JP4876495B2 - Electrolyte for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

The present invention is a lithium ion secondary battery electrolyte and a lithium ion secondary battery using the same including additives.

  In recent years, many portable electronic devices such as notebook portable computers, cellular phones, and camera-integrated VTRs (video tape recorders) have appeared, and their size and weight have been reduced. Accordingly, as a power source for these portable electronic devices, development of a secondary battery that is lightweight and capable of obtaining a high energy density is in progress. As a secondary battery capable of obtaining a high energy density, for example, a lithium ion secondary battery using a material capable of inserting and extracting lithium (Li) such as a carbon material as a negative electrode active material, or a negative electrode A lithium metal secondary battery using metallic lithium as an active material is known, and for example, ethylene carbonate or dimethyl carbonate is appropriately used as an electrolytic solution.

Among these, in the lithium ion secondary battery, since the negative electrode becomes a strong reducing agent in the charged state, the electrolytic solution is easily decomposed, and the battery characteristics such as the discharge capacity or the cycle characteristics are deteriorated. Therefore, conventionally, an electrolytic solution containing an additive such as vinylene carbonate has been proposed in order to improve battery characteristics such as cycle characteristics (see, for example, Patent Documents 1 and 2).
International Publication No. 01/22519 Pamphlet JP 2003-197259 A

  However, the effect of improving battery characteristics by these electrolytic solutions is not yet sufficient, and further improvement has been desired.

The present invention has been made in view of such problems, and an object thereof is to provide an electrolytic solution for a lithium ion secondary battery capable of improving cycle characteristics and a lithium ion secondary battery using the same. .

The electrolytic solution for a lithium ion secondary battery according to the present invention contains the disulfonic acid ester derivative shown in Chemical Formula 1 and the sulfonic acid ester derivative shown in Chemical Formula 2.

（式中、Ｒ１，Ｒ２はアルキル基を表す。ｎは正の整数である。）

(In the formula, R1 and R2 represent an alkyl group. N is a positive integer.)

（式中、Ｒ３，Ｒ４はアルキル基を表す。）

(In the formula, R3 and R4 represent an alkyl group.)

A lithium ion secondary battery according to the present invention is provided with an electrolyte solution together with a positive electrode and a negative electrode, and the electrolyte solution comprises a disulfonic acid ester derivative shown in Chemical formula 3 and a sulfonic acid ester derivative shown in Chemical formula 4. Is included.

（式中、Ｒ１，Ｒ２はアルキル基を表す。ｎは正の整数である。）

(In the formula, R1 and R2 represent an alkyl group. N is a positive integer.)

（式中、Ｒ３，Ｒ４はアルキル基を表す。）

(In the formula, R3 and R4 represent an alkyl group.)

According to the electrolytic solution for a lithium ion secondary battery of the present invention, since the disulfonic acid ester derivative shown in Chemical formula 1 and the sulfonic acid ester derivative shown in Chemical formula 2 are included, chemical stability is improved. be able to. Therefore, according to the lithium ion secondary battery of the present invention using this electrolytic solution, the decomposition reaction of the electrolytic solution in the negative electrode can be suppressed, and the cycle characteristics can be improved.

  In particular, when the content of the disulfonic acid ester derivative in the electrolytic solution is 5% by mass or less and the content of the sulfonic acid ester derivative is 5% by mass or less, a higher effect can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  The electrolytic solution according to an embodiment of the present invention includes, for example, a solvent and an electrolyte salt dissolved in the solvent.

  Examples of the solvent include ethylene carbonate, propylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-fluoro-1,3-dioxolan-2-one, 1,2-dimethoxyethane, 1,2- Diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, acetate ester, butyrate ester Or a non-aqueous solvent such as propionic acid ester. As the solvent, one kind may be used alone, or a plurality of kinds may be mixed and used.

Examples of the electrolyte salt include lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, or LiBr. . As the electrolyte salt, one kind may be used alone, or a plurality of kinds may be mixed and used.

  The electrolytic solution also contains the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6 as additives. Thereby, the chemical stability of the electrolytic solution can be increased.

  In Chemical Formula 5, R1 and R2 represent an alkyl group. As the alkyl group, those having 1 to 6 carbon atoms are preferable. This is because if the carbon number is large, the viscosity of the electrolytic solution increases and the ionic conductivity decreases. Specific examples include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group or a hexyl group, or a branched alkyl group such as an isopropyl group, an isobutyl group or an isopentyl group. It is done. R1 and R2 may be the same or different. The value of n is preferably 2 to 6. This is because if the value of n is large, the viscosity of the electrolytic solution increases and the ionic conductivity decreases.

  In Chemical Formula 6, R3 and R4 each represents an alkyl group. As the alkyl group, those having 1 to 6 carbon atoms are preferable. This is because if the carbon number is large, the viscosity of the electrolytic solution increases and the ionic conductivity decreases. Specific examples include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group or a hexyl group, or a branched alkyl group such as an isopropyl group, an isobutyl group or an isopentyl group. It is done. R3 and R4 may be the same or different.

  Specific examples of the disulfonate derivative include ethylene glycol dimethanesulfonate shown in Chemical formula 7 (1), 1,3-propanediol dimethanesulfonate shown in Chemical formula 7 (2), chemical formula 7 (3) 1,4-butanediol dimethanesulfonate shown in chemical formula 7, 1,6-hexanediol dimethanesulfonate shown in chemical formula 7 (4), 1,4-butanediol diethanesulfonate shown in chemical formula 7 (5) 1, 4-butanediol dipropane sulfonate shown in 7 (6) or 1,4-butanediol diisopropane sulfonate shown in Chemical formula 7 (7).

  Specific examples of the sulfonic acid ester derivatives include methyl methanesulfonate shown in Chemical formula 8 (1), ethyl methanesulfonate shown in Chemical formula 8 (2), and methane shown in Chemical formula 8 (3). Propyl sulfonate, isopropyl methanesulfonate shown in Chemical formula 8 (4), butyl methanesulfonate shown in Chemical formula 8 (5), hexyl methanesulfonate shown in Chemical formula 8 (6), chemical formula 8 (7) In addition, butyl ethane sulfonate, butyl propane sulfonate shown in Chemical Formula 8 (8), butyl isopropane sulfonate shown in Chemical Formula 8 (9), butyl butane sulfonate shown in Chemical Formula 8 (10), or Chemical Formula 8 ( 11) and butyl hexanesulfonate.

  The content of the disulfonic acid ester derivative in the electrolytic solution is preferably 5% by mass or less, and the content of the sulfonic acid ester derivative in the electrolytic solution is preferably 5% by mass or less. This is because when these contents increase, the viscosity of the electrolytic solution increases and the ionic conductivity decreases.

  This electrolytic solution is used for a secondary battery as follows, for example.

(First secondary battery)
FIG. 1 shows a cross-sectional structure of the first secondary battery. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21 </ b> B includes a positive electrode material capable of inserting and extracting lithium, which is an electrode reactant, for example, as the positive electrode active material.

Examples of the positive electrode material capable of inserting and extracting lithium include lithium such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), and vanadium oxide (V ₂ O ₅ ). And metal sulfides or metal oxides that do not contain.

As a positive electrode material capable of inserting and extracting lithium, Li _x MIO ₂ (wherein MI represents one or more transition metal elements. The value of x varies depending on the charge / discharge state of the battery, and is usually 0.05 ≦ x ≦ 1.10)). As the transition metal element MI, cobalt (Co), nickel, manganese (Mn) and the like are preferable. A specific example for such a lithium composite _{oxide, LiCoO 2, LiNiO 2, Li} y Ni z Co 1-z O 2 ( wherein, y, z vary according to charge and discharge state of the battery, usually 0 <Y <1, 0.5 <z <1.0), or a lithium manganese composite oxide having a spinel structure such as LiMn ₂ O ₄ . Furthermore, Li _v MIIPO ₄ (wherein MII represents one or more transition metal elements. The value of v varies depending on the charge / discharge state of the battery, and is generally 0.05 ≦ v ≦ 1.10.) And, specifically, a lithium iron phosphate compound such as LiFePO ₄ .

  The positive electrode active material layer 21B may include a conductive agent or a binder as necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black, and one kind or a mixture of two or more kinds is used. In addition to the carbon material, a metal material or a conductive polymer material may be used as long as it is a conductive material. Examples of the binder include synthetic rubber such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene rubber, or a polymer material such as polyvinylidene fluoride, and one or two or more kinds are used in combination. It is done.

  The negative electrode 22 has, for example, a configuration in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. Although not shown, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium, which is an electrode reactant, for example, as a negative electrode active material. For example, the same conductive agent and binder as those of the positive electrode active material layer 21B may be included.

  Examples of the negative electrode material capable of inserting and extracting lithium include a carbon material. Specifically, artificial graphite, natural graphite, pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound sintered bodies, fibrous carbon, activated carbon, carbon blacks, or non-graphitizable carbon and so on. Examples of the coke include pitch coke, needle coke, and petroleum coke. The organic polymer compound sintered body is a carbonized material obtained by firing a polymer material such as phenols or furans at an appropriate temperature.

  Examples of the negative electrode material capable of inserting and extracting lithium also include a negative electrode material capable of inserting and extracting lithium and including at least one of a metal element and a metalloid element as a constituent element. It is done. This is because a high energy density can be obtained by using such a negative electrode material. This negative electrode material may be a single element, alloy or compound of a metal element or a metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of metal elements or metalloid elements constituting the negative electrode material include magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), and silicon (Si) that can form an alloy with lithium. , Germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y) , Palladium (Pd) or platinum (Pt). These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon and tin is particularly preferable as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

  Examples of tin alloys include silicon, nickel, copper (Cu), iron, cobalt, manganese, zinc, indium, silver, titanium (Ti), germanium, bismuth, and antimony (second constituent elements other than tin). Sb) and those containing at least one selected from the group consisting of chromium (Cr). As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

  Examples of the tin compound or silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to tin or silicon.

  In addition, you may make it use this negative electrode material with the carbon material which can occlude and discharge | release lithium mentioned above. Carbon materials have very little change in the crystal structure that occurs during charge and discharge, and if they are used together, high energy density and excellent cycle characteristics can be obtained. preferable. A carbon material is also preferable because it functions as a conductive agent.

  Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds and polymer materials. Other metal compounds include oxides such as iron oxide, ruthenium oxide, molybdenum oxide, tungsten oxide, titanium oxide or tin oxide, sulfides such as nickel sulfide or molybdenum sulfide, or nitrides such as lithium nitride, Examples of the polymer material include polyacetylene and polypyrrole.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is composed of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. The porous film may be laminated.

  The separator 23 is impregnated with the above-described electrolytic solution. Thereby, the decomposition reaction of the electrolytic solution in the negative electrode 22 can be suppressed, and the cycle characteristics can be improved.

  For example, the secondary battery can be manufactured as follows.

  First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like material. A positive electrode mixture slurry is obtained. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like, and the positive electrode 21 is manufactured.

  Further, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry And Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, and the solvent is dried. Then, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured.

  Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIG. 1 is completed.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through the electrolytic solution. In addition, when discharging is performed, for example, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution. At that time, the electrolytic solution contains the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6, so that the chemical stability of the electrolytic solution is improved, and The decomposition reaction of the electrolytic solution is suppressed.

  As described above, according to the present embodiment, the electrolytic solution includes the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6, so that the chemical stability of the electrolytic solution is improved. The cycle characteristics can be improved.

  In particular, when the content of the disulfonic acid ester derivative in the electrolytic solution is 5% by mass or less and the content of the sulfonic acid ester derivative is 5% by mass or less, a higher effect can be obtained.

(Secondary secondary battery)
FIG. 3 shows the configuration of the second secondary battery. This secondary battery is a so-called laminate film type, and has a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached accommodated in a film-shaped exterior member 40.

  The positive electrode lead 31 and the negative electrode lead 32 are led out, for example, in the same direction from the inside of the exterior member 40 to the outside, and are each made of a metal material such as aluminum, copper, nickel, or stainless steel.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows a cross-sectional structure taken along line II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is formed by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, and the outermost periphery is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on one or both surfaces of a positive electrode current collector 33A. The negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on one surface or both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B and the positive electrode active material layer 33B are arranged to face each other. Yes. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are the same as the positive electrode current collector 21A and the positive electrode active material layer 21B in the first secondary battery described above. , The same as the anode current collector 22A, the anode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution according to the present embodiment and a polymer compound that serves as a holding body that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because it can obtain high ionic conductivity and prevent leakage. The configuration of the electrolytic solution is the same as that of the first secondary battery.

  Examples of the polymer compound include, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, or an acrylate polymer compound, or polyvinylidene fluoride or vinylidene fluoride. Examples thereof include polymers of vinylidene fluoride such as a copolymer with hexafluoropropylene, and any one of these or a mixture of two or more thereof is used. In particular, from the viewpoint of redox stability, it is desirable to use a fluorine-based polymer compound such as a vinylidene fluoride polymer.

  For example, the secondary battery can be manufactured as follows.

  First, after forming the positive electrode 33 and the negative electrode 34 as described above, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34 to volatilize the mixed solvent. Thus, the electrolyte layer 36 is formed. Next, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are stacked via the separator 35, and then wound in the longitudinal direction to form the wound electrode body 30. After that, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edge portions of the exterior members 40 are sealed and sealed by thermal fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 40. Subsequently, an electrolyte composition including an electrolytic solution, a monomer that is a raw material of the polymer compound, and other materials such as a polymerization initiator or a polymerization inhibitor as necessary is prepared, and the interior of the exterior member 40 is prepared. After the injection, the opening of the exterior member 40 is heat-sealed and sealed. After that, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming a gel electrolyte layer 36 and assembling the secondary battery shown in FIGS.

  The operation of this secondary battery is the same as that of the first secondary battery described above.

  As described above, also in the second secondary battery, since the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6 are included in the electrolytic solution, cycle characteristics are improved. be able to.

  Further, specific embodiments of the present invention will be described in detail.

(Example 1-1)
The cylindrical secondary battery shown in FIGS. First, 95 parts by mass of lithium cobalt oxide (LiCoO ₂ ) powder as a negative electrode active material and 5 parts by mass of lithium carbonate powder (Li ₂ CO ₃ ) powder were mixed, and 94 parts by mass of this mixture and Ketjen as a conductive agent. 3 parts by mass of black (amorphous carbon powder) and 3 parts by mass of polyvinylidene fluoride as a binder were mixed and dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a positive electrode mixture slurry. Next, the positive electrode mixture slurry was uniformly applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and compression-molded to form a positive electrode active material layer 21B to produce a positive electrode 21. . The total thickness of the positive electrode 21 was 150 μm. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

  Further, 90 parts by mass of artificial graphite powder having an average particle size of 30 μm and 10 parts by mass of polyvinylidene fluoride as a negative electrode active material were mixed and dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a negative electrode mixture slurry. . After that, this negative electrode mixture slurry was uniformly applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 15 μm, dried, and compression molded to form a negative electrode active material layer 22B to produce a negative electrode 22. . The total thickness of the negative electrode 22 was 160 μm. Subsequently, a negative electrode lead 26 made of nickel was attached to one end of the negative electrode current collector 22A.

  After preparing the positive electrode 21 and the negative electrode 22, a separator 23 made of a microporous film is prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 are laminated in this order, and this laminate is wound many times in a spiral shape. Thus, a jelly roll type wound electrode body 20 having an outer diameter of 17.5 mm was produced.

After producing the wound electrode body 20, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The wound electrode body 20 was housed inside a nickel-plated iron battery can 11. Subsequently, an electrolytic solution was injected into the battery can 11 by a reduced pressure method. In the electrolytic solution, LiPF ₆ is dissolved as an electrolyte salt in a mixed solvent in which ethylene carbonate, dimethyl carbonate, and vinylene carbonate are mixed in a volume ratio of ethylene carbonate: dimethyl carbonate: vinylene carbonate = 30: 69: 1, As additives, disulfonic acid ester derivatives shown in Chemical formula 5 and sulfonic acid ester derivatives shown in Chemical formula 6 were added. The disulfonic acid ester derivative was 1,4-butanediol dimethanesulfonate shown in Chemical Formula 7 (3), and the sulfonic acid ester derivative was butyl methanesulfonic acid shown in Chemical Formula 8 (5). The contents of the disulfonic acid ester derivative and the sulfonic acid ester derivative in the electrolytic solution were each 1% by mass, and the concentration of LiPF ₆ was 1 mol / l.

  After that, the battery lid 24 was caulked to the battery can 21 via the gasket 27 to produce a cylindrical secondary battery having a diameter of 18 mm and a height of 65 mm.

  As Comparative Example 1-1 with respect to Example 1-1, a secondary battery was fabricated in the same manner as in Example 1-1 except that the disulfonic acid ester derivative and the sulfonic acid ester derivative were not added. Further, as Comparative Examples 1-2 and 1-3, a secondary battery was fabricated in the same manner as in Example 1-1 except that only the disulfonic acid ester derivative was added without adding the sulfonic acid ester derivative. did. The content of the disulfonic acid ester derivative in the electrolytic solution was 1% by mass in Comparative Example 1-2 and 2% by mass in Comparative Example 1-3. Further, as Comparative Examples 1-4 and 1-5, a secondary battery was fabricated in the same manner as in Example 1-1 except that only the sulfonic acid ester derivative was added without adding the disulfonic acid ester derivative. did. The content of the sulfonic acid ester derivative in the electrolytic solution was 1% by mass in Comparative Example 1-4, and 2% by mass in Comparative Example 1-5.

  About the produced secondary battery of Example 1-1 and Comparative Examples 1-1-5, charging / discharging was performed and cycling characteristics were investigated. At that time, charging was performed at a constant current of 500 mA until the battery voltage reached 4.2 V, and then at a constant voltage of 4.2 V until the total charging time was 8 hours, and discharging was performed at 300 mA. The test was performed at a constant current until the battery voltage reached 2.75V. The cycle characteristics are obtained by repeating this charging / discharging, from the discharge capacity maintenance ratio at the 200th cycle with respect to the discharge capacity at the second cycle, that is, (discharge capacity at the 200th cycle / discharge capacity at the second cycle) × 100 (%). It was. The results are shown in Table 1.

  As can be seen from Table 1, according to Example 1-1 using 1,4-butanediol dimethanesulfonate and butyl methanesulfonate, Comparative Example 1-1 in which these were not added, or these The discharge capacity retention rate increased dramatically compared to Comparative Examples 1-2 and 1-4 to which only one of them was added. In addition, only 1,4-butanediol dimethanesulfonate or only butylmethanesulfonate was used in the same amount as the total content of 1,4-butanedioldimethanesulfonate and butylmethanesulfonate in Example 1-1, respectively. In Comparative Examples 1-3 and 1-5, the effect of improving the discharge capacity retention rate was lower than that of Example 1-1.

  That is, it was found that the cycle characteristics can be improved by mixing and using the disulfonic acid ester derivative shown in Chemical formula 5 and the disulfonic acid ester derivative shown in Chemical formula 6.

(Examples 2-1 to 2-10)
A secondary battery was fabricated in the same manner as in Example 1-1 except that another sulfonic acid ester derivative was used instead of butyl methanesulfonate. In Example 2-1, the sulfonic acid ester derivative was methyl methanesulfonate shown in Chemical Formula 8 (1), and in Example 2-2, the ethyl methanesulfonate shown in Chemical Formula 8 (2) was used. In 2-3, propyl methanesulfonate shown in Chemical Formula 8 (3) is used, in Example 2-4, isopropyl methanesulfonate shown in Chemical Formula 8 (4) is used, and in Example 2-5, Chemical Formula 8 ( Hexyl methanesulfonate shown in 6), butyl ethanesulfonate shown in Chemical Formula 8 (7) in Example 2-6, and propanesulfonic acid shown in Chemical Formula 8 (8) in Example 2-7 In Example 2-8, butyl isopropanesulfonate shown in Chemical Formula 8 (9) was used, and in Example 2-9, butyl butanesulfonate shown in Chemical Formula 8 (10) was used. 10 is the same as that shown in Chemical formula 8 (11). It was a three-sulfonic acid butyl.

  For the fabricated secondary batteries of Examples 2-1 to 2-10, cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 2.

  As can be seen from Table 2, in Examples 2-1 to 2-10 using other sulfonic acid ester derivatives, the discharge capacity retention rate was dramatically improved as in Example 1-1. That is, it was found that the cycle characteristics can be improved even when other sulfonic acid ester derivatives shown in Chemical Formula 6 are used.

(Examples 3-1 to 3-6)
A secondary battery was fabricated in the same manner as in Example 1-1 except that another disulfonic acid ester derivative was used instead of 1,4-butanediol dimethanesulfonate. In Example 3-1, the disulfonic acid ester derivative was ethylene glycol dimethanesulfonate shown in Chemical formula 7 (1), and in Example 3-2, 1,3-propanediol diester shown in Chemical formula 7 (2) was used. In Example 3-3, 1,6-hexanediol dimethanesulfonate shown in Chemical Formula 7 (4) was used, and in Example 3-4, 1,4-butane shown in Chemical Formula 7 (5) was used. Diol diethane sulfonate, 1,4-butanediol dipropane sulfonate shown in Chemical Formula 7 (6) in Example 3-5, and 1, 4 shown in Chemical Formula 7 (7) in Example 3-6 -Butanediol diisopropane sulfonate.

  For the fabricated secondary batteries of Examples 3-1 to 3-6, the cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 3.

  As can be seen from Table 3, also in Examples 3-1 to 3-6 using other disulfonic acid ester derivatives, the discharge capacity retention rate was dramatically improved as in Example 1-1. That is, it was found that the cycle characteristics can be improved even when the disulfonic acid ester derivative shown in the other chemical formula 5 is used.

(Examples 4-1 to 4-4, 5-1 to 5-4)
As Examples 4-1 to 4-4, secondary batteries were produced in the same manner as in Example 1-1 except that the content of 1,4-butanediol dimethanesulfonate in the electrolytic solution was changed. did. The content of 1,4-butanediol dimethanesulfonate in the electrolytic solution is 5% by mass in Example 4-1, 2% by mass in Example 4-2, and 0.1% by mass in Example 4-3. In Example 4-4, the content was 0.01% by mass.

  As Examples 5-1 to 5-4, secondary batteries were fabricated in the same manner as in Example 1-1 except that the content of butyl methanesulfonate in the electrolytic solution was changed. The content of butyl methanesulfonate in the electrolytic solution was 5% by mass in Example 5-1, 2% by mass in Example 5-2, 0.1% by mass in Example 5-3, and Example 5 In -4, the content was 0.01% by mass.

  Regarding the fabricated secondary batteries of Examples 4-1 to 4-4 and 5-1 to 5-5, cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Tables 4 and 5.

  As can be seen from Tables 4 and 5, the discharge capacity retention rate increases as the content of 1,4-butanediol dimethanesulfonate or butylmethanesulfonate in the electrolyte increases, and the maximum value is reached. After showing, there was a tendency to decrease.

  That is, if the content of the disulfonic acid ester derivative shown in Chemical Formula 5 in the electrolytic solution is 5% by mass or less and the content of the sulfonic acid ester derivative shown in Chemical Formula 6 in the electrolytic solution is 5% by mass or less. It turned out to be preferable.

(Examples 6-1 to 6-4)
A secondary battery was fabricated in the same manner as in Example 1-1, except that the composition of the solvent was changed. In Example 6-1, the solvent was ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (MEC), and vinylene carbonate (VC), ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate: Vinylene carbonate = a mixed solvent mixed at a volume ratio of 30: 39: 30: 1. In Example 6-2, ethylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), and vinylene carbonate were mixed with ethylene carbonate: Dimethyl carbonate: diethyl carbonate: vinylene carbonate = a mixed solvent mixed at a volume ratio of 30: 39: 30: 1. In Example 6-3, ethylene carbonate, propylene carbonate (PC), dimethyl carbonate, and vinylene carbonate And a mixed solvent of ethylene carbonate: propylene carbonate: dimethyl carbonate: vinylene carbonate = 20: 10: 69: 1, and in Example 6-4 Ethylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), dimethyl carbonate, and vinylene carbonate, ethylene carbonate: 4-fluoro-1,3-dioxolan-2-one: dimethyl carbonate : Vinylene carbonate = a mixed solvent mixed at a volume ratio of 20: 10: 69: 1.

  As Comparative Examples 6-1 to 6-4 with respect to Examples 6-1 to 6-4, except that the disulfonic acid ester derivative and the sulfonic acid ester derivative were not added, the others were Examples 6-1 to 6-4. A secondary battery was fabricated in the same manner as described above.

  For the fabricated secondary batteries of Examples 6-1 to 6-4 and Comparative examples 6-1 to 6-4, the cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 6.

  As can be seen from Table 6, according to Examples 6-1 to 6-4 using other solvents and using 1,4-butanediol dimethanesulfonate and butyl methanesulfonate, Example 1-1 Similarly to Comparative Examples 6-1 to 6-4 in which 1,4-butanediol dimethanesulfonate and butyl methanesulfonate were not used, the discharge capacity retention rates were dramatically improved.

  That is, it was found that if the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6 were used, the cycle characteristics could be improved even if other solvents were used.

(Examples 7-1 to 7-4)
A secondary battery was fabricated in the same manner as in Example 1-1 except that another positive electrode active material was used instead of lithium cobalt oxide (LiCoO ₂ ). The positive electrode active material is LiNi _0.8 Co _0.2 O ₂ in Example 7-1, LiNi _0.5 Co _0.5 O _{2 in} Example 7-2, and LiCoO ₂ and LiNi in Examples 7-3 and 7-4. _0.8 Co _0.2 O ₂ was mixed at a mass ratio of LiCoO ₂ : LiNi _0.8 Co _0.2 O ₂ = 1: 1 or 1: 2.

  As Comparative Examples 7-1 to 7-4 with respect to Examples 7-1 to 7-4, except that a disulfonic acid ester derivative and a sulfonic acid ester derivative were not added, the others were Examples 7-1 to 7-4. A secondary battery was fabricated in the same manner as described above.

  Regarding the fabricated secondary batteries of Examples 7-1 to 7-4 and Comparative examples 7-1 to 7-4, cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 7.

  As can be seen from Table 7, according to Examples 7-1 to 7-4 using other positive electrode active materials and using 1,4-butanediol dimethanesulfonate and butyl methanesulfonate, Example 1 Similarly to -1, the discharge capacity retention rate was dramatically improved over Comparative Examples 7-1 to 7-4 in which 1,4-butanediol dimethanesulfonate and butyl methanesulfonate were not used.

  That is, it can be seen that if the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6 are used, the cycle characteristics can be improved even if other positive electrode active materials are used. It was.

(Examples 8-1 to 8-3)
A secondary battery was fabricated in the same manner as in Example 1-1 except that another negative electrode active material was used instead of the artificial graphite. The negative electrode active material was natural graphite in Example 8-1, a copper-silicon alloy in Example 8-2, and a copper-tin alloy in Example 8-3. In Example 8-2, copper-silicon alloy, artificial graphite as a conductive agent and a negative electrode active material, polyvinylidene fluoride as a binder, copper-silicon alloy: artificial graphite: polyvinylidene fluoride = 50 : 45: using negative electrode mixture were mixed at a weight ratio of 5, in example 8-3, copper - tin alloy, and artificial graphite as a conductive agent and the negative Katsubutsu quality, and polyvinylidene fluoride as a binder Was mixed at a mass ratio of copper-tin alloy: artificial graphite: polyvinylidene fluoride = 50: 45: 5.

  As Comparative Examples 8-1 to 8-3 with respect to Examples 8-1 to 8-3, except that the disulfonic acid ester derivative and the sulfonic acid ester derivative were not added, the others were Examples 8-1 to 8-3. A secondary battery was fabricated in the same manner as described above.

  For the fabricated secondary batteries of Examples 8-1 to 8-3 and Comparative examples 8-1 to 8-3, cycle characteristics were examined in the same manner as in Example 1-1. The results are shown in Table 8.

  As can be seen from Table 8, according to Examples 8-1 to 8-3 using other negative electrode active materials and using 1,4-butanediol dimethanesulfonate and butyl methanesulfonate, Example 1 As in -1, the discharge capacity retention rate was dramatically improved over Comparative Examples 8-1 to 8-3 in which 1,4-butanediol dimethanesulfonate and butyl methanesulfonate were not used.

  That is, it is understood that if the disulfonic acid ester derivative shown in Chemical formula 5 and the sulfonic acid ester derivative shown in Chemical formula 6 are used, the cycle characteristics can be improved even if other negative electrode active materials are used. It was.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the above embodiments and examples, a battery using lithium as an electrode reactant has been described. However, other alkali metals such as sodium (Na) or potassium (K), or alkalis such as magnesium or calcium (Ca) are used. The present invention can also be applied to the case of using an earth metal or another light metal such as aluminum. At that time, a positive electrode active material or a solvent that can occlude and release the electrode reactant is selected according to the electrode reactant.

Further, in the above embodiments and examples, a secondary battery using an exterior member such as a cylindrical secondary battery and a laminate film has been specifically described. However, the present invention includes a coin type, a button type, secondary battery having other shape such as square or Ru can be similarly applied to secondary batteries having other structures, such as a multilayer structure.

Furthermore, in the above-described embodiments and examples, the case where an electrolyte solution or a gel electrolyte in which the electrolyte solution is held in a holding body such as a polymer compound is used as the electrolyte has been described. a solid electrolyte may be used with the mixture.

  As the solid electrolyte, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, or an inorganic solid electrolyte made of ion conductive glass or ionic crystals can be used. In this case, as the polymer compound, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate or polyacrylate, or a mixture thereof, or in the molecule It can be used after being copolymerized. As the inorganic solid electrolyte, lithium nitride, lithium iodide, or the like can be used.

It is sectional drawing showing the structure of the 1st secondary battery which concerns on embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view showing the structure of the 2nd secondary battery which concerns on embodiment of this invention. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... Center pin, 25, 31 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte layer, 37 ... Protective tape, 40 ... Exterior member, 41 ... Adhesion film.

Claims (4)

An electrolyte for a lithium ion secondary battery, comprising the disulfonic acid ester derivative shown in Chemical Formula 1 and the sulfonic acid ester derivative shown in Chemical Formula 2.

(In the formula, R1 and R2 represent an alkyl group. N is a positive integer.)

(In the formula, R3 and R4 represent an alkyl group.) The content of the disulfonate ester derivative is not more than 5 wt%, the content of the sulfonic acid ester derivative is not more than 5 wt%, claim 1 for a lithium ion secondary battery electrolyte according. Bei example a cathode, an anode,
The electrolyte solution is a lithium ion secondary battery including the disulfonic acid ester derivative shown in Chemical formula 3 and the sulfonic acid ester derivative shown in Chemical formula 4.

(In the formula, R1 and R2 represent an alkyl group. N is a positive integer.)

(In the formula, R3 and R4 represent an alkyl group.) The content of the disulfonate ester derivative in the electrolytic solution is not more than 5 wt%, the content of the sulfonic acid ester derivative is not more than 5 wt%, the lithium ion secondary battery according to claim 3, wherein.

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