JP2010080188A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery capable of improving cycle characteristics and charging load characteristics. <P>SOLUTION: The secondary battery has a positive electrode 21, a negative electrode 22, and an electrolyte, and the electrolyte is impregnated into a separator 23 arranged between the positive electrode 21 and the negative electrode 22. A negative electrode active material of the negative electrode 22 includes a negative electrode material (high electrical potential material) which occludes and emits lithium ions at an electrical potential of 1.0V or more to a lithium potential. A solvent of the electrolyte includes carbonic acid ester having two or more of halogens as a constituent element. A film can be easily formed on the surface of the negative electrode 22 even when the high electrical potential material is used as a negative electrode active material. Thus, decomposition reaction of the electrolyte is restrained at the time of charge and discharge, and an acceptance nature of lithium ions on the negative electrode 22 is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a secondary battery provided with an electrolyte together with a positive electrode and a negative electrode capable of inserting and extracting lithium ions.

  In recent years, portable electronic devices such as video cameras, digital still cameras, mobile phones, and notebook computers have become widespread, and there is a strong demand for miniaturization, weight reduction, and long life. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is small and lightweight and capable of obtaining a high energy density is in progress.

  Among them, lithium ion secondary batteries that use the insertion and extraction of lithium ions for charge / discharge reactions are widely put into practical use because they have higher energy density than lead batteries and nickel cadmium batteries.

  A lithium ion secondary battery includes a positive electrode including a positive electrode active material capable of occluding and releasing lithium ions, a negative electrode including a negative electrode active material capable of occluding and releasing lithium ions, a solvent, and an electrolyte salt. An electrolyte containing.

  As the negative electrode active material, carbon materials such as graphite are widely used, but other materials are also attracting attention. Examples of such other materials include materials that require a high potential in order to occlude and release lithium ions.

Various studies have been made on the configuration of the lithium ion secondary battery. Specifically, in applications such as long life or rapid charging, lithium titanate or lithium hydrogen titanate is used as a material that requires a high potential to occlude and release lithium ions (for example, patent documents). 1-6.)
Japanese Patent Laid-Open No. 06-275263 JP 2007-173150 A JP 2007-141860 A JP 2008-091327 A WO99 / 03784 pamphlet WO99 / 04442 pamphlet

In addition, cyclic carbonates having one or more halogens as constituent elements are used as electrolyte solvents (see, for example, Patent Documents 7 to 10).
JP 2007-165078 A Japanese Patent Application Laid-Open No. 07-240232 Japanese Patent Laid-Open No. 08-306364 JP 2008-010414 A

  In recent years, portable electronic devices have become more sophisticated and multifunctional, and their power consumption tends to increase. Therefore, charging and discharging of secondary batteries are frequently repeated. Therefore, in order to use the secondary battery safely at high frequency, further improvement in cycle characteristics and charging load characteristics is desired.

  The present invention has been made in view of such problems, and an object thereof is to provide a secondary battery capable of improving cycle characteristics and charge load characteristics.

  The secondary battery of the present invention includes a positive electrode including a positive electrode active material capable of inserting and extracting lithium ions, a negative electrode including a negative electrode active material capable of inserting and extracting lithium ions, a solvent, and an electrolyte salt The negative electrode active material includes a negative electrode material that absorbs and releases lithium ions at a potential of 1.0 V or higher with respect to the lithium potential, and the solvent is a carbonic acid having two or more halogens as constituent elements. It contains an ester.

  According to the secondary battery of the present invention, the negative electrode active material of the negative electrode includes a negative electrode material that absorbs and releases lithium ions at a potential of 1.0 V or higher with respect to the lithium potential, and the electrolyte has two or more solvents. Carbonates having the halogen as a constituent element. In this case, even when a material that requires a high potential to occlude and release lithium ions is used as the negative electrode active material, a film is easily formed on the surface of the negative electrode. Thereby, at the time of charging / discharging, the decomposition reaction of the electrolyte is suppressed, and the acceptability of lithium ions in the negative electrode is improved. Therefore, cycle characteristics and charge load characteristics can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The order of explanation is as follows.

1. First embodiment (battery structure: cylindrical type)
2. Second embodiment (battery structure: laminate film type)

[1. First Embodiment]
1 and 2 show a cross-sectional configuration of the secondary battery according to the first embodiment of the present invention. FIG. 1 shows a cross section in the longitudinal direction of the secondary battery, and FIG. 2 shows an enlarged part of the cross section shown in FIG.

  This secondary battery is a lithium ion secondary battery in which the capacity of the negative electrode is expressed by occlusion and release of lithium ions, mainly inside the battery can 11 having a substantially hollow cylindrical shape, A pair of insulating plates 12 and 13 are accommodated. A battery structure using such a cylindrical battery can 11 is called a cylindrical type.

  The battery can 11 is made of, for example, iron (Fe), aluminum (Al), or an alloy thereof, and one end thereof is opened and the other end is closed. The pair of insulating plates 12 and 13 are arranged so as to sandwich the wound electrode body 20 from above and below and to extend perpendicularly to the wound peripheral surface.

  A battery lid 14 and a safety valve mechanism 15 and a heat sensitive resistance element (Positive Temperature Coefficient: PTC element) 16 provided inside the battery can 11 are caulked through a gasket 17 at the open end of the battery can 11. It is attached. The inside of the battery can 11 is sealed by this caulking process. 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. In the safety valve mechanism 15, when the internal pressure becomes a certain level or more due to an internal short circuit or external heating, the disk plate 15 </ b> A is reversed and the electric power between the battery lid 14 and the wound electrode body 20 is reversed. Connection is cut off. The heat-sensitive resistance element 16 limits the current by increasing the resistance as the temperature rises, and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and for example, asphalt is applied to the surface thereof.

  The wound electrode body 20 is obtained by laminating and winding a positive electrode 21 and a negative electrode 22 with a separator 23 interposed therebetween. For example, a center pin 24 is inserted in the center thereof. In the wound electrode body 20, a positive electrode lead 25 made of aluminum or the like is connected to the positive electrode 21, and a negative electrode lead 26 made of nickel (Ni) or the like is connected to the negative electrode 22. The positive electrode lead 25 is welded to the safety valve mechanism 15 and electrically connected to the battery lid 14, and the negative electrode lead 26 is welded to the battery can 11 and electrically connected thereto.

  For example, the positive electrode 21 is obtained by providing a positive electrode active material layer 21B on both surfaces of a positive electrode current collector 21A having a pair of surfaces. However, 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, aluminum, nickel, stainless steel, or the like.

  The positive electrode active material layer 21 </ b> B contains one or more positive electrode materials capable of inserting and extracting lithium ions as the positive electrode active material. The positive electrode active material layer 21B may contain other materials such as a positive electrode binder or a positive electrode conductive agent together with the positive electrode active material as necessary.

As a positive electrode material capable of inserting and extracting lithium ions, for example, a lithium-containing compound is preferable. This is because a high energy density can be obtained. Examples of the lithium-containing compound include a composite oxide having lithium and a transition metal element as constituent elements, or a phosphate compound having lithium and a transition metal element as constituent elements. Especially, what has at least 1 sort (s) of cobalt (Co), nickel, manganese (Mn), and iron as a transition metal element is preferable. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x M1O ₂ or Li _y M2PO ₄ . In the formula, M1 and M2 represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Examples of the composite oxide having lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni). _1-z Co _z O ₂ (z <1)), lithium nickel cobalt manganese composite oxide (Li _x Ni _(1-vw) Co _v Mn _w O ₂ (v + w <1)), or lithium having a spinel structure Manganese composite oxide (LiMn ₂ O ₄ ) and the like can be mentioned. Especially, what has cobalt as a transition metal element is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can be obtained. Examples of the phosphate compound having lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-u Mn _u PO ₄ (u <1)). Etc.

  In addition, examples of the positive electrode material capable of inserting and extracting lithium ions include oxides, disulfides, chalcogenides, and conductive polymers. Examples of the oxide include titanium oxide, vanadium oxide, and manganese dioxide. Examples of the disulfide include titanium disulfide and molybdenum sulfide. An example of the chalcogenide is niobium selenide. Examples of the conductive polymer include sulfur, polyaniline, and polythiophene.

  Of course, the positive electrode material capable of inserting and extracting lithium ions may be other than the above. Further, two or more kinds of the series of positive electrode materials may be mixed in any combination.

  Examples of the positive electrode binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber, and ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be single and multiple types may be mixed.

  Examples of the positive electrode conductive agent include carbon materials such as graphite, carbon black, acetylene black, and ketjen black. These may be single and multiple types may be mixed. The positive electrode conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  In the negative electrode 22, for example, a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of surfaces. However, 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 a material having good electrochemical stability, electrical conductivity, and mechanical strength. Examples of such a material include copper (Cu), nickel, titanium, and stainless steel.

  The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion between the negative electrode current collector 22A and the negative electrode active material layer 22B. In this case, the surface of the negative electrode current collector 22A only needs to be roughened at least in a region facing the negative electrode active material layer 22B. Examples of the roughening method include a method of forming fine particles by electrolytic treatment. This electrolytic treatment is a method of providing irregularities by forming fine particles on the surface of the anode current collector 22A by an electrolytic method in an electrolytic bath. The copper foil produced by the electrolytic method is generally called “electrolytic copper foil”. The surface roughness of the negative electrode current collector 22A can be arbitrarily set.

  The negative electrode active material layer 22B contains one or more negative electrode materials capable of inserting and extracting lithium ions as a negative electrode active material. This negative electrode active material layer 22B may contain other materials such as a negative electrode binder or a negative electrode conductive agent together with the above negative electrode active material, if necessary. Note that details regarding the negative electrode binder and the negative electrode conductive agent are the same as, for example, the positive electrode binder and the positive electrode conductive agent, respectively.

  In this negative electrode active material layer 22B, for example, in order to prevent unintentional precipitation of lithium ions during charging and discharging, the chargeable capacity of the negative electrode material capable of inserting and extracting lithium ions is positive. It is preferable that the discharge capacity is greater than 21.

  As a negative electrode material capable of inserting and extracting lithium ions, any one of materials that store and release lithium ions at a potential of 1.0 V or more with respect to the lithium potential (hereinafter simply referred to as “high potential material”). 1 type or 2 types or more are preferable. This is because it is electrochemically stable. More specifically, since the potential of the negative electrode 22 is increased, the decomposition reaction of the electrolyte is suppressed and the volume change of the negative electrode 22 is also suppressed during charging and discharging. Note that the lower limit of the potential for inserting and extracting lithium ions in the high potential material is more preferably about 1.5 V, while the upper limit is not particularly limited, but is about 1.7 V, for example.

  The above-described “potential for inserting and extracting lithium ions” is a potential (potential with respect to lithium potential) when charging / discharging with a current amount of 0.2C. “C” is a unit representing a current value, and “XC” represents a current value at which the theoretical capacity can be completely discharged in 1 / X time. For this reason, “0.2 C” is a current value at which the theoretical capacity can be discharged in 5 hours.

  Examples of such high-potential materials include composite oxides having lithium and titanium as constituent elements, composite oxides having hydrogen and titanium as constituent elements, and metal oxides (corresponding to the above-described two kinds of composite oxides). Or a metal sulfide).

The composite oxide having lithium and titanium as constituent elements is, for example, a compound (lithium titanate) represented by Li _x Ti _y O _z having a spinel structure. A specific example of this compound is Li ₄ Ti ₅ O ₁₂ or the like, and the potential for inserting and extracting lithium ions is about 1.55 V in a flat portion in the potential change pattern during charge and discharge.

The composite oxide having hydrogen and titanium as constituent elements is, for example, a compound represented by H _x Ti _y O _z . Specific examples of this compound include H ₂ Ti ₃ O ₇ , H ₂ Ti ₆ O ₁₃ , and H ₂ Ti ₁₂ O ₂₅ .

Examples of the metal oxide include titanium oxide, niobium oxide, cobalt oxide (CoO, Co ₃ O ₄ ), nickel oxide (NiO), iron oxide (FeO), and copper oxide (CuO, Cu ₂ O). The crystal structure of titanium oxide may be any of a rutile type, anatase type, bronze type, hollandite type, ramsdellite type, or brookite type.

Examples of the metal sulfide include cobalt sulfide (CoS), nickel sulfide (NiS), iron sulfide (FeS, FeS ₂ ), and copper sulfide (CuS).

Among them, as the high potential material, for example, a compound having titanium as a constituent element is preferable, and a compound having oxygen as a constituent element is more preferable. Specifically, for example, a composite oxide having lithium and titanium as constituent elements is preferable, and Li ₄ Ti ₅ O ₁₂ is more preferable. This is because excellent effects can be obtained stably.

  In particular, when a high potential material is used, for example, it is preferable to coat the surface of the high potential material with a carbon material described later. This is because the electron conductivity of the negative electrode 22 is improved.

  Note that, as long as the negative electrode active material layer 22B includes the above-described high potential material as the negative electrode active material, the negative electrode active material layer 22B may also include other negative electrode materials capable of inserting and extracting lithium ions.

  Examples of such other negative electrode materials include carbon materials. This is because the change in crystal structure during insertion and extraction of lithium ions is very small, so that a high energy density can be obtained and it can also function as a conductive agent. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, or graphite having a (002) plane spacing of 0.34 nm or less. . More specifically, there are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon, carbon blacks, and the like. Of these, the cokes include pitch coke, needle coke, petroleum coke, and the like. The organic polymer compound fired body is obtained by firing and carbonizing a phenol resin or a furan resin at an appropriate temperature. The shape of the carbon material may be any of fibrous, spherical, granular or scale-like.

  Examples of other negative electrode materials include materials having at least one of a metal element and a metalloid element as constituent elements (except for those corresponding to the above-described high potential materials). This is because a high energy density can be obtained. Such a negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, and may have one or two or more phases thereof at least in part. In addition, the “alloy” in the present invention includes an alloy having one or more metal elements and one or more metalloid elements in addition to one composed of two or more metal elements. Further, the “alloy” may have a nonmetallic element. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a material in which two or more of them coexist.

  Examples of the metal element or metalloid element described above include a metal element or metalloid element capable of forming an alloy with lithium ions. Specifically, magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon (Si), 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). Among these, at least one of silicon and tin is preferable, and silicon is more preferable. This is because a high energy density can be obtained because of its large ability to occlude and release lithium-on.

  Examples of the material having at least one of silicon and tin include, for example, a simple substance, an alloy or a compound of silicon, a simple substance, an alloy or a compound of tin, or one or two or more phases thereof. The material which has is mentioned.

Examples of silicon alloys include, as constituent elements other than silicon, at least one of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), and chromium. The thing which has a seed is mentioned. Examples of the silicon compound include those having oxygen or carbon (C), and may have a constituent element other than the above-described silicon. Examples of silicon alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi. ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), Or LiSiO etc. are mentioned.

As an alloy of tin, for example, as a constituent element other than tin, at least one of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium is included. Things. Examples of tin compounds include those having oxygen or carbon, and may contain constituent elements other than tin described above. Examples of tin alloys or compounds include SnSiO ₃ , LiSnO, or Mg ₂ Sn.

  In particular, as a material having at least one of silicon and tin, for example, a material having tin as the first constituent element and second and third constituent elements in addition to it is preferable. The second constituent elements are cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum, silver, indium, cerium (Ce), It is at least one of hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one of boron, carbon, aluminum, and phosphorus (P). This is because having the second and third constituent elements improves the cycle characteristics.

  Among them, it has tin, cobalt and carbon, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is 30 mass% or more. An SnCoC-containing material that is 70% by mass or less is preferable. This is because a high energy density can be obtained in such a composition range.

  This SnCoC-containing material may further contain other constituent elements as necessary. Examples of such other constituent elements include silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, and bismuth. Good. This is because a higher effect can be obtained.

  The SnCoC-containing material has a phase containing tin, cobalt, and carbon, and the phase is preferably a low crystalline or amorphous phase. This phase is a reaction phase capable of reacting with lithium, and excellent cycle characteristics can be obtained due to the presence of the reaction phase. The half width of the diffraction peak obtained by X-ray diffraction of this phase is 1.0 ° or more at a diffraction angle 2θ when CuKα ray is used as the specific X-ray and the drawing speed is 1 ° / min Is preferred. This is because lithium ions are occluded and released more smoothly and the reactivity with the electrolyte is reduced.

  In addition to this SnCoC-containing material, a SnCoFeC-containing material having tin, cobalt, iron and carbon is also preferable. The composition of the SnCoFeC-containing material can be arbitrarily set. For example, as a composition when the iron content is set to be small, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the iron content is 0.3 mass% or more and 5.9 mass%. % Or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is preferably 30% by mass or more and 70% by mass or less. In addition, for example, as a composition when the content of iron is set to be large, the content of carbon is 11.9 mass% or more and 29.7 mass% or less, and cobalt and iron with respect to the total of tin, cobalt, and iron The total ratio of (Co + Fe) / (Sn + Co + Fe)) is 26.4 mass% to 48.5 mass%, and the ratio of cobalt to the total of cobalt and iron (Co / (Co + Fe)) is 9.9 mass% It is preferable that it is 79.5 mass% or less. This is because a high energy density can be obtained in such a composition range. The physical properties and the like of this SnCoFeC-containing material are the same as those of the above-described SnCoC-containing material.

  Furthermore, examples of other negative electrode materials include metal oxides and polymer compounds. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  Of course, the negative electrode material capable of inserting and extracting lithium ions may be other than the above. Further, two or more kinds of the series of negative electrode materials may be mixed in any combination.

  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 made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic. The separator 23 may be a laminate of two or more porous films.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains a solvent and an electrolyte salt dissolved in the solvent.

  As the solvent used in combination with the negative electrode active material (high potential material), any one or two or more of carbonic acid esters having two or more halogens as constituent elements is preferable. This is because a favorable film is more likely to be formed on the surface of the negative electrode 22 as compared to the case of using a carbonate ester having one halogen as a constituent element or a cyclic carbonate ester having an unsaturated carbon bond. Thereby, at the time of charging / discharging, the decomposition reaction of the electrolyte is suppressed, and the acceptability of lithium ions in the negative electrode 22 is improved.

  Specifically, when a high-potential material is used as the negative electrode active material, the use of the above-described carbonic acid ester having one halogen is difficult to reduce and decompose during charge and discharge. Is difficult to form. On the other hand, when a carbonate ester having two or more halogens is used, the reductive decomposition potential is high, so that even when a high potential material is used as the negative electrode active material, a film is easily formed on the surface of the negative electrode 22. Become.

  The carbonate ester having two or more halogens may be either a cyclic carbonate ester or a chain carbonate ester, and among them, a cyclic carbonate ester is preferable. This is because a film is easily formed on the surface of the negative electrode 22 because it is easily reduced and decomposed during charging and discharging.

  The type of halogen is not particularly limited, but among these, fluorine is preferable. This is because a strong and stable film is easily formed on the surface of the negative electrode 22. Further, the number of halogens is not particularly limited as long as it is 2 or more, but 2 is preferable among them, and in that case, it is more preferable that the types of halogens are the same. This is because chemical synthesis is easy and sufficient film-forming ability can be obtained.

  Among cyclic carbonates having two or more halogens, those having fluorine as the halogen include, for example, 4,5-difluoro-1,3-dioxolan-2-one, 4-fluoro-5-difluoro-1, 3-dioxolan-2-one, tetrafluoro-1,3-dioxolan-2-one, etc. are mentioned. Among these, 4,5-difluoro-1,3-dioxolan-2-one is preferable.

  Among chain carbonic acid esters having two or more halogens, those having fluorine as the halogen include, for example, bis (fluoromethyl) carbonate or difluoromethyl methyl carbonate.

  Of course, the cyclic carbonate or chain carbonate having two or more halogens may be other than the above.

  The content of the carbonic acid ester having two or more halogens in the solvent is not particularly limited, but is preferably 0.01% by weight or more and 10% by weight or less. This is because a good film is formed on the surface of the negative electrode 22 without greatly reducing the battery capacity.

  In addition, as long as the solvent contains the above-mentioned carbonate ester having two or more halogens, it may contain other solvents.

  As such other solvents, for example, as described below, one or more of non-aqueous solvents such as organic solvents (excluding those corresponding to the above-described carbonate having two or more halogens) ). Note that a series of other solvents described below may be arbitrarily combined.

  Specifically, examples of other solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxy. Ethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, Ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethyl acetate, ethyl trimethyl acetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidi Non, N-methyloxazolidinone, N, N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide and the like.

  Among these, at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is preferable. In this case, a high viscosity (high dielectric constant) solvent such as ethylene carbonate or propylene carbonate (for example, a relative dielectric constant ε ≧ 30) and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate (for example, viscosity ≦ 1 mPas). -A combination with s) is more preferred. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.

  Moreover, as another solvent, the cyclic carbonate which has an unsaturated carbon bond represented by Formula (1)-Formula (3) is mentioned.

（Ｒ１１およびＲ１２は水素基あるいはアルキル基である。）

(R11 and R12 are a hydrogen group or an alkyl group.)

（Ｒ１３〜Ｒ１６は水素基、アルキル基、ビニル基あるいはアリル基であり、それらのうちの少なくとも１つはビニル基あるいはアリル基である。）

(R13 to R16 are a hydrogen group, an alkyl group, a vinyl group or an allyl group, and at least one of them is a vinyl group or an allyl group.)

（Ｒ１７はアルキレン基である。）

(R17 is an alkylene group.)

  The cyclic carbonate having an unsaturated carbon bond shown in the formula (1) is a vinylene carbonate compound. Examples of the vinylene carbonate compound include vinylene carbonate (1,3-dioxol-2-one), methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), and ethyl vinylene carbonate (4-ethyl). -1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1, Examples include 3-dioxol-2-one and 4-trifluoromethyl-1,3-dioxol-2-one.

  The cyclic carbonate having an unsaturated carbon bond shown in Formula (2) is a vinyl ethylene carbonate compound. Examples of the vinyl carbonate-based compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, and 4-ethyl. -4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolane-2 -One, 4,4-divinyl-1,3-dioxolan-2-one, 4,5-divinyl-1,3-dioxolan-2-one and the like. Of course, as R13 to R16, all may be vinyl groups, all may be allyl groups, or vinyl groups and allyl groups may be mixed.

  The cyclic carbonate having an unsaturated carbon bond represented by the formula (3) is a methylene ethylene carbonate compound. Examples of the methylene ethylene carbonate compound include 4-methylene-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5. -Methylene-1,3-dioxolan-2-one and the like. As this methylene ethylene carbonate compound, there may be one having two methylene groups in addition to one having one methylene group (compound shown in Formula (3)).

  The cyclic carbonate having an unsaturated carbon bond may be catechol carbonate (catechol carbonate) having a benzene ring in addition to those shown in the formulas (1) to (3).

  Examples of the other solvent include a chain carbonate ester having a halogen represented by the formula (4) as a constituent element and a cyclic carbonate ester having a halogen represented by the formula (5) as a constituent element.

（Ｒ２１〜Ｒ２６は水素基、ハロゲン基、アルキル基あるいはハロゲン化アルキル基であり、それらのうちの１つはハロゲン基あるいはハロゲン化アルキル基である。）

(R21 to R26 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and one of them is a halogen group or a halogenated alkyl group.)

（Ｒ２７〜Ｒ３０は水素基、ハロゲン基、アルキル基あるいはハロゲン化アルキル基であり、それらのうちの１つはハロゲン基あるいはハロゲン化アルキル基である。）

(R27 to R30 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and one of them is a halogen group or a halogenated alkyl group.)

  R21 to R26 in Formula (4) may be the same or different. The same applies to R27 to R30 in the formula (5). Further, the type of halogen is not particularly limited, but among them, fluorine is preferable.

  Examples of the chain carbonate having a halogen represented by the formula (4) include fluoromethyl methyl carbonate. Examples of the cyclic carbonate represented by the halogen represented by the formula (5) include 4-fluoro-1,3-dioxolan-2-one and 4-chloro-1,3-dioxolan-2-one.

  Furthermore, examples of other solvents include sultone (cyclic sulfonic acid ester) and acid anhydrides.

  The sultone is, for example, propane sultone or propene sultone. Although content of sultone in a solvent is not specifically limited, For example, it is preferable that they are 0.5 weight% or more and 5 weight% or less.

  Examples of the acid anhydride include a carboxylic acid anhydride, a disulfonic acid anhydride, and an anhydride of a carboxylic acid and a sulfonic acid. Examples of the carboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride. Examples of the disulfonic anhydride include ethane disulfonic anhydride and propane disulfonic anhydride. Examples of the anhydride of carboxylic acid and sulfonic acid include anhydrous sulfobenzoic acid, anhydrous sulfopropionic acid, and anhydrous sulfobutyric acid. The content of the acid anhydride in the solvent is not particularly limited, but is preferably 0.5% by weight or more and 5% by weight or less, for example.

  For example, as described below, the electrolyte salt contains one or more light metal salts such as lithium salts. Note that a series of lithium salts described below may be arbitrarily combined.

Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), tetra Lithium phenylborate (LiB (C ₆ H ₅ ) ₄ ), lithium methanesulfonate (LiCH ₃ SO ₃ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium tetrachloroaluminate (LiAlCl ₄ ), hexafluoride Examples thereof include dilithium silicate (Li ₂ SiF ₆ ), lithium chloride (LiCl), and lithium bromide (LiBr).

  Among these, at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate is preferable, and lithium hexafluorophosphate is more preferable. This is because a higher effect can be obtained because the internal resistance is lowered.

  Moreover, as lithium salt, the compound represented by Formula (6)-Formula (8) is mentioned, for example. In addition, R31 and R33 of Formula (6) may be the same or different. The same applies to R41 to R43 in formula (7) and R51 and R52 in formula (8).

（Ｘ３１は長周期型周期表における１族元素あるいは２族元素、またはアルミニウムである。Ｍ３１は遷移金属元素、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｒ３１はハロゲン基である。Ｙ３１は−（Ｏ＝）Ｃ−Ｒ３２−Ｃ（＝Ｏ）−、−（Ｏ＝）Ｃ−Ｃ（Ｒ３３）₂ −あるいは−（Ｏ＝）Ｃ−Ｃ（＝Ｏ）−である。ただし、Ｒ３２はアルキレン基、ハロゲン化アルキレン基、アリーレン基あるいはハロゲン化アリーレン基である。Ｒ３３はアルキル基、ハロゲン化アルキル基、アリール基あるいはハロゲン化アリール基である。なお、ａ３は１〜４の整数であり、ｂ３は０、２あるいは４であり、ｃ３、ｄ３、ｍ３およびｎ３は１〜３の整数である。）

(X31 is a group 1 element or group 2 element in the long-period periodic table, or aluminum. M31 is a transition metal element, or a group 13 element, group 14 element, or group 15 element in the long-period periodic table. R31 Y31 is — (O═) C—R32—C (═O) —, — (O═) C—C (R33) ₂ — or — (O═) C—C (═O) Where R32 is an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group, R33 is an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, and a3 is (It is an integer of 1 to 4, b3 is 0, 2 or 4, and c3, d3, m3 and n3 are integers of 1 to 3.)

（Ｘ４１は長周期型周期表における１族元素あるいは２族元素である。Ｍ４１は遷移金属元素、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｙ４１は−（Ｏ＝）Ｃ−（Ｃ（Ｒ４１）₂ ）_b4−Ｃ（＝Ｏ）−、−（Ｒ４３）₂ Ｃ−（Ｃ（Ｒ４２）₂ ）_c4−Ｃ（＝Ｏ）−、−（Ｒ４３）₂ Ｃ−（Ｃ（Ｒ４２）₂ ）_c4−Ｃ（Ｒ４３）₂ −、−（Ｒ４３）₂ Ｃ−（Ｃ（Ｒ４２）₂ ）_c4−Ｓ（＝Ｏ）₂ −、−（Ｏ＝）₂ Ｓ−（Ｃ（Ｒ４２）₂ ）_d4−Ｓ（＝Ｏ）₂ −あるいは−（Ｏ＝）Ｃ−（Ｃ（Ｒ４２）₂ ）_d4−Ｓ（＝Ｏ）₂ −である。ただし、Ｒ４１およびＲ４３は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基であり、それぞれのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。Ｒ４２は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基である。なお、ａ４、ｅ４およびｎ４は１あるいは２であり、ｂ４およびｄ４は１〜４の整数であり、ｃ４は０〜４の整数であり、ｆ４およびｍ４は１〜３の整数である。）

(X41 is a group 1 element or group 2 element in the long periodic table. M41 is a transition metal element, or a group 13, element or group 15 element in the long period periodic table. Y41 is − ( O =) C- (C (R41 ) 2) b4 -C (= O) -, - (R43) 2 C- (C (R42) 2) c4 -C (= O) -, - (R43) 2 C -(C (R42) ₂ ) _c4 -C (R43) ₂ -,-(R43) ₂ C- (C (R42) ₂ ) _c4 -S (= O) ₂ -,-(O =) ₂ S- ( C (R42) ₂ ) _d4- S (= O) _2- or-(O =) C- (C (R42) ₂ ) _d4- S (= O) _2- where R41 and R43 are hydrogen groups. , An alkyl group, a halogen group, or a halogenated alkyl group, and at least one of each is a halogen group or a halogenated alkyl group. R42 is a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, wherein a4, e4 and n4 are 1 or 2, b4 and d4 are integers of 1 to 4, and c4 Is an integer from 0 to 4, and f4 and m4 are integers from 1 to 3.)

（Ｘ５１は長周期型周期表における１族元素あるいは２族元素である。Ｍ５１は遷移金属元素、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｒｆはフッ素化アルキル基あるいはフッ素化アリール基であり、いずれの炭素数も１〜１０である。Ｙ５１は−（Ｏ＝）Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｃ（＝Ｏ）−、−（Ｒ５２）₂ Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｃ（＝Ｏ）−、−（Ｒ５２）₂ Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｃ（Ｒ５２）₂ −、−（Ｒ５２）₂ Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｓ（＝Ｏ）₂ −、−（Ｏ＝）₂ Ｓ−（Ｃ（Ｒ５１）₂ ）_e5−Ｓ（＝Ｏ）₂ −あるいは−（Ｏ＝）Ｃ−（Ｃ（Ｒ５１）₂ ）_e5−Ｓ（＝Ｏ）₂ −である。ただし、Ｒ５１は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基である。Ｒ５２は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基であり、そのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。なお、ａ５、ｆ５およびｎ５は１あるいは２であり、ｂ５、ｃ５およびｅ５は１〜４の整数であり、ｄ５は０〜４の整数であり、ｇ５およびｍ５は１〜３の整数である。）

(X51 is a group 1 element or group 2 element in the long-period periodic table. M51 is a transition metal element, or a group 13, element or group 15 element in the long-period periodic table. Rf is fluorinated. An alkyl group or a fluorinated aryl group, each having 1 to 10 carbon atoms Y51 is — (O═) C— (C (R51) ₂ ) _d5 —C (═O) —, — (R52); ₂ C- (C (R51) ₂ ) _d5 -C (= O)-,-(R52) ₂ C- (C (R51) ₂ ) _d5 -C (R52) ₂ -,-(R52) ₂ C- ( _{C (R51) 2) d5 -S} (= O) 2 -, - (O =) 2 S- (C (R51) 2) e5 -S (= O) 2 - or - (O =) C- (C _{(R51) 2) e5 -S (} = O) 2 -. is, however, R51 is a hydrogen group, an alkyl group, a halogen group, or a halogen Kaa R52 is a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, at least one of which is a halogen group or a halogenated alkyl group, wherein a5, f5 and n5 are 1 or 2; B5, c5 and e5 are integers of 1 to 4, d5 is an integer of 0 to 4, and g5 and m5 are integers of 1 to 3.)

  The long-period periodic table is represented by a revised inorganic chemical nomenclature proposed by IUPAC (International Pure and Applied Chemistry Association). Group 1 elements are hydrogen, lithium, sodium, potassium, rubidium, cesium and francium. Group 2 elements are beryllium, magnesium, calcium, strontium, barium and radium. Group 13 elements are boron, aluminum, gallium, indium and thallium. Group 14 elements are carbon, silicon, germanium, tin and lead. Group 15 elements are nitrogen, phosphorus, arsenic, antimony and bismuth.

  Examples of the compound represented by the formula (6) include compounds represented by the formula (6-1) to the formula (6-6). Examples of the compound represented by formula (7) include compounds represented by formula (7-1) to formula (7-8). Examples of the compound represented by the formula (8) include a compound represented by the formula (8-1). Of course, the compounds shown in the formulas (6) to (8) may be other than those described above.

  Furthermore, as lithium salt, the compound represented by Formula (9)-Formula (11) is mentioned. In addition, m and n in Formula (9) may be the same or different. The same applies to p, q and r in the formula (11).

（ｍおよびｎは１以上の整数である。）

(M and n are integers of 1 or more.)

（Ｒ６１は炭素数が２以上４以下の直鎖状あるいは分岐状のパーフルオロアルキレン基である。）

(R61 is a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

（ｐ、ｑおよびｒは１以上の整数である。）

(P, q and r are integers of 1 or more.)

Examples of the chain compound represented by the formula (9) include bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ ), bis (pentafluoroethanesulfonyl) imide lithium (LiN (C ₂ F) ₅ SO ₂ ) ₂ ), (trifluoromethanesulfonyl) (pentafluoroethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ )), (trifluoromethanesulfonyl) (heptafluoropropanesulfonyl) imide Lithium (LiN (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ )) or (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl) imidolithium (LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ )) Etc.

  Examples of the cyclic compound represented by Formula (10) include compounds represented by Formula (10-1) to Formula (10-4). That is, 1,2-perfluoroethane disulfonylimide lithium, 1,3-perfluoropropane disulfonylimide lithium, 1,3-perfluorobutane disulfonylimide lithium, or 1,4-perfluorobutane disulfonylimide lithium Etc.

Examples of the chain compound represented by the formula (11) include lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ).

  The content of the electrolyte salt is preferably, for example, 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because high ionic conductivity is obtained.

  In this secondary battery, at the time of charging, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. On the other hand, at the time of discharging, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution impregnated in the separator 23.

  This secondary battery is manufactured by the following procedure, for example.

  First, the positive electrode 21 is produced. First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed to form a positive electrode mixture, and then dispersed in an organic solvent to obtain a paste-like positive electrode mixture slurry. Subsequently, the cathode mixture slurry is uniformly applied to both surfaces of the cathode current collector 21A using a doctor blade or a bar coater, and then the organic solvent is volatilized to form the cathode active material layer 21B. Finally, the positive electrode active material layer 21B is compression-molded using a roll press or the like while being heated as necessary. In this case, compression molding may be repeated a plurality of times.

  Next, the negative electrode 22 is produced by the same procedure as that of the positive electrode 21 described above. First, a negative electrode mixture obtained by mixing a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent is dispersed in an organic solvent to obtain a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is uniformly applied to both surfaces of the negative electrode current collector 22A using a doctor blade or the like, and then the organic solvent is volatilized to form the negative electrode active material layer 22B. Finally, the positive electrode active material layer 22B is compression-molded using a roll press or the like while being heated as necessary.

  The secondary battery is assembled as follows. First, the positive electrode lead 25 is attached to the positive electrode 21 by welding or the like, and the negative electrode lead 26 is attached to the negative electrode 22 by welding or the like. Subsequently, the positive electrode 21 and the negative electrode 22 are stacked and wound via the separator 23 to produce the wound electrode body 20. Subsequently, the center pin 24 is inserted into the winding center of the wound electrode body 20. Subsequently, the wound electrode body 20 is accommodated in the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13. In this case, the tip of the positive electrode lead 25 is connected to the safety valve mechanism 25 by welding or the like, and the tip of the negative electrode lead 26 is connected to the battery can 11 by welding or the like. Subsequently, an electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. Finally, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end portion of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  According to the secondary battery according to the present embodiment, the negative electrode 22 and the electrolytic solution have the following configuration. The negative electrode active material of the negative electrode 22 includes a negative electrode material that occludes and releases lithium ions at a potential of 1.0 V or more with respect to the lithium potential. Further, the solvent of the electrolytic solution contains a carbonate ester having two or more halogens as constituent elements. That is, in this embodiment, a negative electrode material (high potential material) that requires a high potential in order to occlude and release lithium ions and a solvent having a high reductive decomposition potential are used in combination. In this case, compared with the case where a solvent having a low reductive decomposition potential (such as a carbonate having one halogen as a constituent element) is used, even when a high potential material is used as the negative electrode active material, the surface of the negative electrode 22 A film is easily formed on the surface. Thereby, at the time of charging / discharging, the decomposition reaction of the electrolytic solution is suppressed, and the acceptability of lithium ions in the negative electrode 22 is improved. Therefore, cycle characteristics and charge load characteristics can be improved.

  In particular, when the content of the carbonate having two or more halogens in the solvent is 0.01% by weight or more and 10% by weight or less, a high effect can be obtained.

[2. Second Embodiment]
FIG. 3 shows an exploded perspective configuration of the secondary battery according to the second embodiment of the present invention, and FIG. 4 shows an enlarged cross-sectional configuration along the line IV-IV shown in FIG. ing.

  This secondary battery is a lithium ion secondary battery as in the first embodiment described above, and is mainly a winding in which the positive electrode lead 31 and the negative electrode lead 32 are attached inside the film-shaped exterior member 40. The rotating electrode body 30 is accommodated. A battery structure using such a film-shaped exterior member 40 is called a laminate film type.

  For example, the positive electrode lead 31 and the negative electrode lead 32 are led out in the same direction from the inside of the exterior member 40 toward the outside. However, the installation position of the positive electrode lead 31 and the negative electrode lead 32 with respect to the spirally wound electrode body 30, the lead-out direction thereof, and the like are not particularly limited. The positive electrode lead 31 is made of, for example, aluminum, and the negative electrode lead 32 is made of, for example, copper, nickel, stainless steel, or the like. These materials have, for example, a thin plate shape or a mesh shape.

  The exterior member 40 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order. In this case, for example, the outer edges of the fusion layers of the two films are bonded together by an adhesive or the like so that the fusion layer faces the wound electrode body 30. The fusion layer is, for example, a film of polyethylene or polypropylene. The metal layer is, for example, a metal foil such as aluminum. The surface protective layer is, for example, a film such as nylon or polyethylene terephthalate.

  Among these, as the exterior member 40, an aluminum laminated film in which a polyethylene film, an aluminum foil, and a nylon film are laminated in this order is preferable. However, the exterior member 40 may be a laminated film having another laminated structure instead of the above-described aluminum laminated film, or may be a polymer film such as polypropylene or a metal film.

  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. Examples of such a material include polyolefin resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

  The wound electrode body 30 is formed by laminating and winding a positive electrode 33 and a negative electrode 34 via a separator 35 and an electrolyte layer 36, and an outermost peripheral portion thereof is protected by a protective tape 37.

  In the positive electrode 33, for example, a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A having a pair of surfaces. In the negative electrode 34, for example, a negative electrode active material layer 34B is provided on both surfaces of a negative electrode current collector 34A having a pair of surfaces. The configuration 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 is the same as that of the positive electrode current collector 21A, the positive electrode active material layer in the first embodiment described above. The configurations of 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23 are the same.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound that holds the electrolytic solution, and is a so-called gel electrolyte. A gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and leakage of the electrolyte is prevented.

  Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl fluoride, polyvinyl acetate, polyvinyl alcohol, poly Examples thereof include methyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, polycarbonate, and a copolymer of vinylidene fluoride and hexafluoropyrene. These may be single and multiple types may be mixed. Among these, polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropyrene is preferable. This is because it is electrochemically stable.

  The composition of the electrolytic solution is the same as the composition of the electrolytic solution in the first embodiment described above. However, in the electrolyte layer 36 which is a gel electrolyte, the solvent of the electrolytic solution is a wide concept including not only a liquid solvent but also a material having ion conductivity capable of dissociating the electrolyte salt. Accordingly, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

  Instead of the gel electrolyte layer 36 in which the electrolytic solution is held by the polymer compound, the electrolytic solution may be used as it is. In this case, the separator 35 is impregnated with the electrolytic solution.

  In this secondary battery, at the time of charging, for example, lithium ions are released from the positive electrode 33 and inserted in the negative electrode 34 through the electrolyte layer 36. On the other hand, at the time of discharge, for example, lithium ions are released from the negative electrode 34 and inserted into the positive electrode 33 through the electrolyte layer 36.

  The secondary battery provided with the gel electrolyte layer 36 is manufactured by, for example, the following three types of procedures.

  In the first manufacturing method, first, for example, the positive electrode 33 and the negative electrode 34 are produced by the same procedure as the positive electrode 21 and the negative electrode 22 in the first embodiment described above. That is, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A to produce the positive electrode 33, and the negative electrode active material layer 34B is formed on both surfaces of the negative electrode current collector 34A to produce the negative electrode 34. Then, after preparing the precursor solution containing electrolyte solution, a high molecular compound, and a solvent and apply | coating to the positive electrode 33 and the negative electrode 34, the solvent is volatilized and the gel-like electrolyte layer 36 is formed. Subsequently, the positive electrode lead 31 is attached to the positive electrode 33 by welding or the like, and the negative electrode lead 32 is attached to the negative electrode 34 by welding or the like. Subsequently, after laminating and winding the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed via the separator 35, the protective electrode 37 is adhered to the outermost peripheral portion thereof, whereby the wound electrode body 30 is formed. Make it. Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, the outer edge portions of the exterior member 40 are bonded to each other by heat fusion or the like, whereby the wound electrode body 30 is enclosed. At this 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.

  In the second manufacturing method, first, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 32 is attached to the negative electrode 34. Subsequently, after the positive electrode 33 and the negative electrode 34 are stacked and wound via the separator 35, a protective tape 37 is adhered to the outermost peripheral portion thereof, whereby a wound body that is a precursor of the wound electrode body 30. Is made. Subsequently, after sandwiching the wound body between the two film-like exterior members 40, the remaining outer peripheral edge portion excluding the outer peripheral edge portion on one side is adhered by heat fusion or the like, thereby The wound body is accommodated in the exterior member 40. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and a bag-shaped exterior member After injecting into the inside of 40, the opening part of the exterior member 40 is sealed by heat sealing or the like. Finally, the gel electrolyte layer 36 is formed by thermally polymerizing the monomer to obtain a polymer compound. Thereby, the secondary battery is completed.

  In the third manufacturing method, a wound body is formed by forming a wound body in the same manner as in the second manufacturing method described above except that the separator 35 coated with the polymer compound on both sides is used first. 40 is housed inside. Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, or a multi-component copolymer. Specifically, polyvinylidene fluoride, a binary copolymer containing vinylidene fluoride and hexafluoropropylene as components, and a ternary copolymer containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence. In addition, the high molecular compound may contain the other 1 type, or 2 or more types of high molecular compound with the polymer which uses the above-mentioned vinylidene fluoride as a component. Subsequently, after the electrolytic solution is prepared and injected into the exterior member 40, the opening of the exterior member 40 is sealed by heat sealing or the like. Finally, the exterior member 40 is heated while applying a load, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. As a result, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte layer 36, thereby completing the secondary battery.

  In the third manufacturing method, the swollenness of the secondary battery is suppressed as compared with the first manufacturing method. Further, in the third manufacturing method, compared to the second manufacturing method, the monomer or solvent that is a raw material of the polymer compound hardly remains in the electrolyte layer 36, and the polymer compound forming process is excellent. Be controlled. Thereby, sufficient adhesion is obtained between the positive electrode 33, the negative electrode 34 and the separator 35 and the electrolyte layer 36.

  According to the secondary battery of the present embodiment, the negative electrode 34 and the electrolytic solution have the same configuration as the negative electrode 22 and the electrolytic solution in the first embodiment described above, respectively, so that the cycle characteristics and the charging load are Characteristics can be improved. Other effects relating to the secondary battery are the same as those of the first embodiment.

  Examples of the present invention will be described in detail.

(Experimental Examples 1-1 to 1-6)
The laminate film type lithium ion secondary battery shown in FIGS. 3 and 4 was produced by the following procedure.

First, the positive electrode 33 was produced. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a molar ratio of 0.5: 1, and then calcined in air at 900 ° C. for 5 hours. A cobalt composite oxide (LiCoO ₂ ) was obtained. Subsequently, by mixing 98 parts by mass of lithium cobalt composite oxide as a positive electrode active material, 1.2 parts by mass of polyvinylidene fluoride as a positive electrode binder, and 0.8 parts by mass of ketjen black as a positive electrode conductive agent. A positive electrode mixture was obtained. Subsequently, the positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode active material layer 33B was formed by uniformly applying and drying the positive electrode mixture slurry on both surfaces of the positive electrode current collector 33A using a bar coater. In this case, a strip-shaped aluminum foil (thickness = 12 μm) was used as the positive electrode current collector 33A. Finally, the positive electrode active material layer 33B was compression molded using a roll press.

Next, the negative electrode 34 was produced. First, by mixing 85 parts by mass of lithium titanate (Li ₄ Ti ₅ O ₁₂ ) as the negative electrode active material, 5 parts by mass of polyvinylidene fluoride as the negative electrode binder, and 10 parts by mass of graphite as the negative electrode conductive agent. A negative electrode mixture was prepared. Subsequently, the negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. Subsequently, the negative electrode active material layer 34B was formed by uniformly applying and drying the negative electrode mixture slurry on both surfaces of the negative electrode current collector 34A using a bar coater. In this case, a strip-shaped electrolytic copper foil (thickness = 18 μm) was used as the negative electrode current collector 34A. Finally, the negative electrode active material layer 34B was compression molded using a roll press.

  Next, an electrolytic solution was prepared. First, as a solvent, ethylene carbonate (EC), dimethyl carbonate (DMC), and γ-butyrolactone (GBL) were mixed in a predetermined combination. Subsequently, 4,5-difluoro-1,3-dioxolan-2-one (DFEC), which is a carbonate ester having two or more halogens as constituent elements, was added to the above solvent as another solvent. Finally, lithium hexafluorophosphate as an electrolyte salt was dissolved in the above mixed solvent. In this case, the mixing ratio (weight ratio) of the solvent and the addition amount (wt%) of the other solvent are set as shown in Table 1, and the content of the electrolyte salt is 1 mol / kg with respect to the solvent. did.

  Finally, a secondary battery was assembled using the electrolytic solution together with the positive electrode 33 and the negative electrode 34. First, the positive electrode lead 31 made of aluminum was welded to one end of the positive electrode current collector 33A, and the negative electrode lead 32 made of nickel was welded to one end of the negative electrode current collector 34A. Subsequently, the positive electrode 33, the separator 35, and the negative electrode 34 are laminated in this order and then wound in the longitudinal direction. A wound body that is a precursor of the body 30 was formed. In this case, a microporous polyethylene film (thickness = 20 μm) was used as the separator 35. Subsequently, after the wound body was sandwiched between the exterior members 40, the wound body was accommodated inside the bag-shaped exterior member 40 by heat-sealing the outer edges except for one side. In this case, as the exterior member 40, three layers in which a nylon film (thickness = 30 μm), an aluminum foil (thickness = 40 μm), and an unstretched polypropylene film (thickness = 30 μm) are laminated from the outside. A laminate film having a structure (total thickness = 100 μm) was used. Subsequently, the wound electrode body 30 was manufactured by injecting an electrolytic solution from the opening of the exterior member 40 and impregnating the separator 35. Finally, the secondary battery was completed by thermally sealing and sealing the opening of the exterior member 40 in a vacuum atmosphere. When manufacturing the secondary battery, the thickness of the positive electrode active material layer 33B was adjusted so that lithium metal was not deposited on the negative electrode 34 during full charge.

(Experimental Examples 1-7 to 1-9)
Except that the composition of the electrolytic solution was set as shown in Table 1, the same procedure as in Experimental Examples 1-1 to 1-6 was performed. Specifically, DFEC was not used as the other solvent. As another solvent, instead of DFEC, 4-fluoro-1,3-dioxolan-2-one (FEC), which is a carbonate having one halogen as a constituent element, or cyclic carbonic acid having an unsaturated carbon bond The ester vinylene carbonate (VC) was used.

  When the cycle characteristics and the charge load characteristics of the secondary batteries of Examples 1-1 to 1-9 were examined, the results shown in Table 1 were obtained.

  When examining the cycle characteristics, the following cycle test was performed to determine the discharge capacity retention rate after 1000 cycles. First, in order to stabilize the battery state, the battery was charged and discharged for 1 cycle in an atmosphere at 23 ° C. Subsequently, the second cycle discharge capacity was measured by charging and discharging again in the same atmosphere. Subsequently, the discharge capacity at the 1000th cycle was measured by repeating charging and discharging until the total number of cycles reached 1000 in the same atmosphere. Finally, discharge capacity retention ratio (%) = (discharge capacity at 1000th cycle / discharge capacity at 2nd cycle) × 100 was calculated. At this time, in the first cycle, the battery is charged at a constant current of 100 mA until the battery voltage reaches 2.8 V, and subsequently charged at a constant voltage of 2.8 V until the total charging time reaches 6 hours. The battery was discharged at a constant current until the battery voltage reached 1V. In the second and subsequent cycles, the battery is charged at a constant current of 3C until the battery voltage reaches 2.8V, and subsequently charged at a constant voltage of 2.8V until the current reaches 25 mA. The battery was discharged until the voltage reached 1V.

  When investigating the charge load characteristics, the following charge load test was performed on one secondary battery to obtain the discharge capacity maintenance rate during load charging. First, the reference discharge capacity was measured by charging and discharging under the conditions of the second cycle in the cycle test described above. Subsequently, charging is performed until the battery voltage reaches 2.8 V with a charging current of 1 C, charging is continued until the current reaches 25 mA at a constant voltage of 2.8 V, and then the battery voltage is 1 V with a constant current of 0.2 C. The discharge capacity at the time of 1C charge was measured by discharging until it reached. From this result, the discharge capacity retention ratio (%) at 1C charge = (discharge capacity at 1C charge / reference discharge capacity) × 100 was calculated. Subsequently, except that the charge current was changed to 5C, the discharge capacity at the time of 5C charge was measured by charging and discharging under the same conditions as at the time of 1C charge, and then the discharge capacity maintenance rate (%) at the time of 5C charge = (Discharge capacity at 5C charge / reference discharge capacity) × 100 was calculated. Subsequently, except that the charging current was changed to 10 C, the discharge capacity at the time of 10 C charging was measured by charging and discharging under the same conditions as those at the time of 1 C charging, and then the discharge capacity maintenance rate (%) at the time of 10 C charging. = (Discharge capacity at 10 C charge / reference discharge capacity) × 100 was calculated. Finally, except that the charging current was changed to 20C, the discharge capacity at the time of 20C charging was measured by charging and discharging under the same conditions as those at the time of 1C charging, and then the discharge capacity maintenance rate (%) at the time of 20C charging. = (Discharge capacity at 20 C charge / reference discharge capacity) × 100 was calculated.

As shown in Table 1, when a high potential material (Li ₄ Ti ₅ O ₁₂ ) is used as the negative electrode active material, there is a difference in the discharge capacity maintenance ratio depending on the type of other solvent contained in the electrolytic solution. It was seen. Specifically, in Experimental Examples 1-1 to 1-6 including DFEC, compared to Experimental Examples 1-7 to 1-9 including VC or FEC, the results do not depend on the composition of the solvent and the content of DFEC. In addition, the discharge capacity retention rate after 1000 cycles and during load charging increased. In particular, in Experimental Examples 1-1 to 1-6, when the content of DFEC was 0.01 wt% or more and 10 wt% or less, both discharge capacity retention rates were higher.

  From these facts, in the secondary battery of the present invention, when the negative electrode active material of the negative electrode contains a high potential material, the solvent of the electrolyte solution contains a carbonate ester having two or more halogens as constituent elements. It was confirmed that the characteristics and charging load characteristics were improved. It was also confirmed that when the content of the carbonic acid ester having two or more halogens in the solvent is 0.01 wt% or more and 10 wt% or less, both characteristics are further improved.

  The present invention has been described with reference to some embodiments and examples. However, the present invention is not limited to the modes described in the above embodiments and examples, and various modifications are possible. For example, in each of the above-described embodiments and examples, the secondary battery in which the capacity of the negative electrode is expressed by the insertion and extraction of lithium ions is described as the type of the secondary battery, but is not necessarily limited thereto. . The secondary battery of the present invention also includes a secondary battery in which the capacity of the negative electrode includes a capacity due to insertion and extraction of lithium ions and a capacity due to precipitation and dissolution of lithium, and is expressed by the sum of these capacities. It is applicable to. In this secondary battery, a negative electrode material capable of inserting and extracting lithium ions is used as the negative electrode active material, and the chargeable capacity of the negative electrode material is set to be smaller than the discharge capacity of the positive electrode. .

  In each of the above embodiments and examples, the case where the battery structure is a cylindrical type or a laminate film type and the case where the battery element has a winding structure have been described as examples. However, the present invention is not necessarily limited thereto. It is not a thing. The secondary battery of the present invention can be similarly applied to a case where the battery has another battery structure such as a square shape, a coin shape or a button shape, and a case where the battery element has another structure such as a laminated structure.

  In each of the above-described embodiments and examples, the appropriate range derived from the results of the examples is described for the content of carbonate ester having two or more halogens as constituent elements in the secondary battery of the present invention. ing. However, the explanation does not completely deny the possibility that the content will be outside the above range. That is, the appropriate range described above is a particularly preferable range in obtaining the effects of the present invention, and the content may slightly deviate from the above ranges as long as the effects of the present invention are obtained.

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st Embodiment of this invention. FIG. 2 is an enlarged cross-sectional view illustrating a part of the secondary battery illustrated in FIG. 1. It is a disassembled perspective view showing the structure of the secondary battery which concerns on the 2nd Embodiment of this invention. It is sectional drawing showing the structure along the IV-IV line of the secondary battery 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 (10)

A positive electrode including a positive electrode active material capable of occluding and releasing lithium ions, a negative electrode including a negative electrode active material capable of occluding and releasing lithium ions, and an electrolyte including a solvent and an electrolyte salt,
The negative electrode active material includes a negative electrode material that absorbs and releases lithium ions at a potential of 1.0 V or more with respect to a lithium potential,
The solvent includes a carbonic acid ester having two or more halogens as constituent elements. The negative electrode material includes a composite oxide having lithium (Li) and titanium (Ti) as constituent elements, a composite oxide having hydrogen (H) and titanium as constituent elements, titanium oxide (TiO ₂ ), and niobium oxide (Nb). _The secondary battery according to claim 1, which is at least one of ₂ O ₅ ).   The secondary battery according to claim 1, wherein the negative electrode material is a compound having titanium as a constituent element.   The secondary battery according to claim 3, wherein the compound has oxygen (O) as a constituent element. The secondary battery according to claim 1, wherein the negative electrode material is lithium titanate (Li ₄ Ti ₅ O ₁₂ ).   The secondary battery according to claim 1, wherein the carbonate ester is a cyclic carbonate ester.   The secondary battery according to claim 1, wherein the halogen is fluorine (F).   The secondary battery according to claim 1, wherein the number of halogens is two.   The secondary battery according to claim 1, wherein the carbonate ester is 4,5-difluoro-1,3-dioxolan-2-one.   The secondary battery according to claim 1, wherein a content of the carbonate ester in the solvent is 0.01 wt% or more and 10 wt% or less.

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