JP2009093843A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery capable of restraining swelling at initial charging. <P>SOLUTION: Of the nonaqueous electrolyte secondary battery provided with nonaqueous electrolyte together with a positive electrode and a negative electrode, the nonaqueous electrolyte contains a complex of β-diketone represented by formula (1) and a metal element of fifth to twelfth groups of the periodic table, and halogenated carbonate ester or carbonate ester having carbon-carbon multiple bonds. In the formula, R<SB>1</SB>is a fluorine atom, an alkyl group with the carbon number of 4 or less, or a fluoroalkyl group with the carbon number of 4 or less, and R<SB>2</SB>is a fluorine atom, an alkyl group with the carbon number of 4 or less, a phenyl group, a 2-furyl group, or a 2-thio phenyl group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte composition that can suppress expansion during initial charging.

  In recent years, many portable electronic devices such as a camera-integrated VTR, a digital still camera, a mobile phone, a personal digital assistant, and a notebook computer have appeared, and their size and weight have been reduced. As portable power sources for these electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Among them, a lithium ion secondary battery that uses carbon as a negative electrode active material, a lithium-transition metal composite oxide as a positive electrode active material, and a carbonate ester mixture as an electrolyte is a lead battery that is a conventional non-aqueous electrolyte secondary battery, Since a large energy density can be obtained compared to a nickel cadmium battery, it is widely put into practical use. In particular, a laminated battery using an aluminum laminated film for the exterior has a high energy density because it is lightweight. In the laminate battery, since the deformation of the laminate battery can be suppressed by swelling the electrolyte in the polymer, the laminate polymer battery is also widely used.

  In these lithium ion secondary batteries, in order to improve battery characteristics such as cycle characteristics, for example, it has been proposed to add various additives to the electrolytic solution (for example, Patent Documents 1 and 2).

JP 2005-38722 A JP 2006-172726 A

  However, since the laminate battery has a soft exterior, there is a problem that it easily expands during the first charge. This is considered to be caused by the fact that the solvent in the electrolytic solution is decomposed by reacting with the electrode to generate gas. Since the outer shape of the battery is designed on the assumption of expansion at the time of initial charge, if the expansion amount is large, it is necessary to reduce the thickness before charging, and as a result, the discharge capacity of the battery decreases.

  Therefore, the present invention has been made in view of such a problem, and an object of the present invention is to provide a secondary battery capable of suppressing expansion at the time of initial charge.

In this invention, it discovered that the expansion | swelling at the time of an initial charge could be suppressed by containing a specific (beta) -diketone metal complex and carbonate in electrolyte solution.
That is, the present invention provides the following non-aqueous electrolyte secondary battery and non-aqueous electrolyte composition.
[1] A nonaqueous electrolyte secondary battery comprising a nonaqueous electrolyte together with a positive electrode and a negative electrode,
The non-aqueous electrolyte comprises a complex of a β-diketone represented by the following formula (1) and a metal element of Group 5 to Group 12 of the periodic table, and a halogenated carbonate or a carbon-carbon multiple bond. A non-aqueous electrolyte secondary battery comprising an ester.

[In Formula (1), R ₁ is a fluorine atom, an alkyl group having 4 or less carbon atoms, or a fluoroalkyl group having 4 or less carbon atoms. R ₂ is a fluorine atom, an alkyl group having 4 or less carbon atoms, a fluoroalkyl group having 4 or less carbon atoms, a phenyl group, a 2-furyl group, or a 2-thiophenyl group.
[2] Contains a complex of a β-diketone represented by the above formula (1) and a metal element of Group 5 to Group 12 of the periodic table, and a halogenated carbonate or a carbonate having a carbon-carbon multiple bond A non-aqueous electrolyte composition characterized by the above.

  According to the secondary battery of the present invention, the compound represented by the formula (1), that is, a metal complex of β-diketone and a halogenated carbonate or a carbonate having a carbon-carbon multiple bond is added to the electrolytic solution. The expansion at the first charge can be suppressed. Since the β-diketone metal complex generates metal at the negative electrode to reduce resistance, it is considered that overvoltage is reduced at the negative electrode and the decomposition of the solvent can be suppressed. Further, it is considered that halogenated carbonates or carbonates having carbon-carbon multiple bonds suppress gas generation by forming a protective film on the electrode by another mechanism.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following mode.

  FIG. 1 schematically shows a configuration of a secondary battery according to an embodiment of the present invention. This secondary battery is a so-called laminate film type, and has a wound electrode body 20 to which a positive electrode lead 21 and a negative electrode lead 22 are attached accommodated in a film-shaped exterior member 30.

  The positive electrode lead 21 and the negative electrode lead 22 are led out from the inside of the exterior member 30 to the outside, for example, in the same direction. The positive electrode lead 21 and the negative electrode lead 22 are made of, for example, a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 30 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. The exterior member 30 is disposed, for example, so that the polyethylene film side and the wound electrode body 20 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive. An adhesion film 31 is inserted between the exterior member 30 and the positive electrode lead 21 and the negative electrode lead 22 to prevent intrusion of outside air. The adhesion film 31 is made of a material having adhesion to the positive electrode lead 21 and the negative electrode lead 22, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 30 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. 2 shows a cross-sectional structure taken along line II of the spirally wound electrode body 20 shown in FIG. The wound electrode body 20 is obtained by laminating a positive electrode 23 and a negative electrode 24 via a separator 25 and an electrolyte layer 26 and winding them, and the outermost periphery is protected by a protective tape 27.

(Active material layer)
The positive electrode 23 has a structure in which a positive electrode active material layer 23B is provided on both surfaces of a positive electrode current collector 23A. The negative electrode 24 has a structure in which a negative electrode active material layer 24B is provided on both surfaces of a negative electrode current collector 24A, and the negative electrode active material layer 24B and the positive electrode active material layer 23B are arranged to face each other. In the non-aqueous electrolyte secondary battery of the present invention, the thickness of each of the positive electrode active material layer 23B and the negative electrode active material layer 24B per side is 40 μm or more, preferably 80 μm or less. More preferably, it is the range of 40 micrometers or more and 60 micrometers or less. By setting the thickness of the active material layer to 40 μm or more, it is possible to increase the capacity of the battery. Moreover, the discharge capacity maintenance factor when charging / discharging is repeated can be enlarged by setting it as 80 micrometers or less.

(Positive electrode)
The positive electrode current collector 23A is made of, for example, a metal material such as aluminum, nickel, or stainless steel. The positive electrode active material layer 24B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium as a positive electrode active material, and a conductive agent such as a carbon material and polyvinylidene fluoride as necessary. It may contain a binder.

Examples of the positive electrode material capable of inserting and extracting lithium include lithium cobaltate, lithium nickelate, and solid solutions thereof (Li (NiCo _y Mn _z ) O ₂ )) (x, y, and z have values of 0 <x <1, 0 <y <1, 0 ≦ z <1, x + y + z = 1.), Manganese spinel (LiMn ₂ O ₄ ) and its solid solution (Li (Mn _2−v Ni _v ) O ₄ ) (The value of v is v <2.) Lithium composite oxides and the like, and phosphate compounds having an olivine structure such as lithium iron phosphate (LiFePO ₄ ) are preferable. This is because a high energy density can be obtained. Examples of positive electrode materials capable of inserting and extracting lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as iron disulfide, titanium disulfide and molybdenum sulfide, sulfur, And conductive polymers such as polyaniline and polythiophene.

(Negative electrode)
The negative electrode 24 has, for example, a structure in which a negative electrode active material layer 24B is provided on both surfaces of a negative electrode current collector 24A having a pair of opposed surfaces. The negative electrode current collector 24A is made of a metal material such as copper, nickel, and stainless steel, for example.

  The negative electrode active material layer 24B includes one or more negative electrode materials capable of occluding and releasing lithium as a negative electrode active material. In this secondary battery, the charge capacity of the negative electrode material capable of inserting and extracting lithium is larger than the charge capacity of the positive electrode 23 so that lithium metal does not deposit on the negative electrode 24 during the charge. It has become.

  Examples of the negative electrode material capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, and fired organic polymer compounds And carbon materials such as carbon fiber or activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body refers to a carbonized material obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature, and in part, it is made of non-graphitizable carbon or graphitizable carbon. Some are classified. Examples of the polymer material include polyacetylene and polypyrrole. These carbon materials are preferable because the change in the crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent characteristics can be obtained. Furthermore, a battery having a low charge / discharge potential, specifically, a battery having a charge / discharge potential close to that of lithium metal is preferable because a high energy density of the battery can be easily realized.

  Further, as the negative electrode material, in addition to the carbon material shown above, a material containing an element that forms an alloy with lithium, such as silicon, tin, and a compound thereof, magnesium, aluminum, germanium, or the like may be used. Further, a material containing an element that forms a composite oxide with lithium, such as titanium, can be considered.

(Separator)
The separator 25 separates the positive electrode 23 and the negative electrode 24 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 25 is made of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a multi-hard film made of ceramic, and a plurality of these porous films are laminated. It may be a structure. For example, the separator 25 is impregnated with an electrolytic solution that is a liquid electrolyte.

(Electrolyte)

  The electrolyte solution and electrolyte composition in the non-aqueous electrolyte secondary battery of the present invention are a complex of a β-diketone represented by the following formula (1) and a metal element of Group 5 to Group 12 of the periodic table (hereinafter referred to as “a”). , Also referred to as a β-diketone metal complex). Since the β-diketone metal complex generates metal at the negative electrode to reduce resistance, it is considered that overvoltage is reduced at the negative electrode and the decomposition of the solvent can be suppressed. As a result, gas generation is less likely to occur, and expansion during the initial charge can be suppressed.

In Formula (1), R ₁ is a fluorine atom, an alkyl group having 4 or less carbon atoms, or a fluoroalkyl group having 4 or less carbon atoms. That is, R ₁ = C _m H _{2m + 1−n} F _n (0 ≦ m ≦ 4, 0 ≦ n ≦ 2m + 1).
R ₂ is a fluorine atom, an alkyl group having 4 or less carbon atoms, a fluoroalkyl group having 4 or less carbon atoms, a phenyl group, a 2-furyl group, or a 2-thiophenyl group. That is, β-diketone is any of the compounds represented by the following formulas (1-1) to (1-4). In the formula (1-1), 0 ≦ p ≦ 4 and 0 ≦ q ≦ 2p + 1.

R ₁ is preferably a methyl group from the viewpoint of solubility. R ₂ is preferably a methyl group from the viewpoint of solubility. Moreover, as a metal element which forms a complex, nickel is preferable from a viewpoint of the ease of metal production | generation among a periodic table group 5-12 group metal element. These may be used alone or in combination of two or more.

  Specific examples of the β-diketone metal complex include zinc (II) acetylacetonate, copper (II) acetylacetonate, nickel (II) acetylacetonate [formula (1-5)], cobalt (II) acetyl Acetonate, cobalt (III) acetylacetonate, iron (II) acetylacetonate, iron (III) acetylacetonate, manganese (II) acetylacetonate, manganese (III) acetylacetonate, chromium (III) acetylacetonate , Vanadium (III) acetylacetonate, nickel (II) hexafluoroacetylacetonate [formula (1-6)], nickel (II) bis (2,2,6,6-tetramethyl-3,5-heptanedionate) [Formula (1-7)] and the like. Among these, nickel (II) acetylacetonate is preferable. This is because R1 is a methyl group and contains nickel.

  The content of the β-diketone metal complex in the electrolytic solution is preferably 0.03 to 0.3% by weight, more preferably 0.05 to 0.2% by weight, based on the electrolytic solution. If it is in the said range, since it is formation of a low resistance film | membrane, it is preferable.

  The electrolyte solution and the electrolyte composition in the nonaqueous electrolyte secondary battery of the present invention further contain a halogenated carbonate ester or a carbonate ester having a carbon-carbon multiple bond. The combined use of the β-diketone metal complex and these carbonates enhances the effect of suppressing the expansion of the battery. These carbonate esters are thought to suppress gas generation by forming a protective film on the electrode. In addition, these carbonate ester may be used individually by 1 type, and may mix and use multiple types.

  Examples of the halogenated carbonate include 4-fluoro-1,3-dioxolan-2-one (fluoroethylene carbonate) [Formula (2)], 4-chloro-1,3-dioxolan-2-one (chloroethylene carbonate) [Formula (3)], trifluoropropylene carbonate [Formula (4)] and the like. Among these, 4-fluoro-1,3-dioxolan-2-one is preferable from the viewpoint of stability.

  Examples of the carbonic acid ester having a carbon-carbon multiple bond include vinylene carbonate and vinyl ethylene carbonate. Among these, vinylene carbonate is preferable from the viewpoint of reactivity.

  The content of the carbonate ester in the electrolytic solution is preferably 0.3 to 3% by weight, more preferably 0.5 to 2% by weight, based on the electrolytic solution. If it is in the said range, since it is formation of a low resistance film | membrane, it is preferable.

  The electrolytic solution (electrolytic solution composition) in the present invention further contains a solvent and an electrolyte salt dissolved in the solvent.

(solvent)
The solvent used for the electrolytic solution is preferably a high dielectric constant solvent having a relative dielectric constant of 30 or more. This is because the number of lithium ions can be increased. The content of the high dielectric constant solvent in the electrolytic solution is preferably in the range of 15 to 50% by mass. It is because higher charging / discharging efficiency is obtained by setting it within this range.

  Examples of the high dielectric constant solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, lactones such as γ-butyrolactone and γ-valerolactone, lactams such as N-methyl-2-pyrrolidone, and N-methyl- Examples thereof include cyclic carbamates such as 2-oxazolidinone and sulfone compounds such as tetramethylene sulfone. A cyclic carbonate is particularly preferable. Moreover, the said high dielectric constant solvent may be used individually by 1 type, and may mix and use multiple types.

  The solvent used for the electrolytic solution is preferably used by mixing a low-viscosity solvent having a viscosity of 1 mPa · s or less with the high dielectric constant solvent. This is because high ion conductivity can be obtained. The ratio (mass ratio) of the low-viscosity solvent to the high-dielectric-constant solvent is preferably in the range of high-dielectric-constant solvent: low-viscosity solvent = 2: 8 to 5: 5. It is because a higher effect can be obtained by setting it within this range.

  Examples of the low viscosity solvent include chain carbonate esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and trimethyl. Chain carboxylic acid esters such as methyl acetate and ethyl trimethylacetate, chain amides such as N, N-dimethylacetamide, chain carbamic acid esters such as methyl N, N-diethylcarbamate and ethyl N, N-diethylcarbamate And ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran and 1,3-dioxolane. These low-viscosity solvents may be used alone or in combination of two or more.

(Electrolyte salt)
As the electrolyte salt, e.g., lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ , Inorganic lithium salts such as lithium perchlorate (LiClO ₄ ) and lithium tetrachloroaluminate (LiAlCl ₄ ), and lithium trifluoromethanesulfonate (CF ₃ SO ₃ Li), lithium bis (trifluoromethanesulfone) imide [(CF ₃ SO ₂ ) ₂ NLi], lithium bis (pentafluoroethanesulfone) imide [(C ₂ F ₅ SO ₂ ) ₂ NLi] and lithium tris (trifluoromethanesulfone) methide [(CF ₃ SO ₂ ) ₃ CLi] Of perfluoroalkanesulfonic acid derivatives Lithium salts. One electrolyte salt may be used alone, or a plurality of electrolyte salts may be mixed and used.

(Polymer compound)
The battery of the present invention may be in the form of a gel by containing a polymer compound that swells with the electrolyte and serves as a holding body that holds the electrolyte. It is because high ion conductivity can be obtained by including a polymer compound that swells with the electrolytic solution, excellent charge / discharge efficiency can be obtained, and battery leakage can be prevented. When a polymer compound is added to the electrolytic solution and used, the content of the polymer compound in the electrolytic solution is preferably in the range of 0.1% by mass to 2.0% by mass. When a polymer compound such as polyfucavinylidene is applied on both sides of the separator, the mass ratio of the electrolytic solution to the polymer compound is preferably in the range of 50: 1 to 10: 1. It is because higher charging / discharging efficiency is obtained by setting it within this range.

  Examples of the polymer compound include ether-based polymer compounds such as polyvinyl formal represented by the following formula (5), polyethylene oxide and a crosslinked product containing polyethylene oxide, and ester-based polymers such as polymethacrylate represented by the following formula (6). Polymers of vinylidene fluoride such as molecular compounds, acrylate polymer compounds, polyvinylidene fluoride represented by the following formula (7), and a copolymer of vinylidene fluoride and hexafluoropropylene are exemplified. A high molecular compound may be used individually by 1 type, and multiple types may be mixed and used for it. In particular, it is desirable to use a fluorine-based polymer compound such as polyvinylidene fluoride from the viewpoint of the effect of preventing swelling during high temperature storage.

In the above formulas (5) to (7), s, t and u are each an integer of 100 to 10000, R is C _x H _{2x + 1} O _y , (x is 1 to 8, y is x-1 or less). Indicated.

(Production method)
For example, the secondary battery can be manufactured as follows.

  The positive electrode can be produced, for example, by the following method. First, 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 positive electrode mixture. A slurry is obtained. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 23A and the solvent is dried. Then, the positive electrode active material layer 23B is formed by compression molding using a roll press or the like, and the positive electrode 23 is manufactured. At this time, the thickness of the positive electrode active material layer 23B is set to 40 μm or more.

  Moreover, a negative electrode can be produced by the following method, for example. First, after preparing a negative electrode mixture by mixing a negative electrode active material containing at least one of silicon and tin as constituent elements, a conductive agent, and a binder, the negative electrode mixture was mixed with N-methyl-2. -Disperse in a solvent such as pyrrolidone to obtain a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 24A, dried, and compression-molded to form a negative electrode active material layer 24B containing negative electrode active material particles made of the negative electrode active material described above. Get. At this time, the thickness of the negative electrode active material layer 24B is set to 40 μm or more.

  Next, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 23 and the negative electrode 24, and the mixed solvent is volatilized to form the electrolyte layer 26. Next, the positive electrode lead 21 is attached to the positive electrode current collector 23A, and the negative electrode lead 22 is attached to the negative electrode current collector 24A. Subsequently, the positive electrode 23 and the negative electrode 24 on which the electrolyte layer 26 is formed are laminated through a separator 25 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and the protective tape 27 is attached to the outermost peripheral portion. The wound electrode body 20 is formed by bonding. After that, for example, the wound electrode body 20 is sandwiched between the exterior members 30, and the outer edge portions of the exterior members 30 are in close contact with each other by thermal fusion or the like and sealed. At that time, an adhesion film 31 is inserted between the positive electrode lead 21 and the negative electrode lead 22 and the exterior member 30. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 23 and the negative electrode 24 are prepared as described above, and after the positive electrode lead 21 and the negative electrode lead 22 are attached to the positive electrode 23 and the negative electrode 24, the positive electrode 23 and the negative electrode 24 are stacked and wound via the separator 25. Rotate and adhere the protective tape 27 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 20. Next, the wound body is sandwiched between the exterior members 30, and the outer peripheral edge except for one side is heat-sealed to form a bag shape, and is stored inside the exterior member 30. Subsequently, an electrolyte composition containing 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 30 is prepared. After the injection, the opening of the exterior member 30 is heat-sealed and sealed. After that, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 26 and assembling the secondary battery shown in FIGS.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 23 and inserted in the negative electrode 24 through the electrolytic solution. On the other hand, when discharging is performed, for example, lithium ions are extracted from the negative electrode 24 and inserted into the positive electrode 24 through the electrolytic solution.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the embodiment, and various modifications can be made. For example, in the above embodiment and the case where an electrolytic solution is used as the electrolyte, and the case where a gel electrolyte in which the electrolytic solution is held in a polymer compound is also described, other electrolytes are used. It may be. Other electrolytes include, for example, a mixture of an ion conductive inorganic compound such as ion conductive ceramics, ion conductive glass or ionic crystal and an electrolyte, or a mixture of another inorganic compound and an electrolyte. Or a mixture of these inorganic compounds and a gel electrolyte.

  In the above embodiment, a battery using lithium as an electrode reactant has been described. However, another alkali metal such as sodium (Na) or potassium (K), or an alkaline earth metal such as magnesium or calcium (Ca). The present invention can also be applied to the case of using other light metals such as aluminum.

  Further, in the above embodiment, the capacity of the negative electrode is a so-called lithium ion secondary battery represented by a capacity component due to insertion and extraction of lithium, or lithium metal is used for the negative electrode active material, and the capacity of the negative electrode is Although a so-called lithium metal secondary battery represented by a capacity component due to precipitation and dissolution has been described, the present invention makes the charge capacity of the negative electrode material capable of occluding and releasing lithium smaller than the charge capacity of the positive electrode. Thus, the present invention can be similarly applied to a secondary battery in which the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof. .

  Furthermore, in the above embodiment, the laminate type secondary battery has been specifically described, but it goes without saying that the present invention is not limited to the above shape. That is, the present invention can be applied to a cylindrical battery, a square battery, and the like. Further, the present invention is not limited to the secondary battery, and can be similarly applied to other batteries such as a primary battery.

<Examples 1-1 to 1-16>
(Example 1-1)
First, 94 parts by weight of lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 3 parts by weight of graphite as a conductive material, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder are homogeneous. After mixing, N-methylpyrrolidone was added to obtain a positive electrode mixture coating solution. Next, the obtained positive electrode mixture coating liquid was uniformly applied on both surfaces of a 20 μm thick aluminum foil and dried to form a positive electrode mixture layer of 20 mg / cm ² per side. This was cut into a shape having a width of 50 mm and a length of 300 mm to produce a positive electrode.
Next, 97 parts by weight of graphite as a negative electrode active material and 3 parts by weight of PVdF as a binder were homogeneously mixed, and N-methylpyrrolidone was added to obtain a negative electrode mixture coating solution. Next, the obtained negative electrode mixture coating solution was uniformly applied on both sides of a 15 μm thick copper foil serving as a negative electrode current collector and dried to form a negative electrode mixture layer of 10 mg / cm ² per side. This was cut into a shape having a width of 50 mm and a length of 300 mm to prepare a negative electrode.
The electrolytic solution was ethylene carbonate / ethyl methyl carbonate / fluoroethylene carbonate (FEC) / lithium hexafluorophosphate / nickel (II) acetylacetonate = 34/51/1 / 13.9 / 0.1 (mass ratio) ). Nickel (II) acetylacetonate was obtained from Sigma-Aldrich Japan (the same applies to other β-diketone metal complexes).
The positive electrode and the negative electrode were laminated and wound up via a separator made of a microporous polyethylene film having a thickness of 9 μm, and placed in a bag made of an aluminum laminate film. After injecting 2 g of the electrolyte into the bag, the bag was heat-sealed to produce a laminate type battery. The capacity of this battery was 700 mAh.

  Table 1 shows the change in battery thickness when the battery was charged at 700 mA in a 23 ° C. environment and 4.2 V as the upper limit for 3 hours as an expansion coefficient (%). The expansion coefficient is a value calculated using the battery thickness before charging as the denominator and the thickness increased after charging as the numerator.

(Examples 1-2 and 1-3)
The laminate type was the same as in Example 1-1 except that the concentration of nickel (II) acetylacetonate was 0.02% by mass and 0.5% by mass, respectively, and the amount of lithium hexafluorophosphate was increased or decreased accordingly. A battery was created. Table 1 shows the expansion rate (%) before and after charging.

(Example 1-4)
A laminate type battery was prepared in the same manner as in Example 1-1 except that vinylene carbonate (VC) was used instead of fluoroethylene carbonate (FEC). Table 1 shows the expansion rate (%) before and after charging.

(Examples 1-5 to 1-16)
A laminate type battery was prepared in the same manner as in Example 1-1 except that the type of β-diketone metal complex was as shown in Table 1. Table 1 shows the expansion rate (%) before and after charging.

(Comparative Example 1-1)
A laminate type battery was prepared in the same manner as in Example 1-1 except that the β-diketone metal complex and fluoroethylene carbonate were not mixed and the amount of ethylene carbonate was increased accordingly. Table 1 shows the expansion rate (%) before and after charging.

(Comparative Example 1-2)
A laminate type battery was prepared in the same manner as in Example 1-1 except that fluoroethylene carbonate was not mixed and the amount of ethylene carbonate was increased accordingly. Table 1 shows the expansion rate (%) before and after charging.

(Comparative Example 1-3)
A laminated battery was prepared in the same manner as in Example 1-1 except that the β-diketone metal complex was not mixed and the amount of lithium hexafluorophosphate was increased accordingly. Table 1 shows the expansion rate (%) before and after charging.

(Comparative Example 1-4)
A laminate type battery was prepared in the same manner as in Example 1-4, except that the β-diketone metal complex was not mixed and the amount of lithium hexafluorophosphate was increased accordingly. Table 1 shows the expansion rate (%) before and after charging.

  As shown in Table 1, Example 1-1 containing nickel (II) acetylacetonate as a β-diketone metal complex and fluoroethylene carbonate as a halogen carbonate in the electrolytic solution is a comparative example containing none. Compared with 1-1, the expansion coefficient of the battery was significantly reduced. Moreover, the expansion coefficient was further reduced as compared with Comparative Examples 1-2 and 1-3 containing only one of nickel (II) acetylacetonate and fluoroethylene carbonate. From this, it was found that by using the β-diketone metal complex and the halogenated carbonate in combination, the expansion rate at the first charge is efficiently reduced.

  In the case of Example 1-4 containing vinylene carbonate as a carbonic acid ester having a carbon-carbon multiple bond instead of fluoroethylene carbonate, a comparison containing only one of nickel (II) acetylacetonate and vinylene carbonate The expansion rate was further reduced as compared with Examples 1-2 and 1-4. From this, it was found that the expansion rate at the first charge can be efficiently reduced by using a β-diketone metal complex and a carbonic acid ester having a carbon-carbon multiple bond in combination.

  The expansion rates of Examples 1-2 and 1-3 in which the content of nickel (II) acetylacetonate was increased or decreased as compared with Example 1-1 slightly increased. From this, it turned out that preferable content of (beta) -diketone metal complex is 0.02-0.5 mass% in electrolyte solution.

  In Examples 1-5 to 1-16 using a β-diketone metal complex other than nickel (II) acetylacetonate and fluoroethylene carbonate, as in Example 1-1, etc., battery expansion during the initial charge was performed. It has been found that the rate can be reduced efficiently.

<Examples 2-1 to 2-16>
(Example 2-1)
A laminate type battery was produced in the same manner as in Example 1-1, except that a separator having a thickness of 7 μm and a separator coated with 2 μm of polyvinylidene fluoride on both sides was used. At this time, the mass ratio of the electrolytic solution to polyvinylidene fluoride was 20: 1. Table 2 shows the change in the battery thickness when the battery was charged at 700 mA in a 23 ° C. environment and 4.2 V as the upper limit for 3 hours as an expansion rate (%).

(Example 2-2, 2-3)
The laminate type was the same as in Example 2-1, except that the concentration of nickel (II) acetylacetonate was 0.02% by mass and 0.5% by mass, respectively, and the amount of lithium hexafluorophosphate was increased or decreased accordingly. A battery was created. Table 2 shows the expansion rate (%) before and after charging.

(Example 2-4)
A laminate type battery was prepared in the same manner as in Example 2-1, except that vinylene carbonate (VC) was used instead of fluoroethylene carbonate (FEC). Table 1 shows the expansion rate (%) before and after charging.

(Examples 2-5 to 2-16)
A laminate type battery was prepared in the same manner as in Example 2-1, except that the type of β-diketone metal complex was as shown in Table 2. Table 2 shows the expansion rate (%) before and after charging.

(Comparative Example 2-1)
A laminate type battery was prepared in the same manner as in Example 2-1, except that the β-diketone metal complex and fluoroethylene carbonate were not mixed and the amount of ethylene carbonate was increased accordingly. Table 1 shows the expansion rate (%) before and after charging.

(Comparative Example 2-2)
A laminate type battery was prepared in the same manner as in Example 2-1, except that fluoroethylene carbonate was not mixed and the amount of ethylene carbonate was increased accordingly. Table 2 shows the expansion rate (%) before and after charging.

(Comparative Example 2-3)
A laminate type battery was prepared in the same manner as in Example 2-1, except that the β-diketone metal complex was not mixed and the amount of lithium hexafluorophosphate was increased accordingly. Table 2 shows the expansion rate (%) before and after charging.

(Comparative Example 2-4)
A laminate type battery was prepared in the same manner as in Example 2-4 except that the β-diketone metal complex was not mixed and the amount of lithium hexafluorophosphate was increased accordingly. Table 2 shows the expansion rate (%) before and after charging.

As shown in Table 2, Example 2-1 containing nickel (II) acetylacetonate as the β-diketone metal complex and fluoroethylene carbonate as the halogen carbonate in the electrolytic solution was a comparative example containing none. Compared to 2-1, the expansion rate of the battery was significantly reduced. Moreover, the expansion coefficient was further reduced as compared with Comparative Examples 2-2 and 2-3 containing only one of nickel (II) acetylacetonate and fluoroethylene carbonate. From this, it was found that by using the β-diketone metal complex and the halogenated carbonate in combination, the expansion rate at the first charge is efficiently reduced.
In addition, Example 2-1 containing polyvinylidene fluoride further improved the effect of reducing the expansion coefficient compared to Example 1-1 not containing polyvinylidene fluoride. From this, it was found that the effect of reducing the expansion of the battery can be further improved by using polyvinylidene fluoride as the polymer compound in addition to containing the β-diketone metal complex and the halogenated carbonate in the electrolytic solution.

In the case of Example 2-4 containing vinylene carbonate as a carbonic acid ester having a carbon-carbon multiple bond instead of fluoroethylene carbonate, a comparison containing only one of nickel (II) acetylacetonate and vinylene carbonate The expansion rate was further reduced as compared with Examples 2-2 and 2-4. From this, it was found that the expansion rate at the first charge can be efficiently reduced by using a β-diketone metal complex and a carbonic acid ester having a carbon-carbon multiple bond in combination.
Moreover, Example 2-4 containing polyvinylidene fluoride further improved the reduction effect of an expansion coefficient compared with Example 1-4 which does not contain. From this, in addition to containing a β-diketone metal complex and a carbonic acid ester having a carbon-carbon multiple bond in the electrolytic solution, the effect of reducing the expansion of the battery can be further improved by using polyvinylidene fluoride as the polymer compound. I understood.

  The expansion rates of Examples 2-2 and 2-3 in which the content of nickel (II) acetylacetonate was increased or decreased from that of Example 2-1 slightly increased. From this, it turned out that preferable content of (beta) -diketone metal complex is 0.02-0.5 mass% in electrolyte solution.

  In Examples 2-5 to 2-16 using a β-diketone metal complex other than nickel (II) acetylacetonate and fluoroethylene carbonate, as in Example 2-1, etc., the battery expanded during the initial charge. It has been found that the rate can be reduced efficiently.

  While the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified.

It is a disassembled perspective view showing the structure of the nonaqueous electrolyte secondary battery which concerns on one 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 20 ... Winding electrode body, 23 ... Positive electrode, 23A ... Positive electrode collector, 23B ... Positive electrode active material layer, 24 ... Negative electrode, 24A ... Negative electrode collector, 24B ... Negative electrode active material layer, 25 ... Separator, 21 ... Positive electrode Lead, 22 ... negative electrode lead, 26 ... electrolyte layer, 27 ... protective tape, 30 ... exterior member, 31 ... adhesion film.

Claims (9)

A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte together with a positive electrode and a negative electrode,
The non-aqueous electrolyte comprises a complex of a β-diketone represented by the following formula (1) and a metal element of Group 5 to Group 12 of the periodic table, and a halogenated carbonate or a carbon-carbon multiple bond. A non-aqueous electrolyte secondary battery comprising an ester.

[In Formula (1), R ₁ is a fluorine atom, an alkyl group having 4 or less carbon atoms, or a fluoroalkyl group having 4 or less carbon atoms. R ₂ is a fluorine atom, an alkyl group having 4 or less carbon atoms, a fluoroalkyl group having 4 or less carbon atoms, a phenyl group, a 2-furyl group, or a 2-thiophenyl group. ]   The non-aqueous electrolyte secondary battery according to claim 1, wherein the β-diketone is acetylacetone.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the metal element is nickel.   The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous electrolyte secondary battery is housed in an exterior member made of a laminate film.   The nonaqueous electrolyte secondary battery according to claim 1, comprising a polymer compound that swells with the nonaqueous electrolyte.   The non-aqueous electrolyte secondary battery according to claim 5, wherein the polymer compound is polyvinylidene fluoride. It contains a complex of β-diketone represented by the following formula (1) and a metal element of Group 5 to Group 12 of the periodic table, and a halogenated carbonate or a carbonate having a carbon-carbon multiple bond. A non-aqueous electrolyte composition.

[In Formula (1), R ₁ is a fluorine atom, an alkyl group having 4 or less carbon atoms, or a fluoroalkyl group having 4 or less carbon atoms. R ₂ is a fluorine atom, an alkyl group having 4 or less carbon atoms, a fluoroalkyl group having 4 or less carbon atoms, a phenyl group, a 2-furyl group, or a 2-thiophenyl group.   The non-aqueous electrolyte composition according to claim 7, wherein the β-diketone is acetylacetone. The non-aqueous electrolyte composition according to claim 7, wherein the metal element is nickel.

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