JP2005222846A - Electrolyte solution for secondary battery and secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain electrolyte solution which is stable even if preserved for a long period, and to provide a lithium secondary battery excellent in a capacity restoration rate with rise of resistance and a generated volume of gas restrained. <P>SOLUTION: On the electrolyte solution for the secondary battery containing a compound expressed in general formula (1) in an aprotic solvent, a content of chlorine in the electrolyte solution is made less than 150 ppm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrolyte for a secondary battery and a secondary battery using the same.

  Non-aqueous electrolyte lithium which uses carbon material, oxide, lithium alloy or lithium metal for negative electrode, uses lithium-containing transition metal composite oxide for positive electrode, and further has electrolyte containing chain or cyclic carbonate solvent Ion or lithium secondary batteries are attracting attention as power sources for mobile phones and laptop computers because they can achieve high energy density. Recently, attention has also been paid to a power source for driving a motor such as a hybrid vehicle (HEV) by improving output characteristics and long-term reliability such as storage characteristics. In these secondary batteries, for the purpose of suppressing the reaction between the electrode surface and the solvent molecules, one or more additives are added to the electrolytic solution, and the electrochemical reaction in the charge / discharge process is used to It is known to form a film called a protective film (or film) derived from an additive to improve the basic characteristics and reliability of a secondary battery. It is known that the formation and control of the coating on the electrode surface is indispensable for improving the performance of the battery because this coating has a great influence on the charge / discharge efficiency, cycle life, and safety.

In order to form the film, various additives have been applied to the electrolytic solution. Among them, cyclic monosulfonic acid esters as shown in Patent Documents 1 to 3 have excellent film forming ability and can improve battery characteristics. It is often used. In addition, recently, in non-patent document 1, secondary batteries using cyclic disulfonate (CDS) as an additive for electrolyte solution have cycle characteristics and storage characteristics (inhibition of resistance increase) rather than those using cyclic monosulfonate. It has been reported that the high capacity retention rate) can be significantly improved. Since the cyclic disulfonic acid ester is synthesized via an alkyldisulfonic acid chloride, for example, as shown in Patent Document 4, it usually contains a compound containing chlorine as an impurity.
JP 63-102173 A JP 2000-3724 A JP 11-339850 A Japanese Patent Publication No. 5-44946 Yuki Kusachi, Koji Utsugi, Abstracts of the 44th Battery Conference, pp 526-527 (2003)

  As described above, the secondary battery using the cyclic disulfonic acid ester as an additive for the electrolytic solution exhibits very excellent battery characteristics. However, it has the following problems. In Patent Document 4, recrystallization after crude synthesis and further sublimation purification are performed, but it is generally difficult to remove chlorine-based impurities. When a cyclic disulfonic acid containing a certain amount of a chlorine-based impurity was mixed with an electrolytic solution, and the electrolytic solution was stored for a long period of time, such as one month or longer, a phenomenon was observed in which it colored and deteriorated over time. It has also been found that battery characteristics deteriorate when a battery is made using a colored electrolyte containing a certain amount or more of chlorine-based impurities.

  Thus, when cyclic disulfonic acid ester is used as an additive for electrolytic solution, the content of chlorinated compounds as impurities is reduced as much as possible, and even if it contains a trace amount of chlorinated compounds, it is excellent. Development of secondary battery electrolytes that exhibit excellent battery characteristics is an important issue.

  In order to solve the above problems, the present invention is characterized by having the following configuration. That is, the present invention is an electrolytic solution for a secondary battery containing at least an aprotic solvent and a cyclic disulfonic acid ester, wherein the concentration of the cyclic disulfonic acid ester in the electrolytic solution is 0.1% by mass or more and 5.0% by mass. An electrolytic solution for a secondary battery, characterized in that the proportion of chlorine in the electrolytic solution is less than 150% by mass and is less than 150 ppm by mass.

  In the present invention, the cyclic disulfonic acid ester is preferably a substance represented by the following general formula (1).

(However, in the above general formula (1), A is a substituted or unsubstituted C1-C5 alkylene group, carbonyl group, sulfinyl group, which may be branched, or substituted or unsubstituted which may be branched. A perfluoroalkylene group having 1 to 5 carbon atoms, a substituted or unsubstituted fluoroalkylene group having 2 to 6 carbon atoms which may be branched, and a substituted or unsubstituted carbon number which may be branched including an ether bond A 1-6 alkylene group, a substituted or unsubstituted C1-C6 perfluoroalkylene group that may contain an ether bond, or an ether bond, or a C2-6 substitution that may contain a ether bond Or an unsubstituted fluoroalkylene group, and B represents a substituted or unsubstituted alkylene group which may be branched.)
In the present invention, it is further preferable that the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (2).

(However, in the said General formula (2), x is 0 or 1, n is an integer of 1-5, and R shows a hydrogen atom, a methyl group, an ethyl group, or a halogen atom.)
In the present invention, it is further preferable that the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (3).

(However, in the general formula (3), x is 0 or 1, n is an integer of 1 to 5, and R represents a hydrogen atom, a methyl group, an ethyl group, or a halogen atom.)
In the present invention, it is further preferable that the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (4).

(However, in the above general formula (4), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4, and k + m + n is 3 to 6. R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.)
In the present invention, the compound represented by the general formula (1) is preferably a cyclic disulfonic acid ester represented by the following general formula (5).

(However, in the general formula (5), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4 and k + m + n is 3 to 6.) R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.)
In the present invention, it is further preferable that the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (6).

(However, in the general formula (6), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4, and k + m + n is 3 to 6.) R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.)
In the present invention, it is further preferable that the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (7).

(However, in the general formula (6), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4, and k + m + n is 3 to 6.) R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.)
According to the present invention, there is provided an electrolytic solution for a secondary battery, wherein the aprotic solvent contains the compound represented by the general formula (1), wherein the chlorine content in the electrolytic solution Is 150 ppm or less, an electrolytic solution effective for storage stability can be provided.

According to the present invention, by using an electrolyte solution for a secondary battery in which a cyclic disulfonic acid ester compound of the general formula (1) is contained in an aprotic solvent containing less than 150 pp of chlorine on a mass basis, Such long-term storage is possible. As a result, a lithium secondary battery excellent in storage stability (suppression of resistance increase, suppression of gas generation, high capacity recovery rate) can be obtained.

  The electrolytic solution for a secondary battery of the present invention has a cyclic disulfonic acid ester represented by the following general formula (1). By having this cyclic disulfonic acid ester, a secondary battery excellent in long-term storage stability can be obtained even if it contains less than 150 pp of chlorine.

(However, in the above general formula (1), A is a substituted or unsubstituted C1-C5 alkylene group, carbonyl group, sulfinyl group, which may be branched, or substituted or unsubstituted which may be branched. A perfluoroalkylene group having 1 to 5 carbon atoms, a substituted or unsubstituted fluoroalkylene group having 2 to 6 carbon atoms which may be branched, and a substituted or unsubstituted carbon number which may be branched including an ether bond A 1-6 alkylene group, a substituted or unsubstituted C1-C6 perfluoroalkylene group that may contain an ether bond, or an ether bond, or a C2-6 substitution that may contain a ether bond Or an unsubstituted fluoroalkylene group, and B represents a substituted or unsubstituted alkylene group which may be branched.)
Here, “C2-C6 substituted or unsubstituted fluoroalkylene group which may be branched” and “C2-C6 substituted or unsubstituted fluoroalkylene which may be branched including an ether bond” The fluoroalkylene group in the “group” is a group in which a part of hydrogen atoms bonded to a carbon atom is substituted with a fluorine atom, and at least two hydrogen atoms bonded to the same carbon and two bonded to the same carbon. It preferably has two fluorine atoms.
The perfluoroalkylene group refers to an alkylene group in which all hydrogen atoms of the alkylene group are replaced with fluorine atoms.

  Specific examples of the cyclic disulfonic acid ester of the general formula (1) of the present invention are specifically illustrated below, but the present invention is not limited thereto.

The compound represented by the general formula (1) can be produced by referring to a method for synthesizing a cyclic disulfonic acid ester described in Patent Document 4 and using methanedisulfonic acid chloride as an intermediate.
Further, examples of the chlorine-based impurities present in the electrolytic solution include the following compounds.

In the present invention, the aprotic solvent contains at least the compound represented by the general formula (1), and the chlorine content in the electrolytic solution needs to be less than 150 ppm on a mass basis. In the case of 150 ppm or more, the electrolyte solution is colored when the electrolyte solution is allowed to stand for approximately one month or longer. The details of this coloring are not well understood at present, but it is conceivable to decompose the solvent or indicator salt contained in the electrolyte solution via chlorinated impurities, or decompose the additive via it. When a secondary battery is produced using this colored electrolyte, the cycle characteristics and the storage characteristics are deteriorated as compared with an electrolyte that is not colored. When the chlorine content was less than 150 ppm, no coloring phenomenon was observed even when left for more than one month, and the battery characteristics were not significantly deteriorated.
If the chlorine content is less than 150 ppm, there is no particular problem, but for the purpose of enhancing the effect of suppressing gas generation during storage of the battery at a high temperature (eg, 55 ° C.), the chlorine content is particularly preferably 100 ppm or less. good. More preferably, the chlorine content is zero. When the chlorine content is 0, the secondary battery can have better long-term storage and cycle characteristics.

  The compound represented by the general formula (1) needs to be contained in an amount of 0.1 to 5.0% by mass in the electrolytic solution. If it is less than 0.1% by mass, the film formation on the electrode surface is not sufficiently effective. If it exceeds 5.0% by mass, it will increase the viscosity of the electrolyte or increase the resistance of the electrolyte. In the present invention, more preferably, a sufficient film effect is obtained when added in the range of 0.5 to 3.0% by mass.

  In addition to the compound represented by the above general formula (1), it may further comprise a compound having one or more sulfonyl groups other than those represented by the general formula (1). Preferably, a cyclic sulfonic acid ester compound represented by the following general formula (8) can be included.

(However, in the general formula (8), n is 0 to 2 integer. Further, R ₁ to R ₆ are each independently hydrogen atom, C 1 to 12 alkyl group carbon, 3 carbon atoms Or a cycloalkyl group having 6 or less or an aryl group having 6 to 12 carbon atoms.)
By adding a compound having a sulfonyl group represented by the general formula (8) in addition to the compound represented by the general formula (1), the stability of the film is improved by the combined effect, the solvent molecule decomposition inhibiting effect, and the water removing effect are greatly increased. Become. Specific compounds represented by the general formula (8) include 1,3-propane sultone and 1,4-butane sultone (Japanese Patent Laid-Open Nos. 62-1000094, 63-102173, 11-339850). However, it is not limited to these.

  Furthermore, according to the present invention, the cycle characteristics can be further improved by adding or mixing vinylene carbonate or a derivative thereof into the electrolytic solution. When the vinylene carbonate or a derivative thereof is used as an additive, the effect can be obtained by adding 0.01 to 10% by mass in the electrolytic solution. Moreover, when using as a solvent, an effect is acquired by including 1-5 mass%.

  Examples of the organic solvent for the aprotic electrolyte solution include cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, γ-lactones, cyclic ethers, chain ethers, and fluorinated derivatives thereof. It is preferable to contain at least one organic solvent selected from the group. By containing these organic solvents, a secondary battery having more excellent battery characteristics can be obtained.

Further, the electrolyte solution preferably contains a lithium salt. Lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , LiAlCl ₄ , LiN (C _k F _{2k + 1} SO ₂ ) ₂ , LiN (C _k F _{2k + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ ) (k and m are each independently 1 or 2), and LiPF ₆ and LiBF ₄ are particularly preferable. By including these lithium salts, a high energy density can be achieved.

  Moreover, according to this invention, the secondary battery using the said electrolyte solution for secondary batteries provided with the positive electrode and negative electrode which use lithium as an active material is provided. FIG. 1 shows a schematic structure of an example of a battery according to the present invention. A positive electrode current collector 11, a layer 12 containing a positive electrode active material made of an oxide or a sulfur compound, a conductive polymer, a stabilized radical compound or a mixture capable of inserting and extracting lithium ions; and a lithium ion A layer 13 containing a negative electrode active material made of any one of a carbon material or an oxide to be occluded and released, a metal that forms an alloy with lithium, lithium metal itself, or a mixture thereof, a negative electrode current collector 14, and an electrolytic solution 15 , And a porous separator 16 including the same. Here, the vinyl disulfone compound represented by the general formula (1) is contained in the electrolytic solution 15 containing a lithium salt as an electrolyte.

  The negative electrode uses a negative electrode active material made of a material capable of inserting and extracting lithium, lithium metal, a metal material capable of forming an alloy with lithium, and an oxide material. Carbon is contained as a material capable of inserting and extracting lithium, and graphite or amorphous carbon is particularly preferable.

  The negative electrode of the secondary battery according to the present invention is made of a material that can occlude and release lithium, such as lithium metal, a lithium alloy, or a carbon material or an oxide. As the carbon material, graphite that occludes lithium, amorphous carbon, diamond-like carbon, carbon nanotube, carbon nanohorn, or a composite thereof can be used.

  Further, as the oxide material, any of silicon oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, phosphoric acid, boric acid, or a composite thereof may be used, and it is particularly preferable that silicon oxide is included. . The structure is preferably in an amorphous state. This is because silicon oxide is stable and does not cause a reaction with other compounds, and the amorphous structure does not lead to deterioration due to nonuniformity such as crystal grain boundaries and defects. As a method for forming the layer having the negative electrode active material, a method such as an evaporation method, a CVD method, or a sputtering method can be used.

  The lithium alloy is composed of lithium and a metal capable of forming an alloy with lithium. For example, it is composed of a binary or ternary or higher alloy of a metal such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, and lithium. As the lithium metal or lithium alloy, an amorphous alloy is particularly preferable. This is because the amorphous structure hardly causes deterioration due to non-uniformity such as crystal grain boundaries and defects.

  Lithium metal or lithium alloy is formed by an appropriate method such as a melt cooling method, a liquid quenching method, an atomizing method, a vacuum deposition method, a sputtering method, a plasma CVD method, a photo CVD method, a thermal CVD method, a sol-gel method, etc. Can do. By using these materials as the negative electrode active material, a secondary battery having a high energy density can be obtained.

In the present invention, as the positive electrode active material, a composite oxide that is Li _b ZO ₂ (wherein Z represents at least one transition metal), for example, Li _b CoO ₂ , Li _b NiO ₂ , Li _b Mn ₂ O ₄ , Li _b MnO ₃ , Li _b Ni _d Cr _1-d O ₂ (where 0 <b <1, 0 <d <1), or organic sulfur compound, conductive polymer, organic A radical compound or the like can be used. Alternatively, a lithium-containing composite oxide having a plateau at 4.5 V or more at the metal lithium counter electrode potential can be used. Examples of the lithium-containing composite oxide include spinel-type lithium manganese composite oxide, olivine-type lithium-containing composite oxide, and reverse spinel-type lithium-containing composite oxide. The lithium-containing composite oxide is, for example, a general formula Li _a (A _x Mn _2−x ) O ₄ (where 0 <x <2, 0 <a <1.2. A is Ni, Co, Fe , At least one selected from the group consisting of Ti, Cr and Cu.). By using these materials as the positive electrode active material, a secondary battery having a high energy density can be obtained.

  In the positive electrode according to the present invention, these active materials are dispersed and kneaded in a solvent such as N-methyl-2-pyrrolidone (NMP) together with a conductive material such as carbon black and a binder such as polyvinylidene fluoride (PVDF). It can be obtained by a method such as coating on a substrate such as an aluminum foil.

  The electrolytic solution of the present invention is brought about by adding and dissolving the compound represented by the general formula (1) in the electrolytic solution in advance. An electrolytic solution containing a monosulfonic acid ester or a vinylene carbonate compound can be obtained by further adding a compound represented by the general formula (8) or a vinylene carbonate compound to the electrolytic solution.

  In the present invention, a negative electrode using lithium as an active material and a positive electrode are combined with a separator interposed therebetween, inserted into a battery outer package, impregnated with an electrolytic solution containing a compound represented by the general formula (1), and then the battery. A film can be formed on the electrode by charging the battery after sealing or sealing the outer package.

Examples of the electrolytic solution in the present invention include propylene carbonate (hereinafter referred to as PC), ethylene carbonate (hereinafter referred to as EC), butylene carbonate (BC), cyclic carbonates such as vinylene carbonate (VC), dimethyl Chain carbonates such as carbonate (DMC), diethyl carbonate (hereinafter referred to as DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), aliphatic such as methyl formate, methyl acetate, ethyl propionate Carboxylic acid esters, γ-lactones such as γ-butyrolactone, chain ethers such as 1,2-ethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, Dimethylsulfoxy 1,3-dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphate triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl Aprotic organics such as 2-imidazolidinone, 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, fluorinated carboxylic acid esters One or a mixture of two or more solvents are used to dissolve lithium salts that are dissolved in these organic solvents. The lithium salt, lithium imide _{salt, LiPF 6, LiAsF 6, LiAlCl} 4, LiClO 4, LiBF 4, LiSbF 6 , and the like.

  When dissolving the compound represented by the general formula (1) and further dissolving the cyclic monosulfonic acid ester of the general formula (8), the concentration of the compound represented by the general formula (8) contained in the electrolytic solution is particularly Although not limited, Preferably 0.01-10 mass% is preferable with respect to the whole electrolysis liquid. When the amount is less than 0.01% by mass, the effect of the additive does not spread over the entire electrode surface, and when the amount exceeds 10% by mass, the viscosity of the electrolyte increases and the liquid resistance increases.

The lithium secondary battery according to the present invention includes a negative electrode and a positive electrode laminated in a dry air or inert gas atmosphere via a separator, or after being rolled up, the lithium secondary battery is accommodated in a battery can or a synthetic resin and a metal A battery can be manufactured by sealing with a flexible film made of a laminate with a foil. In addition, as a separator, porous films, such as polyolefin, such as a polypropylene and polyethylene, a fluororesin, are used.
The shape of the secondary battery according to the present invention is not particularly limited, and examples thereof include a cylindrical shape, a square shape, a coin shape, and a laminate shape.

(Execution synthesis example 1)
(Synthesis of methylenemethane disulfonate (MMDS) shown in Compound No. 1)
(1) Synthesis of methylene-di-sulfochloride (MDSC) 339.32 g (2.213 mol) of phosphorus oxychloride is charged, and 257.88 g (2.213 mol) of chlorosulfonic acid (CS) is charged under ice cooling. Next, 66.45 g (1.107 mol) of acetic acid is added dropwise at 40 ° C. or lower, and then the temperature is slowly raised to reflux (110 ° C.). After incubating for 1 hour under reflux, it was distilled to obtain 159.10 g (0.47 mol) of MDSC. It was confirmed to be MDSC by NMR findings (5.6 ppm (2H)).

(2) Synthesis of silver salt of methylene-di-sulfonic acid (SMDS) 201.73 g (0.728 mol) of silver carbonate and 706 ml of acetonitrile (distilled product added with niline pentoxide) are charged. A solution of MDSC 73.48 g (0.345 mol) in 463 ml of acetonitrile (distilled product added with niline pentoxide) was added dropwise at 40 ° C. or lower.

After stirring at room temperature for 24 hours, filtration and washing with acetonitrile (weight after drying of filtration residue = 134.54 g), 955.90 g of an SMDS acetonitrile solution was obtained. (SMDS includes 119.07g, 0.305mol)
(3) Compound No. Synthesis of 1 (3) -Method A 195.90 g of SMDS in acetonitrile (119.07 g, 0.305 mol as SMDS) was charged with 195.60 g (0.727 mol) of diiodomethane and stirred under reflux for 24 hours. Filtration, washing with acetonitrile (weight after drying of residue = 116.54 g) and concentration gave 76.34 g of a yellow pasty residue. MMDS was eluted with 3 x 100 ml of methylene chloride. The eluted methylene chloride solution was decolorized and filtered with 1 g of activated carbon, concentrated to about 5 ml, and the precipitated crystals were filtered and dried to obtain 4.62 g of white needle crystals. 4.62 g of the white needle crystals are sublimated in a 90 ° C. oil bath under a reduced pressure of 0.5 Torr for 1 hour. The sublimate (a trace amount) at this time is discarded. Again, sublimation under reduced pressure of 0.5 Torr in an oil bath at 200 ° C. and 4.25 g of compound NO. 1 was obtained (the amount of unsublimated was traced at 200 ° C. for 1 hour). Furthermore, Compound No. No. 1 was purified twice by silica gel column chromatography (SiO2: 20 g, hexane: ethyl acetate = 1: 1), and compound No. 1 was obtained. 1 was obtained. The resulting compound NO. When the chlorine content of 1 was measured by elemental analysis, it was less than 0.01% by mass (less than the detection limit).

(3) Method -B Method (3) The method was synthesized in the same manner as in Method (3) -A, except that sublimation purification was not performed in Method -A. 1 was obtained. The obtained Compound No. The chlorine content of 1 was determined by elemental analysis and found to be 0.03% by mass.

(3) -C Method (3) Compound A was prepared in the same manner as in Method (A) except that silica gel column chromatography purification was performed only once. 1 was obtained. The obtained Compound No. The chlorine content of 1 was determined by elemental analysis and found to be 0.08% by mass.

(3) -D Method (3) In the method -A, synthesis was performed in the same manner as in the method (3) -A except that silica gel chromatography purification was performed only once and sublimation purification was not performed. 1 was obtained. The obtained Compound No. The chlorine content of 1 was determined by elemental analysis and found to be 0.4% by mass.

(3) -E Method (3) The method was synthesized in the same manner as in (3) -A method except that silica gel column chromatographic purification was not performed. 1 was obtained. The obtained Compound No. The chlorine content of 1 was determined by elemental analysis and found to be 0.5% by mass.

(3) -F Method (3) The method was synthesized in the same manner as in (3) -A except that sublimation purification and silica gel column chromatography purification were not performed. 1 was obtained. It was 0.8 mass%.

(Preparation of electrolyte)
The electrolyte solution 15 used a mixed solvent of PC, EC, and DEC (volume ratio: 20/20/60) as a solvent, and 1 mol / L LiPF ₆ was dissolved in the solvent. Furthermore, compound No. 1 synthesized by the method (3) -A to (3) -F was used. 1 was adjusted to 3.0% by mass with respect to the total mass of the electrolytic solution.

  The electrolytic solution prepared as described above was sealed and stored at a dew point of −60 ° C. for 30 days. The electrolyte solution after 30 days was sampled and the absorption spectrum was measured. The absorption spectrum of the electrolyte solution containing MMDS synthesized by the (3) -E method and the (3) -F method showed a peak in the vicinity of 367 nm, and the color changed from colorless and transparent to light brown. On the other hand, the absorption spectrum of the electrolyte containing MMDS synthesized by the methods (3) -A, (3) -B, (3) -C, and (3) -D is not observed in the vicinity of 367 nm, and the color change is I couldn't see it.

(Production and evaluation of batteries)
(Example 1)
The positive electrode was used as a composite oxide of lithium manganate and lithium nickelate. A film-sheathed battery was manufactured using LiNi _0.8 Co _0.2 O ₂ having a surface area of 1.7 m ² / g and using an aluminum laminate film as the outer package.

First, lithium manganate, LiNi _0.8 Co _0.2 O ₂ and a conductivity-imparting agent were dry-mixed and uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which PVDF as a binder was dissolved to prepare a slurry. . Carbon black was used as the conductivity imparting agent. The slurry was applied on an aluminum metal foil having a thickness of 25 μm, and NMP was evaporated to obtain a positive electrode sheet. The solid content ratio in the positive electrode was a mixture ratio (a = 10) of lithium manganate: LiNi _0.8 Co _0.2 O ₂ : conductivity imparting agent: PVDF = 72: 8: 10: 10 (% by weight).
On the other hand, the negative electrode sheet was prepared by mixing in a ratio of carbon: PVDF = 90: 10 (% by weight), dispersing in NMP, and coating on a 20 μm thick copper foil.

  The electrode sheets of the positive electrode and the negative electrode produced as described above were alternately laminated through a 25 μm thick polyethylene porous membrane separator to produce a laminated electrode body composed of 12 positive electrode layers and 13 negative electrode layers.

  On the other hand, two laminated films having a structure in which polypropylene resin (sealing layer, thickness 70 μm), polyethylene terephthalate (20 μm), aluminum (50 μm), and polyethylene terephthalate (20 μm) are laminated in this order are cut into a predetermined size, and a part thereof A recess having a bottom surface portion and a side surface portion suitable for the size of the laminated electrode body was formed. The laminated electrode body was wrapped with these facing each other, and the periphery was heat-sealed to produce a film-clad battery. The laminated electrode body was impregnated with the electrolytic solution described above before the last side was heat sealed.

  As described above, a laminate-coated secondary battery (120 × 80 × 4 mm) of Example 1 was produced. Using this laminated battery, at room temperature (25 ° C.), it was charged at a constant current and a constant voltage of 2 A for 5 hours to a final voltage of 4.3 V, and then charged to a final voltage of 2.5 V under a constant current of 2 A. This charge / discharge was repeated.

  The storage characteristics were evaluated using the secondary battery obtained here. First, charging and discharging were performed once at room temperature. The charging current and discharging current at this time are constant (2A), the charging capacity at this time is the initial capacity, and the resistance at that time is the initial resistance. The discharge-side cutoff potential was 2.5 V, and the charge-side cutoff potential was 4.3 V. Then, after charging for 2.5 hours to 4.2 V at a constant current and constant voltage of 2 A, the battery was charged to a discharge depth of 50%, and then left at 55 ° C. for 90 days. After being left standing, the discharging operation was performed again at a constant current at room temperature. Subsequently, charging and discharging were repeated once again at the same constant current, the resistance during charging was measured, and the discharging capacity was defined as the recovery capacity. Furthermore, the volume of the laminate-clad battery after being left for 90 days was measured and taken as the amount of cell swelling (gas generation amount). The results are shown in Table 1.

(Example 2)
(3) Compound No. synthesized by Method -B A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 1 was used. The results are shown in Table 1.

(Example 3)
(3) Compound No. synthesized by Method -C A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 1 was used. The results are shown in Table 1.

Example 4
(3) Compound No. synthesized by Method -D A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 1 was used. The results are shown in Table 1.

(Comparative Example 1)
(3) Compound No. synthesized by the -E method A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 1 was used. The results are shown in Table 1.

(Comparative Example 2)
(3) Compound No. synthesized by Method -F A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 1 was used. The results are shown in Table 1.
As shown in Example 5 and Example 6, when the chlorine concentration in the electrolyte is 150 ppm or more, the electrolyte is colored, the capacity recovery rate is extremely reduced to less than 80%, the resistance increase rate and the cell volume change It can be seen that the amount (the amount of gas generated by the decomposition of the electrolyte) is extremely large.

(Execution synthesis example 2)
(Synthesis of ethylenemethane disulfonate (EMDS) shown in Compound No. 2)
(4)-Method A Dry glyme of MDSC (21.33 g; 100 mmol) in a solution of ethylene glycol (6.21 g; 100 mmol) in DME (1000 ml) with stirring at −34 to −40 ° C. in a nitrogen stream. 140 ml) The solution was added dropwise over 20 minutes. Thereafter, a dry glyme (140 ml) solution of dry triethylamine (20.27 g; 200 mmol) was stirred in a nitrogen stream at −11 to −20 ° C., then returned to room temperature and stirred for 1 hour. Continued. After distilling off the solvent under reduced pressure, the residue was poured into ice-cold water and stirred for 10 minutes. The precipitated white crystals were collected by filtration, and the filtered product was washed with ice-cold water and dried at 50 ° C. under reduced pressure to obtain the desired product. EMDS (10.86 g; 53.71 mmol; 53.7%) was obtained. The obtained EMDS (2.44 g; 12.07 mmol) was purified by sublimation in an oil bath at 111 to 117 ° C. under a reduced pressure of 3 to 8 Pa for 15 hours to obtain EMDS (2.06 g; 10.19 mmol; 84.4%) was obtained. This was further purified by silica gel chromatography twice to obtain EMDS. The obtained Compound No. 2 (EMDS) confirmed the structure by NMR findings. Moreover, when the chlorine content was confirmed by elemental analysis, the content was less than 0.01% (less than the detection limit).

(4) Method -B In the method (4) -A, synthesis was performed in the same manner as in the method (4) -A, except that sublimation purification was not performed. 2 was obtained. The obtained Compound No. It was 0.04 mass% when the chlorine content of 2 was calculated | required by the elemental analysis.

(4) -C Method (4) The method was synthesized in the same manner as in (4) -A except that silica gel column chromatography purification was performed only once in Method (A). 2 was obtained. The obtained Compound No. The chlorine content of 2 was determined by elemental analysis and found to be 0.10% by mass.

(4) -D Method (4) In the method -A, synthesis was carried out in the same manner as in the method (4) -A except that silica gel chromatography purification was performed only once and sublimation purification was not performed. 2 was obtained. The obtained Compound No. It was 0.45 mass% when the chlorine content of 2 was calculated | required by the elemental analysis.

(4) -E Method (4) A compound No. 4 was synthesized in the same manner as in (4) -A method except that silica gel column chromatography purification was not performed. 2 was obtained. The obtained Compound No. It was 0.62 mass% when the chlorine content of 2 was calculated | required by the elemental analysis.

(4) -F Method (4) A compound No. 4 was synthesized in the same manner as (4) -A method except that sublimation purification and silica gel column chromatography purification were not performed. 2 was obtained. It was 0.85 mass%.

(Preparation of electrolyte)
The electrolyte solution 15 used a mixed solvent of PC, EC, and DEC (volume ratio: 20/20/60) as a solvent, and 1 mol / L LiPF ₆ was dissolved in the solvent. Furthermore, compound No. 1 synthesized by the method (4) -A to (4) -F was used. 1 was adjusted to 3.0% by mass with respect to the total mass of the electrolytic solution.

  The electrolytic solution prepared as described above was sealed and stored at a dew point of −60 ° C. for 30 days. The electrolyte solution after 30 days was sampled and the absorption spectrum was measured. Compound Nos. Synthesized by the methods (4) -E and (4) -F. The absorption spectrum of the electrolyte solution containing 2 showed a peak at around 367 nm and changed from colorless and transparent to light brown. On the other hand, compound No. 4 synthesized by the methods (4) -A, (4) -B, (4) -C and (4) -D. In the absorption spectrum of the electrolytic solution containing 2, no peak near 367 nm was observed, and no discoloration was observed.

(Production of battery)
(Example 5)
(4) Compound No. synthesized by Method -A A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 2 was used. The results are shown in Table 4.

(Example 6)
(4) Compound No. synthesized by Method B A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 2 was used. The results are shown in Table 4.

(Example 7)
(4) Compound No. synthesized by Method -C A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 2 was used. The results are shown in Table 4.

(Example 8)
(4) Compound No. synthesized by Method -D A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 2 was used. The results are shown in Table 4.

(Comparative Example 3)
(4) Compound No. synthesized by the -E method A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 2 was used. The results are shown in Table 4.

(Comparative Example 4)
(4) Compound No. synthesized by Method -F A secondary battery was prepared and evaluated in the same manner as in Example 1 except that the electrolytic solution using 2 was used. The results are shown in Table 4.

It is a schematic block diagram of the secondary battery which concerns on this invention.

Explanation of symbols

11 Positive Electrode Current Collector 12 Layer Containing Positive Electrode Active Material 13 Layer Containing Negative Electrode Active Material 14 Negative Electrode Current Collector 15 Nonaqueous Electrolyte Solution 16 Porous Separator

Claims (16)

  An electrolytic solution for a secondary battery containing at least an aprotic solvent and a cyclic disulfonic acid ester, wherein the concentration of the cyclic disulfonic acid ester in the electrolytic solution is 0.1% by mass or more and 5.0% by mass or less. An electrolyte solution for a secondary battery, wherein the ratio of chlorine in the electrolyte solution is less than 150 ppm on a mass basis. The electrolyte solution for secondary batteries according to claim 1, wherein the cyclic disulfonic acid ester is represented by the following general formula (1).

(However, in the above general formula (1), A is a substituted or unsubstituted C1-C5 alkylene group, carbonyl group, sulfinyl group, which may be branched, or substituted or unsubstituted which may be branched. A perfluoroalkylene group having 1 to 5 carbon atoms, a substituted or unsubstituted fluoroalkylene group having 2 to 6 carbon atoms which may be branched, and a substituted or unsubstituted carbon number which may be branched including an ether bond A 1-6 alkylene group, a substituted or unsubstituted C1-C6 perfluoroalkylene group that may contain an ether bond, or an ether bond, or a C2-6 substitution that may contain a ether bond Alternatively, it represents an unsubstituted fluoroalkylene group, and B represents a substituted or unsubstituted alkylene group which may be branched.) The electrolyte solution for a secondary battery according to claim 2, wherein the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (2).

(However, in the said General formula (2), x is 0 or 1, n is an integer of 1-5, and R shows a hydrogen atom, a methyl group, an ethyl group, or a halogen atom.) The electrolyte solution for a secondary battery according to claim 2, wherein the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (3).

(However, in the general formula (3), x is 0 or 1, n is an integer of 1 to 5, and R represents a hydrogen atom, a methyl group, an ethyl group, or a halogen atom.) The electrolyte solution for a secondary battery according to claim 2, wherein the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (4).

(However, in the above general formula (4), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4, and k + m + n is 3 to 6. R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.) The electrolyte solution for a secondary battery according to claim 2, wherein the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (5).

(However, in the general formula (5), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4 and k + m + n is 3 to 6.) R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.) The electrolyte solution for secondary batteries according to claim 2, wherein the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (6).

(However, in the general formula (6), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4, and k + m + n is 3 to 6.) And R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.) The electrolyte solution for a secondary battery according to claim 2, wherein the compound represented by the general formula (1) is a cyclic disulfonic acid ester represented by the following general formula (7).

(However, in the general formula (6), x is 0 or 1, k and m are each independently 1 or 2, n is an integer of 1 to 4, and k + m + n is 3 to 6.) And R represents a hydrogen atom, a methyl group, an ethyl group or a halogen atom.)   The aprotic solvent is at least selected from the group consisting of cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, γ-lactones, cyclic ethers, chain ethers and their fluorinated derivatives. The electrolyte solution for secondary batteries according to any one of claims 1 to 8, comprising one kind of organic solvent. LiPF ₆ wherein the secondary battery electrolyte, as further lithium _{salt, LiBF 4, LiAsF 6, LiSbF} 6, LiClO 4, LiAlCl 4, LiN (C k F 2k + 1 SO 2) 2 and LiN (C _n F _{2n +1 SO 2) (C m F} 2m + 1 SO 2) (n, m are any one of the preceding claims, characterized in that it comprises at least one member selected from the group consisting of natural numbers) The electrolyte solution for secondary batteries as described.   A secondary battery comprising a positive electrode, a negative electrode, and a secondary battery electrolyte, wherein the secondary battery electrolyte is the secondary battery electrolyte according to any one of claims 1 to 10. A secondary battery characterized by that.   The secondary battery according to claim 11, wherein the positive electrode includes a lithium-containing composite oxide as a positive electrode active material.   The negative electrode includes at least one selected from the group consisting of a material capable of inserting and extracting lithium as a negative electrode active material, a lithium metal, a metal material capable of forming an alloy with lithium, and an oxide material. The secondary battery according to claim 11 or 12.   The secondary battery according to claim 11, wherein the negative electrode has carbon as a negative electrode active material.   The secondary battery according to claim 14, wherein the carbon is graphite.   The secondary battery according to claim 14, wherein the carbon is amorphous carbon.

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