JP6411269B2 - Non-aqueous electrolyte additive, non-aqueous electrolyte, and electricity storage device - Google Patents

Description

  The present invention relates to an additive for non-aqueous electrolyte, a non-aqueous electrolyte, and an electricity storage device.

  In recent years, research on non-aqueous electrolyte secondary batteries represented by lithium ion batteries has been extensively conducted as interest in solving environmental problems and realizing a sustainable recycling society has increased. Lithium ion batteries have high working voltage and energy density, and are therefore used as power sources for notebook computers and mobile phones. Since lithium ion batteries have a higher energy density than lead batteries and nickel cadmium batteries, realization of higher capacity of the batteries is expected.

  However, the lithium ion battery has a problem that the capacity of the battery decreases as the charge / discharge cycle progresses. The cause of the decrease in capacity is, for example, the decomposition of the electrolyte solution due to the electrode reaction, the decrease in the impregnation property of the electrolyte into the electrode active material layer, and the decrease in the lithium ion intercalation efficiency with a long charge / discharge cycle. It is thought that this is caused by

  Methods for adding various additives to an electrolytic solution have been studied as a method for suppressing a decrease in battery capacity associated with a charge / discharge cycle. Additives are generally decomposed during the first charge and discharge to form a film called a solid electrolyte interface (SEI) on the electrode surface. Since the SEI is formed in the first charge / discharge cycle, lithium ions can move back and forth through the SEI while suppressing the consumption of electricity for the decomposition of the electrolyte during the subsequent charge / discharge. That is, it is considered that the formation of SEI plays a major role in suppressing the deterioration of the secondary battery when the charge / discharge cycle is repeated and improving the battery characteristics, storage characteristics, load characteristics, and the like.

  For example, Patent Documents 1 to 3 include cyclic monosulfonic acid esters, Patent Document 4 to sulfur-containing aromatic compounds, Patent Document 5 to disulfide compounds, and Patent Documents 6 to 9 to disulfonic acid. Each ester is disclosed. Patent Documents 10 to 15 disclose cyclic carbonates or cyclic sulfones, Patent Document 16 discloses a compound having a nitrogen-containing cyclic group and an electron-withdrawing group, and Patent Document 17 discloses an electrolytic solution containing a compound containing a sulfonic acid amide group. doing.

JP 63-102173 A JP 2000-003724 A JP 11-339850 A JP 05-258753 A JP 2001-052735 A JP 2009-038018 A JP-A-2005-203341 JP 2004-281325 A JP 2005-228631 A Japanese Unexamined Patent Publication No. 04-87156 Japanese Patent Laid-Open No. 10-50342 Japanese Patent Application Laid-Open No. 08-45545 JP 2001-6729 A JP 63-102173 A Japanese Patent Laid-Open No. 05-074486 JP 2014-127354 A JP 2014-194866 A

Geun-Chang, Hyung-Jin Kim, Seung-ll Yu, Song-Hui Jun, Jong-Wook Choi, Myung-Hwan Kim. Journal of The Electrochemical Society, 147, 12, 4391 (2000)

  A compound having a low LUMO energy is an excellent electron acceptor and is considered to be able to form stable SEI on the surface of an electrode such as a non-aqueous electrolyte secondary battery (for example, Non-Patent Document 1).

  Although some of conventional additives such as compounds disclosed in Patent Documents 1 to 9 exhibit low LUMO energy, they are chemically unstable and easily deteriorate due to the influence of moisture and temperature. Had. For example, although a disulfonic acid ester compound exhibits low LUMO energy, it has a low stability to moisture and easily deteriorates. Therefore, when it is stored for a long period of time, it is necessary to strictly control the moisture content and temperature. In general, the lithium ion battery is required to have a heat resistant temperature of about 60 ° C. and the lithium ion capacitor is about 80 ° C. Therefore, the improvement of the non-aqueous electrolyte additive used in the electricity storage device at high temperature is It was one of the important issues.

  In addition, in the case of an electrolytic solution containing a conventional additive, when the power storage device is used over a long period of time while repeating the charge / discharge cycle, the battery characteristics of the power storage device are likely to be deteriorated. There was a need for improvement.

  The electrolyte solutions described in Patent Documents 10 to 14 can suppress irreversible capacity reduction to some extent by SEI generated on the negative electrode surface by electrochemical reductive decomposition. However, although the SEI formed by the additive in these electrolytes is excellent in the performance of protecting the electrode, it is not sufficient in terms of strength to withstand long-term use. When the SEI is decomposed or the SEI is cracked, the surface of the negative electrode is exposed, and the electrolytic solution solvent is decomposed to deteriorate the battery characteristics. The electrolytic solution using the vinylene carbonate-based compound described in Patent Document 15 as an additive generates carbon dioxide and other gases when vinylene carbonate is decomposed on the electrode, resulting in a decrease in battery performance. It had the problem of being connected. The gas generation is particularly remarkable when a charge / discharge cycle is repeated at a high temperature or for a long time.

  As described above, the additive for non-aqueous electrolyte has room for further improvement in terms of storage stability, cycle characteristics for maintaining performance when a charge / discharge cycle is repeated, or suppression of gas generation.

  Accordingly, a main object of the present invention is to provide an additive for a non-aqueous electrolyte that has high storage stability and enables improvement of cycle characteristics and suppression of gas generation for an electricity storage device.

  The present inventors have found that a compound containing a specific partial structure exhibits low LUMO energy and is chemically stable. Furthermore, the present inventors have found that when such a compound is used as an additive for a non-aqueous electrolyte, excellent cycle characteristics are obtained and gas generation is suppressed, and the present invention has been completed. .

  That is, one aspect of the present invention provides a non-aqueous electrolyte additive containing a compound represented by the following formula (1).

In Formula (1), X ¹ represents a group that forms a cyclic group together with a sulfur atom and a nitrogen atom, R ¹ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, and optionally substituted carbon atoms. An alkenyl group having 2 to 4 carbon atoms, an alkynyl group having 1 to 4 carbon atoms which may be substituted, an alkoxy group having 1 to 4 carbon atoms which may be substituted, an aryl group which may be substituted, Heteroaryl group which may be substituted, aryloxy group which may be substituted, heteroaryloxy group which may be substituted, alkenyloxy group having 2 to 4 carbon atoms which may be substituted, carbon which may be substituted The alkynyloxy group of number 2-4, or the amino group which may be substituted is shown.

  The compound represented by the formula (1) has a cyclic structure including a sulfonamide bond, and a sulfonyl group is further bonded to the sulfonamide bond. It is thought that SEI containing a large number of polar groups containing sulfur atoms and the like is formed. SEI containing a large number of such polar groups is considered to have excellent ionic conductivity and sufficient strength to withstand long-term use.

  ADVANTAGE OF THE INVENTION According to this invention, while having high storage stability, regarding an electrical storage device, the additive for nonaqueous electrolyte solutions which makes it possible to improve cycling characteristics and to suppress gas generation is provided. The non-aqueous electrolyte additive according to some embodiments forms a stable solid electrolyte interface on the electrode surface when used in an electricity storage device such as a non-aqueous electrolyte secondary battery or an electric double layer capacitor. Thus, battery characteristics such as cycle characteristics, charge / discharge capacity, and internal resistance can be improved.

It is sectional drawing which shows one Embodiment of an electrical storage device.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  The additive for nonaqueous electrolysis according to the present embodiment contains one or more compounds represented by the following formula (1).

In formula (1), X ¹ represents a group that forms a cyclic group together with a sulfur atom and a nitrogen atom. The cyclic group formed by X ¹ may be substituted. This cyclic group may be a 4- to 6-membered ring or a condensed ring containing two or more rings. From the viewpoint of effects such as recycling characteristics and gas generation suppression, the cyclic group may contain a sulfonyl group (—S (═O) ₂ —) and / or a carbonyl group (—C (═O) —). It may contain a sulfonyl group or a carbonyl group bonded to the nitrogen atom constituting the sulfonamide bond as in formula (2).

In Formula (2), X ² represents a group that forms a cyclic group together with a sulfur atom, a nitrogen atom, and Z, and Z represents a sulfonyl group or a carbonyl group. The cyclic group formed by X ² may be a 4- to 6-membered ring or a condensed ring containing two or more rings. R ¹ has the same meaning as ^{R 1} in formula (1).

  Specific examples of the compound of the formula (2) include a compound represented by the following formula (2a), (2b) or (2c). According to these compounds, particularly excellent effects can be obtained from the viewpoint of suppressing gas generation.

In formulas (2a), (2b) and (2c), R ² , R ³ and R ⁴ are each an optionally substituted alkyl group having 1 to 4 carbon atoms, and optionally having 1 to 4 carbon atoms. An alkoxy group, a nitro group, an amino group, a sulfonyl group, or a halogen atom. m represents an integer of 0 to 4, n represents an integer of 0 to 2, and o represents an integer of 0 to 4. From the viewpoints of availability, reactivity, etc., m may be 0 or 1, n may be 0 or 1, and o may be 0 or 1. R ¹ has the same meaning as ^{R 1} in formula (1). When m, n, and o are 2 or more, the plurality of R ² , R ^3, and R ⁴ may be the same or different, but are preferably the same.

Specific examples of the optionally substituted alkyl group having 1 to 4 carbon atoms as R ² , R ³ or R ⁴ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. And t-butyl groups. Among these, from the viewpoints of availability and reactivity, R ^{2 to} R ⁴ may be a methyl group.

Specific examples of the optionally substituted alkoxy group having 1 to 4 carbon atoms as R ² , R ³ or R ⁴ include a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group. Among these, R ^{2 to} R ⁴ may be a methoxy group from the viewpoints of availability and reactivity.

The halogen atom as R ² , R ³ or R ⁴ may be a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. Among these, from the viewpoints of availability and reactivity, R ^{2 to} R ⁴ may be fluorine atoms.

R ¹ in formula (1) and formulas (2a) to (2c) is an optionally substituted alkyl group having 1 to 4 carbon atoms, an optionally substituted alkynyl group having 1 to 4 carbon atoms, Optionally substituted alkenyl group having 2 to 4 carbon atoms, optionally substituted alkoxy group having 1 to 4 carbon atoms, optionally substituted aryl group, optionally substituted heteroaryl group, substituted An optionally substituted aryloxy group, an optionally substituted heteroaryloxy group, an optionally substituted alkenyloxy group having 2 to 4 carbon atoms, an optionally substituted alkynyloxy group having 2 to 4 carbon atoms A group or an optionally substituted amino group is shown. Especially, since SEI excellent in ion conductivity can be formed, R ¹ is an optionally substituted alkyl group having 1 to 4 carbon atoms, an optionally substituted alkoxy group having 1 to 4 carbon atoms, and substituted. It may be an optionally substituted phenoxy group, an optionally substituted alkenyloxy group having 2 to 4 carbon atoms, or an optionally substituted amino group. The negative electrode formed of SEI by polymerization of allyl occurs is promoted in, since it is possible to form a good SEI, R ¹ may be an alkenyloxy group having 2 to 4 carbon atoms. Among them, R ¹ may be a methyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyloxy group, a p-methylphenyloxy group, a dimethylamino group, a benzylmethylamino group, or an allylamino group. preferable.

Specific examples of the optionally substituted alkyl group having 1 to 4 carbon atoms as R ¹ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, It includes a trifluoromethyl group, a 1,1-dichloroethyl group, and an optionally substituted benzyl group. The optionally substituted benzyl group includes, for example, a benzyl group, 2-methylbenzyl group, 3-methylbenzyl group, 4-methylbenzyl group, 2-ethylbenzyl group, 3-ethylbenzyl group, 4-ethylbenzyl group. 2-methoxybenzyl group, 3-methoxybenzyl group, 4-methoxybenzyl group, 2-ethoxybenzyl group, 3-ethoxybenzyl group, 4-ethoxybenzyl group, 2- (dimethylamino) benzyl group, 3- (dimethyl Amino) benzyl group, 4- (dimethylamino) benzyl group, 2-fluorobenzyl group, 3-fluorobenzyl group, 4-fluorobenzyl group, 2-chlorobenzyl group, 3-chlorobenzyl group, 4-chlorobenzyl group, It may be a 2-bromobenzyl group, a 3-bromobenzyl group, or a 4-bromobenzyl group.

Specific examples of the optionally substituted alkynyl group having 2 to 4 carbon atoms as R ¹ include ethynyl group, 1-propynyl group, 2-1-propynyl group, 1-butynyl group, 2-1-butynyl group, and 3-1-butynyl. Contains groups.

Specific examples of the optionally substituted alkenyl group having 2 to 4 carbon atoms as R ¹ include a vinyl group, an allyl group, an isopropenyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, and an isobutenyl group. And 1,1-difluoro-1-propenyl group. Among these, R ¹ may be an allyl group.

Specific examples of the optionally substituted alkoxy group having 1 to 4 carbon atoms as R ¹ include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, a trifluoromethoxy group, a trichloromethoxy group, and a substituted group. A benzyloxy group which may be substituted. The optionally substituted benzyloxy group includes, for example, benzyloxy group, 2-methylbenzyloxy group, 3-methylbenzyloxy group, 4-methylbenzyloxy group, 2-ethylbenzyloxy group, 3-ethylbenzyloxy group. Group, 4-ethylbenzyloxy group, 2-methoxybenzyloxy group, 3-methoxybenzyloxy group, 4-methoxybenzyloxy group, 2-ethoxybenzyloxy group, 3-ethoxybenzyloxy group, 4-ethoxybenzyloxy group 2- (dimethylamino) benzyloxy group, 3- (dimethylamino) benzyloxy group, 4- (dimethylamino) benzyloxy group, 2-fluorobenzyloxy group, 3-fluorobenzyloxy group, 4-fluorobenzyloxy Group, 2-chlorobenzyloxy group, 3-chloroben Aryloxy group, 4-chlorobenzyl group, 2-bromobenzyl group, 3-bromobenzyl group, or a 4-bromobenzyl group.

Specific examples of the optionally substituted aryl group or heteroaryl group as R ¹ are phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 2-ethylphenyl group, 3- Ethylphenyl group, 4-ethylphenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, 2-ethoxyphenyl group, 3-ethoxyphenyl group, 4-ethoxyphenyl group, 2- (dimethyl) Amino) phenyl group, 3- (dimethylamino) phenyl group, 4- (dimethylamino) phenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 2-chlorophenyl group, 3-chlorophenyl group 4-chlorophenyl group, 2-bromophenyl group, 3-bromophenyl group, 4-bromophenyl group , Furyl group, thienyl group, pyridyl group, oxazolyl group, imidazolyl group, and quinolyl group. Among them, R ¹ may be a phenyl group, a 2-fluorophenyl group, a 3-fluorophenyl group, or a 4-fluorophenyl group because it exhibits a low LUMO energy that is susceptible to electrochemical reduction.

Specific examples of the optionally substituted aryloxy group or heteroaryloxy group as R ¹ include phenoxy group, 2-methylphenoxy group, 3-methylphenoxy group, 4-methylphenoxy group, 2-ethylphenoxy group, 3-ethylphenoxy group, 4-ethylphenoxy group, 2-methoxyphenoxy group, 3-methoxyphenoxy group, 4-methoxyphenoxy group, 2-ethoxyphenoxy group, 3-ethoxyphenoxy group, 4-ethoxyphenoxy group, 2- (Dimethylamino) phenoxy group, 3- (dimethylamino) phenoxy group, 4- (dimethylamino) phenoxy group, 2-fluorophenoxy group, 3-fluorophenoxy group, 4-fluorophenoxy group, 2-chlorophenoxy group, 3 -Chlorophenoxy group, 4-chlorophenoxy group, 2-bromine Including mophenoxy group, 3-bromophenoxy group, 4-bromophenoxy group, furyloxy group, thienyloxy group, pyridyloxy group, oxazolyloxy group, imidazolyloxy group, and quinolyloxy group.

Specific examples of the optionally substituted alkenyloxy group having 2 to 4 carbon atoms as R ¹ include a 2-propenyloxy group, a 1-methyl-2-propenyloxy group, a 2-methyl-2-propenyloxy group, 2-butenyloxy group, 3-butenyloxy group, 2-hexenyloxy group, and 5-hexenyloxy group are included.

Specific examples of the optionally substituted alkynyloxy group having 2 to 4 carbon atoms as R ¹ include an ethynyloxy group, a 1-propynyloxy group, a 2-propynyloxy group, a 1-butynyloxy group, a 2-butynyloxy group, And a tri-butynyloxy group.

The optionally substituted amino group as R ¹ can be represented by, for example, the following formula (10).

In formula (10), R ¹¹ and R ¹² are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, an optionally substituted alkenyl group having 2 to 4 carbon atoms, An aryl group which may be substituted or a heteroaryl group which may be substituted is shown, and R ¹¹ and R ¹² may be bonded to each other to form a divalent group.

The optionally substituted alkyl group, optionally substituted alkenyl group, optionally substituted aryl group, and optionally substituted heteroaryl group as R ¹¹ or R ¹² are exemplified with respect to R ^1. It may be the same as that described. Specific examples of R ¹¹ and R ¹² include a methyl group, an n-butyl group, an allyl group, a phenyl group, and a benzyl group. Specific examples of the amino group represented by the formula (10) include a dimethylamino group, an n-butylmethylamino group, an allylamino group, a phenylmethylamino group, and a benzylmethylamino group.

R ^{1 to} R ⁴ , R ¹¹ and R ¹² are an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryl group, a heteroaryl group, an aryloxy group, a heteroaryloxy group, an alkenyloxyalkyl group, or an alkynyloxy group. In some cases, the substituent that can be bonded to these includes, for example, a halogen atom, an amino group, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an aryl group, It is selected from a heteroaryl group, a heteroaryl group, an aryloxy group, a heteroaryloxy group, and an alkenyloxy group having 2 to 4 carbon atoms. When the substituent is a halogen atom, particularly a fluorine atom, the LUMO energy tends to be low.

  Since the compound of formula (1) exhibits low LUMO energy that is susceptible to electrochemical reduction, a non-aqueous electrolyte containing this as an additive for a non-aqueous electrolyte is a storage battery such as a non-aqueous electrolyte secondary battery. When used in a device, stable SEI can be formed on the electrode surface to improve battery characteristics such as cycle characteristics, charge / discharge capacity, and internal resistance. Moreover, since the compound of Formula (1) is stable with respect to moisture and temperature changes, the additive for non-aqueous electrolyte and the non-aqueous electrolyte containing it can be stored at room temperature for a long time. is there.

  The lowest unoccupied molecular orbital (LUMO) energy of the compound represented by the formula (1) may be −3.0 eV or more, or 0.0 eV or less. When the LUMO energy is −3.0 eV or more, it is easy to avoid the formation of SEI showing high resistance on the negative electrode due to excessive decomposition of the compound. When the LUMO energy is 0.0 eV or less, more stable SEI can be more easily formed on the negative electrode surface. From the same viewpoint, the LUMO energy may be -2.9 eV or more, or -0.5 eV or less. A person skilled in the art can find compounds exhibiting LUMO energy within these numerical ranges within the range defined by the formula (1) without undue trial and error.

  In this specification, “lowest unoccupied molecular orbital (LUMO) energy” is a value calculated by combining the semi-empirical molecular orbital calculation method PM3 and the density functional method B3LYP method. Specifically, the LUMO energy can be calculated using Gaussian 03 (Revision B.03, software manufactured by Gaussian, USA).

  A person skilled in the art can synthesize the compound of the formula (1) by combining usual reactions using available raw materials. For example, the compound of formula (1) can be synthesized by a method in which a corresponding sulfonyl halide compound is reacted with a cyclic compound containing a sulfonamide bond.

  The additive for non-aqueous electrolyte according to the present embodiment may contain other general components such as a compound that can contribute to SEI formation in addition to the compound of the formula (1). Or you may use only the compound of Formula (1) as an additive for non-aqueous electrolytes. The additive for non-aqueous electrolyte according to the present embodiment may contain other general components as long as the effects of the present invention are not impaired. Examples of other general components include vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), flame retardant, negative electrode protective agent, positive electrode protective agent, and overcharge inhibitor. Is mentioned.

  The non-aqueous electrolyte according to this embodiment contains the additive for non-aqueous electrolyte, a non-aqueous solvent, and an electrolyte. The content of the non-aqueous electrolyte additive (or the compound of formula (1)) in the non-aqueous electrolyte may be 0.005% by mass or more based on the total mass of the non-aqueous electrolyte. It may be 10% by mass or less. If this content is 0.005% by mass or more, stable SEI tends to be sufficiently formed by an electrochemical reaction on the electrode surface. When the content is 10% by mass or less, the non-aqueous electrolyte additive can be easily dissolved in the non-aqueous solvent. In addition, by not excessively increasing the content of the additive for nonaqueous electrolyte, an increase in viscosity of the nonaqueous electrolyte can be suppressed, and ion mobility can be particularly ensured. If the mobility of ions is not sufficiently ensured, the conductivity of the non-aqueous electrolyte cannot be sufficiently ensured, and the charge / discharge characteristics of the electricity storage device may be hindered. From the same viewpoint, the lower limit of the content of the non-aqueous electrolyte additive (or the compound of formula (1)) may be 0.01% by mass.

  The non-aqueous electrolyte may contain two or more additives for non-aqueous electrolyte (two or more compounds that form SEI). In this case, the total content of the non-aqueous electrolyte additive may be 0.005% by mass or more, or 10% by mass or less. Examples of other additives include vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propane sultone (PS).

  As the non-aqueous solvent, an aprotic solvent can be selected from the viewpoint of keeping the viscosity of the obtained non-aqueous electrolyte low. The aprotic solvent is at least one selected from the group consisting of cyclic carbonate, chain carbonate, aliphatic carboxylic acid ester, lactone, lactam, cyclic ether, chain ether, sulfone, nitrile, and halogen derivatives thereof. It may be. Among these, the aprotic solvent may be a cyclic carbonate and / or a chain carbonate.

  Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of the aliphatic carboxylic acid ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and methyl trimethyl acetate. Examples of lactones include γ-butyrolactone. Examples of the lactam include ε-caprolactam and N-methylpyrrolidone. Examples of the cyclic ether include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and 1,3-dioxolane. Examples of the chain ether include 1,2-diethoxyethane and ethoxymethoxyethane. Examples of the sulfone include sulfolane. Examples of nitriles include acetonitrile. Examples of the halogen derivative include 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one Is mentioned. These nonaqueous solvents may be used alone or in combination of two or more. These nonaqueous solvents are particularly suitable for use in non-aqueous electrolyte secondary batteries such as lithium ion batteries and electric double layer capacitors such as lithium ion capacitors.

The electrolyte constituting the non-aqueous electrolyte may be a lithium salt that serves as an ion source of lithium ions. Among them, the _{electrolyte, LiAlCl 4, LiBF 4, LiPF} 6, LiClO 4, LiAsF 6, and may be at least one selected from the group consisting of LiSbF _6. LiBF ₄ and / or LiPF ₆ from the viewpoint that the degree of dissociation is high and the ionic conductivity of the electrolytic solution can be increased, and further, the oxidation-reduction characteristics have the effect of suppressing the performance deterioration of the electricity storage device due to long-term use. May be selected. These electrolytes may be used alone or in combination of two or more. LiBF ₄ and LiPF ₆ can be combined with one or more cyclic carbonates and chain carbonates as non-aqueous solvents. In particular, LiBF ₄ and / or LiPF ₆ may be combined with ethylene carbonate and diethyl carbonate.

  The concentration of the electrolyte in the nonaqueous electrolytic solution may be 0.1 mol / L or more, or 2.0 mol / L or less. When the concentration of the electrolyte is 0.1 mol / L or more, it is easy to sufficiently ensure the conductivity of the nonaqueous electrolytic solution. Therefore, it is easy to obtain stable discharge characteristics and charge characteristics of the electricity storage device. When the electrolyte concentration is 2.0 mol / L or less, an increase in the viscosity of the nonaqueous electrolytic solution can be suppressed, and the mobility of ions can be secured particularly easily. If the ion mobility is not sufficiently ensured, the conductivity of the electrolyte cannot be sufficiently ensured, and the charge / discharge characteristics of the electricity storage device may be hindered. From the same viewpoint, the concentration of the electrolyte may be 0.5 mol / L or more, or 1.5 mol / L or less.

  The electricity storage device according to this embodiment is mainly composed of the non-aqueous electrolyte, a positive electrode, and a negative electrode. Specific examples of the electricity storage device include a non-aqueous electrolyte secondary battery (such as a lithium ion battery) and an electric double layer capacitor (such as a lithium ion capacitor). The nonaqueous electrolytic solution according to the present embodiment is particularly effective in applications of lithium ion batteries and lithium ion capacitors.

  FIG. 1 is a cross-sectional view schematically showing an embodiment of an electricity storage device. An electricity storage device 1 shown in FIG. 1 is a non-aqueous electrolyte secondary battery. The electricity storage device 1 includes a positive electrode plate 4 (positive electrode), a negative electrode plate 7 (negative electrode) facing the positive electrode plate 4, a nonaqueous electrolytic solution 8 disposed between the positive electrode plate 4 and the negative electrode plate 7, and nonaqueous And a separator 9 provided in the electrolytic solution 8. The positive electrode plate 4 includes a positive electrode current collector 2 and a positive electrode active material layer 3 provided on the nonaqueous electrolyte solution 8 side. The negative electrode plate 7 includes a negative electrode current collector 5 and a negative electrode active material layer 6 provided on the nonaqueous electrolyte solution 8 side. As the nonaqueous electrolytic solution 8, the nonaqueous electrolytic solution according to the above-described embodiment can be used. In FIG. 1, a non-aqueous electrolyte secondary battery is shown as the electricity storage device, but the electricity storage device to which the non-aqueous electrolyte can be applied is not limited to this, and other electricity storage devices such as an electric double layer capacitor. It may be.

  The positive electrode current collector 2 and the negative electrode current collector 5 may be metal foils made of a metal such as aluminum, copper, nickel, and stainless steel, for example.

The positive electrode active material layer 3 contains a positive electrode active material. The positive electrode active material may be a lithium-containing composite oxide. Specific examples of the lithium-containing composite oxide _{includes LiMnO 2, LiFeO 2, LiCoO 2} , LiMn 2 O 4, Li 2 FeSiO 4, LiNi 1/3 Co 1/3 Mn 1/3 O 2, and LiFePO _4.

  The negative electrode active material layer 6 contains a negative electrode active material. The negative electrode active material may be a material that can occlude and release lithium, for example. Specific examples of such materials include carbon materials such as graphite and amorphous carbon, and oxide materials such as indium oxide, silicon oxide, tin oxide, zinc oxide and lithium oxide. The negative electrode active material may be a lithium metal or a metal material capable of forming an alloy with lithium. Specific examples of metals that can form alloys with lithium include Cu, Sn, Si, Co, Mn, Fe, Sb, and Ag. A binary or ternary alloy containing these metals and lithium can also be used as the negative electrode active material. These negative electrode active materials may be used alone or in combination of two or more.

  For example, the separator 9 may be a porous film made of polyethylene, polypropylene, fluororesin, or the like.

  Specific forms such as the shape and thickness of each member constituting the power storage device can be set as appropriate by those skilled in the art. The configuration of the power storage device is not limited to the embodiment of FIG. 1 and can be changed as appropriate.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

1. Preparation of non-aqueous electrolyte (Example 1)
Ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of EC: DEC = 30: 70 to prepare a mixed non-aqueous solvent, to which LiPF ₆ is added at 1.0 mol / L as an electrolyte. It dissolved so that it might become a density | concentration. To the obtained solution, the compound 1 shown in Table 1 was added as an additive for non-aqueous electrolyte solution to prepare a non-aqueous electrolyte solution. The content ratio of the additive for non-aqueous electrolyte (Compound 1) was 0.5% by mass based on the total mass of the non-aqueous electrolyte.

(Example 2)
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the content ratio of Compound 1 was 1.0% by mass.

(Example 3)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 2 shown in Table 1 and the content ratio was 1.0% by mass. did.

Example 4
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 3 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Example 5)
A nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 4 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Example 6)
A nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 5 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Example 7)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 6 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Example 8)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 7 shown in Table 1 and the content ratio was 1.0% by mass. did.

Example 9
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 8 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Example 10)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 9 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Comparative Example 1)
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that Compound 1 was not added.

(Comparative Example 2)
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that the additive for non-aqueous electrolyte was changed from Compound 1 to 1,3-propane sultone and the content ratio was 1.0% by mass. .

(Comparative Example 3)
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolytic solution was changed from compound 1 to vinylene carbonate (VC) and the content ratio was 1.0% by mass.

(Comparative Example 4)
A nonaqueous electrolytic solution was prepared in the same manner as in Comparative Example 3 except that the content of vinylene carbonate (VC) was 2.0% by mass.

(Comparative Example 5)
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolytic solution was changed from Compound 1 to fluoroethylene carbonate (FEC) and the content ratio was 1.0% by mass. .

(Comparative Example 6)
A nonaqueous electrolytic solution was prepared in the same manner as in Comparative Example 5 except that the content ratio of fluoroethylene carbonate (FEC) was 2.0% by mass.

(Comparative Example 7)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 10 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Comparative Example 8)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 11 shown in Table 1 and the content ratio was 1.0% by mass. did.

(Comparative Example 9)
The nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the additive for nonaqueous electrolyte solution was changed from compound 1 to compound 12 shown in Table 1 and the content ratio was 1.0% by mass. did.

2. Evaluation (calculation of LUMO energy)
The LUMO (lowest unoccupied molecular orbital) energies of compounds 1-9 used in the examples were determined by semi-empirical molecular orbital calculations with Gaussian 03 software. The calculated LUMO energy is shown in Table 1.

(Stability)
The compounds 1 to 9 used in the examples and the fluoroethylene carbonate (FEC) used in Comparative Examples 5 and 6 are left for 90 days in a constant temperature and humidity environment with a temperature of 40 ± 2 ° C. and a humidity of 75 ± 5%. It used for the preservation | save test. The ¹ H-nuclear magnetic resonance spectrum ( ¹ H-NMR) of each non-aqueous electrolyte additive before and after the storage test was measured, and the stability of each compound was evaluated according to the following criteria. Table 2 shows the stability evaluation results.
○: There was no peak changes in ¹ H-NMR spectrum before and after the storage test.
Δ: Slight peak change in ¹ H-NMR spectrum was confirmed before and after the storage test.
X: A clear peak change in the ¹ H-NMR spectrum was confirmed before and after the storage test.

  As shown in Table 2, the fluoroethylene carbonate (FEC) used in Comparative Examples 5 and 6 was considered to be partially hydrolyzed and had poor stability. On the other hand, compounds 1 to 9 used in the examples showed almost no change and showed excellent stability.

(Preparation of positive electrode)
Lithium cobaltate (LiCoO ₂ ) as a positive electrode active material and carbon black as a conductivity imparting agent were dry mixed. The obtained mixture was uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride (PVDF) was dissolved as a binder to prepare a slurry. The obtained slurry was applied to both surfaces of an aluminum metal foil (square shape, thickness 20 μm). After the coating film was dried to remove NMP, the whole was pressed to obtain a positive electrode sheet having an aluminum metal foil as a positive electrode current collector and a positive electrode active material layer formed on both surfaces thereof. The solid content ratio in the positive electrode active material layer of the positive electrode sheet was a mass ratio of positive electrode active material: conductivity imparting agent: PVDF = 90: 5: 5.

(Preparation of negative electrode)
Graphite powder as a negative electrode active material and carbon black as a conductivity imparting agent were dry mixed. The obtained mixture was uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride (PVDF) was dissolved as a binder to prepare a slurry. The obtained slurry was applied to one side of a copper foil (square shape, thickness 10 μm). After the coating film was dried to remove NMP, the whole was pressed to obtain a negative electrode sheet having a copper foil as a negative electrode current collector and a negative electrode active material layer formed on one surface thereof. The solid content ratio in the negative electrode active material layer of the negative electrode sheet was a mass ratio of negative electrode active material: conductivity imparting agent: PVDF = 93: 3: 4.

(Preparation of non-aqueous electrolyte secondary battery)
In various non-aqueous electrolytes obtained in Examples and Comparative Examples, a polyethylene separator was laminated in the order of a negative electrode, a separator, a positive electrode, a separator, and a negative electrode to prepare a battery element. This battery element was inserted into a bag formed of a laminate film having aluminum (thickness: 40 μm) and a resin layer covering both sides thereof so that the ends of the positive electrode sheet and the negative electrode sheet protruded from the bag. Subsequently, each nonaqueous electrolyte solution obtained in the Examples and Comparative Examples was injected into the bag. The bag was vacuum-sealed to obtain a sheet-like nonaqueous electrolyte secondary battery. Furthermore, in order to improve the adhesiveness between electrodes, the sheet-like nonaqueous electrolyte secondary battery was sandwiched between glass plates and pressurized.

(Evaluation of discharge capacity maintenance ratio and internal resistance ratio)
The non-aqueous electrolyte secondary battery was charged to 4.2 V at a current corresponding to 0.2 C at 25 ° C., and then discharged to 3 V at a current corresponding to 0.2 C, and the battery was repeated two cycles. Stabilized.
Next, a charge / discharge cycle test was performed with a charge rate of 0.3 C, a discharge rate of 0.3 C, a charge end voltage of 4.2 V, and a discharge end voltage of 2.5 V. Table 3 shows the discharge capacity retention ratio (%) after 200 cycles and the internal resistance ratio after 200 cycles for each battery.
“Discharge capacity maintenance rate after 200 cycles (%)” is the ratio (percentage) of the discharge capacity (mAh) after the 200 cycle test to the discharge capacity (mAh) after the 10 cycle test. The “internal resistance ratio after 200 cycles” is the relative value of the resistance after the 200 cycle test when the resistance before the cycle test is 1.

(Measurement of gas generation amount)
Separately from the batteries used in the cycle test, non-aqueous electrolyte secondary batteries having the same configuration including the electrolytes of the examples and comparative examples were prepared. The battery was stabilized by repeating two cycles of charging the battery to 4.2 V at 25 ° C. with a current corresponding to 0.2 C and then discharging to 3 V with a current corresponding to 0.2 C.
Next, the charge rate was set to 0.3 C, and the battery was charged again to 4.2 V. Then, the battery was left in an environment of 60 ° C. for 168 hours. Thereafter, the battery was cooled to room temperature. The amount of gas generated in the battery after standing was measured by the Archimedes method. The results are shown in Table 3.

  From Table 3, the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte solution of each Example including the compounds 1 to 9 which are compounds of the formula (1) is a non-aqueous solution using the non-aqueous electrolyte solution of the comparative example. Compared with the electrolyte secondary battery, it can be seen that both the discharge capacity maintenance rate during the cycle test and the suppression of gas generation accompanying charging are superior. This strongly suggests that the compound of formula (1) forms SEI that is stable to charge / discharge cycles and high-temperature storage when used in non-aqueous electrolyte secondary batteries. Moreover, it was confirmed that the compound of Formula (1) is excellent also in the point that there is little increase in internal resistance by a charging / discharging cycle.

DESCRIPTION OF SYMBOLS 1 ... Power storage device (nonaqueous electrolyte secondary battery), 2 ... Positive electrode current collector, 3 ... Positive electrode active material layer, 4 ... Positive electrode plate, 5 ... Negative electrode current collector, 6 ... Negative electrode active material layer, 7 ... Negative electrode Plate, 8 ... non-aqueous electrolyte, 9 ... separator.

Claims (7)

The additive for non-aqueous electrolyte containing the compound represented by following formula (1).

[In the formula (1), X ¹ represents a group to form a cyclic group together with a sulfur atom and a nitrogen atom, R ¹ is an optionally substituted alkyl group having 1 to 4 carbon atoms, optionally substituted carbon An alkynyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms that may be substituted, an alkoxy group having 1 to 4 carbon atoms that may be substituted, an aryl group that may be substituted, and a substituent An optionally substituted heteroaryl group, an optionally substituted aryloxy group, an optionally substituted heteroaryloxy group, an optionally substituted alkenyloxy group having 2 to 4 carbon atoms, and optionally substituted. An alkynyloxy group having 2 to 4 carbon atoms or an optionally substituted amino group is shown. " The additive for non-aqueous electrolyte according to claim 1, wherein the compound represented by the formula (1) is a compound represented by the following formula (2).

Wherein (2), X ² represents a group to form a cyclic group together with a sulfur atom, a nitrogen atom and Z, Z represents a sulfonyl group or a carbonyl group, R ¹ is R ¹ as defined in formula (1) It is. ]   A nonaqueous electrolytic solution containing the additive for nonaqueous electrolytic solution according to claim 1, a nonaqueous solvent, and an electrolyte.   The nonaqueous electrolytic solution according to claim 3, wherein the electrolyte contains a lithium salt.   An electrical storage device comprising the nonaqueous electrolytic solution according to claim 3 or 4, and a positive electrode and a negative electrode.   A lithium ion battery comprising the nonaqueous electrolytic solution according to claim 3 or 4, and a positive electrode and a negative electrode.   A lithium ion capacitor comprising the nonaqueous electrolytic solution according to claim 3, and a positive electrode and a negative electrode.

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