JP2005203342A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a lithium secondary battery which has a property of superior energy density and electromotive force or the like and is superior in cycle life and storage stability. <P>SOLUTION: In the secondary battery which comprises a positive electrode, a negative electrode, and an electrolytic solution containing aprotic solvent dissolved with at least an electrolyte, the positive electrode contains a lithium-containing compound oxide having a charge and discharge region of 4.3 or more in a charge and discharge test using metal lithium for the negative electrode, and the electrolytic solution contains a compound as shown in a general formula (1). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a secondary battery, particularly a laminate type secondary battery.

  Non-aqueous electrolyte lithium ion or lithium secondary battery using carbon material or lithium metal for the negative electrode and lithium-containing composite oxide for the positive electrode can realize high energy density, so it can be used as a power source for mobile phones and laptop computers. Attention has been paid. In this secondary battery, it is generally known that a film called a surface film, a protective film, SEI or a film is formed on the surface of the electrode. Since this surface film has a great influence on charge / discharge efficiency, cycle life, and safety, it is known that control of the surface film is indispensable for improving the performance of the electrode. That is, when a carbon material is used as the negative electrode material, it is necessary to reduce the irreversible capacity, and in the lithium metal negative electrode, it is necessary to solve the problem of safety due to the decrease in charge / discharge efficiency and the generation of dendrite.

  Various techniques have been proposed as a technique for solving these problems. For example, when lithium metal is used as the negative electrode material, it has been proposed to suppress the formation of dendrite by providing a coating layer made of lithium fluoride or the like on the surface using a chemical reaction.

Patent Document 1 discloses a technique in which a lithium negative electrode is exposed to an electrolytic solution containing hydrofluoric acid, and the negative electrode is reacted with hydrofluoric acid to cover the surface with a lithium fluoride film. Hydrofluoric acid is produced by the reaction of LiPF ₆ and a small amount of water. On the other hand, a surface film of lithium hydroxide or lithium oxide is formed on the surface of the lithium negative electrode by natural oxidation in air. When these react, a surface film of lithium fluoride is formed on the negative electrode surface. However, this lithium fluoride film is formed by utilizing the reaction between the electrode interface and the liquid, and side reaction components are likely to be mixed into the surface film, and it may be difficult to obtain a uniform film. . Also, there may be cases where the surface film of lithium hydroxide or lithium oxide is not uniformly formed or there is a part where lithium is exposed. In these cases, a uniform thin film cannot be formed. In addition, there has been a safety problem due to the reaction of lithium with water or hydrogen fluoride. Moreover, when reaction is inadequate, unnecessary compound components other than a fluoride remain, and bad influences, such as causing the fall of ion conductivity, are considered. Furthermore, in the method of forming a fluoride layer using such a chemical reaction at the interface, the selection range of available fluorides and electrolytes is limited, and it is difficult to form a stable surface film with a high yield. There was a case.

  In Patent Document 2, a mixed gas of argon and hydrogen fluoride and an aluminum-lithium alloy are reacted to obtain a lithium fluoride surface film on the negative electrode surface. However, when a surface film is preliminarily present on the surface of the lithium metal, particularly when a plurality of types of compounds are present, the reaction tends to be non-uniform and it may be difficult to form a lithium fluoride film uniformly. It was. In this case, it is difficult to obtain a lithium secondary battery having sufficient cycle characteristics.

  Patent Document 3 discloses a technique for forming a surface film structure mainly composed of a substance having a rock salt type crystal structure on the surface of a lithium sheet having a uniform crystal structure, that is, a (100) crystal plane preferentially oriented. It is disclosed. By carrying out like this, it is said that uniform precipitation dissolution reaction, ie, charge / discharge of a battery, can be performed, dendrite precipitation of lithium metal can be suppressed, and the cycle life of the battery can be improved. It is stated that it is preferable to use lithium halide as the material used for the surface film, and it is preferable to use a solid solution of LiF and at least one selected from the group consisting of LiCl, LiBr and LiI. Yes. Specifically, in order to form a solid solution film with LiF and at least one selected from the group consisting of LiCl, LiBr, and LiI, the (100) crystal plane prepared by pressing (rolling) is preferentially oriented. The lithium sheet is selected from the group consisting of (1) to (3) among (1) chlorine molecules or chlorine ions, (2) bromine molecules or bromine ions, and (3) iodine molecules or iodine ions. A negative electrode for a non-aqueous electrolyte battery is produced by immersing in an electrolytic solution containing at least one kind and fluorine molecules or fluorine ions. In the case of this technology, a rolled lithium metal sheet is used, and since the lithium sheet is easily exposed to the atmosphere, a film derived from moisture and the like is easily formed on the surface, and the presence of active sites becomes uneven, which is the purpose. In some cases, it is difficult to produce a stable surface film. In this case, the effect of suppressing dentlite is not always sufficiently obtained.

  In addition, when a carbon material such as graphite or hard carbon capable of occluding and releasing lithium ions is used as the negative electrode, a technique for improving capacity and charge / discharge efficiency has been reported.

  In patent document 4, the negative electrode which coat | covered the carbon material with aluminum is proposed. Thereby, reductive decomposition on the carbon surface of solvent molecules solvated with lithium ions is suppressed, and deterioration of cycle life is suppressed. However, since aluminum reacts with a small amount of water, the capacity may decrease rapidly when the cycle is repeated.

  Patent Document 5 proposes a negative electrode in which a surface of a carbon material is covered with a thin film of a lithium ion conductive solid electrolyte. Thereby, it is said that the decomposition | disassembly of the solvent which arises when using a carbon material can be suppressed, and especially the lithium ion secondary battery which can use a propylene carbonate can be provided. However, cracks generated in the solid electrolyte due to changes in stress during insertion and desorption of lithium ions may lead to deterioration of characteristics. Further, due to non-uniformity such as crystal defects of the solid electrolyte, a uniform reaction cannot be obtained on the negative electrode surface, leading to deterioration of cycle life.

  Further, in Patent Document 6, the negative electrode is made of a material containing graphite, the main component is a cyclic carbonate and a chain carbonate as an electrolytic solution, and 0.1% by mass or more and 4% by mass or less of a cyclic monolith in the electrolytic solution. A secondary battery containing sulfonic acid ester 1,3-propane sultone and / or 1,4-butane sultone is disclosed. Here, 1,3-propane sultone or 1,4-butane sultone contributes to the formation of a passive film on the surface of the carbon material, and the active and highly crystallized carbon material such as natural graphite or artificial graphite is a passive film. It is considered that the coating has an effect of suppressing the decomposition of the electrolyte without impairing the normal reaction of the battery. In addition to the cyclic monosulfonic acid ester, Patent Documents 7 and 8 report that the same effect can be obtained by using a chain disulfonic acid ester. However, the cyclic monosulfonate of Patent Document 6 or the chain disulfonate of Patent Document 7 and Patent Document 8 mainly forms a film on the negative electrode. For example, a film may be formed on the positive electrode. It was sometimes difficult. Non-Patent Documents 1 to 4 disclose a method for producing a chain disulfonate, and Patent Documents 9 and 10 disclose a method for producing a cyclic sulfonate having two sulfonyl groups.

  In Patent Document 11, by adding an aromatic compound to the electrolytic solution solvent, the deterioration of the capacity when the secondary battery is repeatedly charged and discharged over a long period of time is suppressed by preventing oxidation of the electrolytic solution solvent. This is a technique for preventing the decomposition of the solvent by preferentially oxidatively decomposing the aromatic compound. However, when this additive is used, the positive electrode surface is not coated, so that the effect of improving the cycle characteristics may not be sufficient.

  On the other hand, in recent years, with the improvement in performance of portable devices and the like, there has been an increasing demand for improving the characteristics of batteries serving as driving power sources, particularly for increasing energy density. However, in secondary batteries, the energy density obtained with a positive electrode material in practical use is approaching the theoretical limit. Since energy density = potential (V) × Ah (discharge capacity), in order to obtain a required high energy density, for example, it has a high potential (V) as disclosed in Patent Document 12. High voltage positive electrode materials are being considered. These materials have characteristics that are higher in energy density than conventional positive electrode materials, but they have storage characteristics such as low temperature rate characteristics, cycle characteristics, resistance increase and recovery capacity degradation. Had problems.

Patent Document 13 describes a technique for improving cycle characteristics when a high-voltage positive electrode is used by adding a nitrogen-containing unsaturated cyclic compound to an electrolytic solution. However, although the nitrogen-containing unsaturated cyclic compound improves the charge / discharge efficiency of the negative electrode, it does not improve the charge / discharge efficiency of the positive electrode.
JP-A-7-302617 JP-A-8-250108 Japanese Patent Laid-Open No. 11-288706 Japanese Patent Laid-Open No. 5-234583 JP-A-5-275077 JP 2000-3724 A JP 2000-133304 A US Pat. No. 6,436,582 Japanese Patent Publication No. 5-44946 U.S. Pat. No. 4,950,768 JP 2003-7334 A JP 2003-197194 A JP 2003-115324 A J. et al. Am. Pham. Assoc. L26, 485-493, 1937 G. Schroeter, Lieb, Ann, Der Chemie, 418, 161-257, 1919 Biol. Aktiv. Soedin. Pp 64-69 (1968). Armyanskii Kimicheskii Zhurnal, 21, pp 393-396 (1968).

  The above prior art has the following common problems. The surface film formed on the electrode surface is deeply related to charge / discharge efficiency, cycle life, and safety depending on its properties. However, the above-mentioned conventional technology mainly forms a stable film on the negative electrode, and the negative electrode and the positive electrode. A technique for forming a film on both the electrodes has not been disclosed.

  Further, in the conventional technique for forming a film on the positive electrode, there has not yet been a method for controlling the film over a long period of time. For this reason, although a certain degree of suppression effect of dentite can be obtained at the initial use, the surface film may deteriorate and the function as a protective film may be deteriorated if it is used repeatedly. This is because the layer of the positive electrode active material containing lithium changes its volume by occluding and releasing lithium, while the film formed on the surface hardly changes in volume. This is thought to be due to the occurrence of internal stress. Due to the occurrence of such internal stress, it is considered that a part of the surface film is broken and the dendrite suppressing function is lowered. As a result, the electrolytic solution was decomposed, and it was difficult to maintain a high discharge capacity and excellent cycle characteristics.

  In particular, in order to obtain a secondary battery having a high energy density, when charging / discharging is performed using a positive electrode active material having a high operating potential, charging / discharging is performed as compared with a secondary battery using a positive electrode including a conventional positive electrode active material. As a result, the electrolytic solution is actively decomposed, and the storage characteristics such as the discharge capacity and the cycle characteristics, the low temperature characteristics, and the rate characteristics may be significantly reduced. In this case, it is difficult to obtain a high energy density, and as a result, practical application is difficult. It is considered that such decomposition of the electrolytic solution occurs mainly on the positive electrode surface.

  The present invention has been made in view of the problems as described above. A lithium-containing composite oxide having a charge / discharge region of 4.3 or more is used as a positive electrode active material, and the compound represented by the general formula (1) is electrolyzed. When added to the solution, a stable film is formed on the surface of the positive electrode even when charging and discharging are performed at a high potential, and the decomposition of the electrolytic solution is suppressed. As a result, it is an object to obtain a secondary battery that is excellent in cycle characteristics, discharge capacity, and the like and has a high energy density.

In order to solve the above problems, the present invention has the following configuration. That is, the present invention provides a secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution containing an aprotic solvent in which at least an electrolyte is dissolved.
The positive electrode includes a lithium-containing composite oxide having a charge / discharge region of 4.3 V or more in a charge / discharge test using metallic lithium as a positive electrode active material for the negative electrode,
The electrolyte solution includes a compound represented by the following general formula (1).

(However, in the said General formula (1), R < ₁ > and R < ₄ > are respectively independently a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C1-C5. An alkoxy group, a substituted or unsubstituted fluoroalkyl group having 1 to 5 carbon atoms, a polyfluoroalkyl group having 1 to 5 carbon atoms, —SO ₂ X ₁ (wherein X ₁ is a substituted or unsubstituted carbon atom having 1 to 5 carbon atoms). alkyl group), - SY ₁ (Y ₁ is a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), - COZ (Z is a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), And R ₂ and R ₃ each independently represents a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted carbon group having 1 to 5 carbon atoms. Alkoxy group, substituted or absent Substituted phenoxy group, substituted or unsubstituted fluoroalkyl group having 1 to 5 carbon atoms, polyfluoroalkyl group having 1 to 5 carbon atoms, substituted or unsubstituted fluoroalkoxy group having 1 to 5 carbon atoms, 1 to carbon atoms 5 polyfluoroalkoxy group, hydroxyl group, halogen atom, —NX ₂ X ₃ (X ₂ and X ₃ are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), and _{-NY 2 CONY 3 Y 4 (Y} 2 ~Y 4 are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), indicating the atom or a group selected from.)
Furthermore, in the present invention, the lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is preferably LiCoO ₂ .
Furthermore, in the present invention, the lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is LiMO ₂ (M is Ni, Co, Mn, Li, Al, Fe, Ti, Mg, Cu, V, B, A lithium-containing composite oxide represented by (at least three elements selected from the group consisting of Si, Mo, Zn, Sn, In, Nb, and Zr) is preferable.
In the present invention, the lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is preferably Li [Co _1/3 Mn _1/3 Ni _1/3 ] O ₂ .

Further, in the present invention, the lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is Li _a (M _x Mn _{2 -xy} A _y ) O ₄ (where 0.4 <x, 0 <y, x + y <2, 0 <a <1.2 M includes Ni and at least one metal element selected from the group consisting of Co, Fe, Cr, and Cu, and A includes at least one of Si and Ti However, when A contains only Ti, it is preferably 0.1 <y.) A spinel type lithium manganese composite oxide is preferable.

Furthermore, in the present invention, it is preferable that the compound represented by the general formula (1) is contained in the electrolytic solution in an amount of 0.1 to 5.0% by mass with respect to the total mass of the electrolytic solution.
In the present invention, it is preferable that the electrolytic solution further contains a cyclic monosulfonic acid ester represented by the following general formula (2).

(However, in the general formula (2), n is 0 to 2 integer. Also, R ₅ to R ₁₀ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl having 1 to 12 carbon atoms An atom or a group selected from a group, a substituted or unsubstituted fluoroalkyl group having 1 to 6 carbon atoms, and a polyfluoroalkyl group having 1 to 6 carbon atoms.
Furthermore, in the present invention, it is preferable that the electrolytic solution further includes a cyclic sulfonic acid ester having two sulfonyl groups represented by the following general formula (3).

(However, in the said General formula (3), Q is an oxygen atom, a methylene group, or a single bond, A is a substituted or unsubstituted C1-C5 alkylene group, a carbonyl group, a sulfinyl group, C1-C5. At least one C—C bond in the polyfluoroalkylene group, a substituted or unsubstituted fluoroalkylene group having 1 to 5 carbon atoms, or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms is a C—O—C bond A group in which at least one C—C bond in the polyfluoroalkylene group having 1 to 5 carbon atoms is a C—O—C bond, and a substituted or unsubstituted fluoroalkylene having 1 to 5 carbon atoms A group selected from a group in which at least one CC bond in the group is a C—O—C bond, B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, carbon 1-5 polyfluoroalkylene group, and a substituted or unsubstituted group selected from fluoroalkylene group having 1 to 5 carbon atoms.)
In the present invention, it is preferable that the electrolytic solution further contains at least one of vinylene carbonate and a derivative thereof.
Furthermore, in the present invention, it is preferable that the electrolyte contains a lithium salt.
Furthermore the present invention, the lithium _{salt, LiPF 6, LiBF 4, LiAsF} 6, LiSbF 6, LiClO 4, LiAlCl 4 and _{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 are preferably at least one lithium salt selected from the group consisting of:

  Further, in the present invention, the aprotic solvent comprises a cyclic carbonate, a chain carbonate, an aliphatic carboxylic acid ester, a γ-lactone, a cyclic ether, a chain ether, and a fluorinated derivative thereof. It is preferably at least one organic solvent selected from the above.

  Furthermore, the present invention is preferably a secondary battery in which the secondary battery is covered with a laminate outer package.

  In this specification, “polyfluoroalkylene group”, “polyfluoroalkyl group”, and “polyfluoroalkoxy group” are all hydrogen atoms bonded to carbon atoms of the corresponding alkylene group, alkyl group, and alkoxy group, respectively, by fluorine atoms. Represents a substituted group, and “fluoroalkylene group”, “fluoroalkyl group”, and “fluoroalkoxy group” are fluorine atoms in which part of hydrogen atoms bonded to carbon atoms of the corresponding alkylene group, alkyl group, and alkoxy group, respectively. Represents the one substituted by.

In the “substituted fluoroalkylene group”, “substituted fluoroalkyl group” and “substituted fluoroalkoxy group”, “substituted” means that at least one hydrogen atom bonded to a carbon atom is substituted with an atom or functional group other than fluorine. Represents that Examples of the atom or functional group other than fluorine include, for example, a halogen atom such as a chlorine atom, a bromine atom, and an iodine atom, a hydroxyl group, or an alkoxy group having 1 to 5 carbon atoms, or a group in which this is substituted with a halogen atom or a hydroxyl group. Or a group in which —SO ₂ — is introduced into these groups (for example, —OSO ₂ CH ₂ SO ₂ Cl). When this functional group contains a carbon atom, this carbon atom is not included in the number of “C1-5” in the description of “substituted or unsubstituted alkyl group having 1 to 5 carbon atoms” and the like. And

  According to the present invention, an electrolytic solution for a secondary battery containing a lithium-containing composite oxide having a charge / discharge region of 4.3 or more in a charge / discharge test using metallic lithium as a negative electrode and containing a chain disulfone compound is provided. By using it, it is possible to obtain an excellent lithium secondary battery having a high energy density, excellent charge / discharge efficiency, good cycle characteristics, a high capacity retention rate, and capable of suppressing an increase in resistance during storage.

(Description of battery configuration according to the present invention)
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 capable of inserting and extracting lithium ions, a layer 13 containing a negative electrode active material capable of inserting and extracting lithium ions, a negative electrode current collector 14 and electrolysis It is comprised from the liquid 15 and the separator 16 containing this.

(Current collector)
Aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used as the positive electrode current collector 11, and copper, stainless steel, nickel, titanium, or an alloy thereof can be used as the negative electrode current collector 14. .

(Separator)
As the separator 16, a polyolefin such as polypropylene or polyethylene, or a porous film such as a fluororesin is preferably used.

(Negative electrode)
The negative electrode active material is made of a material that can occlude and release lithium, such as lithium metal or carbon material. As the carbon material, graphite that occludes lithium, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, carbon nanohorn, or a composite thereof can be used. When lithium metal is used as the negative electrode active material, 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. Thus, the layer 13 to be the negative electrode can be obtained. In the case of carbon materials, carbon and a binder such as polyvinylidene fluoride (PVDF) are mixed, dispersed and kneaded in a solvent such as NMP, and this is applied onto a substrate such as copper foil. The layer 13 which becomes a negative electrode can be obtained by the method such as the vapor deposition method, the CVD method or the sputtering method.

(Positive electrode)
The positive electrode active material is a high-voltage positive electrode material, that is, a lithium-containing composite oxide having a charge / discharge region of 4.3 V or higher in a charge / discharge test using metallic lithium as a negative electrode. Here, the meaning of having a charge / discharge region at 4.3 V or higher in a charge / discharge test of a lithium secondary battery will be described with reference to FIG. FIG. 2 shows that the lithium composite oxide of the present invention is used as a positive electrode active material, metallic lithium as a negative electrode, and an electrolytic solution containing 1M LiPF ₆ as an electrolyte, EC / DEC = 30/70 (volume ratio), charging current rate 1 / 40C. It shows an example of the charge / discharge test performed in 1. In the present invention, “having a charge / discharge region at 4.3 V or higher” means that when such a charge / discharge test is performed, charge / discharge can be performed stably as shown in FIG. 2 (charge / discharge). This means that the voltage (which does not cause a sudden voltage rise or the like in the curve) exists at 4.3 V or higher.

  In addition, as a positive electrode active material of this invention, it is more preferable to use what has a charging / discharging area | region to 4.5V or more, What has a charging / discharging area | region to 5.0V or more is still more preferable, and it charges to 5.5V or more. Those having a discharge region are particularly preferred. By using these positive electrode active materials, a secondary battery having a higher energy density can be obtained.

Specifically, as the positive electrode active material of the present invention, LiCoO ₂ , LiMO ₂ (M is Ni, Co, Mn, Li, Al, Fe, Ti, Mg, Cu, V, B, Si, Mo, Zn, Sn). , In, Nb and Zr) are preferred. By using these positive electrode active materials in combination with the compound represented by the general formula (1), a stable film can be formed on the surface of the positive electrode, the decomposition of the solvent component is suppressed, and high cycle characteristics and discharge capacity are obtained. A secondary battery can be obtained.

It is more preferable to use Li [Co _1/3 Mn _1/3 Ni _1/3 ] O ₂ as the positive electrode active material. By using Li [Co _1/3 Mn _1/3 Ni _1/3 ] O ₂ , a more stable film can be formed on the surface of the positive electrode, and good storage characteristics and cycle characteristics can be exhibited.

In addition, Li _a (M _x Mn _{2 -xy} A _y ) O ₄ (wherein 0.4 <x, 0 <y, x + y <2, 0 <a <1.2) is used as the positive electrode active material of the present invention. M includes Ni and at least one metal element selected from the group consisting of Co, Fe, Cr and Cu, A includes at least one metal element of Si and Ti, provided that A includes only Ti. In the case of inclusion, it is preferable to use a spinel type lithium manganese oxide represented by 0.1 <y.) High capacity characteristics and film formation effect can be obtained.

  The selected positive electrode active material is 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). The layer 12 which becomes a positive electrode can be obtained by a method such as coating on a substrate such as an aluminum foil.

(Electrolyte)
The electrolytic solution 15 includes at least an electrolyte, an aprotic solvent, and an additive.

(Electrolytes)
As the electrolyte, in the case of a lithium secondary battery, a lithium salt is used and dissolved in an aprotic solvent. The lithium salt, lithium imide _{salt, LiPF 6, LiAsF 6, LiAlCl} 4, LiClO 4, LiBF 4, LiSbF 6 , and the like. Of these, LiPF ₆ and LiBF ₄ are particularly preferable. LiN The lithium imide salt _{(C k F 2k + 1 SO} 2) (C m F 2m + 1 SO 2) (k, m are each independently 1 or 2). These can be used alone or in combination of two or more. By including these lithium salts, a high energy density can be achieved.

(Aprotic solvent)
The aprotic electrolyte is selected from organic solvents such as cyclic carbonates, chain carbonates, aliphatic carboxylic acid esters, γ-lactones, cyclic ethers, chain ethers and their fluorinated derivatives. At least one organic solvent is used. More specifically,
Cyclic carbonates: propylene carbonate (hereinafter abbreviated as PC), ethylene carbonate (hereinafter abbreviated as EC), butylene carbonate (BC), and their derivative chain carbonates: dimethyl carbonate (DMC), diethyl carbonate ( Hereinafter, abbreviated as DEC.), Ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and their derivatives aliphatic carboxylic acid esters: methyl formate, methyl acetate, ethyl propionate, and their derivatives γ-lactone Class: γ-butyrolactone and derivatives thereof Cyclic ethers: Tetrahydrofuran, 2-methyltetrahydrofuran, and derivatives thereof Chain ethers: 1,2-diethoxyethane (DEE), ethoxymethoxyethane (EME), Diethyl ether, and derivatives thereof, etc .: dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, acetonitrile, propionitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, methyl Sulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, anisole, N-methylpyrrolidone, fluorinated carboxylic acid ester These may be used alone or in combination of two or more. .

(Additive)
As the additive, a chain disulfonic acid ester represented by the general formula (1) is used.

(However, in the said General formula (1), R < ₁ > and R < ₄ > are respectively independently a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C1-C5. An alkoxy group, a substituted or unsubstituted fluoroalkyl group having 1 to 5 carbon atoms, a polyfluoroalkyl group having 1 to 5 carbon atoms, —SO ₂ X ₁ (wherein X ₁ is a substituted or unsubstituted carbon atom having 1 to 5 carbon atoms). alkyl group), - SY ₁ (Y ₁ is a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), - COZ (Z is a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), And R ₂ and R ₃ each independently represents a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted carbon group having 1 to 5 carbon atoms. Alkoxy group, substituted or absent Substituted phenoxy group, substituted or unsubstituted fluoroalkyl group having 1 to 5 carbon atoms, polyfluoroalkyl group having 1 to 5 carbon atoms, substituted or unsubstituted fluoroalkoxy group having 1 to 5 carbon atoms, 1 to carbon atoms 5 polyfluoroalkoxy group, hydroxyl group, halogen atom, —NX ₂ X ₃ (X ₂ and X ₃ are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), and _{-NY 2 CONY 3 Y 4 (Y} 2 ~Y 4 are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), indicating the atom or a group selected from.)
The compound represented by the general formula (1) is an acyclic compound and does not involve a cyclization reaction during synthesis, and can be synthesized using, for example, Non-Patent Documents 1 to 4. Moreover, it can also be obtained as a by-product of the synthesis of a cyclic sulfonic acid ester having two sulfonyl groups shown in Patent Document 9. Thus, the compound represented by the general formula (1) has an advantage that an inexpensive electrolytic solution can be provided because the synthesis process is easy.

Preferred molecular structures of R ₁ and R _{4 in} the general formula (1) include ease of forming a reactive film on the electrode, stability of the compound, ease of handling, solubility in a solvent, From the viewpoint of ease of synthesis, cost, etc., each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a halogen atom, and —SO ₂ X ₁ (X ₁ is a substituted or unsubstituted carbon atom having 1 to Atoms or groups selected from (5 alkyl groups), each independently preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 5 carbon atoms, more preferably a hydrogen atom or a methyl group. Particularly preferred embodiments of R ₁ and R ₄ is where R ₁ and R ₄ is a hydrogen atom. This is because when R ₁ and R ₄ are hydrogen atoms, the methylene moiety sandwiched between the two sulfonyl groups is activated and a reaction film on the electrode is easily formed.

In addition, in R ₂ and R ₃ , from the viewpoints of stability of the compound, ease of synthesis of the compound, solubility in a solvent, price, and the like, each independently substituted or unsubstituted alkyl having 1 to 5 carbon atoms A group, a substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms, a substituted or unsubstituted phenoxy group, a hydroxyl group, a halogen atom, and —NX ₂ X ₃ (X ₂ and X ₃ are each independently a hydrogen atom; Or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms) is preferable, and each independently is a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, or substituted or unsubstituted. The alkoxy group having 1 to 5 carbon atoms is more preferable, and one or both of R ₂ and R ₃ are more preferably substituted or unsubstituted alkoxy groups having 1 to 5 carbon atoms. For the same reason, the substituted or unsubstituted alkyl group having 1 to 5 carbon atoms is preferably a methyl group or ethyl group, and the substituted or unsubstituted alkoxy group having 1 to 5 carbon atoms is a methoxy group or An ethoxy group is preferable.

  The compound of the general formula (1) has two sulfonyl groups, has a small LUMO, and has a smaller LUMO value than solvent molecules and monosulfonic acid esters in the electrolytic solution, and thus is easily reduced. For example, Compound No. 1 shown in Table 1 below. The LUMO of 1 is as small as -0.86 eV according to semiempirical molecular orbital calculation. For this reason, compound No. 1 is preceded by a solvent (LUMO: about 1.2 eV) comprising a cyclic carbonate or a chain carbonate. It is considered that 1 reduction film is formed on the negative electrode and plays a role in suppressing decomposition of solvent molecules. In order to suppress the decomposition of the solvent molecules, it is difficult to form a highly resistant solvent molecule decomposition film on the negative electrode, so that an increase in resistance and an improvement in cycle characteristics can be expected. Moreover, it is considered that two electron-withdrawing sulfonyl groups are bonded to the carbon atom, and a film is easily formed on the electrode by the activation of the carbon atom. Furthermore, it is considered that the carbanion produced by deprotonation of active methylene coordinates Li or reacts on the positive electrode to form a film.

  In particular, when the positive electrode material that can be used at the above-mentioned high potential is used and the compound represented by the general formula (1) is added to the electrolytic solution, a film is formed on the surface of the positive electrode, and the decomposition of the electrolytic solution is suppressed. It is thought that the increase in resistance is suppressed to inhibit deposition. As a result, a secondary battery having excellent discharge capacity and cycle characteristics and a high energy density can be obtained. Further, since the increase in internal impedance at the end of discharge is suppressed by the above-mentioned film, it is considered to be effective for improving cycle characteristics particularly in a high-capacity positive electrode material.

  Although the specific example of General formula (1) is shown below, this invention is not specifically limited to these.

  Although the compound represented by General formula (1) is not specifically limited, It is preferable that 0.1 to 5.0 mass% is contained in electrolyte solution. If it is less than 0.1% by mass, a sufficient effect may not be exhibited in forming a film by an electrochemical reaction on the electrode surface. Moreover, when it exceeds 5.0 mass%, it not only becomes difficult to melt | dissolve, but the viscosity of electrolyte solution may be enlarged. In the present invention, more preferably, a sufficient film effect can be obtained by adding in the range of 0.5% by mass to 3.0% by mass.

You may use the compound shown in General formula (1) individually or in combination of 2 or more types. When two or more types are used in combination, there is no particular limitation, but at least one of them contains a compound having an active methylene group (that is, a compound in which R ₁ and R ₄ are hydrogen) from the viewpoint of easy film formation with an electrode. Is effective. As a specific combination, the above-mentioned compound no. 1 (compound having an active methylene group) and compound no. 5 compounds.

  When two or more types of the compound of the general formula (1) are added to the electrolytic solution, the proportion of the electrolytic solution in the electrolytic solution is not particularly limited, but for the same reason as described above, the two types are combined to be 0.1% by mass or more and 5.0% by mass The following is preferred. Further, when two or more kinds of the compound of the general formula (1) are added, the ratio of each compound to the total mass of the compound of the general formula (1) is not particularly limited, but the ratio of the smallest compound is 5 It is preferable that the ratio of the compound with the most mass% is 95 mass%.

  Further, the electrolyte solution containing the compound of the general formula (1) contains at least one of a cyclic monosulfonic acid ester, a cyclic sulfonic acid ester having two sulfonyl groups, an alkanesulfonic acid anhydride, and a sulfolene compound. This is also effective here using an electrolyte solution.

  Examples of the cyclic monosulfonic acid ester include compounds represented by the following general formula (2).

(However, in the general formula (2), n is 0 to 2 integer. Also, R ₅ to R ₁₀ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl having 1 to 12 carbon atoms An atom or a group selected from a group, a substituted or unsubstituted fluoroalkyl group having 1 to 6 carbon atoms, and a polyfluoroalkyl group having 1 to 6 carbon atoms.
In the compound represented by the general formula (2), n is preferably 0 or 1 from the viewpoints of stability of the compound, ease of synthesis of the compound, solubility in a solvent, price, and the like, and R _{5 to} R ₁₀ Are preferably each independently an atom or group selected from a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, and a polyfluoroalkyl group having 1 to 5 carbon atoms. A hydrogen atom or a polyfluoroalkyl group having 1 to 5 carbon atoms is more preferable. More preferably, all of R _{5 to} R ₁₀ are hydrogen atoms, or one or two of R _{5 to} R ₁₀ are polyfluoroalkyl groups having 1 to 5 carbon atoms, and the other is a hydrogen atom. As said C1-C5 polyfluoroalkyl group, a trifluoromethyl group is preferable.

  Specifically, 1,3-propane sultone (1,3-PS), α-trifluoromethyl-γ-sultone, β-trifluoromethyl-γ-sultone, γ-trifluoromethyl-γ-sultone, α -Methyl-γ-sultone, α, β-di (trifluoromethyl) -γ-sultone, α, α-di (trifluoromethyl) -γ-sultone, α-undecafluoropentyl-γ-sultone, α- Examples include heptafluoropropyl-γ-sultone and 1,4-butane sultone (1,4-BS).

  Among these, 1,3-propane sultone (1,3-PS) is considered to form a decomposition film on the negative electrode of a lithium ion secondary battery. 1,3-PS has a LUMO of 0.07 eV. It is larger than that of 1 (−0.86 eV). For example, compound no. When 1 and 1,3-PS were added to the electrolyte and charged, compound No. 1 was first prepared. One substance may form a film on the negative electrode, and then 1,3-PS forms a film. At the initial stage of charging, a portion having a negative electrode surface and compound No. 1 reacts mainly, but compound no. 1 progresses to charge at the part that did not react with 1 (the part that may react with the solvent molecule) and reacts with 1,3-PS. A composite film of 1 and 1,3-PS is formed, and a further resistance increase suppressing effect, battery swelling expansion, and the like can be expected.

  When the compound of the general formula (2) is added to the electrolytic solution, the content in the electrolytic solution is not particularly limited, but 0.5% by mass to 10.0% by mass is contained in the electrolytic solution. Is preferred. If the amount is less than 0.5% by mass, the effect may not be sufficiently exerted on the film formation by the electrochemical reaction on the electrode surface. If it exceeds 10.0 mass%, the viscosity of the electrolytic solution may be increased. Moreover, as a ratio of the general formula (2) in the compound of the general formula (1) and the general formula (2), the total mass of the compound of the general formula (1) and the compound of the general formula (2), respectively. 10 to 90% by mass is preferable.

  Examples of the cyclic sulfonic acid ester having two sulfonyl groups include compounds represented by the following general formula (3).

(However, in the said General formula (3), Q is an oxygen atom, a methylene group, or a single bond, A is a substituted or unsubstituted C1-C5 alkylene group, a carbonyl group, a sulfinyl group, C1-C5. At least one C—C bond in the polyfluoroalkylene group, a substituted or unsubstituted fluoroalkylene group having 1 to 5 carbon atoms, or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms is a C—O—C bond A group in which at least one C—C bond in the polyfluoroalkylene group having 1 to 5 carbon atoms is a C—O—C bond, and a substituted or unsubstituted fluoroalkylene having 1 to 5 carbon atoms A group selected from a group in which at least one CC bond in the group is a C—O—C bond, B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, carbon 1-5 polyfluoroalkylene group, and a substituted or unsubstituted group selected from fluoroalkylene group having 1 to 5 carbon atoms.)
In the compound represented by the general formula (3), A is a substituted or unsubstituted carbon number of 1 to 5 from the viewpoints of stability of the compound, ease of synthesis of the compound, solubility in a solvent, price, and the like. At least a C-C bond in the alkylene group, a polyfluoroalkylene group having 1 to 5 carbon atoms, a substituted or unsubstituted fluoroalkylene group having 1 to 5 carbon atoms, and a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms. A group in which one site is a C—O—C bond, a group in which at least one C—C bond in a C 1-5 polyfluoroalkylene group is a C—O—C bond, and a substituted or unsubstituted group A group selected from a group in which at least one C—C bond in the fluoroalkylene group having 1 to 5 carbon atoms is a C—O—C bond is preferable. A group selected from a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, a polyfluoroalkylene group having 1 to 5 carbon atoms, and a substituted or unsubstituted fluoroalkylene group having 1 to 5 carbon atoms is more preferable. Alternatively, an unsubstituted alkylene group having 1 to 5 carbon atoms is more preferable, and a methylene group, an ethylene group, or a 2,2-propanediyl group is particularly preferable. The C1-C5 fluoroalkylene group preferably includes a methylene group and a difluoromethylene group, and more preferably includes a methylene group and a difluoromethylene group.

For the same reason, B is preferably an alkylene group having 1 to 5 carbon atoms, more preferably a methylene group, a 1,1-ethanediyl group, or a 2,2-propanediyl group.
The cyclic sulfonic acid ester having two of these sulfonyl groups is disclosed in Patent Document 10. Specific compounds represented by the general formula (3) are listed below, but are not limited thereto.

  These compounds have the same level of LUMO as the compound of the general formula (1) of the present invention and have two or more sulfonyl groups. 1 and compound no. When 21 (MMDS) is added to the electrolyte, a high ion conductive composite film is easily formed in the initial stage of charging. MMDS is considered to be a compound that easily forms a film by reacting with the negative electrode by ring opening.

  If MMDS contributes to the film formation fairly selectively on the negative electrode, compound no. In the case of the first material, the film formation probability on the negative electrode is decreased, the reaction probability on the positive electrode is increased, and the film formation on the positive electrode is achieved. As a result, suppression of solvent decomposition on the positive electrode can be expected.

  When the compound of the general formula (3) is added to the electrolytic solution, the content of the compound of the general formula (3) in the electrolytic solution is not particularly limited, but 0.5% by mass or more and 10. It is preferably contained in an amount of 0% by mass or less. If the amount is less than 0.5% by mass, the effect may not be sufficiently exerted on the film formation by the electrochemical reaction on the electrode surface. If it exceeds 10.0 mass%, the viscosity of the electrolytic solution may be increased. As a ratio of the compound of general formula (3) in general formula (1) and general formula (3), 10-90 mass% of the total mass of the compound of general formula (1) and general formula (3) is preferable. . Moreover, when using the compound of General formula (2) in addition to this, 10-90 mass% of the total mass of the compound of General formula (1), General formula (2), and General formula (3) is preferable.

  In the present invention, in some cases, at least one of vinylene carbonate (VC) and a derivative thereof can be added to the electrolytic solution. By adding at least one of vinylene carbonate (VC) and its derivatives, the cycle characteristics can be further improved. The LUMO of VC is 0.09 eV, which is less susceptible to the reduction reaction than the compound of the general formula (1), and is considered to exist in the electrolyte for a long time without being consumed by receiving the reduction reaction in the initial charge / discharge. Therefore, it is possible to contribute to the improvement of cycle characteristics by being gradually consumed during the charge / discharge cycle. When at least one of the vinylene carbonate and derivatives thereof is used as an additive for an electrolytic solution, the effect can be obtained by including 0.05% by mass to 3.0% by mass in the electrolytic solution.

  When the compound of the general formula (1) and VC, the compound of the general formula (1) and other additives, and VC are further added to the electrolytic solution, the proportion of VC in the whole electrolytic solution is not particularly limited. Is preferably 0.5% by mass to 10.0% by mass. If the amount is less than 0.5% by mass, the effect may not be sufficiently exerted on the film formation by the electrochemical reaction on the electrode surface. If it exceeds 10.0 mass%, the viscosity of the electrolytic solution may be increased.

  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. By appropriately adding other additive materials (cyclic monosulfonic acid ester, cyclic sulfonic acid ester having two sulfonyl groups, sulfolane, alkanesulfonic acid anhydride, sulfolene compound or vinylene carbonate compound) to this electrolytic solution, The electrolyte solution can be obtained.

  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. Among them, the laminate type has a shape sealed by an exterior body made of a flexible film made of a laminate of a synthetic resin and a metal foil, and is a battery can such as a cylindrical type, a square type, or a coin type. It is more susceptible to an increase in internal pressure than that enclosed in an outer package, and therefore control of the chemical reaction between the electrode and the interface between the electrolytic solution is more important. In the case of a secondary battery containing a chain disulfonic acid compound represented by the general formula (1) according to the present invention, even in a laminate type battery, resistance increase is suppressed and battery swelling (gas generation and internal pressure Rise) can be suppressed. Therefore, safety and long-term reliability can be ensured even in a large-sized lithium ion secondary battery such as an automobile.

  In the lithium secondary battery according to the present invention, the negative electrode 13 and the positive electrode 12 are laminated via the separator 16 in a dry air or an inert gas atmosphere, or the laminated one is wound, and then inserted into the outer package. It is obtained by impregnating an electrolytic solution containing a compound represented by the formula (1) and then sealing the battery outer package. The effect of the present invention can be obtained by forming the film on the electrode by charging the battery before or after sealing.

(Production of battery)
A positive electrode active material and a conductivity-imparting agent described in Tables 1 to 4 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 (20 μm for a cylindrical type, 25 μm for a laminate type) serving as a positive electrode current collector, and then NMP was evaporated to obtain a positive electrode sheet. The solid content ratio in the positive electrode was positive electrode active material: conductivity imparting agent: PVDF = 80: 10: 10 (mass%).

  On the other hand, the negative electrode active material was mixed so as to have a ratio of carbon: PVDF = 90: 10 (mass%) and dispersed in NMP, and a copper foil (10 μm in the case of a cylindrical type, laminated type) serving as the negative electrode current collector 14 In this case, it was prepared by coating on 20 μm).

The electrolyte solution 15 was prepared by dissolving the solvents described in Tables 1 to 4, 1 mol / L LiPF ₆ as the electrolyte, and the additives described in Tables 1 to 4.

  Then, a negative electrode and a positive electrode are laminated via a separator 16 made of polyethylene, and an aluminum laminated film type secondary battery (Examples 1 to 26, Comparative Examples 1 to 3) and a cylindrical secondary battery (Examples 27 to 34). Comparative Examples 4 and 5) were produced. When a laminate type battery is used, the laminate film used has a structure in which a polypropylene resin (sealing layer, thickness 70 μm), polyethylene terephthalate (20 μm), aluminum (50 μm), and polyethylene terephthalate (20 μm) are laminated in this order. Two pieces of this are cut into a predetermined size, and a concave portion having a bottom surface portion and a side surface portion that match the size of the multilayer electrode body is formed in a part thereof, and these are opposed to wrap the multilayer electrode body. Then, the periphery was thermally fused to produce a film-clad battery. Before the last side was heat-sealed and sealed, the electrolyte solution was impregnated with the laminated electrode body.

(Charge / discharge cycle test)
When amorphous carbon is used as the negative electrode active material and Li [Ni _0.5 Mn _1.37 Ti _0.13 O ₄ ] is used as the positive electrode active material, the charge end voltage is 4.75 V at a charge rate of 1 C and a discharge rate of 1 C. The final voltage was 2.5V. Further, when amorphous carbon is used as the negative electrode active material and a material other than Li [Co _0.5 Mn _1.37 Ti _0.13 O ₄ ] is used as the positive electrode active material, a charge termination voltage of 4C is obtained at a charge rate of 1C and a discharge rate of 1C. The discharge end voltage was 4V and 4V. These positive electrode capacity retention rates (%) are values obtained by dividing the discharge capacity (mAh) after 500 cycles by the discharge capacity (mAh) at the 10th cycle.

(Storage characteristics test)
Ratio of increase in resistance after storage for 60 days at a discharge depth of 50% (45 ° C.) (the ratio of the resistance value after storage when the initial resistance value (at the start of storage) is 1, the charge / discharge condition is Li [Ni _The storage characteristics were measured by the same conditions as in the charge / discharge cycle test using a positive electrode active material other than _0.5 Mn _1.37 Ti _0.13 O ₄ ] or Li [Co _0.5 Mn _1.37 Ti _0.13 O ₄ ].

  In Tables 1 to 4, “No.” in the column “Type and composition of additives in electrolyte solution” is compound No. Represents.

When the upper limit of the potential at which charging and discharging can be performed stably in the charge and discharge test using the metal lithium of the positive electrode active material used in Tables 1 to 4 as a negative electrode (measured by the method of FIG. 2), Li [Co _1/3 Mn _1/3 Ni _1/3 ] O ₂ : 4.6V, Li [Co _0.2 Mn _0.4 Ni _0.4 ] O ₂ : 4.6V, Li [Al _0.1 Mn _0.4 Ni _0.5 ] O ₂ : 4.7V _{, Li [Fe 0.1 Mn 0.4 Ni} 0.5] O 2: 4.5, Li [Ti 0.1 Mn 0.4 Ni 0.5] O 2: 4.6V, Li [Mg 0.1 Mn 0.4 Ni 0.5] O 2: 4.5V, Li [Ni _0.5 Mn _1.37 Ti _0.13 ] O ₄ : 4.9 V, Li [Co _0.5 Mn _1.37 Ti _0.13 ] O ₄ : 5.2 V, LiCoO ₂ : 4.5 V.

  Moreover, the result obtained by the cycle test and the storage test is shown in Tables 5 to 8 below. The resistance increase rate in the storage characteristics is a relative value when the initial value is 1.

(Evaluation of capacity recovery rate and cell volume change)
Using an aluminum laminate film type battery, at room temperature (25 ° C), with a constant current and voltage of 2A, charge for 5 hours to a final voltage of 4.5V, and then discharge to a final voltage of 2.5V with a constant current of 2A. Then, the generated gas was removed and the volume of the battery at this time was measured. After degassing, the mixture was left for one week, and then charged and discharged once again at room temperature. The charging current and discharging current at this time are constant (2A), and the discharging capacity at this time is defined as the initial capacity. The discharge-side cut-off potential was 2.5 V, and the charge-side cut-off potential was 4.4 V. Then, after charging for 2.5 hours to 4.4 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 84 days. After being left standing, the discharge operation was performed again at a constant current at room temperature. Subsequently, the same constant current was charged and discharged again, and the discharge capacity at this time was defined as a recovery capacity. Here, (capacity recovery rate) = (recovery capacity) / (initial capacity). At the same time, the volume of the battery was measured, and the difference from the volume immediately after degassing was taken as the cell volume change amount.

(Effect of compound addition of general formula (1))
First, the effect of the addition of the compound of the general formula (1) was verified for the laminate type battery (Examples 1 to 10, Comparative Examples 1 to 3). The resistance increase rate, the capacity recovery rate, and the capacity retention rate after 500 cycles in Examples 1 to 10 are greatly improved as compared with Comparative Examples 1 to 3 in which the compound of general formula (1) was not added. These results show that by adding the compound represented by the general formula (1) to the electrolytic solution, a film having high ionic conductivity and high stability during storage compared to the additive-free system and the conventional additive system. This is thought to be because of the formation. Furthermore, the irreversible reaction is suppressed by the stabilization of the surface film present at the interface between the positive electrode / negative electrode surface and the electrolyte and the high ionic conductivity of the film, and therefore, it is considered that the deterioration under high voltage is suppressed.

  Moreover, about the volume variation | change_quantity of the laminate exterior cell after a preservation | save, the volume variation | change_quantity of the cell of the present Examples 1-10 is small with respect to Comparative Examples 1-3. This is presumably because the film of the compound (1) was formed on the electrode, and gas generation due to decomposition of the electrolytic solution could be suppressed.

Further, regarding the battery shown in Example 1, the positive electrode surface and the negative electrode surface after the cycle were examined using X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray analysis (EDX), and the presence of LiF and LiCO ₃ was found. It has been shown. Further, as a result of performing peak splitting of the sulfur spectrum by XPS analysis, it was confirmed that a substance having a peak in the vicinity of 164 eV was present. There is no substance having a peak in the vicinity of 164 eV in the system containing no additive or the system using other additives. It is considered that a unique film was formed by adding 1.

  Similarly, the effect of adding the compound of the general formula (1) was verified for the cylindrical battery (Examples 27 and 28, Comparative Examples 4 and 5). ) Was improved as compared with additive-free Comparative Examples 4 and 5. This is presumably because a film was stably formed on the electrode surface for the same reason as in the laminate type battery.

(Effect of adding cyclic monosulfonic acid ester)
About the laminate type battery, the capacity retention rate and storage characteristics (resistance increase rate, capacity recovery rate) in Examples 11 to 13 were improved. This is probably because the addition of 1,3-PS suppressed the irreversible reaction due to the stabilization of the film present at the interface between the electrode surface and the electrolyte and the high ionic conductivity of the film. The cell volume change amount is smaller than those of Comparative Examples 1 to 3 and Examples 1, 8, and 10. This is presumably because a film was formed on the negative electrode due to the combined effect of the compound of general formula (1) and 1,3-PS, and gas generation due to decomposition of the electrolytic solution could be greatly suppressed.

  Similarly, for the cylindrical battery, the capacity retention rate and the resistance increase rate after the cycle test in Examples 29 and 30 are higher than those in Examples 27 and 28, respectively. This is considered to be due to the same reason as the laminate type battery.

(Effect of VC addition)
Regarding the laminated batteries, the cells in Examples 14 to 16 are further improved in capacity retention rate and storage characteristics (resistance increase rate, capacity recovery rate, cell volume change amount) compared to Examples 11 to 13. . These results are obtained by adding the compound represented by the general formula (1) of the present invention, the cyclic monosulfonic acid ester, and vinylene carbonate to the electrolyte solution, so that ions can be added compared to the additive-free system and the conventional additive system. This is probably because a film having high conductivity and high stability during storage and charge / discharge cycles was formed.

  Similarly, regarding the cylindrical battery, the batteries shown in Examples 31 and 32 have a further improved capacity retention ratio after the cycle test as compared with Examples 29 and 30, that is, the general formula (1). It was confirmed that the cycle characteristics were improved by further adding VC to the electrolytic solution containing the compound represented by the formula (1) and the cyclic monosulfonic acid ester.

(Effect of adding cyclic disulfonic acid ester (cyclic sulfonic acid ester having two sulfonyl groups))
Regarding the laminate type batteries, the capacity retention ratio and storage characteristics (resistance increase rate, capacity recovery rate) in Examples 17 to 19 are further improved as compared with Examples 1 to 10. These results are obtained by adding the compound represented by the general formula (1) of the present invention and a cyclic sulfonic acid ester having two sulfonyl groups to the electrolytic solution, and comparing it with an additive-free system or a conventional additive system. This is probably because a film having high ionic conductivity and high stability during storage was formed.

  Moreover, the volume change amount of the cell in Examples 17-19 is small with respect to Comparative Examples 1-3 and Examples 1-10. This is compound no. This is probably because a film was formed on the negative electrode due to the combined effect of Compound 1 and MMDS, and gas generation due to decomposition of the electrolytic solution could be greatly suppressed.

  Similarly, for the cylindrical batteries, the batteries shown in Examples 33 and 34 have a further improved capacity retention ratio after the cycle test as compared with Examples 27 and 28, that is, the general formula (1). It was confirmed that the cycle characteristics were improved by including the compound represented by the general formula (3) in the electrolyte solution containing the compound represented by formula (3).

(Effect of change in concentration of compound of general formula (1) in electrolyte)
In Examples 20 to 26, Compound No. The concentration of the additive 1 in the electrolyte solution was changed, and a laminate type secondary battery similar to that in Example 1 was prepared and evaluated. The capacity retention after 500 cycles decreased at concentrations of less than 0.1% by mass and greater than 5.0% by mass. It was also found that the resistance increase rate after storage for 60 days was extremely large at concentrations of less than 0.1% by mass and more than 5.0% by mass. From this result, the concentration in the electrolytic solution of the general formula (1) is preferably 0.1% by mass or more and 5.0% by mass or less, and a particularly preferable concentration range is 0.5% by mass or more and 3.0% by mass or less. It was confirmed.

It is a schematic block diagram of the secondary battery which concerns on this invention. It is a figure explaining the charging / discharging curve using the positive electrode active material of 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 (13)

In a secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution containing at least an aprotic solvent in which an electrolyte is dissolved,
The positive electrode includes a lithium-containing composite oxide having a charge / discharge region of 4.3 V or more in a charge / discharge test using metallic lithium as a positive electrode active material for the negative electrode,
The secondary battery, wherein the electrolytic solution includes a compound represented by the following general formula (1).

(However, in the said General formula (1), R < ₁ > and R < ₄ > are respectively independently a hydrogen atom, a substituted or unsubstituted C1-C5 alkyl group, a substituted or unsubstituted C1-C5. An alkoxy group, a substituted or unsubstituted fluoroalkyl group having 1 to 5 carbon atoms, a polyfluoroalkyl group having 1 to 5 carbon atoms, —SO ₂ X ₁ (wherein X ₁ is a substituted or unsubstituted carbon atom having 1 to 5 carbon atoms). alkyl group), - SY ₁ (Y ₁ is a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), - COZ (Z is a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), And R ₂ and R ₃ each independently represents a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, a substituted or unsubstituted carbon group having 1 to 5 carbon atoms. Alkoxy group, substituted or absent Substituted phenoxy group, substituted or unsubstituted fluoroalkyl group having 1 to 5 carbon atoms, polyfluoroalkyl group having 1 to 5 carbon atoms, substituted or unsubstituted fluoroalkoxy group having 1 to 5 carbon atoms, 1 to carbon atoms 5 polyfluoroalkoxy group, hydroxyl group, halogen atom, —NX ₂ X ₃ (X ₂ and X ₃ are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), and _{-NY 2 CONY 3 Y 4 (Y} 2 ~Y 4 are each independently a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms), indicating the atom or a group selected from.) The secondary battery according to claim 1, wherein the lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is LiCoO ₂ . The lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is LiMO ₂ (M is Ni, Co, Mn, Li, Al, Fe, Ti, Mg, Cu, V, B, Si, Mo, Zn). 2. The secondary battery according to claim 1, wherein the secondary battery is a lithium-containing composite oxide represented by at least three elements selected from the group consisting of Sn, In, Nb, and Zr. 4. The secondary according to claim 3, wherein the lithium-containing composite oxide having a charge / discharge region at 4.3 V or more is Li [Co _1/3 Mn _1/3 Ni _1/3 ] O _2. battery. The lithium-containing composite oxide having a charge / discharge region at 4.3 V or higher is Li _a (M _x Mn _{2 -xyA y} ) O ₄ (where 0.4 <x, 0 <y, x + y <2, 0 <A <1.2 M includes Ni and at least one metal element selected from the group consisting of Co, Fe, Cr and Cu, and A includes at least one metal element of Si and Ti. However, when A contains only Ti, 0.1 <y.) The secondary battery according to claim 1, wherein the secondary battery is a spinel-type lithium-manganese composite oxide.   The compound represented by the general formula (1) is contained in the electrolytic solution in an amount of 0.1 to 5.0% by mass with respect to the total mass of the electrolytic solution. Secondary battery described in 1. The secondary battery according to claim 1, wherein the electrolytic solution further includes a cyclic monosulfonic acid ester represented by the following general formula (2).

(However, in the general formula (2), n is 0 to 2 integer. Also, R ₅ to R ₁₀ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl having 1 to 12 carbon atoms An atom or a group selected from a group, a substituted or unsubstituted fluoroalkyl group having 1 to 6 carbon atoms, and a polyfluoroalkyl group having 1 to 6 carbon atoms. The secondary battery according to claim 1, wherein the electrolytic solution further includes a cyclic sulfonic acid ester having two sulfonyl groups represented by the following general formula (3).

(However, in the said General formula (3), Q is an oxygen atom, a methylene group, or a single bond, A is a substituted or unsubstituted C1-C5 alkylene group, a carbonyl group, a sulfinyl group, C1-C5. At least one C—C bond in the polyfluoroalkylene group, a substituted or unsubstituted fluoroalkylene group having 1 to 5 carbon atoms, or a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms is a C—O—C bond A group in which at least one C—C bond in the polyfluoroalkylene group having 1 to 5 carbon atoms is a C—O—C bond, and a substituted or unsubstituted fluoroalkylene having 1 to 5 carbon atoms A group selected from a group in which at least one CC bond in the group is a C—O—C bond, B is a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, carbon 1-5 polyfluoroalkylene group, and a substituted or unsubstituted group selected from fluoroalkylene group having 1 to 5 carbon atoms.)   The secondary battery according to any one of claims 1 to 8, wherein the electrolytic solution further contains at least one of vinylene carbonate and a derivative thereof.   The secondary battery according to claim 1, wherein the electrolyte includes a lithium salt. The lithium salt is LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , LiAlCl ₄ and LiN (C _k F _{2k + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ ) (k and m are respectively The secondary battery according to claim 10, wherein the secondary battery is at least one lithium salt selected from the group consisting of 1 or 2 independently.   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 secondary battery according to claim 1, wherein the secondary battery is an organic solvent.   The secondary battery according to claim 1, wherein the secondary battery is covered with a laminate outer package.

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