0017]
[Example 6]
Measurement of conductivity of solution 2: propylene carbonate having a concentration of 0.7 mol · dm ⁻³ of bis (1,1,2,3,3,3-hexafluoro-n-propanesulfonyl) imide lithium synthesized in Example 1 / Dimethoxyethane (1/1 volume ratio) conductivity of the solution was measured with a conductivity meter (Toa Radio Co., Ltd .: CM-60S) and a conductivity cell (Toa Radio Co., Ltd .: CG-511B), 23 A value of 3.01 mScm ⁻¹ was obtained at 0 ° C.
[0018]
[Comparative Example 1]
A propylene carbonate / dimethoxyethane (1/1 volume ratio) solution of bis (trifluoromethanesulfonyl) imidolithium having a concentration of 0.7 mol · dm ⁻³ is used as an electrolyte, the working electrode is aluminum (commercially available aluminum foil), a counter electrode, When aluminum was held at a potential of 4.0 V (vs. Li metal) in a cell in which the reference electrode was lithium metal, a current of 210 mA · cm ⁻² flowed between the electrodes. The current values in the electrolytic solutions of Example 3 and Example 4 are 1 / 10,000 or less of the values in the electrolytic solution of Comparative Example 1, and the corrosion rates of aluminum in the electrolytic solutions of Examples 3 and 4 are compared. It shows that it becomes 1 / 10,000 or less in the electrolyte solution of Example 1.
[0019]
[Comparative Example 2]
Measurements of conductivity of the solution: propylene carbonate / dimethoxyethane (1/1 volume ratio) of perfluorobutane sulfonic acid lithium concentration 0.7 mol · dm ^-3 conductivity a conductivity meter of solution (Toa Telecommunications Co. : CM-60S) and a conductivity cell (Toa Radio Co., Ltd .: CG-511B), a value of 2.10 mScm ^-1 was obtained at 23 ° C.
[0020]
[Example 7]
The cylindrical nonaqueous electrolyte battery shown in FIG. 3 was produced as follows.
First, LiCoO ₂ was pulverized to an average particle size of 3 μm by a ball mill, and 0.025 part by weight of graphite, 0.025 part by weight of acetylene black and 0.02 part by weight of polyvinylidene fluoride as a binder were added to 1 part by weight of this powder. In addition, a paste formed using dimethylformamide was applied to one surface of an aluminum foil having a thickness of 15 μm so as to have a dry film thickness of 100 μm, thereby producing a positive electrode 1. On the other hand, commercially available petroleum-based needle coke (manufactured by Koa Oil Co., Ltd., KOA-SJ Coke) was pulverized with a ball mill to an average particle size of 10 μm. The surface distances d ₀₀₂ and Lc ₍₀₀₂₎ obtained from the BET surface area, true density, and X-ray diffraction of this needle coke were 11 m ² · g ⁻¹ , 2.13 g · cm ⁻³ , 3.44 mm and 52 mm, respectively. It was. Add 0.05 parts by weight of polyvinylidene fluoride as a binder to 1 part by weight of this powder, paste it into a paste using dimethylformamide, and apply it on one side of a 10 μm thick copper foil to a dry film thickness of 130 μm. Thus, negative electrode 2 was produced. The positive electrode 1 and the negative electrode 2 were welded with an aluminum positive electrode lead terminal 3 and a copper negative electrode lead terminal 4 for current collection, respectively. Then, a separator 5 made of a polyethylene microporous film was interposed between the positive electrode 1 and the negative electrode 2 and laminated together and wound many times to produce a spiral electrode body. The spiral electrode body was housed in a SUS battery container 6. The negative electrode lead terminal 4 was connected to the inner bottom portion of the battery container 6 by spot welding, and the positive electrode lead terminal 3 was connected to the battery sealing plate 7 in the same manner.
[0021]
Next, the compound bis (1,1,2,2) of Example 1 was used as an electrolyte in a mixed solvent in which propylene carbonate and diethoxymethane were mixed at a volume ratio of 1: 1 in a battery can container 6 containing the electrode body. , 2-tetrafluoroethanesulfonyl) imidolithium dissolved in 0.7 mol · dm ⁻³ , and an electrolytic solution prepared by pouring the battery container 6 and the battery sealing plate 7 into the polypropylene packing 8 The cylindrical non-aqueous electrolyte battery having an outer diameter of 20 mm and an outer diameter of 50 mm was manufactured by fitting and crimping. When this battery was subjected to a charge / discharge test at room temperature (about 20 ° C.) with a charge / discharge current of 0.3 A, a charge end voltage of 4.2 V, and a discharge end voltage of 2.7 V, a discharge capacity of 0.90 Ah for the first cycle, The discharge capacity retention rate at the 100th cycle (percentage obtained by dividing the discharge capacity at the 100th cycle by the capacity at the first cycle) was 90%.
[0022]
[Example 8]
The compound non-aqueous electrolyte battery shown in FIG. 3 was mixed with propylene carbonate and diethoxymethane in a volume ratio of 1: 1, and the compound bis (1,1,2,3,3) of Example 2 as an electrolyte. , 3-hexafluoro-n-propanesulfonyl) imidolithium was prepared in the same manner as in Example 7 except that an electrolytic solution prepared by dissolving it to 0.7 mol · dm ⁻³ was poured. The battery container 6 and the battery sealing plate 7 were fitted and crimped through a polypropylene packing 8 to be sealed, thereby producing a cylindrical nonaqueous electrolyte battery having an outer diameter of 20 mm and 50 mm. When this battery was subjected to a charge / discharge test at room temperature (about 20 ° C.) with a charge / discharge current of 0.3 A, a charge end voltage of 4.2 V, and a discharge end voltage of 2.7 V, a discharge capacity of 0.90 Ah for the first cycle, As a result, a discharge capacity retention ratio of the 100th cycle (percentage obtained by dividing the discharge capacity of the 100th cycle by the capacity of the first cycle) was 93%.
[0023]
【The invention's effect】
According to the present invention, an organic sulfonylimide lithium represented by a novel compound useful as an organic electrolyte: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ) can be obtained. The compound of the present invention provides a non-aqueous electrolyte that is excellent in hydrolysis resistance as an electrolyte and hardly corrodes aluminum.
[Brief description of the drawings]
FIG. 1 is an infrared absorption spectrum of the compound of Example 1 of the present invention.
FIG. 2 is an infrared absorption spectrum of the compound of Example 2 of the present invention.
FIG. 3 is a longitudinal sectional view of a non-aqueous electrolyte battery used in Example 7 and Example 8 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Band-shaped positive electrode 2 Band-shaped negative electrode 3 Positive electrode lead terminal 4 Negative electrode lead terminal 5 Separator 6 Battery container 7 Battery sealing plate 8 Packing 9 Insulating plate

Claims (3)

An organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ). A nonaqueous electrolytic solution containing an organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ). A battery comprising a nonaqueous electrolytic solution containing an organic sulfonylimide lithium represented by the formula: (XCHFCF ₂ SO ₂ ) ₂ NLi (where X is F or CF ₃ ) and an electrode using aluminum as a current collector.

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